Patent Application
20240401276
Transparent or translucent materials are used in all different types of applications. Transparency, for instance, is a highly desirable quality in packaging materials. For example, although packaging materials are necessary to protect products during shipping and sales, consumers prefer to be able to view the product through the packaging.
In the past, most transparent or translucent materials, including packaging materials, were formed from plastic materials, such as polyester polymers and polyolefin polymers. These plastic materials, however, are derived from non-renewable, fossil resources, including petroleum-based resources. These resources are not sustainable, are not renewable, and produce polymer products that do not readily degrade. Thus, efforts have been made in the past in an attempt to produce transparent or translucent materials from renewable resources, such as cellulose materials.
For example, low opacity or transparent papers have been developed and produced in the past. Transparent paper products, for instance, have been used in the form of tracing paper, clear windows for envelopes, and more recently packaging paper for cereals, pasta, or bakery products. For example, EP 3 483 337 A1 generally relates to translucent or transparent paper suitable for laminate and packaging applications, particularly to a translucent paper having improved transparency by a coating process.
In many instances, in order to produce a transparent or translucent paper, non-renewable resources or components that do not readily biodegrade were combined with the paper. For example, one type of paper produced in the past was manufactured from wood pulp fibers that may have been combined with an enzyme, such as xylanase. These substrates typically had a relatively high basis weight in order to provide sufficient strength or other mechanical properties. In order to reduce the thickness of the cellulose paper, densify the paper, and produce transparent properties, the paper was combined with petroleum-based chemicals or synthesized resins and then fed through a supercalendering process. As used herein, during supercalendering, a paper is first calendered by pressing it between metal cylinders or rollers. Afterwards, the paper is sent through an additional set of calenders to produce an even smoother and glossier paper, referred to as a supercalendered paper. The supercalender includes several cylinders alternating between polished metal and soft resilient surfaces. The supercalender applies pressure, heat, and friction to glaze both surfaces of the paper to make the paper smooth and/or glossy.
Transparent or translucent papers made in the past as described above have various drawbacks and deficiencies. For instance, as stated above, even though the fibers used to produce the paper are obtained from renewable resources and are biodegradable and compostable, the papers are typically combined with petroleum-based chemicals or other synthetic resins that can frustrate the goal of producing bio-sourced materials. In addition, although supercalendering can be very effective at changing the properties of the paper, the process is very energy intensive.
Barrier properties to water, water vapor, and grease are also important for packaging materials. Usually, these properties are only achieved with petroleum-sourced materials.
In view of the above, it would be desirable to provide a low opacity paper that can be substantially bio-sourced and can be biodegradable and compostable and produced without supercalendering and using fewer cellulose fibers. It would be particularly desirable to provide such a low opacity paper having effective barrier properties.
The following presents a simplified summary of the claimed subject matter in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is intended to neither identify key or critical elements of the claimed subject matter nor delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts of the claimed subject matter in a simplified form as a prelude to the more detailed description that is presented later.
Paper materials and products are provided that may function as an alternative to plastic films currently on the market. In particularly, low opacity paper is provided that can be made at relatively low basis weights, without containing a substantial amount of petroleum-based resources. In some embodiments, the low opacity paper is manufactured without having to supercalender the paper, thus reducing the energy requirements needed to make the product. The low opacity paper described herein can also be formulated to be substantially, or completely, biodegradable, and compostable. In addition, the low opacity paper can have an excellent balance of properties including high transparency, low permeability for providing high barrier properties, and good mechanical properties for converting and handling.
In one aspect, a paper product comprises a fibrous web containing cellulose fibers. The cellulose fibers contained in the web can be refined to a relatively high degree as may be measured according to a freeness value. The cellulose fibers contained in the web have a degree of refining of greater than or equal to about 60° SR, such as greater than about or equal to 70° SR. The fibers generally have a freeness value of less than or equal to about 100° SR, such as less than or equal to about 90° SR. The freeness value (° SR) generally measures the rate at which a dilute suspension of refined fibers may be drained. The freeness is measured by the Schopper Riegler Method for drainability. As used herein, freeness can be measured according to NORM EN ISO 5267-1:2000.
In various embodiments, the basis weight of the fibrous web is less than about 30 g/m2, preferably less than about 24 g/m2, more preferably less than or equal to about 22 g/m2 and most preferably less than or equal to about 20 g/m2, and generally greater than or equal to about 10 g/m2. In a preferred embodiment, the basis weight of the fibrous web is in the range of 10 to 24 g/m2 and preferably 10 to 18 g/m2. As used herein, basis weight can be measured according to ISO 536:2012.
The fibrous web defines a first surface and a second surface. As will be readily understood by the skilled person, the first surface and the second surface are the main surfaces of the fibrous web, which may also be referred to as “upper” and lower” surface and are located opposite to each other.
In various embodiments, the paper product comprises a coating on at least one of the first surface and/or the second surface of the fibrous web. The coating comprises a transparency agent. The transparency agent comprises a bio-based wax or oil.
In various embodiments, the paper product has an opacity of less than or equal to about 40% when tested according to ISO 2471:2008. For example, the opacity can be less than or equal to about 30%, such as less than or equal to about 25%, such as less than or equal to about 23%, such as less than or equal to about 20%, such as less than or equal to about 18%.
In various embodiments, the fibrous web of the paper product has a basis weight of from about 12 g/m2 to about 24 g/m2, preferably to about 22 g/m2 and displays an opacity of less than or equal to about 25%, such as less than or equal to about 23%, such as less than or equal to about 20%. In another embodiment, the fibrous web of the paper product has a basis weight of from about 12 g/m2 to about 22 g/m2 and displays an opacity of less than or equal to about 23%, such as less than or equal to about 20%, such as less than about 18%. In yet another embodiment, the fibrous web of the paper product has a basis weight of from about 12 g/m2 to about 20 g/m2 and displays an opacity of less than or equal to about 20%, such as less than or equal to about 19%, such as less than or equal to about 18%.
The transparency agent included in the coating may comprise a plant or animal derived wax or oil. For example, in one aspect, the transparency agent is a plant derived wax or oil. In particular embodiments, the transparency agent can be a coconut-based wax, a palm-based wax, a rice-based wax, and/or a soy-based wax.
In various embodiments, the fibrous web can comprise a wetlaid web. The fibrous web can contain wood pulp fibers alone or in combination with bast fibers. Bast fibers are plant fibers collected from the phloem or bast surrounding the stem of dicotyledonous plants. Bast fibers can for example be obtained from flax, hemp, ramie, stinging nettle, lime trees, linden trees, willow, oak, wisteria and mulberry. From an economical perspective, the bast fibers are preferably obtained from flax, hemp or ramie. The wood pulp fibers, for instance, can be softwood fibers, hardwood fibers, or combinations thereof. The paper product can be produced without containing any paraffins, mineral oils, or hydrocarbon oils. In one aspect, the paper product can be constructed such that the product is free from petroleum-based chemicals, including polymers. For example, the paper product can be free from polyolefin polymers, polyester polymers, and the like. Thus, in one aspect, the paper product can be repulpable and compostable.
The paper product can contain cellulose fibers generally in an amount greater than or equal to about 50% by weight, such as in an amount greater than or equal to about 60% by weight, such as in an amount greater than or equal to about 65% by weight, such as in an amount greater than or equal to about 70% by weight, such as in an amount greater than or equal to about 75% by weight, such as in an amount greater than or equal to about 80% by weight. Cellulose fibers are generally present in the paper product in an amount less than or equal to about 95% by weight, such as in an amount less than or equal to about 90% by weight, such as in an amount less than or equal to about 85% by weight, such as in an amount less than or equal to about 80% by weight.
The transparency agent can be present in the paper product in an amount greater than or equal to about 10% by weight, such as in an amount greater than or equal to about 15% by weight, such as in an amount greater than or equal to about 17% by weight, such as in an amount greater than or equal to about 20% by weight. The transparency agent is present in the paper product generally in an amount less than or equal to about 50% by weight, such as in an amount less than or equal to about 40% by weight, such as in an amount less than or equal to about 30% by weight, such as in an amount less than or equal to about 25% by weight, such as in an amount less than or equal to about 20% by weight. In one embodiment, the transparency agent can be water miscible and applied to the fibrous web as an aqueous composition.
In one particular embodiment, the fibrous web can contain first cellulose fibers blended with second cellulose fibers. The first cellulose fibers can have an average fiber length that is shorter than the average fiber length of the second cellulose products. The first cellulose fibers, for instance, can be contained in the fibrous web in an amount from about 30% to about 70% by weight and the second cellulose fibers can be present in the fibrous web in an amount from about 70% to about 30% by weight based upon the total weight of fibers contained in the web. The first cellulose fibers, for instance, can have an average fiber length of from about 2.5 mm to about 5 mm.
The paper product may have a combination of beneficial properties. For instance, the paper product can be relatively thin having a thickness of less than or equal to about 50 μm, such as less than or equal to about 45 μm, such as less than or equal to about 40 μm, and generally greater than or equal to about 20 μm. Thickness is measured according to EN ISO 534:2011. The basis weight of the fibrous web is less than or equal to about 30 g/m2, preferably less than or equal to about 24 g/m2, more preferably less than or equal to about 22 g/m2 and most preferably less than or equal to about 20 g/m2, and generally greater than or equal to about 10 g/m2. In a preferred embodiment, the basis weight of the fibrous web is in the range of 10 to 24 g/m2 and preferably 10 to 18 g/m2.
In certain embodiments, the fibrous web has a basis weight of less than about 30 g/m2 and a thickness of about 50 μm to about 20 μm. In an exemplary embodiment, the basis weight is about 19 g/m2 and the thickness is about 30 μm to 38 μm. Reducing the thickness of the web for a given basis weight increases the overall transparency of the paper product. For example, the opacity of the paper in these embodiments is less than about 20% or less than or equal to about 18%.
The paper product can also have a Gurley air permeability measured according to ISO 5636-5:2003 of less than or equal to about 45,200 seconds, such as less than or equal to about 20,000 seconds, such as less than or equal to about 10,000 seconds, such as less than or equal to about 1000 seconds, and generally greater than or equal to about 200 seconds. The paper product can also have a water resistance of greater than or equal to about 10 min according to TAPPI T 432 cm-09 (2 μL of water volume is used in test). The paper product can have a water vapor barrier at 23° C. and 50% HR of less than 100 g/m2/day, such as less or equal to than 80 g/m2/day and generally greater than or equal to about 0.1 g/m2/day according to ASTM E96/E96M—15:2014.
In another aspect a packaging paper is provided comprising one of the paper products described above.
In another aspect, a method for producing a low opacity paper product comprises coating a fibrous web with an aqueous composition containing a transparency agent. The transparency agent may comprise a bio-based wax or oil, such as a coconut-based wax, a palm-based wax and/or a soy-based wax.
In various embodiments, the fibrous web is impregnated with the aqueous composition containing the transparency agent using a size press. In other embodiments, however, the transparency agent can be applied to the fibrous web by using an applicator roll, by knife coating, by spraying, or by using any other suitable coating technique.
In another aspect, the fibrous web comprises a wetlaid web. The method of making the product can include generating an aqueous suspension of cellulose fibers; refining the cellulose fibers; depositing the aqueous suspension of fibers onto a porous forming surface to form a fibrous web; and coating the fibrous web with an aqueous composition containing the transparency agent.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive. Additional features will be set forth in part in the description which follows or may be learned by practice of the description.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments, and serve to explain the principles herein.
This description and the accompanying drawings illustrate exemplary embodiments and should not be taken as limiting, with the claims defining the scope of the description, including equivalents. Various mechanical, compositional, structural, and operational changes may be made without departing from the scope of this description and the claims, including equivalents. In some instances, well-known structures and techniques have not been shown or described in detail so as not to obscure the description. Like numbers in two or more FIGURES represent the same or similar elements. Furthermore, elements and their associated aspects that are described in detail with reference to one embodiment may, whenever practical, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment and is not described with reference to a second embodiment, the element may nevertheless be claimed as included in the second embodiment. Moreover, the depictions herein are for illustrative purposes only and do not necessarily reflect the actual shape, size, or dimensions of the system or illustrated components.
It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.
In accordance with one aspect of this description, a low opacity paper is provided herein. As used herein, the term “low opacity” means transparent or translucent. A product is considered to have low opacity when the product displays an opacity of, e.g., less than or equal to about 45% when tested according to ISO 2471:2008. Low opacity characteristics refer to the characteristics which provide a paper product with transparency or translucency, such as the presence of a transparency agent.
In one aspect, the paper can be transparent. Alternatively, the paper can be formulated to be translucent. In certain embodiments, the low opacity paper can be formed exclusively from sustainable resources that meets all of the requirements for entering the paper recycle stream after use. In the past, for instance, transparent papers typically contained components derived from fossil-based resources, such as petroleum-derived products. The low opacity paper described herein can be produced having over 90% bio-based content. In addition, in one aspect, the low opacity paper can be formulated to be paraffin-free. Consequently, the low opacity paper can be constructed in order to meet all of the requirements for food contact and food handling.
Also of advantage is that the low opacity paper described here can be constructed so as to minimize the use of materials while still having sufficient mechanical properties for handling, processing, and end use applications. For instance, the low opacity paper can be constructed at relatively low basis weights.
As used herein, a “coating” on the surface(s) of the fibrous web can be obtained by applying a generally liquid coating agent on the surface(s) of the fibrous web by means of any suitable coating, impregnation or saturation technique, such as for example air knife coating, roll-to-roll coating, blade coating, spray coating, Mayer rod coating, direct gravure printing, offset gravure printing, reverse gravure printing, smooth roll coating, curtain coating, bead coating, slot coating, fill press coating or impregnation via a size press. The coating can be a continuous coating or a discontinuous coating. Accordingly, along the lateral dimension of the fibrous web, the coating can be present in a part of or the complete fibrous web. When applying the coating composition to the fibrous web, it will penetrate into some of the internal spaces and pores between the fibers of the fibrous web resulting in saturation and/or impregnation of the fibrous web with the coating (composition). That is, the coating will permeate into the fibrous web, in particular internal spaces and pores therein, and apart from this it can cover and preferably does cover at least part of the first and/or the second surface of the fibrous web in the form of a surface coating. In other words, a “coating” as understood herein covers the saturation and impregnation of the fibrous web.
As used herein, the term “transparency agent” refers to an agent which decreases the opacity of fibrous web when applied inside or on the fibrous web. Examples include plant or animal derived waxes or oils, such as a coconut-based wax, a palm-based wax, and/or a soy-based wax. Plant or animal derived components as understood herein can be obtained from biomass.
As used herein, the term “biomass” is broadly understood as encompassing all kinds of plant and animal material and material derived from the same. Biomass does not include petroleum or petroleum-derived products. The biomass may comprise macromolecular compounds, examples of which are lignin and polysaccharides, such as starch, cellulose, hemicellulose. As will be appreciated, certain kinds of biomass may include both plant and animal-derived material. As examples, manure (dung), night soil and sewage sludge can be mentioned. While the biomass is preferably plant biomass, i.e. biomass of or derived from plants, certain contents of animal biomass (i.e. biomass of or derived from animals) may be present therein. For instance, the biomass may contain up to 30% of animal biomass. According to a preferred embodiment, the biomass is preferably plant biomass, contains more than 70 wt %, most preferably more than 90 wt %, of polysaccharides and lignines in terms of the solid contents of the biomass. For instance, the plant biomass may be agricultural plant material (e.g. agricultural wastes) or all kinds of wood material. Biomass may be in the form of waxes and oils, including coconut, palm, and soy waxes and oil.
As used herein, a “biodegradable” component is a component that is capable of being decomposed by living organisms, such as bacteria or fungi. A biodegradable component can thus be decomposed by the action of microorganisms such as bacteria or fungi with or without oxygen. In one aspect, a biodegradable component fulfills the requirements of at least one of the international industrial standards ISO 14855:2018, ISO 14853:2017, and ASTM D5338:2015.
As used herein, the term “compostable” refers to components that can disintegrate into non-toxic, natural elements. Compostable components, for instance, can degrade at a rate consistent with similar organic materials. Compostable components degrade when exposed to microorganisms, humidity, and/or heat to yield a finished compost product. Coated papers can be formulated to meet international industrial standards ISO 17088:2021, DIN EN 13432:2007, DIN EN 14995:2007, and/or ASTM 6400:2021 defines the requirements for industrially compostable components.
The term “pulp” as used herein refers to fibers from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, sisal, abaca, and bagasse. Pulp fibers can include hardwood fibers, softwood fibers, and mixtures thereof.
As used herein, the term “fibrous web” refers to a sheet made from the pulp by a wetlaid process without coating.
As used herein, the term “bio-based wax or oil” refers to wax or oil which have a bio-based content more than or equal to 90% by weight. The “bio-based wax or oil” is preferably derived from plant biomass. Examples include coconut-based wax, a palm-based wax and/or a soy-based wax. According to an embodiment, the bio-based wax or oil is obtained by processing plant material.
In one aspect, the low opacity paper described herein is formed from a fibrous web containing cellulose fibers that have been refined to a relatively high degree. The fibrous web is combined with a transparency agent, which can be a bio-based wax or oil. The transparency agent not only increases the barrier characteristics of the paper but also lowers the opacity characteristics of the paper. Ultimately, a paper can be produced that has an opacity of less than or equal to about 40% when tested according to ISO 2471:2008. For instance, the opacity of the paper products can be less than or equal to about 35%, such as less than or equal to about 30%, such as less than or equal to about 25%, such as less than or equal to about 20%, such as less than or equal to about 18%, such as even less than or equal to about 16%. The actual opacity can depend upon various factors and is generally greater or equal to than 1%, such as greater than about 5%.
For instance, the basis weight of the fibrous web used to construct the low opacity paper can influence the opacity. In one aspect, the fibrous web of the paper product has a basis weight of from about 12 g/m2 to about 24 g/m2 and displays an opacity of less than about 25%, such as less than about 23%, such as less than or equal to about 20%. In another aspect, the fibrous web of the paper product has a basis weight of from about 12 g/m2 to about 22 g/m2 and displays an opacity of less than about 23%, such as less than about 20%, such as less than or equal to about 18%. In yet another aspect, the fibrous web of the paper product has a basis weight of from about 12 g/m2 to about 20 g/m2 and displays an opacity of less than about 20%, such as less than or equal to about 19%, such as less than or equal to about 18%.
Referring now to
As shown in
As described above, in one embodiment, the fibrous web 12 can be a wetlaid paper web formed from cellulose fibers. For example, the fibrous web can be formed from an aqueous suspension of fibers. The cellulose fibers contained in the fibrous web can be pulp fibers including wood pulp fibers, plant waste fibers, or other plant fibers. In forming the fibrous web, the aqueous suspension of fibers can be deposited onto a porous forming surface that allows water to drain thereby forming the fibrous web.
In one aspect, the fibrous web is made primarily from plant derived or natural fibers. Natural (plant derived) fibers may be selected from chemical pulp, such as sulphate and sulphite pulp, organosolv pulp, recycled fibers, and/or mechanical pulp, Kraft wood pulp, mdf-fibers, nanocellulose, and modifications and combinations thereof. The pulp may be a bleached or non-bleached pulp. The pulp may originate from hardwood or softwood, including birch, beech, aspen such as European aspen, alder, eucalyptus, maple, acacia, mixed tropical hardwood, pine such as loblolly pine, fir, hemlock, larch, spruce such as Black spruce or Norway spruce, and mixtures thereof.
Non-wood plant fibers can also be used, such as seed hair fibers, leaf fibers, and bast fibers. Plant fibers can be provided from e.g. straws of grain crops, wheat straw, reed canary grass, reeds, flax, hemp, kenaf, jute, ramie, seed, sisal, abaca, coir, bamboo, bagasse, cotton kapok, milkweed, pineapple, cotton, rice, reed, esparto grass, Phalaris arundinacea, or combinations thereof.
The fibrous web can be primarily formed from the cellulose fibers without being combined with other components, such as fillers. For instance, the fibrous web (prior to coating) can comprise cellulose fibers in an amount greater than or equal to about 90% by weight, such as in an amount greater than or equal to about 95% by weight. Particular cellulose fibers well suited to producing the fibrous web include softwood fibers, hardwood fibers, birch fibers, hemp fibers, or mixtures thereof. For example, in one embodiment, the fibrous web can be made exclusively from softwood fibers alone or in combination with hardwood fibers. Alternatively, the fibrous web can be made from a blend of wood pulp fibers, such as softwood fibers, with bast fibers, such as hemp or flax fibers. The cellulose fibers can be selected, for instance, in order to produce a web that can be efficiently drained from aqueous fluids during formation and that can produce a relatively low opacity paper at lower basis weights while still retaining mechanical properties needed for processing and handling.
Once a suitable fiber furnish is selected for producing the fibrous web, in one aspect, the fibers used to form the web after pulping can be fed through a refining process in order to increase the freeness value expressed in the unit of “° SR” as measured by the Schopper Riegler Method for drainability (ISO 5267-1:2000). As used herein, refining the cellulose fibers is different than producing pulp fibers. In pulping, the lignin is removed from the cellulose fibers. During refining, on the other hand, the nap of individual fibrils making up the outer surface or wall of the fiber is raised which is sometimes referred to as defibrillation. Refining is the mechanical and/or chemical action which causes defibrillation.
In one aspect, in preparing the fibers for producing the fibrous web, the fibers can first go through a suitable pretreatment, such as washing, and can also be chopped especially if using bast fibers. In addition, the fibers can be fed through a hammermill or subjected to various different chemical treatments.
The cellulose fibers can be mixed with an aqueous solution or solvent which can occur in a refiner, such as a twin screw machine. If desired, wetting agents, acids, or alkalis can also be added in order to soften the cellulose fibers. In addition, one or more alcohols can also be added to the fibers including methyl alcohol, ethyl alcohol, or mixtures thereof.
The aqueous suspension can be fed to or formed in a refiner and subjected to a mechanical refining action. The consistency of the fibers in the refiner can be from about 1% to about 30% solids content. In the refiner, such as a twin screw refiner, the pulp suspension is subjected to mechanical action that produces the formation of greater fibrils within each fiber.
It should be understood that any suitable refining device may be used in order to increase the freeness value of the fibers and that a twin screw refiner merely represents one instrument, process or technique that may be used.
After exiting one or more refiners, the cellulose fibers have a freeness value of greater than or equal to about 60° SR, such as greater than or equal to about 65° SR, such as greater than or equal to about 67° SR, such as greater than or equal to about 70° SR. In one aspect, the cellulose fibers have been refined to greater than about 72° SR, such as greater than or equal to about 74° SR, such as greater than or equal to about 76° SR, such as greater than or equal to about 78° SR, such as greater than or equal to about 80° SR. The freeness value of the fibers is generally less than or equal to about 95° SR, such as less than or equal to about 90° SR, such as less than or equal to about 88° SR, such as less than or equal to about 85° SR such as less than or equal to about 80° SR. It was discovered that refining the fibers to the extent described above not only can improve drainage of the web during production but can also lower the opacity characteristics of the paper. Refining the cellulose fibers can also allow for a reduction in the thickness of the sheet while still providing good mechanical properties. Reduction in thickness for a given basis weight, for instance, has been found to unexpectedly improve transparency while still maintaining an excellent balance with mechanical properties. Adjusting the level of refining of the cellulose fibers can also allow for adjustments to the barrier properties of the low opacity paper. For instance, refining of the fibers can be used to adjust air permeability and to develop air barrier properties, water barrier properties, oil barrier properties, or the like.
Once the cellulose fibers have been refined, the fibers are formed into a web. In one aspect, the basis weight of the web is relatively low. For instance, the basis weight of the fibrous web can be less than or equal to about 30 g/m2, such as less than or equal to about 24 g/m2, such as less than or equal to about 23 g/m2, such as less than or equal to about 22 g/m2, such as less than or equal to about 21 g/m2, such as less than or equal to about 20 g/m2, such as less than or equal to about 18 g/m2, such as less than or equal to about 16 g/m2, The basis weight is generally greater than or equal to about 10 g/m2, such as greater than or equal to about 12 g/m2. In one particular aspect, the basis weight of the fibrous web is from about 12 g/m2 to about 22 g/m2, including all increments of 1 g/m2 therebetween.
A coating is applied to the fibrous web. The coating can form a layer on one side of the fibrous web or can be impregnated into the web. In one aspect, a portion of the coating can be impregnated into the web while the coating also forms a surface layer on the web.
The coating comprises a transparency agent that is applied to the fibrous web. The transparency agent can comprise a bio-based wax or oil. The bio-based wax or oil, for instance, can be derived from animal or plant biomass. In one aspect, the transparency agent can be a bio-based wax or oil derived from at least 80% by weight vegetable oils, such as at least about 90% by weight vegetable oils, such as up to 100% by weight vegetable oils. The bio-based wax or oil can be paraffin-free and can be free of mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons. In one aspect, the paper product can be constructed such that the product is also free from petroleum-based chemicals, including polymers. For example, the paper product can be free from petroleum-based polyolefin polymers, petroleum-based polyester polymers, and the like.
Of particular advantage, the transparency agent can meet all government requirements for food contact and food handling. For instance, the low opacity paper can meet all of the requirements of FDA 21 CFR § 176.180 which is directed to components of paper and paperboard that is in contact with dry food. Similarly, the transparency agent and the low opacity paper can also meet all of the requirements of European Commission Regulation No. 1935/2004 regarding materials and articles intended to come in contact with food.
The bio-based wax, in one embodiment, can have a melting point of from about 25° C. to about 75° C., including all increments of 1° C. therebetween. The melting point of the bio-based wax can be less than or equal to about 70° C., such as less than or equal to about 65° C., such as less than or equal to about 60° C., such as less than or equal to about 55° C., such as less than or equal to about 50° C., such as less than or equal to about 45° C., such as less than or equal to about 40° C. The melting point of the bio-based wax can be greater than or equal to about 25° C., such as greater than or equal to about 30° C., such as greater than or equal to about 35° C., such as greater than or equal to about 40° C., such as greater than or equal to about 45° C., such as greater than or equal to about 50° C. A bio-based wax can be selected having a particular melting point that is well suited for a particular application.
In one particular embodiment, the transparency agent comprises a bio-based wax that is a coconut-based wax, a palm-based wax, a soy-based wax, or mixtures thereof.
In one aspect, for instance, the transparency agent is a coconut-based wax or oil. The coconut-based wax can have a melting point of from about 25 degrees C. to about 45 degrees C., such as from about 30 degrees C. to about 40 degrees C. The coconut-based wax can be applied to the fibrous web as an anionic, aqueous dispersion.
In another aspect, the transparency agent can be a palm-based wax or oil. The palm-based wax can have a melting point of from about 50 degrees C. to about 70 degrees C., such as from about 55 degrees C. to about 65 degrees C. The palm-based wax can be applied to the fibrous web as an anionic, aqueous dispersion.
Alternatively, the transparency agent can be a soy-based wax and can be applied in the form of an aqueous cationic emulsion having a melting point of from about 55 degrees C. to about 80 degrees C., such as from about 63 degrees C. to about 72 degrees C.
In one aspect, the bio-based wax can be water dispersible or water miscible. Thus, the transparency agent can be incorporated into an aqueous composition for application to the fibrous web in producing the low opacity paper.
The transparency agent can be applied to the fibrous web using any suitable method or technique. For example, in one embodiment, an aqueous composition containing the transparency agent can be applied to the fibrous web using a size press either at the wet end of the papermaking machine or after the web has been dried. By using a size press, the low opacity paper can be produced in a single process. Alternatively, however, the fibrous web can be formed and then later coated with a composition containing the transparency agent. Coating can be performed using any suitable method including air knife coating, roll-to-roll coating, blade coating, spray coating, Mayer rod coating, direct gravure printing, offset gravure printing, reverse gravure printing, smooth roll coating, curtain coating, bead coating, slot coating, fill press coating, and the like.
Once the transparency agent has been applied to the fibrous web and dried, the fibrous web can be calendered without being supercalendered. In one aspect, a plain filigree press may be used for a glazing effect on the surface of the product. The calender rolls, for instance, can include a hard roll opposite a soft roll. The pressure applied to the coated paper can be greater than or equal to about 200 kPa (2 bar), such as greater than or equal to about 400 kPa (4 bar), such as greater than or equal to about 500 kPa (5 bar), and generally less than or equal to about 1200 kPa (12 bar), such as less than or equal to about 1000 kPa (10 bar), such as less than or equal to about 800 kPa (8 bar), such as less than or equal to about 700 kPa (7 bar). Calendering can occur at ambient temperature or, alternatively, one or both of the calender rolls can be heated.
The amount of transparency agent incorporated into the low opacity paper can depend upon various factors including the basis weight of the paper and the desired opacity that is to be reached. In general, the transparency agent, such as a bio-based wax, can be present in the coated paper in an amount of from about 10% by weight to about 50% by weight, including all increments of 1% by weight therebetween. For instance, the transparency agent can be incorporated into the coated paper in an amount greater than or equal to about 5% by weight, such as in an amount greater than or equal to about 10% by weight, such as in an amount greater than or equal to about 12% by weight, such as in an amount greater than or equal to about 14% by weight, such as in an amount greater than or equal to about 16% by weight. The transparency agent can be present in the coated paper, in one aspect, in an amount less than or equal to about 50% by weight, such as in an amount less than or equal to about 40% by weight, such as in an amount less than or equal to about 30% by weight, such as in an amount less than or equal to about 25% by weight, such as in an amount less than or equal to about 22% by weight.
The amount of transparency agent applied to the low opacity paper can also be described on a weight per area basis. The transparency agent, for instance, can be applied to the fibrous web in an amount greater than or equal to about 3 g/m2, such as in an amount greater than or equal to about 4 g/m2, such as in an amount greater than or equal to about 5 g/m2, such as in an amount greater than or equal to about 6 g/m2, such as in an amount greater than or equal to about 7 g/m2, such as in an amount greater than or equal to about 8 g/m2, such as in an amount greater than or equal to about 9 g/m2, such as in an amount greater than or equal to about 10 g/m2. The transparency agent can be applied to the fibrous web in an amount less than or equal to about 25 g/m2, such as in an amount less than or equal to about 20 g/m2, such as in an amount less than or equal to about 15 g/m2, such as in an amount less than or equal to about 10 g/m2.
In one embodiment, coating composition applied to the fibrous web can contain at least one coloring agent. The coloring agent can be a die, a pigment, or mixtures thereof. In this manner, the final product can display a color and remain translucent.
The transparency agent can improve various properties and characteristics of the coated paper. For instance, the transparency agent can increase the transparency and/or decrease the opacity of the final product. The transparency agent can also reduce the permeability of the low opacity paper and increase the barrier properties of the paper.
In addition to having a relatively low opacity, the coated paper can have a relatively low thickness or caliper. For example, the thickness of the paper can be less than or equal to about 50 μm, such as less than or equal to about 45 μm, such as less than or equal to about 40 μm, such as less than or equal to about 35 μm, such as less than or equal to about 30 μm, such as less than or equal to about 25 μm. The paper generally has a thickness of greater than or equal to about 10 μm, such as greater than or equal to about 15 μm, such as greater than or equal to about 18 μm, such as greater than or equal to about 20 μm.
Low opacity papers described herein not only display low opacity but also display a beneficial blend of other properties. For instance, the coated paper can have a Gurley air permeability of less than or equal to about 45,300 seconds, such as less than or equal to about 20,000 seconds, such as less than or equal to about 10,000 seconds, such as less than or equal to about 1000 seconds, and generally greater than or equal to about 200 seconds.
The low opacity paper can also have a water resistance greater than 10 min according to TAPPI T 432 cm-09. The paper product can have a water vapor barrier at 23° C. and 50% HR of less or equal to than 100 g/m2/day, such as less than or equal to 50 g/m2/day according to ASTM E96/E96M—15:2014.
The low opacity paper has numerous uses and applications. For instance, the low opacity paper can be used as a packaging material for food, tobacco, cosmetics, or pharmaceuticals. In other embodiments, the low opacity paper can be used as a packaging of cigarette packs, cigarette cartons, cigars packages, Heat-non-Burn packs and Heat-non-Burn cartons. The low opacity paper, for instance, can be made to be flexible or semi-rigid making the product well suited for constructing packages. Alternatively, the low opacity paper can be laminated to a paper or a paperboard and formed into a container, such as a box or a bag. In still another embodiment, the low opacity paper can be used as a tracing paper.
Methods for producing a low opacity paper are also provided herein. One such method includes forming a fibrous web from a fiber furnish. The fibrous web, for instance, can be a wetlaid web. The fibrous web is then coated with an aqueous composition containing the transparency agent as described above. Any suitable technique can be used to coat the fibrous web. For instance, in one aspect, the fibrous web can be coated using a size press or bar coating.
The coating applied to the fibrous web can be dried and then can be calendered or not. The resulting coated paper can have an opacity of less than or equal to about 20% and can have a thickness of less than or equal to about 40 μm, such as less than or equal to about 37 μm. The basis weight of the coated paper can be less than or equal to about 30 g/m2, such as from about 19 g/m2 to about 24 g/m2.
According to one embodiment, a paper product comprises: a fibrous web comprising/containing cellulose fibers, wherein the cellulose fibers are 100% refined softwood fibers, the fibrous web having a basis weight of between 10-24 g/m2; and a transparency agent coating the fibrous web, wherein the transparency agent comprises a coconut-based wax, a palm-based wax or a soy-based wax; wherein the paper product displays an opacity of less or than or equal to 20%, preferably less than or equal to 19%, when tested according to ISO 2471:2008; and wherein the paper product has a basis weight of less than or equal to 30 g/m2. The thickness of this embodiment of the paper product is preferably 25-40 μm, more preferably 30-40 μm.
According to another embodiment, a paper product comprises: a fibrous web comprising/containing cellulose fibers, wherein the cellulose fibers are 100% refined softwood fibers, the fibrous web having a basis weight of between 10-18 g/m2; and a transparency agent coating the fibrous web, wherein the transparency agent comprises a palm-based wax and colorant; wherein the paper product displays an opacity of less than or equal to 20%, preferably less than or equal to 18%, when tested according to ISO 2471:2008; and wherein the paper product has a basis weight of less than or equal to 20 g/m2. The thickness of this embodiment of the paper product is preferably 20-30 μm.
Low opacity papers were made and tested for various properties. Two papers were formed from a fibrous web containing 100% refined softwood fibers. The fibrous web was coated with a transparency agent comprising a coconut-based wax using a bar coating technology.
The first low opacity paper had a basis weight of about 28 g/m2 (22 g/m2 fibrous web basis weight+6 g/m2 wax coating) and a thickness of 38 μm. The opacity of the coated paper was 17.9%. The opacity was reduced 42% in comparison to the fibrous web itself (opacity of fibrous web was 31%). The fibrous web had a Schopper-Riegler freeness value of 82° SR. The coated paper displayed a Gurley air permeability of 45,200 seconds, which was over 44,000% greater than the fibrous web itself (Gurley air permeability of fibrous web was 987 seconds). The coated paper displayed a water resistance higher than 10 min, which is 1,000% greater than the fibrous web itself (0.8 min for fibrous web). The water vapor transfer rate at 23° C. and 50% HR was 50 g/m2/day and was reduced by about 83% in comparison to the fibrous web (the water vapor transfer rate at 23° C. and 50% HR of fibrous web was 295 g/m2/day).
The second low opacity paper m had a basis weight of about 19 g/m2 (14 g/m2 fibrous web basis weight+5 g/m2 wax coating) and a thickness of 30 μm. The opacity of the coated paper was 14%. The opacity was reduced 33% in comparison to the fibrous web itself (opacity of fibrous web was 21%). The fibrous web had a Schopper-Riegler freeness value of 86° SR. The coated paper displayed a Gurley air permeability of 484 seconds, which was over 270% greater than the fibrous web itself (Gurley air permeability of fibrous web was 128 seconds). The coated paper displayed a water drop resistance higher than 10 min, which is 1,000% greater than the fibrous web itself (0.8 min for fibrous web). The water vapor transfer rate at 23° C. and 50% HR was 50 g/m2/day and was reduced about 85% in comparison to the fibrous web (the water vapor transfer rate at 23° C. and 50% HR of fibrous web was 330 g/m2/day).
A low opacity paper was made and tested for various properties. The paper was formed from a fibrous web containing 100% refined softwood fibers and having a Schopper-Riegler freeness value of 86° SR. The fibrous web was coated with a transparency agent comprising a palm-based wax using a bar coating technology.
The low opacity paper had a basis weight of 19 g/m2 (14 g/m2 fibrous web basis weight+5 g/m2 wax coating) and a thickness of 32 μm. The opacity of the coated paper was 14%. The opacity was reduced by 33% in comparison to the fibrous web itself (opacity of fibrous web was 21%). The coated paper displayed a Gurley air permeability of 617 sec, which was over 380% greater than the fibrous web itself (Gurley air permeability of fibrous web was 128 seconds). The coated paper displayed a water drop resistance higher than 10 min, which is 1,000% greater than the fibrous web itself (0.8 min for fibrous web). The water vapor transfer rate at 23° C. and 50% HR was 28 g/m2/day and was reduced about 92% in comparison to the fibrous web (the water vapor transfer rate at 23° C. and 50% HR of fibrous web was 330 g/m2/day).
A low opacity paper was made and tested for various properties. The paper was formed from a fibrous web containing 100% refined softwood fibers and having a Schopper-Riegler freeness value of 86° SR. The fibrous web was coated with a transparency agent comprising a soy-based wax using a bar coating technology.
The low opacity paper had a basis weight of 19 g/m2 (14 g/m2 fibrous web basis weight+5 g/m2 wax coating) and thickness of 37 μm. The opacity of the coated paper was 15%. The opacity was reduced by 27% in comparison to the fibrous web itself (opacity of fibrous web was 21%). The coated paper displayed a Gurley air permeability of 617 seconds, which was over 380% greater than the fibrous web itself (Gurley air permeability of fibrous web was 128 seconds). The coated paper displayed a water drop resistance higher than 10 min, which is 1,000% greater than the fibrous web itself (0.8 min for fibrous web). The water vapor transfer rate at 23° C. and 50% HR was 74 g/m2/day and was reduced by about 78% in comparison to the fibrous web (the water vapor transfer rate at 23° C. and 50% HR of fibrous web was 330 g/m2/day).
A low opacity paper was made and tested for various properties. The paper was formed from a fibrous web containing 100% softwood fibers and having a Schopper-Riegler freeness value of 86° SR. The fibrous web was coated with a transparency agent comprising a coconut-based wax and colorant.
The low opacity paper had a basis weight of 19 g/m2 (14 g/m2 fibrous web basis weight+5 g/m2 colored wax) and a thickness of 27 μm. The colorimetric parameters of the coated paper were L* 37.93, a* 2.19 and b* −3.2 measured according to ISO 5631-1:2022. The opacity of the coated paper was 17%. The opacity was reduced by 19% in comparison to the fibrous web itself (opacity of fibrous web was 21%). The coated paper displayed a Gurley air permeability of 273 seconds, which was over 113% greater than the fibrous web itself (Gurley air permeability of fibrous web was 128 seconds). The coated paper displayed a water drop resistance of minimum 10 min, which is 1,000% greater than the fibrous web itself (0.8 min for fibrous web).
Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiment disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the embodiment being indicated by the following claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 63/505,859, filed Jun. 2, 2023, the complete disclosure of which is incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63505859 | Jun 2023 | US |
