Free-flowing, easily soluble granules based on high-temperature thermoplastics with a low content of volatile organic compounds.

Description

[0001] The present invention relates to readily soluble and free-flowing granules based on high-temperature thermoplastics with a low content of volatile organic compounds, as well as processes for their preparation and use.

[0002] The production of membranes or coatings typically requires solutions of high-temperature thermoplastics, especially polyethersulfones. Free-flowing high-temperature thermoplastics, which dissolve quickly in the solvents used, are preferred. Compact granules generally dissolve only slowly. Powders or flakes often tend to clump.

[0003] WO 94 / 15999 describes micropowders of polyarylene ether sulfones or ketones with spherical particles and a substantially smooth surface structure, obtainable by spray-drying polyarylene ether sulfone solutions in N-methylpyrrolidone, dimethyl sulfoxide, or dimethylformamide. The micropowders are characterized by a narrow particle size distribution with average particle diameters of 2–70 µm and are particularly suitable for coating metallic surfaces. To reduce the residual solvent content, subsequent drying, for example, in a fluidized bed or moving bed, is generally required.

[0004] US 2012 / 0245239 A1 describes polyetherimide particles or powders with a high surface area and high porosity, which are obtained by precipitation of polymer solutions in hot water or steam. The solubility of the polyetherimide powders in N-methylformamide at 80°C is lower than that of mechanically ground polyetherimides, but still in the range of one hour.

[0005] WO 2019 / 025245 A1 (PCT / EP2018 / 070084) describes expandable, blowing agent-containing granules based on high-temperature thermoplastics and a process for their production. The expandable, blowing agent-containing granules can be foamed into foam particles with a bulk density according to DIN ISO 697:1982 in the range of 10 to 200 kg / m³.

[0006] Residual solvents such as acetone, methyl ethyl ketone, ethanol, isopropanol, N-methylpyrrolidone, dimethylformamide, sulfolane, or dimethyl sulfoxide, which were used in the aforementioned processes for producing high-temperature thermoplastics, generally interfere with further processing into coatings or membranes, such as dialysis membranes. Therefore, the solvents must be removed from the polymer granules, which is a complex process.

[0007] WO 2014 / 033321 describes a solvent-free process for the production of aromatic polyethersulfones by reacting a dichlorodiphenylsulfone component with a bisphenol component in the presence of alkali metal carbonate in the melt in a mixing kneader. This produces solvent-free granules, which, however, dissolve only slowly in solvents such as N-methylpyrrolidone.

[0008] The object of the present invention was therefore to provide easily soluble and free-flowing granules with a low content of volatile organic compounds and processes for their production.

[0009] The task was solved by granules based on high-temperature thermoplastics, selected from the group of polyarylethersulfones, polyaryletherketones, polyphenylene sulfides, polyetherimides, polyphenyleneamides, polycarbonates, aromatic polyester carbonates, high-temperature polyamides (HTPA), thermoplastic polyoxzolidones and copolycarbonates or mixtures thereof, with a bulk density according to DIN ISO 697:1982 in the range of 100 to 650 kg / m 3< and a content of volatile organic compounds of less than 0.1 wt.%.

[0010] Preferred embodiments can be found in the subclaims.

[0011] According to the invention, amorphous thermoplastic polymers with a glass transition temperature T g of at least 165° C, preferably in the range from 180° to 240° C, measured by means of dynamic differential thermal analysis (DSC) according to ISO 11357-2:1999 with a heating rate of 10 K / min, and semi-crystalline thermoplastic polymers with a melt peak temperature T pm according to ISO 11357-3:2011-05-01 of at least 250° C, preferably in the range from 260 to 350° C, are suitable as high-temperature thermoplastics.

[0012] The high-temperature thermoplastics are polyarylethersulfones, polyaryletherketones, polyphenylene sulfides, polyetherimides, polyphenyleneamides, polycarbonates, aromatic polyestercarbonates, high-temperature polyamides (HTPA), thermoplastic polyoxazolidones, and copolycarbonates (PC-HAT) made from BPA and BPTMC. Polysulfones (PSU), polyphenylsulfones (PPSU), and polyethersulfones (PESU) are particularly preferred.

[0013] According to DIN ISO 697:1982, the bulk density of the granules according to the invention is in the range from 100 to 650 kg / m 3 , preferably in the range from 210 to 390 kg / m 3 . At bulk densities below 100 kg / m 3 , the granules may float upon dissolution in the solvent, and at bulk densities above 700 kg, the time required for complete dissolution of the granules increases.

[0014] The granules have a volatile organic compound (VOC) content of less than 0.1 wt.%, preferably less than 0.01 wt.%. Volatile organic compounds are understood to be those with a boiling point between isopentane (28°C) and n-hexadecane (287°C). The total content of acetone, ethanol, isopropanol, N-methylpyrrolidone, dimethylformamide, sulfolane, and dimethyl sulfoxide, based on the granules, is particularly preferably less than 0.1 wt.%. The volatile organic compound (VOC) content can be determined, for example, by headspace GC / MS or as described in DIN ISO 16000-6:2012-11.

[0015] The granules generally have an average mass in the range of 1 to 50 mg, preferably in the range of 3 to 20 mg, and particularly preferably in the range of 3 to 8.5 mg. To determine the average mass, approximately 100 granules are weighed and the mean value for one granule is determined.

[0016] The granules are generally spherical, ellipsoidal, or cylindrical. They are preferably spherical or ellipsoidal and have an L / D ratio (longest dimension (L) to diameter (D) of the granules) in the range of 1 / 1 to 2.5 / 1, preferably in the range of 1 / 1 to 2 / 1. At L / D ratios above 2.5 / 1 or below 1 / 2, the flowability decreases significantly. The L / D ratio can be determined by measuring at least 20 granules and calculating the average value, or preferably by dynamic image analysis (Camsizer), in which the shadow projection of the granules flowing through a hopper is recorded with cameras.

[0017] The granules according to the invention are rapidly soluble in common solvents. Preferably, 2 g of the granules dissolve completely in 100 ml of N-methylpyrrolidone at 80°C in less than 100 minutes, preferably in less than 60 minutes.

[0018] The granules according to the invention are free-flowing. They preferably have a flowability in the range of 1 to 6 seconds, particularly preferably in the range of 2 to 5 seconds, measured according to DIN EN ISO 6186:1998.

[0019] The granules preferably consist of a high-temperature thermoplastic, particularly preferably of a polyarylethersulfone, with a viscosity number in the range of 40 to 100 cm 3 / g, measured according to ISO 307, 1157, 1628 in 0.01 g / ml phenol / 1,2, ortho-dichlorobenzene, 1:1.

[0020] The granules preferably do not contain any solids as additives, in particular no fillers or nucleating agents such as talc.

[0021] The invention also relates to processes for producing the granules according to the invention by extrusion of a melt of the high-temperature thermoplastic containing a blowing agent.

[0022] A preferred process for producing the granules according to the invention described above comprises the following steps: a) producing a polymer melt by melting at least one high-temperature thermoplastic with a volatile organic compound content of less than 0.1% by weight, b) adding a blowing agent to the polymer melt c) optionally conveying the polymer melt via a gear pump d) conveying the blowing agent-containing polymer melt at a temperature in the range from 250° to 350° C through a perforated plate and e) granulating the blowing agent-laden polymer melt.

[0023] Another preferred process for producing the above-described granules according to the invention comprises the steps: a) producing a polymer melt by reacting a dichlorodiphenyl sulfone component with a bisphenol component as monomers in the presence of alkali carbonate in the melt in the absence of solvents or diluents and subsequent separation of salts, b) adding a blowing agent to the polymer melt, c) optionally conveying the polymer melt via a gear pump and a melt filter, d) conveying the blowing agent-containing polymer melt at a temperature in the range of 250° to 350° C through a perforated plate and e) granulating the blowing agent-laden polymer melt.

[0024] In both preferred processes, granulation can be carried out by strand granulation, water ring granulation, or underwater granulation. Preferably, granulation in step e) of the two preferred processes takes place in an underwater granulator operated at a water temperature in the range of 75 to 99°C and a pressure in the range of 1 to 10 bar.

[0025] Nitrogen, carbon dioxide, water, or mixtures thereof are preferably used as blowing agents. The blowing agents or blowing agent mixtures are added in amounts of 1 to 10 wt.%, preferably 2 to 5 wt.%, based on the high-temperature thermoplastics.

[0026] The bulk density of the granules according to the invention can be controlled by the choice of blowing agent and the pressure in the underwater granulator. Low bulk densities are achieved by lower pressures and / or lower amounts of blowing agent.

[0027] The polymers described above for the granules according to the invention can be used as high-temperature thermoplastics. A polyarylene ether sulfone with a viscosity number in the range of 40 to 100 cm³ / g, measured according to ISO 307, 1157, 1628 in 0.01 g / ml phenol / 1,2-ortho-dichlorobenzene, 1:1, is preferred.

[0028] Suitable polyethersulfones with a low residual monomer content can be obtained, for example, by reacting a dichlorodiphenylsulfone component with a bisphenol component as monomers in the presence of alkali metal carbonate in the melt in the absence of solvents or diluents and subsequently separating the salts, as described in WO 2014 / 033321 and WO 2017 / 162485.

[0029] Preferably, no solids are added to the polymer melt as additives, in particular no fillers or nucleating agents such as talc.

[0030] The granules according to the invention can preferably be used for the production of membranes, in particular dialysis membranes, coatings or for the toughening of reactive resins. Examples

[0031] Raw materials used: Ultrason E2010 natural Polyethersulfone granules from BASF SE, density 1370 kg / m 3< , viscosity number 56 cm 3< / g, glass transition temperature DSC (10° C / min) 225 ° C, bulk density 750 g / l. Ultrason E3010 natural Polyethersulfone granules from BASF SE, density 1370 kg / m 3< , viscosity number 66 cm 3< / g, glass transition temperature DSC (10° C / min) 225 ° C) bulk density 750 g / l. Propellant: H2O Measurement methods: Determination of bulk density:

[0032] The bulk density of the blowing agent-free, porous granules was determined according to DIN ISO 697:1982. Determination of solubility

[0033] To determine solubility, 2 g of polyethersulfone was dissolved in 100 ml of N-methylpyrrolidone (NMP) in a beaker at 80°C on a vibrating plate at 150 rpm. The time until the granules completely dissolved was measured. The vibrating plate speed was 150 rpm for 30 minutes and then 300 rpm. Determination of flowability

[0034] The flowability of the granules was determined according to DIN EN ISO 6186:1998, method B and a test funnel with an outlet diameter of 15 mm. Determination of the content of volatile organic compounds (VOC)

[0035] The content of volatile organic compounds (VOCs) was determined using headspace GC / MS as follows. Headspace measurement conditions:

[0036] Sample temperature: 70 °C Tempering time: 60 min Interface temperature: 150 °C Normal pressure: 115 kPa High pressure: 180 kPa Injection time: 0.20 min Cryofocusing: 2.5 / 2.5 min (pre / post) Sample weight: 152 mg sample + 2 ml DMAA Measurement conditions GC / MS Separation capillary: DB-1 30 m 0.25 mm 1 µm Temperature program: 40 °C; 8.5 min; 5 °C / min; 260 °C; 10 min Pre-pressure: 70 kPa Split: approx. 20 ml / min Scan: 25 - 400 amu

[0037] For quantitative determination, acetone and isopropanol were used as reference. Determination of the L / D ratio:

[0038] The L / D ratio was determined by dynamic image analysis (Camsizer), in which the shadow projection of the granules flowing through a hopper was recorded with cameras. The L / D parameter was determined from the Camsizer size b / l 3 , b / l 3 =xc,min / xFe,max, where xc,min is the shortest chord in the projection plane and xFe,max is the maximum Feret diameter in the projection plane. L / D = l 3 / b. Examples B-1 - B-6: Production of porous granules from polyethersulfones

[0039] The porous granules were produced in an apparatus consisting of a twin-screw extruder from Leistritz divided into eight zones 35 (Z1···Z8) with 18 mm

[0040] screw diameter and a length to diameter ratio of 40, a melt pump (gear pump ZRP), start-up valve (AV), melt filter, perforated plate (LP) and an underwater pelletizer (UWG).

[0041] Polyethersulfone (PESU) was metered into the twin-screw extruder and melted. After approximately two-thirds of the extruder's length, the blowing agent, H2O, was injected into the extruder using Isco pumps (piston pumps from Axel Semrau) and an injector built into the extruder. Using the melt pump (ZRP), the pressure profile in the extruder was adjusted (pressure-speed control) so that the blowing agent was completely mixed into the polymer melt. In addition to adjusting the pressure profile in the twin-screw extruder, the melt pump also serves to convey the blowing agent-impregnated polymer melt through the downstream equipment (the start-up valve, the melt screen, and the perforated plate). The melt strand emerging through the perforated plate (1 hole with 1.0 mm diameter) was expanded under counterpressure in the underwater granulator (UWG) and cut into polyethersulfone granules with a granule weight in the range of 3 - 10 mg.The total throughput of the extruder was kept constant at 4.6 kg / h. The strand in the water box was cut by six knives attached to the knife ring. The knife ring rotates at 3600 rpm. This process produces porous granules, which are transported by the water circuit from the perforated plate into the dryer, from where they are separated into a collecting container.

[0042] The weight proportions of the raw materials used are listed in Table 1. The water content refers to the amount added per 100 parts by weight of polymer. The process parameters are listed in Table 2. Comparative tests:

[0043] Comparative experiment V1 was carried out like examples B-1 to B-6 with the process parameters given in Table 1. Table 1: Process parameters Insurance No. Throughput Ultrason 2010 Ultrason 3010 Water Extruder temp Water temperature UWG Water pressure UWG Granule mass g / h Shares g / h Shares g / h Shares g / h ° C ° C [bear] mg B-1 4603 100 4500,39 2,28 102,61 340 90 5 3,3 B-2 4603 100 4500,39 2,28 102,61 340 90 5 5,7 B-3 4603 100 4500,39 2,28 102,61 340 90 2,5 6,3 B-4 4603 100 4468,93 3,00 134,07 340 90 5 6,4 B-5 4603 100 4468,93 3,00 134,07 340 90 3 6,0 B-6 4603 100 4425,96 4,00 177,04 340 90 3 8,3 V-1 4603 100 4383,81 5,00 219,19 340 90 3 9,3 Table 2: Properties Insurance No. product Bulk density dry Particle mass Solubility in NMP VOC Flowability L / D g / l mg [min] [%] [sec] B-1 Ultrason E 2010 296 3,3 47 < 0,01 1,1 B-2 Ultrason E 3010 289 5,7 24 < 0,01 3,07 1,2 B-3 Ultrason E 3010 271 6,3 29 < 0,01 4,07 1,2 B-4 Ultrason E 3010 269 6,4 16 < 0,01 3,17 1,5 B-5 Ultrason E 3010 271 6,0 29,0 < 0,01 3,2 1,6 B-6 Ultrason E 3010 182 8,3 29 < 0,01 4,13 1,8 V-1 Ultrason E 3010 92 9,3 13 < 0,01 Not free-flowing 2,7

Claims

1. A granulate based on high-temperature thermoplastics, selected from the group of polyaryl ether sulfones, polyaryl ether ketones, polyphenylene sulfides, polyetherimides, polyphenyleneamides, polycarbonates, aromatic polyester carbonates, high-temperature polyamides (HTPA), thermoplastic polyoxazolidones and copolycarbonates or mixtures thereof, with a bulk density in the range of 100 to 650 kg / m3 in accordance with DIN ISO 697:1982 and less than 0.1% by weight content of volatile organic compounds.

2. The granulate according to claim 1, wherein said granulate has a less than 0.01% by weight content of volatile organic compounds.

3. The granulate according to claim 1 or 2, wherein the mass per pellet of said granulate is in the range of 3 to 8.5 mg.

4. The granulate according to any one of claims 1 to 3, wherein the L / D ratio of said granulate is in the range of 1 / 1 to 2.5 / 1.

5. The granulate according to any of claims 1 to 4, wherein 2 g of said granulate dissolves in 100 ml of N-methylpyrrolidone at 80°C in less than 60 minutes.

6. The granulate according to any of claims 1 to 5, wherein the flowability value of said granulate is in the range of 1 to 6 seconds, measured in accordance with DIN EN ISO 6186:1998.

7. The granulate according to any of claims 1 to 6, wherein said granulate consists of a high-temperature thermoplastic with an intrinsic viscosity in the range of 40 to 100 cm3 / g, measured in accordance with DIN EN ISO 1628-1:2012-10 in 0.01 g / ml phenol / 1.2, ortho-dichlorobenzene, 1:1.

8. The granulate according to any of claims 1 to 7, wherein said granulate has a bulk density in the range of 210 to 390 kg / m3 in accordance with DIN ISO 697:1982.

9. A method for the production of granulates based on high-temperature thermoplastics according to any of claims 1 to 8, comprising the stages of: a) production of a polymer melt via melting of at least one high-temperature thermoplastic with less than 0.1% by weight content of volatile organic compounds, b) addition of a blowing agent to the polymer melt c) optionally conveying of the polymer melt by way of a gear pump d) conveying of the blowing-agent-containing polymer melt at a temperature in the range of 250°C to 350°C through a pelletizing die and e) granulation of the blowing-agent-loaded polymer melt.

10. A method for the production of granulates based on polyaryl ether sulfones according to claim 8, comprising the stages of: a) production of a polymer melt via reaction of a dichlorodiphenyl sulfone component with a bisphenol component as monomers in the presence of alkali metal carbonate in the melt in the absence of solvents or diluents, followed by removal of salts, b) addition of a blowing agent to the polymer melt, c) optionally conveying of the polymer melt by way of a gear pump d) conveying of the blowing-agent-containing polymer melt at a temperature in the range of 250°C to 350°C through a pelletizing die and e) granulation of the blowing-agent-loaded polymer melt.

11. The method according to claim 9 or 10, wherein the granulation in stage e) takes place in an underwater pelletizer operated at a water temperature in the range of 75 to 99°C and at a pressure in the range of 1 to 10 bar.

12. The method according to claim 9 or 10, wherein nitrogen, carbon dioxide, water or mixtures thereof are used as blowing agent.

13. The method according to any of claims 9 to 12, wherein a polyarylene ether sulfone with an intrinsic viscosity in the range of 40 to 100 cm3 / g, measured in accordance with DIN EN ISO 1628-1:2012-10 in 0.01 g / ml phenol / 1.2, ortho-dichlorobenzene, 1:1 is used as high-temperature thermoplastic.

14. The use of the granulates according to claims 1 to 8 for the production of membranes or coatings, or for the toughness-modification of reactive resins.