Polyolefins composition with low CLTE and reduced occurrence of flow marks

Abstract

The invention relates to a novel polyolefin composition having a low coefficient of thermal expansion (CLTE) and having a reduced occurrence of flow marks. The novel polyolefin compositions comprise a heterophasic polypropylene composition, ethylene/1-butene elastomer and an inorganic filler.

Claims

1. A polyolefin composition comprising: a. 35-90 wt %, based on the weight of the polyolefin composition, of a heterophasic polypropylene composition having a continuous matrix phase and a discontinuous phase, wherein the continuous matrix phase comprises two propylene homopolymers of different MFR2 and wherein the discontinuous phase comprises two ethylene-propylene rubbers with different molecular weight, and wherein the heterophasic polypropylene composition comprises: i. 10-50 wt %, based on the weight of the heterophasic polypropylene composition, of a first propylene homopolymer (PPH1) having an MFR.sub.2 measured according to ISO 1133 of from 30-80 g/10 min (230 C., 2.16 kg), ii. 20-65 wt %, based on the weight of the heterophasic polypropylene composition, of a second propylene homopolymer (PPH2) having an MFR.sub.2 measured according to ISO 1133 of from 100-250 g/10 min (230 C., 2.16 kg), iii. 5-30 wt %, based on the weight of the heterophasic polypropylene composition, of a first xylene cold soluble fraction (XS1) having an intrinsic viscosity IV.sub.XS1 of 2.0-3.0 dl/g, iv. 5-25 wt %, based on the weight of the heterophasic polypropylene composition, of a second xylene cold soluble (XS2) fraction having an intrinsic viscosity IV.sub.XS2 of 1.5-2.8 dl/g, with the proviso that IV.sub.XS1IV.sub.XS2, b. 5-40 wt %, based on the weight of the polyolefin composition, of an inorganic filler, and c. 5-25 wt %, based on the weight of the polyolefin composition, of an ethylene/1-butene elastomer; wherein the polyolefin composition has a CLTE 30/+80 C.<49 m/m.Math.K, a CLTE +23/+80 C.<57 m/m.Math.K, and a flexural modulus>1700 MPa.

2. The polyolefin composition according to claim 1, wherein the ethylene/1-butene elastomer has a density of from 850-880 kg/m.sup.3.

3. The polyolefin composition according to claim 1, wherein the ethylene/1-butene elastomer has an MFR.sub.2 measured according to ISO 1133 of from 0.5-10 g/10 min (190 C., 2.16 kg).

4. The polyolefin composition according to claim 1, wherein the inorganic filler is selected from the group consisting of talc and wollastonite.

5. The polyolefin composition according to claim 1, wherein the MFR.sub.2 measured according to ISO 1133 of the polyolefin composition is from 5.0-50 g/10 min (230 C., 2.16 kg).

6. The polyolefin composition according to claim 1, further comprising at least one alpha-nucleating agent.

7. The polyolefin composition according to claim 6, wherein the at least one alpha-nucleating agent is selected from the group consisting of aluminum hydroxy-bis[2,4,8,10-tetrakis(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphocin-6-oxidato] containing nucleating agents, sodium-2,2-methylene-bis(4,6-di-t-butylphenyl)phosphate, aluminium-hydroxy-bis[2,2-methylene-bis(4,6-di-t-butyl-phenyl)-phosphate], sorbitol based nucleating agents and polymeric nucleating agents.

8. The polyolefin composition according to claim 7, wherein the at least one alpha nucleating agent is a polymeric nucleating agent selected from the group consisting of vinylcycloalkane polymers and vinylalkane polymers.

9. A molded article comprising a polyolefin composition according to claim 1.

10. The molded article according to claim 9, being an injection moulded article.

Description

EXAMPLES

(1) The following materials were used:

(2) Polymer 1: Heterophasic propylene copolymer having an MFR of 11 g/10 min, with 65 wt % of a propylene homopolymer matrix (MFR=55 g/10 min) and 35 wt % of an ethylene-propylene rubber. XCS content is 35 wt %. IV of XCS is 2.5 dl/g. Ethylene content of XCS is 38 wt %. Polymer 1 further contains 0.1 wt % Pentaerythrityl-tetrakis(3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate and 0.1 wt % Tris (2,4-di-t-butylphenyl) phosphite and 0.05 wt % calcium stearate.

(3) Polymer 2: Heterophasic propylene copolymer having an MFR of 70 g/10 min, with 80 wt % of a propylene homopolymer matrix (MFR=160 g/10 min) and 20 wt % of an ethylene-propylene rubber. XCS content is 20 wt %. IV of XCS is 2.2 dl/g. Ethylene content of XCS is 36 wt %. The heterophasic copolymer contains 35 ppm pVCH as polymeric nucleating agent. Polymer 2 further contains 0.05 wt % Pentaerythrityl-tetrakis(3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate and 0.05 wt % Tris(2,4-di-t-butylphenyl)phosphite and 0.25 wt % of glyceryl monostearate

(4) Talc: Jetfine 3CA, commercially available from Luzenac. Jetfine 3CA has a D.sub.50 of 3.9 m, a topcut (D.sub.95) of 7.8 m, both calculated from the particle size distribution measured by laser diffraction according to ISO 13320-1:1999 and a screen residue (determined by Alpine Airjet) of max. 0.05% of particles>15 m.

(5) EB 1: ethylene-1-butene copolymer having an MFR (190 C., 2.16 kg) of 5.0 g/10 min and a density of 865 kg/m.sup.3. EB 1 is available as Engage 7447 from The Dow Chemical Company.

(6) EB 2: ethylene-1-butene copolymer having an MFR (190 C., 2.16 kg) of 1.2 g/10 min and a density of 862 kg/m.sup.3. EB 2 is available as Engage 7467 from The Dow Chemical Company.

(7) EO 1: Ethylene-1-octene copolymer, having an MFR (190 C., 2.16 kg) of 0.5 g/10 min and a density of 863 kg/m.sup.3. EB 3 is available as Engage 8180 from The Dow Chemical Company.

(8) EO 2: Ethylene-1-octene copolymer, having an MFR (190 C., 2.16 kg) of 13.0 g/10 min and a density of 864 kg/m.sup.3. EB 4 is available as Engage 8130 from The Dow Chemical Company.

(9) EO 3: Ethylene-1-octene copolymer, having an MFR (190 C., 2.16 kg) of 1.0 g/10 min and a density of 870 kg/m.sup.3. EB 5 is available as Engage 8100 from The Dow Chemical Company.

(10) EO 4: Ethylene-1-octene copolymer, having an MFR (190 C., 2.16 kg) of 5.0 g/10 min and a density of 870 kg/m.sup.3. EB 6 is available as Engage 8200 from The Dow Chemical Company.

(11) EO 5: Ethylene-1-octene copolymer, having an MFR (190 C., 2.16 kg) of 30.0 g/10 min and a density of 870 kg/m.sup.3. EB 7 is available as Engage 8400 from The Dow Chemical Company.

(12) CB: carbon black masterbatch: 40 wt % carbon black+60 wt % LDPE.

(13) AP: Additive package: 0.1 pbw Pentaerythrityl-tetrakis(3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate+0.1 pbw Tris(2,4-di-t-butylphenyl)phosphate+0.2 pbw % calcium stearate+1.1 pbw propylene homopolymer (MFR (230 C., 2.16 kg)=3 g/10 min).

(14) TABLE-US-00001 TABLE 1 (example compositions) CE1 CE2 CE3 CE4 CE5 IE1 IE2 polymer 1 [wt %] 30.0 30.0 30.0 30.0 30.0 30.0 30.0 polymer 2 [wt %] 35.0 35.0 35.0 35.0 35.0 35.0 35.0 EO 1 [wt %] 12.0 EO 2 [wt %] 12.0 EO 3 [wt %] 12.0 EO 4 [wt %] 12.0 EO 5 [wt %] 12.0 EB 1 [wt %] 12.0 EB 2 [wt %] 12.0 talc [wt %] 20.0 20.0 20.0 20.0 20.0 20.0 20.0 CB [wt %] 1.5 1.5 1.5 1.5 1.5 1.5 1.5 AP [wt %] 1.5 1.5 1.5 1.5 1.5 1.5 1.5

(15) TABLE-US-00002 TABLE 2 (properties of example compositions) Property unit CE1 CE2 CE3 CE4 CE5 IE1 IE2 MFR g/10 17.0 22.6 17.4 20.6 23.2 20.6 18.4 Flexural Modulus MPa 1953 1836 1896 1819 1825 1850 1914 Charpy 1eA +23 C. kJ/m.sup.2 56.7 47.6 52.7 48.9 40.0 44.7 51.3 Charpy 1eA 20 C. kJ/m.sup.2 9.1 7.8 8.5 7.4 5.8 8.3 9.6 Charpy 1eA 30 C. kJ/m.sup.2 6.7 5.7 6.5 5.6 4.9 6.1 7.2 HDT A @ 1.8 MPa C 58 56 57 56 56 57 58 HDT B @ 0.45 MPa C 106.7 104.0 102.5 100.4 101.9 104.3 104.7 Shrinkage radial % 0.70 0.72 0.70 0.73 0.77 0.70 0.68 Shrinkage tangential % 0.62 0.66 0.62 0.66 0.71 0.67 0.62 CLTE 30/+80 C. 51 49 54 55 58 43 46 CLTE +23/+80 C. 57 56 65 64 69 51 49 MSE Screw speed mm/s 57 11.2 15.7 11.2 16.3 18.0 9.2 7.2 MSE Screw speed mm/s 50 7.5 14.0 6.7 11.8 17.1 6.8 5.9 MSE Screw speed mm/s 35 3.6 6.4 3.7 7.1 6.4 3.5 3.4 MSE Screw speed mm/s 17 2.9 3.4 3.0 3.6 3.5 3.2 3.2 MSE Screw speed mm/s 8 2.1 2.3 2.4 2.2 2.2 2.1 2.1

(16) It can be seen that for the inventive examples the CLTE is significantly smaller. Further, also the inventive compositions show a significantly smaller tendency to exhibit flow marks at high injection speeds.