Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1997-09-29
2001-09-04
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S035600, C428S036900, C428S304400, C428S317900, C428S318400, C428S323000, C428S532000, C428S537500, C428S906000, C264S051000, C264S176100, C264S209100, C264S211000, C264S211100, C521S056000, C521S079000, C521S084100, C521S088000, C521S916000
Reexamination Certificate
active
06284359
ABSTRACT:
This invention relates to biodegradable, water soluble and dispersible, expanded or foamed shaped products which are extruded from starch and are particularly suited for use as the cores in the winding or rolling and storage of paper goods.
Rolled paper goods, such as toweling, tissue and wrapping papers are typically held on a wound paper core. The paper core provides structure and acts as a support for the rolled or wound paper. Emphasis on environmental concerns has made it highly desirable to use products which are either biodegradable and readily disposable or recyclable. While paper is repulpable and recyclable, the products using paper cores generally contain an adhesive or glue making it difficult to process in a repulping operation.
Starch, a readily available known biodegradable material, has been used to prepare foamed, film and other shaped products for different purposes including selected packaging applications. Some of these starch products and their uses are described in U.S. Pat. Nos. 5,035,930 and 5,043,196.
Extrusion is a well known technique, widely used in forming plastic materials into various foamed and expanded products. More recently, the extrusion of starch into expanded articles has shown increased interest as noted in the aforementioned '930 and '196 U.S. patents which disclose the extrusion of high amylose starch into low density packaging materials. Other disclosures of forming starch products by extrusion can be found in U.S. Pat. No. 5,248,702 directed to packaging fillers and in U.S. Pat. No. 5,314,754 involved with the formation of shaped products from a starch hot melt.
The biodegradable, starch-containing packaging materials known in the art are typically prepared to be water-resistant rather than water-dispersible. Furthermore, not much attention has been directed to the preparation and production of structured starch articles such as expanded core products, which require demanding properties including dimensional stability and structural strength. Thus, there remains a need for biodegradable products which are also water soluble and water dispersible and further meet the physical and structural requirements demanded in paper core applications.
SUMMARY OF THE INVENTION
The present invention provides a biodegradable, water dispersible shaped core product having good dimensional stability and structural strength properties comprising an expanded, closed cell starch product wherein the product is formed by extruding starch which has a selected particle size. More particularly, the expanded starch product of this invention is a water dispersible, shaped product made by extruding starch having a particle size of from 400 to 1500 microns.
DETAILED DESCRIPTION OF THE INVENTION
The ability to provide biodegradable, water dispersible shaped starch core products for use in the winding or rolling and storage of paper goods is the main objective of this invention. The term “core” product as used herein refers to products having relatively large configurations or shapes and includes tubes or inserts, spools and supports used for rolled paper goods such as tissues and towels and may even be used for rolling and holding other fabric materials. The core may be solid or tubular and the dimensions can vary depending on the particular use and operation in which it is being used. Generally dimensions of up to 3.0 inches or more, inner and outer diameters and lengths of up to 240″ or more may be used. In the tissue application area, typical dimensions include inner diameter of about 1.5″ and outer diameter of about 1.75″ with a length of about 120″. These dimensions as noted, depend on use and will vary, for example in the paper area depending on the winding and cutting equipment in which it is used.
The formation of shaped starch products by extrusion is becoming of more interest and has been described many times in the recent literature as noted previously. Most of the disclosures have been involved with providing shaped fillers and random or smaller packaging materials such as discrete loosefill products, sometimes called peanuts, or very small sheets. The ability to extend this processing concept to the formation of bigger or larger starch shaped products, such as cores for paper products, has not been a simple or direct extension of the known technology. This is because the chemical nature of starch is quite different from the various plastic and synthetic materials, such as styrene and polyethylene, that have been extruded into shaped products for many years. Additionally, while the rheology of starch extrusion to form smaller loosefill type products is similar in some respects to the extrusion of larger structured or core products, it is also different or lacking in other properties or aspects. Along these lines, it is noted that the extrusion of starch to produce foamed core products generally requires dies with large openings or increased cross sectional areas. This means higher throughput or feed rates to satisfy pressure, fill rates and other rheological properties needed to produce products with suitable properties. One significant variation is that of cell structure in the resulting product.
In order to provide suitable extrusion properties and particularly the needed high feed rates and threshold throughput in forming desired core starch products, it has been found that the feed starch particle size is an important factor. A significantly large and defined particle size has been found especially advantageous in providing desirable extrusion processing conditions and resulting product properties. The useful particle size is large and in a defined range of from about 400 to 1500 microns and more particularly from about 800 to 1200 microns. When using starch feed material with this defined particle size, the extrusion processing conditions including feed rate and pressure, plus needed cell structure in the formed product were more readily attainable to provide the core product of suitable characteristics.
In order to obtain the starch feed material having the necessary particle size in accordance with this invention, a method known as compact granulating, commonly referred to as chilsonating, may be used. Other methods to attain desired starch particle size may also be used provided substantially all of the starch feed material is within the prescribed size range.
Another feature which improves processing and the properties of the resulting structured starch products is the addition of a nucleating agent or salt to the starting starch feed material. This is especially helpful when dies of increased and large open areas or cross section are used and particularly improves the cell structures of the expanded product. Various nucleating agents or salts may be used in this capacity including any inorganic, water soluble salt or mixtures thereof and especially an alkali metal or alkaline earth metal salt such as sodium sulfate and sodium chloride. Other nucleating agents such as microtalc can be used but the alkali metal or alkaline earth metal salts are preferred. The amount of nucleating agent used will depend on particular processing conditions and desired extruded product dimensions, with at least 1%, more particularly from 1 to 8% and preferably from 1 to 6% by weight of nucleating agent, based on the weight of starch in the feed composition, being used. In general, the higher amounts of nucleating agent have been found very beneficial when using large die openings needed to produce the structured or core starch products. It is further noted that the nucleating agent or salt can be added to the feed starch or in certain circumstances may be present as residual salt or ash content in the already prepared starch. The combination of defined starch particle size and the addition of nucleating agent, as defined herein, has been found to be especially advantageous in producing the core foam starch products in accordance with this invention.
The starting estarch material useful in this invention may be any of several starch
Altieri Paul A.
Rose Richard R.
Tormey Beth C.
Chen Vivian
Duncan, Esq. Laurelee
National Starch and Chemical Company Investment Holding Corporat
Zagarella, Esq. Eugene
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