Manufacturing method of water-resistant paper body and water-resistant paper body

Abstract

To provide a manufacturing method of a water-resistant paper body capable of making a material ratio of polylactic acid small and elevating its biodegradation speed.SOLUTION: Pulp fibers 2, a polylactic acid powder 3, and a dispersant are mixed with a liquid 4 and blended by using a stirrer 5 to be dispersed therein. Then the liquid 4 where the pulp fibers 2 and the polylactic acid powder 3 are dispersed is leveled to a plane, rolled by using a roller 6 to squeeze water content, and dried, then the polylactic acid powder 3 is heated and melted in the pulp fibers 2 to couple the pulp fibers 2 to each other.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to paper bodies such as sheet products and threads made using pulp fibers, and to a method for producing waterproof paper bodies that have improved waterproofing and can hasten the rate of biodegradation when disposed of. [Background technology]

[0002] In recent years, in order to reduce the use of plastic and take other environmental measures, there has been a shift away from plastic products such as cups and straws to products made from biodegradable paper.

[0003] However, paper products become soft when they absorb moisture for a long time, making it difficult for them to maintain their shape. For this reason, products whose surfaces are coated with polylactic acid to maintain water resistance are currently in use (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-32015 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the polylactic acid used in this manner is produced from raw materials such as corn, there is a problem in that the cost of materials increases when the cost of raw materials such as corn rises.

[0006] Furthermore, when paper products coated with polylactic acid are discarded, they are often reused as fertilizer. However, when used as fertilizer in this way, the rate of biodegradation is slow, which causes the problem that it takes a long time to use as fertilizer.

[0007] Therefore, the present invention has been made with attention to the above-mentioned problems, and aims to provide a manufacturing method for waterproof paper bodies that makes it possible to reduce the material ratio of biodegradable resin and to increase the rate of biodegradation. [Means for solving the problem]

[0008] In other words, in order to solve the above-mentioned problems, the present invention provides a method for producing a waterproof paper body by comprising the steps of mixing pulp fibers with biodegradable resin powder, and, after mixing the pulp fibers with the biodegradable resin, heating and melting the biodegradable resin.

[0009] In this way, there is no need to coat the front and back of the product with biodegradable resin, so the proportion of biodegradable resin can be reduced, reducing costs and increasing the rate of biodegradation.

[0010] As one such example, the manufacturing process includes the steps of mixing pulp fibers, biodegradable resin powder, and a dispersant into a liquid, dispersing the pulp fibers and biodegradable resin powder using a mixer, forming the liquid in which the pulp fibers and biodegradable resin powder are dispersed into a flat surface, and then squeezing out the liquid. After squeezing out the liquid, the biodegradable resin is heated and melted.

[0011] In this way, the biodegradable resin is melted while the powder of the biodegradable resin is mixed inside the pulp fibers, which strongly bonds the pulp fibers and makes the product stronger.

[0012] Alternatively, a waterproof paper body can be manufactured by the steps of forming a liquid containing pulp fibers into a flat shape, spraying a biodegradable resin powder or a liquid containing biodegradable resin powder onto the flat pulp fibers, squeezing out the liquid after spraying the biodegradable resin powder, and heating and melting the biodegradable resin after removing the liquid.

[0013] In this way, the biodegradable resin powder will not agglomerate in the liquid first, and the biodegradable resin can be uniformly dispersed and melted.

[0014] The powder of biodegradable resin used in this manner has an average particle size of 5 μm to 50 μm.

[0015] By using such a powder, it becomes possible to easily mix the biodegradable resin into the pulp fibers, and it becomes possible to strengthen the bonds between the pulp fibers.

[0016] Furthermore, the powder of the biodegradable resin is mixed with the pulp fibers in a range of 5 to 15 percent by weight.

[0017] By mixing them in such a ratio, it is possible to ensure water resistance and also to increase the rate of biodegradation.

[0018] In addition, in such an invention, a powder of foamed polylactic acid is further applied to the surface.

[0019] By configuring it in this manner, the surface can be made rough, giving it a leather-like flavor, and when used as tableware, it can also reduce thermal conductivity when the tableware is held. Effect of the Invention

[0020] According to the present invention, a waterproof paper body is manufactured by comprising a step of mixing pulp fibers with biodegradable resin powder, and a step of heating and melting the biodegradable resin after mixing the pulp fibers with the biodegradable resin. This eliminates the need to coat the front and back with biodegradable resin, reduces the proportion of biodegradable resin, and reduces costs while also accelerating the rate of biodegradation. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing a manufacturing process of a waterproof paper body according to an embodiment of the present invention. [Diagram 2] FIG. 13 is a diagram showing a manufacturing process of a waterproof paper body in another embodiment. [Diagram 3] A diagram showing the flow of the manufacturing process in the same embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0023] The water-resistant paper body 1 in this embodiment is configured in the form of a sheet or thread, and comprises pulp fibers 2 that make up the paper, and biodegradable resin powder 3 that is mixed into the pulp fibers 2, and is made water-resistant by heating and melting the biodegradable resin powder 3 in a state where it is uniformly dispersed among the pulp fibers 2, and is also designed to hasten the biodegradation rate when the product is disposed of. This embodiment will be described in detail below.

[0024] First, the pulp fibers 2 are composed of fibers extracted from wood chips of hardwood or softwood, or fibers extracted from waste paper. In this case, when extracting new pulp fibers 2 from wood chips, the wood chips are crushed and the pulp fibers 2 are extracted by mechanical or chemical processes. In addition, when using waste paper, the collected waste paper is dissolved in water to remove foreign matter and ink, and the pulp fibers 2 are extracted. Note that such pulp fibers 2 have an average fiber length of 0.5 mm to 5 mm, a diameter of about 1 nm to 5 nm, and a specific gravity of about 1.5.

[0025] On the other hand, biodegradable resins are resins that are decomposed by the action of microorganisms, and bio-derived resins such as polylactic acid (PLA) and polyhydroxyalkanoate (PHA) are used. Note that polylactic acid is used here as the biodegradable resin. This polylactic acid is made from raw materials such as sugar cane and corn, and is biodegradable by microorganisms. This polylactic acid emits significantly less carbon dioxide when burned than plastics, and furthermore, it absorbs carbon dioxide from the atmosphere during the growth of the raw plant, so that carbon dioxide that causes global warming can be significantly reduced. For this reason, polylactic acid is used here as a measure against global warming.

[0026] This polylactic acid is usually used as a coating on the surface of paper, but here it is powdered and mixed into the pulp fibers 2. At this time, the average particle size of the powder 3 is set to a size within the range of 5 μm to 50 μm, and it is uniformly dispersed in the pulp fibers 2.

[0027] As shown in Fig. 1, the pulp fibers 2 and polylactic acid are put into a liquid 4 such as water and mixed in a mixer 5. At this time, the specific gravity of the pulp fibers 2 is about 1.5, and the specific gravity of the polylactic acid is about 1.25, so there is a possibility that the polylactic acid powder 3 will aggregate due to the difference in specific gravity and the polarity of the polylactic acid. For this reason, a dispersant is added and the polylactic acid is uniformly dispersed in the liquid 4 by the mixer 5.

[0028] Regarding the ratio of polylactic acid mixed into the pulp fibers 2, if the ratio of polylactic acid is reduced, the cost can be reduced but the water resistance will be deteriorated. On the other hand, if the ratio of polylactic acid is increased, the water resistance can be increased but the cost will be increased. On the other hand, since straws and paper tableware only need to maintain their water resistance for a few minutes to about an hour at most, the polylactic acid is mixed into the pulp fibers 2 at a ratio of 5 to 15 weight percent.

[0029] When producing a waterproof paper body 1 from liquid 4 in which polylactic acid and pulp fibers 2 are mixed in this way, first, as shown in Figures 1 and 3, polylactic acid and pulp fibers 2 are put into liquid 4 and mixed with a dispersant in a mixer 5 (step S1). Then, in a uniformly dispersed state, the polylactic acid and pulp fibers 2 are smoothed into a flat surface (step S2), and the water in the liquid 4 is squeezed out using rollers 6 or the like (step S3).

[0030] After squeezing out a certain amount of moisture, the material is made into a thickness suitable for the final product (step S4) and then dried (step S5).

[0031] After drying in this way, the surface is heated by the heater 7 to heat and melt the polylactic acid powder 3 (step S6).

[0032] As a result, the pulp fibers 2 are enveloped in the molten polylactic acid powder 3, strengthening the bonds between the pulp fibers 2 and enabling the strength of the sheet to be maintained.

[0033] After the polylactic acid is thus heated and melted, the sheet is cut and processed into straws, tableware, interior materials, etc. At this time, when thread is to be produced from the sheet, the sheet is cut into thin strips and the cut thin sheets are twisted to produce thread.

[0034] When producing yarn from the sheet, the pulp fibers 2 must be aligned along the longitudinal direction of the yarn, so the pulp fibers 2 are placed in running water to align the fiber direction, and in this state, the pulp fibers 2 and the polylactic acid powder 3 are leveled flatly to squeeze out the water and heat-melt the polylactic acid. After that, the sheet is cut along the longitudinal direction of the fibers to produce twisted yarn.

[0035] Furthermore, when such a waterproof paper body 1 is used as an interior material for an automobile or the like, it may be desired to give it the texture of artificial leather. In such a case, the polylactic acid is heated and melted to form a sheet, and then foamed polylactic acid is applied to the surface of the sheet and heated and melted again. Alternatively, after a certain amount of moisture has been squeezed out, foamed polylactic acid powder 3 is applied, dried, and then the polylactic acid powder 3 is heated and melted.

[0036] As described above, according to the embodiment, the waterproof paper body 1 is manufactured by including a process for mixing the pulp fibers 2 with the polylactic acid powder 3, and a process for heating and melting the polylactic acid after mixing the pulp fibers 2 with the polylactic acid. This eliminates the need to coat the front and back with polylactic acid, making it possible to reduce the proportion of polylactic acid, thereby reducing costs and accelerating the biodegradation rate.

[0037] The present invention is not limited to the above-described embodiment, but can be embodied in various forms.

[0038] For example, in the above embodiment, the pulp fibers 2, polylactic acid powder 3, and dispersant are mixed in the liquid 4, but as shown in Fig. 2, the liquid 4 containing the pulp fibers 2 may be leveled on a flat surface, and the polylactic acid powder 3 may be sprayed from the surface with a sprayer 8. In addition, if the polylactic acid powder 3 is sprayed on the liquid 4 while it is leveled on a flat surface, there is a possibility that the polylactic acid powder 3 may aggregate in the liquid 4. In this case, the liquid 4 may be squeezed out with a roller 6, and then the polylactic acid powder 3 may be sprayed on the surface.

[0039] In addition, in the above embodiment, the case of producing a sheet-shaped waterproof paper body 1 has been described, but when producing a three-dimensional object such as a plate, the paper may be placed in a formwork with a certain amount of liquid 4 squeezed out, and the polylactic acid powder 3 in the pulp fibers 2 may be heated and melted in that state to maintain the shape.

[0040] Furthermore, in the above embodiment, a method of mixing polylactic acid powder 3 with a dispersant or a method of spraying polylactic acid powder 3 from above is used, but in addition to these, polylactic acid may be dispersed in liquid 4 and the liquid 4 may be sprayed from above the pulp fibers 2 using a sprayer 8.

[0041] Furthermore, when the polylactic acid powder 3 is sprayed from above in this manner, there is a possibility that the polylactic acid powder 3 will not penetrate into the interior of the pulp fibers 2, so a method of penetrating the polylactic acid powder 3 by vibration or the like may be used, or a method of first applying a layer of polylactic acid powder 3 having a low specific gravity to the bottom layer, and then placing a liquid 4 containing pulp fibers 2 on top of that, and penetrating the polylactic acid powder 3 into the interior by vibration or the like may be used. [Explanation of symbols]

[0042] 1. Water-resistant paper 2. Pulp fiber 3. Polylactic acid powder 4...Liquid 5. Mixer 6. Roller 7...Heating device 8...Sprayer

Claims

1. A step of mixing pulp fibers and a powder of a biodegradable resin; mixing the pulp fibers with a biodegradable resin and then heating and melting the biodegradable resin; A method for manufacturing a waterproof paper body comprising the steps of:

2. A step of mixing pulp fibers, a powder of a biodegradable resin, and a dispersant into a liquid; Dispersing the pulp fiber and biodegradable resin powder using an agitator; forming the liquid in which the pulp fibers and the biodegradable resin powder are dispersed into a flat surface, and then squeezing out the liquid; After removing the liquid, the powder of the biodegradable resin is heated and melted; A method for manufacturing a waterproof paper body, comprising the steps of:

3. forming the liquid containing the pulp fibers into a planar shape; A step of spraying a biodegradable resin powder or a liquid containing a biodegradable resin powder onto the planar pulp fibers; A step of spraying the powder of the biodegradable resin and then squeezing out the liquid; After removing the liquid, the powder of the biodegradable resin is heated and melted; A method for manufacturing a waterproof paper body, comprising the steps of:

4. 3. The method for producing a waterproof paper body according to claim 1 or 2, wherein the average particle diameter of the powder of the biodegradable resin is within a range of 5 μm to 50 μm.

5. 3. A method for manufacturing a waterproof paper body according to claim 1 or 2, in which a powder of a biodegradable resin is mixed with the pulp fibers in an amount ranging from 5 to 15 weight percent.

6. The method for producing a waterproof paper body according to claim 1 or 2 further comprises coating the paper body with a powder of foamed polylactic acid.

7. A pulp layer composed of pulp fibers; a biodegradable resin melted within the pulp layer; A waterproof paper body comprising:

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