Polymer composition and expanded polypropylene beads made from the polymer composition

Abstract

The present invention relates to a polymer composition comprising (85-100 wt %) of a propylene copolymer based on the total amount of the polymer composition, wherein the comonomer in the propylene copolymer is selected from moiety derived from ethylene, an -olefin having (4) to (20) carbon atoms or a combination thereof, wherein the amount of the comonomer is in the range of (0.50 to 4.5) wt % based on the propylene copolymer, wherein the fraction of melted propylene copolymer in the temperature range from (116 to 151 C.) is in the range from (65 to 90) wt % based on the total weight of the propylene copolymer. The present invention also relates to expanded polypropylene (EPP) beads comprising said polymer composition. The invention further relates to the use of such EPP beads. The invention further relates to a process for preparing such EPP beads. The present invention also relates to an article made from said EPP beads. The invention further relates to the use of such article. The invention further relates to a process for preparing such article.

Claims

1. A polymer composition comprising: 100 wt % of a propylene copolymer based on the total amount of the polymer composition, wherein a comonomer in the propylene copolymer is selected from moiety derived from ethylene, an -olefin having 4 to 20 carbon atoms or a combination thereof, wherein the amount of the comonomer is in the range of 3.7 to 4.0 wt % based on the propylene copolymer, wherein the fraction of the polymer composition melted in the temperature range from 116 to 151 C. is in the range from 70 to 90 wt % based on the total weight of the polymer composition; wherein at 151 C. tan of the polymer composition is in the range from 0.15 to 0.11 when tested according to ASTM D4092-07 (2013) with the following setting: Oscillatory Temperature Ramp with 17.5 mm Single Cantilever Geometry at 1 Hz, 6% Oscillation strain, temperature ramps from 27 to 160 C. at the rate of 5 C./min, wherein the melt flow index (MFI) of the propylene copolymer is in the range from 8 to 10 g/10 min when determined according to ISO1133-1:2011 with 2.16 kg load at 230 C., and wherein the strain at break of the polymer composition is from 500 to 551% when determined according to ISO527-1(2012).

2. The polymer composition according to claim 1 wherein the comonomer in the propylene copolymer is moiety derived from ethylene.

3. A process for the preparation of expanded polypropylene beads comprising the steps in the following order: providing the polymer composition of claim 1; placing the polymer composition of and water in a pressurized sealed container, wherein the mass ratio between the polymer composition and water is in the range from 1:5 to 5:1; heating the container to a temperature range from 140 to 165 C. and injecting required amount of inert gas such as carbon dioxide, nitrogen or air into the container to reach a pressure range from 0.5 to 6.0 MPa; maintaining the temperature and pressure for a duration in the range from 10 to 60 min once a target temperature and pressure are reached; discharging the container to room temperature and atmosphere level of pressure 1 bar; and taking the expanded polypropylene beads from the container and drying the expanded polypropylene beads.

4. Expanded polypropylene beads comprising 95 to 100 wt % of the polymer composition of claim 1.

5. A steam molded article prepared with the expanded polypropylene beads of claim 4.

6. A process for the preparation of a steam molded article comprising the steps of providing the expanded polypropylene beads of claim 4; and steam molding the expanded polypropylene beads into the article by placing the expanded polypropylene beads in a mold and fuse-bonding them, wherein the temperature range of this step is from 130 C. to 150 C., wherein the pressure range of this step is from the 2.7 to 4.5 MPa, wherein the duration of this step is in the range from 5 to 20 min.

Description

EXAMPLES

(1) Material

(2) Polymer Composition 1: Polymer Composition 1 comprises 100 wt % of a polypropylene random copolymer produced in Sperizone technology with a Ziegler-Natta catalyst. The comonomer in Polymer Composition 1 is moiety derived from ethylene. The amount of moiety derived from ethylene is 3.80 wt % based on the total amount of Polymer Composition 1.

(3) Polymer Composition 2: Polymer Composition 2 comprises 100 wt % of a polypropylene random copolymer available from The Polyolefin Company (Singapore) with commercial name COSMOPLENE W331. The comonomer in Polymer Composition 2 is moiety derived from ethylene. The amount of moiety derived from ethylene is 3.00 wt % based on the total amount of Polymer Composition 2.

(4) Both Polymer Compositions were provided in pellet form of quasi-spherical shape, the diameter of their pellets is in the range from 0.5 to 1.5 mm.

(5) Sample Preparation

(6) Injection Molding

(7) Pellets of polymer compositions were injection molded into specimens of dimensions 4*10*40 mm to be used in DMA test according to ASTM D4092-07(2013) and specimens of shapes according to ISO527-1A (2012) to be used in tensile test.

(8) EPP Preparation

(9) 25 kg of Polymer Composition pellets was placed in an autoclave with interior volume of 150 L together with 25 kg water. Then the autoclave was sealed and heated, CO.sub.2 was injected in the autoclave to maintain the pressure at 3 MPa at the temperature setting indicated in Table 1. Once the temperature and pressure reached the target level, they were maintained for 20 min for CO.sub.2 to impregnate Polymer Composition pellets. Afterwards, the autoclave was discharged to atmosphere pressure 1 Bar and room temperature 25 C. During the discharge of the autoclave, Polymer Composition pellets were expanded into EPP beads. In the end, the EPP beads were taken out of the autoclave and dried.

(10) TABLE-US-00001 TABLE 1 EPP Production 1 2 3 Temperature ( C.) 149.5 150 150.5
Steam Molded Article Preparation

(11) EPP beads produced from Polymer Composition 1 and 2 with foaming ratio 25 were steam molded under the condition in table 2 for 10 min into an article with dimensions 50505 cm.

(12) TABLE-US-00002 TABLE 2 Polymer Polymer Composition 1 Composition 2 Temperature ( C.) 142 145 Pressure (MPa) 3.83 4.16
Testing Method
MFI

(13) MFI of the pellets of the Polymer Compositions were tested according to ISO1133-1:2011 with 2.16 kg load at 230 C.

(14) Strain at Break

(15) Strain at break were tested in a tensile test according to ISO527-1(2012) on the injection molded specimens of the Polymer Compositions

(16) Thermal-Mechanical Test

(17) DMA measurement according to ASTM D4092-07(2013) was conducted with the following setting: Oscillatory Temperature Ramp with 17.5 mm Single Cantilever Geometry at 1 Hz, 6% Oscillation strain, temperature ramps from 27 to 160 C. at the rate of 5 C./min on a TA Instrument DMA 850 machine with injection molded specimens. tan at 151 C. of the Polymer Compositions was obtained in this test.

(18) Thermal Behavior

(19) Fraction of Polymer Compositions melted in the range between 116 to 151 C. was measured by SSA following the protocol of ISO 11357-3:2018 with the following temperature setting: a) Isothermal 0 C. for 5 minutes. b) Heat from 0 C. to 230 C. with a temperature change rate of 10 C./min c) Isothermal 230 C. for 5 minutes. d) Cool from 230 C. to 25 C. with a temperature change rate of 10 C./min e) Isothermal 25 C. for 5 minutes. f) Heat from 25 C. to 166 C. with a temperature change rate of 10 C./min g) Isothermal 166 C. for 5 minutes. h) Cool from 166 C. to 25 C. with a temperature change rate of 10 C./min i) Isothermal 25 C. for 5 minutes. j) Heat from 25 C. to 161 C. with a temperature change rate of 10 C./min k) Isothermal 161 C. for 5 minutes. l) Cool from 161 C. to 25 C. with a temperature change rate of 10 C./min m) Isothermal 25 C. for 5 minutes. n) Step from i) to m) are repeated in the subsequent loops by lowering of the step size by 5 C. everytime, using an isothermal time of 5 minutes until 41 C. is reached.

(20) The SSA test was carried out on DSC TA Q1000.

(21) The fraction of Polymer Compositions melted 116 to 151 C. was calculated as the ratio between the melt enthalpy within in the range of 116 to 151 C. and the total melt enthalpy. The enthalpy values were exported directly via the software associated with DSC TA Q1000.

(22) Compression Modulus of Steam Molded Article

(23) Compression modulus of steam molded article was tested according to ISO844: 2014.

(24) Density

(25) Density of the pellets of both Polymer Compositions and EPP beads produced from both Polymer Compositions in EPP production 1, 2 and 3 were tested according to ISO845: 2006.

(26) Result and Discussion

(27) The result of aforementioned test are present in Table 3.

(28) TABLE-US-00003 TABLE 3 Polymer Polymer Composition 1 Composition 2 MFI (dg/min) 8.6 6.9 Comonomer content (wt %) 3.80 3.00 Density of pellets (g/cm.sup.3) 0.90 0.90 Strain at break (wt %) 484 551 Melt enthalpy 116 to 151 C. (J/g) 45.8 47.9 Total melt enthalpy (J/g) 73.5 67.3 Fraction melted 116 to 151 C. (wt %) 62.3 71.1 Average tan at 151 C. 0.13 0.18 Density of EPP beads from EPP Production 1 (g/cm.sup.3) 0.044 0.098 Foaming ratio in EPP Production 1 20.5 9.2 Density of EPP beads from EPP Production 2 (g/cm.sup.3) 0.044 0.078 Foaming ratio in EPP Production 2 20.5 11.5 Density of EPP beads from EPP Production 3 (g/cm.sup.3) 0.043 0.067 Foaming ratio in EPP Production 3 21.0 13.5 Foaming ratio variation with EPP Production 1, 2 and 3 0.5 4.3 Compression modulus of the steam molded article (MPa) 2.2 2.2

(29) According to table 3, a larger fraction of Polymer Composition 1 is melted in the temperature range from 116 to 151 C. than Polymer Composition 2, and Polymer Composition 1 has a lower tan value at 151 C. than Polymer Composition 2. As a result, the foaming ratio variation of Polymer Composition 1 is significantly improved comparing to Polymer Composition 2. Moreover, although the steam molding condition of the EPP beads made from Polymer Composition 1 is of lower temperature and pressure than that of the EPP beads made from Polymer Composition 2, the compression modulus of the final steam molded articles based on Polymer Composition 1 and Polymer Composition 2 is the same. It indicates that an article prepared in a steam molding process with reduced energy consumption while keeping the stiffness at the same level is obtained. Furthermore, Polymer Composition 1 shows better tenacity than Polymer Composition 2 with a higher strain at break.