High-density foam flake composite & 3D sound-absorbing component

Applicant: Carpenter Engineering Foams Belgium
Inventors: Kristiaan Bracke [BE]; Rob De Thaey [BE]; Mathieu Gontier [BE]
Patent number: EP4488024
Publication date: 2025-01-08

The invention introduces a technique for producing high-density foam flake composite materials, which consist of foam flakes securely joined together by a thermoplastic binding agent, that can be applied in various sectors, including furniture, automotive, and construction, where effective sound absorption and robust structural support are crucial.

Foam flake composite sheets are produced by mixing foam flakes with a thermoplastic binder. This mixture is then layered, often using an airlaid process, and subjected to heat until the binder melts, allowing the foam flakes to adhere to each other. After this process, the sheet is consolidated. The foam flakes used in these sheets are often sourced from recycled materials, such as discarded upholstery or old mattresses, as well as industrial waste. In some cases, new foam flakes may be incorporated alongside the recycled flakes. The density of these composite sheets typically ranges from 20 to 150 kg/m³, influenced mainly by the average density of the foam flakes, the amount of binder and the degree of compression applied during consolidation.

The binder is usually a thermoplastic, which can be incorporated into the air-laid sheet in the form of granules, powder or melt fibres. These fusible fibres are characterised by their elongated, needle-like shape. Bi-component fibres are also used in the production of these sheets. These fibres consist of a core surrounded by a melt fibre sheath, where the sheath has a lower melting point than the core. When bi-component fibres are used, only the melt fibre shell is melted to effectively bond the foam flakes together.

In certain applications there is a need for high density foam flake composite sheets that have a three dimensional shape. This is usually achieved using a thermocompression mould, which allows simultaneous compression and moulding of the foam flake composite sheet. A major challenge in producing these three-dimensional high density sheets is the need to heat the material to a temperature where the binder melts. This heating is essential to allow the sheet to conform to the contours of the mould and to facilitate the thermocompression process. However, due to the uneven nature of foam flake composite sheet, it can be difficult to achieve uniform heating throughout the material before it is placed in the thermocompression mould. For thermocompression to effectively convert the flat sheet into its intended high-density, three-dimensional shape, the core of the sheet must reach the melting point of the binder. Unfortunately, the heated foam flake composite sheet is prone to tearing during this process, which is problematic as it can lead to surface irregularities in the final product. As a result of these challenges, foam flake composite sheets are often limited to simpler three-dimensional shapes and lower densities.

While certain earlier documents mention the use of melt fibers as binding agents, they fail to explain the process for creating a high-density foam flake composite product with intricate three-dimensional shapes.

Addressing these limitations, the invention aims to present a method that enables the production of three-dimensionally shaped foam flake composite sheets with enhanced density, overcoming the previously noted challenges.

The invention describes a process for creating a high-density foam flake composite product through a series of steps:

First, a section of a low-density foam flake composite sheet, initially at a certain thickness, is subjected to compression: 

• This starting material is either at a specific temperature or has been heated to ensure that a significant portion of the binding agent is in a molten state.
• During the compression, the force applied causes the molten binding agent to fill the surface cavities of the foam flakes.
• In this compression phase, at least one part of the initial product is reduced to a second thickness, which is thinner than the original, resulting in a denser material.
• Finally, the compressed product is allowed to cool below the melting point of the binding agent, resulting in a semi-finished foam flake composite sheet that features at least one section of high density.

The semi-finished sheet product from the previous step is heated to a temperature that melts the binding agent, which fuses the neighboring foam flakes together. 

• Next, the heated sheet is thermoformed in a mold to achieve the desired shape. 
• Once the product cools below the binding agent's melting point, the mold is opened, allowing for the removal of the shaped foam flake composite, which features at least one high-density section.