Ethylene polymers having high density

Abstract

The present invention relates to an ethylene polymer comprising moieties according to Formula (IB): wherein R is a moiety comprising 1 and 10 carbon atoms; wherein R.sup.1 and R.sup.2 are each individually hydrogen or a moiety comprising 1 and 5 carbon atoms, R.sup.1 and R.sup.2 may be the same or different; wherein the ethylene polymer has a molecular weight distribution of 3.0 and 40.0; the ethylene polymer has a melting temperature of 115 C.; the ethylene polymer has a density 935 and 960 kg/m3; the ethylene polymer is essentially free from chromium, hafnium, zirconium and tetrahydrofuran; for the fraction of the ethylene polymer having a molecular weight >100 kg/mol, the intrinsic viscosity of the ethylene polymer is related to the molecular weight according to the inequality: log I.V.<0.65*log M3.10 Such polymers have high density, high purity and good processability, whilst maintaining barrier properties for oxygen and water vapour at a level similar to high-density polyethylenes produced via catalytic processes. ##STR00001##

Claims

1. The ethylene polymer comprising moieties according to Formula IB: ##STR00005## wherein R is a moiety comprising 1 and 10 carbon atoms; wherein R.sup.1 and R.sup.2 are each individually hydrogen or a moiety comprising 1 and 5 carbon atoms, R.sup.1 and R.sup.2 may be the same or different; wherein the ethylene polymer has a molecular weight distribution defined as the ratio between the weight average molecular weight M.sub.w and the number average molecular weight M.sub.n, (M.sub.w/M.sub.n) as determined according to ISO 16014-1 (2012) of 3.0 and 40.0; the ethylene polymer has a melting temperature as determined according to ISO 11357-3 (2011) at a heating rate of 10 K per minute of 115 C.; the ethylene polymer has a density as measured according to ISO 1183-1 (2012), method A of 935 and 960 kg/m.sup.3; the ethylene polymer is essentially free from chromium, hafnium, zirconium and tetrahydrofuran; for the fraction of the ethylene polymer having a molecular weight >100 kg/mol, the intrinsic viscosity of the ethylene polymer is related to the molecular weight according to the inequality:
log I.V.<0.65*log M3.10 wherein I.V. is the intrinsic viscosity, expressed in dl/g, of a fraction of the ethylene polymer having a molecular weight M, the molecular weight M expressed in kg/mol; wherein the molecular weight is determined via Size Exclusion Chromatography (SEC) according to ISO 16014-1 (2012); and wherein the intrinsic viscosity is determined via differential viscometry of the fractions obtained from SEC, in accordance with ASTM D5225 (2014).

2. The ethylene polymer according to claim 1, wherein R is a moiety selected from linear alkanes, branched alkanes, cyclic alkanes, linear alkenes, branched alkenes or cyclic alkenes.

3. The ethylene polymer according to claim 1, wherein R is a moiety selected from C.sub.2H.sub.4, C.sub.3H.sub.6, C.sub.4H.sub.8, C.sub.5H.sub.10, C.sub.6H.sub.12.

4. The ethylene polymer according to claim 1, wherein the ethylene polymer is produced in a polymerisation process at a pressure of 180 MPa and 400 MPa.

5. The ethylene polymer according to claim 1, wherein the ethylene polymer is produced in a tubular reactor.

6. The ethylene polymer according to claim 1, wherein the ethylene polymer is produced by reacting a reaction mixture comprising ethylene and one or more cyclic olefin comonomers.

7. The ethylene polymer according to claim 6, wherein the cyclic olefin comonomer is one or more selected from cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclooctadiene, cyclononene, cyclodecene, 1-methyl cyclohexene, 3-methyl cyclohexene, -pinene, and/or norbornene.

8. The ethylene polymer according to claim 6, wherein the reaction mixture comprises 0.10 and 2.00 mol % of the cyclic olefin comonomer compared to the total molar composition of the reaction mixture.

9. The ethylene polymer according to claim 1, wherein the ethylene polymer comprises 0.05 and 6.00% of moieties according to formula I compared to the total number of recurring moieties in the ethylene copolymer.

10. A polymer composition comprising an ethylene polymer according to claim 1.

11. A film comprising an ethylene polymer according to claim 1.

12. A package for fresh food products comprising a layer comprising an ethylene polymer according to claim 1.

13. The package according to claim 12, wherein said layer comprises 80.0% by weight of the ethylene polymer compared to the total weight of said layer.

14. The package according to claim 12, wherein said layer is present in the form of one or more of a single-layer film, one or more layer(s) of a multi-layer film, and/or an extrusion-coated film.

Description

EXPERIMENT I

Preparation Of Ethylene Polymer

(1) In a high-pressure polymerisation reactor, an ethylene polymer was prepared by reacting a reaction mixture comprising ethylene an amount of comonomer. The comonomer was fed as a 1.45 mol % solution in isopropyl alcohol. The reaction was performed at a pressure of 200 MPa. The reaction temperature was kept between 200 and 230 C. The reaction was initiated by addition of a solution of t-butyl peroxy pivalate in heptane. The obtained ethylene polymer was collected. The examples were prepared using different comonomers and quantities as presented in Table I:

(2) TABLE-US-00001 TABLE I Ethylene Ethylene Ethylene polymer A polymer B polymer C Comonomer cyclohexene cyclooctene cyclooctene Comonomer 0.2 mol % 0.7 mol % 0.2 mol % feed concentration Initiator 0.00153 mol % 0.00179 mol % 0.00250 mol % feed concentration

(3) Wherein the mol % is to be understood to be the fraction in mol % compared to the total quantity of reactive ingredients fed to the reaction. The reactive ingredients in the above examples are ethylene, comonomer and initiator.

EXPERIMENT II

Determination Of Intrinsic Viscosity And Molecular Weight

(4) Ethylene polymer A, B and C according to the invention as obtained in experiment I and for comparative purposes ethylene polymer D, a commercial polyethylene material grade 0863F, obtainable from SABIC, ethylene polymer E, a commercial polyethylene material grade LDPE 1922, and ethylene polymer F, a commercial polyethylene material grade ICP4907S, all obtainable from SABIC, were subjected to Size Exclusion Chromatography (SEC) using a Polymer Laboratories PL-GPC220 high-temperature GPC/SEC system, to obtain fractions of the ethylene polymer having a certain molecular weight. The column set used are three Polymer Laboratories 13 m PLgel Olexis, 3007.5 mm. The calibration for the molar mass was performed with a linear polyethylene as standard. The molecular weight was determined according to ISO 16014-1 (2012).

(5) The intrinsic viscosity of these fractions was subsequently determined using a Polymer Laboratories BV-400 viscometer. Refractive index detector: Polymer Char IR5 infrared detector. The intrinsic viscosity was determined in accordance with ASTM D5225 (2014).

(6) Results are presented in Table II.

(7) TABLE-US-00002 TABLE II Intrinsic viscosity (dl/g) Molecular Ethylene polymer weight (kg/mol) A B C D E F 10 0.292 0.292 0.288 0.348 0.341 0.371 50 0.809 0.800 0.742 1.055 0.803 1.085 100 1.174 1.138 1.033 1.820 1.127 1.846 200 1.585 1.482 1.298 3.020 1.471 3.007 300 1.904 1.731 1.489 4.064 1.686 4.014 400 2.133 1.914 1.589 5.023 1.845 4.908 500 2.540 2.136 1.692 5.840 1.982 5.741 600 2.833 2.405 1.777 6.194 2.090 6.472

EXPERIMENT III

Determination of Material Properties

(8) Material properties of the sample ethylene polymers A-F were determined. The results are presented in Table III.

(9) TABLE-US-00003 TABLE III Ethylene polymer Property (Unit) Method A B C D E F Melting ISO 11357-3 115 116 118 134 112 131 temperature ( C.) (2011) heating rate 10 K. Density (kg/m.sup.3) ISO 1183-1 936 938 940 964 926 949 (2012), method A Transparency (%) ASTM D1746 92 90 86 (2015) Water vapour ISO 15106-3 0.9 1.1 1.1 4.0 1.8 2.3 transmission rate (2003) (g/(m.sup.2*24 h)) Oxygen ISO 15105-2 1335 1474 2135 1000 6389 1339 transmission rate (2003), method (cm.sup.3/(m.sup.2*bar*24 h)) A Molecular Weight ISO 16014-1 3.7 4.4 9.9 5.3 21.7 Distribution () (2012)

(10) ISO 16014-1 (2012) relates to determination of average molecular mass and molecular mass distribution using size-exclusion chromatography.

(11) ISO 11357-3 (2011) relates to determination of temperature and enthalpy of melting and crystallisation via differential scanning calorimetry.

(12) ISO 1183-1 (2012) relates to determination of density of non-cellular plastics.

(13) ISO 15106-3 (2003) relates to determination of water vapour transmission rate of film and sheeting.

(14) ISO 15105-2 (2003) relates to determination of gas transmission rate of film and sheeting.

(15) ASTM D-5225 (2014) relates to a standard test method for measuring solution viscosity of polymers with a differential viscometer.

(16) ASTM D6474 (2012) relates to a standard test method for determining molecular weight distribution and molecular weight averages of polyolefins by high temperature gel permeation chromatography.

(17) ASTM D1746 (2015) relates to a standard test method for transparency of plastic sheeting.

(18) From the results obtained in experiments II and III, it becomes apparent that ethylene polymers according to the present invention having a high density, high purity and good processability, whilst maintaining barrier properties for oxygen and water vapour at a level similar to high-density polyethylenes produced via catalytic processes.