POLYOLEFIN COMPOSITION FOR ENHANCED LASER PRINTING

Abstract

A polyolefin composition for use as an outer layer of a cable is described, wherein the polyolefin composition comprises a multimodal olefin copolymer and carbon black and UV agent; wherein the multimodal olefin copolymer has density of 0.915-0.960 g/cm3, MFR2 of 0.1-10 g/10 min, wherein carbon black in the polyolefin composition is present in an amount of 0.25-1 wt %, and wherein the polyolefin composition has shrinkage of 1% or lower.

Claims

1. A polyolefin composition, wherein said polyolefin composition comprises a multimodal olefin copolymer and carbon black and UV agent; wherein said multimodal olefin copolymer has density of 0.915-0.960 g/cm.sup.3, MFR2 of 0.1-10 g/10 min, wherein carbon black in said polyolefin composition is present in an amount of 0.25-1 wt %, and wherein said polyolefin composition has shrinkage of 1% or lower.

2. The polyolefin composition according to claim 1, wherein said UV agent is present in said polyolefin composition in an amount of 0.1-1 wt %.

3. The polyolefin composition according to claim 1, wherein said UV agent is a mixture of equal amounts of dimethyl succinate polymer with 4-hydroxy-2,2,6,6,-tetramethyl-1-piperidineethanol and poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]).

4. The polyolefin composition according to claim 1, wherein said composition further comprises an antioxidant or an antistatic agent, or both.

5. The polyolefin composition according to claim 4, wherein said antistatic agent is stearate.

6. The polyolefin composition according to claim 4, wherein said antioxidant is a mixture of equal amounts of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and tris(2,4-di-tert-butylphenyl) phosphite.

7. The polyolefin composition according to claim 1, wherein said multimodal olefin copolymer is an ethylene polymer mixture.

8. The polyolefin composition according to claim 1, wherein said multimodal olefin copolymer is a bimodal polymer mixture of a low molecular weight ethylene homo- or copolymer and a high molecular weight copolymer of ethylene and a comonomer selected from the list consisting of 1-butene, 4-methyl-1-pentene, 1-hexene or 1-octene.

9. The composition according to claim 1, wherein the multimodal olefin copolymer mixture is a bimodal polymer mixture of a low molecular weight ethylene homopolymer and a high molecular weight copolymer of ethylene and 1-butene.

10. The polyolefin composition according to claim 1, wherein the amount of carbon black in said polyolefin composition is 0.25-0.75 wt %, preferably 0.25-0.5 wt %.

11. The polyolefin composition according to claim 1, wherein the shrinkage is 0.70% or lower, preferably of 0.60% or lower.

12. A method of inducing print on an outer layer of a cable, wherein said outer layer comprises a polyolefin composition according to claim 1, and said print is induced by laser radiation.

13. The method according to claim 12, wherein the frequency of said laser is 20-100 kHz.

14. The method according to claim 12, wherein the power of said laser is 2-50W.

15. An outer layer of a cable, comprising a polyolefin composition according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Embodiments of the invention will now be described by way of examples with reference to the accompanying drawings, of which:

[0087] FIGS. 1-4 show printed samples with a combination of carbon black and UV agent. The amount of carbon black is 0.25 wt % in FIG. 1, 0.5 wt % in FIG. 2, 0.75 wt % in FIGS. 3 and 1 wt % in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0088] 1. Materials

[0089] PE1 is poly(ethylen-co-(1-butene)) copolymer with 39% of carbon black additive

[0090] PE2 is bimodal high density polyethylene. Comparative PE3 is black bimodal high density polyethylene. The properties of PE2 and PE3 are summarized in Table 1.

TABLE-US-00001 TABLE 1 Properties of the base resin PE2 in Samples 1-4 Property PE2 PE3 Analysis method Density (Compound) 944 kg/m.sup.3 954 kg/m.sup.3 ISO 1183 Melt Flow Rate (190° C./2.16 kg) 1.7 g/10 min 1.7 g/10 min ISO 1133 Flexural Modulus 850 MPa 900 MPa ASTM D 790 Tensile Strain at Break (50 mm/min) 900% 900% ISO 527  Tensile Strength (50 mm/min) 31 MPa 29 MPa ISO 527  Brittleness temperature <−76° C. <−76° C. ASTM D 746 Environmental Stress Crack Resistance >5.000 h >5.000 h IEC 60811-406 (50° C., lgepal 10%, F0) Hardness, Shore D (1 s) 61 61 ISO 868  Pressure Test at High Temperature <10% <10 % IEC 60811-508 (115° C., 6 h)

[0091] The antioxidant is lrganox B225 obtained from BASF.

[0092] The antistatic agent is Ceasit SW (calcium stearate) obtained from Baerlocher. The UV agent is Tinuvin 783 FDL obtained from BASF.

[0093] 2. Methods

[0094] Filler Content

[0095] The amount of carbon black is measured through combustion of the material in a tube furnace in nitrogen atmosphere. The sample is weighted before and after the combustion. The combustion temperature is 550° C. The result is based on one measurement. The method is according to ASTM D1603.

[0096] The amount of CB may also be determined using FT IR spectroscopy as is well known to a person skilled in the art.

[0097] Comonomer Content

[0098] Quantitative nuclear-magnetic resonance (NMR) spectroscopy is used to quantify the comonomer content of the polymers.

[0099] Quantitative 13C{1H} NMR spectra are recorded in the molten-state using a Bruker Advance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for 1H and 13C respectively. All spectra are recorded using a 13C optimized 7 mm magic-angle spinning (MAS) probe-head at 150° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material is packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. This setup is chosen primarily for the high sensitivity needed for rapid identification and accurate quantification (Klimke et al, Macromol. Chem. Phys. 2006; 207:382; Parkinson et al, Macromol. Chem. Phys. 2007; 208:2128; Castignolles et al, M., Polymer 50 (2009) 2373).

[0100] Standard single-pulse excitation is employed utilizing the transient NOE at short recycle delays of 3s (Pollard et al, Macromolecules 2004; 37:813; Klimke et al, Macromol. Chem. Phys. 2006; 207:382) and the RS-HEPT decoupling scheme (Filip et al, J. Mag. Resn.

[0101] 2005, 176, 239; Griffin et al, Mag. Res. in Chem. 2007 45, S1, S198). A total of 1024 (1k) transients are acquired per spectrum. This setup is chosen due its high sensitivity towards low comonomer contents.

[0102] Quantitative 13C{1H} NMR spectra are processed, integrated and quantitative properties determined using custom spectral analysis automation programs. All chemical shifts are internally referenced to the bulk methylene signal (δ+) at 30.00 ppm (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201).

[0103] Characteristic signals corresponding to the incorporation of 1-butene are observed (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201) and all contents calculated with respect to all other monomers present in the polymer.

[0104] Characteristic signals resulting from isolated 1-butene incorporation i.e. EEBEE comonomer sequences, are observed. Isolated 1-butene incorporation is quantified using the integral of the signal at 39.84 ppm assigned to the *B2 sites, accounting for the number of reporting sites per comonomer:

B=I*B2

[0105] When characteristic signals resulting from consecutive 1-butene incorporation i.e. EBBE comonomer sequences are observed, such consecutive 1-butene incorporation is quantified using the integral of the signal at 39.4 ppm assigned to the ααB2B2 sites accounting for the number of reporting sites per comonomer:

BB=2*IααB2B2

[0106] When characteristic signals resulting from non consecutive 1-butene incorporation i.e. EBEBE comonomer sequences are also observed, such non-consecutive 1-butene incorporation is quantified using the integral of the signal at 24.7 ppm assigned to the ßßB2B2 sites accounting for the number of reporting sites per comonomer:

BEB=2*IßßB2B2

[0107] Due to the overlap of the *B2 and *ßB2B2 sites of isolated (EEBEE) and non-consecutively incorporated (EBEBE) 1-butene respectively the total amount of isolated 1-butene incorporation is corrected based on the amount of non-consecutive 1-butene present:

B=I*B2−2*IßßB2B2

[0108] With no other signals indicative of other comonomer sequences, i.e. butene chain initiation, observed the total 1-butene comonomer content is calculated based solely on the amount of isolated (EEBEE), consecutive (EBBE) and non-consecutive (EBEBE) 1-butene comonomer sequences:

Btotal=B+BB+BEB

[0109] Characteristic signals resulting from saturated end-groups are observed. The content of such saturated end-groups is quantified using the average of the integral of the signals at 22.84 and 32.23 ppm assigned to the 2s and 3s sites respectively:

S=(½)*(I2s+I3s)

[0110] The relative content of ethylene is quantified using the integral of the bulk methylene (δ+) signals at 30.00 ppm:

E=(½)*δ+

[0111] The total ethylene comonomer content is calculated based the bulk methylene signals and accounting for ethylene units present in other observed comonomer sequences or end-groups:

Etotal=E+( 5/2)*B+( 7/2)*BB+( 9/2)*BEB+( 3/2)*S

[0112] The total mole fraction of 1-butene in the polymer is then calculated as: fB=Btotal/(Etotal+Btotal)

[0113] The total comonomer incorporation of 1-butene in mole percent is calculated from the mole fraction in the usual manner:

B[mol %]=100*fB

[0114] The total comonomer incorporation of 1-butene in weight percent is calculated from the mole fraction in the standard manner:

B[wt %]=100*(fB*56.11)/((fB*56.11)+((1−fB)*28.05))

[0115] Mw, Mn

[0116] Molecular weight averages (Mw and Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI=Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) are determined by Gel Permeation Chromatography (GPC) according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12 using the following formulas:

[0117] For a constant elution volume interval ΔVi, where Ai, and Mi are the chromatographic peak slice area and polyolefin molecular weight (MW), respectively associated with the elution volume, Vi, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

[0118] A high temperature GPC instrument, equipped with either infrared (IR) detector (IR4 or IR5 from PolymerChar (Valencia, Spain) or differential refractometer (RI) from Agilent Technologies, equipped with 3×Agilent-Plgel Olexis and 1× Agilent-Plgel Olexis Guard columns is used. As the solvent and mobile phase 1,2,4-trichlorobenzene (TCB) stabilized with 250 mg/L 2,6-Di tert butyl-4-methyl-phenol) is used. The chromatographic system is operated at 160° C. and at a constant flow rate of 1 ml/min. 200 μL of sample solution is injected per analysis. Data collection is performed using either Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0119] The column set is calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/mol. The PS standards are dissolved at room temperature over several hours. The conversion of the polystyrene peak molecular weight to polyolefin molecular weights is accomplished by using the Mark Houwink equation and the following Mark Houwink constants:

[00001]$K_{PS}=19*10^{-3}\frac{mL}{g}{\propto }_{\mathrm{PS}}=0.655K_{PE}=39*10^{-3}\frac{mL}{g}{\propto }_{\mathrm{PE}}=0.725K_{PP}=19*10^{-3}\frac{mL}{g}{\propto }_{\mathrm{PP}}=0.725$

[0120] A third order polynomial fit is used to fit the calibration data.

[0121] All samples are prepared in the concentration range of 0,5−1 mg/ml and dissolved at 160° C. for 2.5 hours for PP or 3 hours for PE under continuous gentle shaking.

[0122] As it is known in the art, the weight average molecular weight of a blend can be calculated if the molecular weights of its components are known according to:

[00002]$M{w}_b=\underset{i}{.Math.}{w}_i.Math.{\mathrm{Mw}}_i$

[0123] where Mwb is the weight average molecular weight of the blend, wi is the weight fraction of component “i” in the blend and Mwi is the weight average molecular weight of the component “i”.

[0124] The number average molecular weight can be calculated using the mixing rule:

[00003]$\frac{1}{{\mathrm{Mn}}_b}=\underset{i}{.Math.}\frac{w_i}{{\mathrm{Mn}}_i}$

[0125] where Mnb is the number average molecular weight of the blend, wi is the weight fraction of component “i” in the blend and Mni is the number average molecular weight of the component “i”.

[0126] Cable Extrusion

[0127] The cable extrusion is done on a Nokia-Maillefer cable line. The extruder has five temperature zones with temperatures of 1701175118011901190° C. and the extruder head has three zones with temperatures of 210/210/210° C. The extruder screw is a barrier screw of the design Elise. The die is a semi-tube on type with 5.9 mm diameter and the outer diameter of the cable is 5 mm. The compound is extruded on a 3 mm in diameter, solid aluminum conductor to investigate the extrusion properties. Line speed is 75 m/min.

[0128] The pressure at the screen and the current consumption of the extruder is recorded for each material.

[0129] Cable Shrinkage

[0130] The shrinkage of the composition is determined with the cable samples obtained from the cable extrusion. The cables are conditioned in the constant room at least 24 hours before the cutting of the samples. The conditions in the constant room are 23±2° C. and 50±5% humidity. Samples are cut to 400 mm at least 2 m away from the cable ends. They are further conditioned in the constant room for 24 hours after which they are place in an oven on a talcum bed at 100° C. for 24 hours. After removal of the sample from the oven they are allowed to cool down to room temperature and then measured. The shrinkage is calculated according to formula below:

[(LBefore−LAfter)/LBefore]×100%, whereinL is length.

[0131] UV Ageing

[0132] UV ageing was performed according to VW PV 3930—Weathering in Moist, Hot Climate” or “Florida test” performed according to DIN EN ISO 4892-02.

[0133] Tensile Properties

[0134] Specimen was made according to ISO-527-2 5A. Test method of ISO 527-1,-2:2012, method B was used, employing extensometer Zwick MultiXtens, and evaluated according to ISO 527-1, method B.

[0135] Nominal tensile strain at break was measured according to ISO 527-1,-2:2012 Method B-Extensometer till Yield+Crosshead till break) 3. Results

[0136] Four samples were prepared using the carbon black masterbatch (MB) in PE1 carrier, wherein the carbon black MB was compounded with polymer base resin PE2, in an amount such that the amount of CB in the final composition is 0.25-1 wt % for Sample 1-4 (Table 2). Compounding was implemented on ZSK 18 MEGAlab laboratory twin screw extruder under the following conditions: speed=200 rpm; melt temperature 175-190° C.; pressure 45-50 bar; output 5 kg/h. Plaques of size 150*80*3 mm were produced from the resulting composition using injection moulding on Engel ES 700H/80V/700H/250 3K machine under following conditions: injection speed=11 mm/s; injection time 3.4 sec; switching pressure 66 bar; holding time during backpressure 15 sec; cooling time 20 sec; cycle time 45 sec; melt temperature 150° C.; mould temperature 50° C.

TABLE-US-00002 TABLE 2 Compounding of Samples 1-4 Comp. Components Sample Inv. Inv. Inv. Inv. (wt %) PE3 Sample 1 Sample 2 Sample 3 Sample 4 PE2 99.1  98.85 98.6  98.35 Antioxidant 0.2 0.2 0.2 0.2 Antistatic agent  0.15  0.15  0.15  0.15 UV-agent 0.3 0.3 0.3 0.3 Carbon black 2.6  0.25 0.5  0.75 1   Shrinkage (%)  1.05 <1   <1   — —

[0137] Laser Marking Behaviour

[0138] Laser marking was carried out using Laser machine, SpeedMarker 700, 20W Fiber laser. For marking, a frequency range of 20-100 KHz and power varying between 5-70% of 20W was used. Speed was kept constant at 2000 mm/s.

[0139] FIGS. 1-4 show laser printed samples with a combination of different amounts of carbon black and UV agent. Each square represents a combination of frequency to power. The samples are assessed visually by a human being. Best contrast quality is achieved using 0.25% of carbon black (FIG. 1). As may be seen, the contrast becomes poor if the amount of carbon black present exceeds 0.5 wt % (FIGS. 3 and 4).

[0140] As may be seen in Table 2, the inventive samples showed excellent shrinkage of below 1%.

TABLE-US-00003 TABLE 3 UV ageing properties Ageing 0 507 1008 4000 6000 Tensile stress at break, MPa Inv. Sample 1 24.64 21.79 24.12 26.07 26.14 Inv. Sample 2 26.46 21.74 24.54 24.01 22.19 Comp. Sample 25.3  24.74 21.93 18.83 23.99 Nominal tensile strain at break, % Inv. Sample 1 547.48  453.65  507.1  561.33  561.55  Inv. Sample 2 572.33  429.65  517.66  522.21  483.12  Comp. Sample 582.85  548.2  502.53  509.2  541.12 

[0141] As may be seen in Table 3, the inventive samples exhibit excellent UV ageing properties.

[0142] Although the present invention has been described with reference to various embodiments, those skilled in the art will recognize that changes may be made without departing from the scope of the invention. It is intended that the detailed description be regarded as illustrative, and that the appended claims including all the equivalents are intended to define the scope of the invention.