Short-Chain Polyethylene Homopolymers Having Improved Grindability

Abstract

A polyethylene homopolymer having improved grindability, prepared with a metallocene catalyst system and is characterized by a melt viscosity of 5 to <60 mPa.Math.s at 140 C. and a ram penetration hardness ranging from 210 to 500 bar, as measured according to DGF M-III 9e, and to use thereof as a component in toners, hot-melt adhesives or pigment master batches.

Claims

1. A polyethylene homopolymer, prepared with a metallocene catalyst system and having a melt viscosity as measured to DIN 53019 in the range from 5 to <60 mPa.Math.s at 140 C. and by a ram penetration hardness as measured to DGF M-III 9e of 210 to 500 bar.

2. The polyethylene homopolymer as claimed in claim 1, having a dropping point of 113 to 128 C., a melting point of 100 to 123 C., a density of 0.93 to 0.97 g/cm.sup.3 at 25 C., a heat of fusion of 210 to 270 J/g.

3. The polyethylene homopolymer as claimed in claim 1, having an average particle size d.sub.50 of 15 m.

4. The polyethylene homopolymer as claimed in claim 1, having an oxygen-containing group content and an acid number resulting therefrom in the range from 0.5 to 100 mg KOH/g.

5. A micronized wax having an average particle size d.sub.50 of 15 m, comprising a polyethylene homopolymer having a melt viscosity of 5 to <60 mPa.Math.s at 140 C.

6. An additive component for printing inks comprising a polyethylene homopolymer as claimed in claim 1.

7. An additive component for coating materials comprising a polyethylene homopolymer as claimed in claim 1.

8. A component of hotmelt adhesives comprising a polyethylene homopolymer as claimed in claim 1.

9. A component of photographic toners comprising a polyethylene homopolymer as claimed in claim 1.

10. A component of pigment masterbatches comprising a polyethylene homopolymer as claimed in claim 1.

11. An additive component for printing inks comprising a micronized wax as claimed in claim 5.

12. An additive component for coating materials comprising a micronized wax as claimed in claim 5.

13. A component of hotmelt adhesives comprising a micronized wax as claimed in claim 5.

14. A component of photographic toners comprising a micronized wax as claimed in claim 5.

15. A component of pigment masterbatches comprising a micronized wax as claimed in claim 5.

Description

EXAMPLES

Preparation of Polyethylene Waxes

Example 2 (not Inventive)

[0099] For the preparation of the catalyst, 6 mg of bis(indenyl)zirconium dichloride were dissolved in 20 cm.sup.3 of toluenic methylaluminoxane solution (corresponding to 27 mmol of Al) and reacted with the methylaluminoxane by being left to stand for 15 minutes. In parallel with this, a dry 16 dm.sup.3 vessel flushed with nitrogen was filled with 4 kg of propane and brought to a temperature of 70 C. At this temperature, 0.15 bar of hydrogen and 30 cm.sup.3 of the toluenic methylaluminoxane solution were added via a pressure lock and the mixture was stirred at 100 rpm. The pressure was topped up with ethylene to a total pressure of 31 bar, and the polymerization was initiated at 250 rpm by addition of the catalyst via the pressure lock. The polymerization temperature was regulated at 70 C. by cooling, and the total pressure was kept constant by further addition of ethylene. After a polymerization time of 1 hour, the reaction was stopped by addition of isopropanol and the reactor was let down and opened. The physical properties of the polyethylene wax obtained are reported in tab. 1.

Examples 3, 4 and 9 (not Inventive) and Examples 5-8 (Inventive)

[0100] Preparation took place in a manner similar to that indicated for example 2. The melt viscosity was adjusted by gradually increasing the hydrogen concentration.

[0101] The inventive polyethylenes from examples 5-8 were ground on an AFG 100 fluidized-bed opposed-jet mill from Hosokawa Alpine. The classifier speed was 8000 revolutions per minute (rpm) and the grinding pressure was 6.0 bar. The parameter used for grindability was the throughput, measured in grams/h. The particle size determination was determined by means of a Mastersizer 2000 from Malvern; measuring range 0.02-2000 m by laser diffraction. The samples were prepared with a Hydro 2000 S wet dispersing unit from Malvern.

[0102] For comparison, the noninventive polyethylenes from examples 2-4 and 9 were ground under analogous conditions.

[0103] As further noninventive comparatives, the waxy polyethylenes GW 115.92.HV and GW 105.95.LV from GreenMantra, produced by thermal degradation of LLDPE and HDPE, respectively, and also a LICOWAX PE 130 HDPE produced by Ziegler-Natta polymerization, from Clariant, and the two Fischer-Tropsch paraffins SASOLWAX C80 and SASOLWAX H1 from Sasol were ground and tested for throughput.

[0104] The physical data for the waxes are listed in table 1. The micronization results are contrasted in table 2. They show that with the polyethylenes from examples 5-8 it was possible to obtain micronized waxes with a particle size d.sub.50 of at least comparable fineness, but with significantly higher throughput.

TABLE-US-00001 TABLE 1 Physical properties of the example waxes used: Ram Viscosity Dropping Melting Heat of penetration @ 140 C. point point fusion hardness Density Example Designation mPas C. C. J/g bar g/cm.sup.3 1 comp. Licowax PE 130 350 129 127 229 611 0.97 2 comp. metallocene-PE wax 350 130 127 264 550 0.97 3 comp. metallocene-PE wax 100 128 125 254 481 0.97 4 comp. metallocene-PE wax 60 128 123 268 470 0.97 5 inven. metallocene-PE wax 30 125 121 250 456 0.97 6 inven. metallocene-PE wax 14 122 116 248 409 0.96 7 inven. metallocene-PE wax 9 116 112 237 366 0.95 8 inven. metallocene-PE wax 8 115 111 225 346 0.95 9 comp. metallocene-PE wax 4 113 98 223 221 0.93 10 comp. Sasolwax C80 4 88 82 222 268 0.92 11 comp. Sasolwax H1 9 111 108 233 478 0.94 12 comp. GW 115.92.HV 482 115 111 150 0.92 13 comp. GW 105.95.LV 38 106 108 132 0.95

TABLE-US-00002 TABLE 2 Grinding results Wax Through- corresponding put d.sub.50 to Tab. 1: g/h m Remarks Example 1 1000 8.3 trouble-free grinding Example 2 1100 8.7 trouble-free grinding Example 3 1200 9.1 trouble-free grinding Example 4 1280 9.1 trouble-free grinding Example 5 (inv.) 1511 8.3 trouble-free grinding Example 6 (inv.) 1900 8.3 trouble-free grinding Example 7 (inv.) 1920 8.5 trouble-free grinding Example 8 (inv.) 1580 8.7 trouble-free grinding Example 9 950 9.3 caking in grinding chamber Example 10 950 8.9 trouble-free grinding Example 11 1240 8.5 trouble-free grinding Example 12 190 14.4 severe caking in grinding chamber Example 13 110 14.7 severe caking in grinding chamber

Examples 14-16 (Use in Printing Ink Formulations)

[0105] The inventive micronized wax from example 7 was dispersed into the respective printing ink system and performance-tested in different printing technologies:

Example 14: Flexographic Printing

[0106] The micronized wax was dispersed with a fraction of 0.5% and 0.8% into an aqueous flexographic ink, with intensive stirring using a dissolver, and was tested to standard. Used as comparative examples were two micronized waxes typical for the application, the product Spray 30 from Sasol (Fischer-Tropsch paraffin, d.sub.50=6 m) and Ceridust 3610 from Clariant (micronized polyethylene wax, d.sub.50=5.5 m).

[0107] For the production of the ink, mixtures were prepared of Flexonyl Blue A B2G (Clariant) and distilled water (5:1; mixture A) and also from Viacryl SC 175 W, 40 WAIP (Cytec Ind.) and distilled water (1:1; mixture B). Then 70 parts of mixture B were stirred slowly into 30 parts of mixture A and the resulting mixture was homogenized at a stirring speed of 1200 rpm for 30 minutes. 0.5 or 0.8 wt %, respectively, of micronized wax was incorporated into the ink. The flexographic ink was applied to absorbent flexopaper with a film-drawing apparatus (Control Coater), using a wire doctor (LWC 60 g/m.sup.2; 6 m wet film thickness).

[0108] After a drying time of 24 hours, measurements were made of scuff protection, gloss, and sliding friction.

[0109] For the determination of the scuff resistance, the print was first of all scuffed (Prfbau Quartant scuff tester, scuffing load 48 g/cm.sup.2, scuffing speed 15 cm/s). Measurements were made of the intensity of the ink transferred to the test sheet (color difference E to DIN 6174, measurement with Hunterlab D 25-2, Hunter).

[0110] The coefficient of sliding friction was determined using a Friction Peel Tester 225-1 (Thwing-Albert Instruments).

[0111] The gloss was determined using a micro-TRI-gloss- gloss meter (BYK Gardner GmbH). The results set out in table 3 below show that the inventive wax is in no way inferior to the comparative examples in terms of color difference, and hence abrasion resistance, and also gloss and sliding friction.

TABLE-US-00003 TABLE 3 Aqueous flexographic printing on Algro Finess paper 80 g/m.sup.2 Gloss Sliding Sample 20 60 friction E no wax 5 38 0.44 4.01 0.5% Spray 30 5 37 0.16 2.32 0.8% Spray 30 5 34 0.15 1.96 0.5% Ceridust 3610 5 36 0.19 2.83 0.8% Ceridust 3610 5 34 0.18 2.80 0.5% micronized 5 37 0.17 2.78 polyethylene from example 7 0.8% micronized 5 35 0.17 2.77 polyethylene from example 7

Example 15: Gravure Ink

[0112] The micronized wax was dispersed into gravure ink with a fraction of 1%, with intensive stirring using a dissolver, and was tested to standard. Used as comparative examples were two micronized waxes typical for the application, the product Spray 30 from Sasol (d.sub.50=6 m) and Ceridust 3610 from Clariant (d.sub.50=5.5 m).

[0113] The ink employed was an illustration gravure ink RR Grav Red, toluene-based (Siegwerk Druckfarben AG); for the sample prints on gravure paper (Algro Finess 80 g/m.sup.2), an LTG 20 gravure machine from Einlehner Prfmaschinenbau was used.

[0114] Measurements were made of scuff resistance, coefficient of sliding friction, and gloss. The results set out in table 4 below show that the inventive wax is in no way inferior to the comparative examples with regard to color difference and hence abrasion resistance and also gloss and sliding friction.

TABLE-US-00004 TABLE 4 Gravure printing Gloss Sliding Sample 20 60 friction E Gravure ink - no wax, halftone 13 62 0.61 14.8 Gravure ink - no wax, 26 80 0.59 13.3 masstone Gravure ink - Ceridust 3610, 10 51 0.19 3.4 halftone Gravure ink - Ceridust 3610, 18 63 0.19 3.3 masstone Gravure ink - micronized 9 51 0.18 3.4 polyethylene from example 7, halftone Gravure ink - micronized 18 64 0.16 3.5 polyethylene from example 7, masstone Gravure ink - Spray 30, 9 49 0.16 3.2 halftone Gravure ink - Spray 30, 17 60 0.16 3.5 masstone

Example 16: Offset Ink

[0115] The micronized wax was dispersed into offset ink (Novaboard cyan 4 C 86, K+E Druckfarben) with a fraction of 1.5% and 3%, with intensive stirring using a dissolver, and was tested to standard. Used as comparative examples were two micronized waxes typical for the application, the product Spray 30 from Sasol (d.sub.50=6 m) and Ceridust 3610 from Clariant (d.sub.50=5.5 m).

[0116] A sample print (Prfbau-Mehrzweck-Probedruckmaschine System Dr. Dner) was made on paper of type Phoenomatt 115 g/m.sup.2 (Scheufelen GmbH+Co KG) and investigation was made of the scuff behavior on a scuff tester (Prfbau Quartant scuff tester) for a scuffing load of 48 g/cm.sup.2 and a scuffing speed of 15 cm/sec. Assessment was made of the intensity of the ink transferred to the test sheet (color difference to DIN 6174, measurement with Hunterlab D 25-2, Hunter). The results set out in table 5 below show that the inventive wax is in no way inferior to the comparative examples in terms of color difference and therefore abrasion resistance, and also gloss and sliding friction.

TABLE-US-00005 TABLE 5 Offset printing on paper Gloss Sliding Sample 20 60 friction E no wax 8 46 0.61 10.08 1.5% Spray 30 8 48 0.44 5.24 3.0% Spray 30 7 45 0.35 2.26 1.5% Ceridust 3610 9 52 0.49 4.07 3.0% Ceridust 3610 9 49 0.37 2.80 1.5% micronized 10 53 0.40 3.73 polyethylene from example 7 3.0% micronized 9 50 0.31 2.64 polyethylene from example 7