Porous low-opacity paper

Abstract

Low opacity paper is disclosed. Low opacity paper is made from a fiber web containing unrefined cellulose fibers. The fiber web is coated with a bio-based wax such as coconut-based, palm-based, and soy-based wax. The resulting product may have 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 applications. Transparency is a highly desirable quality, for example, in packaging materials. For instance, packaging materials are necessary to protect products during delivery and sale, but consumers prefer to be able to see the product through the packaging. [Background technology]

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

[0003] For example, low-opacity or transparent paper has 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, wrapping paper for cereals, pasta, or bakery products.

[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 described above, transparent or translucent papers produced in the past have various drawbacks and defects. For example, even if the fibers used to produce the paper are derived from renewable resources and are biodegradable and compostable, as mentioned above, the paper is typically combined with petroleum-based chemicals or other synthetic resins that can thwart the goal of producing bio-sourced materials. In addition, while supercalendering can be very effective in altering the properties of the paper, the process is very energy-intensive. Furthermore, due to the way the paper is formed as described above, the paper has very low porosity, and the process offers little to no control over increasing porosity. [Overview of the project] [Problems that the invention aims to solve]

[0006] 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 compostable. There is also a need for low-opacity paper that can be produced without supercalendering. In one embodiment, there is also a need for low-opacity paper that can be formed with relatively high porosity or permeability. [Means for solving the problem]

[0007] 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 can be constructed without containing any petroleum-based resources and without the need to supercalender the paper, thereby reducing the energy requirements required to manufacture 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 and good mechanical properties for conversion and handling. Furthermore, the porosity of the low-opacity paper can be controlled. Thus, depending on the specific application and desired results, a low-permeability paper or a paper with relatively high permeability or porosity can be formed.

[0008] In one embodiment, the disclosure is directed to a paper product having low opacity characteristics. The paper product comprises a fiber web containing cellulose fibers. At least a portion of the cellulose fibers contained in the web are unpurified, so as 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, for example, about 25°SR or less, for example, about 20°SR or less, for example, about 15°SR or less. The fibers generally have a filtration efficiency value of about 5°SR or more.

[0009] The basic weight of the fiber web is, in one embodiment, 1 g / m². 2 Including all increments, approximately 13g / m 2 From approximately 60g / m 2 It can be up to this. In one embodiment, the fiber web may have a relatively low basic weight. For example, the basic weight of the web may be about 55 g / m 2 For example, approximately 37g / m 2 The following, and generally about 13g / m 2 The above may also apply. 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 of the first surface and / or the second surface of the fiber web, preferably one of them. 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 45% or less when tested in accordance with ISO 2471:2008. For example, the opacity may be about 40% or less, for example about 38% or less, for example about 36% or less.

[0010] In one embodiment, the clearing agent included in the coating is a wax or oil of plant or animal origin. For example, in one embodiment, the clearing agent is a wax or oil of plant origin. In certain embodiments, the clearing agent may be a coconut-based wax, a palm-based wax, and / or a soy-based wax.

[0011] In one aspect, the fibrous web may include a wet laid web. The fibrous 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, plants of the genus Cinnamomum, linden, willow, plants of the genus Quercus, plants of the genus Wisteria, and mulberry. From an economic perspective, 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. In one aspect, at least about 90% by weight of the fibrous web comprises unrefined cellulose fibers. In addition to the wood pulp fibers and / or bast fibers, the fibrous web may contain leaf fibers such as manila hemp fibers, sisal fibers, or mixtures thereof. The fibrous web may also contain regenerated cellulose fibers. Such fibers include rayon fibers, viscose fibers, lyocell fibers, and the like. Bast fibers that can be incorporated into the fibrous web include hemp fibers, flax fibers, or mixtures thereof.

[0012] Paper products can be produced without containing any paraffin, mineral oil, or hydrocarbon oil. Thus, in one aspect, the paper products may be repulpable and compostable.

[0013] The basis weight of the paper product generally ranges from about 13 g / m 2 including all increments therebetween, to about 60 g / m 2 In various embodiments, the basis weight of the paper product is about 55 g / m 2 or less, for example about 50 g / m 2 or less, for example about 40 g / m 2 or less, and about 13 g / m 2 or more. 2 ​The above amounts are also acceptable. Paper products may generally contain cellulose fibers in an amount of about 50% by weight or more, for example, about 60% by weight or more, for example, about 65% by weight or more, for example, about 70% by weight or more, for example, about 75% by weight or more, for example, about 80% by weight or more. Cellulose fibers are generally present in paper products in an amount of about 95% by weight or less, for example, about 90% by weight or less, for example, about 85% by weight or less, for example, about 80% by weight or less.

[0014] The transparency agent is generally present in paper products at approximately 3 g / m². 2 For example, the amount mentioned above is approximately 5g / m 2 For example, the above amount is approximately 8g / m 2 For example, the above amount is approximately 10g / m 2 The above amount may be present. The transparency agent should be present in the paper product at approximately 30 g / m². 2 For example, the amount is approximately 20g / m². 2 For example, the following amounts are used: approximately 15g / m 2 It may be present in the following quantities.

[0015] As described above, the paper products of this disclosure can be formed with relatively high permeability. Permeability, as used herein, refers to air permeability, where 1 cm² is the pressure difference per kPa. 2 Air volume flow rate (cm³) passing through the substrate sample 3 minutes -1 )(In short: cm 3 / min / cm 2 It is measured as follows: For example, paper products are approximately 350 cm². 3 / min / cm 2 To give an example, approximately 500cm 3 / min / cm 2 To give an example, approximately 1,000 cm 3 / min / cm 2 To give an example, approximately 2,000 cm 3 / min / cm 2 To give an example, approximately 3,000 cm 3 / min / cm 2 To give an example, approximately 4,000 cm. 3 / min / cm2 The above permeability can be demonstrated. Porosity or permeability is generally about 30,000 cm³. 3 / min / cm 2 The following applies: Air permeability is measured according to ISO 2965:2009.

[0016] While possessing high porosity or permeability, paper products also exhibit barrier properties. For example, paper products can demonstrate droplet resistance for 10 minutes or more (using 2 μL of water droplets) according to TAPPI T 432 cm-09.

[0017] 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.

[0018] 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 fiber web may contain unrefined cellulose fibers. The transparency agent may contain bio-based waxes or oils such as coconut-based wax, palm-based wax and / or soy-based wax. In one embodiment, the fiber web is impregnated with the aqueous composition containing the transparency agent using a sizing press. However, in other embodiments, the transparency agent may be applied to the fiber web by using an applicator roll, by a sizing press, by a film press, by spraying, or by using any preferred coating technique.

[0019] In one embodiment, the fiber web may be a wet-laid web. A method for producing the product may include the steps of: combining unpurified cellulose fibers with water to form an aqueous suspension of fibers; depositing the aqueous suspension of fibers onto a porous-forming surface to form a fiber web; and coating the fiber web with an aqueous composition containing a clearing agent. In one embodiment, the porous-forming surface may be an inclined surface.

[0020] Other features and aspects of this disclosure will be discussed in more detail below.

[0021] 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]

[0022] [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]

[0023] 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.

[0024] definition As understood herein, “coating” on the surface of a fiber web can 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.

[0025] 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.

[0026] 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 components as understood herein can be obtained from biomass. The clarifier may be a bio-based wax or oil.

[0027] 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.

[0028] The biomass for use in the present invention may include polymer compounds, examples of which are lignin, as well as polysaccharides, such as starch, cellulose, hemicellulose (commonly also called polyose), glycogen, and alginates.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] As used herein, the term “fiber web” refers to a sheet made from pulp by a wet-laid process without coating.

[0035] As used herein, the term "unrefined cellulose fibers" refers to fibrous pulp used in papermaking without any refining process.

[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] As used herein, the term “regenerated cellulose fiber” refers to a fiber produced by the conversion of natural cellulose into a soluble cellulose derivative and subsequent regeneration. Examples include rayon fiber, viscose fiber, lyocell fiber, and the like.

[0038] 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.

[0039] 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 may 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. The low-opacity paper may be constructed to meet all requirements for food contact and food handling.

[0040] In one embodiment, the low opacity paper of the present disclosure is formed from a fibrous web containing unrefined cellulose fibers. By using unrefined cellulose fibers, less energy is required to produce the web, and therefore, it offers further environmental benefits, particularly compared to existing solutions. By using unrefined fibers, it is also possible to control the air permeability of the product. In one embodiment, for example, a highly porous but low opacity paper product can be produced, which can offer various benefits. For example, a product with higher air permeability is particularly well suited to applications where air permeability is important, such as when packaging bread, fruits, or vegetables. According to a preferred embodiment of the present invention, the cellulose fibers contained in the fibrous web of the paper product are unrefined cellulose fibers.

[0041] Overall, the low-opacity paper products of this disclosure may have relatively high transparency (opacity of 45% or less) and can be manufactured without refining cellulose fibers and without using a supercalender. In addition, they still have excellent water resistance while having relatively high air permeability (350 cm²). 3 / min / cm 2 Products possessing the above characteristics can be formed. In addition, paper products exhibit excellent mechanical properties necessary for conversion and handling.

[0042] All of the above benefits can be obtained while still producing paper products with an opacity of approximately 45% or less when tested in accordance with ISO 2471:2008. For example, the opacity of the paper product may be approximately 40% or less, for example, approximately 38% or less, for example, approximately 36% or less, for example, approximately 32% or less, for example, approximately 28% or less, for example, approximately 25% or less. The actual opacity may be determined by various factors and is generally 1% or more, for example, approximately 5% or more. The above opacity levels allow printed materials to be viewed through the paper product. For example, barcodes, QR codes (registered trademarks), and other machine-readable codes can be scanned through the paper products of this disclosure.

[0043] 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 comprises a paper substrate sheet 12 which is a fibrous web containing cellulose fibers, the cellulose fibers containing or being unrefined 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 suitable 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.

[0044] 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.

[0045] As described above, in one embodiment, the fiber web 12 may be a wet-laid paper web containing unrefined 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, regenerated cellulose fibers, or other plant fibers. When forming the fiber web, the aqueous suspension of fibers can be deposited on a porous-forming surface that drains water, thereby forming the fiber web. In one embodiment, the porous-forming surface may be sloped, in particular when the finished fiber pulp contains a significant amount of unrefined fibers.

[0046] 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, 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.

[0047] 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.

[0048] In one embodiment, the fiber web may contain regenerated cellulose fibers. Such fibers may include rayon fibers, lyocell fibers, viscose fibers, and mixtures thereof. If present, the regenerated cellulose fibers may be present in the fiber web in amounts ranging from about 3% to about 50% by weight, for example, from about 5% to about 15% by weight.

[0049] 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, linseed 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 fibers. In another embodiment, the finished fiber pulp may contain softwood fibers and / or hardwood fibers combined with leaf fibers such as Manila hemp fiber, sisal fiber, or mixtures thereof. Alternatively, the entire fiber web may be made from the leaf fibers described above. Cellulose fibers may be selected, for example, to produce a web that can efficiently drain from aqueous fluids during formation and produce relatively low-opacity paper while still retaining the mechanical properties required for processing and handling.

[0050] As described above, non-fibrous webs contain unrefined fibers. Unrefined fibers can be defined by the filtration efficiency value, measured by the Schoper-Riegra method (ISO 5267-1:2000) for drainage, expressed in units of "°SR". As a rule of thumb, the lower the °SR value, the less refined the fibers are. As used herein, unrefined cellulose fibers include fibers that may have been subjected to some mechanical action or refining, but still have a filtration efficiency value of approximately 25°SR or less, e.g., approximately 22°SR or less, e.g., approximately 20°SR or less, e.g., approximately 18°SR or less, e.g., approximately 15°SR or less, e.g., approximately 13°SR or less. The filtration efficiency value of the fibers may be 5°SR or more, e.g., 8°SR or more.

[0051] The fiber web may contain unrefined cellulose fibers in an amount of about 50% by weight or more, for example, about 60% by weight or more, for example, about 70% by weight or more, for example, about 80% by weight or more, for example, about 90% by weight or more, for example, about 95% by weight or more. In one embodiment, the fiber web is made entirely from unrefined cellulose fibers such as softwood fibers, bast fibers, leaf fibers, or mixtures thereof.

[0052] Using unrefined cellulose fibers not only reduces the energy requirements for producing the paper products of this disclosure, but also provides various advantages. For example, by controlling the amount of unrefined fibers in the fiber web, it is possible to control the air permeability of the resulting paper product. For example, the paper product of this disclosure has an air permeability of approximately 500 cm². 3 / min / cm 2 To give an example, approximately 750cm 3 / min / cm 2 To give an example, approximately 1,000 cm 3 / min / cm 2 To give an example, it is approximately 1,250 cm. 3 / min / cm 2 To give an example, approximately 1,500 cm 3 / min / cm 2 To give an example, it is approximately 1,750 cm. 3 / min / cm 2 To give an example, approximately 2,000 cm 3 / min / cm 2 To give an example, it is approximately 2,250 cm. 3 / min / cm 2 To give an example, approximately 2,500 cm 3 / min / cm 2 To give an example, it is approximately 2,750 cm. 3 / min / cm 2 To give an example, approximately 3,000 cm 3 / min / cm 2 For example, approximately 3,225 cm 3 / min / cm 2 To give an example, approximately 3,500 cm. 3 / min / cm 2 To give an example, it is approximately 3,750 cm. 3 / min / cm 2 To give an example, approximately 4,000 cm. 3 / min / cm 2 While still possessing the above air permeability, it may also have low opacity characteristics. The air permeability of paper products is generally about 30,000 cm³. 3 / min / cm 2 For example, approximately 20,000 cm 3 / min / cm 2 For example, approximately 10,000 cm 3 / min / cm 2 For example, approximately 7,000 cm 3 / min / cm 2 The following applies to products with a higher base weight: the air permeability is approximately 3,000 cm². 3 / min / cm 2 For example, approximately 2,000 cm 3 / min / cm 2 For example, approximately 1,000 cm 3 / min / cm 2 The following is also acceptable.

[0053] The low-opacity paper product may have the above-mentioned air permeability characteristics while still having excellent barrier properties. For example, the paper product can exhibit drip-proof properties for more than 10 minutes.

[0054] The basis weight of the fiber web used to form the paper product according to the present disclosure can vary depending on the specific application and the desired results. Generally, the basis weight of the fiber web is between about 13 g / m 2 including all increments therebetween, up to about 60 g / m 2 and can range from about 13 g / m 2 to about 60 g / m 2 In one embodiment, the fiber web has a relatively high basis weight of about 30 g / m 2 or more, such as about 34 g / m 2 or more, and about 55 g / m 2 or less, such as about 53 g / m 2 or less. In one embodiment, the basis weight of the fiber web can range from about 40 g / m 2 to about 60 g / m 2 In another embodiment, the basis weight of the fiber web can range from about 30 g / m 2 to about 40 g / m

[0055] In an alternative embodiment, the basis weight of the fiber web can be relatively low. For example, the basis weight can be about 35 g / m 2 or less, such as about 30 g / m 2 or less, such as about 28 g / m 2 or less, such as about 26 g / m 2 or less, such as about 24 g / m 2 or less. The basis weight of the fiber web is generally about 13 g / m 2 or more, such as about 15 g / m 2 or more, such as about 18 g / m 2 or more.

[0056] According to the present disclosure, the coating is applied to the fiber web.

[0057] In accordance with this disclosure, the coating includes a transparency agent applied to a fiber web. The transparency agent 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 transparency agent 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 transparency agent 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 transparency agent 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] Alternatively, the clearing agent may be a soy-based wax that can be applied to a fiber web as a cationic aqueous emulsion having a melting point of approximately 55 to 80 degrees Celsius, for example, approximately 63 to 72 degrees Celsius.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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. For example, the transparency agent may be added to the fiber web at approximately 3 g / m². 2 For example, the above amount is approximately 4g / m 2For 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 is applicable. Apply the clearing agent to the fiber web at approximately 30 g / m². 2 For example, the amount is approximately 20g / m². 2 For example, the following amounts are used: approximately 15g / m 2 For example, the following amounts are used: approximately 10g / m 2 It can be applied in the following quantities:

[0067] The amount of transparency agent incorporated into low opacity paper can also be described based on the weight of the product, using weight percentage as the basis. Generally, transparency agents such as bio-based waxes may be present in coated paper in amounts ranging from about 5% 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 7% by weight or more, for example, about 10% by weight or more, for example, about 13% 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, for example, about 20% by weight or less, for example, about 18% by weight or less, for example, about 15% by weight or less.

[0068] 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.

[0069] 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 air permeability of low-opacity paper and increase the barrier properties of the paper.

[0070] Low opacity paper produced in accordance with this disclosure not only exhibits low opacity but also offers beneficial admixtures of other properties. For example, the paper products of this disclosure can exhibit tensile strengths of approximately 2,000 cN / 30 mm or more, e.g., approximately 2,500 cN / 30 mm or more, e.g., approximately 3,000 cN / 30 mm or more, e.g., approximately 3,500 cN / 30 mm or more, and approximately 10,000 cN / 30 mm or less in at least one direction. Elongation in at least one direction may be approximately 1.2% or more, e.g., approximately 1.4% or more, and approximately 3% or less, e.g., approximately 2.5% or less, e.g., approximately 2% or less. Tensile strength and elongation are measured in accordance with ISO 1924-2:2008. Measurements are taken at a speed of 10 mm / min on a paper band with a width of 30 mm.

[0071] Low opacity paper may also have water-resistant properties for 10 minutes or more, according to TAPPI T 432cm-09.

[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 fruits, vegetables, bread, flowers, plants, etc. Low-opacity paper can be manufactured to be flexible or semi-rigid, for example, to make products well-suited for packaging.

[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, an air knife, or bar coating.

[0076] According to a preferred embodiment, the paper product (10) comprises a fiber web containing unrefined cellulose fibers, wherein the fiber web is 20 to 25 g / m² 2 A paper substrate sheet (12) having a basic weight up to 40 g / m², comprising a paper substrate sheet in which unrefined cellulose is a softening fiber, and a coating (14) containing a transparency agent which is coconut-based wax, palm-based wax, or soy-based wax, wherein the paper product exhibits an opacity of 30% or less, preferably 25% or less, when tested according to ISO 2471:2008, and weighs 40 g / m². 2 The following are the basic weights and 3000cm 3 / min / cm 2 Above and 6000cm 3 / min / cm 2 It has the following air permeability.

[0077] According to another preferred embodiment, the paper product (10) comprises a fiber web containing unrefined cellulose fibers, wherein the fiber web is 30 to 55 g / m² 2 Preferably 35 to 50 g / m² 2 A paper substrate sheet (12) having a basic weight up to a certain amount, wherein the paper substrate sheet is made of unrefined cellulose as softening fiber, and comprises a coating (14) containing a coconut-based wax as a transparency agent, wherein the paper product exhibits an opacity of 40% or less when tested according to ISO 2471:2008, and the paper product has a weight of 72 g / m². 2 The following are the basic weights, and 500cm 3 / min / cm2 Above and 2000cm 3 / min / cm 2 It has the following air permeability.

[0078] This disclosure may be better understood by referring to the following examples. [Examples]

[0079] Low-opacity paper was prepared in accordance with this disclosure and tested for various properties. For comparison, an uncoated substrate sheet (fiber web) was also tested.

[0080] In the first set of the example, 22 g / m² 2 A fiber web with a basic weight was constructed. The fiber web was formed from 100% unrefined soft fiber using a diagonal screen paper machine. Various transparent agents were applied to the fiber web using bar coating as follows: Sample No. 1 and Sample No. 2: The clearing agent was a coconut-based wax with a melting point between 30°C and 40°C. Sample No. 3: The transparent agent was a palm-based wax with a melting point of approximately 60°C, and Sample No. 4: The clearing agent was a soybean-based wax with a melting point of approximately 68°C.

[0081] Coconut-based wax and palm-based wax were both applied to fiber webs as anionic aqueous dispersions. However, soybean-based wax was applied to the fiber webs as a cationic emulsion. The samples were tested for opacity, mechanical properties, permeability, and water-repellency. The following results were obtained.

[0082] [Table 1]

[0083] As shown above, the opacity of the samples prepared according to this disclosure decreased by only about 20%, for example, by only about 30%, and for example, by only about 35%, compared to the original paper. While the water-repellent properties increased dramatically, the product still retained high air permeability characteristics.

[0084] Further low-opacity papers were prepared in accordance with this disclosure. In sample number 5, bar coating was used, and coconut-based wax was applied at 36 g / m². 2 It was applied to a fiber web with a base weight of [value missing]. In sample number 6, bar coating was used, and coconut-based wax was applied at 50 g / m². 2 The experiment was applied to a base paper having a specific basic weight. A fiber web was formed from 100% unrefined soft fiber using a diagonal screen paper machine. The following results were obtained.

[0085] [Table 2]

[0086] 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 more specifically described in the appended claims. [Explanation of Symbols]

[0087] 10 Low opacity paper and paper products 12 Paper substrate sheets, fiber webs 14 Coating

Claims

1. 13 g / m ２ From 60g / m ２ A fiber web having a basic weight up to and defining a first surface and a second surface, comprising cellulose fibers, wherein the cellulose fibers include unrefined cellulose fibers, 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, When tested according to ISO 2471:2008, it exhibited an opacity of 45% or less at 350 cm². ３ / min / cm ２ It also has the above degree of air permeability, paper products.

2. The paper product according to claim 1, wherein the unrefined cellulose fibers have a Shopper-Riegra filtration rate of 5°SR or higher and 25°SR or lower, preferably 7°SR or higher and 20°SR or lower.

3. The paper product according to claim 1, wherein the fiber web contains 90% by weight or more of unrefined cellulose fibers.

4. The paper product according to claim 1, wherein the unrefined cellulose fibers include wood fibers, preferably softwood fibers, hardwood fibers, or a mixture thereof.

5. The paper product according to claim 1, wherein the unrefined cellulose fibers comprise leaf fibers, preferably Manila hemp fibers, sisal fibers, or a mixture thereof.

6. The paper product according to claim 1, wherein the fiber web contains regenerated cellulose fibers.

7. The paper product according to claim 1, wherein the fiber web comprises bast fibers, preferably hemp fibers, flax fibers, or a mixture thereof.

8. 500 cm ３ / min / cm ２ or more, preferably 1000 cm ３ / min / cm ２ or more, more preferably 2000 cm ３ / min / cm ２ or more, even more preferably 3000 cm ３ / min / cm ２ or more, most preferably 4000 cm ３ / min / cm ２ or more, and 30,000 cm ３ / min / cm ２ The paper product according to claim 1, having an air permeability as described above.

9. The paper product according to claim 1, which exhibits water-resistant properties for 10 minutes or more in accordance with TAPPI T 432cm-09.

10. The fiber web is 55 g / m ２ Preferably 40 g / m ２ More preferably, 30 g / m ２ Further, and more preferably, 25 g / m ２ The paper product according to claim 1, having the following basic weight.

11. 75 g / m ２ Preferably 60 g / m ２ More preferably, 40 g / m ２ The following, and 18 g / m ２ The paper product according to claim 1, having the above basic weight.

12. The paper product according to claim 1, which is not supercalendered.

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

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

15. 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.

16. The paper product according to claim 1, wherein the transparent agent comprises a wax having a melting point from 25°C to 75°C, preferably from 30°C to 45°C.

17. The paper product according to claim 1, having an opacity of 40% or less, preferably 38% or less, more preferably 36% or less, and most preferably 32% or less, when tested in accordance with ISO 2471:2008.

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

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

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

21. The transparent agent is present in the paper product at a concentration of 3 g / m². ２ The above amount is preferably 5 g / m². ２ More preferably, 8 g / m² ２ More preferably, the amount is 10 g / m². ２ In the above quantities, and 30 g / m² ２ Preferably 25 g / m² in the following amounts. ２ The following amounts, more preferably 15 g / m² ２ The paper product according to claim 1, which exists in the following quantities.

22. A method for producing a paper product according to any one of claims 1 to 21, A process for preparing an aqueous suspension of cellulose fibers, A step of depositing an aqueous suspension of fibers onto a porous surface to form a fiber web, A step of coating at least one surface, preferably one surface, of a fiber web with an aqueous composition containing a transparent agent. Methods that include...

23. Use of the paper product according to any one of claims 1 to 21 as packaging material for fruits, vegetables, bread, flowers and / or plants.

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