BUFFER MATERIAL

A buffer material of the present disclosure is a material including cellulose fibers and a binding material that binds the cellulose fibers, in which the binding material is a natural component and a proportion of the binding material in the buffer material is 10.0% by mass or greater and 30.0% by mass or less. It is preferable that the buffer material of the present disclosure have a thickness of 1.0 mm or greater and 100 mm or less and that the buffer material have a density of 0.02 g/cm3 or greater and 0.20 g/cm3 or less. It is preferable that the binding material contain a shellac resin. It is preferable that a content of lignin in the cellulose fibers be 5.0% by mass or less.

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Description

The present application is based on, and claims priority from JP Application Serial Number 2021-124154, filed Jul. 29, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a buffer material.

2. Related Art

In recent years, there has been a demand for a buffer material with a low environmental load in place of plastic materials. In the related art, a processing method of reusing used paper has been known. For example, JP-A-9-296398 suggests a processing method of crushing used paper into fibers and molding the fibers using polypropylene or a vinyl acetate emulsion as a solidifying material. Further, JP-A-2002-172728 suggests a method of coating one surface or both surfaces of a paper base material with a shellac resin which is a biologically produced natural resin obtained by purifying an acid ester resinous substance secreted by scale insects, to process a packaging material.

However, in the processing method disclosed in JP-A-9-296398, since the solidifying material is not a naturally derived material, reduction in environmental load is insufficient. In the processing method disclosed in JP-A-2002-172728, the water resistance and the oil resistance are improved by dissolving the shellac resin in water, alcohol, or the like and coating the paper base material with the mixture, but the strength of the packing material is not described. Therefore, a buffer material with a further reduced environmental load and satisfactory strength is required.

SUMMARY

The present disclosure has been made to solve the above-described problems and can be realized as the following aspect.

According to an aspect of the present disclosure, there is provided a buffer material including cellulose fibers, and a binding material that binds the cellulose fibers, in which the binding material is a natural component and a proportion of the binding material in the buffer material is 10.0% by mass or greater and 30.0% by mass or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing an example of a production device capable of producing a sheet-like buffer material.

FIG. 2A is a view showing an example of the shape of a molding die used for producing a buffer material.

FIG. 2B is a view showing an example of the shape of a molding die used for producing a buffer material.

FIG. 2C is a view showing an example of the shape of a molding die used for producing a buffer material.

FIG. 2D is a view showing an example of the shape of a molding die used for producing a buffer material.

FIG. 3 shows stress/strain curves of Examples 1 to 4.

FIG. 4 shows stress/strain curves of Examples 5 to 8.

FIG. 5 shows buffer coefficients/strain curves of Examples 1 to 4.

FIG. 6 shows buffer coefficients/strain curves of Examples 5 to 8.

 DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will be described in detail.

Examples of the present disclosure will be described in the embodiments described below. The present disclosure is not limited to the following embodiments and include various modifications within a range not departing from the scope of the present disclosure. Further, configurations described below may not all necessarily be essential configurations. 1. Buffer material

First, a buffer material will be described.

The buffer material of the present embodiment contains a plurality of cellulose fibers and a binding material that binds the cellulose fibers. Further, the binding material is a natural component and the proportion of the binding material in the buffer material is 10.0% by mass or greater and 30.0% by mass or less.

With such a configuration, a buffer material with a reduced environmental load and satisfactory strength can be provided.

Meanwhile, when the content of the binding material which is a natural component in the buffer material is less than the lower limit described above, the adhesive force of the cellulose fibers cannot be sufficiently increased, and thus the strength of the buffer material cannot be sufficiently increased. Further, the moldability of the buffer material is significantly deteriorated, and as a result, the production of the buffer material becomes difficult.

Further, when the content of the binding material which is a natural component in the buffer material is greater than the upper limit described above, the buffer effect of the buffer material cannot be sufficiently increased. Further, cracks and the like are likely to occur, and thus the strength is significantly decreased. Further, the moldability of the buffer material is significantly deteriorated, and as a result, the production of the buffer material becomes difficult.

1-1. Cellulose Fibers

The buffer material of the present embodiment contains a plurality of cellulose fibers.

The cellulose fibers are an abundant material derived from a plant, and it is preferable that the cellulose fibers be used as fibers from the viewpoints of suitably dealing with the environmental problems, saving reserve resources, stably supplying the buffer material, reducing the cost, and the like. Further, the cellulose fibers have a particularly high theoretical strength among various fibers and are also advantageous from the viewpoint of improving the strength of the buffer material.

Typically, cellulose fibers are mainly formed of cellulose, but may contain components other than cellulose. Examples of such components include hemicelluloses and lignin.

Here, the content of lignin in the cellulose fibers is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and still more preferably 1.0% by mass or less.

In this manner, buffering performance, particularly compression characteristics, of the buffer material is further improved.

The content of the cellulose in the cellulose fibers is preferably 50.0% by mass or greater, more preferably 60.0% by mass or greater, and still more preferably 80.0% by mass or greater.

For example, fibers which have been subjected to a bleaching treatment or the like may be used as the cellulose fibers. Further, the cellulose fibers may have been subjected to a treatment such as an ultraviolet irradiation treatment, an ozone treatment, or a plasma treatment.

As the cellulose fibers, chemical cellulose fibers such as organic cellulose fibers, inorganic cellulose fibers, and organic-inorganic composite cellulose fibers may be used in addition to the natural cellulose fibers such as animal cellulose fibers and plant cellulose fibers. More specifically, examples of the cellulose fibers include cellulose fibers consisting of cellulose, cotton, cannabis, kenaf, linen, ramie, jute, manila hemp, sisal hemp, conifer, and hardwood. These cellulose fibers may be used alone or in the form of a mixture as appropriate, or may be used as regenerated cellulose fibers which have been purified or the like. Further, the cellulose fibers may be subjected to various surface treatments.

The average length of the cellulose fibers is not particularly limited, but is preferably 10 μm or greater and 50 mm or less, more preferably 20 μm or greater and 5.0 or less, and still more preferably 30 μm or greater and 3.0 or less in terms of the length-weighted average cellulose fiber length.

In this manner, the stability of the shape of the buffer material, the strength of the buffer material, and the like can be further improved. Further, the buffering performance of the buffer material can be further improved.

When the cellulose fibers contained in the buffer material of the present embodiment are considered to be one independent cellulose fiber, the average thickness thereof is preferably 1.0 μm or greater and 1000 μm or less and more preferably 2.0 μm or greater and 100.0 μm or less.

In this manner, the stability of the shape of the buffering material, the strength of the buffer material, and the like can be further improved. Further, the buffering performance of the buffer material can be further improved. Further, it is possible to more effectively prevent the surface of the buffer material from being unexpectedly uneven.

Further, when a cross section of the cellulose fiber is not circular, a circle having the same area as the area of the cross section is assumed, and the diameter of the circle is used as the thickness of the cellulose fiber.

The average aspect ratio of the cellulose fibers, that is, the average length with respect to the average thickness is not particularly limited, but is preferably 10 or greater and 1000 or less and more preferably 15 or greater and 500 or less.

In this manner, the stability of the shape of the buffering material, the strength of the buffer material, and the like can be further improved. Further, the buffering performance of the buffer material can be further improved. Further, it is possible to more effectively prevent the surface of the buffer material from being unexpectedly uneven.

In the present specification, the term “cellulose fibers” denote a single cellulose fiber or an aggregate of a plurality of cellulose fibers. Further, the cellulose fibers may be cellulose fibers loosened into fibers by performing a defibration treatment on a material to be defibrated, that is, a defibrated material. Examples of the material to be defibrated here include cellulose fibers obtained by being entangled or bound, such as pulp sheets, paper, used paper, tissue paper, kitchen paper, cleaners, filters, liquid absorbing materials, sound absorbing bodies, buffer materials, mats, and corrugated cardboard.

The content of the cellulose fibers in the buffer material is preferably 63.0% by mass or greater and 90.0% by mass or less, more preferably 67.0% by mass or greater and 88.0% by mass or less, and still more preferably 72.0% by mass or greater and 86.0% by mass or less.

In this manner, the strength and the buffering performance of the buffer material can be further improved.

1-2. Binding Material

The buffer material of the present embodiment contains a binding material which is a natural component. Hereinafter, the binding material which is a natural component will also be referred to as “natural binding material”.

The binding material has a function of binding a cellulose fiber to a cellulose fiber and may further have other functions. More specifically, the binding material may have a function of suppressing a component other than the cellulose fibers, for example, a colorant or the like described below from falling off from the buffer material. Further, a part of the natural binding material contained in the buffer material may be contained in a form in which the above-described function is not exhibited.

It is preferable that the natural binding material have thermal plasticity.

In this manner, the natural binding material is melted or softened by applying heat in the process of producing the buffer material to spread between cellulose fibers, and thus the cellulose fibers are likely to be bound to each other.

The natural binding material is melted or softened preferably at 200° C. or lower and more preferably at 160° C. or lower.

In this manner, the cellulose fibers can be more suitably bound to each other by carrying out a heat treatment at a relatively low temperature, which is more preferable from the viewpoint of energy saving.

The glass transition temperature of the natural binding material is preferably 45° C. or higher and 95° C. or lower and more preferably 50° C. or higher and 90° C. or lower.

In this manner, the cellulose fibers can be more suitably bound to each other by carrying out a heat treatment at a relatively low temperature, which is more preferable from the viewpoint of energy saving. Further, for example, it is possible to effectively prevent the natural binding material from being unexpectedly softened when the buffer material stands in a high temperature environment.

Examples of the natural binding material include natural resins such as rosin, dammar, mastic, copal, amber, a shellac resin, dragon tree, sandarac, and colophonium, starch as a natural polymer, and modified products thereof, and one or two or more selected from among these can be used in combination, but it is preferable that the natural binding material contain a shellac resin.

In this manner, the strength and the buffering performance of the buffer material can be further improved, and the workability of the buffer material can also be further improved.

The proportion of the shellac resin in the entire natural binding material of the buffer material is preferably 50.0% by mass or greater, more preferably 70.0% by mass or greater, and still more preferably 90.0% by mass or greater.

In this manner, the above-described effects are more significantly exhibited.

The starch is a polymer material obtained by polymerizing a plurality of α-glucose molecules with glycoside bonds. The starch may be linear or branched.

For example, starch derived from various plants can be used as the starch. Examples of raw materials of starch include cereals such as corn, wheat, and rice, beans such as broad beans, mung beans, and adzuki beans, tubers such as potatoes, sweet potatoes, and tapioca, wild grasses such as dogtooth violet, bracken, and kadzu, and palms such as sago palm.

For example, processed starch or modified starch may be used as the starch. Examples of the processed starch include acetylated adipic acid crosslinked starch, acetylated starch, oxidized starch, sodium octenyl succinate starch, hydroxypropyl starch, hydroxypropylated phosphoric acid crosslinked starch, phosphorylated starch, phosphoric acid monoesterified phosphoric acid crosslinked starch, urea phosphorylated esterified starch, sodium starch glycolate, and high amylose cornstarch. Further, examples of the modified starch include pregelatinized starch, dextrin, laurylpolyglucose, cationized starch, thermoplastic starch, and carbomic acid starch.

The content of the natural binding material in the buffer material may be 10.0% by mass or greater and 30.0% by mass or less, and is preferably 12.0% by mass or greater and 28.0% by mass or less, more preferably 14.0% by mass or greater and 25.0% by mass or less, and still more preferably 15.0% by mass or greater and 22.0% by mass or less.

In this manner, the above-described effects are more significantly exhibited.

1-3. Other Components

The buffer material of the present embodiment is not limited as long as the buffer material contains the cellulose fibers and the natural binding material, but may further contain other components in addition the above-described components. Hereinafter, such components will also be referred to as “other components”.

Examples of other components include a flame retardant, a colorant, an aggregation inhibitor, a surfactant, a fungicide, a preservative, an antioxidant, an ultraviolet absorbing agent, and an oxygen absorbing agent.

Further, the buffer material of the present embodiment may contain, as other components, binding materials other than the natural binding material.

Various synthetic resins such as thermoplastic resins, thermosetting resins, and photocurable resins can be used as the binding materials other than the natural binding material.

Examples of the thermoplastic resins among the synthetic resins include an AS resin, an ABS resin, polypropylene, polyethylene, polyvinyl chloride, polystyrene, an acrylic resin, a polyester resin, polyethylene terephthalate, polyphenylene ether, polybutylene terephthalate, nylon, polyamide, polycarbonate, polyacetal, polyphenylene sulfide, and polyether ether ketone.

Among the synthetic resins, biodegradable resins such as polylactic acid, polybutylene succinate, and polyhydroxybutanoic acid may be used as the binding materials other than the natural binding material.

The environmental suitability of the buffer material can be further improved by using the biodegradable resins.

Further, the resins may be, for example, copolymerized or modified.

The content of other components in the buffer material is preferably 7.0% by mass or less, more preferably 5.0% by mass or less, and still more preferably 3.0% by mass or less.

Particularly when the buffer material contains binding materials other than the natural binding material, the content of the binding materials in the buffer material is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.1% by mass or less.

1-4. Properties and the Like of Buffer Material

The buffer material of the present embodiment may have any size and any shape. For example, the buffer material may have a sheet shape or a three-dimensional shape.

Further, the buffer material of the present embodiment may be, for example, processed into a predetermined three-dimensional shape by performing treatments, such as molding, cutting, bending, notching, organizing, and the like as necessary, on the sheet-like buffer material which has been prepared in advance, using a molding die.

As described above, when the buffer material has a three-dimensional shape and is produced from a sheet-like buffer material, the three-dimensional buffer material may be produced by superimposing a plurality of sheet-like buffer materials.

The thickness of the buffer material, that is, the thickness of a portion formed of the material containing cellulose fibers and the natural binding material is not particularly limited, but is preferably 1.0 mm or greater and 100 mm or less, more preferably 1.5 mm or greater and 30 mm or less, and still more preferably 2.0 mm or greater and 20 mm or less.

In this manner, the strength and the rigidity of the buffer material can be further improved. Further, for example, the workability when the sheet-like buffer material is processed into a buffer material having a three-dimensional shape by carrying out a process of deep drawing or the like can be further improved, and occurrence of wrinkles or breakage can be more effectively prevented.

The density of the buffer material is not particularly limited, but is preferably 0.02 g/cm3 or greater and 0.20 g/cm3 or less, more preferably 0.03 g/cm3 or greater and 0.15 g/cm3 or less, and still more preferably 0.05 g/cm3 or greater and 0.11 g/cm3 or less.

In this manner, the strength and the rigidity of the buffer material can be further improved. Further, the durability of the buffer material against an impact can be further improved. Further, for example, the workability when the sheet-like buffer material is processed into a buffer material having a three-dimensional shape by carrying out a process of deep drawing or the like can be further improved, and occurrence of wrinkles or breakage can be more effectively prevented.

Particularly when the buffer material satisfies the above-described conditions for the thickness and the above-described conditions for the density, the effects obtained by satisfying the conditions are synergistically enhanced so that the above-described effects are more significantly exhibited.

The basis weight of the buffer material is not particularly limited, but is preferably 100 g/m2 or greater and 600 g/m2 or less, more preferably 150 g/m2 or greater and 500 g/m2 or less, and still more preferably 150 g/m2 or greater and 400 g/m2 or less.

In this manner, the strength and the rigidity of the buffer material can be further improved. Further, the durability of the buffer material against an impact can be further improved. Further, for example, the workability when the sheet-like buffer material is processed into a buffer material having a three-dimensional shape by carrying out a process of deep drawing or the like can be further improved, and occurrence of wrinkles or breakage can be more effectively prevented.

The BET specific surface area of the buffer material is not particularly limited, but is preferably 0.30 m2/g or greater and 0.50 m2/g or less, more preferably 0.33 m2/g or greater and 0.47 m2/g or less, and still more preferably 0.35 m2/g or greater and 0.45 m2/g or less.

The BET specific surface area thereof decreases as the amount of the binding material such as a shellac resin to adhere to the surface of the fiber increases. The strength of the fibers increases as the adhesion amount increases, and thus effects that make the buffer material preferable can be obtained.

Further, the buffer material of the present embodiment may have a portion formed of a material that does not satisfy the above-described conditions in addition to a portion formed of a material that satisfies the above-described conditions. In this case, examples of the portion formed of a material that does not satisfy the above-described conditions include a core material and a coating layer. Here, the proportion of the material that satisfies the above-described conditions in the entire buffer material is preferably 50% by volume or greater, more preferably 80% by volume or greater, and still more preferably 90% by volume or greater. 2. Method of producing buffer material

Next, a method of producing the buffer material will be described.

The method of producing the buffer material of the present embodiment includes a heating and pressing step of heating and pressing a composition for producing a buffer material which is a composition containing the cellulose fibers and the natural binding material. Further, the proportion of the natural binding material in the total solid content constituting the composition for producing a buffer material is 10.0% by mass or greater and 30.0% by mass or less.

In this manner, the buffer material as described above, that is, the buffer material with a reduced environmental load and satisfactory strength can be suitably produced.

2-1. Composition for Producing Buffer Material

First, the composition for producing the buffer material used in the method of producing the buffer material of the present embodiment will be described.

2-1-1. Cellulose Fibers

The composition for producing the buffer material of the present embodiment contains a plurality of cellulose fibers.

The cellulose fibers described in the section 1-1 can be used as the cellulose fibers contained in the composition for producing the buffer material.

In this manner, the same effects as described above can be obtained.

The proportion of the cellulose fibers in the total solid content constituting the composition for producing the buffer material is preferably 63.0% by mass or greater and 90.0% by mass or less, more preferably 67.0% by mass or greater and 88.0% by mass or less, and still more preferably 72.0% by mass or greater and 86.0% by mass or less.

In this manner, the strength and the buffering performance of the buffer material to be produced can be further improved.

2-1-2. Natural Binding Material

The composition for producing the buffer material of the present embodiment contains a natural binding material.

The natural binding material described in the section 1-2 can be used as the natural binding material contained in the composition for producing the buffer material.

In this manner, the same effects as described above can be obtained.

When the composition for producing the buffer material contains the natural binding material in the form of particles, it is preferable that the volume average particle diameter of the natural binding material be less than the thickness of the cellulose fibers.

In this manner, the natural binding material and the cellulose fibers are more likely to be uniformly mixed with each other, and thus it is possible to more effectively prevent the composition of the buffer material from being unexpectedly uneven.

The volume average particle diameter of the natural binding material is preferably 0.8 μm or greater and 100 μm or less and more preferably 1.5 μm or greater and 50 μm or less.

The particulate natural binding material can be obtained by being kneaded using, for example, a kneader, a Banbury mixer, a single-screw extruder, a multi-screw extruder, a twin roll, a triple roll, a continuous kneader, or a continuous twin roll, pelletized by an appropriate method, and crushed. The natural binding material contains various sizes of particles in some cases and may be classified using a known classification device. Further, the outer shape of the particles of the natural binding material is not particularly limited, and the particles may be spherical, disc-like, fibrous, or amorphous.

In the present embodiment, the proportion of the natural binding material in the total solid content constituting the composition for producing a buffer material may be 10.0% by mass or greater and 30.0% by mass or less, and is preferably 12.0% by mass or greater and 28.0% by mass or less, more preferably 14.0% by mass or greater and 25.0% by mass or less, and still more preferably 15.0% by mass or greater and 22.0% by mass or less.

In this manner, the above-described effects are more significantly exhibited.

The composition for producing a buffer material may contain the natural binding material in any state. For example, the natural binding material may be contained in a state of being dissolved in another component or the like, but it is preferable that the natural binding material be contained in a state of being dispersed in another component, particularly in a state of being dispersed as powder.

In this manner, voids can be suitably formed in the buffer material to be produced, and thus the buffering performance of the buffer material can be more reliably improved.

2-1-3. Liquid Component

The composition for producing a buffer material of the present embodiment may contain, for example, a liquid component.

When the composition contains a liquid component, for example, the cellulose fibers can enter a suitably loose state in the composition for producing a buffer material or unexpected uneven distribution or the like of each component in the composition for producing a buffer material can be suitably prevented.

When the composition for producing a buffer material contains a liquid component, the natural binding material may be contained in a state of being dissolved in the liquid component or in a state of being dispersed in the liquid component.

Examples of the liquid component include various organic solvents such as water, an alcohol-based solvent such as methanol, ethanol, ethylene glycol, or glycerin, and a ketone-based solvent such as acetone or methyl ethyl ketone, and one or two or more selected from among these can be used in combination.

When the composition for producing a buffer material contains a liquid component, the content of the liquid component in the composition for producing a buffer material can be set to, for example, 10.0% by mass or greater and 70.0% by mass or less.

2-1-4. Other Components

The composition for producing a buffer material of the present embodiment may contain other components in addition to the above-described components. The other components described in the section 1-3 can be used as such components.

The proportion of the other components in the total solid content constituting the composition for producing a buffer material is preferably 7.0% by mass or less, more preferably 5.0% by mass or less, and still more preferably 3.0% by mass or less.

Particularly when the composition for producing a buffer material contains a binding material other than the natural binding material, the proportion of the binding material in the total solid content constituting the composition for producing a buffer material is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.1% by mass or less.

2-1-5. Properties of Composition for Producing Buffer Material

The composition for producing a buffer material may be in any form of powder, a dispersion liquid, a web, or the like.

2-1-6. Preparation of Composition for Producing Buffer Material

The composition for producing a buffer material can be prepared, for example, by mixing constituent components constituting the composition for producing a buffer material.

More specifically, the composition for producing a buffer material can be prepared, for example, by stirring and mixing defibrated cellulose fibers and the powdery natural binding material. In such a case, for example, the composition for producing a buffer material can be suitably prepared by using a device described below.

2-2. Heating and Pressing Step

In the heating and pressing step, the composition for producing a buffer material is heated and pressed.

The present step can be performed by a heat press, a heat roller, a three-dimensional molding machine, or the like.

The heating temperature in the present step is preferably 160° C. or higher, more preferably 165° C. or higher and 250° C. or lower, and still more preferably 170° C. or higher and 220° C. or lower.

In this manner, the natural binding material can efficiently form binding of the cellulose fibers while unexpected modification, deterioration, or the like of the constituent components constituting the buffer material is effectively prevented, the productivity of the buffer material can be further improved, and the strength, the buffering performance, and the like of the buffer material can be further improved. Further, it is also preferable that the heating temperature be in the above-described ranges even from the viewpoint of energy saving.

The pressing pressure in the present step is preferably 0.50 MPa or less, more preferably 0.01 MPa or greater and 0.45 MPa or less, and still more preferably 0.05 MPa or greater and 0.40 MPa or less.

In this manner, the natural binding material can efficiently form binding of the cellulose fibers while the buffer material to be produced is allowed to have a moderate amount of voids, and thus the strength, the buffering performance, and the like of the buffer material can be further improved. Further, it is also preferable that the pressing pressure be in the above-described ranges even from the viewpoint of energy saving.

The heating and pressing time in the present step is preferably 1 second or longer and 300 seconds or shorter, more preferably 10 seconds or longer and 60 seconds or shorter, and still more preferably 15 seconds or longer and 45 seconds or shorter.

In this manner, the productivity of the buffer material can be further improved, and the strength, the buffering performance, and the like of the buffer material can be further improved. It is also preferable that the heating and pressing time be in the above-described ranges even from the viewpoint of energy saving.

2-3. Other Steps

The method of producing a buffer material may further include other steps in addition to the above-described heating and pressing step. Examples of such steps include a cutting step of cutting the produced buffer material into an appropriate size and an appropriate shape.

2-4. Production Device

Next, a production device that can be used for producing the sheet-like buffer material will be described.

FIG. 1 is a view schematically illustrating an example of a production device capable of producing the sheet-like buffer material. FIGS. 2A to 2D each show an example of the shape of a molding die used for production of the buffer material.

As illustrated in FIG. 1, a production device 100 includes a supply unit 10, a crushing unit 12, a defibrating unit 20, a sorting unit 40, a first web forming unit 45, a rotating body 49, a mixing unit 50, an accumulating unit 60, a second web forming unit 70, a buffer material forming unit 80, a cutting unit 90, and a humidifying unit 78.

The supply unit 10 supplies the raw material to the crushing unit 12. The supply unit 10 is an automatic charging unit for continuously charging the crushing unit 12 with the raw material. The raw material to be supplied to the crushing unit 12 may contain the cellulose fibers.

The crushing unit 12 cuts the raw material supplied by the supply unit 10 in the atmosphere, for example, in the air to form small pieces. As the shape and the size of the small pieces, small pieces with a size of several cm square may be exemplified. In the example shown in the figure, the crushing unit 12 includes crushing blades 14, and the raw material charging the crushing unit 12 can be cut by the crushing blades 14. For example, a shredder is used as the crushing unit 12. The raw material cut by the crushing unit 12 is received by a hopper 1 and transported to the defibrating unit 20 through a pipe 2.

The defibrating unit 20 defibrates the raw material cut by the crushing unit 12. Here, the term “defibrate” denotes that the raw material formed by binding a plurality of cellulose fibers, that is, a material to be defibrated is loosened into individual cellulose fibers. The defibrating unit 20 also has a function of separating substances, such as resin particles, an ink, a toner, a filler, and a bleeding inhibitor, adhering to the raw material from the cellulose fibers.

The material after passing through the defibrating unit 20 is referred to as “defibrated material”. In some cases, “defibrated material” contains, in addition to the loosened cellulose fibers, resin particles, a coloring agent such as an ink, a toner, or a filler, and an additive such as a bleeding inhibitor or a paper strength enhancer which have been separated from the cellulose fibers during loosening of the cellulose fibers. Examples of the resin particles separated from the cellulose fibers include particles containing a resin for binding a plurality of cellulose fibers.

The defibrating unit 20 performs dry type defibration. A treatment of performing defibration or the like in the atmosphere, for example, in the air without performing wet type defibration of dissolving a material in a liquid such as water in a slurry form is referred to as dry type defibration. In the present embodiment, an impeller mill is used as the defibrating unit 20. The defibrating unit 20 has a function of generating an air flow that sucks the raw material and discharges the defibrated material. In this manner, the defibrating unit 20 can suck the raw material from an introduction port 22 together with the air flow, perform the defibration treatment, and transport the defibrated material to a discharge port 24 by the air flow generated by itself. The defibrated material that has passed through the defibrating unit 20 is transferred to the sorting unit 40 through the pipe 3. Further, as the air flow for transporting the defibrated material to the sorting unit 40 from the defibrating unit 20, the air flow generated by the defibrating unit 20 may be used or an airflow generating device such as a blower is provided and an air flow generated by the device may be used.

The sorting unit 40 introduces the defibrated material defibrated by the defibrating unit 20 from the introduction port 42 and sorts out the defibrated material according to the length of the cellulose fibers. The sorting unit 40 includes a drum portion 41 and a housing unit 43 that accommodates the drum portion 41. For example, a sieve is used as the drum portion 41. The drum portion 41 has a net and can divide the defibrated material into a first sorted material that is cellulose fibers or particles having a size smaller than the size of the mesh of the net and thus passing through the net and a second sorted material that is cellulose fibers, undefibrated pieces, or lumps having a size greater than the size of the mesh of the net and thus not passing through the net. For example, the first sorted material is transferred to the mixing unit 50 through the pipe 7. The second sorted material is returned to the defibrating unit 20 from a discharge port 44 through a pipe 8. Specifically, the drum portion 41 is a cylindrical sieve rotationally driven by a motor. As the net of the drum portion 41, for example, a wire net, an expanded metal obtained by expanding a metal plate with cuts, or a punchinig metal in which holes are formed in a metal plate with a press machine or the like is used.

The first web forming unit 45 transports the first sorted material having passed through the sorting unit 40 to the mixing unit 50. The first web forming unit 45 includes a mesh belt 46, a stretching roller 47, and a suction unit 48.

The suction unit 48 can suck the first sorted material having passed through the opening of the sorting unit 40, that is, the opening of the net and dispersed in the air, onto the mesh belt 46. The first sorted material is accumulated on the moving mesh belt 46 to form a web V. The basic configurations of the mesh belt 46, the stretching roller 47, and the suction unit 48 are the same as the configurations of a mesh belt 72, a stretching roller 74, and a suction mechanism 76 of the second web forming unit 70 described below.

The web V passes through the sorting unit 40 and the first web forming unit 45 and is thus formed in a soft and inflated state due to containing a large amount of air. The pipe 7 is charged with the web V accumulated on the mesh belt 46, and the web V is transported to the mixing unit 50.

The rotating body 49 can cut the web V before the web V is transported to the mixing unit 50. In the example shown in the figure, the rotating body 49 includes a base portion 49a and protrusions 49b protruding from the base portion 49a. The protrusions 49b have, for example, a plate shape. In the example shown in the figure, four protrusions 49b are provided and the four protrusions 49b are provided at equal intervals. Since the base portion 49a rotates in a direction R, the protrusions 49b can rotate using the base portion 49a as an axis. Since the web V is cut by the rotating body 49, for example, a fluctuation in amount of the defibrated material supplied to the accumulating unit 60 per unit time can be reduced.

The rotating body 49 is provided in the vicinity of the first web forming unit 45. In the example shown in the figure, the rotating body 49 is provided in the vicinity of the stretching roller 47a positioned on the downstream in the path of the web V, that is, next to the stretching roller 47a. The rotating body 49 is provided at a position where the protrusions 49b can come into contact with the web V and does not come into contact with the mesh belt 46 on which the web V is accumulated. The shortest distance between the protrusions 49b and the mesh belt 46 is, for example, 0.05 mm or greater and 0.5 mm or less.

The mixing unit 50 mixes the first sorted material having passed through the sorting unit 40, that is, the first sorted material transported by the first web forming unit 45 with an additive containing the natural binding material. The mixing unit 50 includes an additive supply unit 52 that supplies the additive, a pipe 54 that transports the first sorted material and the additive, and a blower 56. In the example shown in the figure, the additive is supplied to the pipe 54 through the hopper 9 from the additive supply unit 52. The pipe 54 is connected to the pipe 7.

The mixing unit 50 allows the blower 56 to generate an air flow so that the first sorted material and the additive can be transported while being mixed with each other in the pipe 54. Further, the mechanism of mixing the first sorted material and the additive is not particularly limited, and the first sorted material and the additive may be mixed by being stirred using a blade rotating at a high speed or may be mixed by using rotation of a container as in a case of a V type mixer.

A screw feeder as shown in FIG. 1 or a disc feeder which is not shown in the figure is used as the additive supply unit 52. The additive supplied from the additive supply unit 52 contains the above-described natural binding material. The plurality of cellulose fibers have not been bound at the time point when the natural binding material is supplied. The natural binding material is partially melted while passing through the buffer material forming unit 80 so that the plurality of cellulose fibers in the surface region of the buffer material WS are bound.

Further, the additive to be supplied from the additive supply unit 52 may contain, in addition to the natural binding material, a colorant for coloring the cellulose fibers, an aggregation inhibitor for suppressing aggregation of the cellulose fibers or aggregation of the natural binding material, and a flame retardant for making the cellulose fibers and the like difficult to burn, depending on the type of the buffer material WS to be produced. The composition for producing a buffer material which is the mixture having passed through the mixing unit 50, that is, the mixture of the first sorted material and the additive is transferred to the accumulating unit 60 through the pipe 54.

The accumulating unit 60 introduces the mixture having passed through the mixing unit 50 from the introduction port 62, loosens the defibrated material of the entangled cellulose fibers, and drops the mixture while dispersing the mixture in the air. In this manner, the accumulating unit 60 can uniformly accumulate the mixture on the second web forming unit 70.

The accumulating unit 60 includes a drum portion 61 and a housing unit 63 that accommodates the drum portion 61. A cylindrical rotating sieve is used as the drum portion 61. The drum portion 61 has a net and drops the cellulose fibers or particles which are contained in the mixture having passed through the mixing unit 50 and have a size smaller than the size of the mesh of the net. The configuration of the drum portion 61 is the same as the configuration of the drum portion 41.

Further, “sieve” of the drum portion 61 may not have a function of sorting out a specific object. That is, “sieve” used as the drum portion 61 denotes a portion provided with a net, and the drum portion 61 may drop the entire mixture introduced to the drum portion 61.

The second web forming unit 70 accumulates the material having passed through the accumulating unit 60 to form a web W which is an accumulated material serving as the buffer material WS. Here, a molding die which is not shown in FIG. 1 is placed on the mesh belt 72 to be used as a saucer so that a web can be formed in the molding die. The second web forming unit 70 includes the mesh belt 72, the stretching roller 74, and the suction mechanism 76.

Any of the molding dies having shapes shown in FIGS. 2A, 2B, 2C, and 2D can be used as the molding die. When the buffer material WS has a three-dimensional shape having a projection, such as a bombshell shape, a hemispherical shape, a laterally-long elliptical shape, a speaker shape, a cylindrical shape, a conical shape, or step-like conical shape, since the buffer material is capable of more suitably withstanding an impact, the shape thereof can be optionally changed.

The mesh belt 72 accumulates the material having passed through the opening of the accumulating unit 60, that is, the opening of the net on the molding die while moving. The mesh belt 72 and the molding die are configured to be stretched by the stretching roller 74 and circulate the air to make the material having passed through the accumulating unit difficult to pass through. The mesh belt 72 moves by rotation of the stretching roller 74. The mesh belt 72 continuously drops and accumulates the material having passed through the accumulating unit 60 while continuously moving, and thus the web W is formed on the molding die provided on the mesh belt 72. The mesh belt 72 and the molding die are made of, for example, a metal, a resin, cloth, or nonwoven fabric.

The suction mechanism 76 is provided below the mesh belt 72, that is, on a side opposite to the side of the accumulating unit 60. The suction mechanism 76 can generate an air flow flowing downward, that is, an air flow flowing to the mesh belt 72 from the accumulating unit 60. The mixture dispersed in the air by the accumulating unit 60 can be sucked onto the mesh belt 72 by the suction mechanism 76. In this manner, the discharge rate of the material from the accumulating unit 60 can be increased. Further, the suction mechanism 76 can form a downflow in the path where the mixture falls, and thus it is possible to suppress the defibrated material and the additive from being entangled with each other during the fall.

As described above, the web W is formed in a soft and inflated state due to containing a large amount of air by carrying out the web forming step performed by the accumulating unit 60 and the second web forming unit 70. The web W accumulated on the molding die provided on the mesh belt 72 is transported to the buffer material forming unit 80.

The thickness of the web W which is the accumulated material to be transported to the buffer material forming unit 80 is preferably 2.0 mm or greater and 150 mm or less, more preferably 3.0 mm or greater and 120 mm or less, and still more preferably 5.0 mm or greater and 100 mm or less.

Further, the density of the web W is preferably 0.01 g/cm3 or greater and 0.05 g/cm3 or less and more preferably 0.02 g/cm3 or greater and 0.04 g/cm3 or less.

Further, the basis weight of the web W is preferably 20 g/m2 or greater and 7500 g/m2 or less, more preferably 30 g/m2 or greater and 6000 g/m2 or less, and still more preferably 50 g/m2 or greater and 5000 g/m2 or less.

The buffer material forming unit 80 forms the buffer material WS by heating the web W accumulated on the molding die provided on the mesh belt 72. The buffer material forming unit 80 heats the web W which is the accumulated material of the mixture of the defibrated material and the additive mixed in the second web forming unit 70, and thus the natural binding material is softened and melted. In this manner, the plurality of cellulose fibers are bound to each other.

The buffer material forming unit 80 includes a heating unit 84 that heats the web W. For example, a heat press or a heating roller may be used as the heating unit 84, and an example of using a heating roller will be described below. The number of heating rollers in the heating unit 84 is not particularly limited. In the example shown in the figure, the heating unit 84 includes a pair of heating rollers 86. The buffer material WS can be molded while the web W is continuously transported by configuring the heating unit 84 as the heating rollers 86.

The heating rollers 86 are disposed such that the rotation axes thereof are in parallel with each other. The roller radius of the heating roller 86 is preferably 2.0 cm or greater and 5.0 cm or less, more preferably 2.5 cm or greater and 4.0 cm or less, and still more preferably 2.5 cm or greater and 3.5 cm or less.

The heating rollers 86 come into contact with the web W and heat the web W while transporting the web W in a state of interposing the web W.

The rotation speed of the heating rollers 86 is, for example, preferably 20 rpm or greater and 500 rpm or less, more preferably 30 rpm or greater and 350 rpm or less, and still more preferably 50 rpm or greater and 300 rpm or less.

In this manner, the surface region of the web W can be sufficiently heated with high accuracy.

The heating rollers 86 transport the web W in a state of interposing the web W to form the buffer material WS having a predetermined thickness.

Here, the pressure applied to the web W by the heating rollers 86 is preferably 0.50 MPa or less, more preferably 0.01 MPa or greater and 0.45 MPa or less, and still more preferably 0.05 MPa or greater and 0.40 MPa or less.

The surface temperature of the heating rollers 86 when heating the web W is preferably 160° C. or higher, more preferably 165° C. or higher and 250° C. or lower, and still more preferably 170° C. or higher and 220° C. or lower.

It is preferable that the gap between the pair of heating rollers 86 of the heating unit 84 be adjusted such that the thickness, the density, and the basis weight of the buffer material WS satisfy the conditions described in the section 1-4.

The production device 100 of the present embodiment may include the cutting unit 90 as necessary. In the example shown in the figure, the cutting unit 90 is provided on the downstream of the heating unit 84. The cutting unit 90 cuts the molding die containing the buffer material WS molded by the buffer material forming unit 80. In the example shown in the figure, the cutting unit 90 includes a first cutting unit 92 cutting the molding die of the buffer material WS in a direction intersecting the transport direction of the buffer material WS and a second cutting unit 94 cutting the buffer material WS in a direction parallel to the transport direction. The second cutting unit 94 cuts, for example, the molding die containing the buffer material WS having passed through the first cutting unit 92.

Further, the production device 100 of the present embodiment may include the humidifying unit 78. In the example shown in the figure, the humidifying unit 78 is provided on the downstream of the cutting unit 90 and on the upstream of a discharge unit 96. The humidifying unit 78 is capable of applying water or water vapor to the buffer material WS. Specific examples of the aspect of the humidifying unit 78 include an aspect of spraying mist of water or an aqueous solution, an aspect of spraying water or an aqueous solution, and an aspect of jetting water or an aqueous solution from an ink jet head for adhesion.

Since the production device 100 includes the humidifying unit 78, the buffer material WS to be formed can be humidified. In this manner, the cellulose fibers are humidified and softened. Therefore, when a container or the like is three-dimensionally molded by using the buffer material WS, wrinkles or breakage is less likely to occur. Further, since a hydrogen bond is easily formed between cellulose fibers by humidifying the buffer material WS, the density of the buffer material WS is increased, and for example, the strength can be improved.

In the example of FIG. 1, the humidifying unit 78 is provided on the downstream of the cutting unit 90, and the same effects as described above can be obtained as long as the humidifying unit 78 is provided on the downstream of the heating unit 84. That is, the humidifying unit 78 may be provided on the downstream of the heating unit 84 and on the upstream of the cutting unit 90.

The buffer material WS is obtained, for example, as a three-dimensional molded body having a convex shape by demolding only the buffer material WS from the molding die where the buffer material WS has been molded.

Hereinbefore, the suitable embodiments of the present disclosure have been described, but the present disclosure is not limited thereto.

For example, the present disclosure has configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, the same methods, and the same results as described above or configurations with the same purposes and the same effects as described above. Further, the present disclosure has configurations in which parts that are not essential in the configurations described in the embodiments have been substituted. Further, the present disclosure has configurations exhibiting the same effects as the effects of the configurations described in the embodiments or configurations capable of achieving the same purposes as the purposes of the configurations described in the embodiments. Further, the present disclosure has configurations in which known techniques have been added to the configurations described in the embodiments.

For example, the buffer material of the present disclosure is not limited to the buffer material produced by the above-described method using the above-described production device.

More specifically, for example, the case where the buffer material is produced by using the composition for producing a buffer material that is the composition containing the cellulose fibers and the natural binding material has been described as a representative example in the above-described embodiments, but the buffer material may be produced by sprinkling the natural binding material on the cellulose fibers which have been prepared in advance and heating and pressing the cellulose fibers and the natural binding material.

EXAMPLES

Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

3. Production of Buffer Material Example 1

A buffer material was produced using corrugated cardboard (manufactured by Rengo Co., Ltd.) as a raw material that was a cellulose fiber source, using Chinese shellac resin powder having a softening point of 62° C., a curing point of 152° C., and a volume average particle diameter of 20 μm or less as a natural binding material, and using a production device for a buffer material with the configuration shown in FIG. 1. Here, a #3 type molding die with a plurality of hemispherical recesses arranged in a staggered manner and a #3 type molding die with a plurality of hemispherical projections corresponding to the recesses and arranged in a staggered manner were used. Further, the content of lignin in the cellulose fibers was 1.0% by mass or less. Further, the supply amount of the natural binding material was adjusted such that the blending ratio between the cellulose fibers and the natural binding material in the buffer material produced reached 70% by mass:30% by mass. In addition, the heating temperature, the pressing pressure, and the heating and pressing time in the buffer material forming unit were respectively adjusted to 170° C., 0.05 MPa, and 60 seconds.

The buffer material produced had a thickness of 3.5 mm, a density of 0.05 g/cm3, and a basis weight of 175 g/m2. Further, the cellulose fibers contained in the buffer material had an average thickness of 730 μm and an average thickness of 20 μm.

Examples 2 to 4

Each buffer material was produced in the same manner as in Example 1 except that the supply amount of the natural binding material was changed such that the blending ratio between the cellulose fibers and the natural binding material in the buffer material produced was set as listed in Table 1.

Examples 5 to 8

Each buffer material was produced in the same manner as in Example 1 except that the conditions for the buffer material forming unit were adjusted and the density of the buffer material was set as listed in Table 1. Comparative Example 1 and 2

Each buffer material was attempted to be produced in the same manner as in Example 1 except that the supply amount of the natural binding material was changed such that the blending ratio between the cellulose fibers and the natural binding material in the buffer material produced was set as listed in Table 1.

The configurations of the buffer materials in the examples and the comparative examples are collectively listed in Table 1.

TABLE 1 Conditions for Constituent component buffer material Cellulose fibers Shellac resin Density [% by mass] [% by mass] [g/cm3] Example 1 70 30 0.05 Example 2 80 20 0.05 Example 3 85 15 0.05 Example 4 90 10 0.05 Example 5 70 30 0.02 Example 6 70 30 0.10 Example 7 70 30 0.20 Example 8 70 30 0.30 Comparative 95 5 0.05 Example 1 Comparative 60 40 0.40 Example 2

4. Evaluation 4-1. Moldability

In each example and each comparative example, a case where a buffer material having a shape corresponding to the shape of the molding die was able to be produced was evaluated as “possible”, and a case where a buffer material having a shape corresponding to the shape of the molding die was not able to be produced was evaluated as “impossible”.

4-2. Stress/Strain Curve

The buffer material was compressed in the thickness direction, that is, the projection direction of a hemispherical projection using a universal test machine AG-IS (manufactured by Shimadzu Corporation), and a stress/strain curve was created. That is, a graph showing the relationship between the ratio of the thickness of the buffer material during the compression to the thickness of the buffer material in a natural state and the stress applied during the compression was created.

4-3. Buffer Coefficient/Strain Curve

The buffer material was compressed in the thickness direction, that is, the projection direction of a hemispherical projection using a universal test machine AG-IS (manufactured by Shimadzu Corporation), and a buffer coefficient/strain curve was created. That is, a graph showing the relationship between the ratio of the thickness of the buffer material during the compression to the thickness of the buffer material in a natural state and the buffer coefficient during the compression was created.

The results of the section 4-1 for each example and each comparative example are listed in Table 2, the results of the section 4-2 for Examples 1 to 4 are shown in FIG. 3, the results of the section 4-2 for Examples 5 to 8 are shown in FIG. 4, the results of the section [4-3] for Examples 1 to 4 are shown in FIG. 5, and the results of the section 4-3 for Examples 5 to 8 are shown in FIG. 6.

TABLE 2 Moldability Example 1 Possible Example 2 Possible Example 3 Possible Example 4 Possible Example 5 Possible Example 6 Possible Example 7 Possible Example 8 Possible Comparative Example 1 Impossible Comparative Example 2 Impossible

As is evident in Table 2, it was found that in each example, a buffer material having a desired shape was able to be produced and had excellent moldability.

Further, as is evident in FIGS. 3 and 4, it was found that in each example, the stress was almost constant in a wide range of strain, and the buffer material had excellent buffering performance.

Further, when buffer materials were produced in the same manner as in each example described above except that the average length of the cellulose fibers contained in the buffer materials was changed within a range of 10 μm or greater and 50 mm or less, the average thickness thereof was changed within a range of 1.0 μm or greater and 1000 μm or less, and the average aspect ratio thereof was changed within a range of 10 or greater and 1000 or less and the evaluations were performed in the same manners as described above, results similar to those described above were obtained.

Claims

1. A buffer material comprising:

cellulose fibers; and
a binding material that binds the cellulose fibers,
wherein the binding material is a natural component and a proportion of the binding material in the buffer material is 10.0% by mass or greater and 30.0% by mass or less.

2. The buffer material according to claim 1,

wherein the binding material contains a shellac resin.

3. The buffer material according to claim 1,

wherein the buffer material has a thickness of 1.0 mm or greater and 100 mm or less, and
the buffer material has a density of 0.02 g/cm3 or greater and 0.20 g/cm3 or less.

4. The buffer material according to claim 1,

wherein a content of lignin in the cellulose fibers is 5.0% by mass or less.
Patent History
Publication number: 20230037691
Type: Application
Filed: Jul 27, 2022
Publication Date: Feb 9, 2023
Inventors: Jun TAKIZAWA (Chino), Tetsuji FUJITA (Chino), Akio ITO (Matsumoto)
Application Number: 17/815,220
Classifications
International Classification: D21H 17/21 (20060101); D21H 21/06 (20060101);