Patent Application
20170361991
There are no related applications.
Not applicable.
None.
The present invention generally relates to moisture resistant and water proof paper products including linerboard and corrugated board. Particularly, this invention relates to a process and moisture resistant paper boxes made by the process for use primarily in the food industry. The corrugated board used to make the paper boxes is waterproofed by the addition of a layer of plastic film glued to a single faced liner which is impregnated with a hydrogenated triglyceride.
Corrugated paperboard is widely used as a material for constructing containers and other packaging applications. Untreated corrugated paperboard is strong, relatively inexpensive and may be recycled by composting or re-pulping. Conventional corrugated paperboard is constructed of two opposing liners and an intervening fluted medium secured between each liner with an adhesive, typically starch. The corrugated paperboard is heated to dry or cure the adhesive during its assembly on the corrugator.
Petroleum derived paraffin waxes and synthetic polymers have been used as coatings for many years in the manufacture of paper and paperboard as moisture retardants, water repellents, oil repellents, stiffeners, strengtheners, and release agents. Besides paraffin waxes, the material used most often in such products is polyethylene. However, other widely used polymers in the field include polymerized acrylics, vinyls, styrenes, ethylenes and copolymers or hetero-polymers of these monomers. The paper and paperboard to which these traditional materials are applied is difficult and often impossible recycle in standard paper mill processes because the petroleum derived polymers and, particularly, the petroleum waxes are non-biodegradable in mill white waters (circulated process waters) and discharge effluents. Furthermore, the residue of the petroleum waxes that is not removed from pulp fibers during the recycling processes causes severe operation and maintenance problems due to buildup that occurs on the screens and felts used during the process of forming and making the paper or paperboard sheet. Likewise, coatings and impregnated products made from or based on paraffin waxes and/or similar petroleum derivatives can only be re-pulped for recycling in specially configured re-pulping equipment that removes and separates the paraffin waxes. In addition, paper and paperboard coated or impregnated with petroleum waxes resist biodegradation and composting when disposed of in landfills and other waste disposal systems. Moreover, boxes containing petroleum waxes must be separated and deposited in separate landfill areas.
Paper and paperboard coated or impregnated with traditional synthetic polymers and hetero-polymers are also difficult to impossible to recycle owing to their resistance to separation from the fiber in the standard re-pulping processes resulting in significant fiber losses during efforts to re-pulp and recycle them. These coated or impregnated paper and corrugated board are also non-biodegradable and therefore resist composting.
As previously noted, water repellent packaging currently being used utilizes petroleum based liquid polymers or polymer film laminates (including polyethylene or similar film laminates such as polyolefin, polyester, polyvinyl alcohol, polyvinyl acetate, polystyrene, polypropylene, and the like) which are recyclable after extensive treatment, All of these laminates require the installation of specialized machinery that is far more expensive in terms of operating costs and/or recycled pulp fiber yields. The action of separating the fiber from the film damages some fibers causing them to be selected out of the recycled pulp while the separated film waste carries other fibers out of the re-pulpate.
The poultry box industry currently uses a wax to coat the boxes (EVA—poly (ethylene vinyl acetate) which takes a significantly long period of time to compost and leaves a chemical residue from those compounds. This process is known in the industry as curtain coating. There appears to be little or no decomposition of higher molecular weight resin and EVA fractions. Wax coated boxes are not considered to be biodegradable and do not meet the ecology friendly standards of many companies and are therefore not used by these companies.
The use of tallow to treat paper is well known in the prior art and a number of patents have attempted to use tallow to address the above noted problems. U.S. Pat. No. 2,840,138 issued Jun. 24, 1958 discloses the use of tallow fatty acids to impregnate and penetrate corrugated paper material to provide a wilt resistant material while U.S. Pat. No. 4,752,637 issued Jun. 21, 1988 is directed to a method of treating fiberboard to have moisture resistance with various mixtures of hydroxyl terminated esters such as tallow.
U.S. Pat. No. 6,103,308 issued Aug. 15, 2000 is directed toward a paper and paperboard coating composition using vegetable oil triglyceride as a paper coating while U.S. Pat. No. 6,201,053 issued Mar. 13, 2001 is directed toward various triglycerides mixed with catalysts for use as a waterproofing agent on paper coating.
U.S. Pat. No. 6,846,573 issued Jan. 25, 2005 discloses the use of hydrogenated triglycerides having a melting point above 50° as a coating material for the surface of paper products to improve wet strength and moisture resistance of the paper while allowing the paper product to being re-pulpable.
U.S. Pat. No. 7,870,992 issued Jan. 18, 2011 discloses a cardboard container having an outer shell which includes a moisture resistant barrier. The container further includes at least one insulating member disposed within the outer shell having a cellulose-based substrate substantially encapsulated in a polymeric film.
The combination of impregnation of the poultry boxes medium and liner boards with hydrogenated triglyceride and covering the outer surface of the liner boards with a dimethyl or ethylene terephthalate (PET) coating is disclosed in U.S. Pat. No. 8,455,068 issued Jun. 4, 2013. While this coating method resulted in corrugated poultry boxes which provided moisture resistance and were recyclable and re-pulpable, the boxes were only able to obtain a 30 minute Cobb value of about 20-30 causing water absorption of the boxes and structural damage to the sides and corners as well as the fold lines when the boxes were stacked for storage and shipping.
U.S. Pat. No. 4,871,406 issued Oct. 3, 1989 discloses the manufacture of a corrugated paperboard having a layer of plastic film heat laminated to the single face liner of a corrugated board. The film is supplied from a film roll and reeved over an unwrinkling device to smooth it before it is placed on the liner face. The film used for the lamination was a thermal plastic high density polyethylene (HDPE) having a heat seal layer of ethylene acrylic acid (EAA) which allowed the film to be adhered to the liner face. The '406 patent also discloses additional films which can be used for lamination such as coextruded polypropylene (PP) film and EAA or a polyester film coated with EAA. Corrugated boxes using the combined film lamination were used to package meat and poultry as well as viscous materials such as soft drinks, syrups and household chemical products.
U.S. Pat. No. 7,195,804 issued Mar. 27, 2007 discloses the manufacture of a paperboard structure adhered to a backing structure. The backing structure includes an orientated polymer film such as biaxial oriented polyethylene terephthalate film and a reinforcing scrim heat bonded together through the use of a thermal bonding layer to form a film composite.
Manufacturers have been trying to replace wax coated boxes for a number of years due to the fact that wax coated boxes do not compost and are extremely difficult to recycle.
As previously noted, the wax coated boxes are produced by a process known as curtain coating in which liquid wax is applied by pouring a curtain of wax over the exterior surface and/or interior surface of the box blank to form a uniform wax coating on the box blank.
The application of laminates to corrugated material has been undertaken for a number of years to try to solve the above noted problems with mixed success but have been unable to match the 30 minute Cobb values of wax-coated boxes which runs between 0 and 5. Furthermore, most of the lamination was done offline rather than inline which is an expensive manufacturing technique as well as incurring significant transportation costs to transport and store the offline laminated board for use on an inline corrugator.
One significant problem with non-wax coated boxes of corrugated paperboard when used for packaging of fresh poultry, seafood, meat and the like is that such boxes have a higher Cobb value over 20, typically between 40 and 80, and become wet from condensation of moisture within the box or leakage that occurs from the food product by fluid discharge from the product or melting of ice packed products. The corrugated box end corners, sides and fold lines become wet, resulting in a deterioration of box strength, box stacking capability and box tear strength leading to box crushing and tearing of the corners and sides of the boxes when the boxes are stacked.
Other problems with corrugated boxes used for fresh product shipping is that moisture from poultry, seafood and meat or other contained food product causes significant box strength weakening and provides box areas for bacterial growth and possible food contamination.
There thus exists a need for a compostable or recyclable moisture resistant corrugated food box which does not use wax or other non-biodegradable coatings. This problem has been substantially unresolved by the paper corrugating industry for the last decade.
The present invention is directed to a hydrogenated triglyceride impregnated corrugated paperboard box product comprising an inner fluted medium with laminated backer assemblies secured on opposite sides. Each backer assembly has a paper liner board sheet secured to the tips of the flutes with a starch and the outer paper liner board surface covered with a polyethylene terephthalate (PET) film glued to the outer surface of the paper liner board sheet. The PET film is glued to the paper and not heat bonded to the liner board. The inner corrugated paper fluted medium and the paper liner board sheets are impregnated with a hydrogenated triglyceride.
Hydrogenated triglycerides such as tallow can be applied to the corrugated medium and liners in the same manner as the traditional petroleum waxes and synthetic polymers and functions together with the plastic laminate as a moisture retardant, water repellent, oil repellent, stiffener and strengthener. A particular advantage in this construction is that hydrogenated triglycerides are readily biodegradable and are compostable in landfill or other waste disposal systems. The present invention is easier to re-pulp and recycle without detriment to production machinery, processes, or manufactured product quality or performance.
It is an object of this invention to produce a water resistant paper corrugated container which can be recycled without loss of fiber content.
It is another object of the invention to apply the plastic sheets of film to the liner board and secure them both together with glue rather than heat maintaining the integrity of the low temperature plastic film being used for the laminate thus increasing 30 minute Cobb values.
It is another object of the invention to provide a corrugated poultry box which is biodegradable and compostable.
It is yet another object of the invention is to produce a polyethylene terephthalate film laminated corrugated paperboard box having a moisture vapor barrier property equal or superior to wax coated paperboard, curtain coated wax boards and offline film coatings currently in use.
It is still another object of the invention to produce a recyclable water resistant poultry, seafood or meat corrugated box which has superior moisture resistance and transmission rates in a 30 minute Cobb test having Cobb values ranging from about 0 to about 1.
It is another object of the invention to provide a box surface which can be printed on and takes printing inks to provide a sharp image.
It is another object of the invention to provide a hydrogenated triglyceride impregnated fluted medium and laminated liner board corrugated box.
It is yet another object of the invention to manufacture a water resistant, recyclable laminated poultry box on an inline corrugator.
The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein.
The preferred embodiments and best mode of the invention are shown in
As used herein the following abbreviations and terms are understood to have the meanings as set forth:
The term “Hydrogenated Triglyceride” includes both animal fats and vegetable oils and is derived from one or a mixture of the animal fats and/or vegetable oils. Animal fats include beef tallow, pork lard, poultry grease and fish oils. Vegetable oils include soybean oil, peanut oil, olive oil, palm oil, coconut oil and cottonseed oil.
The term “Paper” includes substrates and surfaces of cellulosic material.
The term “PET” is a film formed from a thermoplastic resin consisting of polymerized units of the monomer dimethyl terephthalate or polyethylene terephthalate, with repeating C10H8O4 units formed in a laminating sheet.
The term “moisture resistant” means the tendency of a material to repel or not absorb or transmit liquid in normal use. The term includes moisture repellant and other terminology which means substantial water blocking capabilities or properties as opposed to total water blocking capabilities or properties.
It has been found that hydrogenated triglycerides and preferably either tallow or palm oil can be impregnated into the paper components of the corrugated board, namely, the medium and liners with the outer surface of each liner being covered with a polyester PET film which is glued to the respective liner. This combination can be substituted for petroleum based paraffin waxes and wax compounds in the manufacture of recyclable, paper products and in particular, mediums and liner board of corrugated cardboard. All of these application systems involve melted hydrogenated triglycerides held at a temperature ranging from about 125° to about 170° F. The hydrogenated triglycerides are either squeezed, rolled, cascaded, sprayed, or doctored onto the linerboard, paper, carton stock, or corrugated medium surface to impregnate the same.
Poultry boxes are unique paper container products that need to withstand water and poultry fluid.
A preferred embodiment of the inventive moisture resistant poultry box (not shown) according to the invention is constructed from a single corrugated board 11, as shown in cross section in
The corrugated medium 12 is constructed of 30 to 40 lb./1000 sq. ft. (MSF) paperboard in an “A”, “B”, “C”, “E” and “F” flute size (weight depends upon various external factors). The preferred flute size used in the invention is an “A” flute having 33+/−3 flutes per lineal foot with a flute thickness of ⅜ inch or a “C” flute having 39+/−3 flutes per lineal foot with a flute thickness of 5/32 inch.
The outer tip surfaces of the medium flutes 13 are coated with a starch 15 which is applied as is known in the art to hold the laminated liner assemblies 22 in place on the medium 12 once they engage the flute tips. Each laminated liner assembly 22 comprises a paper liner backer 14/16 upon which a plastic film 18, preferably polyethylene terephthalate (PET) having a thickness ranging from about 0.008 mm to about 0.020 mm (8 to 20 microns), most preferably about 0.008 mm to about 0.012 mm (8 to 12 microns) is glued 20 as will be described in more detail to the outer surface of the paper liners 14 and 16 to form laminated liner assemblies 22. The laminated liner assembly 22 is secured by the starch 15 applied to the flute tips of the fluted medium 12 to form the laminated corrugated board 11 used as the box blank. A cross section of the corrugated board 11 is best shown in
In operation, the laminated corrugated poultry box is constructed using standard corrugated box making machinery such as an inline corrugator which is schematically shown in
As shown in
The laminated liner assembly 122 is preferably constructed of Kraft paper 114 (various grades) with the laminated plastic PET film 112 glued thereto. The paper 114 is adhered to one side of the fluted medium 216 with a starch based adhesive to form a polyethylene terephthalate (PET) laminated backed corrugated board. The Kraft paperboard liner 114 may be bleached white, coated white (white coat), mottled white or colored. As is well known in the art, the medium paper is humidified by means of high pressure steam which softens the paper fibers to facilitate the formation of the flute and consequent gluing. The paper medium 216 is taken from roll 204 though the corrugator flute forming machine 140 as is well known in the art to make a flute of the desired size such as “A” which is attached as to the laminated backer sheet 122 noted above by starch. After formation of the board, this humidity is removed by drying in the dry-end. In the present invention, the newly formed corrugated liner board is heated by hot plates and the adhesive holding components of the structure is cured.
A second roll of paper 304, as shown in
As shown in
The laminated liner assembly 430 is run through an impregnator 177 which impregnates the liner paper 414 of the second laminated liner assembly 430 with hydrogenated triglyceride. The impregnated liner assembly 430 is carried past a heater drum 179 and a stacked heater assembly 180 where the adhesive is cured. As seen in
The PET film is applied to the outside top and bottom surfaces of the respective liner assemblies and are secured to the medium forming a laminated corrugated board. The laminated corrugated composite board 11 as seen in
The heat curing bed 190 is a series of hot plates and pressure rollers which applies light pressure and heat to cure the laminate and adhesive. The composite laminated corrugated board is then scored and cut into individual box blanks in a scoring, cutting and stacking station 200 (shown in
The poultry box blanks after being scored and cut at cutter 200, as seen in
Testing of the poultry boxes when compared with boxes without impregnated liners showed that hydrogenated triglyceride impregnated boxes had a 7% higher ECT Compression strength and retained 66% of their dry strength compression under 5 days simulated ice pack conditions as opposed to 54% of dry strength compression with non-impregnated liners. Box compression tests were at ambient temperature for simulated ice pack conditions (40 lbs. brick with 10 lbs. of ice).
As previously noted the plastic sheet used in the laminated board backer is a polyethylene terephthalate (PET) film consisting of polymerized units of the monomer dimethyl terephthalate or ethylene terephthalate, with repeating C10H8O4 units is glued to the liners of the corrugated material. PET contains the chemical elements carbon, hydrogen, and oxygen and has a tensile strength ranging from 55-75 MPa. If fully burned, it produces only carbon dioxide (CO2) and water (H2O) and contains no Sulphur. PET is commonly recycled, and has the number “1” as its recycling symbol.
The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention should not be construed as limited to the particular embodiments which have been described above. Instead, the embodiments described here should be regarded as illustrative rather than restrictive. Variations and changes may be made by others without departing from the scope of the present invention as defined by the following claims:
