Manufacturing Method of Paper-Based Foam Board with Protective Layer

The present invention relates to a manufacturing method of a paper-based foam board with a protective layer. More particularly, the invention relates to a manufacturing method of a paper-based foam board that has a protective layer on each of its two sides and that can be used to make a paper container for food while providing the paper container with a three-dimensional (e.g., protruding and/or sunken) surface feature.

The way the society works nowadays has caused an increasing demand for food takeout and food delivery. In addition, food packaging containers used in the eating-out market has been an indispensable part of the entire eating-out industry. Therefore, the design of such packaging containers calls for innovation in continual research and development efforts in order to meet the requirements of safety, suitability, cost, ease of operation, and so on.

There have been paper containers whose surface has three-dimensional patterns formed of a foaming material, with the foam layer typically made by: mixing a liquid adhesive with a thermoplastic polymer to form a foaming composite material, and then coating the surface of a paper container with the composite material in order for the composite material to form the foam layer. With this manufacturing method, however, the foam layer is not effectively bonded to the surface of the paper container and may therefore peel off. Also, the foam layer has low resistance to heat.

The present invention relates to a manufacturing method of a paper-based foam board with a protective layer and is intended mainly to solve such problems of the conventional paper containers as: the protective layer of such a container failing to form an effective bond with the foam layer on the protective layer such that the foam layer peels off easily, and the foam layer having low resistance to heat.

The present invention provides a manufacturing method of a paper-based foam board with a protective layer, and the manufacturing method includes the following steps: preparing a foaming coating material, which steps involves preparing a water-based foaming coating material containing a water-based polyolefin that makes up at least 50% by mass of the water-based foaming coating material; providing a paper substrate having a first surface and a second surface; forming a first protective layer, which step involves forming a waterproof/oil-proof layer on the first surface; forming a second protective layer, which step involves forming a waterproof/oil-proof layer on the second surface; and forming a foam layer, which step involves applying to the first protective layer the water-based foaming coating material in which the water-based polyolefin makes up at least 50% by mass of the water-based foaming coating material.

The present invention further provides a structure of a paper-based foam board that has a protective layer on each of its two sides. The foam board is made by the foregoing manufacturing method of a paper-based foam board with a protective layer and includes: the paper substrate having the first surface and the second surface; the first protective layer formed as a waterproof/oil-proof layer on the first surface; the second protective layer formed as a waterproof/oil-proof layer on the second surface; and the foam layer formed on the first protective layer and formed of the water-based foaming coating material in which the water-based polyolefin makes up at least 50% by mass of the water-based foaming coating material.

The present invention also provides a container structure made of a paper-based foam board that has a protective layer on each of its two sides. The container structure includes: a bottom plate, which is a paper substrate, with a waterproof/oil-proof layer formed on a side of the paper substrate that corresponds to the inner side of the container structure; and a sidewall formed of the paper-based foam board that has a protective layer on each of its two sides, wherein the paper-based foam board is made by the foregoing manufacturing method of a paper-based foam board that has a protective layer on each of its two sides, and wherein the sidewall extends upward from and surrounds the bottom plate, with the foam layer formed on the outer side of the container structure and being resistant to heat of a temperature in the range from 90° C. to 140° C.

Implementation of the present invention at least produces the following advantageous effects:

The embodiment shown inprovides a manufacturing method Sof a paper-based foam board that has a protective layer on each of its two sides. The manufacturing method Sincludes the steps of: preparing a foaming coating material (S), providing a paper substrate (S), forming a first protective layer (S), forming a second protective layer (S), and forming a foam layer (S).

The embodiment shown inprovides a structure of a paper-based foam boardthat has a protective layer on each of its two sides. The paper-based foam boardhaving a protective layer on each of its two sides is made by the foregoing manufacturing method Sof a paper-based foam board that has a protective layer on each of its two sides, and the structure of the foam boardincludes: a paper substrate, a first protective layer, a second protective layer, and a foam layer.

Referring back to, the step Sof preparing a foaming coating material includes mixing a water-based polyolefin with a water-based or water-soluble substrate in order to make a water-based foaming coating material in which the water-based polyolefin makes up at least 50% by mass of the water-based foaming coating material.

The water-based foaming coating material may be composed of a water-based ethylene-vinyl acetate, a water-based polyvinyl alcohol, a water-based acrylic resin, and/or a water-based polyurethane resin, in addition to the water-based polyolefin.

More specifically, the water-based polyolefin alone constitutes at least 50% by mass of the water-based foaming coating material, and the water-based polyolefin constituting at least 50% by mass of the water-based foaming coating material may be mixed, in a predetermined ratio, with a water-based resin such as a water-based polyvinyl alcohol, a water-based acrylic resin, a water-based polyurethane resin, and/or a water-based ethylene-vinyl acetate.

The water-based polyolefin may be added with a water-based acrylic resin, a water-based polyurethane, a water-based ethylene-vinyl acetate, a water-based polyvinyl alcohol, a water-based foaming agent in powder form, a dispersing agent, a defoaming agent, and/or a wetting agent.

The step Sof providing a paper substrate includes providing the paper substrate, which has a board-like structure and therefore has a first surfaceand a second surface.

The step Sof forming a first protective layer and the step Sof forming a second protective layer are intended to prevent oil and water from seeping into, and thus causing structural damage to, the paper substrateor to prevent the paper substratefrom making direct contact with, and thus contaminating, food. Therefore, a waterproof/oil-proof layer is formed on the first surfaceand on the second surfaceto form the first protective layerand the second protective layerrespectively.

The step Sof forming a foam layer includes applying the water-based foaming coating material containing a water-based polyolefin that makes up at least 50% by mass of the water-based foaming coating material to the first protective layerin order to form the foam layer. The material properties of the foam layerand the first protective layerallow the foam layerand the first protective layerto be tightly bonded to each other through a covalent bond.

The step Sof forming a foam layer may include: applying the water-based foaming coating material by a printing or coating process so as to form a predetermined pattern and/or predetermined text, and heating the resulting foam layerin order for the foam layerto form a three-dimensional (e.g., protruding and/or sunken) surface feature according to the shape of the pattern and/or text.

The embodiment shown inandprovides a container structuremade of a paper-based foam board that has a protective layer on each of its two sides. The container structuremade of a paper-based foam board that has a protective layer on each of its two sides serves mainly to package portable takeout food and includes: a bottom plateand a sidewall. The bottom plateand the sidewalljointly form a receiving spacefor accommodating food.

The bottom plateis also a paper substrateand is used to form the bottom portion of the container structure. A waterproof/oil-proof layer that is identical in material and function to those stated above and that serves as a third protective layeris formed at least on the side of the bottom platethat corresponds to the inner side of the container structure.

The sidewallis used to form the side of the container structure. The sidewallis a paper-based foam boardthat has a protective layer on each of its two sides and that may be made by any embodiment of the foregoing manufacturing method Sof a paper-based foam board that has a protective layer on each of its two sides. The sidewallextends up from and surrounds the bottom plate.

To provide the external appearance of the container structurewith a three-dimensional surface feature that shows changes in height/depth, the foam layeris formed on the outer side of the container structure. Furthermore, as the material of the foam layerhas a relatively high glass transition temperature (Tg), the foam layercan resist heat of a temperature in the range from 90° C. to 140° C.

The waterproof/oil-proof layers in the embodiments described above may be made of polyethylene, polypropylene, a water-based polyolefin, a water-based polyvinyl alcohol, a water-based acrylic resin, a water-based polyurethane resin, or another water-based resin.

The above description is based on only some preferred embodiments of the present invention and is not intended to limit the invention in any way. Although the invention has been disclosed above by way of the preferred embodiments, the embodiments are not intended to limit the invention. A person skilled in the relevant art will recognize that equivalent embodiments can be achieved by modifying, varying, or making equivalent changes to the disclosed embodiments without departing from the scope of the technical solution of the invention. Any simple modification or equivalent change that is made to the above embodiments according to the material contents of the invention shall fall within the scope of the technical solution of the invention.