USE OF A COMPOSITION FOR THE MANUFACTURE OF A FOAMED ARTICLE

Abstract

The present invention relates to the use of a composition comprising 60-98 wt. % of polypropylene, 2-40 wt. % of low density polyethylene, 0.1-10 wt. % of compatibiliser wherein the compatibiliser is a BAB or AB type of block copolymer comprising a polypropylene block A and a polyester block B, or wherein the compatibiliser is a graft copolymer of the type ABn having a polypropylene backbone A and polyester block(s) B grafted thereon, with n being at least 1, and the polyester block(s) B have an average M/F ratio from 8-32, wherein M is the number of backbone carbon atoms in the polyester not including carbonyl carbon atoms, and F is the number of ester groups in the polyester block(s), wherein the wt. % is based on the sum of the amount polypropylene, low density polyethylene and compatibiliser, for the manufacture of a foamed article.

Claims

1. A foamed article formed from a composition comprising 60-98 wt. % of polypropylene 2-40 wt. % of low density polyethylene 0.1-10 wt. % of compatibiliser wherein the compatibiliser is a BAB or AB type of block copolymer comprising a polypropylene block A and a polyester block B, or wherein the compatibiliser is a graft copolymer of the type ABn having a polypropylene backbone A and polyester block(s) B grafted thereon, with n being at least 1, and the polyester block(s) B have an average M/F ratio from 8-32, wherein M is the number of backbone carbon atoms in the polyester not including carbonyl carbon atoms, and F is the number of ester groups in the polyester block(s), wherein the wt. % is based on the sum of the amount polypropylene, low density polyethylene and compatibiliser.

2. The foamed article of claim 1 wherein the M/F ratio is at least 10.

3. The foamed article of claim 1 wherein the amount of compatibiliser is from 1-8 wt. %.

4. The foamed article of claim 1 wherein in the compatibiliser the block B is a polyester obtained by the ring opening polymerisation of at least one of cyclic ethylene brassylate, dodecalactone, tridecanolactone, tetradecalactone, pentadecalactone, hexadecalactone, heptadecalactone, octadecalactone, nonadecalactone, ambrettolide, or globalide.

5. The foamed article of claim 1 wherein in the compatibiliser the polypropylene block A or backbone A is a propylene homopolymer or a random propylene and ethylene or C.sub.4-C.sub.8 alpha olefin copolymer containing at most 5 wt. %, on the basis of the weight of the block or backbone, of ethylene or C.sub.4-C.sub.8 alpha olefin.

6. The foamed article of claim 1 wherein the polypropylene is a propylene homopolymer or a random propylene and ethylene or C.sub.4-C.sub.8 alpha olefin copolymer containing at most 5 wt. %, on the basis of the weight of the polypropylene, of said ethylene or a C.sub.4-C.sub.8 alpha olefin.

7. The foamed article of claim 1 wherein the amount of polypropylene is at least 70 wt. %, and the amount of low density polyethylene is from 5-20 wt. %.

8. The foamed article of claim 1 wherein the foamed article has a percentage of closed cells of at least 50% as determined in accordance with ASTM D2856.

9. The foamed article of claim 1 wherein the foamed article has a degree of expansion of from 1.05-40 wherein the degree of expansion is defined as the ratio between the density of the composition in molded state prior to foaming and the density of the foamed composition after foaming.

10. The foamed article of claim 1 consisting of the composition and residues of a chemical or physical foaming agent.

11. A method for the manufacture of a foamed article comprising the steps of i) providing a composition comprising 60-98 wt. % of polypropylene 2-40 wt. % of low density polyethylene 0.1-10 wt. % of compatibiliser wherein the compatibiliser is a BAB or AB type of block copolymer comprising a polypropylene block A and a polyester block B, or wherein the compatibiliser is a graft copolymer of the type ABn having a polypropylene backbone A and polyester B grafted thereon, with n being at least 1, and the polyester block(s) have an average M/F ratio from 8-32, wherein M is the number of backbone carbon atoms in the polyester not including carbonyl carbon atoms, and F is the number of ester groups in the polyester block(s) wherein the wt. % is based on the sum of the amount polypropylene, low density polyethylene and compatibiliser, ii) adding to said composition a physical or chemical foaming agent iii) foaming the composition of step ii into a foamed article.

12. The method of claim 11 wherein the foaming agent is added to the composition in an extruder and is mixed with the composition in molten state.

13. The method of claim 11 wherein the blowing agent is a physical foaming agent and wherein the foamed article is a obtained by extruding the composition through a die, or a chemical foaming agent and wherein the foamed article is obtained by first molding the composition of step ii) into a unfoamed intermediate article, followed by a step of foaming said unfoamed intermediate.

14. The foamed article of claim 1 wherein the foamed article is a foamed sheet, foamed packaging element, or foamed insulation element.

15. A composition comprising 60-98 wt. % of polypropylene 2-40 wt. % of low density polyethylene 0.1-10 wt. % of compatibiliser a physical or chemical foaming agent wherein the compatibiliser is a BAB or AB type of block copolymer comprising a polypropylene block A and a polyester block B, or wherein the compatibiliser is a graft copolymer of the type AB.sub.n having a polypropylene backbone A and polyester block(s) B grafted thereon, with n being at least 1, and the polyester block(s) B have an average M/F ratio from 2-25, wherein M is the number of backbone carbon atoms in the polyester not including carbonyl carbon atoms, and F is the number of ester groups in the polyester block(s) wherein the wt. % is based on the sum of the amount polypropylene, low density polyethylene and compatibiliser.

Description

EXAMPLES

[0169] Materials

[0170] ω-Pentadecalactone (PDL) (98%, Sigma-Aldrich) was dried over CaH.sub.2 and distilled under reduced pressure. Benzyl alcohol (BnOH) (99%, Merck) was dried over CaH.sub.2 (95%, Sigma-Aldrich) and distilled under reduced pressure. Toluene (Sigma-Aldrich) was dried using an MBraun-SPS-800 purification column system. Exxelor PO1020 was purchased from ExxonMobil. Methanol, pentamethyl heptane (from in house purification system) were used as received. Toluene (anhydrous, Sigma-Aldrich) and tetrahydrofuran (THF) (anhydrous, Sigma-Aldrich) were purified using an MBraun-SPS-800 purification column system and were kept in glass bottle with 4-Å molecular sieves under an inert atmosphere. 10-undecen-1-ol, ethanolamine and tin(II) 2-ethylhexanoate were purchased from Sigma Aldrich. Methylaluminoxane (MAO) (30 wt. % solution in toluene) was purchased from Chemtura. Diethyl zinc (DEZ) (1.0 M solution in hexanes), triisobutylaluminum (TiBA) (1.0 M solution in hexanes), di-n-butylmagnesium (MgBu.sub.2, 1.0 M solution in heptane), and 2,6-di-tert-butyl-4-methylphenol (BHT) (99%, purum), were purchased from Sigma-Aldrich. N,N′-bis(salicylidene)-2,2-dimethyl-1,3-propanediamine (98%, Sigma-Aldrich), trimethyl aluminum (2.0 M solution in toluene) and triisobutyl aluminum (1.0 M solution in hexanes) were purchased from Sigma Aldrich. rac-Me.sub.2Si(2-Me-4-Ph-Ind).sub.2ZrCl.sub.2 was purchased from MCAT GmbH, Konstanz, Germany.

[0171] PP500P is a semi-crystalline propylene homopolymer commercially available from SABIC having a melt flow of 3.1 g/10 min (ISO1133, 2.16 kg, 230° C.)

[0172] PP531P is a semi-crystalline propylene homopolymer commercially available from SABIC having a melt flow rate of 0.30 g/10 min (ISO 1133, 2.16 kg, 230° C.).

[0173] PP520 is a semi-crystalline propylene homopolymer commercially available from SABIC having a melt flow rate of 10.5 g/10 min (ISO 1133, 2.16 kg, 230° C.).

[0174] Daploy WB140, commercially available from Borealis, is a high melt strength propylene homopolymer having a melt flow rate of 2.1 g/10 min in accordance with ISO 1133 (230° C. and 2.16 kg).

[0175] 2008TN00 is low density polyethylene having a density of 920 kg/m.sup.3 and a melt flow rate of 7.5 g/10 min (ISO1133, 2.16 kg, 190° C.)

[0176] ExxelorPO1020, commercially available from ExxonMobil, is a maleic anhydride-grafted propylene homopolymer having a melt flow rate of 430 g/10 min in accordance with ISO 1133 (230° C. and 2.16 kg). The amount of grafted maleic anhydride (MAH) is about 0.43 wt. % on the basis of the weight the polymer.

[0177] Measurement Methods

[0178] Conversion of reactions was determined by NMR:

[0179] .sup.1H NMR analysis (.sup.1H-NMR) was carried out at 80-110° C. using deuterated tetrachloroethane (TCE-d.sub.2) as the solvent and recorded in 5 mm tubes on a Varian Mercury spectrometer operating at frequencies of 400 MHz. Chemical shifts in ppm versus TCE-d.sub.2 were determined by reference to the residual solvent signal.

[0180] M.sub.n, M.sub.w and the polydispersity index (PDI, Ð.sub.M) were determined as follows by size exclusion chromatography:

[0181] SEC measurements were performed at 150° C. on a Polymer Char GLDPE-IR® built around an Agilent GC oven model 7890, equipped with an autosampler and the Integrated Detector IR4. 1,2-dichlorobenzene (oDCB) was used as an eluent at a flow rate of 1 mL/min. The SEC-data were processed using Calculations Software GLDPE One®.

[0182] Melting (Tm) and crystallization (Tc) temperatures as well as enthalpies of the transitions were measured by differential scanning calorimetry (DSC) using a DSC Q100 from TA Instruments. The measurements were carried out at a heating and cooling rate of 10° C..Math.min.sup.−1 from −60° C. to 210° C. The transitions were deduced from the second heating and cooling curves.

[0183] Density analysis were carried out using PLT-A01 set for density determination for KERN PLT. The foam samples were immersed in water to determine the volume and the mass by weighing it on the balance. The volume determination is based on the Law of Archimedes.

[0184] The morphology of foam cell structures were characterised with a JEOL JSM 7800-F Field Emission Scanning Electron Microscopy (FE-SEM) at an operating voltage of 5 kV. A piece of foam sample were cryogenically cut using an ultra sharp razer blade for the cross-sectional morphology characterization. The foam cross section was viewed using the Large Depth of Focus (LDF) mode and the Lower Electron Detector (LED) detector in the FE-SEM. The LDF mode provides a larger depth of focus than conventional SEM mode, and is suitable for imaging of rough samples with micron size features. All the samples were sputter-coated with gold-palladium before SEM imaging in order to reduce the surface charging during imaging.

[0185] Typical Procedure for the Synthesis of Hydroxyl Functionalised Polypropylene Via Reactive Extrusion (REX):

[0186] ExxelorPO1020 with 2500 ppm of antioxidant, Irganox 1010, was introduced into a co-rotating twin-screw extruder under nitrogen atmosphere set with different temperature zones 50-90-160-165-170-170-180-180° C., respectively. Ethanolamine was added to the extruder in an amount such that the molar ratio of the anhydride groups and the ethanolamine was equal to 1.1:1. The mixture was processed and then cooled and granulated. The product was dried in a vacuum oven for 10 h at 70° C.

[0187] Typical Procedure for the Synthesis of Hydroxyl Functionalised Polypropylene Via Catalytic Route:

[0188] Polymerization experiments were carried out in a stainless steel autoclave with an internal volume of 2.1 L. The reactor is equipped with interMIG stirrer, operated at 900 rpm. Pentamethyl heptane “PMH” (400 mL) was added into the autoclave. Propylene (typically 200 Nl/h) was dosed via Brooks Mass flow controller into the headspace and the propylene was set at the desired pressure (9 bar). The temperature was set at 87° C. Off-gas was continuously vented. Subsequently, the MAO (30 wt. % solution in toluene, 9 mmol) was dosed using the injection vessel with an additional 400 mL of PMH. After stirring the mixture for 15-20 min at 87° C., a premixed solution of 10-undecen-1-ol and TiBA (TiBA/C11=OH=1, 0.85 M, 10 mL), DEZ (1 M solution in hexane, 1 mL) and TiBA (1 M solution in hexane, 4 mL) were introduced into the reactor under a nitrogen atmosphere with PMH through the injection Schlenk vessel. The mixture was stirred for 10 min and a solution of rac-dimethylsilyl bis(2-methyl-4-phenyl-1-indenyl) zirconium dichloride catalyst (6 μmol) in approximately 5 mL of toluene was injected into the reactor applying an over pressure of nitrogen. After dosing all the components, the total volume of the added PMH was 1 L. The reactor temperature was kept at 87±3° C. by cooling with an oil LAUDA system. At the end of the reaction (20 min), the mixture was drawn off via a bottom valve. A mixture of acidified methanol (2.5% v/v HCl) and Irganox 1010 was added and the resulting suspension was filtered, washed with demineralised water and dried at 60° C. in vacuo overnight.

[0189] Typical Procedure for Synthesis of PPDL Using Catalyst 1.

[0190] A glass crimp cap vial was charged with toluene (1.0 mL), PDL (0.500 g, 2.08 mmol), benzyl alcohol (0.22 mg, 2.08 μmol) and catalyst 1 (1.26 mg, 2.08 μmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100° C. The progress of the reaction was followed by H NMR spectroscopy by taking aliquots at set time intervals. The synthesised copolymer was cooled to room temperature and quenched using acidified methanol, isolated and dried in vacuum at room temperature for 18 h. Table 1 specifies the molecular weight (Mn and Mw) of PPDL. The structure of catalyst 1 is shown in FIG. 1.

[0191] Typical Procedure for Synthesis of PPDL Using Catalyst 2.

[0192] A glass crimp cap vial was charged with toluene (1.0 mL), PDL (0.500 g, 2.08 mmol), benzyl alcohol (0.22 mg, 2.08 μmol) and catalyst 2 (0.73 mg, 2.08 μmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100° C. The progress of the reaction was followed by H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated and dried in vacuum at room temperature for 18 h. Table 2 specifies the reaction molecular weight (Mn and Mw) of PPDL. The structure of catalyst 1 is shown in FIG. 2.

[0193] Typical Procedure for the Synthesis of PP-Graft-PPDL Via REX:

[0194] The experiments were carried out in a co-rotating twin-screw extruder at 40-120-165-170-180-180-180-180-170-155-150° C. with a screw rotation speed of 65 rpm and throughput 3 kg/hr. Hydroxyl-functionalised polypropylene (PP-OH, Mn=36,200 g/mol, Mw=166,000 g/mol, PDI=4.59, 1995 g), polypentadecalactone (PPDL, 990 g, Mn=35,100 g/mol, Mw=56,800 g/mol, PDI=1.6) and stannous octoate as catalyst (Sn(Oct).sub.2, 15 g) were fed into the extruder. The process of extrusion was carried out using two feeders. From the first feeder PP-OH and from the second-blend of the other components were dosed. The mixture was processed and then cooled and granulated. The copolymer was dried in a vacuum oven for 10 h at 70° C.

[0195] Typical Procedure for Preparation of PP/LDPE Blends.

[0196] Isotactic polypropylene (iPP) (SABIC PP500P, 800 g, MFI=10.5 g/10 min (230° C., 2.16 kg)), low density polyethylene (LDPE) (SABIC 2008TN00, 200 g, MFI=7.5 g/10 min (190° C., 2.16 kg)) were fed into the extruder chamber. The mixture was processed for 3 minutes at 190° C. with a screw rotation rate of 100 rpm. Afterwards the mixture was evacuated directly to a mini-injection molding machine to prepare samples for mechanical properties and morphology analysis. The same procedure was used for the preparation of PP520/LDPE2008TN00, PP531/LDPE2008TN00 blends.

[0197] Typical Procedure for Preparation of PP/LDPE Blends Compatibilised by PP-Graft-PPDL Copolymer.

[0198] 770 gram of isotactic polypropylene PP500P, 180 gram of LDPE 2008TN00) and 50 gram of the PP-graft-PPDL compatibiliser were fed into an extruder chamber. The mixture was processed for 3 minutes at 190° C. with a screw rotation rate of 100 rpm. Afterwards the mixture was evacuated directly to a mini-injection moulding machine to prepare samples for mechanical properties and morphology analysis. The same procedure was used for the preparation of PP520/LDPE2008TN00 and PP531/LDPE2008TN00 blends.

TABLE-US-00001 TABLE 1 PPDL PPDL PP-graft- M.sub.n M.sub.w PP/LDPE PPDL Entry Catalyst [kg .Math. mol.sup.−1] [kg .Math. mol.sup.−1] PP LDPE [wt %/wt %] [wt %] 1 1 63.1 123.8 PP500P 2008TN00 77/18 5 2 1 43.5 85.6 PP500P 2008TN00 77/18 5 3 1 18.2 38.6 PP500P 2008TN00 77/18 5 4 1 48.1 91.9 PP500P 2008TN00 77/18 5 5 1 63.5 127.6 PP500P 2008TN00 77/18 5 6 1 39.9 89.5 PP500P 2008TN00 77/18 5 7 1 23.3 45.8 PP500P 2008TN00 77/18 5

[0199] The compatibilisers are AB block copolymers.

TABLE-US-00002 TABLE 2 PPDL, PPDL, PP-graft- M.sub.n M.sub.w PP/LDPE PPDL Entry Catalyst [kg .Math. mol.sup.−1] [kg .Math. mol.sup.−1] PP LDPE [wt %/wt %] [wt %] 1 2 35.1 56.8 PP500P 2008TN00 77/18 5 2 2 40.6 79.0 PP500P 2008TN00 77/18 5 3 2 32.0 59.6 PP500P 2008TN00 77/18 5 4 2 70.8 181.2 PP500P 2008TN00 77/18 5 5 2 75.4 146.2 PP500P 2008TN00 77/18 5 6 2 29.7 58.7 PP500P 2008TN00 77/18 5 7 2 90.1 176.8 PP500P 2008TN00 77/18 5 8 2 115.1 232.7 PP500P 2008TN00 77/18 5 9 2 79.8 156.0 PP500P 2008TN00 77/18 5 10 2 54.9 123.0 PP500P 2008TN00 77/18 5

[0200] Synthesis of Mg(BHT).sub.2(THF).sub.2 Catalyst 1.

[0201] In the glovebox, 2,6-di-tert-butyl-4-methylphenol (BHT, 4.40 g, 20 mmol) was introduced into Schlenk glass and dissolved in dry tetrahydrofuran (30 mL). The mixture was cooled down to 0° C. in an ice bath. Subsequently n-Bu.sub.2Mg (3.89 ml of 1 M solution in hexane, 20 mmol of n-Bu.sub.2Mg) was added to BHT solution in THE and stirred at room temperature for 24 h under nitrogen atmosphere. The solvent was removed under reduced pressure. A white powder was rinsed with dry heptane (3×15 mL) and dried under reduced pressure. Yield: 4.41 g (73.3%).

[0202] Synthesis of Aluminum-Salpen Catalyst 2.

[0203] N,N′-bis(salicylidene)-2,2-dimethyl-1,3-propanediamine (2.0 g, 5.7 mmol) was suspended in toluene (30 mL) under N.sub.2 flow. Subsequently, Al(CH.sub.3).sub.3 (2 M solution in toluene, 2.85 mL, 5.7 mmol) was added via syringe and the mixture was stirred at room temperature for 1 h. The thus obtained solution was concentrated to half the original volume and pale yellow crystals of 2 were isolated with a yield of 88%.

[0204] Foaming experiments were performed on a lab scale foaming unit consisting on an 11 mm co-rotating twin screw extruder for melting the polymer composition and injection of the physical foaming agent iso-butane. The outlet of the extruder is directly fed into a static mixer consisting of three zones (entrance zone, mixer zone and tool zone) for further mixing the foaming agent with the molten polymer composition and controlling of the temperature. The amount of polymer composition fed to the extruder was 290 g/h and the amount of iso-butane that was dosed in the extruder was kept at a constant value of 28.4 g/hr. At the start of the experiment the mixer and tool zone temperatures were set at 200° C. During the experiments the temperatures of the mixer and tool zones were lowered in steps of 5-10° C. each time allowing five minutes for stabilisation of the process at each temperature setting. Once the temperatures were stabilised the tool zone pressure was set at 30 bars by adjusting the opening of the die. Initial settings of the foaming unit are per the Table 3 below.

TABLE-US-00003 TABLE 3 Extruder Screwspeed [rpm] 75 T1 ° C. 80 T2 ° C. 160 T3 ° C. 210 T4 ° C. 210 T5 ° C. 210 T6 ° C. 210 T7 ° C. 210 T8 ° C. 210 Static mixer T_entrance ° C. 200 T_mixer ° C. 200 T_Tool ° C. 200 P_Tool Bar 30 Foaming die Temperature ° C. 200

[0205] T1-T8 are the temperatures of the sections 1-8 of the extruder.

[0206] FIG. 2 shows the density of the foams based on:

[0207] PP500 (-x-)

[0208] PP500/LDPE compatibilised by PP-graft-PPDL copolymer (-.circle-solid.-); The material of Table 2, entry 5 was used.

[0209] Daploy WB140 (-.box-tangle-solidup.-)

[0210] The horizontal axis shows the temperature of the foaming die, while the vertical axis shows the density of the foamed material. The curves essentially show that compositions as disclosed herein can indeed be foamed.

[0211] FIG. 3 shows SEM analysis of the foam based on the materials of Table 2, entry 5. The pictures show that the cell walls are predominantly continuous meaning that the foam is predominantly a closed cell foam.