EP4563744A1 - Base paper for translucent paper, translucent paper, and method for manufacturing translucent paper - Google Patents

Base paper for translucent paper, translucent paper, and method for manufacturing translucent paper Download PDF

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Publication number
EP4563744A1
EP4563744A1 EP23846626.2A EP23846626A EP4563744A1 EP 4563744 A1 EP4563744 A1 EP 4563744A1 EP 23846626 A EP23846626 A EP 23846626A EP 4563744 A1 EP4563744 A1 EP 4563744A1
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EP
European Patent Office
Prior art keywords
translucent
paper
region
base paper
range
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23846626.2A
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German (de)
English (en)
French (fr)
Inventor
Yoshiyuki Asayama
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Oji Holdings Corp
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Oji Holdings Corp
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Publication of EP4563744A1 publication Critical patent/EP4563744A1/en
Pending legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/10—Packing paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/12—Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/33—Synthetic macromolecular compounds
    • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/26—Agents rendering paper transparent or translucent
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/06—Vegetable or imitation parchment; Glassine paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/30—Multi-ply
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/30—Multi-ply
    • D21H27/38—Multi-ply at least one of the sheets having a fibrous composition differing from that of other sheets

Definitions

  • the present invention relates to base paper for translucent paper, translucent paper, and a method for manufacturing translucent paper. More specifically, the present invention relates to translucent paper that can be used for packaging paper, printing paper, publishing paper, information paper, and the like, and has a partial or entire region made translucent, base paper used in the translucent paper, and a method for manufacturing translucent paper.
  • Paper packages such as envelopes and product packages may have a window through which an addressee and contents can be seen from the outside.
  • a transparent resin film or glassine paper may be attached to the window. From the viewpoint of recycling resources, it is preferable to use glassine paper.
  • Glassine paper is translucent paper obtained by finely beating pulp to produce paper and subjecting the produced paper to a high-pressure calendaring process, and is known in the art. Glassine paper is not strong enough to be used as a package such as an envelope, so its applications are limited, such as being attached only to the window of an envelope.
  • a method for producing translucent paper to replace glassine paper a method of impregnating spaces between the fibers of paper with a resin which makes a translucent region has been proposed (for example, Patent Documents 1 to 4). By impregnating the spaces between the cellulose fibers of paper with a resin which makes a translucent region, the transparency of the translucent region impregnated with the resin which makes a translucent region can be increased. Since translucent paper has superior strength to glassine paper, the translucent paper can also be used as a package such as an envelope.
  • the present invention provides base paper used in translucent paper which is obtained by impregnation with a resin which makes a translucent region, translucent paper using base paper, and a method for producing translucent paper.
  • the present invention has the following configurations.
  • the base paper for translucent paper of the present invention becomes translucent paper in which an impregnated region is translucent by impregnating it with a material which makes a translucent region.
  • the material which makes a translucent region may be impregnated in the entire region of the base paper for translucent paper when viewed in a plane, or in a partial region. There is no particular limit to the shape or number of regions. In the region impregnated with the material which makes a translucent region, the material which makes a translucent region penetrates in the thickness direction of the base paper for translucent paper, and the material which makes a translucent region fills as many gaps inside the paper as possible, making the paper translucent.
  • translucent refers to the opacity of the paper after processing being lower than the opacity of the paper before processing, and although there is no particular limit, “translucent” refers to a region after processing with an opacity of 4 to 25%.
  • the base paper for translucent paper is paper of which the main components region is softwood chemical pulp and hardwood chemical pulp.
  • softwood chemical pulp include unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), semi-bleached softwood kraft pulp (NSBKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), and semi-bleached softwood sulfite pulp (NSBSP).
  • Examples of the hardwood chemical pulp include unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), semi-bleached hardwood kraft pulp (LSBKP), unbleached hardwood sulfite pulp (LUSP), bleached hardwood sulfite pulp (LBSP), and semi-bleached hardwood sulfite pulp (LSBSP).
  • LKP unbleached hardwood kraft pulp
  • LLKP bleached hardwood kraft pulp
  • LSBKP semi-bleached hardwood kraft pulp
  • LUSP unbleached hardwood sulfite pulp
  • LBSP bleached hardwood sulfite pulp
  • LSBSP semi-bleached hardwood sulfite pulp
  • NNKP bleached softwood kraft pulp
  • LLKP bleached hardwood kraft pulp
  • the blending ratio of the softwood chemical pulp to the hardwood chemical pulp is 80:20 to 51:49.
  • a preferable blending ratio is 75:25 to 55:45, and a more preferable blending ratio is 70:30 to 60:40.
  • the softwood chemical pulp Since the softwood chemical pulp has a longer and thicker fiber structure than the hardwood chemical pulp, blending a large amount of the softwood chemical pulp results in base paper with a high porosity, which can efficiently impregnate the material which makes a translucent region.
  • the hardwood chemical pulp has a thin and short fiber structure, which improves the texture of the paper. Therefore, by using the blending ratio above, the porosity of the base paper and the texture of the translucent paper can be compatible.
  • the hardwood chemical pulp since the hardwood chemical pulp has a thin and short fiber structure, it is easily covered by the resin contained in the material which makes a translucent region, so it is preferable to adjust the blending amount of the hardwood chemical pulp in consideration of the ease of defibration when recycling it as waste paper.
  • the Canadian Standard Freeness of the softwood chemical pulp is preferably 400 to 700 mlCSF.
  • the Canadian Standard Freeness is more preferably 420 to 650 mlCSF, and even more preferably 450 to 600 mlCSF.
  • the Canadian Standard Freeness of the softwood chemical pulp is equal to or greater than the lower limit of the range above, the gaps in the base paper for translucent paper can be maintained, and the impregnation of the material which makes a translucent region is excellent.
  • the Canadian Standard Freeness of the softwood chemical pulp is equal to or less than the upper limit of the range above, the texture of the base paper for translucent paper can be improved, and translucent paper having a translucent region with excellent transparency and visibility can be easily obtained.
  • the Canadian Standard Freeness of the hardwood chemical pulp is preferably 350 to 650 ml CSF.
  • the Canadian Standard Freeness is more preferably 370 to 630 ml CSF, and even more preferably 400 to 600 ml CSF.
  • the strength of the base paper for translucent paper can be increased.
  • the Canadian Standard Freeness of the hardwood chemical pulp is equal to or less than the upper limit of the range above, the texture of the base paper for translucent paper can be improved, and it is easy to obtain translucent paper having a translucent region with excellent transparency and visibility.
  • the Canadian Standard Freeness of the softwood chemical pulp be higher than that of the hardwood chemical pulp, since the strength and transparency of the paper are excellent.
  • the Canadian Standard Freeness of pulp is measured according to JIS P8121-2:2012.
  • glassine paper which is generally known as translucent paper
  • a chemical pulp with a high degree of beating for example, a chemical pulp with a Canadian Standard Freeness of 250 ml CSF or less, is used.
  • the pulp fibers with a high degree of beating are ground and cut, they are difficult to apply to applications such as packaging bags that require strength, even if they are used for transparent windows of envelopes, for example.
  • Pulps other than the softwood chemical pulp and the hardwood chemical pulp can be used in combination as long as the effects of the present invention are not impaired.
  • Examples of the pulp include mechanical pulp, thermomechanical pulp, deinked pulp, nonwood pulp, and synthetic pulp.
  • the basis weight of the base paper for translucent paper is 40 to 100 g/m 2 .
  • the basis weight is preferably 40 to 80 g/m 2 , more preferably 40 to 75 g/m 2 , more preferably 43 to 70 g/m 2 , and even more preferably 45 to 65 g/m 2 .
  • the base paper for translucent paper When the basis weight of the base paper for translucent paper is equal to or greater than the lower limit of the range above, the base paper has sufficient strength, making the translucent paper suitable for applications such as packaging paper and printing paper. When the basis weight of the base paper for translucent paper is equal to or lower than the upper limit of the range above, the transparency of the translucent paper can be increased. Basis weight is measured in accordance with JIS P8 124.
  • the air permeability of the base paper for translucent paper is 10 to 40 seconds.
  • the air permeability is preferably 12 to 35 seconds, and more preferably 15 to 33 seconds.
  • the base paper has sufficient strength, and the translucent paper is suitable for applications such as packaging paper and printing paper.
  • the air permeability of the base paper is equal to or lower than the upper limit of the range above, the permeability of the material which makes a translucent region is excellent, and the transparency of the translucent paper can be increased.
  • the air permeability is measured according to the Oken air permeability method in accordance with J. TAPPI-5-2:2000.
  • the density of the base paper for translucent paper is preferably 0.5 to 0.85 g/cm 3 , and more preferably 0.6 to 0.8 g/cm 3 .
  • the density of the base paper is equal to or greater than the lower limit of the range above, the base paper has sufficient strength, and the translucent paper is suitable for applications such as packaging paper and printing paper.
  • the density of the base paper is equal to or less than the upper limit of the range above, the permeability of the material which makes a translucent region is excellent, and the transparency of the translucent paper can be increased.
  • the density is measured according to JIS P8118.
  • the porosity of the base paper for translucent paper is preferably 30 to 80%, more preferably 40 to 70%, and even more preferably 50 to 70%.
  • the porosity of the base paper for translucent paper is equal to or greater than the lower limit of the range above, the transparency of the translucent region is easily increased.
  • the porosity of the base paper for translucent paper is equal to or less than the upper limit of the range above, the physical strength of the translucent paper is less likely to decrease.
  • the porosity of the paper substrate is calculated by dividing the density measured according to JIS P8118 by the true density of cellulose, which is 1.50.
  • the Parker Print Surf smoothness of at least one surface of the base paper for translucent paper is preferably 7 ⁇ m or less, and more preferably 5 ⁇ m or less. There is no particular limit to the lower limit. The smaller the value, the smoother the paper. The Parker Print Surf smoothness can evaluate the smoothness of fine details, and the smaller this value, the more the light scattering on the paper surface can be reduced, so that the visibility through the translucent region can be improved.
  • the Parker Print Surf smoothness is the Parker Print Surf smoothness (soft backing/clamp pressure 500 kPa) obtained in accordance with ISO 8791-4:1992.
  • the base paper for translucent paper can be appropriately blended with known papermaking auxiliaries such as paper strengthening agents, sizing agents, fillers, colorants, and the like. Since the blending of fillers works to increase the concealing properties of the paper, it is preferable to limit the blending to a range that does not impair transparency and visibility, and it is more preferable that the base paper for translucent paper not contain fillers.
  • the method for producing the base paper for translucent paper is not particularly limited.
  • the method may include a step of beating pulp, which is a raw material for the base paper for translucent paper, a step of papermaking using a pulp slurry containing the beaten pulp, and a step of drying the wet sheet obtained by papermaking.
  • the beating step it is preferable to beat the raw pulp so that the pulp has the Canadian Standard Freeness above.
  • the beating machine include known beating machines such as a double disc refiner.
  • papermaking machine used for papermaking.
  • Examples of the papermaking machine include a Fourdrinier papermaking machine, a Short Drain papermaking machine, and a Cylinder papermaking machine.
  • drying step There are no particular limitations on the drying step.
  • a dryer attached to the papermaking machine can be used.
  • the base paper for translucent paper may be subjected to a smoothing treatment.
  • the smoothing treatment include a tight press, a machine calendar, a gloss calendar, a soft nip calendar, and a super calendar.
  • these devices increase the density of the base paper, it is necessary to be careful not to increase the density too much by lowering the linear pressure.
  • the transfer method in which the base paper is attached to a smooth surface while it is still wet and then dried to transfer the smooth surface is preferable because the density of the base paper does not increase.
  • techniques such as a Yankee cylinder, a cast drum, and a film transfer can be used.
  • a Yankee dryer using a Yankee cylinder is preferable because it is attached to a papermaking machine and has excellent productivity.
  • the translucent paper of the present invention is paper in which the base paper for translucent paper is impregnated with a material which makes a translucent region, making the impregnated region translucent.
  • the translucent paper 1A shown in FIG. 1 and FIG. 2 has base paper 2 for translucent paper and a translucent region 4 in which the material which makes a translucent region 3 is impregnated in the base paper for translucent paper 2.
  • the translucent paper 1B shown in FIG. 1 and FIG. 3 has the base paper 2 for translucent paper, the translucent region 4 in which the material which makes a translucent region 3 is impregnated in the base paper 2 for translucent paper, and a coating layer 5 that covers the translucent region 4.
  • the translucent region 4 is formed in a partial region of the base paper 2 for translucent paper when viewed in plan view. For example, when the translucent paper 1A is used as a package, the contents can be seen from the outside of the package through the translucent region 4, or through the translucent region 4 and the coating layer 5.
  • the material which makes a translucent region is not particularly limited as long as it is a material that makes the impregnated portion translucent by impregnating the base paper for translucent paper.
  • the material which makes a translucent region may be, for example, resins such as acrylic resin, polyethylene resin, polyester resin, urethane resin, nitrocellulose, shellac, rosin, and the like; vegetable oils such as paulownia oil, linseed oil, castor oil, hydrophilic castor oil, coconut oil, soybean oil, and commercially available salad oil; and waxes such as carnauba wax, palm wax, beeswax, spermaceti, and Japan wax.
  • the material which makes a translucent region may be used alone or in combination of two or more.
  • a resin that is stable over time is preferable, and an acrylic resin is more preferable.
  • acrylic resins a UV-curable acrylic resin is particularly preferable because it has excellent surface coverage and the interface of the impregnated region of the material which makes a translucent region in a cross-sectional view is clear.
  • UV-curable acrylic resins include those disclosed in paragraphs 0025 and 0026 of Japanese Patent Application, First Publication No. 2021-91481 .
  • a material which makes a translucent region from the examples above, which have a refractive index in the range of 1.4 to 1.6, preferably 1.45 to 1.58, more preferably 1.50 to 1.58, and even more preferably 1.52 to 1.58.
  • the refractive index of cellulose fibers is generally said to be in the range of 1.4 to 1.6. If the refractive index of the material which makes a translucent region is within the range above, the difference with the refractive index of cellulose fibers is small, making it easy to increase the transparency and visibility of the translucent region.
  • the refractive index of the material which makes a translucent region is measured in accordance with JIS K 7142.
  • base paper for translucent paper By impregnating base paper for translucent paper with a material which makes a translucent region, which has a refractive index close to that of cellulose fibers, and filling the gaps between the cellulose fibers inside the paper, the refraction of light caused by the material which makes a translucent region in the base paper for translucent paper can be reduced. This makes it easier to obtain a translucent region with excellent transparency and visibility.
  • a high refractive index material such as zirconium or titanium may be used as necessary.
  • the material which makes a translucent region is impregnated in the base paper for translucent paper
  • the material which makes a translucent region is preferably liquid at room temperature or in a heated state.
  • the material which makes a translucent region be soluble in a liquid medium such as an organic solvent at room temperature or in a heated state.
  • the material which makes a translucent region be one which can be impregnated into the base paper for translucent paper as an impregnable liquid agent which makes a translucent region during manufacturing of the translucent paper.
  • a coating layer may be provided on at least a part of the surface of the translucent region.
  • This coating layer can increase the smoothness of the surface of the translucent region, prevent diffuse reflection of light on the surface of the translucent region, and improve the visibility of the translucent region.
  • the material of the coating layer include a material which makes a translucent region and OP varnish.
  • the material which makes a translucent region include the same as those exemplified in the section on the translucent region.
  • the coating layer includes a material which makes a translucent region, the material which makes a translucent region in the coating layer and the material which makes a translucent region in the translucent region may be the same or different.
  • the material of the coating layer may be used alone or in combination of two or more.
  • OP varnish is sometimes called overprint varnish.
  • the components of OP varnish vary depending on the product, manufacturer, and the like, but OP varnish containing at least one selected from the group consisting of linseed oil, tung oil, and nitrocellulose is preferable.
  • Commercially available OP varnishes include products from Toyo Ink Co., Ltd., T&K Toka Corporation, and Fuji Ink Mfg. Co., Ltd. OP varnish may be used alone, or two or more may be used in combination. Drying methods such as those based on oxidative polymerization or UV effects may be used.
  • the refractive index of the cellulose fibers is generally said to be in the range of 1.4 to 1.6.
  • the refractive index of the coating layer is measured according to JIS K 714 2.
  • the opacity of the translucent region is preferably 4 to 25%, more preferably 4 to 20%, and even more preferably 4 to 15%.
  • the opacity of the translucent region is measured according to JIS P 8138:1976. The smaller the opacity value, the more transparent the region.
  • the haze of the translucent region is preferably 80% or less. When the haze of the translucent region is 80% or less, the transparency of the translucent region is improved.
  • the lower limit of the haze of the translucent region is not particularly limited, but is, for example, 10% or more, and preferably 20% or more.
  • the haze of the translucent region is measured in accordance with JIS-K7136. The smaller the haze value, the less cloudy the region.
  • haze and opacity have been used to evaluate the visibility of translucent regions.
  • the numerical trends of haze and opacity often do not correspond to the superiority or inferiority of visibility by human eyes. For example, when the whiteness of a sample is high, the transmittance of visible light is high, but the visibility and visual appearance are not always satisfactory.
  • Haze is calculated as the ratio of diffuse transmittance to the total light transmittance of light transmitted through a sample.
  • the diffuse transmittance is the transmittance of diffuse light, which is obtained by excluding parallel components from the light rays that are transmitted through a sample when linear light is incident on the sample.
  • the human eye preferentially recognizes light that travels in a straight line or light with a narrow diffusion angle, rather than diffuse light or scattered light with a wide diffusion angle.
  • opacity is calculated by including diffuse light that is difficult for the human eye to recognize the measurement target, so it is not suitable for evaluating the human visual appearance or the visibility in the depth direction.
  • the inventors came up with the idea of evaluating the visibility of a translucent region based on the degree of blurring of the contents seen through the translucent region.
  • the degree of blurring is due to the diffusion pattern of light transmitted through the translucent region.
  • the transmitted light contains a relatively large amount of diffused light with a wide diffusion angle, which reduces the visibility of the contents.
  • the transmitted light contains a relatively large amount of light that travels in a straight line or light that has a narrow diffusion angle, which improves the visibility of the contents.
  • the inventors devised a method and index for quantitatively evaluating the degree of blurring, and found that if the index of the degree of blurring is equal to or greater than a specific value, the visibility of the contents seen through the translucent region is excellent.
  • the indexes are the luminous transmittance and the luminous transmittance ratio.
  • a luminous transmittance measuring device that has a light-projecting part that projects light from a light source onto a sample, a light-receiving part that receives the light that has passed through the sample, and a sensor that measures the received light, with a distance of 50 mm or more between the light-projecting part and the light-receiving part, and of which the light receiving sensitivity characteristics are nearly identical to that of photo vision-relative luminous efficiency when measured without a sample.
  • luminous transmittance measuring devices are commercially available for measuring eyeglass lenses, filter glass, transparent conductive film glass, and the like, and measurements can be made using a device that meets the above measurement conditions.
  • any device that meets the above measurement conditions such as a spectrophotometer, can be used as the luminous transmittance measuring device.
  • the luminous transmittance (T50) under the following measurement condition 1 be 20% or more.
  • a luminous transmittance measuring device with a gap of at least 50 mm between the light-projecting part and the light-receiving part is used, the translucent region of the paper is used as a sample, and the luminous transmittance (T50) of the translucent region of the translucent paper is measured by placing the sample such that one side of the sample is in contact with the light-projecting part.
  • FIG. 6 is an explanatory diagram explaining the measurement.
  • the luminous transmittance (T50) can be measured by placing one surface S1 of the sample S in contact with the light-projecting part 101 of the luminous transmittance measuring device 100.
  • TLV-304-LC a luminous transmittance measuring device sold by Asahi Spectroscopy Co., Ltd.
  • This device has a distance of 51.5 mm between the light-projecting part and the light-receiving part.
  • the luminous transmittance (T50) is preferably 23% or more.
  • the translucent region of the paper is measured as a sample, and the luminous transmittance (T50) is measured when one side of the sample is placed in contact with the light-projecting part, and the luminous transmittance (T0) is measured when the other side of the sample is placed in contact with the light-receiving part, and the luminous transmittance ratio is calculated using the following formula.
  • Luminous transmittance ratio T 50 / T 0 x 100
  • FIGS. 7(a) and (b) are explanatory diagrams explaining the measurement.
  • the luminous transmittance (T50) can be measured by placing one surface S1 of a sample S in contact with light-projecting part 101 of the luminous transmittance measuring device 100.
  • the luminous transmittance (T0) can be measured by placing the other surface S2 of the sample S in contact with light-receiving part 102.
  • TLV-304-LC a luminous transmittance measuring device sold by Asahi Spectroscopy Co., Ltd.
  • This device has a distance of 51.5 mm between the light-projecting part and the light-receiving part.
  • the luminous transmittance ratio (T50 / T0) x 100 is calculated from the luminous transmittance (T50) and luminous transmittance (T0) of two points at least 50 mm apart. If this value is 44 or more, the paper has a transparent region with excellent visibility. The larger the value, the better the visibility.
  • the luminous transmittance ratio is preferably 48 or more, and more preferably 50 or more.
  • the luminous transmittance ratio indicates the degree to which the luminous transmittance of light immediately after passing through the sample (T0) has decreased at a position 50 mm away (T50).
  • T50 corresponds to visibility because it excludes light that is scattered within 50 mm and does not reach the light-receiving part. Since light does not scatter in air, the cause of scattering is due to the state of the inside and surface of the sample.
  • the range of both the luminous transmittance (T50) and the luminous transmittance ratio be satisfied.
  • the luminous transmittance (T50) is 20% or more and the luminous transmittance ratio is 44 or more in the transparent region, it is advisable to control the refraction and scattering of light on the surface of the paper where the light is incident, inside the paper with light incident, and on the surface of the paper through which the light passes.
  • the density of the translucent region of the translucent paper is preferably 0.7 to 2.5 g/cm 3 , more preferably 0.7 to 2.0 g/cm 3 , and even more preferably 0.8 to 2.0 g/cm 3 .
  • the density of the translucent region is equal to or greater than the lower limit of the range above, it is believed that the air spaces between the cellulose fibers are sufficiently eliminated by impregnation with the resin component.
  • the density of the translucent region is equal to or less than the upper limit of the range above, the processability of the translucent paper when made into packaging materials and the like is improved.
  • the density of the translucent region is measured in accordance with JIS P 8118.
  • the translucent paper of the present invention can be recycled without separation.
  • paper recycling involves defibrating collected waste paper in a large disintegrator called a pulper when the paper/pulp concentration is about 1%, removing undispersed material in a coarse fiberizer with a diameter of about 9 mm, and then further dispersing and passing through a cleaner or a screen with a diameter of about 1.6 mm to remove fine undispersed material. If the resin is contained in excess, defibration-ability and dispersibility may deteriorate, clogging these screens, or undispersed material may generate dust during the papermaking process and contaminate the paper, causing problems with dust spots.
  • the base paper with a controlled pulp blend has an appropriate gap ratio, so that it is possible to simultaneously achieve improved transparency due to the material which makes a translucent region and suppress the decrease in recyclability due to the impregnation of the material which makes a translucent region.
  • the method of manufacturing translucent paper of the present invention is a method including: impregnating and coating at least a part of base paper for translucent paper with a material which makes a translucent region, wherein the base paper mainly contains a softwood chemical pulp and a hardwood chemical pulp, a ratio of the softwood chemical pulp to the hardwood chemical pulp is in a range from 80:20 to 51:49, a basis weight of the base paper is in a range from 40 to 100 g/m 2 , and an air permeability of the base paper is in a range from 10 to 40 seconds.
  • the base paper for translucent paper contains a lot of softwood chemical pulp and has a basis weight and air permeability within a specific range, which allows many gaps to be formed inside the paper and allows the gaps to be impregnated with a material which makes a translucent region, thereby increasing transparency. Impregnation of the material which makes a translucent region can be performed by impregnation-coating.
  • the material which makes a translucent region is impregnated by impregnation-coating the liquid material which makes a translucent region into the base paper for translucent paper.
  • the impregnation-coating may be performed on either side of the base paper for translucent paper.
  • the Parker Print Surf smoothness of one side of the base paper for translucent paper is 5 ⁇ m or less, it is preferable to impregnate the other side with a material which makes a translucent region, since it penetrates efficiently.
  • the Parker Print Surf smoothness of both sides is 5 ⁇ m or less, it is preferable to impregnate the side with the larger value.
  • the side with a smaller Parker Print Surf smoothness value has a higher smoothness, so the closer to the surface, the higher the density of the cellulose fibers.
  • the impregnation of the material which makes a translucent region is performed by impregnation-coating the side with a lower cellulose density.
  • a Parker Print Surf smoothness of 5 ⁇ m or less is preferable because it is smooth, light scattering on the paper surface can be suppressed, and visibility is excellent.
  • a liquid medium capable of dissolving the material which makes a translucent region is used to prepare the impregnation-coating solution.
  • the concentration of the material which makes a translucent region may be changed using a liquid medium, or the material which makes a translucent region may be used as it is as the impregnation-coating solution without using a liquid medium.
  • the liquid medium is not particularly limited. Either an aqueous solvent or an organic solvent can be used. If the liquid medium contains moisture, the base paper for translucent paper is likely to swell due to the moisture. In addition, the base paper for translucent paper is likely to shrink during subsequent drying. As a result, curling, bumps, and unevenness are likely to occur. Therefore, it is preferable that the liquid medium not contain moisture, and an organic solvent is more preferable.
  • the organic solvent may be a polar solvent or a non-polar solvent.
  • Examples of the polar solvents include alcohols, ethers, and esters.
  • alcohols examples include methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, and n-hexanol.
  • ethers examples include glycol ethers, such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, triethylene glycol monopropyl ether, tetraethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, tetraethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monoisopropyl ether,
  • esters examples include diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate.
  • non-polar solvents examples include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, and dodecane; isoparaffinic hydrocarbons such as isohexane, isooctane, and isododecane; alkylnaphthenic hydrocarbons such as liquid paraffin; aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, and solvent naphtha, and silicone oil.
  • paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, and dodecane
  • isoparaffinic hydrocarbons such as isohexane, isooctane, and isododecane
  • alkylnaphthenic hydrocarbons such as liquid paraffin
  • aromatic hydrocarbons such as
  • the impregnation-coating solution may further contain components other than the material which makes a translucent region and the liquid medium.
  • the other components include basic substances such as ammonia, ethylenediamine, and triethylamine; viscosity modifiers such as glycerin and ethylene glycol; high refractive index substances such as zirconium and titanium; antifoaming agents; release agents; and colorants.
  • the other components are not limited to these examples.
  • a section may be formed in the base paper for translucent paper where the material which makes a translucent region does not reach a part of the surface opposite the impregnated surface. This is because the surface condition of the relatively smooth surface in this section can be maintained in the state that the material which makes a translucent region was in before impregnation-coating.
  • the material which makes a translucent region may be impregnated from both sides of the base paper for translucent paper. This is to ensure that the material which makes a translucent region is sufficiently impregnated into the interior of the translucent paper and to reduce gaps where the material which makes a translucent region is not impregnated.
  • the coating amount of the impregnation-coating solution per unit area is preferably 10 to 70 g/m 2 , more preferably 20 to 60 g/m 2 , and even more preferably 30 to 60 g/m 2 .
  • the coating amount of the impregnation-coating solution per unit area is equal to or greater than the lower limit of the range above, the transparency of the translucent region is easily increased.
  • the coating amount of the impregnation-coating solution per unit area is equal to or less than the upper limit of the range above, the recyclability can be increased.
  • the viscosity of the impregnation-coating solution is preferably 50 to 5000 mPa ⁇ s, more preferably 50 to 4000 mPa ⁇ s, and even more preferably 50 to 3000 mPa ⁇ s.
  • the viscosity is equal to or less than the upper limit of the range above, the impregnation-coating solution penetrate into the base paper, and the transparency of the translucent region is easily increased.
  • the viscosity is equal to or greater than the lower limit of the range above, the boundary between the translucent region and the non-translucent region becomes clear.
  • the viscosity is measured using a Brookfield viscometer at 30°C and 60 rpm.
  • the method of coating the impregnation-coating solution is not particularly limited.
  • Examples of the method of coating the impregnation-coating solution include flexographic printing, inkjet printing, gravure printing, offset printing, gravure offset printing, silk screen printing, roll coating, bar coating, and blade coating.
  • the gaps between the cellulose fibers in the translucent paper can be filled with the material which makes a translucent region.
  • an impregnation-coating solution containing a material which makes a translucent region with a refractive index in the range of 1.4 to 1.6 is used, the gaps in the translucent paper can be filled with a material which makes a translucent region whose refractive index is close to that of cellulose. This makes it possible to reduce the refraction of light caused by the gaps in the translucent paper.
  • the impregnation-coating of the base paper for translucent paper with the impregnation-coating solution may be carried out in one step or in multiple steps.
  • the constituent components and composition of the material which makes a translucent region used in each step may be the same or different from each other.
  • various light sources can be used, such as a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, and an electrodeless discharge lamp.
  • the integrated light amount is not particularly limited. It may be appropriately changed depending on the amount of the material which makes a translucent region used and the type of resin which makes a translucent region.
  • the translucent region is formed in a portion of the translucent paper when viewed in plan view.
  • the translucent paper is used as a package, the contents and address can be seen through the translucent region from outside the package.
  • the translucent region may be the entire region of the translucent paper in the planar direction. There is no particular limitation on the number of translucent regions, and there may be one or more. In the case of translucent paper with multiple translucent regions, there are no particular limitations on the size or shape of each translucent region.
  • the translucent paper of the present invention offers unprecedented transparency and visibility, making it suitable for use in a variety of applications, including not only wrapping paper but also printing paper, book paper, copy paper, information paper, label paper, and the like, where images (letters, symbols, pictures, objects, and the like) on the opposite side of the paper can be seen through the paper base.
  • Base paper for translucent paper was manufactured using the chemical pulp blend and manufacturing device combination shown in Tables 1 and 2. The measured values of the basis weight, Oken air permeability (air permeability), and Parker Print Surf smoothness (smoothness) of the smooth surface of the obtained base paper for translucent paper are also listed.
  • Impregnation-coating solution 1 An acrylic paraffin solvent (product name: Clariten DC, manufactured by Yamato Chemical Industry Co., Ltd.) was prepared as the material which makes a translucent region.
  • the refractive index of the material which makes a translucent region was 1.50.
  • the refractive index was measured using an Appe type refractive index measuring device manufactured by Atago Co., Ltd.
  • An aromatic paraffin solvent (product name: Clariten S, manufactured by Yamato Chemical Industry Co., Ltd.) was prepared as the solvent.
  • the material which makes a translucent region and the solvent were mixed to prepare an impregnation-coating solution with a concentration of the material which makes a translucent region of 75% by mass.
  • the viscosity of the impregnation-coating solution at 30°C and 60 rpm was 1800 mPa ⁇ s.
  • Impregnation-coating solution 2 40% shellac (manufactured by Koyo Chemical Co., Ltd.) was diluted with anhydrous ethanol from Kenei Pharmaceutical Co., Ltd. to prepare alcoholic dilution of shellac with a solid shellac content of 25.0% by mass.
  • the refractive index was 1.46.
  • the refractive index was measured using an Appe type refractometer from Atago Co., Ltd.
  • Sumifix HF Navy 2G gran solution (indigo blue) manufactured by Sumika Chemtex Co., Ltd. was added dropwise to the total mass of the diluted solution at 0.2% by mass, and dispersed using a rotating and revolving mixer Awatori Rentaro ARE310 manufactured by Thinky Co., Ltd. to prepare impregnation-coating solution.
  • the viscosity of the impregnation-coating solution at 30°C and 60 rpm was 1200 mPa ⁇ s.
  • the impregnation-coating solution 1 was coated and impregnated to the surface opposite the highly smooth surface of the base paper of translucent paper obtained in Manufacturing examples 1 to 11, and the surface was dried at 100°C for 5 minutes using a HEATTECH hot air circulation dryer.
  • the base paper for translucent paper, the type of impregnation-coating solution, and the amount of impregnation are shown in Tables 3 and 4.
  • the impregnation-coating solution 2 was impregnation-coated on the surface opposite to the highly smooth surface of the base paper for translucent paper obtained in Manufacturing Example 1 using a Hand K Rocks engraving roll (specifications 100/18) manufactured by Laurent Co., Ltd. Specifically, the impregnation-coating solution 2 was repeatedly coated by the rubber roll transfer method so that the amount of shellac was 18 g/m 2 , and then dried at room temperature to obtain translucent paper.
  • the luminous transmittance (T50) was measured using the TLV-304-LC luminous transmittance measuring device manufactured by Asahi Spectroscopy Co., Ltd., as shown in FIG. 6 .
  • Luminous transmittance ratio T 50 / T 0 x 100
  • Haze was measured using the "HZ-V3" (manufactured by Suga Test Instruments) in accordance with JIS-K7136.
  • An A4 printout of a 10.5 point Word document was placed on a level stand, and the wrapping paper of each example was placed 5.0 cm above it. Furthermore, the visibility of the characters on the printout when viewed through the translucent region of the wrapping paper from a position 30 cm above the wrapping paper was evaluated based on the following criteria:
  • the translucent paper obtained was torn by hand into 10 mm squares to prepare a solution with a concentration of 3%. 500 ml of the solution was stirred for 30 seconds in a household mixer, Tescom TM856-W mixer, and then sieved through HOGA 12 mesh sieve.
  • the wrapping paper of the examples had excellent visibility in the depth direction.
  • the wrapping paper of the Comparative Examples which had a translucent region in which the luminous transmittance (T50) and the luminous transmittance ratio did not meet the specified requirements, had poor visibility evaluation results.
  • the numerical trends of the luminous transmittance (T50) and the luminous transmittance ratio were roughly consistent with the trends of superiority and inferiority of visibility by human visual inspection.
  • translucent paper is provided that has excellent visibility when viewed through a translucent region.

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EP23846626.2A 2022-07-29 2023-07-27 Base paper for translucent paper, translucent paper, and method for manufacturing translucent paper Pending EP4563744A1 (en)

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PCT/JP2023/027606 WO2024024896A1 (ja) 2022-07-29 2023-07-27 半透明化紙用原紙、半透明化紙及び半透明化紙の製造方法

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JPS5418914A (en) * 1977-07-13 1979-02-13 Mitsubishi Paper Mills Ltd Production of transparent paper
JPS6147354A (ja) * 1984-08-01 1986-03-07 十條製紙株式会社 高透明シ−ト
JPS61132698A (ja) 1984-11-30 1986-06-20 サイデン化学株式会社 透明紙の製造法
JPS61132699A (ja) 1984-11-30 1986-06-20 サイデン化学株式会社 透明紙の製造方法
JPH026682A (ja) * 1987-12-01 1990-01-10 Honshu Paper Co Ltd 剥離紙用原紙
JP6793485B2 (ja) 2016-07-11 2020-12-02 アイカ工業株式会社 光硬化性樹脂組成物
CN111235952A (zh) * 2018-11-28 2020-06-05 蒋爱华 一种透明纸张生产用浸渍液
JP7375736B2 (ja) 2019-12-11 2023-11-08 王子ホールディングス株式会社 紙製包装体
JP7463935B2 (ja) * 2020-10-08 2024-04-09 王子ホールディングス株式会社 透明紙、包装材、ラベル、透明化剤

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