Mono- and Multi-Layer Blown Films

Abstract

An extruded air cooled blown film having a) a total thickness of 5 to 500 m, b) a mono-layer structure or 2 to 9 coextruded layers, c) at least one layer L containing a polymer selected from the group consisting of polypropylene homopolymers, polypropylene random copolymers, hetero-phasic polypropylene block copolymers, or any mixtures thereof, said polymer having a melt flow rate, according to ASTM D-1238, of 0.1 to 10 dg/min at 230 C. and 2.16 kg, said layer L further containing 0.001 to 2%, relative to the weight of the polymer, of a particular nucleating agent, and optionally d) a Modulus according to EN ISO 527 enhanced by at least 10% versus a reference film without the nucleating agent.

Claims

1.-34. (canceled)

35. An extruded air cooled blown film having a) a total thickness of 5 to 500 m, b) a mono-layer structure or 2 to 9 coextruded layers, c) at least one layer L containing a polymer selected from the group consisting of polypropylene homopolymers, polypropylene random copolymers, hetero-phasic polypropylene block copolymers, or any mixtures thereof, said polymer having a melt flow rate, according to ASTM D-1238, of 0.1 to 10 dg/min at 230 C. and 2.16 kg, said layer L further containing 0.001 to 2%, relative to the weight of the polymer, of a nucleating agent of formula (IA), (TB) or (IC), ##STR00016## wherein x and y are an integer from 2 to 6; z and z independently of one another are an integer from 1 to 5 with the proviso that the sum of z and z is an integer from 2 to 6; X.sub.0 is a residue which is formed by elimination of x carboxyl groups of a saturated or unsaturated aliphatic polycarboxylic acid having 3 to 25 carbon atoms, a residue which is formed by elimination of x carboxyl groups of a saturated or unsaturated alicyclic polycarboxylic acid having 7 to 25 carbon atoms or a residue which is formed by elimination of x carboxyl groups of an aromatic polycarboxylic acid having 8 to 25 carbon atoms; any of said polycarboxylic acids optionally contains further hetero atoms in its skeleton; the radicals X.sub.1 independently of one another are C.sub.1-C.sub.20alkyl unsubstituted or substituted by one or more hydroxy, amino and/or nitro groups; C.sub.2-C.sub.20alkenyl unsubstituted or substituted by one or more hydroxy, amino and/or nitro groups; C.sub.2-C.sub.20alkyl interrupted by oxygen or sulfur; C.sub.3-C.sub.12cycloalkyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; (C.sub.3-C.sub.12cycloalkyl)-C.sub.1-C.sub.10alkyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; bis[C.sub.3-C.sub.12cycloalkyl]-C.sub.1-C.sub.10alkyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; a bicyclic or tricyclic hydrocarbon radical with 5 to 20 carbon atoms unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; phenyl unsubstituted or substituted by one or more radicals selected from C.sub.1-C.sub.20alkyl, C.sub.1-C.sub.20alkoxy, C.sub.1-C.sub.20alkylamino, di(C.sub.1-C.sub.20alkyl)amino, amino, hydroxy and nitro; phenyl-C.sub.1-C.sub.20alkyl unsubstituted or substituted by one or more radicals selected from C.sub.1-C.sub.20alkyl, C.sub.3-C.sub.12cycloalkyl, phenyl, C.sub.1-C.sub.20alkoxy, amino, hydroxy and nitro; phenylethenyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; biphenyl-(C.sub.1-C.sub.10alkyl) unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; naphthyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; naphthyl-C.sub.1-C.sub.20alkyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; naphthoxymethyl unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; biphenylenyl, fluorenyl, anthryl; a 5- to 6-membered heterocyclic radical unsubstituted or substituted by one or more C.sub.1-C.sub.20alkyl; a C.sub.1-C.sub.20hydrocarbon radical containing one or more halogen or pseudo-halogen; tri(C.sub.1-C.sub.10alkyl)silyl; or tri(C.sub.1-C.sub.10alkyl)silyl(C.sub.1-C.sub.10alkyl); Y.sub.0 is a residue which is formed by elimination of y amino groups of a saturated or unsaturated aliphatic polyamine having 3 to 25 carbon atoms, a residue which is formed by elimination of y amino groups of a saturated or unsaturated alicyclic polyamine having 6 to 25 carbon atoms or a residue which is formed by elimination of y amino groups of an aromatic polyamine having 6 to 25 carbon atoms; any of said polyamines optionally contains further hetero atoms in its skeleton; the radicals Y.sub.1 independently of one another have one of the definitions of X.sub.1; Z.sub.0 is a residue which is formed by elimination of z amino groups and z carboxyl groups of an unsaturated or saturated aliphatic amino carboxylic acid having 2 to 25 carbon atoms, a residue which is formed by elimination of z amino groups and z carboxyl groups of a saturated or unsaturated alicyclic amino carboxylic acid having 7 to 25 carbon atoms or a residue which is formed by elimination of z amino groups and z carboxyl groups of an aromatic amino carboxylic acid having 7 to 25 carbon atoms; any of said amino carboxylic acids optionally contains further hetero atoms in its skeleton; and the radicals Z.sub.1 and Z.sub.2 independently of one another have one of the definitions given for X.sub.1.

36. The extruded air cooled blown film according to claim 35, having d) a Modulus according to EN ISO 527 enhanced by at least 10% versus a reference film without a nucleating agent of the formula (IA), (IB), or (IC).

37. The extruded air cooled blown film according to claim 35, comprising 20 to 100% by weight, relative to its total weight, of a polypropylene homopolymer or copolymer.

38. The extruded air cooled blown film according to claim 35, wherein layer L contains a polypropylene homopolymer, random copolymer, alternating or segmented copolymer, a block copolymer or a blend of polypropylene with another synthetic polymer.

39. The extruded air cooled blown film according to claim 35, wherein the layer L contains a propylene copolymer with ethylene at an ethylene content of 0.5 to 15% by weight, relative to the total weight of the propylene copolymer.

40. The extruded air cooled blown film according to claim 35, wherein the polypropylene homopolymer or copolymer has a melt flow rate of 0.3 to 5 dg/min at 230 C. and 2.16 kg according to ASTM D1238.

41. The extruded air cooled blown film according to claim 35, wherein the film structure contains at least one coextruded layer of low-, linear-low- or high-density polyethylene (LDPE, LLDPE, HDPE) or metallocene polyethylene, adjacent to the layer of polypropylene.

42. The extruded air cooled blown film according to claim 35, consisting of 3 coextruded layers, the layer L is the inner layer and two layers S1 and S2 are the outer layers, the layers 51 and S2 contain at least 50% of low-, linear-low- or high-density polyethylene (LDPE, LLDPE, HDPE) or metallocene polyethylene (m-PE) or any mixture thereof.

43. The extruded air cooled blown film according to claim 35, wherein one or more layers contain ethylene vinyl alcohol copolymer (EVOH), ethylene vinyl acetate copolymer (EVA), maleic anhydride grafted polypropylene or polyethylene, copolymers of acrylic-acid esters with propylene or ethylene, acrylic acid copolymers with propylene or ethylene, polyvinylidene chloride (PVDC), polyamide, or polyester.

44. The extruded air cooled blown film according to claim 35, which contains additionally one or more adhesive layer.

45. The extruded air cooled blown film according to claim 35, having a Modulus according to EN ISO 527 enhanced in longitudinal direction by at least 10% versus a reference film without a nucleating agent of the formula (IA), (IB), or (IC).

46. The extruded air cooled blown film according to claim 35, having a Modulus according to EN ISO 527 enhanced in transversal direction by at least 10% versus a reference film without a nucleating agent of the formula (IA), (IB), or (IC).

47. The extruded air cooled blown film according to claim 35, having a Haze value according to ASTM D-1003 reduced by at least 10% relative to a reference film without a nucleating agent of the formula (IA), (IB), or (IC).

48. The extruded air cooled blown film according to claim 35, having a Clarity value according to ASTM D-1746 enhanced by at least 0.5% relative to a reference film without a nucleating agent of the formula (IA), (IB), or (IC).

49. The extruded air cooled blown film according to claim 35, having a Haze value according to ASTM D-1003 reduced by at least 10% relative to a reference film without a nucleating agent of the formula (IA), (TB), or (IC), and a Clarity value according to ASTM D-1746 enhanced by at least 0.5% relative to a reference film without a nucleating agent of the formula (IA), (TB), or (IC).

50. The extruded air cooled blown film according to claim 35, comprising one or more additives selected from the group consisting of 1) an anti-agglomerant, 2) an antioxidant, 3) an antistatic agent, 4) a slip- and anti-blocking agent, 5) an anti-fogging agent, and 6) a light stabilizer.

51. The extruded air cooled blown film according to claim 35, wherein the layer L additionally contains one or more anti-agglomerants.

52. The extruded air cooled blown film according to claim 35, wherein x, y or the sum of z and z are 2 or 3, and when x, y or the sum of z and z are 2, X.sub.0, Y.sub.0, and Z.sub.0 are the group of formula ##STR00017## and when x, y or the sum of z and z are 3, X.sub.0, Y.sub.0, and Z.sub.0 are the group of formula ##STR00018##

53. The extruded air cooled blown film according to claim 35, wherein the radicals X.sub.1, Y.sub.1, Z.sub.1 and Z.sub.2 independently of one another are C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 hydroxy, amino and/or nitro; C.sub.2-C.sub.20alkenyl unsubstituted or substituted by 1, 2 or 3 hydroxy, amino and/or nitro; C.sub.2-C.sub.10alkyl interrupted by oxygen; C.sub.3-C.sub.6cycloalkyl unsubstituted or substituted by 1, 2, 3 or 4 C.sub.1-C.sub.4alkyl; (C.sub.3-C.sub.6cycloalkyl)-C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; bis[C.sub.3-C.sub.6cycloalkyl]-C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; ##STR00019## phenyl unsubstituted or substituted by 1, 2 or 3 radicals selected from C.sub.1-C.sub.4alkyl, C.sub.1-C.sub.4alkoxy, C.sub.1-C.sub.4alkylamino, di(C.sub.1-C.sub.4alkyl)amino, amino, hydroxy and nitro; phenyl-C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 radicals selected from C.sub.1-C.sub.4alkyl, C.sub.3-C.sub.6cycloalkyl, phenyl, C.sub.1-C.sub.4alkoxy, hydroxy, amino and nitro; phenylethenyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; biphenyl-(C.sub.1-C.sub.10alkyl) unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; naphthyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; naphthyl-C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; naphthoxymethyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; biphenylenyl, fluorenyl, anthryl; 3-pyridinyl, 4-pyridinyl, 2-hydroxypyridin-3-yl, 3-quinolinyl, 4-quinolinyl, 2-furyl, 3-furyl, 1-methyl-2-pyrryl; 1-bromo-2-methylpropyl, dichloromethyl, pentafluoroethyl, 3,5-bis[trifluoromethyl]phenyl, 2,3,5,6-tetrafluoro-p-tolyl, 2,3-dichlorophenyl, 3,4-dichlorophenyl or 2,4-bis[trifluoromethyl]phenyl; tri(C.sub.1-C.sub.10alkyl)silyl; or tri(C.sub.1-C.sub.10alkyl)silyl(C.sub.1-C.sub.10alkyl).

54. The extruded air cooled blown film according to claim 35, wherein the radicals X.sub.1, Y.sub.1, Z.sub.1 and Z.sub.2 independently of one another are branched C.sub.3-C.sub.10alkyl; C.sub.3-C.sub.10alkyl interrupted by oxygen; C.sub.3-C.sub.6cycloalkyl unsubstituted or substituted by 1, 2, 3 or 4 C.sub.1-C.sub.4alkyl; (C.sub.3-C.sub.6cycloalkyl)-C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; ##STR00020## phenyl unsubstituted or substituted by 1, 2 or 3 C.sub.1-C.sub.4alkyl; phenyl-C.sub.1-C.sub.10alkyl unsubstituted or substituted by 1, 2 or 3 radicals selected from C.sub.1-C.sub.4alkyl and C.sub.1-C.sub.4alkoxy; biphenyl-(C.sub.1-C.sub.10alkyl); naphthyl-C.sub.1-C.sub.10alkyl; tri(C.sub.1-C.sub.10alkyl)silyl; or tri(C.sub.1-C.sub.4alkyl)silyl(C.sub.1-C.sub.5alkyl).

55. The extruded air cooled blown film according to claim 35, wherein the nucleating agent is a compound of the formula (IA), x is 2 or 3, when x is 2, X.sub.0 is the group of the formula ##STR00021## and when x is 3, X.sub.0 is the group of the formula ##STR00022## and the radicals X.sub.1 independently of one another are n-propyl, i-propyl, n-butyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 2-ethylbutyl, 2-ethylhexyl, 5-ethylhexyl, n-octyl, 1,1,3,3-tetramethylbutyl, 2,2,4-trimethylpentyl, 3,7-dimethyloctyl, cyclobutyl, cyclopentyl, cyclohexyl, 2-methyl-cyclohexyl, 3-methyl-cyclohexyl, 4-methyl-cyclohexyl, 2,3-dimethyl-cyclohexyl, 3,3,5-trimethyl-cyclohexyl, 1-cyclohexyl-ethyl, cycloheptyl, cyclooctyl, cyclododecyl, phenyl, benzyl, 1-phenylethyl, 2-phenylethyl, cumyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2,3-dimethylphenyl, 3,5-dimethylphenyl, 2,3,5-trimethylphenyl, 2,4,6-trimethylphenyl, 4-n-butylphenyl, 4-tert-butylphenyl, 4-methoxyphenyl.

56. The extruded air cooled blown film according to claim 35, wherein the nucleating agent is a compound of the formula (TB), y is 2 or 3, when y is 2, Y.sub.0 is the group of formula ##STR00023## and when y is 3, Y.sub.0 is the group of formula ##STR00024## and the radicals Y.sub.1 independently of one another are n-propyl, i-propyl, n-butyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 2-ethylbutyl, 2-ethylhexyl, 5-ethylhexyl, n-octyl, 1,1,3,3-tetramethylbutyl, 2,2,4-trimethylpentyl, 3,7-dimethyloctyl, cyclobutyl, cyclopentyl, cyclohexyl, 2-methyl-cyclohexyl, 3-methyl-cyclohexyl, 4-methyl-cyclohexyl, 2,3-dimethyl-cyclohexyl, 3,3,5-trimethyl-cyclohexyl, 1-cyclohexyl-ethyl, cycloheptyl, cyclooctyl, cyclododecyl, phenyl, benzyl, 1-phenylethyl, 2-phenylethyl, cumyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2,3-dimethylphenyl, 3,5-dimethylphenyl, 2,3,5-trimethylphenyl, 2,4,6-trimethylphenyl, 4-n-butylphenyl, 4-tert-butylphenyl, 4-methoxyphenyl.

57. The extruded air cooled blown film according to claim 35, wherein the nucleating agent is a compound of the formula (IC), z and z independently of one another are 1 or 2, and when the sum of z and z is 2, Z.sub.0 is the group of formula ##STR00025## and when the sum of z and z is 3, Z.sub.0 is the group of formula ##STR00026## and the radicals Z.sub.1 and Z.sub.2 independently of one another are n-propyl, i-propyl, n-butyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 2-ethylbutyl, 2-ethylhexyl, 5-ethylhexyl, n-octyl, 1,1,3,3-tetramethylbutyl, 2,2,4-trimethylpentyl, 3,7-dimethyloctyl, cyclobutyl, cyclopentyl, cyclohexyl, 2-methyl-cyclohexyl, 3-methyl-cyclohexyl, 4-methyl-cyclohexyl, 2,3-dimethyl-cyclohexyl, 3,3,5-trimethyl-cyclohexyl, 1-cyclohexyl-ethyl, cycloheptyl, cyclooctyl, cyclododecyl, phenyl, benzyl, 1-phenylethyl, 2-phenylethyl, cumyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2,3-dimethylphenyl, 3,5-dimethylphenyl, 2,3,5-trimethylphenyl, 2,4,6-trimethylphenyl, 4-n-butylphenyl, 4-tert-butylphenyl, 4-methoxyphenyl.

58. The extruded air cooled blown film according to claim 35, wherein the nucleating agent is a compound of the formula (IA) wherein x is 3, X.sub.0 is the group of the formula ##STR00027## and the radicals X.sub.1 are tert-octyl.

59. The extruded air cooled blown film according to claim 35, wherein the nucleating agent is a compound of the formula (TB) wherein y is 3, Y.sub.0 is the group of the formula ##STR00028## and the radicals Y.sub.1 are tert-butyl.

Description

EXAMPLE 1

Preparation of Masterbatch MB-1 Utilized for Film Production

[0262] The following powdery components are intimately pre-blended during five minutes at ambient temperature in a high-speed Henschel (RTM) mixer:

525 g of 1,3,5-tris[2,2-dimethylpropionylamino]benzene as the nucleating agent,
700 g of glycerol mono-stearate as first anti-agglomerant,
350 g of calcium stearate as second anti-agglomerant,
58 g of pentaerythryl-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate as primary antioxidant, and
117 g of tris(2,4-di-tert-butylphenyl) phosphite as secondary antioxidant.

[0263] The obtained pre-blend of above is then continuously added via a screw feeder (Brabender (RTM), DE) into the main feed of granular polypropylene RB-501 BF (commercial polypropylene random copolymer of Borealis (RTM)). Both feeds are then continuously combined in the hopper of a Theysohn (RTM) twin-screw extruder (30 mm44 D), operated under high-shear conditions and increasing temperature profile (feed-mixing-die) of 210 C.-240 C.-255 C. The feeds of both materials are adjusted to 2.5% let-down ratio of the additives. The melt is then extruded through a 23.2 mm twin-die to form stands, which are water-chilled, dried and eventually cut into the granular form of the masterbatch. The actual concentration of the nucleating agent in the final masterbatch is verified by analytical control to be 0.70%.

[0264] This masterbatch MB-1 is used for the addition of 200 ppm of the nucleating agent to the polypropylene type PP-1 in Examples 3 to 8, i.e. the MB-1 carrier resin is identical with PP-1.

[0265] Careful formulation and sufficient homogenization of the aforementioned components is imperative to ensure good quality of the masterbatch. Inadequate preparation will result in reduced performance during further processing and cause severe problems with formation of film structure and surface defects, like for example streaks or so-called fish-eyes.

EXAMPLE 2

Preparation of a Masterbatch MB-2 Utilized During Film Production

[0266] The procedure described in Example 1 is repeated, but substituting the random copolymer of above with the polypropylene homopolymer Moplen HP-522 H (RTM) (commercially available from Basell (RTM)).

[0267] The final masterbatch is verified by analysis to contain 0.73% of the nucleating agent. This masterbatch MB-2 is used for the addition of 200 ppm of the nucleating agent to the polypropylene type PP-2 in Examples 3 to 8, i.e. the MB-2 carrier resin is identical with PP-2.

EXAMPLES 3 TO 8

Manufacture of Extruded Air Cooled Blown Films

[0268] The examples relate to the manufacture of films on an industrial blown film line, set-up as multi-purpose line for the production of air-cooled films. This line allows production of films up to three layers. The circular die of 25 cm diameter (2.8 mm die gap) can be fed by three independent single screw extruders: Main feeder 90 mm25 D, each side feeder 60 mm25 D. The temperatures along the extruder barrels are stepwise increased to achieve a gradient of about 15-20 C.; melt temperatures are kept +/5 C. constant between extruder exit and the die as listed in the Table 1, column Melt Temp..

[0269] Total throughput is varied between 230-250 kg/h, corresponding to specific throughputs of 9.2 to 10 kg/h per cm of die diameter, but kept constant in the course of one trial. The flow and feeding characteristics of the polymer melts are monitored online. The results are listed in Table 1 in g/h/rpm. This unit signifies the quantity of polymer transported per hour at constant revolutions of the extruder screw. Thus, higher values of g/h/rpm comply with less energy at constant throughput, respectively allowing higher throughput at constant revolutions per minute (rpm) of the extruder screw.

EXAMPLES 9 TO 11

[0270] Three-layer coextruded air cooled blown films are prepared with a Collin (RTM) lab scale multilayer extruder equipped with circular die of 80 mm diameter, gap 0.8 mm, main extruder 25 mm25 D and side extruder 20 mm25 D.

[0271] In examples 9 and 10 a mixture of polymer PP-1 and MB-1 is prepared so that the final amount of clarifier in each layer of the final plastic article is 100 ppm; this mixture is used to feed the different extruders for the film manufacturing process.

[0272] The following polymers (all being commercial grades) are used as received for the manufacture of the blown films described in Tables 1 and 2: [0273] PP-1=Polypropylene random copolymer (RB-501 BF of Borealis (RTM)), melt flow rate: 1.9 dg/min at 230 C. and 2.16 kg; [0274] PP-2=Polypropylene homopolymer (Moplen HP-522 H (RTM) of Basell (RTM)), melt flow rate: 2.0 dg/min at 230 C. and 2.16 kg; [0275] PP-1*=blend composed of 97.1% of PP-1 pellets and 2.9% of granular MB-1; [0276] PP-2*=blend composed of 97.2% of PP-2 pellets and 2.8% of granular MB-2; [0277] PP-3*==blend composed of 98.6% of PP-1 pellets and 1.4% of granular MB-1 [0278] PE-1=metallocene polyethylene (Exceed 1018 EB (RTM) of ExxonMobil (RTM), melt flow rate: 1.0 dg/min at 190 C. and 2.16 kg; [0279] PE-2=low density polyethylene (Lupolen 2420 F (RTM) of Basell (RTM), melt flow rate: 0.75 dg/min at 2.16 kg and 190 C.; [0280] PE-3=pellet blend composed of 80% of PE-1 with 20% of PE-2.

[0281] The addition of the nucleating agents is continuously performed by online dosing of the granular masterbatches MB-1 or MB-2, as indicated above, at suitable let-down ratios (i.e. percentage of (masterbatch (MB) admixture to the polymer main feed). The resulting mixture of pellets is constantly processed and sheared in one or more of the extruders as commented above, eventually resulting in homogeneous polymer melts feeding the circular blowing die. The flow of materials is constantly controlled and adjusted in such a way, thatin case of nucleated filmsthe final concentration of the nucleating agent is always 200 ppm and kept constant in the course of each trial. Further data on the processing conditions and compositions of the films are given in Table 1. Table 2 shows the testing results obtainable from the film samples.

The Designations and Data Summarized in Table 1 have the Following Significance:

[0282] Layers and Thick. refer to the composition by layer of the blown films and their thicknesses.

[0283] M. Temp. gives the temperature of the polymer melt having exited the extruder and passing the die entrance, from where it is kept unchanged towards the die exit (die gap).

[0284] g/h/rpm signifies the grams of polymer transported within one hour per one revolution of the extruder screw, i.e. a measure of the flow- and feeding characteristics of the polymer.

[0285] D.D.R. signifies the longitudinal draw down ratio of the film, i.e. the ratio of the eventual pull-off speed of the film relative to the speed of the melt passing the die gap.

[0286] B.U.R. signifies the blow-up ratio of the film given by the diameter of the tubular film pulled-off relative to the diameter of the die forming the tubular film cylinder.

[0287] Bubble Stab. signifies the visible stability of the film bubble during the blowing process; irregularities are often audible, too, as stronger sough or noise in the die exit proximity.

TABLE-US-00001 TABLE 1 Conditions for the Manufacture of Extruded Air Cooled Blown Films. Bubble Example Layers Thickn. M. Temp. g/h/rpm D.D.R. B.U.R. Stab. No. 3 S1: PE-3 6 m 205 C. 2726 15.3 3.7 excellent Invention L: PP-1* 38 m 231 C. (+5.9% S2: PE-3 6 m 201 C. versus No. 4) No. 4 S1: PE-3 6 m 205 C. 2573 15.3 3.7 moderate Reference L: PP-1 38 m 231 C. S2: PE-3 6 m 201 C. No. 5 S1: PP-1* 18 m 227 C. 2894 14.1 3.7 excellent Invention L: PP-1* 18 m 225 C. (+6.6% S2: PP-1* 18 m 222 C. versus No. 6) No. 6 S1: PP-1 18 m 227 C. 2716 14.0 3.8 fair to Reference L: PP-1 18 m 225 C. poor S2: PP-1 18 m 222 C. No. 7 S1: PE-3 6 m 226 C. 2857 20.8 3.7 excellent Invention L: PP-2* 24 m 233 C. (+4.1% S2: PE-3 6 m 217 C. versus No. 8) No. 8 S1: PE-3 6 m 227 C. 2744 20.4 3.8 fair to Reference L: PP-2 24 m 232 C. poor S2: PE-3 6 m 218 C. No. 9 S1: PP-3* 10 m 230 C. 5.2 2.5 excellent Invention L: PP-3* 10 m 232 C. S2: PP-3* 10 m 229 C. No. 10 S1: PP-3* 17 m 233 C. 5.1 2.5 excellent Invention L: PP-3* 17 m 229 C. S2: PP-3* 17 m 233 C. N0. 11 S1: PP-1 17 m 230 C. 4.3 2.5 fair to Reference L: PP-1 17 m 229 C. poor S2: PP-1 17 m 229 C.

[0288] Blown films according to the present invention are the above Examples 3, 5, 7, 9 and 10; Examples 4, 6, 8 and 11 represent comparative films only for reference purposes. The film structures are indicated by designation of the layers signifying S1 and S2 as skin or outer layers; layer L as core or inner layer. Pseudo-monolayer films have identical composition of all layers, as in case of Examples 5, 6, 9 and 10.

The Designations and Data Summarized in Table 2 have the Following Significance:

[0289] T. Thick. refers to the final thickness of the films actually measured during testing.

[0290] Haze determined according to ASTM D-1003 is measured for each blown film; reductions given as negative percentage indicate the improvements achieved with the inventive samples versus the respective references.

[0291] Clarity is determined according to ASTM D-1746. Improvements are given as positive percentage versus the respective reference film.

[0292] Mod.-MD determined according to EN ISO 527 signifies the Modulus in longitudinal or machine direction, in which the film was blown; percentages of improvements are given versus the respective reference samples.

[0293] Mod.-TD complies with Mod.-MD of above, however, referring to the Modulus determined in transversal or cross-machine direction.

[0294] E.a.B.-MD determined according to EN ISO 527 signifies the elongation at break of a sample taken from longitudinal or machine direction of the blown film; percentages of improvements are given versus the respective reference samples.

[0295] E.a.B.-TD complies with E.a.B.-MD of above, however, referring to the elongation at break determined in transversal or cross-machine direction.

TABLE-US-00002 TABLE 2 Physical Properties of the Extruded Air Cooled Blown Films. T. Example Thick. Haze Clarity Mod.-MD Mod.-TD E.a.B.-MD E.a.B.-TD No. 3 51 m 5.2% 98.10% 268 MPa 603 MPa 534% 687% Invention (16% of (+0.8% of (+16.2% of (+22.0% of No. 4) (+2.4% of (+4.5% of No. 4) No. 4) No. 4) No. 4) No. 4) No. 4 51 m 6.2% 97.34 230 MPa 494 MPa 522% 657% Reference No. 5 54 m 7.0% 94.96% 418 MPa 859 MPa 517% 735% Invention (64% of (+5.2% of (+11.3% of (+16.1% of No. 6) (+3.0% of (+6.5% of No. 6) No. 6) No. 6) No. 6) No. 6) No. 6 53 m 19.4% 90.28% 376 MPa 740 MPa 502% 690% Reference No. 7 35 m 4.8% 98.22% 360 MPa 937 MPa 601% 677% Invention (43% of (+7.9% of (+19.8% of (+21.8% of No. 8) (+9.7% of (+2.0% of No. 8) No. 8) No. 8) No. 8) No. 8) No. 8 34 m 8.4% 91.02% 301 MPa 769 MPa 457% 663% Reference No. 9 31 m 3.1% 99.68% Invention No. 10 50 m 3.8% 99.46% Invention (75% of (+11.7% of No. 11) No. 11) No. 11 52 m 15% 89% Reference

[0296] The data given in the Tables 1 and 2 of above are intended only for the purpose of illustration of the present invention, and are not to be construed to mean any limitation of the scope or of the general applicability of the present invention. Although being self-explanatory by the various improvements achieved, the inventive examples should be understood as follows:

[0297] Examples 3 to 6 are based on the use of PP-1 as principal component of the film. The processing stability, in particular the bubble stability of this random copolymer is quite moderate, as outlined in the comparative Example 4. Certain improvements are possible by additional usage of metallocene-PE based skin layers, as outlined in the comparative Example 6. But by using the PE-3, the overall stiffness of the film is heavily affected, which is expressed in the comparatively low values of the Modulus in both, machine or longitudinal direction and cross- or transversal direction.

[0298] By usage of the nucleating agents according to the invention, these drawbacks are eliminated as outlined by Examples 3 and 5. The processing stability, in particular the bubble stability, during film blowing becomes excellent. In addition, higher specific throughput (given in g/h/rpm) is observed further enhancing the smoothness of the total film blowing process. Furthermore, the corresponding film properties given in Table 2 are self-explanatory with regard to the improvements achieved.

[0299] The measured values of the Moduli were found to be 11% to 22% higher in comparison to the reference films, which do not contain any nucleating agent. It is important here to note that the enhancements of the Moduli do not affect the elastic properties of the films (percentage of elongation at break); even slightly higher values have been found for the inventive films based on the random copolymer.

[0300] Also the aesthetic properties of the films, expressed by lower Haze and higher Clarity values, respectively, are clearly improved in the inventive formulations (Examples 3 and 5) relative to their corresponding reference films (Examples 4 and 6). Haze reduction by 16%, respectively 64% and Clarity enhancement of 0.8%, respectively 5.2% has been achieved by Example 3, respectively Example 5, relative to the corresponding reference films of Example 4, respectively Example 6. The clarified blown film described in Example 5 has remarkable properties. Being a pseudo-monolayer polypropylene film, it merges the benefits of optical, mechanical, easy-to-process and even recycling properties with an outstanding balance.

[0301] Examples 7 and 8 are based on the use of PP-2 as principal component of the film. It is known that the overall processibility of this polypropylene homopolymer alone is fairly poor in the blown film process. Even the use of PE-3 skin layers as done in Example 8 results only in marginally better bubble stability. The benefits of the inventive formulations are realized in Example 7. Complementing the excellent processibilities of these clarified polypropylene films, the use of polypropylene homopolymer allows to even further enhance their Moduli at maintained optical clarity, particularly in comparison the aforementioned blown films based on polypropylene random copolymers. Some further film properties given in Table 2 are self-explanatory with regard to the improvements achieved.

[0302] As can be seen from Example 7, it should be noted that the presence of PE-3 skin layers might be preferred, when the core layers are based on PP-2* (i.e. clarified polypropylene homopolymer). In this way, it is ensured to combine best optical properties and high moduli with constantly maintained elasticity in longitudinal and transversal direction of the film.

[0303] In Examples 9 and 10 concentration of the clarifier is down-gauged to half of the previous examples. In both examples the addition of the clarifier improves remarkably the processing stability as seen in the bubble stability comment. In addition to processing stability, aesthetic properties of these films are very much improved as compared to example 11, where no clarifier was used. Throughput is also increased by around 20%.

[0304] This consideration and selection may conclude a sensible balance of all properties to be taken into account in this particular case, although further improvements are obvious to those skilled in the art, based on these novel principal findings according to the invention.