THERMOPLASTIC MOLDING COMPOUNDS

Abstract

The invention relates to thermoplastic molding compounds having melt viscosities of less than 30,000 mPas for use as a hot-melt adhesive, comprising the components A and B, wherein component A comprises one or more C.sub.3/C.sub.2 copolymers each produced with metallocene catalysts and each having a melt viscosity at 170° C. of less than 20,000 mPas, measured according to DIN 53019, and a molecular weight M.sub.W of 1000 g/mol to 50,000 g/mol, and component B comprises one or more C.sub.2/C.sub.3 copolymers each produced with metallocene catalysts and each having a melt flow index MI of 1 to 100 g/min, measured at 190° C./2.16 kg, according to ASTM D 1238, and a molecular weight M.sub.W of 50,000 g/mol to 300,000 g/mol. Said thermoplastic molding compounds, because of the viscosity and mechanical properties thereof, are suitable for fiber mesh applications.

Claims

1. A thermoplastic molding material comprising the components A and B, wherein the thermoplastic molding material has a melt viscosity at 170° C. of less than 30 000 mPas, wherein the component A comprises one or more C.sub.3/C.sub.2-copolymers each of which have been produced with metallocene catalysts and have a melt viscosity at 170° C. of less than 20 000 mPas measured according to DIN 53019 and a molecular weight M.sub.W of 1000 g/mol to 50 000 g/mol, and the component B comprises one or more C.sub.2/C.sub.3-copolymers each of which have been produced with metallocene catalysts and have a melt index MI of 1 to 100 g/min measured at 190° C./2.16 kg according to ASTM D 1238 and a molecular weight M.sub.W of 50 000 g/mol to 300 000 g/mol.

2. The thermoplastic molding material as claimed in claim 1, wherein the thermoplastic molding material has a melt viscosity at 170° C. of 100 to 25 000 mPas, preferably 500 to 20 000 mPas, particularly preferably 1000 to 15 000 mPas, measured according to DIN 53019.

3. The thermoplastic molding material as claimed in claim 1, wherein the thermoplastic molding material has a strength of not less than 8 MPa measured according to ISO 527 save that a non-standard test specimen produced by hot melt pressing and differing from the test specimen conforming to the standard in terms of its dimensions was used. The test specimens used have the following dimensions: total length: 50 mm, width of narrow part: 3.3 mm, width at ends: 7 mm, length of narrow parallel part: 25 mm, thickness: 1 mm.

4. The thermoplastic molding material as claimed in claim 1, wherein the thermoplastic molding material has a breaking elongation of more than 1000% measured according to ISO 527 save for the test specimen used which has the following dimensions which deviate from the specification: total length: 50 mm, width of narrow part: 3.3 mm, width at ends: 7 mm, length of narrow parallel part: 25 mm, thickness: 1 mm.

5. The thermoplastic molding material as claimed in claim 1, wherein said material contains 2% by weight to 98% by weight, preferably 30% by weight to 95% by weight, particularly preferably 40% by weight to 90% by weight, based on the total weight of the thermoplastic molding material, of the component A and 2% by weight to 98% by weight, preferably 5% by weight to 70% by weight, preferably 10% by weight to 60% by weight, based on the total weight of the thermoplastic molding material, of the component B.

6. The thermoplastic molding material as claimed in claim 1, wherein component B is an elastomeric, semicrystalline C.sub.3/C.sub.2-copolymer having a proportion of propylene greater than 80% by weight.

7. The thermoplastic molding material as claimed in claim 1, wherein component A is a random copolymer of propylene derived from 70% to 95% by weight of propylene and from 5% to 30% by weight of ethylene.

8. The thermoplastic molding material as claimed in claim 1, wherein the component B has a melting enthalpy measured according to ISO 11357-2 of 0 to 50 J/g, preferably of 1 to 30 J/g, particularly preferably of 2 to 20 J/g.

9. The thermoplastic molding material as claimed in claim 1, wherein the component A has a weight-average molecular weight according to ISO 16014 of 1000 to 50 000 g/mol, preferably 5000 to 30 000 g/mol, and component B has a weight-average molecular weight according to ISO 16014 of 50 000 to 300 000 g/mol, preferably 70 000 to 150 000 g/mol.

10. The thermoplastic molding material as claimed in claim 1, wherein the component A has a melt viscosity at 170° C. measured according to DIN 53019 of 10 to 10 000 mPas, preferably 100 to 5000 mPas, and component B has a melt index at 190° C./2.16 kg measured according to ASTM D1238 of between 1 g/10 min and 50 g/10 min, preferably between 1 g/10 min and 30 g/10 min.

11. The thermoplastic molding material as claimed in claim 1, wherein component A has a breaking elongation less than 1000% measured according to ISO 527 save for the test specimen used and component B has a breaking elongation greater than 1000% measured according to ISO 527 save for the test specimen used which has the following dimensions: total length: 50 mm, width of narrow part: 3.3 mm, width at ends: 7 mm, length of narrow parallel part: 25 mm, thickness: 1 mm.

12. A hot melt adhesive containing a thermoplastic molding material as claimed in claim 1.

13. The hot melt adhesive as claimed in claim 12, wherein said adhesive contains no tackifiers or plasticizers.

14. The hot melt adhesive as claimed in claim 12, wherein said adhesive contains organic or inorganic pigments, fillers, flame retardants, stabilizers, antistats, antioxidants and light stabilizers.

15. A process for producing a thermoplastic molding material as claimed in claim 1 by mixing the components A and B.

16. The use of the thermoplastic molding material as claimed in claim 1 for bonding or affixing substrates.

17. The use of the thermoplastic molding material as claimed in claim 16, wherein the bonding is an affixing of fillers or granular or pulverulent materials on structured or textile substrates.

18. The use of the hot melt adhesive as claimed in claim 12 for bonding or affixing substrates.

19. The use of the hot melt adhesive as claimed in claim 18, wherein the bonding is an affixing of fillers or granular or pulverulent materials on structured or textile substrates.

Description

[0071] FIG. 1: Schematic representation of the test specimen used in determining breaking elongation

[0072] FIG. 2: Schematic representation of the static peel test.

EXAMPLES

[0073] To produce the molding materials according to the invention polymers 1 and 2 were used as component A and polymers 3 and 4 were used as a component B. The components A and B are each characterized in more detail in tables 1 and 2.

TABLE-US-00001 TABLE 1 Component A Polyolefin A1 Polyolefin A2 Melt viscosity @ 170° C. [mPas] 200 2200 (DIN 53019) Weight-average molecular weight 8700 17800 M.sub.w [g/mol] (ISO 16014) PDI (ISO 16014) 1.5 2.1 Glass transition temperature T.sub.G [° C.] −30 −25 (DIN EN ISO 11357-2:2016) Density (ISO 1183) [g/cm.sup.3] 0.87 0.884 Melting point T.sub.m [° C.] 77 95 (DIN EN ISO 11357-1:2016) Heat of melting ΔH.sub.m [J/g] 36 37 (DIN EN ISO 11357-1:2016) Breaking elongation [%] (ISO 527) 10 600 Strength [MPa] (ISO 527) 2 9.0

[0074] The components from table 1 are commercial copolymers obtainable under the trade names Licocene® 1302 and Licocene® 2502.

TABLE-US-00002 TABLE 2 Component B Polyolefin B1 Polyolefin B2 MI [g/10 min] (190° C./2.15 21 8 kg, ASTM D1238) Weight-average molecular 80300 128400 weight M.sub.w [g/mol] (ISO 16014) PDI (ISO 16014) 2.5 2.5 Melting point T.sub.m [° C.] 95 60 (DIN EN ISO 11357-1:2016) Heat of melting ΔH.sub.m [J/g] 12 17.7 (DIN EN ISO 11357-1:2016) Breaking elongation [%] 1356 1100 (ISO 527) Strength [MPa] (ISO 527) 17.7 29.5

[0075] The components from table 2 are commercial copolymers obtainable under the trade names Vistamaxx®3000 and Vistamaxx®6502.

[0076] The polyolefins described in tables 1 and 2 were produced by melt extrusion as melt mixtures of the components. This was achieved using a co-rotating twin-screw extruder at a speed of 130 rpm and a processing temperature of 180° C. The extrusion throughput was 7 kg/h.

[0077] The comparative examples show prior art mixtures which employ in addition to a poly-alpha-olefin a SEBS block copolymer Kraton® MD 1648 or else a resin as a further component.

[0078] The following properties were determined from the hot melt adhesive compositions thus produced: [0079] melt viscosity at 170° C., [0080] tensile strength in MPa, [0081] breaking elongation in [%].

[0082] Thermoplastic molding materials/hot melt adhesives were also tested for their suitability for the intended use: To this end two flexible substrates having dimensions of 5 cm×30 cm were coated by spray application with the hot melt adhesive composition and bonded to one another. An application weight between 3 to 5 g/m.sup.2 was sought. To the extent that the tested thermoplastic molding materials/hot melt adhesives were sprayable the static peel test described hereinbelow was performed:

[0083] The bonded article formed (test specimen) was tested to determine delamination resistance by subjecting a test specimen to a static peel test at room temperature. This comprises delaminating the test specimen on a narrow side to form two flaps to which the substrates may be secured (see FIG. 2). One of these so-called tabs is secured to a holder while a weight of 100 g is secured to the other tab.

[0084] Measurement commences with release of the weight in the pulling direction (3) to delaminate an adherend (1) at a peel angle of 180° from the other substrate (2). The elapsed time from release of the weight until complete delamination is then recorded. The test is repeated 5 times and the average time is the parameter recorded. The longer the elapsed time the better the delamination resistance. In the case of a non-woven as the substrate an average elapsed time of more than 250 seconds may be regarded as a good result. This is a comparative test, the result of which can vary greatly depending on the nature of the substrates.

TABLE-US-00003 TABLE 3 Working examples (inventive)/(employed amounts in % by weight) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Polyolefin A1 50 23 20 Polyolefin A2 50 70 58 50 85 95 Polyolefin B1 50 30 50 19 5 Polyolefin (IIb) B2 30 15 Melt 23638 12535 10425 6314 7470 9230 3025 viscosity@170° C. [mPa .Math. s] Tensile strength 12.3 11.0 8.8 9.3 8.3 11.2 9.8 [N/mm.sup.2] Breaking 1470 1250 1497 1290 1210 1298 1091 elongation [%] static peel hang-time >300 >300 >300 >300 >300 >300 >300 test (sec)

TABLE-US-00004 TABLE 4 Comparative examples (noninventive)/(employed amounts in % by weight) C1 C2 C3 C4 C5 Polyolefin A1 60 8 Polyolefin A2 50 60 32 Polyolefin B2 20 Kraton MD 1648 50 40 40 40 100 Viscosity @ 170° C. [mPa .Math. s] 70000 12000 13250 32900 400000 Strength [N/mm.sup.2] 6.05 1.7 6.6 3.2 8.1 Breaking elongation [%] 815 344 850 426 673 static peel hang-time test (sec) Not 40 sec 90 sec Not Not usable usable usable since not since not since not sprayable sprayable sprayable

[0085] Kraton® MD 1648 from table 4 is a styrene block copolymer (SEBS) from Kraton.

[0086] The inventive examples show markedly better values compared to the comparative examples in the static peel test to the extent that the hot melt adhesive formulation was sprayable. While having good mechanical properties, comparative formulations that are not sprayable were not able to achieve the object of the invention of better processability. Only the inventive examples simultaneously exhibit sufficient viscosity, strength and breaking elongation to be suitable for realizing fiber web spraying applications. The comparative formulations fail in terms of at least one of the properties mentioned (viscosity, strength, breaking strength) and are thus unsuitable for use for fiber web applications.