Functional paper product

Abstract

The present invention provides a functional paper product that is water-resistant, oil-resistant, and recyclable. A functional paper product (1) according to the present invention is composed of a base paper (20) and a coating film (10) formed on the base paper (20). The coating film (10) is mainly composed of a modified mannan in which the acetyl group of konjak mannan is released. Swollen modified mannan sol, in which the viscosity of the swollen modified mannan before hardening is 3000 mPa·s or lower, is hardened in a state of having infiltrated into the gaps between cellulose fibers of the base paper (20).

Description

Functional paper products

[0001] The present invention relates to a functional paper product that is excellent in water resistance, oil resistance, and durability, and is recyclable.

[0002] Currently, plastic packaging materials, packaging containers, food containers, straws, etc. are used in a variety of situations. They are highly water-resistant and oil-resistant, and are convenient because they can accommodate a variety of items, foods, and beverages. However, environmental issues have been raised regarding the disposal of plastic packaging materials, packaging containers, food containers, and straws.

[0003] Another method is to laminate paper products, including cardboard boxes and paper plates, with polyethylene film. However, this method also significantly increases the manufacturing cost, and because the paper products are laminated, they cannot be recycled.

[0004] In this situation, Patent Document 1 discloses an invention of a method for manufacturing a food container, in which water, glucomannan, and an alkali are mixed and stirred to liberate acetyl groups and inhibit swelling of modified mannan, and the swelling inhibition of the modified mannan is released by neutralization to obtain a neutral or acidic mannan sol or a mannan gel obtained by gelling the mannan sol, which is then applied to a paper food container and dried.

[0005] According to the invention described in Patent Document 1, food containers have better water resistance and oil resistance than conventional containers, have a lower environmental impact, and can be manufactured at low cost.Furthermore, the food containers of this invention are recyclable because they disintegrate in water.

[0006] International Publication No. 2021 / 166017

[0007] The swollen modified mannan described in Patent Document 1 has a predetermined viscosity, but in order to mass-produce paper products at low cost using general-purpose printing equipment owned by paper manufacturers and printing companies, it is necessary to apply the swollen modified mannan to paper at a relatively low viscosity.

[0008] In view of the above problems, the present invention aims to provide a functional paper product that can be mass-produced using general-purpose equipment at paper manufacturing companies and printing companies, has excellent water resistance, oil resistance, and durability, and is recyclable.

[0009] The present inventors have investigated the above-mentioned problems and have found that by applying the above-mentioned swollen modified mannan with reduced viscosity when it is applied to base paper, the swollen modified mannan can infiltrate into the gaps between the cellulose fibers of the base paper and harden in a state where it is intricately entangled with the cellulose fibers.

[0010] The present invention has been made based on this finding, and provides a functional paper product consisting of base paper and a coating formed on the base paper, wherein the coating is primarily composed of modified mannan in which the acetyl groups of konjac mannan have been released, and the functional paper product is produced by hardening a swollen modified mannan sol in which the viscosity of the swollen modified mannan before hardening is 3000 mPa·s or less while infiltrating into the gaps between the cellulose fibers of the base paper.

[0011] According to the present invention, functional paper products that are water-resistant and oil-resistant while suppressing the generation of konjac odor, harshness, astringency, etc. can be mass-produced efficiently and inexpensively using the existing facilities of paper manufacturers, printing companies, etc., without the need to install new coating equipment. Furthermore, durability can be imparted in addition to water resistance and oil resistance.

[0012] 1 is a cross-sectional view of (a) a conventional paper product (i.e., base paper 10 on which no coating is formed) and (b) a functional paper product 1 according to the present embodiment. (a) A cross-sectional view of a conventional paper product and (b) a scanning microscope photograph of the surface of a functional paper product according to the present embodiment. (b) A graph showing the time course of viscosity at a swollen modified mannan concentration of 1%. (c) A graph showing the time course of viscosity at a swollen modified mannan concentration of 1.2%. (d) A graph showing the time course of viscosity at a swollen modified mannan concentration of 1.4%. (e) A graph showing the time course of viscosity at a swollen modified mannan concentration of 1% or less. (f) A table showing the viscosity reduction rate depending on the temperature range and stirring time at a swollen modified mannan concentration of 1%. (g) A table showing the results of a 24-hour verification test using a Gurley-Cobb size tester. (h) A graph and table comparing the film thickness of swollen modified mannan sol at different paper smoothness levels. (i) A graph showing the results of a water resistance test of hamburger wrapping base paper coated with swollen modified mannan sol using a No. 5 coating rod. 1 is a graph showing the results of a water resistance test of hamburger wrapper base paper coated with swollen modified mannan sol using coating rod No. 48. Scanning microscope photographs of paper coated with swollen modified mannan sol: (a) shows the condition of the coated surface after a single application of swollen modified mannan sol with 300-fold hydration using coating rod No. 5. (b) shows the condition of the coated surface after two applications of the same swollen modified mannan sol as in (a). (c) shows the condition of the coated surface after three applications of the same swollen modified mannan sol as in (a). Scanning microscope photographs of paper coated with swollen modified mannan sol: (a) shows the condition of the coated surface after a single application of swollen modified mannan sol with 300-fold hydration using coating rod No. 48. (b) shows the condition of the coated surface after a single application of swollen modified mannan sol with 150-fold hydration using coating rod No. 5. (a) is an optical microscope photograph of a paper surface that has not been coated with swollen modified mannan sol, and (b) is an optical microscope photograph of a paper surface that has been coated with swollen modified mannan sol at a 300-fold water addition ratio three times using a No. 5 coating rod. The photographs show the state of a chocolate confectionery placed on a functional paper product coated with swollen modified mannan sol, followed by observation over time.

[0013] The functional paper product according to the embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows (a) a cross-sectional view of a conventional paper product (i.e., base paper 10 without a coating) and (b) a cross-sectional view of the functional paper product 1 according to the present embodiment. Figure 2 also shows (a) a cross-sectional view of the conventional paper product and (b) a scanning microscope photograph of the surface of the functional paper product according to the present embodiment.

[0014] The functional paper product 1 according to this embodiment comprises a base paper 20 and a coating 10 formed on the base paper 20 .

[0015] The type of base paper 20 is not particularly limited, and any paper used for the purpose of imparting water resistance, oil resistance, and durability, such as food base paper, tableware base paper, and cardboard base paper, can be used. It is particularly preferable to select paper used for manufacturing paper food containers and paper tableware. Examples of food containers include paper cups, paper cups, paper plates, paper trays, ice cream containers, milk containers, sake containers, soft drink containers, ramen containers, rice bowl containers, and confectionery containers. Examples of tableware include spoons, forks, chopsticks, straws, stirrers, and paper knives. Other paper products include laundry detergent containers, kitchen detergent containers, dressing containers, pickle containers, liquid detergent and cosmetic containers, food container lids, hamburger wrapping paper and boxes, paper bags, and other packaging paper.

[0016] The coating 10 is mainly composed of modified mannan in which the acetyl groups of konjac mannan have been released, and is formed by hardening a swollen modified mannan sol in which the viscosity of the swollen modified mannan before hardening is 3000 mPa·s or less while infiltrating into the gaps between the cellulose fibers of the base paper 20.

[0017] As shown in Figure 1 (b), the swollen modified mannan sol hardens while infiltrating into the gaps between the cellulose fibers of the base paper 20, so the coating 10 and the base paper 20 are firmly bonded together, and no adhesive is required to bond the base paper 20 and the coating 10 together.

[0018] 1(b) appears to have a two-layer structure in order to explain the relationship between the base paper 20 and the coating 10, but in reality, the swollen modified mannan sol hardens while infiltrating into the gaps between the cellulose fibers of the base paper 20, so the thickness of the coating 10 is almost the same as that of the base paper 20, and there is no clear boundary surface between the base paper 20 and the coating 10. Therefore, the coating 10 can impart water resistance, oil resistance, and durability without interfering with the original uses and functions of conventional paper products.

[0019] As shown in Figure 2(a), there are many gaps between the cellulose fibers in the base paper 20, and when liquid is poured into the base paper 20, the liquid leaks out through these gaps. In contrast, the functional paper product 1 according to this embodiment is formed so that the gaps between the cellulose fibers of the base paper 20 are covered with a coating 10, as shown in Figure 2(b), so that even when liquid is poured, the liquid is retained without leaking, achieving water resistance and oil resistance. Furthermore, in addition to liquids such as water and oil, solids and gases can also be retained.

[0020] As shown in Figure 2(b), the coating 10 is preferably formed so as to completely fill the gaps (holes) between the cellulose fibers of the base paper 20. However, depending on the application of the functional paper product of this embodiment, it is not necessarily necessary to form a complete coating without gaps (holes). For example, when the functional paper product of this embodiment is made into plates, knives, forks, spoons, bags, or packaging paper, these applications do not require complete water resistance or oil resistance. The same is true for cups, bowls, and beverage cartons. This is because when the coating 10 comes into contact with water, it absorbs moisture and swells, filling the voids in the base paper. This is due to the fact that the raw material of the coating 10 is konjac mannan.

[0021] Even if the coating 10 absorbs water and swells, due to the inherent irreversibility of konjac, the coating 10 will not dissolve or return to the swollen modified mannan sol before hardening. Furthermore, since the coating 10 has the same strength as a general polyethylene film, it is resistant to high and low temperatures and acids and alkalis.

[0022] The functional paper product according to this embodiment can be formed into shapes such as a cube, rectangular parallelepiped, or approximately triangular pyramid to produce a beverage carton for containing beverages such as milk. Furthermore, by forming it into a bag, it can be used as a paper bag as an alternative to plastic shopping bags. Additionally, the dried paper can be formed into any shape, such as a spoon, fork, chopsticks, straw, stirrer, or plate. By forming it into a desired shape in this way, various functional paper products can be obtained. Furthermore, it can also be used as packaging paper for foods such as hamburgers. Furthermore, because the functional paper product according to this embodiment is water-resistant and oil-resistant, it can be used for purposes other than the functional paper products exemplified above, as long as water-resistant and oil-resistant properties are required.

[0023] An example of a functional paper product other than the functional paper products exemplified above is corrugated cardboard. That is, by using corrugated cardboard base paper (linerboard and / or core base paper) for the base paper 20, it is possible to provide corrugated cardboard that is more water-resistant, oil-resistant, and durable than ordinary corrugated cardboard. Corrugated cardboard with such added functionality can be used not only as a packaging material to protect products from scratches, stains, crushing, etc. as in the past, but also for meat, seafood, vegetables, frozen foods, and other items that could only be packed in polystyrene foam containers.

[0024] Furthermore, the paper can be used in functional paper products, such as umbrella fabrics, raincoats, and hats.

[0025] Next, a method for producing a functional paper product according to an embodiment of the present invention will be described. The swollen modified mannan sol to be applied to the functional paper product of the present invention is within the following range. Specifically, as disclosed in Japanese Patent No. 6089308, modified mannan is used, in which acetyl groups are liberated and swelling is inhibited by mixing and stirring water, konjac mannan, and alkali. This modified mannan is neutralized to lower the pH of the modified mannan, thereby releasing the swelling inhibition. The swollen modified mannan sol, in which the acetyl groups have been liberated, has the ability to gel even in the acidic to weakly alkaline pH range, and is free of the konjac odor, harshness, and astringency, making it preferable to use this type of mannan.

[0026] However, in addition to the above-mentioned swollen modified mannan sol, any mannan sol that has the ability to gel even under low pH conditions, such as a mannan sol that gels in the acidic to neutral pH range, or a sol in which modified konjac powder deacetylated with alkali or enzymes is dispersed in water, may be used.

[0027] Next, a method for producing a swollen modified mannan sol for application to paper products will be described.

[0028] Swollen modified mannan sol can be obtained by subjecting konjac mannan to alkali treatment and neutralization treatment. Konjac mannan is mixed with water, alkali, and the mixture is stirred for 1 to 100 minutes to inhibit swelling, and the acetyl groups are released to obtain modified mannan. The resulting modified mannan is then neutralized to release the swelling. When the modified mannan has swollen, stirring is stopped and the mixture is allowed to swell sufficiently, yielding a swollen modified mannan sol.

[0029] Konjac mannan can be one or a mixture of two or more of ground konjac root, konjac flour, and konjac mannan obtained by washing konjac flour with an alcoholic aqueous solution. There is no particular restriction on the variety of konjac root, and any variety of konjac root belonging to the genus Amorphophallus of the family Araceae that contains konjac mannan can be used.

[0030] The ratio of konjac mannan to alkaline solution is preferably 1 part konjac mannan to 10 to 500 parts water, and the water temperature is preferably 60°C or less.

[0031] The alkali to be added may be strong, and examples include calcium hydroxide, calcined shell calcium, and eggshell calcium. The amount of alkali must be sufficient to liberate the acetyl groups in konjac mannan and inhibit swelling, and is greater than the amount of alkali used in producing konjac for general food use. In the case of calcium hydroxide, the amount is preferably 7.6% or more of the weight of konjac mannan.

[0032] The pH of the alkaline solution is preferably 11.7 or higher, and if the pH is too low, swelling cannot be suppressed. If the pH is too high, swelling suppression may not be released depending on the type and degree of purification.

[0033] Swelling inhibition means suppressing the inherent ability of konjac mannan to swell (speed, viscosity, etc.). For example, when ordinary konjac for food use is produced using premium konjac mannan of the KONJAC variety produced in Japan, calcium hydroxide is used in an amount of about 3 to 6% of the weight of the konjac mannan. However, by using a larger amount of calcium hydroxide that slows down the swelling speed or reduces the viscosity, the swelling can be suppressed.

[0034] The acetyl groups of konjac mannan are liberated by alkali treatment, and the swelling-inhibited modified mannan is mixed with a water-alkali mixture, and a food or neutralizing agent is added to remove the swelling inhibition, resulting in a swollen modified mannan sol. The food or neutralizing agent used may be any substance that removes the swelling inhibition, and a food or neutralizing agent that lowers the pH is preferred. After addition, stirring causes swelling within a few seconds to 60 minutes, resulting in a swollen modified mannan sol.

[0035] The swollen modified mannan sol produced as described above is applied to a base paper and dried. In this case, hot air drying is preferred, but other drying methods such as natural drying and vacuum drying may also be used.

[0036] Next, the dried paper (paper coated with the swollen modified mannan sol and dried) is molded into the shape of the desired paper product, thereby obtaining water-resistant, oil-resistant, and durable functional paper products of any shape, such as plates, cups, bowls, and boxes.

[0037] The resulting functional paper product can then be molded into any shape, such as a cube, rectangular parallelepiped, roughly triangular pyramid, or bag, depending on the intended use. Additionally, the dried paper can be molded into any shape, such as a spoon, fork, chopsticks, straw, or stirrer. By molding into the desired shape in this way, various functional paper products can be obtained. Furthermore, it can also be used as packaging paper for foods such as hamburgers.

[0038] Next, the viscosity adjustment of the swollen modified mannan when applying the mannan to the base paper will be described.

[0039] When functional paper products are mass-produced by applying swollen modified mannan, it is desirable that the viscosity be 3000 mPa·s or less, preferably 1000 mPa·s or less, depending on the specifications of existing manufacturing equipment.

[0040] It is known that the viscosity value of the swollen denatured mannan in the present invention decreases with increasing temperature. Therefore, three types of mannan with mannan concentrations of 1%, 1.2%, and 1.4% were tested in a thermostatic water bath at four temperatures: 28°C, 35°C, 40°C, and 50°C, with stirring at 90 rpm for 5 hours (viscosity value measured every hour). The viscosity values ​​were measured after 4 hours at 35°C (rotation speed 30 rpm) using a Toki Sangyo Co., Ltd. viscometer "TVB-10 Model" with a rotor M4.

[0041] The test results are shown in graphs in Figures 3 to 5 for each mannan concentration. The test results show that, when the mannan concentration is 1%, the viscosity can be reduced to 3,000 mPa·s or less by controlling the temperature in the 40-50°C range. These results also show that in order to further reduce the viscosity, the mannan concentration must be reduced to 1% or less.

[0042] Therefore, to examine mannan concentrations of 1% or less, four hydration ratios were used: 150 times (mannan concentration 0.66%), 200 times (mannan concentration 0.5%), 250 times (mannan concentration 0.4%), and 300 times (mannan concentration 0.33%). Tests were conducted at 35°C in a thermostatic water bath with a stirring speed of 90 rpm for 4 hours (viscosity values ​​were measured every hour).

[0043] The test results are shown in a graph in Figure 6 for each hydration ratio of mannan (the numbers in parentheses are concentrations). The test results show that the viscosity value can be reduced to 3000 mPa s or less at any hydration ratio, and that a hydration ratio of 200 times or more can reduce the viscosity to approximately 1000 mPa s or less.

[0044] Figure 7 shows the experimental results of viscosity reduction rates at 1% mannan concentration depending on the temperature range and stirring time (stirring speed: 90 rpm). As shown in the table, increasing the temperature significantly reduces the viscosity value. This indicates that even when the mannan concentration is 1%, 1.2%, or 1.4%, the viscosity value of the swollen modified mannan sol can be reduced to 3,000 mPa·s or less, or even 1,000 mPa·s or less, by increasing the temperature and adjusting the stirring time.

[0045] As mentioned above, while the viscosity value can be reduced by reducing the mannan concentration to 1% or less, lowering the mannan concentration also reduces the mannan fiber content in the mannan, which may affect the film thickness of the swollen modified mannan sol when applied to base paper and dried, as well as the penetration of water and oil into the cellulose fiber structure of the base paper, potentially affecting water and oil resistance.

[0046] Therefore, we estimated the mannan fiber content for each hydration ratio, applied it to base paper, and conducted a 24-hour verification test to verify water and oil resistance, including bleeding to the back of the paper.

[0047] The swollen modified mannan sol used in the verification was produced as follows: Japanese konjac mannan (KONJAC variety) and calcium hydroxide were added to 100 cc of water at 12°C, and the mixture was stirred for 10 minutes. Then, 0.15 g of citric acid as a neutralizer was added. Once the mixture swelled, the stirring was stopped and the mixture was left to stand for 60 to 120 minutes to produce a swollen modified mannan sol. The swollen modified mannan sol was then applied to base paper and dried. Note that citric acid was added as a neutralizer to produce a neutral swollen modified mannan sol, but a slightly larger amount of citric acid was added to produce an acidic swollen modified mannan sol. Note that instead of citric acid, other acidic substances or acid-containing foods that can be used as neutralizers may be used.

[0048] To confirm water resistance, a water absorbency test was performed using a water absorbency tester. The water absorbency tester used was a Garle Cobb Size Tester (standard type) manufactured by Kumagaya Riki Kogyo Co., Ltd. Base paper for food containers was used as the test paper. The swollen modified mannan sol was applied to the base paper using coating rods No. 5 and No. 48 manufactured by Kumagaya Riki Kogyo Co., Ltd., at thicknesses of 11.43 μm (for No. 5) and 109.8 μm (for No. 48), respectively.

[0049] In the 24-hour verification test using the Garle Cobb Size Tester, tea beverages were used as samples to check water resistance, and coffee beverages and household cooking oil were used as samples to check oil resistance. In addition, chocolate was also tested by direct contact (approximately 8 months of continuous contact).

[0050] The results of the verification are shown in the table in Figure 8. As shown in the table, the relationship between the mannan content and water / oil resistance shows that the lower limit is about 0.26 g of mannan per 100 cc, and that 0.5 g or more is preferable whenever possible. This means that the mannan content can be adjusted depending on the production cost and application (required water / oil resistance).

[0051] Furthermore, when examining the relationship between the film thickness of the applied, swollen modified mannan sol before hardening and water / oil resistance, the lower limit of the film thickness before hardening is about 3 μm, and preferably 5 μm or more if possible, depending on the content of the swollen modified mannan sol. As shown in the table, in the case of household cooking oil, oil resistance is improved by applying the swollen modified mannan sol multiple times to increase the film thickness. This means that the film thickness before hardening can be adjusted depending on the production cost and application (the required strength of water / oil resistance).

[0052] Regarding water resistance, it is possible to solve cost problems by changing the hydration ratio and the film thickness before hardening depending on the application and conditions of use of the paper product to be used. For example, when manufacturing swollen modified mannan sol-coated paper trays to replace the PVC food trays sold at general mass retailers, if the moisture content of the food is low, the hydration ratio can be set to about 500 times and the film thickness before hardening to about 3 μm, making it possible to manufacture them more cheaply than PVC food trays. Conversely, if the moisture content of the food is high, it is possible to prevent moisture penetration by applying swollen modified mannan sol to the front and back of the tray, for example.

[0053] In the case of paper cups, water resistance can be ensured by applying swollen modified mannan sol to the inside of the surface that comes into contact with water under normal conditions of use, but when the cup is used for a long period of time with ice, such as for iced coffee, applying swollen modified mannan sol to the front and back of the paper cup can achieve performance equivalent to that of a PVC cup.Of course, it is also possible to achieve performance equivalent to that of a PVC cup lid by applying swollen modified mannan sol to the front and back of a paper cup lid.

[0054] Furthermore, based on the results of the above-mentioned verification, as shown in Figure 14, verification was also carried out on the case where chocolate was directly contacted (contact continued for about 8 months). In the example shown in the figure, a mannan aqueous solution with a hydration ratio of 250 times, which contains very little mannan dietary fiber, was used, and a very small amount of application (0.11 g / m ２ ) No oil seepage was observed on the contact surface or back side of the swollen modified mannan sol coated paper. Therefore, it was confirmed that the paper exhibits oil resistance equivalent to that of PVC-processed packaging materials, and it can be used as a packaging material for chocolate products in the same way as PVC-processed packaging materials or aluminum packaging materials.

[0055] Next, the surface treatment of paper coated with swollen modified mannan sol can make a big difference in water and oil resistance. This is influenced by the properties of mannan. For example, when swollen modified mannan sol is applied to copy paper used in general jet printers and water and oil resistance tests are conducted, the water and oil resistance tends to be lower than that of general paper with an untreated surface. The same tendency is observed in paper with a water-resistant surface.

[0056] Therefore, we used base paper with different smoothness and actually applied swollen modified mannan sol using coating rods No. 5 and No. 48 to confirm the results. As a result of this confirmation, as shown in Figure 9, it was found that, particularly when increasing the film thickness, a lower smoothness of the base paper allows for a thicker film thickness, and that a lower smoothness of the base paper is preferable. In other words, keeping the smoothness of the base paper as low as possible and applying swollen modified mannan sol to the untreated surface leads to improved water and oil resistance. Furthermore, even if swollen modified mannan sol is applied to paper that has been treated with chemicals or other water-resistant agents on the surface of the base paper, a sufficient film thickness cannot be ensured, and therefore water and oil resistance does not improve.

[0057] Next, a functional paper product, hamburger wrapping base paper (45 g / m ２ The results of a water resistance test conducted by applying swollen modified mannan sol at a hydration ratio of 100 to 500 times to a hamburger wrapper base paper are described below. That is, in the water resistance test, the swollen modified mannan sol was applied to a hamburger wrapper base paper using coating rods No. 5 and No. 48 to prepare a box-shaped container (7.5 cm x 8 cm, depth 3.8 cm), and about 40 cc of room temperature tea was poured into the box-shaped container, and the elapsed time until leakage was confirmed was investigated.

[0058] As the results of the water resistance test, Fig. 10 shows the test results of a hamburger wrapping paper coated with modified mannan sol swollen by coating rod No. 5, and Fig. 10 shows the test results of a hamburger wrapping paper coated with modified mannan sol swollen by coating rod No. 48. Figs. 10 and 11 show the estimated mannan fiber content along with each hydration ratio.

[0059] Furthermore, in the above water resistance test, a comparison was made using hamburger wrapping paper base paper not coated with swollen modified mannan sol. Water leakage from the box-shaped container was confirmed after 4 minutes and 15 seconds. On the other hand, hamburger wrapping paper coated with modified mannan sol swollen by coating rod No. 5 exhibited water resistance of 1.5 hours (hours) even at a 500-fold hydration ratio, and 11.3 hours (hours) at a 100-fold hydration ratio. Furthermore, hamburger wrapping paper coated with modified mannan sol swollen by coating rod No. 48 exhibited water resistance of 2.5 hours (hours) even at a 500-fold hydration ratio, and 23.8 hours (hours) at a 100-fold hydration ratio.

[0060] From the results of the water resistance test, it is possible to significantly improve water resistance by setting the hydration ratio at least to 500 times or less. More preferably, by setting the hydration ratio to 400 times or less, and even more preferably to 300 times or less, water resistance for half a day or more can be ensured, making it possible to significantly improve water resistance.

[0061] In addition, as can be seen from the amount of mannan fiber shown in the water resistance test results shown in Figure 10, it is at least 0.01 g / m ２ or more, preferably 0.017 g / m ２ By applying the above amount of mannan fiber to the base paper, it is possible to significantly improve the water resistance.

[0062] Next, we investigated the effect of applying swollen modified mannan sol on the durability of base paper. Conventionally, the final product is manufactured by increasing the thickness of the base paper depending on the required durability of the paper product. However, this increases the amount of base paper used, leading to increased costs and environmental impact.

[0063] Therefore, in this verification, swollen modified mannan sol was applied to copy paper, and burst strength and other properties were measured using a KRK burst strength tester manufactured by Kumagaya Riki Kogyo Co., Ltd., and durability (tensile strength, etc.) was measured using a horizontal tensile tester (desktop type). The burst strength test results showed that when the swollen modified mannan sol was applied to one side of the paper, the burst strength was improved by 140.6% compared to uncoated paper, and when the swollen modified mannan sol was applied to both sides of the paper, the burst strength was improved by 158.1% compared to uncoated paper. Furthermore, in terms of tensile strength, when the swollen modified mannan sol was applied to one side of the paper, the longitudinal breaking length was improved by 110.1% compared to uncoated paper, and the transverse breaking length was improved by 110.9%.

[0064] Cardboard boxes and paper containers can be damaged from the outside when stacked or during transportation, but the above-mentioned verification results show that in order to ensure the required burst strength and tensile strength, by applying swollen modified mannan sol to one side of the paper as needed, or to both sides, it is possible to improve the durability of paper products without increasing the thickness of the base paper or the amount of base paper used, as in the past.

[0065] In other words, in the case of corrugated cardboard, applying swollen modified mannan sol to one side ensures water resistance and improves burst strength and tensile strength. This also makes it possible to reduce the thickness of conventionally used corrugated cardboard (linerboard) and reduce costs. Of course, applying swollen modified mannan sol to both sides of the corrugated cardboard as needed can further improve burst strength and tensile strength. Furthermore, applying swollen modified mannan sol to the core paper, which is necessary for corrugated cardboard strength, can achieve the same effect.

[0066] Table 1 shows the results of examining the breaking strength, burst index, tensile strength, and breaking length, which are indicators of durability, of functional paper products manufactured by forming a coating 20 on the surface of liner paper, using liner paper as base paper 10.

[0067] The liner paper used was LB-grade liner paper according to JIS standard (JIS P3902). The swollen modified mannan sol was applied once with a No. 5 or No. 48 coating rod at a hydration ratio of 150 (mannan concentration of 0.66%). The test was carried out under the following conditions: temperature 22.6°C, humidity 38%, test machine C type (kPa), span 100 mm.

[0068] As shown in Table 1, the liners (Sample 1 and Sample 2) coated with swollen modified mannan showed significant improvements in burst strength, burst index, tensile strength, and breaking length compared to the base paper. These results demonstrate that forming a coating made from cured swollen modified mannan sol can improve the quality of corrugated board without increasing the thickness of the paper. Furthermore, because the formed coating has high frictional force, forming the coating also increases the frictional resistance of the corrugated board, eliminating the need for the commonly performed friction treatment of corrugated board. Although data is not shown, functional paper products formed with a coating 20 on liner base paper also have water and oil resistance.

[0069]

[0070] Table 2 shows the results of examining the burst strength, longitudinal strength (tensile strength and elongation), and transverse strength (tensile strength and elongation), which are indicators of the durability of the core raw paper, produced from functional paper products in which a coating 20 is formed on the surface of the core raw paper, using the core raw paper as base paper 10. The measuring equipment and conditions were the same as those for the liner paper described above.

[0071] The core raw paper used was MB-grade core raw paper according to JIS standard (JIS P3902). The swollen modified mannan sol was applied once with a No. 5 or No. 48 coating rod at a water addition ratio of 150 (mannan concentration: 0.66%).

[0072] As shown in Table 2, the liners (Sample 3 and Sample 4) coated with swollen modified mannan had burst strength, longitudinal strength, and transverse strength equal to or greater than those of the core raw paper. These results demonstrate that the durability of core raw paper can be improved by forming a coating of cured swollen modified mannan sol on the core raw paper. Corrugated cardboard is used to impart strength to cardboard, and the core of this embodiment can add strength to the cardboard without increasing the weight of the core. Although data is not shown, functional paper products in which a coating 20 is formed on the core raw paper are also imparted with water resistance and oil resistance.

[0073]

[0074] (Verification by Micrograph) Next, the following will be explained based on a micrograph of the surface coated with swollen modified mannan sol. Figure 12 shows scanning micrographs of paper coated with swollen modified mannan sol, in which (a) shows the state of the surface coated with swollen modified mannan sol at a 300-fold hydration ratio once using a No. 5 coating rod, (b) shows the state of the surface coated with the same swollen modified mannan sol as (a) twice, and (c) shows the state of the surface coated with the same swollen modified mannan sol as (a) three times.

[0075] As shown in Figure 12(a), it can be seen that a film of swollen modified mannan sol is formed in the gaps between the cellulose fibers of the paper, but there are some cavities that appear black in places. Also, as shown in Figure 11(b), when the swollen modified mannan sol is applied twice, a film of swollen modified mannan sol is formed more in the gaps between the cellulose fibers, and the cavities are significantly reduced. Furthermore, as shown in Figure 12(c), when the swollen modified mannan sol is applied three times, almost no cavities are found, and it can be seen that a film of swollen modified mannan sol is reliably formed over a wide area.

[0076] In other words, by increasing the number of times the swollen modified mannan sol is applied, a film of the swollen modified mannan sol is evenly formed on the surface of the paper, and it can be confirmed that the mannan fibers penetrate into the gaps between the cellulose fibers of the base paper. This contributes greatly to the water resistance and oil resistance of functional paper products. Note that base paper whose surface has been treated with anti-bleed agents or chemicals for water resistance processing is not preferred because it inhibits the formation of the mannan film as described above.

[0077] Next, Figure 13(a) shows a scanning microscope photograph of a coated surface where swollen modified mannan sol at a 300-fold hydration ratio was applied once using a No. 48 coating rod, and Figure 13(b) shows a scanning microscope photograph of a coated surface where swollen modified mannan sol at a 150-fold hydration ratio was applied once using a No. 5 coating rod. Comparing these, it can be seen that there are fewer remaining gaps in Figure 13(a) than in Figure 13(b). Therefore, even when the hydration ratio is increased, by increasing the film thickness of the swollen modified mannan sol, it is possible to more reliably form a film of swollen modified mannan sol on the surface of the base paper.

[0078] 14(a) shows an optical microscope photograph of the surface of base paper not coated with swollen modified mannan sol, and FIG. 14(b) shows an optical microscope photograph of the surface of paper coated with swollen modified mannan sol at a 300-fold water addition ratio three times using a No. 5 coating rod. As shown in the figure, the surface not coated with swollen modified mannan sol is subject to diffuse reflection of light by the cellulose fibers of the base paper, resulting in a vague outline of the cellulose fibers and an overall dark appearance. On the other hand, the surface coated with swollen modified mannan sol three times, on which a film of swollen modified mannan sol was formed overall, shows an iridescent film and clearly visible outlines of the cellulose fibers, resulting in an overall bright appearance.

[0079] (Observation of foods containing fats and oils) Figure 15 shows a photograph of a chocolate confectionery placed on a functional paper product coated with swollen modified mannan sol, and the situation was observed over time. The example shown in the photograph is one with a 250-fold water addition ratio, but no oil seepage was observed over a period of eight months.

[0080] Other Embodiments Although several embodiments of the functional paper product of the present invention have been described above, the present invention is not necessarily limited to the above-described embodiments, and the following embodiments are also possible.

[0081] For example, the above-mentioned verification results mainly focused on modified mannan sol swollen with a hydration ratio of 100 to 500 times, but the range is not necessarily limited to this. For example, it is also possible to increase the hydration ratio to 500 to 3000 times, and verification has made it clear that water resistance and oil resistance can be ensured even within this range. Within this range of hydration ratio, the viscosity becomes very low, making it easy to apply using general-purpose machines.

[0082] On the other hand, when the hydration ratio is between 500 and 3000 times, the concentration of the swollen modified mannan sol decreases, and therefore it is necessary to satisfy the required performance by increasing the number of applications depending on the water resistance and oil resistance required of the functional paper product. Therefore, from the viewpoint of using the existing facilities of paper manufacturers, printing companies, etc. and efficiently mass-producing high-quality functional paper products, a hydration ratio of 100 to 500 times is said to be a preferable range.

[0083] The present invention makes it possible to mass-produce functional paper products that are water-resistant and oil-resistant while suppressing the generation of konjac odor, harshness, astringency, etc. efficiently and inexpensively using existing facilities of paper manufacturers, printing companies, etc., without installing new coating equipment.

[0084] 1... Functional paper product according to this embodiment 10... Coating 20... Base paper

Claims

1. A functional paper product consisting of a base paper and a coating formed on the base paper, the coating being mainly composed of modified mannan in which the acetyl groups of konjac mannan have been liberated, and the swollen modified mannan sol, in which the viscosity of the swollen modified mannan before hardening is 3000 mPa·s or less, is hardened while infiltrating into the gaps between the cellulose fibers of the base paper.

2. The functional paper product according to claim 1, wherein the viscosity of the swollen modified mannan sol before hardening is 1000 mPa·s or less.

3. The amount of mannan fiber in the swollen modified mannan sol is 0.01 g / m ２ The functional paper product according to claim 1 or 2.

4. The functional paper product according to claim 1, wherein the base paper is at least one selected from the group consisting of base paper for food containers, base paper for tableware, and base paper for cardboard.

5. The functional paper product according to claim 1, which is at least one selected from the group consisting of paper cups, paper cups, paper plates, paper trays, ice cream containers, milk containers, liquor containers, soft drink containers, ramen containers, rice bowl containers, confectionery containers, paper bags, spoons, forks, chopsticks, straws, stirrers, paper knives, laundry detergent containers, kitchen detergent containers, dressing containers, pickle containers, liquid detergent and cosmetic containers, food container lids, hamburger wrapping paper and hamburger boxes, paper bags, wrapping paper, and cardboard.

6. The functional paper product according to claim 1, which is at least one selected from the group consisting of umbrellas, raincoats, and hats.

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