Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/10—Packing paper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B50/00—Making rigid or semi-rigid containers, e.g. boxes or cartons
  • B31B50/74—Auxiliary operations
  • B31B50/81—Forming or attaching accessories, e.g. opening devices, closures or tear strings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F1/00—Mechanical deformation without removing material, e.g. in combination with laminating
  • B31F1/0003—Shaping by bending, folding, twisting, straightening, flattening or rim-rolling; Shaping by bending, folding or rim-rolling combined with joining; Apparatus therefor
  • B31F1/0038—Rim-rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F1/00—Mechanical deformation without removing material, e.g. in combination with laminating
  • B31F1/008—Shaping of tube ends, e.g. flanging, belling, closing, rim-rolling or corrugating; Fixing elements to tube ends
  • B31F1/0087—Rim-rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D3/00—Rigid or semi-rigid containers having bodies or peripheral walls of curved or partially-curved cross-section made by winding or bending paper without folding along defined lines
  • B65D3/28—Other details of walls
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B2105/00—Rigid or semi-rigid containers made by assembling separate sheets, blanks or webs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B2105/00—Rigid or semi-rigid containers made by assembling separate sheets, blanks or webs
  • B31B2105/002—Making boxes characterised by the shape of the blanks from which they are formed
  • B31B2105/0022—Making boxes from tubular webs or blanks, e.g. with separate bottoms, including tube or bottom forming operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B2120/00—Construction of rigid or semi-rigid containers
  • B31B2120/002—Construction of rigid or semi-rigid containers having contracted or rolled necks, having shoulders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B50/00—Making rigid or semi-rigid containers, e.g. boxes or cartons
  • B31B50/25—Surface scoring
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31B50/00—Making rigid or semi-rigid containers, e.g. boxes or cartons
  • B31B50/26—Folding sheets, blanks or webs
  • B31B50/28—Folding sheets, blanks or webs around mandrels, e.g. for forming bottoms
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/22—Polyalkenes, e.g. polystyrene
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/58—Polymers or oligomers of diolefins, aromatic vinyl monomers or unsaturated acids or derivatives thereof
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed
  • D21H19/826—Paper comprising more than one coating superposed two superposed coatings, the first applied being pigmented and the second applied being non-pigmented
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/30—Pretreatment of the paper

Definitions

• the present invention relates to a canister type carton having a curled brim region. More particularly, the present invention relates to a canister type carton having a buckle-controlled brim curl, a method of forming such buckle-controlled brim curl as well as a paperboard blank used to form such a carton.
• the rigidity of a particular container is effected by the tensile and bending stiffness in both the vertical and circumferential directions of the container.
• one expedient for increasing the rigidity of a paper container is to form a brim about the top of the container.
• conventional brim curling mechanisms utilize complimentary curved dies in which the lower die is first moved upwardly around the upper end ofthe cup to the top edge of the cup where it firmly holds the cup top.
• the upper die is then moved downwardly to engage the uppermost edge ofthe cup between the dies with both of the dies then moving downwardly together to curl the upper edge of the container thereby forming a brim.
• This brim adds significantly to the rigidity of the overall cup structure.
• U.S. Patent No. 3,065,677 issued to Loeser discloses a similar brim curling mechanism for containers.
• a lower die having a curve forming upper surface is maintained stationary while an upper die having a curve forming lower surface descends downwardly toward the stationary lower die, deflecting the upper edge portion of the container secured by the lower die and again forming a brim about the upper periphery of the container.
• This brim adds significantly to the overall rigidity of the container.
• Containers of the above-mentioned type can be readily manufactured at relatively high speeds using conventional brim curl forming equipment by forcing an unfinished annular edge into a die which curls the brim outwardly forming a roughly elliptical toroidal rim.
• the orientation of the blank used in forming such containers may also aid in the manufacture of containers having brim curls formed thereon by reducing defects found in the brim curls.
• cracks often appear in the outer surface of the toroidal brim.
• such cracks degrade the appearance of the rolled brim and can often degrade the functionality of the rolled brim particularly when the brim is to seaiingly receive a lid thereon.
• containers of the type discussed above often include outer polymer coatings, such as polyethylene, applied to the paperboard material.
• outer polymer coatings such as polyethylene
• Such polymer coatings may be extruded onto the surface of the paperboard. It is imperative that the polymer coating bond to the paperboard material.
• one of three methods are generally used, namely, corona treatment, flame treatment, or polyethylene imine treatment. These treatments are not always sufficient, however, if the polymer coating or the paperboard is treated with additional coating materials. In these cases, peeling of the polymer coating from the paperboard material can occur which is highly undesirable. Such peeling is particular a problem for brim curled containers in view ofthe stress imposed to the upper portion of the container during formation of the brim curl.
• the primary object of the present invention is to overcome the aforementioned shortcomings associated with the prior art containers.
• Another object of the present invention is to provide a container having a brim curl formed about a portion ofthe container having a relatively small radius without the formation of cracks in an outer surface of the brim curl.
• Yet another object of the present invention is to provide a container formed from a blank having a relatively high thickness when compared to similar prior art paperboard containers.
• a still further object of the present invention is to provide a canister type container wherein defects formed in the brim curl of the container are minimized.
• Yet another object of the present invention is to form a canister type carton from paperboard material impregnated with sizing adhesive in an amount equivalent to from about at least 8 to about 20 lbs/3000 ft 2 ream of paperboard material, and preferably in an amount equivalent to approximately 13 lbs. of sizing adhesive per 3,000 ft 2 ream of paperboard material.
• a further object of the present invention is to provide a method of forming a paperboard container wherein an initial buckling point of the paperboard shell being subjected to a brim curl process is controlled so as to produce a substantially defect free brim curl.
• a still further object of the present invention is to provide a paperboard shell for forming a container having paperboard characteristics which aid the paperboard shell in its travel into a forming die such that the initial buckling point ofthe paperboard shell occurs a substantial distance into the annular edge so as to form substantially defect free brim curls on containers having relatively small radius of curvature at the brim curl.
• Yet another object of the present invention is to provide enhanced bonding of a polymer coating to coated paperboard used to form a paperboard container.
• a paperboard container having a rolled brim with the container being formed of a paperboard material, a rolled brim arc length of less than about 0.25 inches, an outer radius of curvature cut through the plane normal to the axis of the rolled brim arc length of the container adjacent the rolled brim being less than approximately 1.5 inches with the paperboard material forming the container having at least approximately 8 lbs/3,000 ft 2 ream of size press adhesive included therein and preferably approximately 13 lbs/3,000 ft 2 ream of paperboard material.
• One such container includes particular dimensions wherein the outer radius of curvature cut through the plane normal to the axis of the rolled brim arc length of the container adjacent the rolled brim is approximately 1.25 inches while an inner radius of curvature cut through the plane normal to the axis of the rolled brim arc length ofthe container adjacent the rolled brim is at least 1.09 inches.
• the side wall of the container is substantially vertical and a major diameter ofthe rolled brim is approximately 0.14 inches while a minor diameter of the rolled brim is approximately 0.125 inches.
• the aforementioned container is formed by providing a paperboard shell having an unfinished annular exposed edge; directing the unfinished annular edge into a forming surface of a forming die; urging the unfinished annular edge into the forming die and controlling an initial buckling point of the unfinished annular edge of the paperboard shell such that a substantially defect free prolate rolled toroidal brim is formed.
• the buckling point of the unfinished annular edge of the paperboard shell initiates a distance from about 4 to about 8 times the caliper of the paperboard shell from the unfinished annular edge.
• the distance may be defined as from about 25% to about 50% of the arc length of the rolled brim to be formed from the unfinished annular edge.
• a lubricant is provided on one of either the paperboard shell or forming surface of the forming die which allows the unfinished annular edge of the paperboard shell to travel further along the forming surface before the buckling of the unfinished annular edge is initiated. This may be achieved by applying a lubricating agent to the paperboard blank prior to forming the paperboard shell, applying the lubricating agent to the paperboard shell, or applying the lubricating agent to the forming surface of the forming die.
• the lubricating agent is added to a polyethylene coating which is applied to the paperboard material.
• the paperboard blank may further include a styrene-acrylic coating applied prior to the formation of the polyethylene coating.
• the styrene-acrylic coating provides smoothness to the surface of the paperboard while enhancing, rather than diminishing, the resulting bond between the paperboard and the polyethylene coating.
• Figure IA is a perspective view of one type of container which benefits from being formed in accordance with the present invention.
• Figure IB is a perspective view of another type of container which benefits from being formed in accordance with the present invention.
• Figure 2A is a side elevational view of the container illustrated in Figure IA.
• Figure 2B is a side elevational view of the container illustrated in Figure IB.
• Figure 3 A is a top view of the container illustrated in Figure IA.
• Figure 3B is a top view of the container illustrated in Figure IB.
• Figure 4 is a cross-sectional view of an upper tool die for forming a brim curl on the container illustrated in Figure 1.
• Figure 5 is a cross-sectional view of a lower tool die for forming the brim curl on the container illustrated in Figure 1.
• Figure 6A is a schematic representation of a brim curl formed in accordance with the present invention which would be substantially defect free.
• Figure 6B is a schematic representation of a brim curl not formed in accordance with the present invention which would exhibit defects in the exterior surface thereof.
• Figure 7 is a schematic representation of a brim curl being formed illustrating the unfinished annular edge ofthe container entering the brim curl forming die at the point of engagement with the concave upper-toroidal surface of the die.
• Figure 8 is a schematic representation of the brim curl being formed illustrating initial buckling of the unfinished edge as it is urged into engagement with the concave upper surface of the die.
• Figure 9 is a schematic representation of the brim curl being formed illustrating initial curling of the rolled brim as it is further urged into engagement with the concave upper surface of the die.
• Figure 10 is a schematic representation of the brim curl formed illustrating the completion ofthe rolled brim as it completes engagement with the concave upper-toroidal surface of the die.
• Figure 11 is a composite photomicrograph of a section of a prolate rolled brim of a container formed in accordance with the present invention.
• Figure 12 is a composite photomicrograph of a section of an oblate rolled brim of a container not in accordance with the present invention which when examined exhibits cracking on the exterior peripheral surface thereof.
• Figure 13 is a partially cut-away, side elevational view of a second embodiment of the container illustrated in Figure IA.
• Figure 14 is a cross-sectional representation of a brim curl of the second embodiment of the present invention. Detailed Description of the Invention
• FIG. IA wherein a container 10 of the canister type having a substantially vertical side wall 12 is illustrated.
• This container being one type of container which benefits from being formed in accordance with the present invention.
• the container 10 includes rounded corners 14, the particular dimensions of which will be described in greater detail hereinbelow.
• About an upper periphery thereof is a rolled brim or brim curl 16.
• the brim curl is provided in order to add stability to the container as well as allow the container to readily receive and form sealing engagement with a cooperating lid 18.
• the lid includes similar rounded corners and a substantially vertical side wall 20 which frictionally engages the brim curl 16 of the container 10.
• the container 10 is of the canister type and readily receives flowable products such as ice cream, frozen yogurt, sugar, flour, or similar type granular products.
• flowable products such as ice cream, frozen yogurt, sugar, flour, or similar type granular products.
• FIG. 2A the brim curl 16 formed about an upper periphery of the container 10 is readily illustrated. Further, the substantially vertical side walls 12 which extend upwardly from a substantially planar bottom 22 of the container 10 is readily illustrated. It should be noted that while the present invention is described with reference to the particular container 10 illustrated in Figures IA, 2 A and 3 A, the underlying concepts set forth hereinbelow may be readily applied to any paperboard containers having a circular, elliptical, or other curvilinear type opening wherein it is desired to for substantially defect free brim curls about an upper periphery of the container.
• the corners 14 have an inner radius R, cut through the plane normal to the axis of the rolled brim arc length of approximately 1.094 inches where the brim curl begins and an outer radius at the outer periphery of the brim curl R 2 cut through the plane normal to the axis of the rolled brim arc length of approximately 1.250 inches.
• the diameter of the brim curl D, at the curved corners 14 is approximately 0.125 inches while the diameter of the brim curl D 2 along a length of the container is approximately 0.156 inches. It is the diameter of the brim curl along the curvilinear regions 14 which is critical and the essence of the present invention.
• the bottom 22 of the container is of a smaller dimension than the top and includes a radius region R 3 cut through the plane normal to the axis of the rolled brim arc length equal to approximately 1.034 inches. While the side walls 12 of the container are substantially vertical, it is necessary that such walls taper inwardly slightly thereby providing a bottom wall 22 having a smaller dimension than the top ofthe container such that the containers when stacked one upon the other will telescope into one another thereby reducing the overall height of the stack for storage and transportation purposes. Again, forming the brim curl along the elongated regions ofthe container occur substantially without fault. However, as can be appreciated by those skilled in the art, it is at the corners in the curved regions 14 where the paperboard material forming the brim curl is stressed which can often result in the cracking of the outer parameter of the brim curl.
• Cups of this type have a paperboard shell thickness of approximately .007 inches and when formed include a brim curl 17 and slightly angled side walls 23 as illustrated in Figures IB, 2B and 3B.
• a paperboard shell thickness of approximately .007 inches and when formed include a brim curl 17 and slightly angled side walls 23 as illustrated in Figures IB, 2B and 3B.
• the resultant stress on the paperboard shell is great, resulting in cracks and other noticeable defects in the outer surface of the brim curl. Accordingly, by forming such brim curls in accordance with the present invention reduces and substantially eliminates such defects.
• the brim curls formed in either of the containers illustrated in Figures 1-3 are formed by a die arrangement which is heretofore described in detail in U.S. Patent No. 5,029,749 issued to Aloisi et al. and discussed hereinabove and will only be described briefly in connection with the subject invention.
• the particular die arrangement for forming the brim curl 16 or 17 about an upper periphery of the container illustrated in Figures 1-3 includes an upper or male die 110 which may be manipulated by conventional brim forming devices such as those illustrated in U.S. Patent Nos. 2,473,836 and 3,065,677 discussed hereinabove.
• the upper die 110 includes a lower surface having a flange 112 extending axially therefrom thereby providing a slanted outer surface 114 and an undercut 1 16, the significance of which will be described in greater detail hereinbelow.
• the lower or female die 118 illustrated in Figure 5 includes an axial bore 120 which receives a container shell formed from paperboard material.
• the bore 120 being of the same configuration as that of the container itself with an unfinished annular edge of the container extending from the die 118.
• Also formed in the die 118 is a channel 122 which receives the paperboard material during a formation of the brim curl 16 or 17.
• FIG. 7-10 a schematic illustration of the brim curl being formed in accordance with the present invention will be described in greater detail.
• the upper die 110 which includes the elongated surface 114 as well as the concaved forming surface 116. It has been determined in accordance with the present invention that it is desirable that the unfinished annular edge 126 of the paperboard shell 128 which is to form the container as illustrated in Figure 1-3 extend into the forming region 130 of the die 110 as far as practical before initial buckling ofthe paperboard material takes place.
• the elliptical toroidal surface being the surface formed by revolving an ellipse around a line spaced therefrom, this being the brim curl itself.
• the elliptical toroid or brim curl can be classified into classes, an oblate toroidal surface or a prolate toroidal surface.
• an oblate toroidal surface is defined as the surface resulting when the flattened exterior portion of the ellipse 50 is closer to perpendicular to the line about which the elliptical toroidal surface is revolved.
• a prolate toroidal surface is formed when the flattened exterior portion 50 of the ellipse is closer to parallel to the line about which the elliptical toroidal surface is revolved.
• the two classes are divided by a line at about 45° with respect to the line about which the elliptical toroidal surface, that is a surface where the flattened exterior surface 50 extends at an angle less than 45° with respect to the center line, is revolved.
• brim curls closely approximating a prolate toroidal surface that is a surface where the flattened exterior surface 50 extends at an angle less than 45° with respect to the center line exhibit little, if any, failures while those brim curls more closely exhibiting an oblate elliptical toroidal surface or a surface extending at an angle greater than 45° with respect to the center line, generally include numerous failures.
• the leading edge 126 of the paperboard carton shell contacts the concave forming surface of the die 1 10 the paperboard shell is urged into the die as far as possible before an initial buckling at 138 occurs in the paperboard material as illustrated in Figure 8.
• the initial buckling position of the unfinished annular edge of the paperboard shell for the container illustrated in Figure 1 A be a distance of from about 4 to about 8 times the caliper ofthe paperboard shell from the unfinished edge.
• the initial buckling position ofthe unfinished annular edge ofthe paperboard shell should initiate a distance from about 25% to about 50% of an arc length of the rolled brim to be formed from the unfinished annular edge.
• the arc length of the brim curl formed in accordance with the present invention is approximately 0.25 inches.
• the initial buckling position be from 0.0625 inches to 0.125 inches from the unfinished annular edge or with a paperboard shell having a caliper of 0.0235 inches
• the optimum initial buckling position would be 0.094 to 0.188 inches.
• these values are set forth by way of example and the particular initial buckling position of the unfinished annular edge of the paperboard shell would be dependent upon the desired brim curl to be formed as well as the caliper of the paperboard material being used.
• the paperboard stock material which is used in forming the container illustrated in Figures 1-3 is preferably impregnated with sizing adhesives in an amount equivalent to from about at least 8 to about 20 lbs/3,000 ft 2 ream of paperboard material and preferably in the amount equivalent to approximately 13 lbs of sizing adhesive per 3,000 ft 2 ream of paperboard material.
• the sizing adhesives suitable for use in the present invention include those materials commonly applied to paperboard which serve to stiffen the board.
• Typical sizing adhesives include polyvinyl alcohol, carboxymethyl cellulose, naturally occurring gums, sodium silicate, polyvinyl acetate, styrene butadiene, starches and the like as well as various combinations of these materials. For economical reasons, starches are the preferred sizing adhesive for use in connection with the present invention.
• the paperboard material may be impregnated with pigments in the from of clay and the like.
• the amount of pigmentation material not exceed more than 50% of the total sizing adhesive being applied to the paperboard material.
• the main factors affecting the buckling resistance of the container which can be readily controlled during the manufacture of the paperboard material are the Z direction tensile strength of the paperboard material, the amount of wood pulp fiber and its character within the board, the caliper ofthe paperboard material, the moisture content ofthe paperboard material, the amount of sizing adhesive applied to the paperboard material as well as the addition of a lubricant to the paperboard material.
• increasing the Z direction tensile strength of the paperboard material increases the buckling resistance of the paperboard material.
• the productivity of the board machine forming the paperboard material is significantly reduced. Therefore, as is best illustrated in the following Table, a compromise between the increase in size press weight and increase in Z direction tensile strength results in little or no failures in the brim curls while allowing for high productivity.
• the first sample being that having a size press coat weight of approximately 9 lbs/3,000 ft 2 ream and a Z direction tensile strength of approximately 40 lbs per square inch.
• a significant number of failures were evidenced, however, with the use of steam, these failures are reduced significantly.
• the use of steam adds to the production costs of manufacturing such containers.
• the Z direction tensile strength of the paperboard material is increased significantly as exhibited in grade C. the failures are significantly reduced, however, again, as mentioned hereinabove. large increases in Z direction tensile strength result in a decrease in the productivity of the board machine forming the paperboard material.
• FIGs 11 and 12 photomicrographs of two brim curls formed utilizing conventional forming dies are illustrated wherein the caliper of the paperboard material used in each of the samples is identical.
• the paperboard material included approximately 13 lbs/3,000 ft 2 ream of sizing adhesive wherein it can be noted that the initial buckling point of the paperboard material is on the order of 4 to 8 times that of the caliper of the material for containers such as that illustrated in Figure IA or 25% to 50% of the arc length of the elliptical toroidal surface being formed.
• the brim curl formed on the sample illustrated in Figure 12 includes an initial buckling point which is less than 25% ofthe arc length ofthe elliptical toroidal surface and less than 4 times that of the caliper of the paperboard material.
• the sizing adhesive added to the sample set forth in Figure 11 is significantly greater than that of the sample set forth in Figure 12.
• the unfinished annular edge of the paperboard shell of the sample set forth in Figure 11 passes further into the concave forming surface before buckling thus resulting in a substantially defect free brim curl.
• the unfinished annular edge of the paperboard shell of the example set forth in Figure 12 did not pass fully into the concave region of the forming die and thus buckled at a point less than an optimum distance into the paperboard material and consequently results in a brim curl exhibiting cracks and other failures in its outer surface.
• the paperboard material is coated with a useful coating polymer prior to formation of the paperboard shells used in forming the containers in accordance with the present invention.
• Polymers suitable for this purpose are polymers comprising carbon and hydrogen moieties or carbon, hydrogen and oxygen moieties having a melting point below 270 °C and having a glass transition temperature (T g ) in the range of -150° to +120°C.
• the preferred polymer is a low density polyethylene for containers similar to that illustrated in Figure IA and a high density polyethylene for cups such as that illustrated in Figure IB.
• an additional means in aiding in the passing of the paperboard material into the forming die is the addition of a lubricant to the polyethylene coating which is applied to the paperboard material.
• the lubricant added to the polyethylene was glycerol monostearate, however, any known lubricant may be used to accomplish the same goals. By adding such lubricant, the leading edge ofthe paperboard material will not be prematurely caught in the forming die and thus permitted to pass completely into the forming die before the initial buckling takes place. It should also be noted that a lubricant may also be applied to the forming die itself.
• the lubricant contaimng polyethylene coating to adhere to the paperboard material resulting in a paperboard shell which passes further into the forming die when urged thus aiding in the control ofthe initial buckling point during formation ofthe brim curl in accordance with the present invention.
• the use ofthe lubricant reduces the coefficient of friction of the surface of the paperboard material as well as reduces any static charge build up during handling of the paperboard material.
• the paperboard material may also include a coating to impart smoothness to the paperboard. This is particular desirable for the outer wall of the resulting container to provide an aesthetically pleasing appearance and to enhance the ability to provide printing thereon.
• Ethylene vinyl acetate latex has been used as a coating to impart smoothness to paperboard. Such coatings, however, have been found to diminish the bond between the paperboard and a polymer coating layer. Specifically, peeling ofthe polymer coating layer from the coated paperboard can occur. It has also been found that the presence of the hereinabove noted lubricant further reduces the bonding strength between the polymer coating layer and a coated paperboard material.
• a primer layer including a styrene-acrylic derivative latex on the surface of the paperboard material prior to extrusion of the polymer coating layer to the paperboard material provides very desirable results.
• styrene- acrylic derivatives in the coating layer include, but are not limited to n-butyl- acrylate acrylonitrile, n-amyl-acrylate acrylonitrile, n-propyl-acrylate-acrylonitrile and n-ethyl-acrylate-acrylonitrile.
• Aliphatic acrylate styrene co-polymers are preferred and include, but not limited to, n-butyl-acrylate acrylonitrile-styrene, n-amyl-acrylate acrylonitrile-styrene, n-propyl-acrylate-acrylonitrile-styrene and n-ethyl-acrylate-acrylonitrile styrene.
• Mean adhesion between the coated paperboard and the polymer coating of 170 and greater can be achieved using such a primer latex coating layer for the paperboard.
• Figure 13 is a partially cut ⁇ away side view ofthe container of Figure 2 A illustrating paperboard material 26 and an extruded polymer coating layer 28.
• polymer coating layer 28 is preferably polyethylene.
• Figure 13 also includes primer layer 30 which, in accordance with the present invention, is preferably a styrene-acrylic latex layer.
• Primer layer 30 provides the desired smoothness to the surface of the paperboard, while also significantly increasing the bonding strength of polymer coating layer 28 to paperboard material 26. Such increased bonding strength is provided for both lubricated and non-lubricated polymer coatings.
• Primer layer 30 of the present invention is extremely advantageous for a brim curled container in view of the extreme stress exerted on the top portion of the container during formation. Without sufficient bonding between the polymer coating layer and the paperboard, the stresses created during formation of the brim can cause peeling and separation of the coating from the paperboard.
• Figure 14 provides an expanded cross-section of the brim shown in Figure 6 A illustrating paperboard material 26, polymer coating layer 28 and primer layer 30.
• the styrene-acrylic latex of primer layer 30 preferably includes n-butyl-acrylate-acrylonitrile-styrene co-polymer.
• the primer layer may also include one or more of an inorganic pigment, such as clay/carbonate, a thickener/water retention agent, a dispersant, a biocide, a defoamer and a dye.
• an inorganic pigment such as clay/carbonate, a thickener/water retention agent, a dispersant, a biocide, a defoamer and a dye.
• the composition of primer layer 30 includes approximately 20 parts of an acrylonitrile-styrene co-polymer, such as BASF Acronal S 504, and 100 parts inorganic pigment (clay/carbonate).
• Other styrene- acrylic polymers useful in the present invention include BASF's Acronal S 888
• the ethylene vinyl acetate primer included 20 parts ethylene vinyl acetate, and the styrene-acrylic latex primer included 20 parts n-butyl-acrylate-acrylonitrile- styrene co-polymer. These primer layers were each applied to a paperboard material and a polymer layer was extruded on the primer layer. In one case, the polymer did not include a lubricant and PEl was not performed and in the second case, the polymer included lubricant and PEl was performed.
• the mean polyethylene (PE) adhesion for coated paperboard material having in this example a gloss finish, more than doubled for the styrene-acrylic coating compared to the ethylene vinyl acetate coating.
• Test 1 was an uncoated paperboard material with no smoothness coating. Uncoated board is often used on the interior of paperboard containers and also generally includes a matt finish polyethylene coating thereon.
• Tests 2-9 were coated paperboard material including an ethylene vinyl acetate primer layer. Specifically, Tests 2 and 3 did not include a lubricant. Further, Test 2 did not include PEl treatment, while Test 3 did. Tests 4 and 5 included a lubricant and, like Tests 2 and 3, Test 4 did not include PEl treatment and Test 5 did. As can be seen, the presence of a lubricant significantly reduced the mean PE adhesion between the paperboard and the polymer coating layer. Although PEl treatment increased adhesion, the mean PE adhesion was still below 120.
• Tests 6-9 included different levels of lubricant and PEl treatments with an ethylene vinyl acetate primer layer. The mean PE adhesion was still below
• Tests 6, 8 and 9 were below 100.
• Tests 10-13 utilized the styrene-acrylic primer layer of the present invention.
• the mean PE adhesion was significantly improved using the styrene-acrylic primer layer to greater than 173, even when the polyethylene polymer coating included a lubricant. Consequently, it is readily apparent that significant improvements in bonding between extruded polyethylene and the paperboard coated with a smoothness coating can be achieved using a styrene-acrylic latex coating of the present invention.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Containers Having Bodies Formed In One Piece (AREA)

Applications Claiming Priority (5)

Publications (2)

Family

ID=27056199

Family Applications (1)

Country Status (3)

Families Citing this family (1)

Citations (4)

Family Cites Families (10)

• 1996
  • 1996-07-26 EP EP96927249A patent/EP0853585A4/de not_active Withdrawn
  • 1996-07-26 WO PCT/US1996/012188 patent/WO1997005024A1/en not_active Ceased
  • 1996-07-26 CA CA002227372A patent/CA2227372A1/en not_active Abandoned

Patent Citations (4)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events