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EP-4673504-B1 - THERMOPLASTIC MOLDING COMPOSITIONS FOR EXTRUSION WITH HIGH MELT STABILITY

EP4673504B1EP 4673504 B1EP4673504 B1EP 4673504B1EP-4673504-B1

Inventors

  • RICHTER, FLORIAN
  • KRAUSS, Gert
  • LEHENMEIER, Maximilian

Dates

Publication Date
20260513
Application Date
20250430

Claims (15)

  1. Thermoplastic molding composition (M) comprising: (A) 30 to 100 wt.-% of at least one thermoplastic polymer blend (A) comprising or consisting of: (A-1) 81.5 to 99.39 wt.-% of at least one semi-aromatic polyester (A-1); (A-2) 0.01 to 2 wt.-% of at least one acrylic acid polymer (A-2) composed of: (a-2a) 70 to 100 wt.-%, based on (A-2), of acrylic acid (a-2a), and (a-2b) 0 to 30 wt.-%, based on (A-2), of at least one other ethylenically unsaturated monomer (a-2b) copolymerizable with acrylic acid, selected from the group of the mono-ethylenically unsaturated carboxylic acids; (A-3) 0.05 to 5 wt.-% of at least one epoxy-containing vinylaromatic copolymer (A-3); (A-4) 0.5 to 10 wt.-% of at least one epoxy-containing olefinic copolymer (A-4); (A-5) 0.05 to 1.5 wt.-% of at least one polyolefin wax (A-5) prepared by means of metallocene catalysts, where the polyolefin wax is a homopolymer of ethylene, a copolymer of ethylene with one or more 1-olefins which may be linear or branched, substituted or unsubstituted and having 3-18 carbon atoms, or a homopolymer of propylene, wherein the polyolefin wax (A-5) is polar modified by reacting the polyolefin wax with an α , β -unsaturated carboxylic acid or a derivative thereof; wherein the sum of the proportions of components (A-1), (A-2), (A-3), (A-4) and (A-5) add up to 100 wt.-%; and (B) 0 to 70 wt.-% of one or more further additives and processing aids (B); wherein the sum of the proportions of components (A) and (B) add up to 100 wt.-%.
  2. Thermoplastic molding composition (M) according to claim 1, wherein the at least one acrylic acid polymer (A-2) is composed of (a-2a) 85 to 100 wt.-%, based on (A-2), of acrylic acid (a-2a), and (a-2b) 0 to 15 wt.-%, based on (A-2), of at least one other ethylenically unsaturated monomer (a-2b) copolymerizable with acrylic acid, selected from the group of the mono-ethylenically unsaturated carboxylic acids.
  3. Thermoplastic molding composition (M) according to claim 1 or 2, wherein the at least one acrylic acid polymer (A-2) has a weight average molecular weight M W in the range of from 1,000 to 12,000 g/mol, wherein the molecular weights of the acrylic acid polymer (A-2) are determined by gel permeation chromatography (GPC) on aqueous solutions of polymers buffered to pH 7 using hydroxyethyl methacrylate copolymer networks as stationary phase and sodium polyacrylate standards.
  4. Thermoplastic molding composition (M) according to any of claims 1 to 3, wherein the thermoplastic molding composition (M) comprises 0.05 to 1.5 wt.-% of the at least one acrylic acid polymer (A-2) and/or, wherein the thermoplastic molding composition (M) comprises 0.05 to 2.5 wt.-% of at least one epoxy-containing vinylaromatic copolymer (A-3) selected from poly(styrene-glycidylether-methyl methacrylates).
  5. Thermoplastic molding composition (M) according to any of claims 1 to 4, wherein the least one epoxy-containing olefinic copolymer (A-4) is selected from one or more copolymer(s) composed of: (a-4a) 50 to 94.8 wt.-% of at least one α -olefin with 2-8 carbon atoms; (a-4b) 5 to 40 wt.-% of a C 1 -C 12 alkyl ester of acrylic acid or methacrylic acid or mixtures of such esters; (a-4c) 0.1 to 20 wt.-% of ethylenic unsaturated mono- or dicarboxylic acid or a functional derivative of such an acid; and (a-4d) 0.1 to 20 wt.-% of a monomer containing epoxy groups, wherein the sum of the proportions of constituents (a-4a), (a-4b), (a-4c), and (a-4d) add up to 100 wt.-%.
  6. Thermoplastic molding composition (M) according to any of claims 1 to 4, wherein the at least one thermoplastic polymer blend (A) comprises or consists of: (A-1) 87.5 to 99.33 wt.-% of at least one semi-aromatic polyester (A-1); (A-2) 0.05 to 1.5 wt.-% of the at least one acrylic acid polymer (A-2); (A-3) 0.05 to 2.5 wt.-% of the at least one epoxy-containing vinylaromatic copolymer (A-3); (A-4) 0.5 to 7.5 wt.-% of the at least one epoxy-containing olefinic copolymer (A-4); (A-5) 0.07 to 1 wt.-% of the at least one polyolefin wax (A-5).
  7. Thermoplastic molding composition (M) according to any of claims 1 to 6, wherein the thermoplastic molding composition (M) comprises 0 to 5 wt.-% of an epoxidized oil (B-1) or oil mixture in which the at least partly unsaturated fatty acids in the underlying fatty acid esters of the oil or oil mixture contain 12 to 22 carbon atoms;
  8. Process for producing a thermoplastic molding composition (M) according to any of claims 1 to 7, wherein the process comprises at least the step of melt-mixing components (A-1), (A-2), (A-3), (A-4), (A-5) and optionally component(s) (B).
  9. Use of a thermoplastic molding composition (M) according to any of claims 1 to 7 as coating material.
  10. Coated article (S), comprising: (S-1) at least one substrate layer (S-1), and (S-2) at least one coating layer (S-2), wherein the at least one coating layer (S-2) is coated on at least one surface of the at least one substrate layer (S-1), and wherein the at least one coating layer (S-2) comprises or consists of a thermoplastic molding composition (M) according to any of claims 1 to 7.
  11. Coated article (S) according to claim 10, wherein the substrate layer (S-1) comprises or consists or a fiber substrate, preferably selected from paper-based substrate materials.
  12. Process for the production of a coated article (S) according to claim 10 or 11, wherein the process at least comprises the following process steps: (i) providing of a substrate layer (S-1); (ii) providing of a thermoplastic molding composition (M) according to any of claims 1 to 8; (iii) melting of the thermoplastic molding composition (M), and (iv) coating of the molten thermoplastic molding composition (M) on at least one surface of the substrate layer (S-1) to obtain a coating layer (S-2) comprising or consisting of the thermoplastic molding composition (M).
  13. Process for the production of a coated article (S) according to claim 12, wherein the substrate layer (S-1) is a paper-based substrate material and the process comprises the further process step (pre-iv) wherein the paper-based substrate material is pre-treated before process step (iv) is carried out by flame-treatment or corona-treatment of the at least one surface to which the coating layer (S-2).
  14. Use of a coated article (S) according to claim 10 or 11 as packaging material (P) or construction material.
  15. Packaging material (P) comprising or consisting of a coated article (S) according to claim 10 or 11.

Description

The present invention relates to thermoplastic molding compositions based on semi-aromatic polyesters, which are particularly suitable for extrusion coating processes, especially on paper substrates. The invention further relates to molded articles and films comprising the thermoplastic molding, in particular to coated articles. In a further aspect, the invention relates to processes for producing the thermoplastic molding composition and to extrusion processes using the thermoplastic molding compositions. The invention further relates to packaging materials comprising the coated articles coated with the thermoplastic molding compositions according to the invention. Extrusion coating with polymers is a widely practiced technique that involves applying a thin layer of a polymeric material to various substrates such as paper, paperboard, fabrics, and metal foils. During extrusion coating, a molten polymeric material is extruded through a flat die, resulting in a film having a thickness of only a few micrometers. This film is then coated onto a substrate and cooled, allowing the polymeric material to adhere to the surface of the substrate. For the extrusion coating process, the polymeric material used should possess a good combination of flowability, melt stability and viscosity. The polymeric material should have good melt flow properties, allowing it to be easily extruded through the flat die. Additionally, it should exhibit sufficient adhesion properties to ensure proper bonding to the substrate surface. Sufficient melt stability is required to achieve a thin and uniform coating on the substrate and a stable production process. Polyesters exhibit a good combination of properties as barrier coatings, such as a high moisture and oxygen barrier, combined with good grease and oil barrier and resistance. Commercial thermoplastic polyesters, such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), are also highly temperature stable. The coated articles using these polymers can therefore be used in high temperature applications. However, polyesters, such as PET and PBT, exhibit several drawbacks in the extrusion coating process, such as a low melt stability during film extrusion, which leads to an unstable melt curtain during the extrusion process and the so-called "edge-waving" (i.e., the outer edges of the extruded films are wavy and no constant coating width is achieved). Therefore, those polymers can only be coated onto the substrate at low velocities. In addition, the adhesion of those polyesters, especially on paper and paperboard, is very low, in particular at high processing speeds (i.e. high substrate velocities). Further problems that may occur during the coating process is the so-called "neck-in", an effect in which the width of the product film becomes substantially narrower than the width of the die outlet. WO 2011/110750 discloses to a heat-sealable biodegradable packaging material comprising a fiber substrate, which is coated with a polymeric layer, which contains polylactide and a biodegradable polyester, by extrusion or coextrusion. Small amounts of acrylic copolymers can be blended into the polymeric layer to improve the adhesion to the substrate. The production speed of the coating process is not addressed in WO 2011/110750. JP5995471 describes a laminate on a paper base material of PBT containing 0.1 to 0.7 wt.-% of an organic compound having at least two epoxy groups in one molecule. The laminate exhibits reduced neck-in during processing. Surface adhesion is not addressed in JP5995471. WO 2005/100015 discloses lamination processes using an olefinic copolymer to provide improved adhesion of a foil to thermoplastic compositions. The disclosed olefinic copolymers can for example be ethylene/methacrylate copolymers or ethylene/acrylic acid copolymers. In contrast to the present invention, the disclosed articles are multilayer structures and not monolayer coatings, where the olefinic copolymers are laminated as a separate layer. US 7,507,473 discloses a coated paper article containing a primer to enhanced adhesion of polyethylene terephthalate to the paperboard. The primer used for adhesion enhancement is an ammonium catalyzed, self-crosslinking copolymer of ethylene-vinyl acetate with N-methylol acryl amide functional groups attached to a polymer backbone that needs to be applied to the paper. WO 2009/133016 describes two-component adhesion compositions suitable for extrusion coating on paper substrates which comprises (A) a high melt strength polypropylene and a second component (B) to increase the melt-strength and adhesion to paper board selected from the group of (i) maleic anhydride-modified polypropylene (MAPP) (ii) maleic anhydride-modified polypropylene wax (iii) polypropylene homopolymer with high melt flow rate or (iv) ethylene-vinyl acetate-based hot melt adhesive. The invention is limited to polypropylene and other classes of additives (B) are used to improve the