Stock material or miscellaneous articles – Composite – Of carbohydrate
Reexamination Certificate
2000-07-07
2002-04-16
Parker, Fred J. (Department: 1762)
Stock material or miscellaneous articles
Composite
Of carbohydrate
C162S135000, C162S175000, C427S395000
Reexamination Certificate
active
06372361
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a paper surface treatment and compositions for the treatment of paper products which impart an oil and grease resistant barrier to such products. In particular, the invention is directed to paper products treated with a coating, more specifically, an oil and grease resistant coating.
BACKGROUND OF THE INVENTION
Coating and surface sizing of paper is conventionally used in the paper industry to provide barrier properties and other desired and beneficial attributes to paper. Properties which are provided to paper by coating compositions include porosity reduction to air, water resistance, oil and grease resistance, higher surface strength and properties which effect the quality and ease of printing on the paper.
Various materials and compositions have been used in the art to coat the surface of paper. Starch and polyvinyl alcohol have been used as components in different coating compositions. U.S. Pat. No. 4,278,583, U.S. Pat. No. 4,837,087 and U.S. Pat. No. 5,292,781 describe the use of starch and polyvinyl alcohol as binders in paper coating compositions. While the use of polyvinyl alcohol has been well documented in the patent literature, see also U.S. Pat. No. 5,849,128, its use has many drawbacks including machine runability, tackiness and unfavorable rheology.
A coating composition which is widely used commercially to impart oil and grease resistance to paper contains fluorochemicals. While such coating compositions are quite effective, they are not environmentally friendly and raise various health and safety concerns.
There is thus a need in the art for coating compositions for use in the production of oil and grease resistant papers, in particular paper products used for food packaging, which is safe for the environment and the consumer.
SUMMARY OF THE INVENTION
The present invention fulfills this need by providing a paper coating composition for oil and grease resistance that is formulated from food grade ingredients, so is both environmentally friendly and safe for the consumer.
The invention relates to a paper coating composition that provides good barrier properties. The paper coating composition of the invention comprises a hydrophobically modified non-high amylose starch wherein the starch base material is a native starch having an amylose content of less than about 40% by weight and the starch is modified with a hydrocarbon group of 6 to 18 carbon atoms.
One aspect of the invention is directed to a paper product resistant to oil and grease having a coating which comprises a hydropbically modified starch having an amylose content of less than about 40% by weight wherein the fluidity of the base starch has a gel strength of greater than 500 grams/in
2
.
The paper products of the invention preferably comprise a coating containing a modified starch having the formula:
where St is a starch having an amylose content of less that about 40%, R is dimethylene or trimethylene, R′ is a hydrocarbon group of 6 to 18 carbon atoms and Y is H, alkali metal, alkaline earth metal or ammonium.
In a preferred embodiment, the paper product is a food container.
Yet another aspect of the invention is directed to a method of preparing a coated paper product having good barrier properties comprising
a) providing a coating composition comprising a hydrophobically modified starch having an amylose content of less that about 40% by weight and wherein the fluidity of the starch prior to modification has a gel strength of greater than 500 grams/in
2
,
b) applying the coating composition to a paper substrate, and
c) drying the coated substrate to remove moisture and provide the coated paper product.
A preferred coating for use in the practice of the invention is an aqueous solution having a total solids content of from about 2 to about 25% by weight.
DETAILED DESCRIPTION OF THE INVENTION
The disclosures of all references cited herein are incorporated in their entireties by reference.
The term “coating” as used herein, refers to any surface treatment applied to paper. “Barrier” properties refer to an increase in the resistance of paper to various materials such as air, oil, grease, and also higher surface strength. The composition of the invention provides a paper surface treatment composition comprising a hydrophobically modified, high gel strength starch that when applied to paper products provides an especially good barrier to oil- and grease-like materials.
Paper products are defined herein as any article of manufacture, at least a portion of which comprises paper coated in accordance with the invention. The paper product may be made totally of paper or partially of paper. The invention encompasses paper products made of either single or multiple layers, e.g., a paper laminate, plastic/paper laminate. The coating may be applied on one or both sides, and may be coated on the side to be laminated. As the coating is made of food grade ingredients, paper products designed to receive food may, if desired, be coated on the side which will be in direct contact with food.
Paper products to be treated with the composition of the invention or made with paper treated in accordance with the invention include, but are not limited to laundry soap boxes, fabric dryer sheet containers, industrial wraps and food containers. As the composition of the invention is formulated from food grade ingredients, a preferred embodiment will be food containers. Food containers are defined herein as including any wrapper, bag, box, cup or other paper product capable of covering, holding or containing a food product, whether hot or cold, wet or dry. Examples include but are not limited to hamburger wrappers, candy wrappers, pizza and cereal boxes, and bags for potato chips, peanuts and pet food.
The coating composition of the invention comprises a hydrophobically modified non-high amylose starch. The starch is hydrophobically modified with hydrocarbon groups of at least 6 carbon atoms, preferably 6 to 18 carbon atoms, and preferably 8 to 12 carbon atoms. This hydrophobically modified starch can be prepared by reacting starch and an organic anhydride reagent and has the formula:
where St is the non-high amylose starch base material, R is a dimethylene or trimethylene group, R′ is a hydrocarbon group of 6 to 18 carbons and Y is H, alkali metal, alkaline earth metal or ammonium. The hydrocarbon or hydrophobic substituent group R′ may be alkyl, alkenyl, aryl, aralkyl or aralkenyl, preferably alkyl or alkenyl and more preferably alkenyl.
Preferred organic anhydrides include octenyl succinic anhydride, dodecenyl succinic anhydride and hexadecenyl succinic anhydride. While octenyl succinic anhydride (OSA)-modified starch, e.g., OSA-modified tapioca, is one preferred embodiment, and is exemplified herein, the invention is not limited thereto.
The amount of the derivative group bound to the starch, i.e.,
will be from about 1 to 10% and preferably from about 2 to 3% by weight, based on the weight of dry starch.
It is well known that starch is composed of two fractions, the molecular arrangement of one being predominantly linear and the other being highly branched. The linear fraction of starch is known as amylose and the branched fraction amylopectin. Starches from different sources, e.g. potato, corn, tapioca, sago, rice, etc., are characterized by different relative proportions of amylose and amylopectin components. Some plant species have been genetically engineered or modified by classical hybrid breeding and are characterized by a large preponderance of one fraction over the other.
The starch material used as the starting base material in this invention will be a non-high amylose starch, i.e. one containing less than about 40% by weight of amylose. By “base” starch is meant raw or native starch, i.e., starch as it comes from the plant source. Such base starch include natural starches as well genetically altered and hybrid starches. Suitable starches which may be used to practice the invention are any starches with an amylose content of less than about 40%, pa
Billmers Robert L.
Hanchett Douglas J.
Mackewicz Victor L.
Duncan, Esq. Laurelee
National Starch and Chemical Investment Holding Corporation
Parker Fred J.
Tsoy Elena
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