Polyethylene with controlled wax content, chlorinated polyethylene thereof and molded article produced from the chlorinated polyethylene

Abstract

Disclosed are polyethylene, chlorinated polyethylene thereof and a molded article produced from the chlorinated polyethylene. More specifically, disclosed are polyethylene for preparation of chlorinated polyethylene, the polyethylene having a molecular weight distribution (MWD) of 5 or less, a melting index (5.0 kg) of 0.1 to 10 dg/min, a weight average molecular weight of 50,000 to 300,000 g/mol, a melting temperature of 125 to 135° C., a wax content of 0.0001 to 3% by weight or 0.01 to 0.3% by weight and a density of 0.94 g/cm.sup.3 or more, chlorinated polyethylene thereof and a molded article produced from the chlorinated polyethylene.

Claims

1. Polyethylene for preparation of chlorinated polyethylene, the polyethylene having a molecular weight distribution (MWD) of 5 or less, a melting index (5.0 kg) of 0.1 to 10 dg/min, a weight average molecular weight of 50,000 to 300,000 g/mol, a melting temperature of 125 to 140° C., a density of 0.94 g/cm.sup.3 or more and a wax content of 0.01 to 0.3% by weight.

2. The polyethylene according to claim 1, wherein the polyethylene has a low molecular weight (≦5,000 g/mol) content of 0.01 to 5% by weight.

3. The polyethylene according to claim 1, wherein the molecular weight distribution (MWD) is 2.1 to 3.4.

4. The polyethylene according to claim 1, wherein the melting index (5.0 kg) is 0.3 to 7 dg/min.

5. The polyethylene according to claim 1, wherein the melting temperature is 125 to 135° C.

6. The polyethylene according to claim 1, wherein the density is 0.945 to 0.955 g/cm.sup.3.

7. The polyethylene according to claim 1, wherein the polyethylene has a wax content of 0.05 to 0.2% by weight.

8. The polyethylene according to claim 1, wherein the polyethylene has an average particle size of 30 to 400 μm.

9. The polyethylene according to claim 1, wherein the polyethylene is prepared in the presence of a metallocene catalyst.

10. Chlorinated polyethylene prepared by reacting the polyethylene according to claim 1 with chlorine.

11. The chlorinated polyethylene according to claim 10, wherein the chlorinated polyethylene has a chlorine content of 20 to 45% by weight.

12. The chlorinated polyethylene according to claim 10, wherein the chlorinated polyethylene has a Mooney viscosity of 70 to 110.

13. The chlorinated polyethylene according to claim 10, wherein the chlorinated polyethylene has a volume resistance of 10.sup.13 to 10.sup.17 Ωcm and thermal stability of 150 to 180° C.

14. An extrusion-molded article produced from the chlorinated polyethylene according to claim 10.

15. The extrusion-molded article according to claim 14, wherein the extrusion-molded article is cross-linked using a peroxide cross-linking agent.

16. The extrusion-molded article according to claim 15, wherein the extrusion-molded article has a volume resistance of 1×10.sup.14 Ωcm to 200×10.sup.14 Ωcm.

17. The extrusion-molded article according to claim 14, wherein the extrusion-molded article is a wire cable or a hose.

18. A method for preparing chlorinated polyethylene comprising: dispersing 100 parts by weight of the polyethylene according to claim 1, 0.1 to 0.2 parts by weight of an emulsifier, and 1 to 5 parts by weight of a dispersant in water; and reacting the resulting dispersion with 80 to 200 parts by weight of chlorine in the presence of 0.01 to 1.0 parts by weight of a catalyst.

19. A method for producing an extrusion-molded article comprising: a) roll-mill compounding the chlorinated polyethylene according to claim 10 with a cross-linking agent; b) extruding the compounded chlorinated polyethylene; c) allowing the extrudate to stand at 100 to 180° C. for 3 to 60 minutes; and d) cross-linking (curing) the extrudate.

Description

EXAMPLE

Example 1

(1) <High-Density Polyethylene>

(2) 13 kg/hr of ethylene and 0.1 g/hr of hydrogen were continuously reacted in a hexane slurry state using Metallocene K1 and K2 catalysts produced by LG Chem., Ltd. in a 220 L reactor of a pilot plant at a reactor temperature of 82° C. for 2 hours, followed by dehydration and drying, to prepare a High-density polyethylene powder. The prepared High-density polyethylene was present in a powder form and MI, density, wax content or the like thereof are shown in the following Table 1.

(3) <Preparation of Chlorinated Polyethylene>

(4) 5,000 L of water and 550 kg of High-density polyethylene were added to a reactor, sodium polymethacrylate as a dispersant, oxypropylene and oxyethylene copolyether as emulsifiers, and benzoyl peroxide as a catalyst were added to the reactor and chlorination was performed with gas-phase chlorine at a final temperature of 132° C. for 3 hours.

(5) The chlorination product was neutralized with NaOH or Na.sub.2CO.sub.3 for 4 hours, washed with running water for 4 hours and finally dried at 120° C. to prepare powdery chlorinated polyethylene.

(6) <Roll-Mill Compounding>

(7) 100 parts by weight of the prepared chlorinated polyethylene, 28 parts by weight of trioctyl trimellitate (TOTM), 80 parts by weight of talc, 60 parts by weight of CaCO.sub.3, 2 parts by weight of a calcium zinc stabilizer, 8 parts by weight of MgO, 0.4 parts by weight of St-A (stearic acid), 2.8 parts by weight of dicumyl peroxide and 4 parts by weight of TAIC 70% were compounded using a roll-mill at 133° C. for 2 minutes.

(8) <Production of Sheet Without Cross-Linking (Curing)>

(9) The compounding product was pressed in a hot press at 150° C. and 60 bar to produce a sheet.

(10) <Production of Sheet Using Cross-Linking (Curing)>

(11) The sheet (before cross-linking) was treated (cured) in an oven at 165° C. for 10 minutes to produce a cross-linked (cured) sheet.

Example 2

(12) Chlorinated polyethylene and PVC composition samples were prepared in the same manner as in Example 1 except that 0.4 g/hr of hydrogen was added in the preparation of High-density polyethylene.

Comparative Example 1

(13) Chlorinated polyethylene and PVC composition samples were prepared in the same manner as in Example 1 except that CE2080Z produced by LG Chem., Ltd. having properties shown in the following Table 1 was used as High-density polyethylene.

Test Example

(14) Physical properties of the sheet and cross-linked (cured) sheet produced in Examples 1 and 2 and Comparative Example 1 were measured and results are shown in the following Table 1. Melting index (dg/min): measured under the conditions of 190° C. and 5 kg in accordance with ASTM D-1238. Weight average molecular weight (g/mol): measured by gel permeation chromatography. The device used herein was PL-GPC 220 (Agilent, Polymer Laboratories). 0.2% by weight of HDPE and 125 ppm of BHT were dissolved in trichlorobenzene (TCB) at 165° C. for 2 hours to produce a sample and the sample was analyzed by passing through three Mixed-B Columns and one Mixed-B Guard Column produced by Agilent (Polymer Laboratories). Molecular weight distribution: obtained as a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) measured by gel permeation chromatography. Low molecular weight content (wt %): obtained by calculating a content of a molecular weight of 5,000 g/mol or less in molecular weights measured by gel permeation chromatography. Melting temperature: measured at a temperature increase rate of 10° C./min using DSC. Average particle size: nine sieves (63˜850 μm) in total were mounted on a particle size analyzer Taylor-type Auto shaker and a particle size corresponding to 50% of the total weight of the sample was calculated. Density: measured in accordance with ASTM D-792. Wax content: a low molecular weight ingredient was extracted from 10 g of polyethylene with 150 ml of n-heptane at 98° C. for 3 hours and a content (by weight) of a solid after extraction with respect to a standard substance was measured. Chlorine content: the sample was baked in an automatic quick furnace at 1,000° C., the produced gas was collected in H.sub.2O and Cl content was analyzed using an ion chromatograph (IC) device. Mooney viscosity (processability): measured at 100° C. for 4 minutes in accordance with ASTM D-1626. Cross-linking properties: scorch time and curing rate and the like were measured at 165° C. in accordance with ASTM D-2084. Tensile strength and elongation: measured in accordance with ASTM D2240 sample size and tensile testing method. The tensile rate was 500 mm/min and the total number of samples used for measurement was 15. Electrical insulation property: volume resistance of a flat cross-linked (cured) sheet (CPE) having a measurement area of 19.625 cm.sup.2 and a sample thickness of 0.2 cm was measured in accordance with ASTM D257.

(15) TABLE-US-00001 TABLE 1 Comparative Properties Example 1 Example 2 Example 1 Poly- MI (5 kg) 2 4 0.5 ethylene Density (g/cm.sup.3) 0.953 0.954 0.956 (PE) Mw (g/mol) 122,000 135,000 220,000 MWD 3 2.5 13 Low molecular 0.3 0.8 5.4 weight content (%) Wax content (wt %) 0.07 0.11 0.35 Average particle 200 130 200 size (μm) Melting temperature 133 133 132 (° C.) Sheet Chlorination (%) 36 36 36 (CPE) Mooney viscosity 95 87 85 Tensile strength 6.5 6.2 8.3 (MPa) Elongation (%) 1,200 1,400 850 Cross- Tensile strength 10.8 10.5 9.2 linked (MPa) sheet Electrical insulation 110 80 5.2 (CPE) property(*10.sup.14Ωcm)

(16) As can be seen from Table 1 above, the polyethylene (Examples 1 and 2) according to the present invention had a wax content controlled to a low level, unlike conventional polyethylene, and thus caused no blocking problem upon chlorination and was sufficiently neutralized and washed, and chlorinated polyethylene prepared therefrom exhibited superior production efficiency, thermal stability and the like.

(17) In addition, the chlorinated polyethylene sheet according to the present invention exhibited superior Mooney viscosity, tensile strength and elongation, and the cross-linked (cured) sheet produced by cross-linking the same exhibited considerably superior tensile strength and electrical insulation property.

(18) In addition, chlorinated polyethylene prepared using polyethylene having a higher molecular weight distribution (MWD) and wax content (Comparative Example 1) exhibited bad Mooney viscosity, elongation, tensile strength after cross-linking and electrical insulation property.

(19) Furthermore, Examples 1 and 2 in which a content of a low molecular weight of 5,000 g/mol or less was 0.01 to 5% by weight exhibited superior Mooney viscosity and elongation and excellent tensile strength after cross-linking and electrical insulation property.