FOOD TRAY AND PROCESS FOR MAKING SAME

Abstract

A repulpable moisture resistant protein tray formed of thermo-molded pulp comprised of recycled paper pulp impregnated with a hydrogenated triglyceride. The protein tray has an outer surface coated with an emulsion of styrene acrylic to provide a moisture resistance repulpable and recyclable tray. The protein tray has a flat bottom and an integral sidewall forming an interior volume. An integral edge extends peripherally outward from an upper edge of the sidewall forming a substantially oval shape.

Claims

1. A repulpable moisture resistant and recyclable protein tray formed of thermo-molded pulp having a planar base and an integral sloped sidewall forming an interior volume, said tray comprising a thermo-molded structure made of a pulp mixture derived from DLK (double lined kraft) clippings impregnated with hydrogenated triglyceride, said molded tray having an exterior surface coated with a polymer having characteristics which provide moisture resistance and wet strength to said molded tray, said molded tray being repulpable and recyclable.

2. The repulpable moisture resistant molded protein tray of claim 1 wherein the hydrogenated triglyceride of said recycled paper is a hydrogenated vegetable oil selected from the group consisting of soybean oil, peanut oil, olive oil, palm oil, coconut oil and cottonseed oil.

3. The repulpable moisture resistant molded protein tray of claim 1 wherein the hydrogenated triglyceride of said recycled paper is an animal fat selected from the group consisting of beef tallow, pork lard, poultry grease, and fish oils.

4. The repulpable moisture resistant molded protein tray of claim 1 wherein said coating polymer is a water based polyester.

5. The repulpable moisture resistant molded tray of claim 2 wherein said protein tray is directed toward protein consisting of poultry, seafood and meat.

6. The repulpable moisture resistant paper tray of claim 1 wherein sidewall is two separate contiguous sloped sections comprising an upper sloped section from at an about 70° to about 80° angle from a plane drawn across said peripherally extending flange and a lower sloped section formed at an angle about 50° to about 70° from said plane drawn across said peripherally extending flange.

7. A repulpable moisture resistant paper container comprising a thermo-molded composite container made of pulped DLK containing hydrogenated triglyceride, said container defining a base, an integral outwardly sloped sidewall extending upward from said base, a flange extending outward from an upper edge of said sloped sidewall, said flange, sidewall and base having a surface coated with an emulsified mixture of styrene acrylic to provide moisture resistance and wet strength to said thermo-molded container, said thermo-molded container being repulpable and recyclable.

8. The repulpable moisture resistant paper container as claimed in claim 7 wherein said base is planar and said flange defines a planar surface parallel with said planar base with outward edge of said flange being bent downward from a plane drawn across said flange at an angle in a range of about 50° to about 70°.

9. The repulpable moisture resistant paper container of claim 8 wherein sidewall is two separate contiguous sloped sections comprising an upper sloped section from at an about 70° to about 80° angle from a plane drawn across said peripherally extending flange and a lower sloped section formed at an angle about 50° to about 60° from said plane drawn across said peripherally extending flange.

10. The repulpable moisture resistant paper container of claim 8 wherein said paper container is a single compartment tray formed of said mixture of thermo-molded pulp defining a planar base and an integral sloped sidewall forming an interior volume, the tray further comprising an integral flange having a planar surface extending peripherally outward from an upper edge of said sidewall.

11. A process for making a repulpable and recyclable food tray comprising the steps of: a). mixing a recycled pulp medium previously treated with hydrogenated triglyceride (HT); b). adding Ulterion 2050 to the pulp medium;; c). thermo-molding the homogenous mixture into trays; d). coating each molded tray with at least one coating of polyester; and e). drying said each coated tray with a heater dryer to dry said coating.

12. A process as claimed in claim 11 wherein said polyester is in a water solution and is applied at about 7 grams wet weight to the top surface and bottom surface of the tray.

13. A process as claimed in claim 11 wherein step d) coating is done by spraying.

14. A process as claimed in claim 11 wherein said polyester coating is a styrene acrylic.

15. A process for making a repulpable and recyclable food as claimed in claim 11 wherein the drying step e) comprises: heating each coated tray from about 300° F. to about 350° F. to dry the polymer coating for a period ranging from about 10 seconds to about 15 seconds.

16. A process for making a repulpable and recyclable food tray as claimed in claim 11 including an additional step f) of stacking said cured coated trays in stacks having a specific number of trays.

17. A process for making a protein container comprising the steps of: a). mixing a recycled paper pulp medium previously treated with hydrogenated triglyceride (HT) into a homogenous slurry; b). thermo-molding the homogenous slurry into protein containers; c). coating each molded protein container with at least one coating of polymer; d). curing said each coated container with a heater dryer at a temperature ranging from 300° F. to about 350° F. for a time suitable to dry the coating to cure said coating; and e). stacking said dried coated poultry containers in stacks having a specific number of containers.

18. The process for making a protein container as claimed in claim 17 wherein said paper pulp medium is in the form of cardboard clippings taken from cardboard containing hydrogenated triglyceride.

19. The process for making a protein container as claimed in claim 17 wherein said polymer coating is a polyester.

20. The process for making a protein container as claimed in claim 17 wherein said polymer coating is an acrylic styrene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 is a perspective view of a prior art poultry tray;

[0038] FIG. 2 is an enlarged cross sectional view of the prior art poultry tray of FIG. 1 taken along line 2′-2;

[0039] FIG. 3 is a top plan view of the inventive food tray invention;

[0040] FIG. 4 is an enlarged cross sectional view of the inventive food tray of FIG. 3 taken along line 4′-4; and

[0041] FIG. 5 is a schematic of the process used in making the inventive thermo-molded coated food tray;

DETAILED DESCRIPTION OF THE INVENTION

[0042] The preferred embodiments and best mode of the invention are shown in FIGS. 3 through 5. While the invention is described in connection with certain preferred embodiments, it is not intended that the present invention be so limited. On the contrary, it is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims.

Definitions

[0043] As used herein the following abbreviations and terms are understood to have the meanings as set forth:

[0044] The term “Triglyceride” includes both animal fats and vegetable oils and is derived from one or both of them. 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.

[0045] The term “Paper” includes substrates and surfaces of cellulosic material.

[0046] The letters “DLK” (double lined kraft) refer to clippings from cardboard boxes when the same are trimmed and cut out in the box making process.

[0047] GREENCOAT® is a registered trademark which identifies paper and cardboard coated and/or impregnated with hydrogenated triglyceride which when repulped still contains cellulosic fibers containing hydrogenated triglycerides.

[0048] The method and machinery or equipment for repulping and recycling scrap paper in the paper and paperboard or liner board industry is both an established and well known art, and the equipment required is standard and commonly installed at most mills incorporating recycled paper in their manufacturing feed stocks. Thus, those skilled in the paper making art are also knowledgeable in re-pulping and recycling.

[0049] Protein trays are unique paper products that need to withstand leakage of water and fluid from the contained food. Typical use of such trays includes holding poultry, seafood, and meat. The present food tray matches or exceeds equivalent Styrofoam® trays with an acceptable strength with a minimized rim width to reduce fingernail punch through.

[0050] The present repulpable degradable thermo-molded poultry tray 10 is constructed of a mixture of recycled paper and cardboard clippings (DLK) coated and/or impregnated with hydrogenated triglycerides. Hydrogenated triglycerides typically used for coating and impregnation of paper products are animal fats and 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 pulp used for the pulp mixture forming the composition of the molded food containers is preferably about 100% hydrogenated triglyceride impregnated cardboard clippings (HTIC) DLK. A food container made of 100% (HTIC) pulp has superior strength to a food container made of 100% OCC pulp. The percentage is shown in Table I on page 13.

[0051] The paper pulp mixture is pulped and diluted into a slurry consisting of a low percentage of pulp which is well known in the art. The slurry is pumped into a mold tool where it is thermo-molded into a tray 10 having a wall thickness ranging from about 1/16 inch to about ¼ inch. The tray 10 is formed in heat forming molds which form the molded tray products which have the appearance of plastic material. The trays 10 are ejected from the heated mold in a semi-finished state and carried through a spray conveyor. The trays are coated on the exterior top and bottom surfaces of the tray with a polyester or copolymer, preferably styrene acrylic as shown in FIG. 5 by spray nozzles for a spray time of three seconds to 3½ seconds. The tray is sprayed on the top and bottom surfaces with about 3.0 to 3.5 grams on each side of a polyester or a copolymer styrene acrylic coating solution prior to entering the IR drying section where curing and drying takes place. The total wet coat weight of the polyester coating is about 7 grams. The trays 10 leave the sprayer and are dried on an IR drying conveyor at a temperature ranging from 300° F. to 350° F. for 5 to 10 seconds.

[0052] The tray 10 is preferably a simple compartment tray having a plane A taken across planar surface 24 of an opposing rim or flange 20 as seen in FIG. 4. The tray has a flat bottom 12, a continuous sidewall 14 with an upper sloped section 16 sloped inward at about a 70° to about a 80° (angle B), preferably 75°, taken from a line B′-B′ which is perpendicular to the planar horizontal line A and an integral second lower sloped portion 18 sloped inward about 50° to about 60° (angle C), preferably about 50°, taken from a line C′-C′ which is perpendicular to the same planar horizontal line A. Both sections 16 and 18 are integrally connected together by an arcuate intermediate section 17. The flange 20 allows for sealing the top of the tray 10 with a lidding film (not shown). The integral two stage sloping sidewall gives greater strength to the tray as well as providing a minimized area exposed to finger punch-thru risk. The sidewall 14 and bottom 12 form an interior volume of a substantially rounded rectangular shape of the tray. The flange or rim 20 is integrally formed with the upper edge of sidewall section 16 and extends peripherally outward. The flange end tip 22 is bent downward approximately 60° from a planar line A. The flange 20 allows a minimum deflection of the tray 10 during wrapping and resists puncture. The exterior dimensions of the tray range from 0.5-1.75 inches high, 5 to 8 inches wide and 8 to 15 inches long. It has been found that clippings from hydrogenated triglyceride containing cardboard converted to pulp to and then thermo-molded is stronger than a tray made of 100% DLK pulp made from untreated cardboard. The HTIC pulp when formed into the present protein tray provides a substitute for Styrofoam® trays presently in the marketplace.

[0053] The inventive pulp protein tray disclosed above is equivalent to the strength of a Styrofoam® tray.

TABLE-US-00001 TABLE I Test Results Indexed to 176 g/m.sup.2 Basis Weight Ring Crush STFI Taber Stiffness Mullen (lb/in) (lb/in) (Taber Stiffness Units) Burst Sample ID MD CD MD CD MD CD (psi) 100% dry clippings DLK 70.38 37.54 23.44 8.05 107.11 40.99 60.77 100% Greencoat ® 78.6 41.24 25.96 8.38 117.48 41.31 63.19 (+1.2%) (+1.0%) (+1.1%) (+0.4%) (+1%) (+0.1%) (+0.4%)

[0054] In the present Table I shown above, the base reference is made to a 100% paper sheet and a 100% GREENCOAT® or HTIC paper sheet. The term GREENCOAT® is a registered trademark of Interstate Corrpack LLC and is used to designate a recyclable cardboard liner board and corrugated cardboard which is impregnated with hydrogenated triglycerides or coated with a copolymer styrene acrylic which is used on various GREENCOAT® paper products sold by Interstate Corrpack LLC.

[0055] It was surprisingly found that a tray of a 100% HTIC pulp mixture had a Ring crush, strength and stiffness which was greater than a tray of a standard DLK pulp mixture. This GREENCOAT® paper material was about 12% greater in the machine direction Ring Crush tests (compression strength) and 10% stronger in the cross direction than 100% normal DLK. Both the machine direction and cross direction of the STFI test was higher than that of the 100% normal DLK. The HTIC paper material also was about 10% greater in the machine direction for Taber Stiffness (flexural rigidity) and 5% greater in the Mullen Burst (psi) test than 100% standard paper material. The Mullen Burst (psi) relates to puncture resistance.

[0056] At the end of the pulping process, but before the molding begins, chemical additives are added to the pulp such as Ulterion 2050 and Ulterion 2100. The typical sequence would be to add the Ulterion 2050 first from vat 50 by selection valve 53, and then add the Ulterion 2100 from vat 52 and then mixed in blender 54 with the HTIC slurry. The mixture passes through line 55 into the pulp storage tank 56. Additionally, PAC (polyaluminum chloride) and AKD (alkyl ketene dimer) are added to assist the Ulterion products in adhering to the paper fibers.

[0057] Following the pulping and mixing process, the pulp is diluted to a low consistency of fibers. This can be done in a holding tank 56. Once the target consistency is reached, the slurry is pumped to the thermoforming machines or forming dies 58 via pump 57 where the trays are formed and fluid removed by vacuum pump 60 into storage tank 62. After the trays are formed, they are conveyed 64 to the spraying section.

[0058] A coating is applied to the outer upper surface area of the molded tray shown in FIGS. 3 and 4 and the bottom surface of the tray. The coating is a water based polymer such as a polyester (Ulterion 535). The coating is fast drying, recyclable, repulpable and is printable. After the spray application, the tray coating was dried in an IR heater at a temperature range from about 300° F. to about 350° F. for 5 to 10 seconds to cure and dry the polymer on the fibers of the thermo-molded tray. There is no sticking of the trays when the trays are stacked.

[0059] After the trays leave the sprayer coater 66, they are placed onto the IR drying oven conveyor 68 using compressed air or other transportation means such as a slide or adjacent transport conveyor and are dried. The trays are cured in the IR conveyor oven dryer 68 to cure the polymer coating. The trays travel through the conveyor oven 68 which is heated at about 300° F. to about 350° F. The coated dried trays can optionally be carried by conveyor 70 from the conveyor oven 68 to an automatic stacker 72 which stacks the trays for shipment.

[0060] The wrapping material (not shown) for the tray can be any conventionally used and available film overwrap. One example is Cryover BDF-2001 film that is a coextruded polyolefin shrink film. If desired, the overwrap can be a clear plastic film allowing the food product contained in the tray to be seen and displayed in the packaging.

[0061] 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: