SEALABLE MULTILAYER FILM OF STYRENE POLYMERS WITH IMPROVED ORGANOLEPTIC PROPERTIES

Abstract

A heat-sealable multilayer film comprising: a) 1% to 50% by weight of heat-sealable polymer layer (A), b) 1% to 99% by weight of polymer layer (C), and c) 0% to 95% by weight of polymer layer (B), with polymer layer (A) comprising: A1) 20% to 90% by weight of impact-resistant polystyrene and A2) 5% to 50% by weight of vinylaromatic-diene block copolymer; and polymer layer (B) comprising impact-resistant polystyrene, vinylaromatic-diene block copolymer, and/or mixtures of styrene homopolymers or vinylaromatic-diene graft copolymers with vinylaromatic-diene block copolymers; and polymer layer (C) having a melting temperature of ≥170° C.; and polymer layer (A) comprising) i) 66% to 99% by volume of a vinylaromatic hard phase and ii) 1% to 34% by volume of a diene soft phase surrounded by the hard phase and taking the form of spheres/cylinders.

Claims

1-18. (canceled)

19. A heat-sealable multilayer film comprising: a) 1 to 50 wt % of a heat-sealable polymer layer (A), b) 1 to 99 wt % of a polymer layer (C), and c) 0 to 95 wt % of a polymer layer (B), wherein, if present, the polymer layer (B) is between the heat-sealable polymer layer (A) and the polymer layer (C), and the proportions of a), b), and c) are each based on the total weight of the heat-sealable multilayer film; wherein the heat-sealable polymer layer (A) contains: A1) 20 to 90 wt %, based on the total weight of the heat-sealable polymer layer (A), of at least one impact-resistant polystyrene (A1); A2) 5 to 50 wt %, based on the total weight of the heat-sealable polymer layer (A), of at least one vinylaromatic-diene block copolymer (A2); A3) 0 to 30 wt %, based on the total weight of the heat-sealable polymer layer (A), of at least one glidant and/or lubricant (A3); and A4) 0 to 10 wt %, based on the total weight of the heat-sealable polymer layer (A), of auxiliaries and/or additives (A4) other than (A3); wherein the polymer layer (B) is different than the heat-sealable polymer layer (A) and the polymer layer (C); wherein the polymer layer (B) contains at least one component (B1) selected from the group consisting of: impact-resistant polystyrene, vinylaromatic-diene block copolymers, and mixtures of styrene homopolymers or vinylaromatic-diene graft copolymers with vinylaromatic-diene block copolymers; wherein the polymer layer (C) is different than the heat-sealable polymer layer (A) and the polymer layer (B); wherein the polymer layer (C) has a melting temperature of at least 170° C.; wherein the heat-sealable polymer layer (A) comprises: (i) 66 to 99 vol % of a hard phase, based on the total volume of the heat-sealable polymer layer (A), containing structural units of at least one vinylaromatic monomer; and (ii) 1 to 34 vol % of a soft phase, based on the total volume of the heat-sealable polymer layer (A), containing structural units of at least one conjugated diene; and wherein the soft phase (ii) is in the form of spheres and/or cylinders surrounded by the hard phase.

20. The heat-sealable multilayer film of claim 19, wherein the heat-sealable polymer layer (A) comprises: (i) 86 to 99 vol % of the hard phase containing structural units of the at least one vinylaromatic monomer; and (ii) 1 to 14 vol % of the soft phase containing structural units of the at least one conjugated diene.

21. The heat-sealable multilayer film of claim 19, wherein the soft phase (ii) is in the form of spheres and/or cylinders, and optionally, with a proportion of less than 50 vol %, of lamellas each having an average diameter of 20 to 200 nm.

22. The heat-sealable multilayer film of claim 19, wherein the heat-sealable polymer layer (A) is formed from: A1) 40 to 90 wt %, based on the total weight of the heat-sealable polymer layer (A), of the least one impact-resistant polystyrene (A1); A2) 10 to 40 wt %, based on the total weight of the heat-sealable polymer layer (A), of the least one vinylaromatic-diene block copolymer (A2); A3) 0 to 20 wt %, based on the total weight of the heat-sealable polymer layer (A), of the least one glidant and/or lubricant (A3); and A4) 0 to 5 wt %, based on the total weight of the heat-sealable polymer layer (A), of the additives and/or auxiliaries (A4).

23. The heat-sealable multilayer film of claim 19, wherein the vinylaromatic-diene block copolymer (A2) is formed from at least one block S, which forms a hard phase, containing structural units of at least one vinylaromatic monomer, and at least one block B and/or block B/S, which forms a soft phase, containing structural units of a conjugated diene and also, in the case of the B/S block, structural units of at least one vinylaromatic monomer.

24. The heat-sealable multilayer film of claim 23, wherein the vinylaromatic-diene block copolymer (A2) does not contain the B block and the B/S block is constructed randomly.

25. The heat-sealable multilayer film of claim 23, wherein the vinylaromatic-diene block copolymer (A2) contains at least two terminal blocks S and has a linear or star-shaped construction.

26. The heat-sealable multilayer film of claim 23, wherein the proportion of the soft phase of the vinylaromatic-diene block copolymer (A2) is 60 to 95 vol %, and the proportion of the hard phase of the vinylaromatic-diene block copolymer (A2) is 5 to 40 vol %.

27. The heat-sealable multilayer film of claim 23, wherein the copolymer block (B/S) of the vinylaromatic-diene block copolymer (A2) consists of 30 to 70 wt % of structural units of the at least one vinylaromatic monomer, and 30 to 70 wt % of structural units of the conjugated diene.

28. The heat-sealable multilayer film of claim 23, wherein the vinylaromatic-diene block copolymer (A2) includes 25 to 50 wt % of structural units of the conjugated diene, and 25 to 50 wt % of structural units of the at least one vinylaromatic monomer.

29. The heat-sealable multilayer film of claim 19 comprising: a) 3 to 30 wt % of the heat-sealable polymer layer (A); b) 50 to 90 wt % of the polymer layer (B); and c) 1 to 30 wt % of the polymer layer (C).

30. The heat-sealable multilayer film of claim 19, further comprising 1 to 10 wt %, based on the total weight of the heat-sealable multilayer film, of a further polymer layer (D), other than the heat-sealable polymer layer (A), the polymer layer (B), and the polymer layer (C), which is between the heat-sealable polymer layer (A) and the polymer layer (C), or the polymer layer (B) and the polymer layer (C).

31. The heat-sealable multilayer film of claim 30, wherein the polymer layer (D) contains at least one component (D1) selected from the group consisting of adhesion promoters, copolymers containing structural units of glycidyl (meth)acrylate, vinylaromatic-diene block copolymers, and gas barrier and/or water vapor barrier materials.

32. The heat-sealable multilayer film of claim 19, wherein the polymer layer (C) contains at least one thermoplastic polymer (C1) selected from the group consisting of polyesters, polyamides, and polyesteramides.

33. The heat-sealable multilayer film of claim 19, wherein the at least one component (B1) of the polymer layer (B) is impact-resistant polystyrene.

34. A process for producing a heat-sealable multilayer film of claim 30, comprising the steps of: i) melting the components used for the heat-sealable polymer layer (A) in an extruder (I), melting the components used for the polymer layer (C) in an extruder (II), if present, melting the components used for the polymer layer (B) in an extruder (III), and, if present, melting the components used for polymer layer (D) in an extruder (IV); and ii-1) producing a multilayer film by coextruding the heat-sealable polymer layer (A), the polymer layer (C), and optionally the polymer layer (B) and/or the polymer layer (D); or ii-2) producing a multilayer film by extruding individually the heat-sealable polymer layer (A), the polymer layer (C), optionally the polymer layer (B) and optionally the polymer layer (D), and then laminating the polymer layers to one another.

35. A method of closing vessels based on styrene polymers comprising the heat-sealable multilayer film of claim 19.

36. The method of claim 35, wherein the vessels are vessels containing taste-sensitive foods.

37. The heat-sealable multilayer film of claim 19, wherein the heat-sealable polymer layer (A) comprises: (i) 66 to 99 vol %, based on the total volume of the heat-sealable polymer layer (A), of structural units of styrene in the hard phase; and (ii) 1 to 34 vol %, based on the total volume of the heat-sealable polymer layer (A), of structural units of butadiene in the soft phase.

38. The heat-sealable multilayer film of claim 23, wherein the vinylaromatic-diene block copolymer (A2) is a styrene butadiene block copolymer.

Description

EXAMPLES

[0167] The coextrusion process produces a sealable multilayer film composed of polymer layers A (20 wt %), B (70 wt %) and C (10 wt %).

[0168] Sealable polymer layer A: mixture of 80 wt % of an impact-resistant polystyrene having a butadiene content of 8 wt % [Vicat B/50: 95° C.; melting index: 5 g/10 min determined to ISO 1133 (200° C./5 kg); average rubber particle size: 2 μm] and 20 wt % of a styrene-butadiene block copolymer having a butadiene content of 35 wt % (Styroflex® 2G66 from INEOS Styrolution).

[0169] FIG. 1 shows an electron micrograph (OsO4 contrast, enlargement 1:50 000) of the polymer layer A according to example 1. What is clearly apparent is a discontinuous soft phase of butadiene-containing segments of cylindrical morphology, dispersed in polystyrene.

[0170] Polymer layer B: impact-resistant polystyrene with butadiene content 8 wt %, Vicat B/50 of 95° C., melting index: 5 g/10 min determined to ISO 1133 (200° C./5 kg) and an average rubber particle size of 2 μm.

[0171] Polymer layer C: nylon-6,6, melting point 260° C., determined to ISO 1218, method A.

[0172] Polymer layer B is fed to a multiple manifold die through a main extruder, and polymer layers A and C through one side extruder each. The processing temperatures of the molding compounds were: [0173] polymer layer A: 189° C.; polymer layer B: 210° C.; polymer layer C: 280° C.

[0174] The layer structure of the film was as follows: [0175] polymer layer A: 0.05 mm; polymer layer B: 0.2 mm; polymer layer C: 0.02 mm.

[0176] The heat-sealable polymer layer A produced, and optionally also the sealable multilayer film, were used to conduct organoleptic studies.

[0177] The organoleptic studies were conducted in a 100 ml Erlenmeyer flask that had been filled with 10 g of the multilayer film or 10 g of polymer layer A according to the examples. Boiling water was poured directly from the kettle into the Erlenmeyer flask.

[0178] The water vapor was taken directly by hand to the nose and assessed by a committee of at least 3 persons by the following criteria: [0179] 0=completely neutral; no odor at all [0180] 1=slight perception of odor [0181] 2=perceptible odor, but entirely acceptable [0182] 3=strong odor, still acceptable [0183] 4=very strong odor, unacceptable.

[0184] It is advantageously possible to use the multilayer films to produce vessels where the films have no adverse odor.