Polymer composition comprising at least one vinyl aromatic diene block copolymer and specific amounts of oil

Abstract

The present invention relates to a polymer composition comprising at least one block copolymer and a specific amount of at least one oil component. The block copolymer, which is the polymeric matrix of the inventive composition, is built up from at least one vinyl aromatic monomer M.sub.A and at least one conjugated diene monomer M.sub.B, in particular the block copolymer is a styrene butadiene block copolymer (SBC).

Claims

1. A polymer composition consisting of: 94.9 to 97.49% by weight, based on the total polymer composition: at least one block copolymer P, having one of the following formulas (I) to (III):
(A-B/A).sub.n-A  (I),
X—[(B/A-A).sub.n].sub.m+1  (II),
Y—[(B/A-A).sub.n].sub.m+1  (III), wherein the abbreviations and indices have the following meaning: A is a vinyl aromatic block forming a hard phase, which is composed of at least one vinyl aromatic monomer M.sub.A, B/A is a diene block forming a soft phase, which is composed of at least one conjugated diene monomer M.sub.B and at least one vinyl aromatic monomer M.sub.A, X is the radical of an m+1-functional initiator, Y is the radical of an m+1-functional coupling agent, n is a natural number from 1 to 10, and m is a natural number from 1 to 10; 2.5 to 5% by weight, based on the total polymer composition, at least one oil component C, wherein the oil component is one or more paraffin oil; and 0.01 to 1% by weight, based on the total polymer composition, one or more further components E; wherein: the at least one block copolymer P comprises 40 to 75% by weight, based on the block copolymer P, of the at least one vinyl aromatic monomer M.sub.A and 25 to 60% by weight, based on the block copolymer P, of the at least one conjugated diene monomer M.sub.B; the glass transition temperature's T.sub.g of the vinyl aromatic block's A is/are above 25° C. and the glass transition temperature's T.sub.g of the diene block's B/A is/are below 25° C., the proportion of the vinyl aromatic block's forming the hard phase is from 5 to 40% by volume, based on the total volume of block copolymer P; the relative amount of 1,2 linkages in the diene block B/A, based on the sum of 1,2- and 1,4-cis/trans-linkages, is less than or equal to 15%; and the weight average molecular weight M.sub.w of the block copolymer P is in the range of 120,000 to 300,000 g/mol.

2. The polymer composition according to claim 1, wherein the vinyl aromatic monomer M.sub.A is at least one monomer selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, and 1,1-diphenylethylene, and the conjugated diene monomer M.sub.B is at least one monomer selected from the group consisting of butadiene and isoprene.

3. The polymer composition according to claim 1, wherein the vinyl aromatic monomer M.sub.A is at least one monomer selected from the group consisting of styrene and α-methylstyrene, and the conjugated diene monomer M.sub.B is butadiene.

4. The polymer composition according to claim 1, wherein the molecular weight of the vinyl aromatic block's A is/are in the range of 5,000 to 100,000 g/mol; and the molecular weight of the diene block's B/A is/are in the range of 20,000 to 250,000 g/mol.

5. The polymer composition according to claim 1, wherein the glass transition temperature T.sub.g of the vinyl aromatic block's A is/are above 50° C.; and the glass transition temperature T.sub.g of the diene block's B/A is/are below 5° C.

6. The polymer composition according to claim 1, wherein the relative amount of 1,2 linkages in the diene block B/A of the block copolymer P, based on the sum of 1,2- and 1,4-cis/trans-linkages, is less than or equal to 12%.

7. The polymer composition according to claim 1, wherein the oil component C is at least one paraffin oil having a viscosity in the range of 20 to 300 m Pas, measured at a temperature in the range of 20 to 25° C.

8. The polymer composition according to claim 1, wherein the block copolymer P is obtained by a process which comprises the step of forming the block copolymer by sequential anionic polymerization, where at least the polymerization step of the at least one block B/A takes place in the presence of a potassium salt as randomizer.

9. A moulded part made from the polymer composition according to claim 1.

10. The moulded part according to claim 9, wherein the moulded part is selected from extruded sheets, extruded multilayer sheets, extruded tubings, multilumen tubings, drip chamber parts, food packagings, beakers, plates, and labels.

11. A process for the production of the polymer composition according to claim 1, wherein the at least one block copolymer P is mixed with the at least one oil component C, and optionally further components E.

12. The process according to claim 11, wherein the components are mixed by melt extrusion.

Description

EXAMPLE I: PREPARATION OF THE POLYMER COMPOSITIONS

(1) Polymer compositions based on styrene butadiene block copolymers (SBC) were prepared using the following components: P linear styrene butadiene triblock copolymer with a melt volume rate (200° C., 5 kg, determined according to ISO 1133) of 13 cm.sup.3/10 min, a butadiene content of 34.4% by weight and a molecular weight M.sub.w in the range of 155,200 to 185,900 g/mol C oil component, paraffin oil DAB 70 E further components E: E1: Zinc stearate, E2: Sumilizer™ GS, from Sumitomo Chemicals, phenolic antioxidant stabilizer, CAS 123968-25-2 E3: Irganox® 1010 from BASF SE, phenolic antioxidant stabilizer, CAS 6683-19-8 E4: Irgafos® 168 from BASF SE, phosphite processing stabilizer (tris(2,4-ditert-butylphenyl)phosphite

(2) The components were mixed by extrusion using the following parameters: Extruder type: ZSK 30 Extruder screw diameter: 30 mm Throughput: 5-10 kg/h Melt temperature: 210-250° C. Die temperature: 240° C.

(3) The polymer compositions according to examples 1 to 8 are summarized in the following table 1. The molecular weight M.sub.w of the polymer component P is given in table 2.

(4) TABLE-US-00001 TABLE 1 Polymer Compositions Example 1 2 3 4 5 6 7 8 P up to up to up to up to up to up to up to up to 100% 100% 100% 100% 100% 100% 100% 100% C 0 2.9 3.0 3.2 3.3 3.1 3.0 2.7 [% by weight] E1 1,203 1,201 1,189 1,252 1,100 1,010 1,128 1,035 [ppm] E2 1,857 2,101 2,068 2,043 2,038 1,922 1,919 1,908 [ppm] E3 1,922 2,048 1,995 1,999 2,089 1,972 1,950 1,951 [ppm] E4 2,392 1,869 1,363 2,030 1,756 1,955 1,846 1,644 [ppm]

EXAMPLE II: PHYSICAL DATA OF THE POLYMER COMPOSITIONS

(5) Analytical, optical and mechanical data of the examples 1 to 8, e.g. measured on injection-moulded test specimen, are summarized in the following Table 2.

(6) The test methods are described in Example III. Surprisingly, it is shown that the inventive SBC compositions of examples 2-5 do not show increased melt volume flow rate (MVR), despite containing up to 3% mineral oil. The polymer components of examples have similar molecular weight compared to example No. 1. Lower MVR however is important for good extrusion properties. Furthermore, the inventive samples 2-5 show higher bulk density and improved yield stress in comparison to the control sample without oil, at generally good clarity of >70% and low Haze of <30%. This result is surprising, because in the light of the state of the art, typically the addition of mineral oil addition to SBC compositions results in a higher melt flow. In case of extrusion applications, a lower MVR is important to allow higher melt strength after the extrusion die.

(7) TABLE-US-00002 TABLE 2 Properties of polymer compositions Example 2 3 4 5 Low Low High High 1 MVR, MVR, MVR, MVR, 6 7 8 M.sub.w 170,000 185,500 185,900 177,200 167,800 156,400 155,200 158,700 [g/mol] MVR 13.4 8.4 7.1 11.1 11.3 17.3 16.8 17.7 [g/10 min] Vicat softening 47.7 38.9 38.7 39.4 38.2 39.4 39.2 39.9 point [° C.] Bulk density 588 608 595 599 617 618 619 618 [g/l] Yield stress 4.0 Type D Type D Type D Type D Type D Type D Type D [MPa] E modulus 81.25 84.2 97.4 83.6 46.8 49.5 50.6 36.1 [MPa] Shore A — 78 78 80 77 82 81 70 compression Shore D — 24 25 26 25 27 26 25 compression YI 11.2 13.4 14.4 13.0 12.5 15.0 17.0 15.1 Transmittance 81.8 79.9 81.9 81.7 81.2 81.8 82.1 81.4 [%] Haze [%] 15.4 27.2 21.3 17.8 22.7 13.6 13.1 24.4 Clarity [%] 96.4 68.8 70.3 71.1 63.0 88.0 90.8 74.8

(8) Yield stress “Type D” means that no yield point on the stress-strain curve can be determined.

EXAMPLE III: TEST METHODS

(9) The following test methods are used for characterization of the SBC compositions (see data of Table 2): The weight average molecular weights M.sub.W of the SBC block copolymers were analysed using gel permeation chromatography (GPC) on polystyrene gel columns (Polymer Labs, mixed B type) with monodisperse polystyrene standards at room temperature using tetrahydrofuran as eluent.

(10) The Melt Volume Flow Rate (MVR) was been determined using the polymer granulate according to ISO 1133-1:2011-12 at 200° C. with a load of 5 kg.

(11) The polymer compositions according to Examples 1 to 8 as described above were processed to standard test specimens. For mechanical measurements 2 mm thick sheets were produced by compression moulding (200° C., 3 min) and test specimens were produced. The tests were performed as described in the following Table 3:

(12) TABLE-US-00003 TABLE 3 Test methods Test Description Melt Flow Rate ISO 1133-1: 2011-12 Vicat Softening Point load 1 kg, temperature 25° C. Bulk density ISO 1183-1 Tensile Properties ASTM D-638 Shore hardness A and D DIN ISO 7619-1 compression 200° C., annealed 50° C. for 1 hour Yellowness Index YI ISO 17223 Transmittance; Haze ISO 13468

(13) Typically, the Shore A scale is used for soft rubbers while the Shore D scale is used for tough rubbers. The depth of indentation or penetration of a steel rod is typically measured on a scale of 0 to 100. The steel rod is either configured as a defined frustum cone (Shore A) or a defined needle pin (Shore D).

(14) The properties clarity, haze and transmittance were determined using haze-gard plus (BYK Gardner GmbH) (illuminate CIE-C). The clarity was determined on basis of ASTM D-1044.