JPH10217415A - Complex structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a complex structure which is lightweight and has high interlayer strength by a method wherein a pulp-based low density body of a specific density, containing curled fibers of a specific humic curl factor and fine fibers of a specific connection strengthening factor, and a sheet-shaped material or a molded item are stacked one over another. SOLUTION: By combining curled fibers and fine fibers having inter-fiber connection stronger than that of the curled fibers, a material in which low density and strength are balanced can be obtained. And a pulp-based low density body which contains curled fibers whose humid curl factor is in the range of 0.4-1.0 and fine fibers whose connection strengthening factor is 0.05 or more and which has the density of 0.05-0.45g/cm<3> and a sheet-shaped material or molded item are stacked one over another. And as the sheet-shaped material or molded item 2, high quality paper, thick paper, fiberboard, cloth, non-woven fabric, and metal foil can be employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite structure of a light-weight pulp-based low-density material having a high interlayer strength and a sheet or molded product.

[0002]

2. Description of the Related Art In general, low-density materials are used in various fields by taking advantage of their properties such as light weight, cushioning property, heat insulating property, sound absorbing property, and the like. It is a foam of a synthetic resin such as polyurethane or polyethylene. When these low-density materials do not provide sufficient performance by themselves or want to reduce prices, they are often used as composite structures bonded to other materials, such as high quality paper, paperboard, corrugated paper, It is used in combination with synthetic paper, cloth, nonwoven fabric, wood board, synthetic resin board or sheet, inorganic fiber paper such as glass fiber, metal foil or board and the like. However, although this synthetic resin foam is excellent in cushioning and heat insulating properties, it is not biodegradable and maintains its original shape when left in a natural environment. Has the problem of spoiling the aesthetics of the people and polluting the environment. Further, when the waste is treated by landfill, the lack of biodegradability and the fact that the waste is bulky are also troubled, which causes the life of the landfill disposal site to be shortened. In addition, since this material has a high calorie of combustion, it has a problem that when it is disposed in an incinerator, the combustion temperature becomes high, which damages the incinerator and shortens the life of the furnace.

[0003] Therefore, many proposals have been made on low-density cellulose fiber-based bodies that are biodegradable and have low burning calories. For example, a method of producing a foam by mixing cellulose fibers with a synthetic resin (Japanese Patent Laid-Open No. 55-23109,
JP-A-3-26925, JP-B-52-1915
No. 2) and a composition in which an adhesive selected from animal and vegetable pastes, synthetic resin emulsions, rubber latex, and the like are blended in a fixed ratio with cellulose fiber, and the decomposition temperature is 10%.
A method for producing a foam by containing a foaming agent at 0 ° C. or lower and foaming the foam (JP-A-7-41588), and heating a base paper obtained by mixing a cellulose foam with a particulate foaming agent and making paper. To produce low-density and bulky paper by foaming (JP-A-5-339898).
Bulky paper (Japanese Patent Application Laid-Open No. 3-124895) in which hollow spherical vaterite-type calcium carbonate is blended with cellulose fiber, crosslinked pulp obtained by reacting a crosslinking agent in the presence of a fiber softening agent, and heat fusion Bulky sheets obtained by molding a mixture of conductive fibers (JP-A-4-202895) and the like have been proposed.

[0004] However, a low-density body obtained by combining a cellulosic fiber with a heat-fusible fiber is excellent in bulkiness, but has few binding points between fibers and has a weak adhesive force. For this reason, delamination is apt to occur, and paper powder is likely to be generated during the production, handling, or molding, which causes a problem in the working environment in a place where the paper is produced or handled. Also, in the case of a method of obtaining a low-density body by foaming with the above-mentioned foaming agent, it is difficult to control the foaming state, the foaming state tends to be a locally different uneven structure, and the part where foaming has progressed excessively is There is a problem that delamination is apt to occur, and paper powder is generated from that portion. Further, in the case of a method using a resin or fiber having no biodegradability, the above-mentioned matter becomes a problem at the time of disposal.

[0005]

In view of such circumstances, the present inventors have conducted intensive studies to obtain a composite structure having excellent properties by using biodegradable cellulose fibers as a raw material. It has been found that the low-density body layer can be obtained by draining and drying a slurry containing specific curled fibers and fine fibers, and the present invention has been completed. The reason for the success of the present invention is that curled fibers having a wet curl factor in the range of 0.4 to 1.0 have extremely low bond strength between fibers, but tend to have a low density because they can hold many voids. Attention is focused on combining this with another fiber for strengthening the inter-fiber bond. Also, by combining the low-density layer and a layer made of another material, for example, strength,
Surface strength, waterproof / moisture proof, gas barrier properties, flexibility,
The point is that it has been found that a material having a higher level of performance such as smoothness and printability can be obtained. An object of the present invention is to provide a composite structure of a pulp-based low-density body having a light weight and excellent interlayer strength, and a sheet or a molded article.

[0006]

According to the present invention, there is provided a composite structure comprising:
A curled fiber having a wet curl factor in the range of 0.4 to 1.0, a fine fiber having a bond reinforcing factor of 0.05 or more, and a density of 0.05 to 0.45.
It is characterized by being laminated with a pulp-based low-density body of g / cm ³ and a sheet-like or molded article. The composite structure of the present invention is such that the sheet-like material or the molded product is a high-quality paper, a paperboard, a cardboard paper, a pulp mold, a cloth, a nonwoven fabric, a wooden board, a synthetic resin board or sheet, an inorganic fiber paper, an inorganic paper, a metal foil, It is preferably either a metal plate or a sheet-like material or a molded product obtained by combining these. In the composite structure of the present invention, the binding reinforcing factor of the fine fibers is preferably 0.15 to 1.5. In the composite structure of the present invention, the water retention of the curled fiber is preferably in the range of 10 to 80%. In the composite structure of the present invention, the low-density body contains the fine fibers in a ratio of 3 to 65% by weight based on the total fiber weight and the curled fibers in a ratio of 35 to 97% by weight based on the total fiber weight. Is preferred. Furthermore, in the composite structure of the present invention, it is preferable that the low-density body is a sheet or a molded body.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The composite structure of the present invention contains a curled fiber having a wet curl factor in the range of 0.4 to 1.0, and a fine fiber having a bond reinforcing factor of 0.05 or more, And a density of 0.05 to 0.45 g / cm
^The pulp-based low-density body of No. ³ and a sheet or a molded body are laminated, and examples thereof include a configuration shown in FIGS. The part 1 in the figure is a pulp-based low-density body, and the part 2 is a sheet or a molded body. These are usually bonded together using an adhesive, but they can be bonded together as long as they have adhesiveness to each other. FIG. 1 shows an example in which a pulp-based low-density body 1 is laminated on one surface of a sheet-like material 2, and FIG. 2 shows an example in which a pulp-based low-density body 1 is partially laminated on one surface of a sheet-like material 2. FIG. 3 is an example in which the sheet-like material 2 is laminated on both sides of the pulp-based low-density body 1, and FIG. 4 is an example in which the pulp-based low-density body 1 is laminated on both sides of the sheet-like substance 2. Further, FIG. 5 shows an example in which the pulp-based low-density body 1 is adhered to the four corners of the box made of the sheet-like material 2, and an effect of protecting the material placed therein from impact can be expected. The structure and size of the pulp-based low-density body 1 and the sheet-shaped or molded body 2 are designed according to the shape and size of the contents. The shape of the composite structure of the present invention is not limited to shapes such as a sheet shape and a plate shape as shown in the drawing, and the shapes to be bonded may be different from each other. Can also be laminated.

As the sheet-like material or molded article 2 used in the present invention, those having various materials and various shapes depending on the application are used. For example, high-quality paper, paperboard, corrugated paper, pulp mold , A cloth, a nonwoven fabric, a wooden board, a synthetic resin board or sheet, an inorganic fiber paper, an inorganic paper, a metal foil, a metal plate, and a sheet or molded article obtained by combining these are preferably used. It is also possible to obtain a desired composite structure by laminating pulp-based low-density bodies composed of curled fibers and fine fibers and having different physical properties such as density and strength.

The success of the present invention is attained by combining curled fibers with fine fibers having a stronger inter-fiber bond than the curled fibers, thereby achieving a low-density that could not be achieved by a combination of curled fibers and other binders. It has been found that it can be a material with a good balance of strength.

[0010] The curled fiber is a pulp fiber having an apparent length smaller than that of the original fiber, in which deformation such as curling or twisting is fixed by chemical bonding by a crosslinking reaction. A curled fiber having a wet curl factor in the range of 0.4 to 1.0 is used. Incidentally, the wet curl factor is an index indicating the degree of deformation of the fiber in a wet state, and the actual length (LA) of the fiber after immersing the curled fiber in pure water at room temperature for 24 hours and the fiber The maximum projection length (the length of the longest side of the rectangle surrounding the fiber, LB) is measured using a microscope,
This is a value calculated by [(LA / LB) -1], which is a numerical value indicating how much the fiber is curved from the original length of the linear fiber. The importance of the wet curl factor, which indicates the state of curl in a wet state, is that no matter how high the curl factor in a dry state, if the wet curl factor is small, the curl will return by wetting and the density will be low. Because it is difficult.

The curled fiber having a wet curl factor in the range of 0.4 to 1.0 is bent by imparting a considerable amount of deformation to the pulp fiber, and the fiber is rigid because of the cross-linking. Therefore, the slurry obtained by dehydrating and drying the slurry composed of the slurry alone has a low density.
However, in this material, the entanglement between the fibers is weak, and the hydroxyl group (-OH) of the cellulose molecule is reduced by the crosslinking treatment, so that the hydrogen bond due to the hydroxyl group is hardly generated. The interlaminar strength is weak, and the single system cannot be put to practical use. After adding a cross-linking agent to the pulp fiber, mechanical stirring is performed, followed by fluffing and heat treatment. When the fiber is fixed while being deformed, a curled fiber having a large wet curl factor is obtained.

Known curled fibers can be used in the present invention. For example, a crosslinked fiber having an average water retention of 28% to 50% obtained by crosslinking the inside of a cellulosic fiber using a C2 to C8 dialdehyde and a C2 to C8 monoaldehyde having an acid functional group (Japanese Patent Publication No. 5-71702)
JP-A-3-206174, JP-A-3-2174, and cross-linked fibers having a water retention of 25% to 60% obtained by internally crosslinking cellulosic fibers using C2 to C9 polycarboxylic acids.
No. 06175, JP-A-3-206176) and commercially available products (for example, trade names: HBA-FF, NHB405, NHB4, manufactured by Warehauser, USA)
16 etc.), which are appropriately selected and used.

The curled fiber preferably has a water retention value indicating the ability to retain water in the range of 10 to 80%. Especially, the thing of the range of 25-60% is more preferable. If the water retention is less than 10%, the number of hydroxyl groups (-OH) on the surface of the cellulose is too small and the bonding between fibers becomes weak, and the low-density body tends to have poor shape retention. Further, when the water retention degree exceeds 80%, the curl elongates in a wet state in a relatively short time and approaches the original fiber shape, so that the density varies depending on the length of the preparation time. For example, there is a problem that a low-density body cannot be obtained stably. However, even if a material other than this range is used, it may be practicable depending on the application, and therefore the water retention of the curled fiber of the present invention is not limited to this range. Incidentally, the water retention is defined as a value (%) in which the amount of water retained by the fiber after the fiber in a wet state is dehydrated by a centrifugal force of 3000 G for 15 minutes is expressed as 1 g of the absolutely dried fiber. The measurement method is JAPAN TAPPI No. 26-78.

As the fine fibers constituting the low-density layer of the present invention, natural polymer fibers, synthetic polymer fibers, semi-synthetic polymer fibers or those obtained by treating them are usually used. By using fine fibers of 0.05 or more, a low density layer having sufficient interlayer strength can be obtained. When a fine fiber having a bond reinforcing factor of less than 0.05 is used, the bonding between the curled fibers becomes insufficient, and the resulting low-density body is liable to cause delamination and paper powder is likely to occur, which is not practical. Preferably, fine fibers having a bond reinforcing factor in the range of 0.15 to 1.5 are used, more preferably 0.20 to 1.5.
Are used. Fine fibers exceeding 1.5 can be used satisfactorily in the present invention in terms of quality, but increase the production cost.

[0015] The size of the fine fibers used in the present invention is not particularly limited, but usually those having a number average fiber length in the range of 0.01 to 0.80 mm are preferably used. Furthermore, in terms of yield and dispersibility, 0.05 to
Those having a range of 0.60 mm are more preferable. As the fiber form, there are various forms such as a form in which most of the fibers are made of fine fibers, and a form in which a part of pulp fibers is fibrillated and only that part is made into a thin fibrous form and dispersed.
Therefore, the fiber width varies depending on the type of pulp fiber and the treatment method, and cannot be generally described, but is usually 0.1 to
Those having a width of 30 μm are preferably used.

Examples of natural polymer fibers include unbleached or bleached chemical pulp, GP, TMP (thermomechanical pulp), etc. obtained by kraft pulping, sulfite pulping, alkali pulping of coniferous or hardwood. Pulp fibers such as mechanical pulp, cotton pulp, linter pulp, and waste paper pulp; cellulose fibers such as bacterial cellulose; protein fibers such as wool, silk, and collagen fibers; and composites such as chitin / chitosan fibers and alginate fibers. Sugar chain fibers and the like can be mentioned. Examples of the synthetic polymer fibers include fibers synthesized from monomers such as aliphatic polyester fibers, polyethylene fibers, polypropylene fibers, and aramid fibers. Examples of the semi-synthetic polymer fiber include a fiber obtained by chemically modifying a natural product, such as an acetylcellulose fiber.

Among them, those having biodegradability such as cellulosic fibers, aliphatic polyester fibers, and acetylcellulose fibers are preferably used. Further, from the viewpoints of stability of raw material supply and cost, a cellulosic fiber or one obtained by treating the same is more preferable. Further, mechanical pulp such as unbleached or bleached chemical pulp, GP, TMP (thermomechanical pulp), cotton pulp, linter pulp, waste paper obtained by kraft pulping, sulfite pulping, alkali pulping, etc. of softwood or hardwood. Fine fibers obtained by mechanically treating pulp fibers such as pulp by a wet method tend to have a branched shape, and the effect of improving interlayer strength is particularly large and is preferable.

Examples of the mechanical treatment include a medium stirring mill treatment (JP-A-4-18186), a vibration mill treatment (JP-A-6-10286), a treatment with a high-pressure homogenizer, a colloid mill treatment, and the like. Although a beating machine treatment is mentioned, the present invention does not particularly limit a treatment device.
Among the processing apparatuses, the fine fiber pulp obtained by the medium stirring mill or the vibration mill is more easily obtained than the pulp fibers obtained by other processing apparatuses. It is particularly preferable that curled fibers used in the present invention can be efficiently and firmly bonded to each other because the fibers are finely dimensionally formed.

Incidentally, the medium stirring mill is a device for inserting a stirrer into a grinding container filled with glass beads or alumina beads and rotating at a high speed to grind the dispersion in the slurry by shearing stress. There are a tank type, a flow tube type, an annular type, and the like. A vibration mill is a device that vibrates a crushing container at high speed and applies a force such as an impact force or a shearing force to a dispersion in a slurry by beads, balls, rods, or the like filled in the container. In addition, the high-pressure homogenizer applies high pressure to pass between small-diameter orifices,
This is a device for crushing a dispersion in a slurry.

[0020] The binding enhancement factor (BF) referred to in the present invention.
Is calculated by (E2−E1) / E1. However, in E1, only pulp fibers (for example, LBKP, NBKP, etc.) beaten to a freeness of 500 ml in Canada are disintegrated in water to prepare an aqueous slurry, which is then dewatered and air-dried by a hand-making machine, and then at 130 ° C. A sheet having a basis weight of 60 g / m ² was prepared by heat treatment for 1 minute, and the ultrasonic elastic modulus measured after adjusting the humidity to 20 ° C. and 65% RH is shown. E2 is 50 of the above pulp fibers.
% Was replaced with fine fibers to prepare an aqueous slurry.
Shows the ultrasonic elastic modulus when a sheet is prepared and measured by the same method as used for measuring the elastic modulus. Incidentally, the ultrasonic elastic modulus is calculated from the value of the ultrasonic wave propagation velocity measured using a dynamic Young's modulus measuring device (model: SST-210A, manufactured by Nomura Corporation).
It was calculated according to the following equation. E (GPa) = ρ (g / cm ³ ) × {S (km / s)} ² where ρ is the density (g / cm ³ ) of the sheet after humidity control, and S is the ultrasonic wave propagation velocity (km / s). ).

The fine fiber pulp used in the present invention preferably has a water retention value in the range of 120 to 500%. Further, it is more preferably in the range of 165 to 500%, and particularly preferably in the range of 210 to 450%. By the way, when water retention is less than 120%,
Due to insufficient bonding ability of the fibers, the power to bind the curled fibers is not enough.The low-density body obtained by combining such fine fibers and the curled fibers has insufficient interlayer strength and paper powder. Tends to occur. In particular, when the low-density body is a sheet, the paper strength is insufficient, making it impractical for some applications. On the other hand, the water retention is 500%
When it exceeds, the production cost of the fine fiber increases. In the present invention, the fine fibers as described above can be used alone or in combination of two or more.

The mixing ratio of the curled fiber and the fine fiber in the low-density layer of the present invention can be appropriately selected according to the purpose because the balance between the density and the interlayer strength can be controlled by changing the ratio. it can. That is, when the interlaminar strength is more important than the density, the blending of the fine fibers is increased. On the contrary, when the density is more important than the interlaminar strength, the curling fiber is increased. Above all, 3 to 3 fibers per absolute dry weight of all fibers
When 65% by weight and curled fiber are mixed and used at a ratio of 35 to 97% by weight based on the total fiber dry weight, the balance between the density and the interlayer strength is particularly excellent.

In the low-density layer of the present invention, organic synthetic fibers, inorganic fibers, paper strength agents, water-proofing agents, water-repellent agents, foamable microcapsules, sizing agents, etc. Dyes, pigments, retention aids, fillers, pH regulators, slime control agents, thickeners, preservatives, fungicides, antibacterial agents, flame retardants, preservatives, rodenticides, insect repellents, moisturizers, freshness preservatives , An oxygen scavenger, a microcapsule, a foaming agent, a surfactant, an electromagnetic shielding material, an antistatic agent, a rust inhibitor, a fragrance, a deodorant and the like can be selected and blended. These may be used in combination of two or more.

Examples of the organic synthetic fiber include polyethylene fiber, polypropylene fiber, polyacrylonitrile fiber, acrylic fiber, polyester fiber, polyamide fiber and the like. Among them, biodegradable fibers such as aliphatic polyester and acetyl cellulose are preferable. Is particularly preferred.
Further, as the shape of the fiber, a fiber having a bend such as a curl is more preferable than a straight fiber because an effect on lowering the density can be expected. These may be used alone or in combination of two or more. The amount of the organic synthetic fiber varies depending on the use of the low-density body, but is usually added in the range of 0 to 30% by weight of the total solids. The addition of organic synthetic fibers is generally effective in improving the strength in a wet state of water.

As the inorganic fibers, for example, glass fibers,
Examples thereof include carbon fiber, alumina fiber, silicon carbide fiber, silica / alumina silicate fiber, and rock wool fiber. These may be used alone or in combination of two or more. The amount of the inorganic fiber varies depending on the use of the low-density body, but is usually added in the range of 0 to 30% by weight of the total solids. The addition of inorganic fibers is generally effective in improving heat resistance and the like.

Examples of the paper strength enhancer include starch, processed starch, vegetable gum, dry paper strength enhancer such as PVA, urea formaldehyde resin, melamine formaldehyde resin, polyamide urea formaldehyde resin, ketone resin, polyamide epichlorohydrin resin, polyamide Examples include wet paper strength agents such as polyamine epichlorohydrin resin, glycerol polyglycidyl ether resin, and polyethyleneimine resin. These may be used alone or in combination of two or more. The amount of the paper strength enhancer varies depending on the use of the low-density body, but is usually added in the range of 0 to 10% by weight of the total solids. The addition of a paper strength enhancer is generally effective in improving strength and the like. In particular, when a wet paper strength enhancer is used, there is a great effect on improving the strength in a wet state with water.

As the water-proofing agent, the above-mentioned wet paper strength enhancer can be used as a water-proofing agent, and formaldehyde having an aldehyde group, glyoxal, dialdehyde starch,
Examples thereof include ammonium zirconium carbonate, which is a polyvalent metal compound. Examples of water repellents include various waxes (natural wax, petroleum wax, chlorinated paraffin, wax emulsion, etc.), higher fatty acid derivatives, synthetic resins,
Chromium complex salts, zirconium salts, silicon resins and the like can be mentioned. The water-proofing agent and the water-repellent agent may be used alone or in an appropriate combination of two or more. Addition of a water-proofing agent and a water-repellent agent is effective in improving the water resistance of the low-density body. The compounding amount varies depending on the use of the low-density body, but is usually 0 to 1 of the total solid content.
It is added in the range of 0% by weight.

The foamable microcapsules are obtained by encapsulating a low-boiling solvent in fine resin particles and having a temperature of 70 to 150 ° C.
Particles having an average particle diameter of 5 to 30 μm which expand 3 to 5 times in diameter and 30 to 120 times in volume at the temperature described above are usually used.
As the resin material, a thermoplastic resin composed of a copolymer such as vinylidene chloride, acrylonitrile, acrylate, and methacrylate is usually used.As the low-boiling solvent, isobutane, pentane, petroleum ether, hexane, and a low-boiling halogen are generally used. Hydrocarbons and the like are used. These foamable microcapsules may be used alone or in an appropriate combination of two or more. The amount varies depending on the use of the low-density body, but is usually 0 to 30% by weight of the total solids.
Is added within the range. The foamable microcapsules are foamed by heat in the drying step, and have an effect of further lowering the density.

The slurry used for forming the low-density material of the present invention is usually prepared in a batch system or continuously by using a device having a stirrer. The carded fiber should not be left in the water for a long time, but should be defibrated immediately before the production of the low-density body,
It is desirable to mix it with fine fibers. The reason is that although the hydrophilicity of curled fiber is lower than that of ordinary pulp, if it is immersed in water for a long time, the fiber itself becomes flexible including water, and the density tends to increase even if manufactured under the same pressing pressure This is because the bulk is difficult to appear. Accordingly, the preparation of the aqueous slurry is preferably of a continuous type which can be prepared in accordance with the production of a low-density body, rather than a batch type. Water is usually used as a medium used to form the slurry, but a mixed solution of water and an alcohol (methanol, ethanol, glycerin, etc.), or an organic solvent such as alcohol, acetone, ethyl acetate, glycerin, etc. can do. The concentration of the slurry varies depending on the low-density body manufacturing apparatus, but is usually adjusted to a dry solid content of 0.05 to 10% by weight. Generally, in the case of a paper machine, it is prepared such that the dry solid content is 0.05 to 2% by weight. If the concentration is too high, the curled fiber and the fine fiber are not mixed well, which is not preferable. The low-density body of the present invention can be obtained by a slurry method using a medium, a so-called wet method. However, compared to a dry method using no medium, the mixing of the fibers is more likely to be uniform, and the bonding by hydrogen bonding between the fibers becomes stronger. Therefore, a strong one can be obtained.

Examples of the shape of the low-density body of the present invention include a sheet (sheet or board) and a molded body. In the case of a so-called sheet, it can be manufactured using a paper machine for papermaking, such as a round paper machine, a fourdrinier paper machine, an inclined paper machine, and a twin wire paper machine. The thickness of the sheet obtained by these paper machines is 30 μm to 5 μm.
mm. The density of the sheet obtained is affected by the type of curled fiber or fine fiber or the compounding ratio thereof, and the type or compounding amount of other additives. In addition, the pressure applied to the sheet in the production stage is important. In order to make the density as low as possible, reduce the degree of vacuum of the suction roll to reduce the dehydration pressure at the wire part, reduce the pressure of the dandy roll as much as possible, reduce the press pressure, tension and size of the dryer canvas It is important to reduce the press pressure of the press and not to use the on-machine calendar. In the present invention, a slurry having a range of 0.05 to 0.45 g / cm ³ can be obtained by mixing the slurry and devising the production.

A sheet having a thickness of 5 mm to several cm is generally called a board, and can be manufactured using the same paper machine as described above for a sheet. The thin sheets can be laminated to form a thick product. In the case of a board, as in the case of a sheet, 0.05-0.4
Those having a range of 5 g / cm ³ can be obtained. As a special manufacturing method, a method of extruding a slurry into a board under high temperature and high pressure by an injection method is also effective. At this time, if a high amylose-containing starch is also added to the slurry, a slurry having a lower density can be obtained. It should be noted that a plurality of sheets or boards obtained by the above method can be laminated to form a thicker sheet or board.

The molded article can be obtained in a desired form by a pulp molding method or an injection method.
This can be achieved by selecting the formulation of the slurry.
Those having a range of 5 to 0.45 g / cm ³ can be obtained.

As a net used for dewatering the slurry in a paper machine or a pulp mold manufacturing machine, for example, generally used mesh sizes such as 60 and 80 can be used, but the fine fibers are extremely fine or When the slurry concentration is low, a fine mesh having a mesh size of 150 mesh or more is appropriately used. The apparatus for producing a low-density body used in the present invention is not limited to the above.

In the low-density body, a paper strength enhancer, a waterproofing agent, a water repellent, a dye, a preservative, a fungicide, an antibacterial agent, a rust preventive, a flame retardant,
Preservatives, rodenticides, insect repellents, moisturizers, freshness preservatives, oxygen scavengers, fragrances, deodorants, surfactants, antistatic agents, electromagnetic shielding materials, etc. In addition to the internal addition method of adding and mixing these, a sheet, a board, a method of applying a surface after manufacturing a molded body,
That is, the external addition method can be used. For this coating, means such as coating, brushing, and spraying can be used. Of course,
External addition may be used in combination.

The composite structure of the present invention may be prepared by adding, to the low-density body obtained as described above, for example, high-quality paper, paperboard, corrugated paper, pulp mold, cloth, nonwoven fabric, wood board, synthetic resin board or sheet, inorganic resin Fiber paper, inorganic paper, metal foil, metal plate, and a sheet-like material formed by combining these, a molded product can be laminated, but the lamination method, lamination method is not particularly limited. Absent.

Depending on the material to be bonded, a composite structure having excellent properties that cannot be achieved by using only the low-density body can be obtained. For example, by adhering to a synthetic resin plate or sheet, water resistance, strength, barrier properties, and the like can be improved. By laminating with high-quality paper, paperboard, corrugated cardboard, or wood board, surface strength, surface printability, barrier property buffering properties, and the like can be improved. By bonding with a nonwoven fabric or a cloth, the softness of the surface can be improved. By bonding with inorganic fiber paper or inorganic paper,
Heat resistance and the like can be improved. In addition, by combining with a normal pulp mold, the buffering property, the surface smoothness and the like can be improved. Note that the bonding can also be performed after each material is processed into a desired shape. As a material to be attached, a material having biodegradability is preferable.

For example, when a heat-sealing material is included in a layer, the bonding between the layers can be performed only by a heat treatment. Also, when a plurality of layers are continuously formed and dried by a pulp mold method, or when a plurality of wet paper webs are dried as in a paper board manufacturing method, a system in which fiber entanglement easily occurs. In this case, bonding between layers is possible without using a binder. However, a binder is usually used for bonding. Examples of the binder include starch,
PVA, CMC, urea formalin resin, melamine formalin resin, SBR latex, vinyl acetate latex, EVA, ethyl acetate, butyl acetate and the like.
These are applied as an aqueous system, a solvent system, or a hot melt system. The coating amount is usually 3 to 50 g / m ² .

[0038]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but it should be understood that the present invention is not limited to these examples.
In Examples and Comparative Examples, “parts” and “%” indicate “parts by weight of solid content” and “% by weight” unless otherwise specified.

Example 1 A 1.5-liter Dynomill (model: KDL-PIL) filled with 70% glass beads having an average particle size of 2 mm was filled with an aqueous slurry of bleached hardwood kraft pulp having a solid content of 1%.
OT type, manufactured by Shinmaru Enterprises)
By introducing and passing at a flow rate of 00 ml / min, the bond strengthening factor is 0.60, the number average fiber length is 0.25 mm,
Fine fibers having a water retention of 310% were obtained. Also, 30 g of soft-dried bleached kraft pulp is put into a 1-liter double-arm kneader (model: S1-1, manufactured by Moriyama Seisakusho), and a non-formaldehyde crosslinking agent (trade name: Sumitex N)
F-500K, manufactured by Sumitomo Chemical Co., Ltd.) and its crosslinking aid (trademark: Sumitex ACCELATOROR X-60,
2. Sumitomo Chemical Industries, Ltd.)
0% and 0.25%, and then water was added to adjust the solids concentration to 35%. Then, at 27 ° C., the two arms were rotated at 60 rpm and 100 rpm, respectively, and stirred for 20 minutes. did. Thereafter, the pulp was taken out of the kneader, the pulp was loosened by hand, and the pulp mass was disintegrated and fluffed with a laboratory Warren blender. Then, the fluffed pulp was put into a blow dryer at a temperature of 150 ° C., and was not restrained. After drying for 2 hours, a curled fiber having a wet curl factor of 0.75 and a water retention of 45% was obtained.

Next, water was added to a mixture of 85 parts of the curled fiber and 15 parts of the fine fiber to adjust the solid content concentration to 1%, and the mixture was sufficiently stirred to obtain a pulp slurry. Next, using this pulp slurry as a raw material, a small pulp mold molding machine having a board mold (model: SDM
Mold, manufactured by Noritake Company), and then dried while hot-pressing to obtain
A board of 0 mm × width 500 mm × thickness 30 mm was obtained.
Finally, a polyethylene film having a thickness of 20 μm was laminated on one side of the board to obtain a composite structure. A commercial cutter knife (trade name:
25 mm long, 25 mm wide with NT cutter L-500)
A sheet having a thickness of 5 mm was cut out, and the interlayer strength was measured. At the time of cutting, almost no generation of paper dust was observed.
Further, after water was dropped on the surface of the composite structure, the surface was wiped off and the wetness of the surface was observed. As a result, unlike the other surfaces, no wetness was observed on the surface laminated with the film. Table 1 shows the measurement results of the density of the low-density layer and the delamination strength.

Hereinafter, a method for evaluating the characteristics of the used fine fiber and the curled fiber and a method for measuring the delamination strength will be described. Evaluation method [Measurement method of binding enhancement factor] 50 parts of bleached hardwood kraft pulp and 50 parts of softwood bleached kraft pulp are mixed,
Adjust to 2% concentration and use Canadian Standard Freeness (CSF) 500 in a laboratory Niagara beater (23 L capacity).
Refined until the volume was up to ml. A 3.7 g portion of this paper stock was completely dried, and a sheet was formed using a 150-mesh wire using a square (25 cm × 25 cm) hand-making machine without adding chemicals. After performing wet press for 5 minutes (first press) and 2 minutes (second press) at a pressure of 3.5 kg / cm ² , drying was performed at room temperature by a blow dryer between frames. Thereafter, the sheet 1 was heat-treated at 130 ° C. for 2 minutes to prepare a sheet 1 having a basis weight of 60 g / m ² , and was conditioned at 20 ° C. and 65% RH. on the other hand,
3.7 g of absolutely dried material was taken from a raw material in which 50 parts of the above-mentioned NL-mixed beaten pulp and 50 parts of fine fibers were well mixed, and a sheet 2 was prepared in the same manner and conditioned at 20 ° C. and 65% RH. After measuring the densities of the sheets 1 and 2, a dynamic Young's modulus measuring device (manufactured by Nomura Shoji Co., Ltd., model: SST-210A)
The elastic modulus (GPa) of the sheets 1 and 2 was measured by measuring the ultrasonic wave propagation velocity using Modulus of elasticity (E)
Was calculated by the following equation. E (GPa) = ρ (g / cm ³ ) × {S (km / s)} ² where ρ is the density (g / cm ³ ) of the sheet after humidity control, and S is the ultrasonic wave propagation velocity (km / s). ). The elastic modulus of the sheet 1 is E1 (GPa), and the elastic modulus of the sheet 2 is E2 (GPa).
, The bond strengthening factor is ｛(E2 / E1) −
It is represented by 1｝.

[Measurement method of number average fiber length] Measured by a Kayani fiber length measuring instrument (model: FS-200).

[Method of measuring water retention] The water retention was measured by JAPA.
N TAPPI No. It measured according to 26-78.
When the carded fiber was in a dry state, the following was performed. Collect 0.5 g of paper material in absolute dryness, 100 m of distilled water
1 and sufficiently allowed to stand at room temperature for 24 hours to be sufficiently impregnated with water. Thereafter, the stock was collected on a filter, then placed in a centrifuge tube of a centrifuge (model: H-103N, manufactured by Domestic Centrifuge) having a G2 glass filter, and dewatered at a centrifugal force of 3000 G for 15 minutes. . The sample subjected to the centrifugal dehydration treatment was taken out from the centrifuge tube, and the weight in a wet state was measured. Thereafter, the sample was dried to a constant weight with a dryer at 105 ° C., the dry weight was measured, and the water retention was calculated by the following equation. Water retention (%) = {(WD) / D} × 100 where W is the wet weight (g) of the sample after centrifugal dehydration, and D is the dry weight (g) of the sample. In the case of fine fibers, the solid content is adjusted to a range of 6 to 9%, and a sample is collected so as to have an absolute dry weight of 0.7 g, placed in a centrifuge tube having a G3 glass filter, and Similarly, centrifugal dehydration was performed, and the water retention was calculated from the wet weight and the dry weight according to the above equation.

[Measurement Method of Wet Curl Factor] 100 pieces of curled fibers after being immersed in distilled water at room temperature for 24 hours are placed on a microscope slide glass, and each fiber is used for each fiber using an image analyzer. The actual (linear) length LA (μm) and the maximum projected length (equal to the length of the longest side of the rectangle surrounding the fiber) LB (μm) were measured, and the wet curl factor was obtained from the following equation. The average value was used. Wet curl factor = (LA / LB) -1

[Measurement Method of Delamination Strength] The delamination strength was measured based on TAPPI UM403.

Example 2 A 1.5-liter Dynomill (model: KDL-PIL) filled with 80% glass beads having an average particle size of 2 mm was filled with a water slurry of bleached hardwood kraft pulp having a solid content of 1%.
4 for OT type (Shinmaru Enterprises)
By introducing and passing at a flow rate of 70 ml / min, fine fibers having a bond reinforcing factor of 0.43, a number average fiber length of 0.32 mm and a water retention of 223% were obtained. 15 parts of these fine fibers,
85 parts of a commercially available curled fiber (trade name: NHB416, manufactured by Warehauser, USA) having a wet curl factor of 0.65 and a water retention of 50% were mixed, and water was added to adjust the solid content to 2%. The mixture was stirred to obtain a sufficiently dispersed fiber slurry. A raw material equivalent to 150 g of absolutely dry was taken from this slurry, dehydrated by a square (25 cm × 25 cm) hand-made sheet machine equipped with an 80 mesh bronze wire, and a wet board was formed on the wire. The wet board was transferred from a wire onto a stainless steel plate having countless holes of 3 mmφ covered with filter paper, and dried as it was at 105 ° C. in a blow dryer. After drying, 20
After humidification at 65 ° C. and 65% RH, the weight of the board (A) was 152 g and the thickness was 20 mm. On the other hand, 15 parts of the fine fiber, 50 parts of the curled fiber, and unbeaten softwood bleached kraft pulp (freeness 717)
(ml CSF) was mixed, and water was added to prepare a slurry adjusted to a solid content concentration of 2%. A board (B) was prepared in the same manner as described above by taking 280 g of absolutely dry raw material from this slurry. After humidification at 20 ° C. and 65% RH, the board (B) weighs 283 g and has a thickness of 20
mm.

Next, a board having a length of 120 mm and a width of 120 mm was cut out of each of the boards (A) and (B) using a commercially available cutter knife, and the two boards (B) obtained from the board (B) were cut out. A hole with a diameter of 30 mmφ was formed in (B-1), and a hole with a diameter of 100 mmφ was formed in (B-1) using a thread saw and a cutter knife at the center of each of the parts (-1, B-2). Further, one of the boards (A) and (B-1)
With a commercially available vinyl acetate resin emulsion-based adhesive (trade name: Woodworking Bond, manufactured by Konishi Co., Ltd.).
mm, 120 mm wide and 40 mm high (AB-
1) was obtained. Similarly, the remaining one of the boards (A) and (B-
2) was adhered to obtain a structure (AB-2). On the other hand, a commercially available double-faced corrugated cardboard (standard A, thickness 5 mm) was processed using a cutter knife and the above-mentioned adhesive, and the inner size was 120 m in length.
A rectangular parallelepiped box having a size of 120 mm, a width of 120 mm, and a height of 440 mm was opened and closed. The upper part of this box is opened, the above-mentioned adhesive is applied to the non-hole side (A side) of the structure (AB-2) obtained above, and the box is inserted into the box so that this surface faces down. And glued to the bottom of the box.

Further, an unopened Japanese sake bottle (top diameter 30 mmφ, bottom diameter 100 mmφ, height 400 mm) is inserted into the box while being inserted into the structure (AB-2), and the structure (AB) is inserted at the top. -1) was overlapped so that the top of the bottle was inserted into the hole, and finally the opening of the cardboard was closed and fastened with adhesive tape. The box containing the bottle was dropped on a concrete surface from a height of 50 cm. However, the bottle was not broken and the liquid did not leak, and there was no problem in practical use. Further, a sheet having a length of 25 mm, a width of 25 mm, and a thickness of 5 mm was cut out from the rest of the board (A) and the board (B), and was subjected to interlayer peel strength measurement. Table 1 shows the measurement results of the density and the delamination strength of the board (A) and the board (B).

Example 3 95 parts of the curled fiber and 5 parts of the fine fiber used in Example 1 were mixed, diluted with water to a solid concentration of 2%, and sufficiently dispersed in a fiber slurry. I got From the slurry, a raw material equivalent to 30 g of absolutely dry was taken, and a dry board was obtained using a square hand-making machine in the same manner as in Example 2. 20 ° C, 6
The weight of this board after humidity control at 5% RH is 31.2 g,
The thickness was 5.0 mm. Vertical 2 from part of this board
A sheet having a thickness of 5 mm, a width of 25 mm, and a thickness of 5 mm was cut out and subjected to measurement of delamination strength. Next, on both sides of the remaining board, using the commercially available adhesive used in Example 2, a basis weight of 1
A high-quality high-quality paper having a thickness of 57 g / m ² and a thickness of 0.17 mm was laminated. After drying, a board having a length of 15 cm and a width of 20 cm was cut out from this structure with a commercially available cutter knife to obtain a photographic panel. No paper dust was generated during cutting. This composite structure had a thickness of 5.4 mm and a density of 0.16 g / cm ³ . Table 1 shows the measurement results of the density and the delamination strength of the low-density layer.

Example 4 A water slurry of bleached hardwood kraft pulp having a solid content of 3% was repeatedly beaten with a 12-inch refiner (manufactured by Kumagaya Riki Kogyo Co., Ltd.) to a freeness of 396 ml CSF to obtain a bond reinforcing factor of 0.10 and a number average fiber. A fiber having a length of 0.46 mm and a water retention of 125% was obtained. A composite structure was obtained in exactly the same manner as in Example 1 except that this fiber was used in place of the fine fiber having a bond reinforcing factor of 0.60 and a water retention of 310%. A sheet having a length of 25 mm, a width of 25 mm, and a thickness of 5 mm was cut out from the low-density layer of the composite structure using a commercially available cutter knife (trade name: NT Cutter L-500) to measure the delamination strength. The occurrence of paper dust at that time was visually determined. As a result, although the generation of paper dust was considerably inferior to that of Example 1, it was at a level having no practical problem. Further, after water was dropped on the surface of the composite structure, the surface was wiped off and the wetness of the surface was observed. As a result, unlike the other surfaces, no wetness was observed on the surface laminated with the film. Table 1 shows the measurement results of the density of the low-density layer and the delamination strength.

Comparative Example 1 Water was added to the curled fiber obtained in the same manner as in Example 1 to adjust the solid concentration to 1%, and the mixture was sufficiently stirred to obtain a pulp slurry. Next, a composite structure was obtained in exactly the same manner as in Example 1 except that the above-mentioned slurry containing only the curled fiber was used instead of the slurry containing the mixture of the fine fiberized pulp and the curled fiber. The composite structure was cut with a commercially available cutter knife (trade name: NT Cutter L-500), and the occurrence of paper dust at that time was visually determined. Was. The sheet for measuring the delamination strength could not be cut out.

[0052]

[Table 1]

As can be seen from Table 1, the low-density layers used in Examples 1 to 4 have a low density and a high interlaminar strength, and can be sufficiently used in each application by forming a composite structure. It was of quality. As can be seen from Examples 1 and 4, a pulp-based low-density two-component curled fiber having a wet curl factor in the range of 0.4 to 1.0 and a fine fiber having a bond reinforcing factor of 0.05 or more. The composite structure obtained by laminating a film layer on a layer has a low generation of paper dust and the film lamination surface does not get wet with water. Above all, when a fine fiber having a bond reinforcing factor of 0.15 or more is used as the fine fiber, generation of paper powder is extremely small (Example 1). However, in the case of using only the curled fiber, paper dust was generated so violently that it was not suitable for practical use (Comparative Example 1). Further, in the present invention, a composite structure can be obtained by laminating two low-density layers having different densities, and a larger composite structure can be manufactured by combining the composite with another material such as cardboard. This makes the packaging material excellent due to the buffering property of the low-density layer (Example 2). Also, as shown in the third embodiment,
By bonding sheets to both sides of the low-density layer as well as to both sides, a low-density composite structure that can be used for a photographic panel, a display board, or the like can be manufactured.

[0054]

The present invention has the effect of providing a composite structure of a light-weight pulp-based low-density body having a high interlaminar strength and a sheet or molded article.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example in which a pulp-based low-density body 1 is laminated on one surface of a sheet-like material 2. FIG.

FIG. 2 is a cross-sectional view showing an example in which a pulp-based low-density body 1 is partially laminated on one surface of a sheet material 2.

FIG. 3 is a cross-sectional view showing an example in which a sheet-like material 2 is laminated on both surfaces of a pulp-based low-density body 1.

FIG. 4 is a cross-sectional view showing an example in which a pulp-based low-density body 1 is laminated on both surfaces of a sheet-like material 2.

FIG. 5 is a sectional view showing an example in which pulp-based low-density bodies 1 are arranged at four corners of a box made of a sheet-like material 2.

[Explanation of symbols]

 1: Pulp-based low-density material 2: Sheet-like material

Claims (7)

[Claims] 1. A wet curl factor of 0.4 to 1.0.
And a fine fiber having a bond reinforcing factor of 0.05 or more and a density of 0.1.
A pulp-based low-density body having a mass of from 0.5 to 0.45 g / cm ³ ,
A composite structure obtained by laminating a sheet or a molded product. 2. The sheet-like article or the molded article is made of high-quality paper, paperboard, corrugated paper, pulp mold, cloth, nonwoven fabric, wood board, synthetic resin board or sheet, inorganic fiber paper, inorganic paper, metal foil, metal sheet, The composite structure according to claim 1, wherein the composite structure is any one of a sheet-like material or a molded product obtained by combining these. 3. The method according to claim 1, wherein said fine fiber has a binding reinforcing factor of 0.1.
The composite structure according to claim 1, wherein the composite structure is 15 to 1.5. 4. The curled fiber has a water retention of 10 to 10.
2. The composite structure according to claim 1, which is in the range of 80%. 5. The low-density body according to claim 1, wherein the fine fibers are contained in a proportion of 3 to 65% by weight based on the total fiber weight, and the curled fibers are contained in a proportion of 35 to 97% by weight based on the total fiber weight. Composite structure. 6. The composite structure according to claim 1, wherein the low-density body is in the form of a sheet. 7. The composite structure according to claim 1, wherein the low-density body is a molded body.