Polyether block amide-poly(meth)acrylate foams

Abstract

A mixture contains at least one polyether block amide (PEBA) and at least one poly(meth)acrylate, selected from poly(meth)acrylimides, poly-alkyl(meth)acrylates, and mixtures thereof. The mass ratio of PEBA to poly(meth)acrylate is 95:5 to 60:40. The polyalkyl(meth)acrylate contains 80% by weight to 99% by weight of methyl methacrylate (MMA) units and 1% by weight to 20% by weight of C1-C10-alkyl acrylate units, based on the total weight of polyalkyl(meth)acrylate. The mixture can be processed to give foamed mouldings. The mouldings can he used in footwear soles, stud material, insulation or insulating material, damping components, lightweight components, or in a sandwich structure.

Claims

1. A mixture, comprising: a. at least one polyether block amide (PEBA), and b. at least one poly(meth)acrylate selected from the group consisting of poly(meth)acrylimides, polyalkyl(meth)acrylates, and mixtures thereof, wherein the mass ratio of the at least one PEBA to the at least one poly(meth)acrylate is in a range from 95:5 to 60:40, and wherein the at least one poly(meth)acrylate comprises a polyalkyl(meth)acrylate, and wherein the polyalkyl(meth)amilate contains 80% by weight to 99% by weight of methyl methacrylate (MMA) units and 1% by weight to 20% by weight of C.sub.1-C.sub.10-alkyl acrylate units, based on the total weight of the polyalkyl(meth)acrylate.

2. The mixture according to Claim 1, wherein the at least one PEBA is an amino-regulated PEBA.

3. The mixture according to claim 1, wherein the at least one PEBA is a carboxyl-regulated PEBA.

4. The mixture according claim 1, wherein the at least one PEBA contains 20 to 60 mmol/kg of amino end groups.

5. The mixture according to claim 1, wherein the fraction of polyether in the at least one PEBA contains 10% to 50% by weight, based on the total weight of the at least one PEBA.

6. The mixture according to claim 1, wherein the at least one poly(meth)acrylate comprises a poly(meth)acrylamide, and wherein the poly(meth)acrylimide comprises the following groups: a. an N-alkylacrylimide of the formula (IV) ##STR00003## wherein R.sup.1 and R.sup.2 are the same or different, and are hydrogen or a methyl group, and wherein R.sup.3 is hydrogen, an alkyl radical having 1 to 20 carbon atoms, or an aryl radical having 2 to 20 carbon atoms, b. a (meth)acrylic acid, c. a (meth)acrylic anhydride, and d. a (meth)acrylate, wherein groups a. to d. are each present to an extent of at least 1% by weight, based, on the total weight of the poly(meth)acrylimide.

7. The mixture according to claim 6, wherein the poly(meth)acrylimide contains 10-95% by weight of units of the formula (IV).

8. The mixture according to claim 1, wherein the at least one poly(meth)acrylate comprises a poly(meth)acrylimide, and wherein the molecular weight Mw of the poly(meth)acrylimide is in the range from 50,000 to 150,000 g/mol, determined by GPC against PMMA standard.

9. The mixture according to claim 1, wherein the polyakyl alkyl(meth)acrylate contains styrene as a comonomer.

10. The mixture according to claim 1, wherein the polyalkyl(meth)acrylate is an impact-modified polymer.

11. The mixture according to claim 1, wherein the mixture contains at least one of the components selected from the group consisting of colourants, light stabilizers, UV stabilizers, UV absorbers, IR absorbers, antimicrobial actives, flame retardants, heat stabilizers, antioxidants, crosslinking polymers, organic or inorganic fibre-reinforcing additives, impact modifiers, and mixtures thereof.

1. A foamed moulding obtainable from the mixture according to claim 1.

13. A process for producing a foamed moulding, the process comprising: a. melting the mixture according to claim 1, thereby obtaining a molten mixture, b. extruding the molten mixture to obtain pellets, c. injection-moulding the pellets to obtain a moulding or an extruded sheet, and d. introducing the moulding or the extruded sheet into an autoclave and treating with a physical blowing agent to obtain the foamed moulding.

14. A process for producing a foamed moulding, the process, comprising: a. melting the mixture according to claim 1, thereby obtaining a molten mixture, and b. treating the molten mixture with a physical blowing agent and extruding the molten mixture with a perforated plate or a die to obtain the foamed moulding.

15. A method for preparing a footwear sole, stud material, insulation or insulating material, a damping component, a lightweight component, or in a sandwich structure, the method comprising: producing a foamed moulding with the mixture according to claim 11.

16. The mixture according to claim 4, wherein the at least one PEBA contains 30 to 50 mmol/kg of amino end groups.

17. The mixture according to claim 7, wherein the poly(meth)acrylimide contains 25-40% by weight of units of the formula (IV).

18. The mixture according to claim 11, wherein the mixture contains a colourant, and wherein the colourant is a pigment or a dye.

19. The mixture according to claim 18, wherein the colourant is an organic dye.

Description

EXAMPLES

[0101] Dry premixtures containing PEBA and poly(meth)acrylate were produced from pellets: These mixtures were metered at a throughput of 20 kg/h by means of gravimetric metering balances into the Coperion ZSK25 WLE twin-screw compounder preheated to 240° C. The screw configuration used was a standard screw as, for example, for the production of polyamide compounds. In the twin-screw compounder, the mixture was heated at a screw speed of 250 rpm to give a melt. The melt was pressed through a 3-hole die plate with diameter 4 mm in each case to give melt strands. These melt strands were cooled down in a water bath at room temperature. The cooled and hardened strands were chopped into pellets in a standard strand pelletizer. The resultant pellets were dried in dry air dryers at 80° C. for 12 h to a water content of <0.02%. The dried pellets were processed on a standard injection moulding machine (Engel Victory 650/200) with a standard 3-zone screw at a barrel temperature of 240° C. to give sheets. The injection mould was cooled to 40° C. Cubic test specimens having either edge lengths of 30×10×5 mm or edge lengths of 40×30×10 mm were sawn out of the resultant injection-moulded sheets. The test specimens were saturated with CO.sub.2 in a standard autoclave over a period of 4.5 h (small specimens) or 95 h (large specimens) at a pressure of 300 bar and a temperature of 140° C. with CO.sub.2. The foaming proceeded with spontaneous expansion.

[0102] The following substances were used:

[0103] PEBA 1: amino-terminated PEBA containing 30% by weight of polyether blocks (VESTAMID® E58-S4)

[0104] PEBA 2: carboxyl-terminated PEBA containing 20% by weight of polyether blocks (VESTAMID® E62-S3)

[0105] (Meth)acrylate 1: polymethylmethacrylimide, as described in EP 1 755 890 B1, having a molecular weight of 100 000 g/mol (determined by GPC against PMMA standard), consisting of 30% by weight of units of formula IV, where R.sup.1, R.sup.2 and R.sup.3 are each a methyl group, of 57% by weight of methyl methacrylate (MMA) units, of 10% by weight of methacrylic anhydride (MA) units and of 3% by weight of methacrylic acid (MAA) units (determined by IR spectroscopy).

[0106] (Meth)acrylate 2: impact-modified poly(meth)acrylate, having a molecular weight of 200 000 g/mol (determined by GPC against PMMA standard), consisting of 55% by weight of methyl methacrylate (MMA) units, 20% by weight of styrene units, 2% by weight of ethyl acrylate (EA) units and 23% by weight of rubber. The rubber is polybutadiene, grafted with a shell of MMA units and styrene units, and with an active diameter for impact modification (corresponding to an average agglomerate diameter) of 300 nm (determined by transmission electron microscopy).

[0107] (Meth)acrylate 3: impact-modified poly(meth)acrylate, as (meth)acrylate 2, here with a molecular weight of 140 000 g/mol (determined by GPC against PMMA standard).

[0108] PA12: carboxyl-terminated nylon-12 (VESTAMID® L1901)

TABLE-US-00001 TABLE 1 Compositions #1 to #9 used. Density in kg/cm.sup.3 Polyamide Poly(meth)acrylate (unfoamed) #1* 99% by wt. of PEBA 1  1% by wt. of (meth)acrylate 1 1042/1030 #2 90% by wt. of PEBA 1 10% by wt. of (meth)acrylate 1 1045 #3 80% by wt. of PEBA 1 20% by wt. of (meth)acrylate 1 1062 #4 70% by wt. of PEBA 1 30% by wt. of (meth)acrylate 1 1079 #5 70% by wt. of PEBA 2 30% by wt. of (meth)acrylate 1 1069 #6* 70% by wt. of PA12 30% by wt. of (meth)acrylate 1 1065 #7 70% by wt. of PEBA 1 30% by wt. of (meth)acrylate 2 1032/1049 #8 70% by wt. of PEBA 1 30% by wt. of (meth)acrylate 3 1005/1047 #9* 100% by wt. of PEBA 1 — 1010 *non-inventive

[0109] Thereafter, the foamed compositions were visually examined under a scanning electron microscope and the following properties were ascertained or calculated:

[0110] d.sub.cell: average diameter of the cells in μm

[0111] t.sub.cell: average thickness of the cell walls in μm

[0112] N.sub.cell: number of cells per cm.sup.3

[0113] ρ: density of the foamed material in kg/cm.sup.3

[0114] Δρ: change in density compared to unfoamed material

[0115] Foam quality: The foams were visually assessed by microscope images at different resolutions. Microscope images from Examples 1 to 9 are reproduced in FIGS. 1 to 9.

[0116] 1: inhomogeneous cell distribution, nonuniform cells

[0117] 2: homogeneous cell distribution, uniform cell size

TABLE-US-00002 TABLE 2 Physical measurement data of compositions #1 to #9. T in ° C. d.sub.cell t.sub.cell N.sub.cell ρ Δρ Foam quality #1* 140  6 0.5   48 .Math. 10.sup.9 460 55% 1 #2 140 25 0.9 0.11 .Math. 10.sup.9 110 89% 2 #3 140 24 0.9 0.14 .Math. 10.sup.9 110 90% 2 #4 140 23 1.2 0.14 .Math. 10.sup.9 260 76% 2 #5 155 22 1 0.14 .Math. 10.sup.9 150 86% 2 #6* 140 *** *** *** 900 15% 1 #7 140 20 0.7 0.24 .Math. 10.sup.9 110 90% 2 #8 140 23 <0.5 0.12 .Math. 10.sup.9  90 91% 2 #9* 140 ** ** ** ** ** 1 *non-inventive ** foam collapsed *** not determined, since density too high

[0118] The foams of the inventive compositions #2 to 5 and #7 and #8, compared to the prior art compositions, showed a high cell diameter dce of 21 to 25 μm and a reduced number of cells per cubic centimetre N.sub.cell. The density was in the range from 90 to 260 kg/cm.sup.3 and was reduced compared to the starting material by 76% to 91%. In addition, the foams of the composition according to the invention show a homogeneous cell distribution with cells of virtually equal size (cf. FIGS. 2 to 5, 7 and 8).

[0119] In the case of the prior art materials, distinctly lower reductions in density of 15% to 55% were recorded (#1, #6); the average diameters of the cells were likewise below the values for the inventive compositions (#1). Mixture #6 showed such a high density that diameter and the number of cells could not be determined. The foam of mixture #9 collapsed. The foam structures had an inhomogeneous cell distribution with cells of different size (cf. FIGS. 1, 6 and 9).

[0120] The non-inventive compositions #1 (PEBA content 99% by weight), #6 (nylon-12 rather than PEBA) and #9 (PEBA without acrylate) were found to be unsuitable foam materials. Inventive mixtures #2 to #4 and #5 and #7 composed of amino-terminated and carboxyl-terminated PEBA with higher poly(meth)acrylate contents compared to mixture #1 showed homogeneous, regular cells.