Repulpable corrugated protein box and process for making same using wire side impregnation

Abstract

A repulpable moisture resistant protein box having a composite structure with a fluted medium, a top backing board secured to one side of the fluted medium and a bottom backing board secured to the other side of the fluted medium. The backing boards are impregnated with a hydrogenated triglyceride on the wire side and the fluted medium is also impregnated with a hydrogenated triglyceride. The backing boards each have an outer felt side surface coated with styrene acrylic co-polymer. The protein boxes have a higher compression, moisture resistance and are recyclable.

Claims

1. A process for making a repulpable and recyclable protein box comprising the steps of: a) impregnating a corrugated paper medium with hydrogenated triglyceride (HT); b) impregnating a first paper liner board solely through its wire side with HT; c) impregnating a second paper liner board solely through its wire side with HT; d) coating said impregnated first paper liner board on its felt side with a coating which is a styrene acrylic co-polymer solution having 40% to 70% solids; e) coating said impregnated second paper liner board on its felt side with a coating which is a styrene acrylic co-polymer solution having 40% to 70% solids; f) securing said first impregnated and coated liner board, said corrugated medium and said second impregnated and coated liner board together with an adhesive to form a composite sheet; and g) curing said composite sheet.

2. A process as claimed in claim 1 wherein said hydrogenated triglyceride is beef tallow is 100% by weight.

3. A process as claimed in claim 1 wherein said hydrogenated triglyceride is palm oil.

4. A process as claimed in claim 1 wherein said adhesive is a starch solution.

5. A process as claimed in claim 4 wherein said starch adhesive has a solid content ranging from about 25% to about 35%.

6. A process as claimed in claim 1 wherein the hydrogenated triglyceride is an animal fat selected from one or more of a group consisting of beef tallow, pork lard, poultry grease, and fish oils.

7. A process as claimed in claim 1 wherein the hydrogenated triglyceride is a hydrogenated vegetable oil selected from one or more of a group consisting of soybean oil, peanut oil, olive oil, palm oil, coconut oil and cottonseed oil.

8. A process for making a repulpable and recyclable protein box as claimed in claim 1 wherein the protein box is a poultry box.

9. A process for making a repulpable and recyclable protein box as claimed in claim 1 including the step of: a) cutting the composite sheet into blanks.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic of the process used in making the protein boxes; and

(2) FIG. 2 is an enlarged cross sectional view of the inventive protein box invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) The preferred embodiments and best mode of the invention are shown in FIGS. 1 and 2. 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.

(4) Definitions

(5) As used herein the following abbreviations and terms are understood to have the meanings as set forth:

(6) “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.

(7) “Paraffin” is a wax-like product derived from petroleum.

(8) “Paper” includes substrates and surfaces of cellulosic material.

(9) It has been found that hydrogenated triglycerides and styrene acrylic co-polymer can be substituted for petroleum based paraffin waxes and wax compounds in the manufacture of paper food boxes, and when these paper boxes are impregnated on the wire side and coated on the felt side, they have superior compression strength, hot melt glue strength, and slide resistance. These application systems involve melted triglycerides held at temperatures in a range from around 170° F. to 190° F. which is either squeezed, rolled, cascaded, sprayed, or doctored onto the wire surface of the linerboard, paper, carton stock, or corrugated medium surface to impregnate the same.

(10) 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.

(11) The paper liners or paper backers for the corrugated boards have two opposite sides commonly referred to as the felt side and the wire side. In the manufacturing of paper, pulp is initially deposited on a screen which gives the name (wire side) to that side of the paper. After the pulp is deposited on the screen, it is pressed with felt pads to force the water out of the pulp and compress the fibers into the paper form. This side is called the felt side.

(12) Protein boxes are unique paper products that need to withstand water and poultry fluid. The present inventive protein box is made of double backer corrugated board having a corrugated medium of 30 to 40 lb./1000 sq. ft. (MSF) paperboard of 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. A flat liner or backer board of Kraft paper (various grades) is adhered to one side of the fluted medium with a starch based adhesive and a second flat liner or backer board of Kraft paper is adhered to the other side of the fluted medium with a starch based adhesive to form a backed corrugated board. The Kraft paperboard liner 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. 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 from the bottom by hot plates and the adhesive holding components of the structure are cured.

(13) The present degradable protein box 10 is constructed with an inner Kraft paper liner or backer 12 impregnated through the wire side with a hydrogenated triglyceride, preferably beef tallow at 2.0 to 3.0 lbs/MSF, a corrugated paper medium 14 impregnated with a hydrogenated triglyceride, preferably beef tallow at 3.0 to 3.5 lbs/MSF and an outer Kraft paper liner or backer 16 impregnated through the wire side with beef tallow at 2.0 to 3.0 lbs/MSF or other materials which are discussed. Other hydrogenated triglycerides can be used such as 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 preferred vegetable oil which is used for impregnation is palm oil. Beef tallow used in the impregnation is commercially available from Chemol Corporation. After beef tallow impregnation of the wire side of the paper liners, both liners or backers 16 are coated on their felt side surfaces with a coating 18 having 40% to 70% preferably 50% solids in a styrene acrylic co-polymer solution.

(14) The present protein box 10 is constructed using standard inline corrugated box making machinery as is well known in the art. A roll of the medium paper 30 is positioned upstream of the corrugator. The paper is wetted and passed through a standard corrugating machine 35 and formed into a corrugated medium 32 having the desired flute size, preferably “A” or “C”. The corrugated medium 32 is transported downstream through a hydrogenated triglyceride bath 36 (preferably beef tallow) and rollers with the corrugated medium being impregnated with beef tallow at 2.0 to 3.5 lbs/MSF. The impregnated corrugated medium 37 is carried by belts to an assembly station 60 where the coated liner backers 45 and 55 as further described below are secured to the corrugated medium 37 to form a composite sheet protein box carton blank.

(15) As noted above, two liner sheets 41 and 51 of roll stock Kraft paper are removed from the respective rolls 40 and 50 and the respective liner sheets 41 and 51 are transported by rollers (not shown) through separate hydrogenated triglyceride, baths 42 and 52 and their associated rollers which applies the hydrogenated triglyceride, namely, beef tallow to the wire side of liner backer sheets 41 and 51 at 2.5 lbs/MSF impregnating the same. It is believed that the absorbent nature of the wire side of the liner board allows more fibers per pound of impregnation to be treated to the liner board. The now impregnated liner backer sheets 43 and 53 are then transported by rollers and coated on the felt side at coating stations 44 and 54 on a single sheet surface side with a styrene acrylic co-polymer coating 18 heated to about 170° F. The coating can be placed on the felt side backing surface by rollers, doctor blades or spraying as is well known in the art. The coating 18 is water based. The coated liner sheets 45 and 55 are then combined at gluing station 60 using a wet strength glue to the corrugated medium 37 with the starch adhesive having a higher solids content than that presently used in the art with the addition of 16 ounces of penetrate added to each glue volume to form a coated corrugated composite board. The coated and impregnated corrugated composite board 61 is then passed over a heat curing bed 70 to cure and set the adhesive or glue. There were no problems with the glue bond and the bond became stronger over time and the overall box appearance become brighter which was significantly better than prior foodstuff boxes. The heat curing bed 70 is a series of hot plates and pressure rollers which applies light pressure and heat to cure the adhesive and the glue cures very rapidly. The composite corrugated board sheet 61 is then cut into individual blank sections in a cutting and stacking station 80 with known means stacking the individual flat sheets of composite corrugated board. If desired, air impact dryers 90 can be used to dry the flat sheets. The blanks are later placed in a standard box cutting station which cuts and scores the composite poultry box 10.

(16) Another embodiment of the protein box 12 uses hydrogenated triglyceride for impregnation and runs through the same process steps as noted above. The hydrogenated triglyceride is heated to a temperature from about 170° F. to about 200° F.

(17) The coating 18 when styrene acrylic co-polymer is used is a water based high solid fluid solution % by weight of the styrene acrylic co-polymer ranging from about 50% to about 55% most preferably about 52% and has a pH ranging from about 8-9 with fully cured Tg of +7. The coating has a specific gravity of ranging from about 1.04 to about 1.6 and viscosity (cps) of about 400, a vapor density the same as water with 30 minute Cobb values of 30 or better. The coating is fast drying, recyclable, repulpable and is printable and glueable.

(18) The wire side impregnation and felt side coated protein box allows a brighter pre-print and the finished protein box has a greater brightness. The printing has an improved sharpness with wire side impregnation. The process also provides the box with higher slide angle results thus eliminating the need for application of anti-skid products. Not only was an improved slide angle obtained using the inventive process but the typical diminishing of the slide angle over time which occurs in the field was lessened by over 50%. Box compression was 18% greater than that of previous boxes which were not impregnated on the wire side and coated on the felt side with the box also having a high slide angle.

(19) 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: