Patent Application
20080271866
The invention relates to the papermaking art and, in particular, to the manufacture of paper or paperboard substrates, paper-containing articles such as multilayered paper or paperboard or corrugated-based packaging, having a functional layer, as well as methods of making and using the same.
Paper substrates containing functional layers are highly desired by several niche markets. Each functional layer may be specifically tailored to each market demand and specifications depending on the packaging requirement for consumer goods. These packaging requirements are specifically determined by the risks associated with packaging and shipping such goods around the country and around the world. However, such demands from such markets may require functionalities to be programmed within the functional layer of paper substrate that, when the paper substrate is incorporated into a package, the functionality itself prohibit and/or make it costly and/or less efficient to manufacture and/or convert the substrate so as to be incorporated into a paper-based package. Accordingly, there is an unmet need for all markets to be able to program tailored functionality into a coating layer of a paper substrate (e.g. based upon the nature of the consumer goods to be packaged and/or shipped) so that, when the paper substrate is incorporated into a such packages, there is little or no loss of manufacturing/conversion efficiency and thus little or no increase in overhead costs for production of such packages.
The inventors have surprisingly found a paper substrate containing a functional layer that, when incorporated into a package for shipping, is capable of minimizing the costly impact of that functionality on the downstream manufacturing/converting requirements by increasing manufacturing/converting efficiency that otherwise would render the use of such functionality cost prohibitive.
The paper substrate contains a web of cellulose fibers. The source of the fibers may be from any fibrous plant. In certain embodiments, at least a portion of the pulp fibers may be provided from non-woody herbaceous plants including, but not limited to, kenaf, hemp, jute, flax, sisal, or abaca although legal restrictions and other considerations may make the utilization of hemp and other fiber sources impractical or impossible. The paper substrate of the present invention may contain recycled fibers and/or virgin fibers. Recycled fibers differ from virgin fibers in that the fibers may have gone through the drying process at least once, preferably several times.
The paper substrate of the present invention may contain from 1 to 99 wt %, preferably from 5 to 95 wt %, most preferably from 60 to 80 wt % of cellulose fibers based upon the total weight of the substrate, including 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 99 wt %, and including any and all ranges and subranges therein.
Preferably, the sources of the cellulose fibers are from softwood and/or hardwood. The paper substrate of the present invention may contain from 1 to 100 wt %, preferably from 5 to 95 wt %, cellulose fibers originating from softwood species based upon the total amount of cellulose fibers in the paper substrate. This range includes 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 wt %, including any and all ranges and subranges therein, based upon the total amount of cellulose fibers in the paper substrate.
The paper substrate may alternatively or overlappingly contain from 0.01 to 100 wt % fibers from softwood species, preferably from 0.1 to 95 wt %, most preferably from 1 to 90 wt % based upon the total weight of the paper substrate. The paper substrate contains not more than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 wt % fibers from softwood species based upon the total weight of the paper substrate, including any and all ranges and subranges therein.
The paper substrate of the present invention may contain from 1 to 100 wt %, preferably from 5 to 95 wt %, cellulose fibers originating from hardwood species based upon the total amount of cellulose fibers in the paper substrate. This range includes 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 wt %, including any and all ranges and subranges therein, based upon the total amount of cellulose fibers in the paper substrate.
The paper substrate may alternatively or overlappingly contain from 0.01 to 100 wt % fibers from hardwood species, preferably from 5 to 95 wt %, cellulose fibers originating from hardwood species based upon the total amount of cellulose fibers in the paper substrate. The paper substrate contains not more than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99 and 100 wt % fibers from hardwood species based upon the total weight of the paper substrate, including any and all ranges and subranges therein.
When the paper substrate contains both hardwood and softwood fibers, it is preferable that the hardwood/softwood ratio be from 0.001 to 1000. This range may include 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000 including any and all ranges and subranges therein and well as any ranges and subranges therein the inverse of such ratios.
Further, the softwood and/or hardwood fibers contained by the paper substrate of the present invention may be modified by physical and/or chemical means. Examples of physical means include, but is not limited to, electromagnetic and mechanical means. Means for electrical modification include, but are not limited to, means involving contacting the fibers with an electromagnetic energy source such as light and/or electrical current. Means for mechanical modification include, but are not limited to, means involving contacting an inanimate object with the fibers. Examples of such inanimate objects include those with sharp and/or dull edges. Such means also involve, for example, cutting, kneading, pounding, impaling, etc means.
Examples of chemical means include, but is not limited to, conventional chemical fiber modification means including crosslinking and precipitation of complexes thereon. Examples of such modification of fibers may be, but is not limited to, those found in the following U.S. Pat. Nos. 6,592,717, 6,592,712, 6,582,557, 6,579,415, 6,579,414, 6,506,282, 6,471,824, 6,361,651, 6,146,494, H1,704, 5,731,080, 5,698,688, 5,698,074, 5,667,637, 5,662,773, 5,531,728, 5,443,899, 5,360,420, 5,266,250, 5,209,953, 5,160,789, 5,049,235, 4,986,882, 4,496,427, 4,431,481, 4,174,417, 4,166,894, 4,075,136, and 4,022,965, which are hereby incorporated, in their entirety, herein by reference.
Sources of “Fines” may be found in SaveAll fibers, recirculated streams, reject streams, waste fiber streams. The amount of “fines” present in the paper substrate can be modified by tailoring the rate at which such streams are added to the paper making process.
The paper substrate preferably contains a combination of hardwood fibers, softwood fibers and “fines” fibers. “Fines” fibers are, as discussed above, recirculated and are typically not more that 100 μm in length on average, preferably not more than 90 μm, more preferably not more than 80 μm in length, and most preferably not more than 75 μm in length. The length of the fines are preferably not more than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 μm in length, including any and all ranges and subranges therein.
The paper substrate contains from 0.01 to 100 wt % fines, preferably from 0.01 to 50 wt %, most preferably from 0.01 to 15 wt % based upon the total weight of the substrate. The paper substrate contains not more than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 wt % fines based upon the total weight of the paper, including any and all ranges and subranges therein.
The paper substrate may alternatively or overlappingly contain from 0.01 to 100 wt % fines, preferably from 0.01 to 50 wt %, most preferably from 0.01 to 15 wt % based upon the total weight of the fibers contained by the paper substrate. The paper substrate contains not more than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 wt % fines based upon the total weight of the fibers contained by the paper substrate, including any and all ranges and subranges therein.
The paper substrate may also contain a functional layer.
The functional layer may contain additives that permit the layer to be a holdout layer. Examples of a holdout layer may be those that holdout or reduce the penetration of grease, water, water vapor, salt air, carbon dioxide, sulfur dioxide, hydrogen sulfide, or other solids/gases/liquids which pose a threat to surfaces of, for example, metallic objects, consumables such as fruits and vegetables, as well as other consumer/manufacturing goods. Examples of paper substrates containing holdout layers include United States Published Patent Applications 20020182381; 20040221976 and U.S. provisional applications having U.S. Ser. Nos. 60/698,274 filed Jul. 11, 2005 and 60/731,897, filed on Oct. 31, 2005, which are hereby incorporated, in their entirety, herein by reference. The functional layer may contain the additives mentioned in these applications so as to impart such functionality in the layer, the substrate, and resulting package made therefrom.
The functional layer may also contain releasable additives. An example of a releasable additive may be vapor corrosion inhibitors. Examples of such inhibitors may be found in U.S. Pat. Nos. 6,833,334; 6,617,415; 6,555,600; 6,444,595; 6,420,470; 6,331,044; 6,292,996; 6,156,929; 6,132,827; 6,054,512; 6,028,160; 5,937,618; 5,896,241; 5,889,639; 5,773,105; 5,736,231; 5,715,945; 5,712,008; 5,705,566; 5,486,308; 5,391,322; 5,324,448; 5,139,700; 5,209,869; 5,344,589; 4,313,836; 4,312,768; 4,151,099; 4,101,328; 6,429,240; 6,273,993; 6,255,375; and 4,685,563 and in U.S. application having US Ser. No. 60/731,897, filed on Oct. 31, 2005, which are all hereby incorporated, in their entirety, herein by reference.
The functional layer may also contain an antifouling agent and/or antimicrobial agent and may serve to be antifouling and/or antimicrobial. Alternatively, it may serve to release such antifouling and/or antimicrobial agents into the local environment. Examples of such antimicrobial agents are those found in United States Published Patent Applications 20020182381; 20040221976, and U.S. applications having U.S. Ser. Nos. 60/585,757; 11/175,899; and 11/175,700, which are hereby incorporated, in their entirety, herein by reference.
In one specific embodiment, the paper substrate of the present invention may contain a functional layer containing a film-forming compound. Although the film-forming compound may be any film-forming compound, examples of preferred film-forming compounds may be those that have Tg, glass transition temperatures, of not greater than 350° C. The Tg may be any Tg, but preferably not greater than 350, 340, 330, 325, 320, 310, 300, 290, 280, 275, 270, 260, 250, 225, 200, 175, 150, 125, and 100, including any and all ranges and subranges therein. An example of such a film forming compound is a styrene acrylate-containing compound such as Dow latex 229804 and/or starch such as Ethylex 2035 Starch. The film forming compound may be present in the functional layer from 0 to 100%, preferably from 50 to 150 ppm, based on the total weight of the functional layer, including 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, and 95 wt % based on the total weight of the functional layer, including any and all ranges and subranges therein. In ppm, the film forming compound may be present in the functional layer at any amount, preferably 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, and 150 ppm based on the total weight of the functional layer, including any and all ranges and subranges therein.
The functional layer may be present at any weight. The functional layer may be present at a weight that ranges from 1 to 25 gsm, preferably from 2 to 20 gsm, more preferably from 3 to 18 gsm (grams per square meter), and most preferably from 5 to 15 gsm. This includes, but is not limited to, embodiments where the functional layer is added to the fibers at the size press and/or coater. The amount of functional layer include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, and 25 gsm, including any and all ranges and subranges therein.
Further, the functional layer may contain any crosslinker. A preferable crosslinker is one such as Cartabond TSI. Still further, the functional layer may contain a pigment which can act as an anti-blocking agent. Any clay or anti-blocking agent is acceptable. A preferable pigment is a clay. A preferable clay is one such as NuClay. Still further, the functional layer may contain a defoamer. The crosslinker may be present from 0.1 to 10 ppm based on the total weight of the functional layer, preferably 0.1, 0.2, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3, 4, 5, 6, 7, 8, 9, and 10 ppm based on the total weight of the functional layer, including any and all ranges and subranges therein. The pigment may be present from 50 to 150 ppm based on the total weight of the functional layer, preferably 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, and 150 ppm based on the total weight of the functional layer, including any and all ranges and subranges therein. The defoamer may be present from 50 to 150 ppm, preferably 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, and 150 ppm based on the total weight of the functional layer, including any and all ranges and subranges therein.
The functional layer, when contacted with the fibers of the paper substrate, may have any pH, preferably from 4 to 8, including 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 and 8, including any and all ranges and subranges therein. The functional layer, when contacted with the fibers, may have any % solids, preferably a % solids of from 1 to 65, more preferably from 10 to 60% solids, including 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60% solids, including any and all ranges and subranges therein. The functional layer, when contacted with the fibers, may have a Brookfield Viscosity@ 100 rpm of ≦1000 cps, preferably ≦300 cps, most preferably from 50 to 200 cps, including 50, 55, 60, 65, 70, 75, 80, 90, 100, 11, 120, 130, 140, 150, 160, 170, 180, 190, and 200 cps, including any and all ranges and subranges therein.
The density, basis weight and caliper of the web of this invention may vary widely and conventional basis weights, densities and calipers may be employed depending on the paper-based product formed from the web. Paper or paperboard of invention preferably have a final caliper, after calendering of the paper, and any nipping or pressing such as may be associated with subsequent coating of from about 1 mils to about 35 mils, although the caliper can be outside of this range if desired. More preferably the caliper is from about 4 mils to about 20 mils, and most preferably from about 7 mils to about 17 mils. The caliper of the paper substrate with or without any functional layer may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 20, 22, 25, 27, 30, 32, and 35, including any and all ranges and subranges therein.
Paper substrates of the invention preferably exhibit basis weights of from about 10 lb/3000 ft2 to about 500 lb/3000 ft2, although web basis weight can be outside of this range if desired. More preferably the basis weight is from about 30 lb/3000 ft2 to about 200 lb/3000 ft2, and most preferably from about 35 lb/3000 ft2 to about 150 lb/3000 ft2. The basis weight may be 10, 12, 15, 17, 20, 22, 25, 30, 32, 35, 37, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 500 lb/3000 ft2, including any and all ranges and subranges therein.
The final density of the papers may be calculated by any of the above-mentioned basis weights divided by any of the above-mentioned calipers, including any and all ranges and subranges therein. Preferably, the final density of the papers, that is, the basis weight divided by the caliper, is preferably from about 6 lb/3000 ft2/mil to about 14 lb/3000 ft2/mil although web densities can be outside of this range if desired. More preferably the web density is from about 7 lb/3000 ft2/mil to about 13 lb/3000 ft2/mil and most preferably from about 9 lb/3000 ft2/mil to about 12 lb/3000 ft2/mil.
The substrate of the present invention preferably has a Cobb Value as determined by the Cobb Sizing Test, according to ASTM D-3285 (TAPPI T-441), of less than 50 g/m2, preferably less than 35 g/m2, more preferably less than 30 g/m2, most preferably less than 25 g/m2. The Cobb Value may be 50, 45, 40, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 g/m2, or less, including any and all ranges and subranges therein.
Textbooks such as those described in the “Handbook for pulp and paper technologists” by G. A. Smook (1992), Angus Wilde Publications, which is hereby incorporated, in its entirety, by reference. Further, G. A. Smook referenced above and references cited therein provide lists of conventional additives that may be contained in the paper substrate, and therefore, the paper articles of the present invention. Such additives may be incorporated into the paper, and therefore, the paper packaging (and packaging materials) of the present invention in any conventional paper making process according to G. A. Smook referenced above and references cited therein.
The paper substrate of the present invention may also include optional substances including retention aids, sizing agents, binders, fillers, thickeners, and preservatives. Examples of fillers include, but are not limited to; clay, calcium carbonate, calcium sulfate hemihydrate, and calcium sulfate dehydrate. Examples of binders include, but are not limited to, polyvinyl alcohol, polyamide-epichlorohydrin, polychloride emulsion, modified starch such as hydroxyethyl starch, starch, polyacrylamide, modified polyacrylamide, polyol, polyol carbonyl adduct, ethanedial/polyol condensate, polyamide, epichlorohydrin, glyoxal, glyoxal urea, ethanedial, aliphatic polyisocyanate, isocyanate, 1,6 hexamethylene diisocyanate, diisocyanate, polyisocyanate, polyester, polyester resin, polyacrylate, polyacrylate resin, acrylate, carboxymethyl cellulose, urea, sodium nitrate, and methacrylate. Other optional substances include, but are not limited to silicas such as colloids and/or sols. Examples of silicas include, but are not limited to, sodium silicate and/or borosilicates. Another example of optional substances is solvents including but not limited to water.
Further, the starch may be of any type, including but not limited to oxidized, ethylated, cationic and pearl, and is preferably used in aqueous solution. Illustrative of useful starches for the practice of this preferred embodiment of the invention are naturally occurring carbohydrates synthesized in corn, tapioca, potato and other plants by polymerization of dextrose units. All such starches and modified forms thereof such as starch acetates, starch esters, starch ethers, starch phosphates, starch xanthates, anionic starches, cationic starches and the like which can be derived by reacting the starch with a suitable chemical or enzymatic reagent can be used in the practice of this invention.
Useful starches may be prepared by known techniques or obtained from commercial sources. Suitable starches include, but are not limited to, PG-280 from Penford Products, SLS-280 from St. Lawrence Starch, the cationic starch CatoSize 270 from National Starch and the hydroxypropyl No. 02382 from Poly Sciences, Inc.
Starches for use in the practice of this invention may be modified starches. Still further, are those starches that are cationic modified or non-ionic starches such as CatoSize 270 and KoFilm 280 (all from National Starch) and/or chemically modified starches such as PG-280 ethylated starches and AP Pearl starches. Starches for use in the practice of this invention may be cationic starches and chemically modified starches.
The contacting of the functional layer with the cellulose fibers may occur anytime in the papermaking process including, but not limited to the wet end, thick stock, thin stock, head box, size press and coater, with the preferred addition point being at the size press and/or coater. Further addition points include machine chest, stuff box, and suction of the fan pump. As discussed above and in
The paper substrate may be made by contacting further optional substances with the cellulose fibers as well. The contacting may occur anytime in the papermaking process including, but not limited to the thick stock, thin stock, head box, size press, water box, and coater. Further addition points include machine chest, stuff box, and suction of the fan pump. The cellulose fibers, functional layer, and/or optional/additional components may be contacted serially, consecutively, and/or simultaneously in any combination with each other. The cellulose fibers and functional layer may be pre-mixed in any combination before addition to or during the paper-making process.
The paper substrate may be pressed in a press section containing one or more nips. However, any pressing means commonly known in the art of papermaking may be utilized. The nips may be, but is not limited to, single felted, double felted, roll, and extended nip in the presses. However, any nip commonly known in the art of papermaking may be utilized.
The paper substrate may be dried in a drying section. Any drying means commonly known in the art of papermaking may be utilized. The drying section may include and contain a drying can, cylinder drying, Condebelt drying, IR, or other drying means and mechanisms known in the art. The paper substrate may be dried so as to contain any selected amount of water. Preferably, the substrate is dried to contain less than or equal to 10% water.
The paper substrate may be passed through a size press, where any sizing means commonly known in the art of papermaking is acceptable. The size press, for example, may be a puddle mode size press (e.g. inclined, vertical, horizontal) or metered size press (e.g. blade metered, rod metered). At the size press, sizing agents such as binders may be contacted with the substrate. Optionally these same sizing agents may be added at the wet end of the papermaking process as needed. After sizing, the paper substrate may or may not be dried again according to the above-mentioned exemplified means and other commonly known drying means in the art of papermaking. The paper substrate may be dried so as to contain any selected amount of water. Preferably, the substrate is dried to contain less than or equal to 10% water.
In addition to the starch and/or polyvinyl alcohol being added at the size press/coater section(s), small amounts of other additives may be present as well in the size composition. These include, without limitation, dispersants, fluorescent dyes, surfactants, deforming agents, preservatives, pigments, binders, pH control agents, coating releasing agents, optical brighteners, defoamers, bulking agents such as expandable microspheres and the like. Such additives may include any and all of the above-mentioned optional substances, or combinations thereof.
The paper substrate may be calendered by any commonly known calendaring means in the art of papermaking. More specifically, one could utilize, for example, wet stack calendering, dry stack calendering, steel nip calendaring, hot soft calendaring or extended nip calendering, etc.
The paper substrate may contain multiple layers of cellulose fibers webs. Preferably, the substrate contains at least three layers of cellulose fiber webs having six major surfaces or four layers of cellulose fiber webs having eight major surfaces. Any of these surfaces may be corrugated, laminated, glued, or adhered to each other in any conventional manner so as to form a multilayered substrate. Preferably, a multilayered paper substrate may be a corrugated paper substrate. In one embodiment of the invention, a corrugated paper substrate may be made from the paper substrate of the present invention and further converted/folded/die cut into for example a package and/or shipping material that is, single layered and/or multilayered paper or paperboard material. The package and/or shipping material preferably comprises at least three paper substrates, each having a web of cellulose fibers and at least one of which further containing the functional layer therein and/or thereon.
These above-mentioned methods of making the paper substrate of the present invention may be added to any conventional papermaking processes, as well as converting processes, including corrugating, abrading, sanding, slitting, scoring, perforating, sparking, calendaring, sheet finishing, converting, coating, laminating, printing, etc. Preferred conventional processes include those tailored to produce paper substrates capable to be utilized as coated and/or uncoated paper products, board, and/or substrates. Textbooks such as those described in the “Handbook for pulp and paper technologists” by G. A. Smook (1992), Angus Wilde Publications, which is hereby incorporated, in its entirety, by reference.
Within the above-mentioned conventional papermaking processes, as well as converting processes, multilayered paper-based structures (e.g. such as those mentioned above) are formed and/or folded into shapes useful for packaging and/or shipping. During this time, means for connecting such layers together are required. Such means may be gluing, laminating, adhering and/of folding such layers together and require, in part, an adhesive.
Accordingly, the paper substrate and articles made therefrom preferably contain an adhesive layer.
The adhesive layer preferably contains at least one adhesive that is suitable for adhering two layers of cellulose fiber web together. Any conventional adhesive is suitable. Examples of suitable adhesives include those known as hot melt adhesives and/or cold-set adhesives. Examples of the adhesive are those containing a polyamide, polyamide containing polymer, polyamide containing copolymer, polyethylene, polyethylene-containing polymer, polyethylene-containing copolymer, ethylene vinyl acetate, ethylene vinyl acetate-containing polymer, ethylene vinyl acetate copolymer, vinyl, polyvinyl, vinyl containing polymer, vinyl containing copolymer, poly, alpha olefin, olefin, polyolefin, olefin containing polymer, and olefin containing copolymer. Commercial hot melt adhesives include those from National Starch, Hercules, Henkel, Reynolds, Arizona Chemical Company, and HB Fuller. Specific examples are Henkel 80-8795; Chief 235 HP; National Starch 34-246A; Chief 235 Plus; HB Fuller HL9254; Henkel TB9-15-5; National Starch 34-6601; National Starch 34-379A; Forbo/Swifts; Pacific; H. B. Fuller G3556; and Henkel 51-1057-FD. The adhesives may be used together and/or alone.
In one preferred embodiment, when a single adhesive is used, it is preferably that it be a hot-melt adhesive. In another preferred embodiment, when more than one adhesive is used, it is preferably that at least one hot-melt adhesive and at least one cold-set adhesive be utilized. The adhesives may be contained in a single layer or multiple layers and may follow the example of the substrate discussed above in relation to
When two layers of cellulose fiber web are incorporated into the above-mentioned substrate of the present invention, a portion of the functional layer may intervene between the two webs at some time, which may cause a reduction in the adhesive properties of the adhesive layers thereon to adhere the webs together. Therefore, the efficiency of such converting processes may be compromised by the functionality in the functional layer present on/in the paper substrate at the time of the above-mentioned conventional converting steps. In such cases, it may be preferable to expose at least a portion of at least one layer of cellulose fiber web to the adhesive layer before and/or during and/or after adhesive layer application. Alternatively and/or in addition to such exposure, it may desirable to increase the surface area of contact between the adhesive layer and the functional layer. Preferably, both the increase in surface area and the exposure methodologies in combination is an embodiment of the present invention. Such portions of the paper substrate may be referred to as “treated” portions.
Means for exposing at least a portion of at least one layer of cellulose fiber web to the adhesive layer or means for increasing the surface area of contact between the adhesive layer and the functional layer may include any means for compromising at least a portion of the functional layer. Such means may include, for examples, means for penetrating, abrading, skiving, boring, breaking, busting, cracking, diffusing, drilling, eating through, encroaching, entering, goring, impaling, infiltrating, inserting, piercing, knifing, perforating, permeating, pervade, pop in, pricking, puncturing, reaming, spearing, stabbing, wearing, chafing, eroding, grating, rubbing, scraping, scratching, scuffing, denting, fragmenting, nicking, notching, paring, scratching, shaving, slicing, and splintering. Any conventional above-mentioned means commonly known to the skilled artisan, especially papermaking, is suitable, including a combination thereof. These means may be added to any conventional papermaking process and/or converting process, and/or those papermaking and/or converting processes mentioned herein, especially those processes that lead to the production of paper-based packaging systems.
An example of a converted blank for a package that contains at least one substrate of the present invention is shown as
In some instances, it is not desirable to perform any of the above mentioned means for treating the substrate, yet the presence of the functional layer could greatly reduce ability of substrates to adhere to one another. In such cases, not any conventional adhesive may be used in the adhesive layer. Preferably, the adhesive should provide an open time of from 0.5 to 5.0, more preferably 1.5 to 3.5 seconds, most preferably 1.9 to 2.5 seconds. In addition and/or in alternative, the adhesive should provide a dwell time for compression of 0.25 to 1.5 second, preferably 0.5 to 1.25 seconds, more preferably from 0.65 to 0.85 seconds. In addition and/or in alternative, the adhesive must satisfy the below mentioned initial fiber tear test (Hot melt Bonding Test attached below) which is the use of a Rock-Term hot melt simulator (see Examples) using settings of, 300 to 450 deg F., preferably from 350 to 380 deg F., the above-mentioned open time (preferably ˜2.5 sec open time), with the above-mentioned dwell time (preferably ˜0.75 sec dwell time), and with tearing force applied immediately after dwell time to simulate springback forces during conversion of packages made from the substrate of the present invention.
The Hot Melt Bonding Test provides a value of simulating the hog melt gluing process in the lab so as determine the effects of major variables such as substrate, adhesive, temperature, open and dwell times, and adhesive amount upon gluing. In the present application, this test was performed in the lab when two strips of paper are cut CD (cross direction) long: 2.5″×8″ and 1″×8″ specimens respectively. The adhesive is applied at the temperatures ranging from 350 to 400 degree F. to the uncoated side of the 2.5″×8″ specimen with a 1.5 second of open time. The coated side of the second 1″×8″ is compressed onto this for 1.0 seconds of compression time. The samples are glued, cooled, and torn along the length of the glue bead at TAPPI Standard Conditions (73 degree F., 50% Relative Humidity).
If the initial fiber tear test mentioned above, a fiber tear test resulting in:
a. 50-75% initial fiber tear to have a working solution would preferably require a cold-set adhesive (below this level one may not even achieve adequate bonding to hold flaps)
b. 75-100% initial fiber tear to have a working solution that may or may not require a cold-set adhesive (see item #4). A cold set adhesive may be optional if this is the initial fiber tear results. However, then a test four 4 hours of curing to the substrate is begun (Four hour cured fiber tear test relates to use of Rock-Term hot melt simulator using settings of, 300 to 450 deg F., preferably from 350 to 380 deg F., the above-mentioned open time (preferably 2.5 sec open time), with the above-mentioned dwell time (preferably 0.75 sec dwell time), with samples stored at TAPPI standard conditions (73 F, 50% RH) under no applied load, and then torn after four hours of curing). If, after the 4 hour test, there remains a 75-100% initial fiber tear, then sufficient bonding occurs with the first adhesive, preferably a hot-melt adhesive, alone and the cold-set adhesive is optional. If, however, <75% fiber tear occurs after the 4 four hour test mentioned above, then a cold set adhesive assist would be desirable in addition to the first adhesive, preferably a hot-melt adhesive.
The present invention is explained in more detail with the aid of the following embodiment example which is not intended to limit the scope of the present invention in any manner.
Packagings for fruits and vegetables have had problems with their inability to protect their handlers and the produce contained therein from deadly predators. Accordingly, it has been desirable to treat the packages so that the environment, in which they lie, while in transit to the consumer, in part results in their exposure to sulfur dioxide.
Sulfur dioxide is known to kill predators of produce and pests of humans. One such pest is the black widow spider. It is necessary to keep black widow spiders away or dead when in contact with the produce package and environment. Therefore, it is desirable to have a packaging material for the product that does not absorb, adsorb, and/or chemically react with the sulfur dioxide in the shipping environment. Such interactions will inevitably reduce the amount of active sulfur dioxide within the environment; thereby reducing the efficacy of the killing/controlling pests sensitive to sulfur dioxide such as black widow spiders.
Until now, the only effective packaging material to ship such produce effectively and resist the sulfur from absorbing, adsorbing, and/or chemically reacting with such material is Styrofoam. However, Styrofoam is not environmentally friendly. Therefore, the market still demands an environment-friendly packaging material that is capable of shipping produce at low cost and not absorb, adsorb, and/or chemically react with the sulfur dioxide in the shipping environment to the point that the active sulfur dioxide is reduced so that it is ineffective in keeping pests away and/or killing them.
As one specific non-limiting embodiment of the present invention, the inventors have surprisingly found a cellulose-based packaging material that is capable of shipping produce at low cost and not absorb, adsorb, and/or chemically react with the sulfur dioxide in the shipping environment to the point that the active sulfur dioxide is reduced so that it is ineffective in keeping pests away and/or killing them. This one non-limiting embodiment of the present invention is a paper substrate containing a functional layer that specifically increases the hold-out capacity of the substrate to sulfur dioxide. Measurement of hold-out capacity is discussed below. Preferably, the hold-out capacity is increased at least 1%, more preferably more than 5%, most preferably more than 20% as compared to substrates that do not contain this non-limiting embodiment of the functional layer. Further, the inventors have surprisingly found solutions to minimize the effect of a functional layer (e.g. sulfur dioxide holdout layer in this example) of a paper substrate on the manufacturing/converting costs/problems, while maintaining functional and structural performance of a package that incorporates the substrate therein.
The sulfur dioxide testing setup is described on the next pages, including initial attempts to physically (such as taping edges of substrates) and chemically (changing the amounts and types of chemistries contained by the functional layer of the substrates tested.
The above mentioned timepoint measurements are in ppm of sulfur dioxide. Therefore, the higher the number, the more sulfur dioxide measured in the atmosphere, and the more effective the functional layer-containing substrate is to sulfur dioxide holdout.
In this specific embodiment, it is preferably to have a functional layer that had sulfur dioxide holdout of any kind at 5 and/or 15 minutes respectively, preferably from 5 to 100% holdout based upon the total amount of sulfur dioxide initially present in the atmosphere, more preferably from 10 to 100% holdout based upon the total amount of sulfur dioxide initially present in the atmosphere, most preferably from 50 to 100% holdout based upon the total amount of sulfur dioxide initially present in the atmosphere. The amount of holdout may be greater than 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 99% holdout based upon the total amount of sulfur dioxide initially present in the atmosphere, including any ranges and subranges therein.
The results in tables 1, 2, 3 were tested under different conditions.
A saturation point of SO2 in the board was determined by purging the boards and then waiting 15 minutes to test SO2 levels. Initially six (10″×12″) boards were used with one minute purges but it was taking too long to reach a saturation level (5 ppm increase per purge), so we cut the sample to one 6″×10″ board in the chamber with 2 minute purges.
Saturation point of a 6″×10″ piece of cardboard. Usually purges were done immediately after the previous SO2 measurement: those that were not are indicated.
Screen Pigments with Improved Glueability
Effect of pH on SO2 Barrier
Boards with the Pigment:Dow Formulations
Apply Dow latex based and starch coatings onto liner and medium which will be used to make corrugated boxes with improved SO2/moisture barrier performance for grape packaging applications.
Coat weight:
The same as the proposed Box Construction Plan in Example 2, except a 74 lb paper substrate was put in to replace the 69 lb substrate. Condition 3 mentioned below was then converted to a package and/or box so as to be Box #3. Therefore, unless specifically mentioned otherwise below, the DuraCool box or International Paper box # 3 corresponds to a box that was made from Condition #3 mentioned below.
The above-mentioned box blanks were successfully converted to trays at the using Boix MP-S equipment using several hot melt adhesives with a cold glue assist. There were three major gluing scenarios, all of which produced well-bonded DEFOR Black Widow grape trays:
The initial hot melt adhesives recommended by Henkel, Chief Adhesives and National Starch did not set quick enough through the Boix MP-S equipment to hold the flaps of the tray together and/or had poor bonding and fiber tear. The adhesives trialed in the first trial are listed below.
The major issue which the first trial uncovered were the following:
To better simulate the Boix equipment, the hot melt gluing test using the RockTenn simulator was modified so that a springback force was applied manually following the compression cycle (SEE THE ATTACHED FORHTE ROCK-TENN LAB TESTER INFORMATION AND METHODOLOGY). The most recent latex coated liner was used as the substrate with an open time of 3 seconds and compression time of 0.75 seconds in the following tests
The goal of the cold set glue tests was to determine the degree of fiber tear achieved with the latex coated liner and the time to achieve complete fiber tear. The resin (polyvinyl acetate formulation) adhesive was applied with a 0.015-inch Bird bar to the felt side of the latex coated liner and a second specimen of the treated liner was placed felt side down onto the first strip and compressed at 0.3 psi for the duration of the test. The time was varied in intervals from 5 to 28 minutes and the degree of fiber tear was noted for each test. The table below shows the minimum time at which 100% fiber tear was noted for each adhesive:
With untreated linerboard, the time to develop 100% fiber tear is in the range of 10 to 30 seconds. Therefore, the latex coating significantly retards the rate of absorption of the water-based adhesives, but still achieves complete fiber tear.
Based upon the above, the cold-set glue adhesive is recommended at this time when used along with the hot melt glue even on the boxes to provide their high temperature resistance. As the grapes boxes are stored and packaged in temperatures sometimes exceeding 110 degree F., hot melt glue alone would soften leading to pop-opens unless there was cold-set glue to provide a strong bond that can resist temperature extremes.
Although the comparison of times to achieve complete fiber tear is useful to understand the dynamics of absorption, the recommendation must also consider the ability of each of the cold-set adhesives to create a thick enough film to bridge the gap between the two surfaces of the coated linerboard in the glue flap region. As it turns out, the product with the slowest absorption rate creates the thickest film which persists long enough to effectively bond the two surfaces of the board.
The goal of the second converting trial was to evaluate the various hot melt adhesives and to produce enough trays for the long term storage
There were two board conditions that were trialed (condition numbers relate to prior coating and corrugating trials):
Condition 3 represents the minimum coating cost scenario in which the single-face (74 ag) and the doubleback (62 ag) liner were coated on their outer surfaces (non-flute contacting side) and the dual arch medium (26c/26c) was uncoated.
Condition 5 was a condition that was designed to be easier to glue on the Boix equipment as it had the latex on the medium and only the doubleback (62 ag) sides. The plan was to convert Condition 3 using the newer hot melt adhesives and to convert Condition 5 using the standard Henkel adhesive for comparison. As it turned out, even the Condition 5 trays had one glue flap that contained a latex coating on the DB liner side, so that it also required a higher performance hot melt. The standard hot melt adhesive does not bond to the latex coated portion of the glue flap, therefore this is not a viable low cost commercial solution.
The hot melt adhesive trials on the Boix MP-S equipment are listed below. It is important to note that the tray flaps held together through the Boix equipment even at the highest operating speed (24 boxes per minute (bpm).
Stacks of trays 25 high with an additional 40 lbs. of weight at the top of the stack of each of the nine conditions were placed outside the plant in direct sunlight to determine whether any of the flaps would open. Conditions #3A, B and C were outside for approximately 3.5 hours; Conditions #3D, E and F were outside for approximately 3 hours; Conditions #3G, H and I were outside for approximately 1.5 hours in direct sunlight and approximately 90 F ambient temperature. Each stack was then placed inside the plant at the conclusion of the day and was examined the next morning (September 7). All stacks of trays maintained their structural integrity on this overnight stacking test, with the exception of 2 boxes out of 25 that had one flap popping open made with the Chief 235 Plus hot melt and with no cold-set adhesive.
Also, boxes of each condition number were torn open and the subjective force to open the flaps was noted. There were three key results:
A condition in which the outer surfaces of the glue flaps of the blanks were roughened or perforated to determine whether the standard hot melt adhesive used on uncoated boxes (Henkel 80-7883) could successfully bond a latex coated box (Condition 3). Using a knife, the glue flaps of several trays were perforated to simulate a skiving operation that may also be used on folding cartons as a cold glue assist methodology. These samples were produced and demonstrated that good fiber tear could be produced even using a less aggressive hot melt adhesive.
Sulfur dioxide fumigation is used by the California table grape industry for control of insects and decay in packed table grapes. The treatment for decay control is designed to achieve a minimum dose of 100 CT (concentration in ppm×time in hours), achieved by either a 30-minute treatment or a total utilization treatment. The treatment for black widow spider control is a 30-minute fumigation with 6% CO2 and 1% SO2. While there is no official requirement for monitoring CTs during the black widow spider treatment, laboratory studies suggest that a CT of approximately 3,000 to 3,300 ppm·hrs is required for high spider mortality.
The type of packaging materials used can influence the concentrations of sulfur dioxide in the fumigation room during treatment due to the potential for packaging materials to absorb sulfur dioxide. Cardboard packaging material generally has a high rate of sulfur dioxide absorbance. In fact, the cardboard box is no longer approved for use in the black widow spider protocol for this reason.
Initial tests included two experimental boxes, #1 and #3. For each test, two boxes of the same type were packed with 18 pounds of cold table grapes, held at 20 degree C. overnight to equilibrate to that temperature, and fumigated the following day. The two boxes (25.4 liters, 0.90 ft3 each) were loaded into a sealed 165 liter chamber and the final load volume was 30.8%. The boxes were fumigated with 1% sulfur dioxide (1,900 ml 100% SO2 injected) for 30 minutes at 20 degree C. The sulfur dioxide levels in the chamber were monitored at the start and every 5 minutes thereafter using a rapid gas analyzer. A 10 ml sample was drawn through a rubber septum mounted on the fumigation chamber with a syringe and injected into the analyzer. The sulfur dioxide concentrations over time (CT) were calculated for each test. The results from these tests indicated that the Styrofoam boxes had the highest CT, followed by condition #3, then condition #1 and finally the regular cardboard box.
In these initial tests, grapes had been placed in the boxes immediately upon removal from the cold room and allowed to warm in the box. This likely resulted in condensation within the bags which may have reduced the final CT values for all the tests. However, it was clear that box #3 had the best performance of the cardboard boxes and therefore subsequent tests focused on box #3. It should be reiterated that box #3 was constructed and converted from liner and medium condition #3 of Table 11 and described in more detail at page 50 above. We wondered if the amount of time the grapes were in the box after harvest would influence moisture absorbance by the box and subsequent absorbance of sulfur dioxide. In this next test, we fully warmed and dried the grapes before placing them into the cardboard boxes. The grapes were held in different sets of boxes for 2, 4, 8 and 12 hours prior to 1% sulfur dioxide fumigation as described above. There were two separate boxes for each time point.
The boxes absorbed additional weight over time, but more of the weight gain occurred in the first few hours and slowed thereafter. There was not much effect on sulfur dioxide absorbance of storing the grapes up to 8 hours in the box, but perhaps a slight decrease in CT at 12 hours. The results indicate that the final CT using box type #3 and a load factor near 30.8% would be close to 3,000 CTs and should provide for high black widow spider mortality.
The final test involved storing a regular untreated cardboard grape box and experimental box #3 with grapes at 0 degree C. for two weeks prior to sulfur dioxide fumigation at 0 C. The boxes were weighed before and after cold storage to determine the amount of moisture gain during this time. Following storage, two boxes of each type were fumigated with 1% sulfur dioxide as described above and the CT values determined.
There was a clear difference between the CT values for the two types of boxes fumigated following two weeks of cold storage, with a four-fold higher CT value with the Experimental Box #3. The regular cardboard box absorbed more water than experimental box #3. However, the weight gain was also substantial for the experimental box, but this did not seem to greatly affect the CT value achieved during sulfur dioxide fumigation. The pattern of decline in sulfur dioxide concentration between the two box types during fumigation after cold storage is shown below.
This graph represents the percent of sulfur dioxide in the fumigation chamber during a 30-minute fumigation with 1% sulfur dioxide. In each fumigation, two boxes of the same type, untreated cardboard boxes or experimental boxes #3 were placed in the cold room for two weeks with grapes prior to loading into the fumigation chamber at a load factor of 30.8%. The final CTs are given in Table 18 above.
Our results demonstrate that the experimental boxes absorbed less sulfur dioxide during a simulated black widow spider fumigation protocol than the standard cardboard grape box. The best performance was for box #3 which achieved an 80% higher CT value than the standard cardboard box under the test conditions employed. The CTs following fumigation in box #3 were approximately 3,000. Accordingly, the present invention relates to a paper substrate that is capable of making a box that has a CT of more than 2000, preferably more than 2500, more preferably more than 3000. These substrate is capable of being incorporated into a box that has a CT of at least 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, and 4000, including any and all ranges and subranges therein. Previous results from laboratory tests suggest these CT would provide for greater than 90% black widow spider mortality. In comparison, the regular cardboard grape box gave a CT of 1,500 which would provide for about 50% black widow spider mortality. Following cold storage for two weeks, both box types weighed more (presumably they absorbed moisture from the air and fruit), but the experimental box showed a smaller increase in weight and achieved a four-fold higher CT than the regular cardboard grape box. The CT achieved with box #3 (2421 ppm hours) should provide for approximately 80% spider mortality while the CT achieved with the regular cardboard box would provide for less than 30% mortality.
The experimental box #3 developed by International Paper has been demonstrated to absorb considerably less sulfur dioxide than the regular cardboard table grape box and is worthy of further consideration as an improved packing material for the table grape industry. The reduction in sulfur dioxide absorbance would likely be beneficial for decay control and black widow spider control.
To find a suitable replacement for Styrofoam boxes used for long term storage of table grapes, several different coated boxes were developed and their performance during the sulfur dioxide fumigation was tested in our laboratory. The box of the present invention containing the substrate of the present invention showed the best performance. The absorption of sulfur dioxide was significantly reduced compared to the uncoated box. Its performance was also superior compared to the competitors' boxes.
The testing was performed in an airtight chamber with air and sulfur dioxide mixture (0.7% by weight). An empty box was placed in a testing chamber and fumigated with the gas mixture until the atmosphere in the chamber was completely exchanged. After the fumigation, the concentration of the SO2 was measured periodically using Drager tubes.
The graph below compares results of the measurements of different boxes. In order to confirm that the chamber was sealed, the empty chamber was fumigated with the gas mixture and the concentration of sulfur dioxide was measured at 15 and 30 minutes. The SO2 concentration remained constant within the experimental error (see the blue line on the graph below).
The rest of the lines on the graph show sorption of sulfur dioxide by different types of boxes. The box with a better performance will have a flatter line, showing smaller change in the sulfur dioxide concentration. The Styrofoam box showed the least sorption of SO2 as expected. The uncoated box caused a dramatic decrease in the sulfur dioxide concentration (orange line on the graph), which dropped more than half after only 5 minutes. The GP box (blue line) performed in a way similar to the uncoated box. The Weyerhaeuser box (green line) showed smaller sorption of sulfur dioxide, and the Maxco box performed better compared to the other two competitors'boxes.
We tested two IP DuraCool boxes (red lines). One of them was printed, the other unprinted. The overlap of the two red lines indicates good reproducibility of the data. The performance of the box according to the present invention made from the substrate of the present invention was superior to all of the tested competitors' boxes and showed significant improvement in performance when compared with the uncoated box.
The inventive boxes were also tested in the laboratory of the Department of Plant Sciences at the University of California Davis. The testing was performed on boxes packed with grapes, using the chamber with load similar to that used by grape growers. The amount of sulfur dioxide introduced into the chamber was equivalent to 1% by weight. These testing conditions simulated closely the grape fumigation process prior to storage. We were not able to test the competitors' boxes the same way due to logistics, however by correlating the inventive box data (i.e. Duracool) obtained in our laboratory with the results from UC Davis, we were able to make predictions of performance of the competitors' boxes under the same conditions. The graph below illustrates the calculated predicted results. The performance of the boxes is expressed in the amount of sulfur dioxide remaining in the chamber during the treatment in units called CT (ppm×hr). The actual tested CT value for the DuraCool box was close to 3000, while the Maxco box (which was the best performing competitors' box) had the predicted CT value of 2570. Based on the results of general testing, a box having a CT of approximately 2700 or higher will provide greater than 90% black widow mortality.
Numerous modifications and variations on the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the accompanying claims, the invention may be practiced otherwise than as specifically described herein.
As used throughout, ranges are used as a short hand for describing each and every value that is within the range, including all subranges therein.
All of the references, as well as their cited references, cited herein are hereby incorporated by reference with respect to relative portions related to the subject matter of the present invention and all of its embodiments
The present invention is related to, and claims the benefit of 119(e) priority to U.S. provisional patent application Ser. No. 60/698,274; entitled “MULTILAYERED PAPER OR PAPERBOARD PRODUCT HAVING IMPROVED SULFUR DIOXIDE HOLDOUT”, which was filed on Jul. 11, 2005, and is hereby incorporated, in its entirety, herein by reference. This application is also related to and claims the benefit of 119(e) priority to U.S. provisional patent application Ser. No. 60/734,021; entitled “A PAPER SUBSTRATE CONTAINING A FUNCTIONAL LAYER AND METHODS OF MAKING AND USING THE SAME”, which was filed on Nov. 4, 2005, and is hereby incorporated, in its entirety, herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60698274 | Jul 2005 | US | |
| 60734021 | Nov 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US06/26716 | Jul 2006 | US |
| Child | 12008009 | US |
