Low opacity paper

Abstract

A low basis weight, low opacity paper is disclosed. The low opacity paper is made from a fiber web containing highly refined cellulose fibers. The fiber web is coated with a bio-based wax such as coconut-based wax, palm-based wax, or soy-based wax. The resulting product may have a relatively low basis weight and relatively low opacity. Therefore, the product may have excellent transparency or translucency characteristics.

Description

Technical Field

[0001] Transparent or translucent materials are used in a wide variety of different applications. Transparency is a highly desirable quality, for example, in packaging materials. For example, packaging materials are necessary to protect products during shipping and sales, but consumers prefer to be able to see the product through the packaging.

Background Art

[0002] In the past, most transparent or translucent materials, including packaging materials, have been formed from plastic materials such as polyester polymers and polyolefin polymers. However, these plastic materials are derived from non-renewable fossil resources, including petroleum-based resources. These resources are not sustainable, not renewable, and produce polymer products that do not easily decompose. Therefore, efforts have been made in the past to generate transparent or translucent materials from renewable resources such as cellulose materials.

[0003] For example, low-opacity or transparent papers have been developed and produced in the past. Transparent paper products have been used, for example, in the form of tracing paper, transparent windows for envelopes, and more recently, packaging papers for cereal, pasta, or bakery products. European Patent Application Publication No. 3483337 relates to semi-transparent or transparent papers suitable for lamination and packaging applications, particularly semi-transparent papers with improved transparency by a coating process.

[0004] In many cases, non-renewable resources or components that do not readily biodegrade were combined with paper to produce transparent or translucent paper. For example, one type of paper produced in the past was made from wood pulp fibers, which may have been combined with enzymes such as xylanase. These substrates typically had a relatively high base weight to provide sufficient strength or other mechanical properties. To reduce the thickness of cellulose paper, compress the paper, and produce transparency, the paper was combined with petroleum-based chemicals or synthetic resins and then fed through supercalendering. As used herein, supercalendering first calenders the paper by compressing it between metal cylinders and rollers. The paper is then fed through an additional set of calendering machines to produce a smoother, shinier paper, referred to as supercalendered paper. A supercalendering machine contains several cylinders alternating between polished metal and a soft, resilient surface. The supercalendering machine applies pressure, heat, and friction to gloss both sides of the paper, making it smooth and / or shiny.

[0005] As mentioned above, transparent or translucent papers produced in the past have various drawbacks and deficiencies. For example, even if the fibers used to produce the paper are derived from renewable resources and are biodegradable and compostable, as stated above, the paper is typically combined with petroleum-based chemicals or other synthetic resins that can thwart the goal of producing materials sourced from living organisms. In addition, while supercalendering can be very effective in altering the properties of paper, the process is extremely energy-intensive.

[0006] Barrier properties against water, water vapor, and grease are also important for packaging materials. Typically, these properties can only be achieved with petroleum-based materials. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] European Patent Application Publication No. 3483337 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Considering the above, there is a current need for low-opacity paper that can be supplied by more than 90% biological sources, and that is biodegradable and / or compostable. There is also a need for low-opacity paper that can be produced without supercalendering and likely using fewer materials such as fewer cellulose fibers. There is also a need for low-opacity paper with good barrier properties. [Means for solving the problem]

[0009] The object of the present invention is to provide an alternative to plastic films currently on the market. More specifically, the disclosure is toward a low opacity paper that does not contain any petroleum-based resources, does not require the paper to be supercalendered, is produced at a relatively low basic weight, and therefore can reduce the energy requirements required to produce the product. The low opacity paper of the disclosure can also be formulated to be fully biodegradable and compostable. In addition, the low opacity paper may have an excellent balance of properties, including high transparency to provide high barrier properties, low permeability, and good mechanical properties for conversion and handling.

[0010] In one embodiment, the disclosure is directed to paper products having low opacity characteristics. The paper products include a fibrous web containing cellulose fibers. The cellulose fibers contained in the web can be purified to a relatively high degree, which can be measured according to the filtration efficiency value. The filtration efficiency value (°SR) generally measures the rate at which a diluted suspension of purified fibers can be drained. The filtration efficiency is measured for drainage by the Schöpper-Riegra method. As used herein, the filtration efficiency may be measured according to DIN EN ISO 5267-1:2000. The cellulose fibers contained in the web may have a degree of purification of about 60°SR or higher, for example, about 70°SR or higher. The fibers generally have a filtration efficiency value of about 100°SR or lower, for example, about 90°SR or lower. The fibrous web may also have a relatively low basic weight. The basic weight of the fibrous web for use in the present invention is about 30 g / m². 2 Preferably about 24 g / m 2 More specifically, approximately 22 g / m 2 The following, and most preferably about 20 g / m² 2 The following, and generally about 10g / m 2 That concludes the explanation. In a preferred embodiment, the basic weight of the fiber web is 10 to 24 g / m². 2 And preferably 10 to 18 g / m² 2 It is within the range. The fiber web defines a first surface and a second surface. As will be readily apparent to those skilled in the art, the first surface and the second surface are the primary surfaces of the fiber web, which may also be referred to as the “upper” and “lower” surfaces and are located opposite each other. According to the present invention, the paper product includes a coating on at least one, preferably one, of the first surface and / or the second surface of the fiber web. The coating includes a transparency agent. The transparency agent includes a bio-based wax or oil. Paper products made in accordance with this disclosure may exhibit an opacity of about 40% or less when tested in accordance with ISO 2471:2008. For example, the opacity may be about 30% or less, for example about 25% or less, for example about 23% or less, for example about 20% or less, for example about 18% or less.

[0011] In one aspect, the fiber web of the paper product has a basis weight of from about 12 g / m 2 to about 24 g / m 2 and preferably up to about 22 g / m 2 and exhibits an opacity of about 25% or less, such as about 23% or less, such as about 20% or less. In another aspect, the fiber web of the paper product has a basis weight of from about 12 g / m 2 to about 22 g / m 2 and exhibits an opacity of about 23% or less, such as about 20% or less, such as about 18% or less. In yet another aspect, the fiber web of the paper product has a basis weight of from about 12 g / m 2 to about 20 g / m 2 and exhibits an opacity of about 20% or less, such as about 19% or less, such as about 18% or less.

[0012] In one aspect, the clarifying agent included in the coating is a wax or oil derived from plants or animals. For example, in one aspect, the clarifying agent is a wax or oil derived from plants. In certain embodiments, the clarifying agent may be coconut-based wax, palm-based wax, and / or soybean-based wax.

[0013] In one aspect, the fiber web may include a wet-laid web. The fiber web may contain wood pulp fibers alone or in combination with bast fibers. Bast fibers are plant fibers collected from the phloem or bast around the stems of dicotyledonous plants. Bast fibers can be obtained, for example, from flax, hemp, ramie, common nettle, kozo, linden, willow, konara, wisteria, and mulberry. From an economic perspective, the bast fibers are preferably obtained from flax, hemp, or ramie. The wood pulp fibers may be, for example, softwood fibers, hardwood fibers, or a combination thereof. The paper product can be produced without containing any paraffin, mineral oil, or hydrocarbon oil. Thus, in one aspect, the paper product may be repulpable and compostable.

[0014] Paper products may contain cellulose fibers in an amount of approximately 50% by weight or more, for example, approximately 60% by weight or more, for example, approximately 65% ​​by weight or more, for example, approximately 70% by weight or more, for example, approximately 75% by weight or more, for example, approximately 80% by weight or more. Cellulose fibers generally exist in paper products in an amount of approximately 95% by weight or less, for example, approximately 90% by weight or less, for example, approximately 85% by weight or less, for example, approximately 80% by weight or less.

[0015] The clarifying agent may be present in the paper product in an amount of about 10% by weight or more, for example, about 15% by weight or more, for example, about 17% by weight or more, for example, about 20% by weight or more. The clarifying agent may generally be present in the paper product in an amount of about 50% by weight or less, for example, about 40% by weight or less, for example, about 30% by weight or less, for example, about 25% by weight or less, for example, about 20% by weight or less. In one embodiment, the clarifying agent may be water-miscible and can be applied to a fiber web as an aqueous composition.

[0016] In one particular embodiment, the fiber web may contain first cellulose fibers mixed with second cellulose fibers. The first cellulose fibers may have an average fiber length shorter than the average fiber length of the second cellulose product. The first cellulose fibers may be present in the fiber web in an amount ranging from about 30% to about 70% by weight, based on the total weight of the fibers contained in the web, and the second cellulose fibers may be present in the fiber web in an amount ranging from about 70% to about 30% by weight. The first cellulose fibers may have an average fiber length ranging from about 2.5 mm to about 5 mm.

[0017] The paper products of this disclosure may have a combination of beneficial properties. For example, the paper products may be relatively thin, having a thickness of about 50 μm or less, for example, about 45 μm or less, for example, about 40 μm or less, and generally about 20 μm or more. The thickness is measured in accordance with EN ISO 534:2011. The paper products may also have a Gurley air permeability measured in accordance with ISO 5636-5:2003, of about 45,200 seconds or less, for example, about 20,000 seconds or less, for example, about 10,000 seconds or less, for example, about 1,000 seconds or less, and generally about 200 seconds or more. The paper products may also have a drip resistance of about 10 minutes or more (using a volume of 2 μL of water in the test) in accordance with TAPPI T 432cm-09. The paper products may have a thickness of 100 g / m² in accordance with ASTM E96 / E96M-15:2014. 2 Less than / day, for example, 80g / m 2 Less than / day and generally about 0.1g / m 2 It may have a water vapor barrier of 23°C and 50%HR for more than one day.

[0018] The paper products of this disclosure can be used in a wide variety of applications. In one embodiment, this disclosure is directed to packaging paper made from paper products.

[0019] In another embodiment, this disclosure also relates to a method for producing low-opacity paper products as described above. The method includes the step of coating a fiber web with an aqueous composition containing a transparency agent. The transparency agent may include bio-based waxes or oils such as coconut-based wax, palm-based wax and / or soy-based wax. In one embodiment, a size press is used to impregnate the fiber web with the aqueous composition containing the transparency agent. However, in other embodiments, the transparency agent may be applied to the fiber web by using an applicator roll, by knife coating, by spraying, or by using any other suitable coating technique.

[0020] In one embodiment, the fiber web may be a wet-laid web. The method for producing the product may include the steps of: preparing an aqueous suspension of cellulose fibers; purifying the cellulose fibers; depositing the aqueous suspension of fibers onto a porous surface to form a fiber web; and coating the fiber web with an aqueous composition containing a transparent agent.

[0021] Other features and aspects of this disclosure will be discussed in more detail below.

[0022] A full and implementable extent of this disclosure is more specifically specified in the remainder of this Specification, including by reference to the attached figures. [Brief explanation of the drawing]

[0023] [Figure 1] This is a schematic cross-sectional view of one embodiment of low-opacity paper prepared in accordance with this disclosure. [Modes for carrying out the invention]

[0024] The repeated use of reference letters in this specification and drawings is intended to represent the same or similar features or elements of the present invention.

[0025] definition As understood herein, “coating” on the surface of a fiber web can generally be obtained by applying a liquid coating agent to the surface of the fiber web using any suitable coating, impregnation, or saturation technique, such as air knife coating, roll-to-roll coating, blade coating, spray coating, Meyer 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 may be continuous or discontinuous. Thus, along the transverse dimensions of the fiber web, the coating may be present on part or all of the fiber web. When a coating composition is applied to a fiber web, the composition penetrates into some of the internal spaces and pores between the fibers of the fiber web, resulting in saturation and / or impregnation of the fiber web by the coating (composition). That is, in the present invention, the coating permeates into the fiber web, particularly into the internal spaces and pores therein, and separately, at least a portion of the first and / or second surfaces of the fiber web can be covered in the form of a surface coating, preferably. In other words, “coating” as understood herein encompasses the saturation and impregnation of the fiber web.

[0026] As used herein, the term "low opacity" means transparent or translucent. A product is considered to have low opacity if, when tested according to ISO 2471:2008, it exhibits an opacity of, for example, about 45% or less. Low opacity characteristics refer to features that provide transparency or translucency to a paper product, such as the presence of a transparent agent.

[0027] As used herein, the term “clarifier” refers to a substance that, when applied to the inside or on top of a fiber web, reduces the opacity of the fiber web. Examples include plant or animal-derived waxes or oils, such as coconut-based waxes, palm-based waxes, and / or soy-based waxes. Plant or animal-derived ingredients as understood herein can be obtained from biomass.

[0028] As used herein, the term “biomass” is broadly understood to encompass all types of plant and animal materials and materials derived therefrom. Biomass does not include petroleum or petroleum-derived products.

[0029] The biomass used in the present invention may include high-molecular-weight compounds, such as lignin and polysaccharides, including starch, cellulose, and hemicellulose.

[0030] As can be seen, certain types of biomass may include both plant and animal-derived materials. Examples include manure (feces), human waste, and sewage sludge. The biomass for use in the present invention is preferably plant biomass, i.e., biomass of or derived from plants, but may contain a certain amount of animal biomass (i.e., biomass of or derived from animals). For example, the biomass may contain up to 30% animal biomass. According to a preferred embodiment, the biomass for use in this disclosure is preferably plant biomass and contains 70 wt% or more, most preferably 90 wt% or more, of polysaccharides and lignin in terms of the solid content of the biomass.

[0031] For example, plant biomass may be agricultural plant material (e.g., agricultural waste) or any kind of woody material. The biomass may also be in the form of waxes and oils, including coconut, palm, and soybean waxes and oils.

[0032] As used herein, a "biodegradable" component is a component that can be corroded by living organisms such as bacteria or fungi. Therefore, biodegradable components can be corroded by the action of microorganisms such as bacteria or fungi, with or without oxygen. In one embodiment, the biodegradable component satisfies at least one requirement of the international industrial standards ISO 14855:2018, ISO 14853:2017, and ASTM D5338:2015.

[0033] As used herein, the term “compostable” refers to components that can disintegrate into non-toxic, natural elements. Compostable components can decompose at a rate consistent with, for example, similar organic materials. Compostable components decompose when exposed to microorganisms, humidity, and / or heat to produce a mature compost product. Coated papers produced in accordance with this disclosure may be formulated to meet the international industrial standards ISO 17088:2021, DIN EN 13432:2007, DIN EN 14995:2007, and / or ASTM 6400:2021, which define the requirements for industrially compostable components.

[0034] As used herein, the term "pulp" refers to fibers derived 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, African honeysuckle, milkweed, straw, tuna, hemp, sisal, Manila hemp, and bagasse. Pulp fibers may include hardwood fibers, softwood fibers, and mixtures thereof.

[0035] As used herein, the term “fiber web” refers to a sheet made from pulp by a wet-laid process without coating.

[0036] As used herein, the term “bio-based wax or oil” refers to a wax or oil having a bio-based content of 90% by weight or more. “Bio-based wax or oil” is preferably derived from plant biomass. Examples include coconut-based wax, palm-based wax, and / or soy-based wax. According to one embodiment, the bio-based wax or oil is obtained by processing plant material.

[0037] Detailed description Those skilled in the art will understand that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure.

[0038] Generally, this disclosure is directed toward low-opacity paper. In one embodiment, the paper may be transparent. Alternatively, the paper may be formulated to be semi-transparent. The low-opacity paper of this disclosure may be formed exclusively from sustainable resources that meet all requirements for entering the paper recycling stream after use. In the past, for example, transparent paper typically contained components derived from fossil-based resources, such as petroleum-derived products. However, the low-opacity paper of this disclosure can be produced with a bio-based content of more than 90%. In addition, in one embodiment, the low-opacity paper may be formulated to be paraffin-free. As a result, the low-opacity paper may be constructed to meet all requirements for food contact and food handling.

[0039] The low-opacity papers of this disclosure are also advantageous in that they can be constructed to minimize material usage while still possessing sufficient mechanical properties for handling, processing, and end-use applications. For example, the low-opacity papers of this disclosure can be constructed with a relatively low base weight.

[0040] In one embodiment, the low opacity paper of the present disclosure is formed from a fibrous web containing relatively highly refined cellulose fibers. According to the present disclosure, the fibrous web is combined with a clearing agent, which may be a bio-based wax or oil. The clearing agent not only increases the barrier properties of the paper but also decreases its opacity properties. Ultimately, paper with an opacity of about 40% or less, when tested according to ISO 2471:2008, can be produced. For example, the opacity of the paper product may be about 35% or less, for example about 30% or less, for example about 25% or less, for example about 20% or less, for example about 18% or less, and for example even about 16% or less. The actual opacity may be determined by various factors and is generally 1% or more, for example about 5% or more.

[0041] For example, the basic weight of the fiber web used to construct low-opacity paper can affect the opacity. In one embodiment, the fiber web of the paper product is approximately 12 g / m². 2 From approximately 24g / m 2 It has a basic weight up to approximately 25% or less, for example, approximately 23% or less, for example, approximately 20% or less. In another embodiment, the fiber web of a paper product is approximately 12 g / m 2 From approximately 22g / m 2 It has a basic weight up to approximately 23% or less, for example approximately 20% or less, for example approximately 18% or less. In yet another embodiment, the fiber web of a paper product is approximately 12 g / m 2 From approximately 20g / m 2 It has a basic weight up to a certain point and exhibits an opacity of approximately 20% or less, for example, approximately 19% or less, for example, approximately 18% or less.

[0042] Referring to Figure 1, one embodiment of a low-opacity paper or paper product 10 prepared according to this disclosure is shown. Figure 1 represents a schematic cross-sectional view of the product 10. As shown, in this embodiment, the low-opacity paper 10 includes a paper substrate sheet 12 which is a fibrous web formed from cellulose fibers. The fibrous web 12 may be, for example, a wet-laid paper web. However, in other embodiments, the fibrous web 12 may be prepared using any preferred papermaking technique. The fibrous web 12 includes a first surface opposite a second surface. Applied to the first surface of the fibrous web 12 is a coating 14. The coating 14 contains a transparency agent that reduces the opacity of the paper product 10. The coating 14 is shown as a separate layer in Figure 1, but as described above, it will also be impregnated into the fibrous web 12. As will be described in more detail below, the coating 14 may be prepared from a bio-based oil or wax. In one particular embodiment, for example, the coating 14 is formed from coconut-based wax, palm-based wax, and / or soy-based wax.

[0043] As shown in Figure 1, the low-opacity paper 10 can be exclusively produced from a single layer of fiber web combined with a coating 14. Alternatively, the low-opacity paper 10 may include a second coating (not shown) applied to the opposite side of the fiber web, such as a heat-sealable coating.

[0044] As described above, in one embodiment, the fiber web 12 may be a wet-laid paper web formed from cellulose fibers. For example, the fiber web may be formed from an aqueous suspension of fibers. The cellulose fibers contained in the fiber web may be pulp fibers including wood pulp fibers, plant waste fibers, or other plant fibers. When forming the fiber web, the aqueous suspension of fibers can be deposited on a porous surface that drains water, thereby forming the fiber web.

[0045] In one embodiment, the fiber web is made primarily from plant-derived or natural fibers. Natural (plant-derived) fibers may be selected from chemical pulps such as sulfate and sulfite pulps, organosolve pulps, regenerated fibers, and / or mechanical pulps, kraft wood pulp, medium-density fiberboard fibers, nanocellulose, and their modifiers and combinations. The pulp may be bleached or unbleached. The pulp may originate from hardwoods or softwoods, including birch, beech, aspen (such as European aspen), alder, eucalyptus, maple, acacia, mixed tropical hardwoods, pine (such as loblolly pine), fir, hemlock, larch, spruce (such as black spruce or Norway spruce), and mixtures thereof.

[0046] Non-woody plant fibers such as seed hair fibers, leaf fibers, and bast fibers may be used. Plant fibers can be provided, for example, from grain straw, wheat straw, reed, rush, flax, hemp, kenaf, tuna, ramie, seeds, sisal, Manila hemp, koia, bamboo, bagasse, cotton kapok, milkweed, pineapple, cotton, rice, reed, African feather grass, Phalaris arundinacea, or combinations thereof.

[0047] Fiber webs can be formed primarily from cellulose fibers without being combined with other components such as fillers. For example, a fiber web (before coating) may contain cellulose fibers in an amount of about 90% or more by weight, for example, about 95% or more by weight. Specific cellulose fibers well suited for producing fiber webs include softwood fibers, hardwood fibers, birch fiber, hemp fiber, or mixtures thereof. For example, in one embodiment, a fiber web may be made exclusively from softwood fibers alone or in combination with hardwood fibers. Alternatively, a fiber web may be made from a mixture of wood pulp fibers such as softwood fibers and bast fibers such as hemp or linseed fiber. Cellulose fibers may be selected, for example, to produce webs that can be efficiently drained from aqueous fluids during formation and produce relatively low opacity paper at a lower basic weight while still retaining the mechanical properties required for processing and handling.

[0048] Once a suitable fibrous pulp for producing a fibrous web has been selected, in one embodiment, the fibers used to form the web after pulping may be fed through a purification process to increase the drainability value, expressed in units of "°SR", which is measured for drainability by the Schöpper-Riegra method (ISO 5267-1:2000). As used herein, purifying cellulose fibers is different from producing pulp fibers. During pulping, lignin is removed from the cellulose fibers. On the other hand, during purification, the fuzz of individual small fibers that make up the outer surface or wall of the fibers is raised, which is sometimes called beating. Purification is the mechanical and / or chemical action that causes beating.

[0049] In one embodiment, when preparing fibers for producing a fiber web, the fibers may first undergo suitable pretreatment such as washing, and may be chopped, especially if bast fibers are used. In addition, the fibers may be fed through a hammer mill or subjected to various different chemical treatments.

[0050] Cellulose fibers can be mixed with an aqueous solution or solvent, which may occur in a refining machine such as a twin-screw machine. If desired, a wetting agent, acid, or alkali may be added to soften the cellulose fibers. In addition, one or more alcohols, including methyl alcohol, ethyl alcohol, or mixtures thereof, may be added to the fibers.

[0051] The aqueous suspension can be fed into or formed within a purifier and subjected to mechanical purification. The viscosity of the fibers in the purifier can have a solid content ranging from approximately 1% to approximately 30%. In a purifier such as a twin-screw purifier, the pulp suspension is subjected to mechanical action that generates the formation of larger subfibers within each fiber.

[0052] It should be understood that any suitable refining device may be used to increase the water filtration efficiency of the fibers, and that twin-screw refining machines represent only one possible device, process, or technology.

[0053] After exiting one or more purifiers, the cellulose fibers, in accordance with this disclosure, have a filtration efficiency of approximately 60°SR or higher, for example, approximately 65°SR or higher, for example, approximately 67°SR or higher, for example, approximately 70°SR or higher. In one embodiment, the cellulose fibers are purified to approximately 72°SR or higher, for example, approximately 74°SR or higher, for example, approximately 76°SR or higher, for example, approximately 78°SR or higher, for example, approximately 80°SR or higher. The filtration efficiency of the fibers is generally approximately 95°SR or lower, for example, approximately 90°SR or lower, for example, approximately 88°SR or lower, for example, approximately 85°SR or lower, for example, approximately 80°SR or lower. It has been found that purifying the fibers to the extent described above not only improves the effluent of the web being produced but also reduces the opacity characteristics of the paper. Purifying the cellulose fibers also allows for a reduction in sheet thickness while still providing good mechanical properties. Reducing the thickness relative to a given base weight has been shown to unexpectedly improve transparency while still maintaining an excellent balance with mechanical properties, for example. Adjusting the level of cellulose fiber refinement also allows for adjustment of the barrier properties of low-opacity paper. For example, fiber refinement can be used to adjust air permeability and develop air barrier properties, water barrier properties, oil barrier properties, etc.

[0054] Once the cellulose fibers are purified, they are formed into a web. In one embodiment, the basic weight of the web is relatively low. For example, the basic weight of a fibrous web is approximately 30 g / m². 2 For example, approximately 24g / m 2 For example, approximately 23g / m 2 For example, approximately 22g / m 2 For example, approximately 21g / m 2 For example, approximately 20g / m 2For example, approximately 18g / m 2 For example, approximately 16g / m 2 The following is also acceptable. The basic weight is generally about 10g / m 2 To give an example, it's approximately 12g / m 2 That is all. In one particular embodiment, the basic weight of the fiber web is 1 g / m². 2 Including all increments, approximately 12g / m 2 From approximately 22g / m 2 That is the end.

[0055] In accordance with this disclosure, the coating is applied to a fiber web. The coating may form a layer on one side of the fiber web or it may be impregnated into the web. In one embodiment, the coating may also form a surface layer of the web, while a portion of the coating is impregnated into the web.

[0056] According to this disclosure, the coating includes a clarifier applied to a fiber web. The clarifier may include a bio-based wax or oil. The bio-based wax or oil may be derived, for example, from animal or plant biomass. In one embodiment, the clarifier may be a bio-based wax or oil derived from at least 80% by weight of vegetable oil, e.g., at least about 90% by weight of vegetable oil, e.g., up to 100% by weight of vegetable oil. The bio-based wax or oil may be paraffin-free and may not contain mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons. Particularly advantageous is that the clarifier can meet all government requirements for food contact and food handling. For example, the low opacity paper of this disclosure can meet all the requirements of FDA Section 21 CFR 176.180, which is directed to components of paper and cardboard that come into contact with dry food. Similarly, the clarifier and the low opacity paper can meet all the requirements of European Commission Regulation 1935 / 2004 on materials and articles intended to come into contact with food.

[0057] In one embodiment, the bio-based wax may have a melting point ranging from about 25°C to about 75°C, including all increments of 1°C in between. The melting point of the bio-based wax may be about 70°C or less, for example, about 65°C or less, for example, about 60°C or less, for example, about 55°C or less, for example, about 50°C or less, for example, about 45°C or less, for example, about 40°C or less. The melting point of the bio-based wax may be about 25°C or more, for example, about 30°C or more, for example, about 35°C or more, for example, about 40°C or more, for example, about 45°C or more, for example, about 50°C or more. A bio-based wax having a specific melting point that is well suited to a particular application may be selected.

[0058] In one particular embodiment, the clearing agent comprises a bio-based wax, which is a coconut-based wax, a palm-based wax, a soy-based wax, or a mixture thereof.

[0059] In one embodiment, for example, the clarifier is a coconut-based wax or oil. The coconut-based wax may have a melting point between approximately 25 degrees Celsius and approximately 45 degrees Celsius, for example, between approximately 30 degrees Celsius and approximately 40 degrees Celsius. The coconut-based wax can be applied to a fiber web as an anionic aqueous dispersion.

[0060] In another embodiment, the transparency agent may be a palm-based wax or oil. The palm-based wax may have a melting point of about 50 to 70 degrees Celsius, for example, about 55 to 65 degrees Celsius. The palm-based wax may be applied to a fiber web as an anionic aqueous dispersion.

[0061] Alternatively, the clarifier may be a soybean-based wax and can be applied in the form of a cationic aqueous emulsion having a melting point from approximately 55 degrees Celsius to approximately 80 degrees Celsius, for example, from approximately 63 degrees Celsius to approximately 72 degrees Celsius.

[0062] In one embodiment, the bio-based wax may be water-dispersible or water-miscible. Therefore, the transparency agent may be incorporated into an aqueous composition for application to a fiber web when producing low-opacity paper.

[0063] The transparency agent can be applied to the fiber web using any preferred method or technique. For example, in one embodiment, an aqueous composition containing the transparency agent can be applied to the fiber web using a size press, either at the wet end of the papermaking machine or after the web has dried. By using a size press, low opacity paper can be produced in a single process. However, alternatively, the fiber web can be formed and then coated with a composition containing the transparency agent. The coating can be carried out using any preferred 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.

[0064] After applying the clearing agent to the fiber web and allowing it to dry, the fiber web can be calendered without supercalendering. In one embodiment, a plain filigree press may be used for a glossy effect on the surface of the product. The calender rolls may include, for example, a hard roll on the opposite side of a soft roll. The pressure applied to the coated paper may be about 200 kPa (2 bar) or more, for example about 400 kPa (4 bar) or more, for example about 500 kPa (5 bar) or more, and generally about 1200 kPa (12 bar) or less, for example about 1000 kPa (10 bar) or less, for example about 800 kPa (8 bar) or less, for example about 700 kPa (7 bar) or less. Calendering can be performed at ambient temperature, or alternatively, one or both of the calender rolls may be heated.

[0065] The amount of transparency agent incorporated into low-opacity paper can be determined by various factors, including the base weight of the paper and the desired opacity to be achieved. Generally, transparency agents such as bio-based waxes can be present in coated paper in amounts ranging from about 10% to about 50% by weight, including all increments of 1% by weight in between. For example, the transparency agent may be incorporated into coated paper in amounts of about 5% by weight or more, for example, about 10% by weight or more, for example, about 12% by weight or more, for example, about 14% by weight or more, for example, about 16% by weight or more. In one embodiment, the transparency agent may be present in coated paper in amounts of about 50% by weight or less, for example, about 40% by weight or less, for example, about 30% by weight or less, for example, about 25% by weight or less, for example, about 22% by weight or less.

[0066] The amount of transparency agent applied to low-opacity paper can also be described based on weight per unit area. For example, the amount of transparency agent applied to a fiber web is approximately 3 g / m². 2 For example, the above amount is approximately 4g / m 2 For example, the amount mentioned above is approximately 5g / m 2 For example, the above amount is approximately 6g / m 2 For example, the amount mentioned above is approximately 7g / m 2 For example, the above amount is approximately 8g / m 2 For example, the above amount is approximately 9g / m 2 For example, the above amount is approximately 10g / m 2 The above amount can be applied. Apply the clearing agent to the fiber web at approximately 25 g / m². 2 For example, the amount is approximately 20g / m². 2 For example, the amount is approximately 15g / m². 2 For example, the following amounts are used: approximately 10g / m 2 It can be applied in the following quantities.

[0067] In one embodiment, the coating composition applied to the fiber web may contain at least one colorant. The colorant may be a dye, a pigment, or a mixture thereof. In this manner, the final product may exhibit color and remain translucent.

[0068] Transparent agents can improve various properties and characteristics of coated paper. For example, transparent agents can increase the transparency and / or decrease the opacity of the final product. Transparent agents can also reduce the permeability of low-opacity paper and increase the barrier properties of paper.

[0069] In addition to having relatively low opacity, the coated paper of this disclosure may have relatively low thickness or caliper. For example, the thickness of the paper may be about 50 μm or less, for example about 45 μm or less, for example about 40 μm or less, for example about 35 μm or less, for example about 30 μm or less, for example about 25 μm or less. Generally, the paper has a thickness of about 10 μm or more, for example about 15 μm or more, for example about 18 μm or more, for example about 20 μm or more.

[0070] Low opacity papers produced in accordance with this disclosure not only offer low opacity but also offer beneficial admixtures of other properties. For example, coated papers may have a Gurley permeability of about 45,300 seconds or less, for example about 20,000 seconds or less, for example about 10,000 seconds or less, for example about 1,000 seconds or less, and generally about 200 seconds or more.

[0071] Low opacity paper may also have water-resistant properties of 10 minutes or more, according to TAPPI T 432cm-09. Paper products shall be 100 g / m² in accordance with ASTM E96 / E96M-15:2014. 2 Less than / day, for example, 50g / m 2 It may have a water vapor barrier of less than / day at 23°C and 50%HR.

[0072] The low opacity paper of this disclosure has numerous uses and applications. For example, low opacity paper can be used as packaging material for food, tobacco, cosmetics, or pharmaceuticals. In other embodiments, low opacity paper can be used as packaging for cigarette packs, cigarette cartons, cigar packages, heated (heated non-combustible) packs, and heated (heated non-combustible) cartons. Low opacity paper can be manufactured to be flexible or semi-rigid, for example, to make the product well-suited for packaging construction.

[0073] Alternatively, low-opacity paper can be laminated onto paper or cardboard to form containers such as boxes or bags.

[0074] In another embodiment, low-opacity paper can be used as tracing paper.

[0075] In addition to being directed towards low-opacity paper and products made from such paper, this disclosure is also directed towards methods for producing low-opacity paper. The method includes the step of forming a fiber web from a fiber-finished paper stock. The fiber web may be, for example, a wet-laid web. The fiber web is then coated with an aqueous composition containing a transparency agent as described above. The fiber web can be coated using any preferred technique. For example, in one embodiment, the fiber web may be coated using a size press or bar coating.

[0076] The coating applied to the fiber web can be dried and then calendered or not. The resulting coated paper may have an opacity of about 20% or less and a thickness of about 40 μm or less, for example, about 37 μm or less. The basic weight of the coated paper is about 30 g / m². 2 For example, approximately 19g / m 2 From approximately 24g / m 2 It's fine up to that point.

[0077] According to embodiments of the present invention, the paper product is a fiber web containing cellulose fibers, wherein the cellulose fibers are 100% purified soft fiber, and the fiber web has a density of 10-24 g / m². 2 A fiber web having a basic weight between 30g and 30g / m², and a clearing agent for coating the fiber web, comprising coconut-based wax, palm-based wax, or soy-based wax, exhibiting an opacity of 20% or less, preferably 19% or less, when tested according to ISO 2471:2008, and comprising a fiber web with a basic weight between 30g and 30g / m². 2 The following basic weights are present. The thickness of this embodiment of the paper product according to the present invention is preferably 25 to 40 μm, more preferably 30 to 40 μm.

[0078] According to another embodiment of the present invention, the paper product is a fiber web containing cellulose fibers, wherein the cellulose fibers are 100% purified soft fiber, and the fiber web has a density of 10-18 g / m². 2 A fiber web having a basic weight between 20g and 20g / m², and a transparent coating agent for the fiber web, comprising a palm-based wax and a colorant, exhibiting an opacity of 20% or less, preferably 18% or less, when tested according to ISO 2471:2008, and 20g / m² 2 The following basic weights are present. The thickness of this embodiment of the paper product according to the present invention is preferably 20 to 30 μm.

[0079] This disclosure may be better understood by referring to the following examples. [Examples]

[0080] Low-opacity paper was prepared in accordance with this disclosure and tested for various properties. Two types of paper were formed from a fiber web containing 100% refined softwood fibers. The fiber web was coated with a transparent agent containing coconut-based wax using a bar coating technique.

[0081] The first low-opacity paper produced in accordance with this disclosure is approximately 28 g / m². 2 Basic weight (22g / m 2Fiber web base weight + 6g / m 2 The coated paper had a wax coating and a thickness of 38 μm. The opacity of the coated paper was 17.9%. The opacity was reduced by 42% compared to the fiber web itself (the fiber web's opacity was 31%). The fiber web had a Schöpper-Riegra water permeability value of 82°SR. The coated paper exhibited a Guarley permeability of 45,200 seconds, which was 44,000% higher than the fiber web itself (the fiber web's Guarley permeability was 987 seconds). The coated paper exhibited water resistance higher than 10 minutes, which was 1,000% higher than the fiber web itself (0.8 minutes for the fiber web). The water vapor transfer rate at 23°C and 50%HR was 50 g / m³ 2 This represents a reduction of only about 83% compared to the fiber web (the water vapor transfer rate of the fiber web at 23°C and 50% HR was 295 g / m²). 2 (It was / day)

[0082] The second low-opacity paper produced in accordance with this disclosure is approximately 19 g / m². 2 Basic weight (14g / m 2 Fiber web base weight + 5g / m 2 The coated paper had a wax coating and a thickness of 30 μm. The opacity of the coated paper was 14%. The opacity was 33% lower compared to the fiber web itself (the fiber web's opacity was 21%). The fiber web had a Schöpper-Riegra water permeability value of 86°SR. The coated paper exhibited a Gurley permeability of 484 seconds, which was 270% higher than the fiber web itself (the fiber web's Gurley permeability was 128 seconds). The coated paper exhibited water resistance higher than 10 minutes, which was 1,000% higher than the fiber web itself (0.8 minutes for the fiber web). The water vapor transfer rate at 23°C and 50%HR was 50 g / m³ 2 This represents a reduction of approximately 85% compared to the fiber web (the water vapor transfer rate of the fiber web at 23°C and 50% HR was 330 g / m²). 2 (It was / day) [Examples]

[0083] Low opacity paper was prepared in accordance with this disclosure and tested for various properties. Paper was formed from a fiber web containing 100% purified softwood fibers and having a Schöpper-Liegura water filtration value of 86°SR. The fiber web was coated with a clearing agent containing palm-based wax using a bar coating technique.

[0084] The low-opacity paper produced in accordance with this disclosure is 19 g / m². 2 Basic weight (14g / m 2 Fiber web base weight + 5g / m 2 The coated paper had a wax coating and a thickness of 32 μm. The opacity of the coated paper was 14%. The opacity was reduced by only 33% compared to the fiber web itself (the fiber web's opacity was 21%). The coated paper exhibited a Guarley permeability of 617 seconds, which was 380% higher than the fiber web itself (the fiber web's Guarley permeability was 128 seconds). The coated paper exhibited a watertightness of more than 10 minutes, which was 1,000% higher than the fiber web itself (0.8 minutes for the fiber web). The water vapor transfer rate at 23°C and 50% HR was 28 g / m³ 2 This represents a reduction of approximately 92% compared to the fiber web (the water vapor transfer rate of the fiber web at 23°C and 50% HR was 330 g / m²). 2 (It was / day) [Examples]

[0085] Low opacity paper was prepared in accordance with this disclosure and tested for various properties. Paper was formed from a fiber web containing 100% refined softwood fibers and having a Schöpper-Liegra water filtration value of 86°SR. The fiber web was coated with a clearing agent containing soy-based wax using a bar coating technique.

[0086] The low-opacity paper produced in accordance with this disclosure is 19 g / m². 2 Basic weight (14g / m 2 Fiber web base weight + 5g / m 2The coated paper had a wax coating and a thickness of 37 μm. The opacity of the coated paper was 15%. The opacity was reduced by only 27% compared to the fiber web itself (the fiber web's opacity was 21%). The coated paper exhibited a Gurley permeability of 617 seconds, which was 380% higher than the fiber web itself (the fiber web's Gurley permeability was 128 seconds). The coated paper exhibited a watertightness of more than 10 minutes, which was 1,000% higher than the fiber web itself (0.8 minutes for the fiber web). The water vapor transfer rate at 23°C and 50% HR was 74 g / m³ 2 This represents a reduction of only about 78% compared to the fiber web (the water vapor transfer rate of the fiber web at 23°C and 50% HR was 330 g / m²). 2 (It was / day) [Examples]

[0087] Low opacity paper was prepared in accordance with this disclosure and tested for various properties. Paper was formed from a fiber web containing 100% soft fiber and having a Schöpper-Liegra water filtration value of 86°SR. The fiber web was coated with a clearing agent containing coconut-based wax and a colorant.

[0088] The low-opacity paper produced in accordance with this disclosure is 19 g / m². 2 Basic weight (14g / m 2 Fiber web base weight + 5g / m 2 It had a colored wax coating and a thickness of 27 μm. The colorimetric parameters of the coated paper were measured according to ISO 5631-1:2022, L * 37.93, a * 2.19 and b * The value was -3.2. The opacity of the coated paper was 17%. The opacity was only 19% lower compared to the fiber web itself (the fiber web's opacity was 21%). The coated paper exhibited a Gurley permeability of 273 seconds, which was 113% higher than the fiber web itself (the fiber web's Gurley permeability was 128 seconds). The coated paper exhibited a minimum water resistance of 10 minutes, which was 1,000% higher than the fiber web itself (0.8 minutes for the fiber web).

[0089] These and other modifications and variations of the present invention can be practiced by those skilled in the art. Embodiments of the present invention are specified in the appended claims. In addition, it should be understood that the various embodiments may be interchangeable, either in whole or in part. [Explanation of Symbols]

[0090] 10 Low opacity paper and paper products 12 Paper substrate sheets, fiber webs 14 Coating

Claims

1. A fiber web containing cellulose fibers, wherein the cellulose fibers have a Schoper-Liegura filtration rate within the range of 60°SR to 95°SR as measured according to ISO 5267:2000, and the fiber web has a density of 30 g / m². ２ The following and 10 g / m ２ Having the above basic weight, a fiber web defining the first surface and the second surface, A coating on a first surface and / or a second surface of a fiber web, preferably on one of the first and second surfaces, comprising a transparent agent containing at least 95% by weight of a bio-based wax or oil, and Paper products including, Paper products that exhibit an opacity of 40% or less when tested according to ISO 2471:2008.

2. The paper product according to claim 1, wherein the cellulose fibers have a Shopper-Liegra water filtration rate in the range of 70°SR to 90°SR.

3. The fiber web is 24 g / m ２ Preferably, the following is 22 g / m ２ More preferably, 20 g / m ２ The following, and 10 g / m ２ The paper product according to claim 1, having the above basic weight.

4. The paper product according to claim 1, which is calendar-finished but not supercalender-finished.

5. The paper product according to claim 1, wherein the bio-based wax or oil is obtained by processing plant material.

6. The paper product according to claim 1, wherein the bio-based wax or oil is a plant-derived wax or oil, preferably having a melting point of 25°C to 75°C.

7. The paper product according to claim 1, wherein the bio-based wax or oil is coconut-based wax, soy-based wax, palm-based wax, rice-based wax, or a mixture thereof.

8. The paper product according to claim 1, having an opacity of 30% or less when tested in accordance with ISO 2471:2008.

9. The paper product according to claim 1, wherein the fiber web includes a wet-laid web.

10. The paper product according to claim 1, which does not contain paraffin, mineral oil, or hydrocarbon oil.

11. The paper product according to claim 1, wherein the fiber web comprises wood pulp fibers alone or in combination with bast fibers.

12. The paper product according to claim 1, having a Gurley air permeability of 45,200 seconds or less, preferably 20,000 seconds or less, more preferably 10,000 seconds or less, even more preferably 1,000 seconds or less, and 200 seconds or more, as measured in accordance with ISO 5636-5:2003.

13. Measured according to ASTM E96 / E96M-15:2014, 100 g / m² ２ Less than 80 g / m² per day, preferably 80 g / m² ２ The paper product according to claim 1, exhibiting water vapor resistance at 23°C and 50% humidity for a period of 1 day or less.

14. The paper product according to claim 1, which exhibits water resistance for 10 minutes or more in accordance with TAPPI T432cm-09.

15. The paper product according to claim 1, wherein the transparent agent is present in the paper product in an amount of 5% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, and 40% by weight or less, preferably 35% by weight or less, more preferably 30% by weight or less.

16. The paper product according to claim 1, which is colored.

17. Use of the paper product according to any one of claims 1 to 16 as packaging paper for food, cosmetics, or pharmaceuticals.

18. Use of the paper product according to any one of claims 1 to 16 as packaging for cigarette packs, cigarette cartons, cigar packages, heated food packs and heated food cartons.

19. A method for producing a paper product according to any one of claims 1 to 16, The process of preparing an aqueous suspension of cellulose fibers, The process of refining cellulose fibers, A step of depositing an aqueous suspension of fibers onto a porous surface to form a fiber web, A process of coating a fiber web with an aqueous composition containing a transparent agent and Methods that include...

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