POLYETHER BLOCK AMIDE-POLY(METH)ACRYLATE FOAMS

Abstract

A mixture contains at least one amino-regulated polyether block amide (PEBA) and at least one poly(meth)acrylate selected from poly(meth)acrylimides, polyalkyl(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 be 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 amino-regulated 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 amino-regulated PEBA to the at least one poly(meth)acrylate is in the range from 95:5 to 60:40, and wherein the polyalkyl(meth)acrylate, if present, 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 amino-regulated PEBA contains 20 to 60 mmol/kg of amino end groups.

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

4: The mixture according to claim 1, wherein the at least one amino-regulated PEBA has a Shore D hardness of 30 to 70, measured to ISO 868 at 23° C.±2° C.

5: 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 3 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.

6: The mixture according to claim 5, wherein the poly(meth)acrylimide contains 10-95% by weight of units of the formula (IV).

7: 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.

8: The mixture according to claim 1, wherein the polyalkyl(meth)acrylate, if present, contains styrene as a comonomer.

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

10: The mixture according to claim 1, wherein the mixture contains at least one of the components selected from the group consisting of colourants, pigments, organic dyes, 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.

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

12: 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.

13: 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.

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

15: The mixture according to claim 2, wherein the at least one amino-regulated PEBA contains 30 to 50 mmol/kg of amino end groups.

16: The mixture according to claim 4, wherein the at least one amino-regulated PEBA has a Shore D hardness of 35 to 65, measured to ISO 868 at 23° C.±2° C.

17: The mixture according to claim 6, wherein the poly(meth)acrylimide contains 25-40% by weight of units of the formula (IV).

Description

EXAMPLES

[0058] 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. The foaming proceeded with spontaneous expansion.

[0059] The following substances were used:

PEBA 1: amino-terminated PEBA containing 30% by weight of polyether blocks (VESTAMID® E58-S4)
PEBA 2: carboxyl-terminated PEBA containing 20% by weight of polyether blocks (VESTAMID® E62-S3)
(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).
(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).
(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).
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

[0060] Thereafter, the foamed compositions were visually examined under a scanning electron microscope and the following properties were ascertained or calculated:

d.sub.cell: average diameter of the cells in μm
t.sub.cell: average thickness of the cell walls in μm
N.sub.cell: number of cells per cm.sup.3
ρ: density of the foamed material in kg/cm.sup.3
Δρ: change in density compared to unfoamed material
Foam quality: Visual assessment of the foams with reference to FIGS. 1 to 9 at different resolutions
1: inhomogeneous cell distribution, nonuniform cells
2: homogeneous cell distribution, uniform cell size

TABLE-US-00002 TABLE 2 Physical measurement data of compositions #1 to #9. Foam T in ° C. d.sub.cell t.sub.cell N.sub.cell ρ Δρ quality #1* 140 6 0.5 .sup. 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* 140 0.7 <0.5  7500 .Math. 10.sup.9  650 40% 1 #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

[0061] The foams of the inventive compositions #2 to 4 and #7 and #8, compared to the prior art compositions, showed a high cell diameter d.sub.cell 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 4, 7 and 8).

[0062] In the case of the prior art materials, distinctly lower reductions in density of 15% to 55% were recorded (#1, #5, #6); the average diameters of the cells were likewise below the values for the inventive compositions (#1, #5). Mixture #8 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, 5, 6 and 9).

[0063] The non-inventive compositions #1 (PEBA content 99% by weight), #5 (carboxyl-terminated PEBA), #6 (nylon-12 rather than PEBA) and #9 (PEBA without acrylate) were found to be unsuitable foam materials. Inventive mixtures #2 to #4 and #6 and #7 composed of amino-terminated PEBA with higher poly(meth)acrylate contents compared to mixture #1 showed homogeneous, regular cells.