Multilayer polymeric structure

Abstract

The invention relates to multilayer polymer structures having at least three layers. These layers include a polar capstock layer other than an acrylic, an olefinic substrate layer, and a tie layer. The tie layer is selected from olefinic acrylate copolymers, a block copolymer of vinyl aromatic monomer with an aliphatic conjugated diene or a derivative thereof, a copolymer of olefin and (meth)acrylic acid partially or fully in the salt form, a high impact polystyrene, and/or a vinyl cyanide-containing compound. Each layer could contain multiple sub-layers. The multilayer structure exhibits excellent structural integrity, excellent surface appearance, high impact strength, high scratch resistance, and excellent resistance to UV rays.

Claims

1. A multi-layer thermoformable polymer structure or sheet comprising: a) at least one thermoplastic polyolefin substrate layer, b) at least one styrenic-based polymer capstock layer, having a thickness of from 0.075 to 2.5 mm, wherein said styrenic-based polymer is selected from the group consisting of polystyrene, high-impact polystyrene (HIPS), acrylonitrile-butadiene-styrene (ABS) copolymers, acrylonitrile-styrene-acrylate (ASA) copolymers, styrene acrylonitrile (SAN) copolymers, methacrylate-acrylonitrile-butadiene-styrene (MABS) copolymers, styrene-butadiene copolymers (SB), styrene-butadiene-styrene block (SBS) copolymers and their partially or fully hydrogenated derivatives, styrene-isoprene copolymers, styrene-isoprene-styrene (SIS) block copolymers and their partially or fully hydrogenated derivatives, and styrene-methyl methacrylate copolymers (S/MMA), and c) a tie layer, having a thickness of from 0.05 to 1 mm, consisting of copolymers selected from the group consisting of olefinic acrylate copolymers having a homogeneous or heterogeneous distribution of compositions and molecular weights, copolymers of olefin and (meth)acrylic acid which can be partially or fully in the salt form, and mixtures thereof, wherein said tie layer has a tensile modulus of greater than 300 psi, as measured by ASTM D638, wherein the tie layer is directly adjacent to, and in between the at least one polyolefin-based substrate layer and the at least one styrenic-based polymer layer, wherein the layers a), b) and c) are coextruded together, and wherein said at least one substrate layer is thicker than said at least one capstock layer and tie layer combined, and wherein the thermoplastic polyolefin of the at least one substrate layer contains at least one polypropylene component and at least one elastomer component, where the at least one elastomer component includes at least one ethylene/alpha-olefin copolymer, at least one styrenic block copolymer, or a mixture thereof.

2. The multi-layer thermoformable structure of claim 1, wherein said at least one styrenic-based polymer layer has a weight average molecular weight of between 50,000 and 500,000 g/mol, as measured by gel permeation chromatography.

3. The multi-layer thermoformable structure of claim 1, wherein said at least one styrenic-based polymer comprises acrylonitrile-styrene-acrylate (ASA) copolymers.

4. The multi-layer thermoformable structure of claim 1, wherein said at least one styrenic-based polymer layer further comprises one or more impact modifiers, fillers, and/or fibers.

5. The multi-layer thermoformable structure of claim 1, wherein said tie layer has a tensile modulus of greater than 500 psi, as measured by ASTM D638.

6. An article formed from the thermoformable structure of claim 1.

7. The article of claim 6 in the form of a flat sheet, a rod, or a profile.

8. The article of claim 6 formed by a process selected from lamination, coextrusion, multi-shot injection molding, and insert molding.

Description

EXAMPLES

(1) The following sheet structures were prepared on a laboratory coextrusion line using a triple manifold die:

(2) TABLE-US-00001 Example 2 Layer Example 1 (Comparative) Example 3 Thickness Capstock ASA.sup.1 ASA.sup.1 PMMA.sup.4 6 mil Tie Layer Olefin-Acrylic None Olefin-Acrylic 12 mil Copolymer.sup.2 Copolymer.sup.2 Substrate TPO.sup.3 TPO.sup.3 TPO.sup.3 90 mil .sup.1LURAN SE UV 797 Natural from Styrolution. .sup.2PRD-940B from Arkema, Inc. .sup.3METAFORM 7200 from Mytex Polymers. .sup.4SOLARKOTE A200 from Arkema, Inc.

(3) After coextrusion, the composite sheet was cut into 1″ wide strips and adhesion between the capstock and substrate was measured using a 90° peel test as described in ASTM 6862-04.

(4) The following results were obtained:

(5) TABLE-US-00002 Peel Strength Example 1 15.9 lbf/in Example 2 <2 lbf/in Example 3 17.2 lbf/in

(6) Example 1 displays excellent adhesion between the layers. In contrast, example 2, having no tie layer present, exhibits very little adhesion. This demonstrates the usefulness of using an olefin-acrylic copolymer as a tie layer for coextruding styrenics such as ASA over polyolefins such as TPO. Examples 1 and 3 exhibits similar adhesion, the choice of acrylic-based polymers or styrenic-based polymers as a capstock layer depends on the end-application requirements, in terms of cost and physical properties (hardness, gloss, impact)