WO2013106564A1 - Dual-smooth molded pulp forms and shapes and method of making - Google Patents

Abstract

Most pulp molded shapes when processed have one smooth side and one rough side. WE have formulated a method of manufacturing pulp molded shapes having two smooth, and generally opposing, sides. Discarded pulp molded shapes are repulpable and, thus, the fibers in the molded articles can be recovered and recycled. Pulp molded articles can take the form of food packaging containers, food preparation and serving trays, and other useful pulp molded articles. Therefore, the invention contributes to the green presentation to the food packaging industry as well as to the ultimate consumer.

Description

DUAL-SMOOTH MOLDED PULP FORMS AND SHAPES AND METHOD OF MAKING BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to pulp molded articles having opposed surfaces which are each smooth. The articles can take the shape of food preparation and serving containers, food packaging containers, egg crates and similar articles molded from pulp. A method of making the pulp articles is also disclosed.

2. Description of Related Art

Articles molded from pulp (a mixture of cellulosic fibers and optionally fillers, colorants, sizing agents in a liquid, normally water) are known in the art. See for example, U.S. Patent 4,088,259, the entire disclosure of which is herein incorporated by reference. Such articles are easy to mold by introducing the pulp into porous molds whereby the liquid, e.g., water, is drawn, suitably with the application of a vacuum to the mold, through the porous moid, the solids (cellulosic fibers, fillers, etc.) depositing as a molded shape in the forms. The molded shapes can be dried either in the molds or removed from the molds and dried in air. Although the pulp molded articles can be recycled by beating the articles in water to form a new pulp, the articles, as molded, have one smooth side (adjacent the mold surface) with the opposing side (away from the mold surface) being rough. Attempts at coating the rough side to form a smooth surface have resulted in additional steps and expense and diminished the ability of the molded pulp articles to be repulped.

Thus, there exists a need in the art for pulp molded articles which have smooth opposing sides, and are still repuipable and therefore recyclable.

SUMMARY OF THE INVENTION

The invention is directed to pulp molded articles having two sides, each of which is a smooth surface. Generally the two smooth sides will be opposing surfaces, but the invention is applicable to intricate shapes where the smooth sides are not opposing surfaces. A method of forming such pulp molded articles is also described.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic depiction of a prior art pulp molded article, such as an egg crate, having one smooth surface and an opposing rough surface;

Fig. 2 is a schematic representation of a pulp molded article having opposed smooth surfaces; and,

Fig. 3 is an exploded view of a pulp molded article having opposed, smooth surfaces, made according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in Fig. 1, a pulp molded article, such as an egg crate, is molded by the conventional pulp molding process of depositing a pulp (cellulosic fibers and an excess of water) against a porous mold surface to draw the water through the mold surface leaving behind the fibers consolidated into a molded article. However, the resultant article 12 will have one smooth side 46 (adjacent the mold surface) with the opposing surface 42 being rough. Even if the molded article is formed with an appendage, such as lid 34, attached to the article 12 by a hinge 20, the lid 34 will have one smooth surface 18 (adjacent the mold surface) and an opposing rough surface 38. While such pulp molded articles have utility as an egg crate, when a consumer handles a food preparation and serving tray, or purchases a product in a pulp molded food container, the presence of the rough surface may leave the impression of poor quality, unsanitary construction, and an undesirable feel in the hands of a consumer.

Thus, the present invention, such as a pulp molded food preparation and serving tray 10 as shown in Fig. 2, having opposed surfaces 34, 36, can each be made smooth by the following steps of manufacturing. The tray 10 may have several compartments 30, 32, 0, 41, 38 and 39 for separately holding different foods of a meal. Two pulp molded shapes are formed as shown in the exploded view of Fig. 3, where smooth surface 34 of a first ply 10A is formed against a first porous mold surface and smooth surface 36 of a second ply 10B is formed against a second porous mold surface. Elements 52 and 53 of ply 10B are the complement to elements 38, 39, respectively, of ply 10A, as are shapes 54, 55 complementary to comparments 40, 41, respectively of ply 10A. The plys 10A and 10B are then laminated in such a way that surfaces 34 and 36 are each facing outward of the finished tray 10, by the use of an adhesive 50 that does not interfere with the ability to repulp the pulp molded articles.

We have found that a suitable adhesive is a polyethylene containing composition in combination with an acrylic acid or methacrylic acid moiety containing polymer, such as that sold under the trademark Spectra-Guard HS, available from Spectra-Kote Corporation of Gettysburg, Pennsylvania. The polymer can be used with a cross-linking agent, such as a titanium dioxide suspension in water. We prefer to use a methyl meth(acrylate) (PMMA) as the polymer, but other acrylic or methacrylic-based copolymers, homopolymers, oligomers or monomers can be used to form the adhesive having repulping qualities suitable for use in the invention. The adhesive can be applied in any conventional manner as a separate ply as shown in Fig. 3, or by coating it on one, or both, of plys 10A, 10B. Coating techniques include rod coating, spraying (including electrostatic spraying), dipping, falling curtain, air-knife and other coating techniques.

The cellulosic fibers can be virgin or recycled wood fibers or a mixture of the same. The liquid used is prefereably water, but may have conventional fillers, pigments, dyes, sizing agents and other components used in the pulp molding art. A small proportion of fibers other than wood may be included, including polymeric, metal, or ceramic fibers. Such other fibers may assist in using the molded articles as microwavable food preparation containers, or convection oven food preparation, containers.

While we have provided a description of preferred embodiments of our invention, it should be understood by those skilled in the art that our invention is not limited to those preferred embodiments as other embodiments will be envisioned by those skilled in the art upon reading this disclosure.

Claims

We Claim:

1. A pulp molded article having two smooth sides.

2. The pulp molded article of claim 1, wherein the smooth sides are opposing surfaces.

3. A pulp molded product having two smooth outwardly facing surfaces formed by the process comprising the steps of:

pulp molding a first ply to obtain a shape having a smooth surface and a rough surface;

pulp molding a second ply to obtain a shape having a smooth surface and a rough surface; and,

laminating the plys together with an adhesive that permits repulping the molded product in such a way that the smooth surfaces are each facing outward.

4. A method of manufacturing a pulp molded article comprising the steps of:

pulp molding a first ply to obtain a shape having a smooth surface and a rough surface;

pulp molding a second ply to obtain a shape having a smooth surface and a rough surface; and,

laminating the plys together with an adhesive that permits repulping the molded product in such a way that the smooth surfaces are each facing outward.