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DE-102024132632-A1 - Silo film

DE102024132632A1DE 102024132632 A1DE102024132632 A1DE 102024132632A1DE-102024132632-A1

Abstract

The invention relates to a silage film with a total thickness between 75 µm and 150 µm, comprising at least one outer and at least one inner layer, wherein the middle layer consists of a soft polyethylene (PE) selected from linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE), at least one functional layer arranged on both sides of the central layer, and at least one intermediate layer located between each functional layer and the outer or inner layer. At least one functional layer consists of a special polyethylene that replaces conventional barrier layers. The silage film has an oxygen permeability of less than 150 cm³ / m² /24h at 23°C and 50% relative humidity, measured according to ASTM D3985. The silage film is completely free of barrier layers, including polyamide (PA) or ethylene vinyl alcohol (EVOH).

Inventors

  • Luc Paepen

Assignees

  • RKW SE

Dates

Publication Date
20260513
Application Date
20241108

Claims (15)

  1. A silo film (1) with a total thickness between 75 µm and 150 µm, comprising: - at least one outer (2) and at least one inner layer (8), - a central layer (5) of a soft polyethylene (PE), selected from linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE), - at least one functional layer (4, 6) arranged on both sides of the central layer (5), - at least one intermediate layer (3, 7) arranged between each functional layer (4, 6) and the outer layer (2) or the inner layer (7), characterized in that at least one functional layer (4, 6) consists of a special polyethylene that replaces conventional barrier layers, and the silo film (1) has an oxygen permeability of less than 150 cm³ / m² /24h at 23 °C and 50% relative humidity, measured according to ASTM D3985, and is completely free of any barrier layers, including polyamide. (PA) or ethylene vinyl alcohol (EVOH).
  2. Silage film after Claim 1 , characterized in that the at least one functional layer (4, 6) comprises a masterbatch containing particles that reduce oxygen permeability.
  3. Silage film after Claim 2 , characterized in that the functional layer (4, 6) consists of less than 20 wt.% of the masterbatch, wherein the masterbatch contains particles that create a convoluted path for gas and moisture molecules and thereby improve the barrier properties of the film.
  4. Silage film after Claim 2 or 3 characterized by the fact that the particle size is between 1 and 100 nm.
  5. Silo film according to at least one of the preceding claims, characterized in that the at least one functional layer (4, 6) is directly adjacent to the central layer (5).
  6. Silo film according to at least one of the preceding claims, characterized in that at least one of the intermediate layers (3, 7) comprises a masterbatch containing particles that reduce oxygen permeability.
  7. Silo film according to at least one of the preceding claims, characterized in that the film (1) has a water vapor permeability of less than 20 g/m 2 in 24 h according to ASTM D6701-01.
  8. Silo film according to at least one of the preceding claims, characterized in that the masterbatch has a density of more than 0.94 g/cm 3 and less than 1.05 g/cm 3 .
  9. Silo film according to at least one of the preceding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has a density of more than 0.925 g/cm 3 and less than 0.930 g/cm 3 .
  10. Silo film according to at least one of the preceding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has a molecular weight distribution (PDI) according to ISO 16014 of less than 2.
  11. Silo film according to at least one of the preceding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has a short chain branching (SCB) of 5 - 20 SCB per 1000 carbon atoms.
  12. Silo film according to at least one of the preceding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has an elongation at break according to ISO 527-1 of more than 400%, preferably more than 550%, in particular more than 700%.
  13. Silo film according to at least one of the preceding claims, characterized in that the soft polyethylene (PE) of the middle layer (5) has a density of more than 0.880 g/cm 3 and less than 0.912 g/cm 3 .
  14. A method for producing a silo film (1) comprising the following steps: - extrusion of at least one outer layer (2) and at least one inner layer (8), - co-extrusion of a central layer (5), - co-extrusion of at least one intermediate layer (3, 7), - co-extrusion of at least one functional layer (4, 6), characterized in that at least one functional layer (4, 6) and/or intermediate layer (3, 7) incorporates a proportion of up to 20 wt.% masterbatch into the polyethylene base prior to extrusion, such that the film (1) has an oxygen permeability rate of less than 150 cm³ / m² /24h at 23°C and 50% relative humidity, as measured according to ASTM D3985.
  15. Use of a foil (1) according to one of the Claims 1 until 13 as a fully recyclable silo Foil for storing grain, silage, warm or wet industrial products.

Description

The invention relates to a silo film with a total thickness between 75 µm and 150 µm, comprising at least one outer and at least one inner layer, a central layer made of a soft polyethylene (PE) selected from linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE), and at least one functional layer arranged on both sides of the central layer, wherein at least one intermediate layer is located between each functional layer and the outer or inner layer. These multi-layered silage films with barrier properties are used in agriculture. One important application is silage film. Silage film technology is an efficient, flexible, and environmentally friendly method for preserving and storing all types of animal feed in specially designed film bags. Originally developed for ensiling green fodder, a wide variety of substrates can now be stored in silage films. Silage films are also used for composting organic material. For example, beet pulp, as well as corn and grass silage, are stored in silage films. Sealing against oxygen is crucial for silage production. Traditionally, stable polyethylene-based films are used for silage liners or silage trays. However, the use of these conventional films has repeatedly led to mold growth due to oxygen penetration. Conventional films for silo bags based on conventional polyolefins would have to be very thick to ensure sufficient oxygen impermeability and would therefore be heavy and relatively expensive to manufacture. The use of EVOH as a barrier material results in excellent barrier properties, but EVOH does not offer sufficient mechanical properties for use in silo bags. For this reason, films with special barrier structures were developed for silo bags. These barrier structures consist of polymers that exhibit particularly high impermeability to gases, especially oxygen. DE 698 17 012 T2 This describes a multi-layered film for agricultural silage products. The film has a polyamide layer that acts as an oxygen barrier. The film product can consist of two or more layers, e.g., co-extruded layers, of which at least one, or possibly several, layers consist of an insulating plastic layer. In the case of a multi-layer film with at least two insulating layers, these insulating layers can be made of the same plastic or of different plastics, all of which are airtight. DE 10 2009 052 948 B4 describes a silage covering system with a base film made of polyamide and a silage film made of polyethylene. Polyamide has excellent puncture resistance, but its tear resistance is often insufficient for demanding use as silage film in agriculture. DE 10 2017 107 060 A1 The invention discloses a method for increasing the tear resistance of a multilayer film. The multilayer film has at least one barrier arrangement having a total thickness to reduce gas permeability. According to the invention, the barrier arrangement is divided into at least two layers to increase the tear resistance. As part of the European Green Deal and the Circular Economy Action Plan, the EU has set the goal that all packaging placed on the market in the EU should be either reusable or fully recyclable by 2030. By 2025, at least 65% of all packaging waste should be recycled, with a rate of at least 50% for plastics, which are frequently used to make films. By 2030, this share should increase to 55% for plastic-based films. Recycling PE plastic films containing EVOH can be problematic because EVOH has barrier properties that complicate processing. EVOH is water-soluble and difficult to separate from polyethylene, negatively impacting the quality of the recycled material. Furthermore, the differing melting points and chemical properties of these materials can lead to poor mixing during recycling. The result is often low-quality recyclates that do not meet the requirements for new applications. The problem with recycling polyethylene films containing PA (polyamide) is primarily due to their differing chemical and physical properties. PA has a higher melting point compared to polyethylene and PA exhibits different thermal behavior, which can complicate the recycling process. These materials do not mix well during recycling, resulting in a lower-quality recycled product. Furthermore, the presence of PA can cause problems in achieving the desired properties for the recycled material, making it less suitable for new applications. PA or EVOH can cause die blockages and negatively affect bubble stability during the blown extrusion of polyethylene films. This is due to the fact that both materials have different thermal and viscoelastic properties. Polyamide has a higher melting point and different flow behavior, which prevents it from mixing optimally with polyethylene during the extrusion process. This can lead to deposits in the dies, reducing the flow rate and resulting in uneven extrusion. EVOH, which also has a high melting point, can cause similar problems. It tends to decompose at higher temperatures, leading