JPH10219585A - Water-resistant low density structural material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable low density structural material having excellent water resistance and strength by performing water-resistant and/or water-repelling treatment to a low density material obtained by respectively specifying the value of a wet curl factor of curled fiber and that of a bond reinforcing factor of fine fibers contained in the structural material. SOLUTION: This water-resistant low density structural material is obtained by dipping or coating a water-resistant and/or water-repellent liquid or sticking a water-resistant and/or water-repellent sheet or board to a low density material obtained by dehydrating a slurry containing curled fibers using biodegradable cellulosic fibers and biodegradable fine fibers as raw materials. A wet curl factor of the curled fiber is made to 0.4-1.0 and a bond reinforcing factor of the fine fibers is made to >=0.15. The structural material is useful for a paper vessels, a water-resistant paper bag, a structural material for a civil engineering or constructing, a board for exhibition, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a pulp-based low-density structure having a water-resistant surface.

[0002]

2. Description of the Related Art In general, low-density bodies are used for their properties such as light weight, cushioning properties, heat insulation properties, sound absorption properties, and the like, for example, building insulation materials, food packaging materials, various trays, buffer packaging materials, and the like.
It is used in various fields such as various return boxes, heat insulation materials,
The most widely used is a synthetic resin foam such as polystyrene, polyurethane, or polyethylene. However, while this synthetic resin foam is excellent in cushioning, heat insulation, and water resistance, it does not have biodegradability and maintains its shape when left in a natural environment. There is a problem that the beauty of the place is damaged and the environment is polluted. If the waste is disposed of by landfill,
The lack of biodegradability and the fact that it is bulky are a disaster, which is a cause of shortening the life of landfills. Also, because this material has high combustion calories,
When disposed in an incinerator, there is a problem that the combustion temperature becomes high and the incinerator is damaged, thereby shortening 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. In addition, the cellulose fiber-based low-density body is water-absorbing and hygroscopic properties of cellulose as a material,
Due to the water swelling property, the water resistance is inferior to that of the synthetic resin foam, which is a serious problem depending on the use.

[0005]

In view of the above situation, the present inventors have made intensive studies to obtain a low-density structure excellent in water resistance by using a biodegradable cellulose fiber as a raw material. A low-density body obtained by dewatering and drying a slurry containing carded fibers and fine fibers,
By impregnating or coating with a water-resistant and / or water-repellent liquid, or by laminating a water-resistant and / or water-repellent sheet or board, a low-density structure excellent in water resistance and strength. They found that a body could be obtained and completed the present invention. Furthermore, the reason for the success of the present invention is that, as a low-density body, curled fibers having a wet curl factor in the range of 0.4 to 1.0 have extremely low bond strength between fibers, but can maintain a large amount of voids. Focusing on the fact that the density tends to be low, this is the point that this is combined with fine fibers for strengthening the bonding between fibers. Instead of the fine fibers used for forming the low density body of the present invention, starch, CMC, PV
A method of combining a water-soluble polymer such as A or PAM, or a latex such as styrene-butadiene or vinyl acetate is conceivable, but in that case, the yield is poor and the interlayer strength is difficult to be obtained even if a large amount is blended. The purpose of the present invention is
An object of the present invention is to provide a pulp-based low-density structure having low density and excellent water resistance.

[0006]

A water-resistant low-density structure according to the present invention comprises 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 0.15 or more. The low-density body containing fibers is subjected to water resistance and / or water repellency treatment. The water-resistant low-density structure of the present invention has a JIS surface whose surface has been subjected to water resistance and / or water repellency treatment.
The water repellency specified in P8137 is preferably in the range of R8 to R10. Water-resistant low-density structure of the present invention,
The curled fiber is used in an amount of 35 to 9 per dry weight of all fibers.
7% by weight, and the fine fibers are contained in an amount of 3 to 6
It is preferably contained in a proportion of 5% by weight. In the water-resistant low-density structure of the present invention, the low-density body has a density of 0.05 to 0.5.
It is preferably 45 g / cm ³ . Furthermore, in the water-resistant low-density structure of the present invention, it is preferable that the low-density body is a sheet or a molded body.

[0007]

DETAILED DESCRIPTION OF THE INVENTION One of the reasons for the success of the present invention is that a combination of a specific curled fiber and a specific fine fiber cannot be achieved with a combination of a curled fiber and another binder. It has been found that the material can be a material having a well-balanced low density and strength. It is essential that the low-density body used to form the water-resistant structure of the present invention contains a specific curled fiber and two components of a fine fiber having a bond reinforcing factor of 0.15 or more.

[0008] 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 due to a crosslinking reaction. A curled fiber having a wet curl factor in the range of 0.4 to 1.0 is used. When the curl fiber has a wet curl factor of less than 0.4, the bulkiness is small, and the density of the low-density body obtained by combining with the fine fiber is high. On the other hand, when the wet curl factor is larger than 1.0, the strength is reduced due to damage to the pulp fiber due to strengthening of the mechanical treatment at the time of imparting deformation to the pulp fiber, rather than the effect due to bulkiness. There are cases. By the way,
The wet curl factor is an index indicating the degree of deformation of a fiber in a wet state.
The actual length of the fiber after immersion in pure water (LA) and the maximum projected length of the fiber (the length of the longest side of the rectangle surrounding the fiber,
LB) was measured using a microscope, and [(LA / LB) −
1], which is a numerical value representing how much the fiber is curved from the original linear length of the fiber.

The reason why the wet curl factor, which indicates the state of curl in a wet state, is important is that no matter how high the curl factor in a dry state, if the wet curl factor is small, the curl will return due to wetting when the curl factor is low, This is because it is difficult to achieve the density. Wet curl factor 0.4 ~
The curled fiber in the range of 1.0 is bent by imparting a considerable amount of deformation to the pulp fiber, and is cross-linked, so that the fiber is rigid.・ The product obtained by drying becomes a low density body. However, in this material, the entanglement between fibers is weak, and the hydroxyl groups (-O
H) is reduced, so that hydrogen bonds due to hydroxyl groups are hardly generated, and the obtained one has weak interlayer strength,
Single systems cannot be put to practical use. Therefore, in the present invention, specific fine fibers are combined.

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. 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. As the carded fiber, those having a water retention of 25 to 65%, which is excellent in terms of drainage and drying speed and excellent in production efficiency, are preferable, but the present invention is not particularly limited to this.

The other fine fibers constituting the low-density body of the present invention are usually natural polymer fibers, synthetic polymer fibers or semi-synthetic polymer fibers, or those obtained by treating them. Fine fibers having a reinforcing factor of 0.15 or more are used. As natural polymer fibers, for example, unbleached or bleached chemical pulp, GP, TMP (thermomechanical pulp) obtained by kraft pulping, sulfite pulping, alkali pulping, etc. of softwood or hardwood.
Pulp fibers such as mechanical pulp, cotton pulp, linter pulp, waste paper pulp, etc .; cellulosic fibers such as bacterial cellulose; protein fibers such as wool, silk and collagen fibers; and complex sugars such as chitin / chitosan fibers and alginic acid fibers. Chain-based fibers and the like. 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 fibers include fiber fibers obtained by chemically modifying natural products, such as acetyl cellulose fibers.

Among these, 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, unbleached or bleached chemical pulp obtained by kraft pulping, sulfite pulping, alkali pulping or the like of softwood or hardwood, or mechanical pulp such as GP, TMP (thermomechanical pulp), cotton Fine fiber pulp obtained by mechanically treating pulp fibers such as pulp, linter pulp, and waste paper pulp by a wet method tends to have a branched shape, and the effect of increasing the 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 shear 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.

In the present invention, the binding enhancing factor (B)
F) is calculated by (E2−E1) / E1. Where E
1 was mixed with 50% by weight of bleached hardwood kraft pulp and 50% by weight of softwood bleached kraft pulp to form an aqueous slurry, beaten to 500 ml of Canadian Standard Freeness (CSF), and dewatered with a hand making machine according to JIS-P-8209. After air-drying to produce a sheet having a basis weight of 60 g / m ² ,
The figure shows the ultrasonic elastic modulus measured after heat treatment at 130 ° C. for 2 minutes and humidity control at 20 ° C. and 65% RH. E2 prepares an aqueous slurry by replacing 50% of the pulp fibers with fine fibers, and prepares a sheet in the same manner as the measurement of E1,
It shows the ultrasonic elastic modulus when measured.

In the present invention, the binding enhancement factor is 0.1
It is characterized by using 5 or more fine fibers, in which delamination and generation of paper dust are remarkably improved, and a desired low-density body can be obtained. When a fine fiber having a bond strengthening factor of less than 0.15 is used, the bond between the curled fibers becomes insufficient, and the resulting low-density body is liable to cause delamination and easily generate paper powder, which is not practically satisfactory. It becomes something. Preferably the binding enhancement factor is between 0.15 and 1.5
Are used, more preferably 0.20
A range of ~ 1.5 is used. In the present invention, fine fibers exceeding 1.5 can be sufficiently used in terms of quality, but the production cost of the fine fibers increases.

Regarding the size of the fine fibers obtained by mechanical treatment of the natural pulp fibers used in the present invention,
Although not particularly limited, the number average fiber length is 0.01
Those having a range of .about.0.80 mm are preferably used. Among them, those having a range of 0.05 to 0.60 mm are more preferable in terms of yield and dispersibility. 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. For this reason, the fiber width varies depending on the type of pulp fiber and the treatment method, and cannot be specified unconditionally, but usually a fiber width of 0.1 to 30 μm is preferably used. However, the present invention is not particularly limited thereby.

The fine fibers of the present invention preferably have a water retention value in the range of 150 to 500%. More preferably, it is in the range of 165 to 500%, particularly preferably in the range of 210 to 450%. When the water retention is less than 150%, the binding ability between the curled fibers is not sufficient due to insufficient binding ability of the fibers, and the low fiber obtained by the combination of the fine fibers and the curled fibers is insufficient. The density body has insufficient interlayer strength and tends to generate paper powder. In particular, when the low-density body is a sheet, the paper strength is insufficient, and it may not be practical depending on the use. On the other hand, when the water retention exceeds 500%, the production cost of the fine fibers increases.

The mixing ratio of the low-density curled fiber and the fine fiber of the present invention can be appropriately selected according to the purpose because the balance between density and 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, fine fibers are used in an amount of 3 to 65 per dry weight of all fibers.
3% by weight of curled fiber per dry weight of total fiber
When mixed and used at a ratio of 5 to 97% by weight, the balance between the density and the interlayer strength is particularly excellent and is preferable. Although it can be used depending on the application even outside the range, the fine fiber is 3% by weight.
If it is less than 10, the interlayer strength of the low-density body is insufficient, and paper dust is easily generated. On the other hand, when the content of the fine fibers exceeds 65% by weight, the tendency of the density increase is remarkable.

The low-density body of the present invention may contain, in addition to the above-mentioned specific curled fibers and fine fibers, organic synthetic fibers, inorganic fibers, paper-strengthening agents, water-proofing agents, water-repelling agents, Microcapsules, sizing agents, dyes, pigments,
Yield improvers, fillers, pH regulators, slime control agents, thickeners, preservatives, fungicides, antibacterials, flame retardants, preservatives, rodenticides, insect repellents, moisturizers, fresheners, deoxidizers ,
Microcapsules, foaming agents, surfactants, electromagnetic shielding materials, antistatic agents, rust inhibitors, fragrances, deodorants 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, rayon fiber, polyester fiber, polyamide fiber and the like. Degradable fibers are 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 fiber, for example, glass fiber,
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, and dry paper strength enhancers 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, the use of a wet paper strength enhancer is preferable because it has a significant effect on improving the strength of the low-density body as a base material in a water-wet state.

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 are each used alone or appropriately selected in combination of two or more. Addition of a water-proofing agent and a water-repellent agent is effective in increasing the water resistance of a low-density body. The mixing amount 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 foamable microcapsules are obtained by encapsulating a low-boiling solvent in resin fine particles.
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 in the present invention is usually prepared batchwise or continuously using an apparatus having a stirrer.
It is desirable that the carded fiber is not left in a wet state for a long time, but is defibrated as much as possible immediately before the production of the low-density body and mixed with the fine fiber. The reason is that although the curled fiber is less hydrophilic than normal 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. Therefore, aqueous slurry
Is preferably a continuous type which can be prepared according to 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 in addition, a mixed solution of water and an alcohol (such as methanol or ethanol), alcohol, acetone, ethyl acetate, glycerin,
And other organic solvents can be used. 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, 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 is usually prepared by a slurry method,
It can be obtained by the so-called wet method, but compared to the dry method,
Since the mixing of the fibers is likely to be uniform and the bonding strength due to the hydrogen bond between the fibers is increased, the generation of paper dust is extremely small.

The low-density body used to form the water-resistant low-density structure of the present invention, specifically, a sheet (sheet or board) or a molded body is exemplified. In the case of a sheet, it can be produced 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 usually 30 μm to 5 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.

The board is usually 5 mm to several cm thick and can be manufactured using the same paper machine as described above for the sheet. It can be laminated to form a thick material. In the case of a board, as in the case of a sheet, 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. 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. The molded body can also be obtained by processing the sheet or board by cutting, bonding, or the like.

As a net used for dewatering the slurry in a paper machine or a pulp mold manufacturing machine, a mesh having a mesh size of generally used such as 60 or 80 can be used. When the slurry concentration is low, a fine mesh 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.

The water-resistant low-density structure of the present invention is obtained by subjecting the low-density body obtained as described above to a water-resistant treatment or a water-repellent treatment. It is manufactured by a method of impregnating or applying a water repellent liquid, or a method of bonding a sheet or board having water resistance and water repellency.

The impregnation treatment with the water-resistant or water-repellent liquid can be roughly divided into two cases: impregnating only near the surface layer of the surface to be made water-resistant, and impregnating the entire low-density body. . Generally, when the whole is impregnated with the liquid,
The density of the water-resistant low-density structure tends to increase, and it is preferable to impregnate only near the surface because the cost is low. However, when strong water resistance is required, it is preferable to impregnate the liquid entirely.

In the case of impregnating the entire low-density body and continuously producing sheets and boards, the liquid is usually impregnated using an impregnating machine known in the papermaking industry, such as a pre-wet method, a float method, or a doctor bar method. After impregnation, a means for drying by an air floating system or the like can be used. In the case of a molded body, for example, a method of immersing the vats one by one in a vat filled with a liquid and then pulling up and drying can be adopted. However, the present invention does not particularly limit the impregnation method.

As a coating method, when sheets and boards are continuously produced, a method of performing on-machine size press or a method of applying with an on-machine or off-machine coater can be used. As the coating head, for example, an air doctor coater, a blade coater, a transfer roll coater, a bar coater, a reverse roll coater, a gravure roll coater, and the like, which are generally used in the production of coated paper, and a spray method can be used. In the case of a molded body, a method of spraying a low-density body with a spray, a method of painting with a brush, and the like can be used. However, the present invention does not particularly limit the coating method.

The coating method is a method in which the coating liquid penetrates into the inside of the low-density body less than the impregnation method, and the coating liquid component is more likely to remain on the surface. In order to suppress the penetration of the paint into the low-density body, it is effective to add a sizing agent and a paper-strengthening agent to the slurry in a larger amount than usual when producing the low-density body. A method of applying a surface sizing agent by a size press or the like is also effective.

The water-resistant or water-repellent liquid used for the impregnation or coating treatment includes rubber-based latex, resin-based latex, polybutadiene latex, vinylpyridine latex, polyethylene latex, urea formaldehyde resin, melamine formaldehyde resin, polyamide urea Formaldehyde resin, ketone resin, polyamide epichlorohydrin resin, polyamide polyamine epichlorohydrin resin, glycerol polyglycidyl ether resin, polyethyleneimine resin, dialdehyde starch, ammonium zirconium carbonate, waxes, higher fatty acid derivatives, silicons, fluorine compounds and the like are used. These may be used in combination of two or more.

Examples of the rubber latex include styrene-butadiene (SB, SBR), acrylonitrile-butadiene (NBR), methyl methacrylate-butadiene (MBR), chloroprene (CR), polyisoprene (PIR), and natural rubber. (NR), polyurethane (PU) and the like. As resin-based latex,
For example, acrylate (ACL), vinyl acetate (PVA)
c), ethylene-vinyl acetate (EVA), vinylidene chloride (PVDc) and the like. Examples of the wax include natural wax, petroleum wax, chlorinated paraffin, and the like.

In addition to the above compounds, if necessary, dispersants, surfactants, thickeners, binders, dyes, pigments, preservatives, fungicides, antibacterial agents, flame retardants, rodenticides, insect repellents, freshness preservation An agent, an oxygen scavenger, an electromagnetic shielding material, an antistatic agent, a rust inhibitor, a fragrance, a deodorant and the like can be selected and blended.
Addition of the binder and the thickener can prevent the liquid from excessively seeping into the low-density body, and are effective in improving the water resistance. The water-resistant or water-repellent liquid is used for impregnation or coating as a water-based, solvent-based, solvent-free, or hot-melt-based liquid.

When a crosslinking reaction type is mixed with the water-resistant liquid or the water-repellent liquid, it is preferable to further perform a heat treatment for accelerating the crosslinking after the drying step.

As a special impregnation or coating method,
There is a method using an ultraviolet or electron beam curable resin.
In the case of ultraviolet curing, the coating is composed of a premonomer (monomer or oligomer), a photoreaction initiator, a photosensitizer, a colorant, a storage stabilizer, an antioxidant, a dispersant, etc. In some cases, the coating is composed of premonomers (monomers or oligomers), colorants, storage stabilizers, antioxidants, dispersants, and the like. Generally, acrylates such as polyester acrylate, epoxy acrylate, polyurethane acrylate and polyol acrylate are often used as the premonomer. The amount of impregnation or application of the water-resistant liquid and the water-repellent liquid is usually in the range of 1 to 100 g / m ² in terms of solid content, but the present invention is not limited to this.

Furthermore, a method of imparting water resistance to the low-density body by attaching a sheet or board having water resistance and water repellency to the low-density body is superior to that obtained by the impregnation method or the coating method. A low-density structure having water resistance is obtained. The most common sheet used for this bonding is a synthetic resin film, but in addition, synthetic paper, a synthetic resin plate, water-resistant paper, water-repellent paper, metal foil such as aluminum,
Examples include a metal plate and a glass plate. In addition, a material obtained by laminating a plurality of the above materials may be used. As the synthetic resin film, for example, polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyamide imide, polysulfone, polycarbonate and the like biodegradable aliphatic polyester, cellulose derivative, Kitchen·
Chitosan and the like. Examples of the synthetic paper include polypropylene-based synthetic paper and polystyrene-based synthetic paper. Examples of the sheet include those having a thickness of several μm to several mm, and examples of the board include those having a thickness of several mm to several cm, but the present invention is not limited thereto.

The lamination can be performed manually, but a laminating machine such as a wet laminator, a dry laminator, a solventless laminator, a hot melt laminator, an extrusion laminator and the like are usually used. However, the present invention is not limited to this. Examples of the adhesive in the case where an adhesive is required for bonding include starch, a starch derivative, a cellulose derivative such as carboxymethyl cellulose, a protein such as casein, polyvinyl alcohol, vinyl acetate, and vinyl acetate-acrylate, which are aqueous adhesives. , Ethylene-vinyl acetate,
Emulsions of acrylic esters, butadiene-styrene, butadiene-acrylonitrile, butadiene-
Examples include latexes of methyl methacrylates and resin adhesives such as urea resins and melamine resins. In addition, a solvent-based adhesive such as vinyl acetate resin, vinyl chloride resin, and polyurethane isocyanate can be used. The coating amount is usually ² to 50 g / m ² .

The above-described processing for imparting water resistance is performed on a part of or the entire surface of the low-density body. At this time, the processing conditions and the processing method can be changed depending on the portion of the low-density body. The water repellency of the water-resistant or water-repellent treated surface of the water-resistant low-density structure of the present invention varies depending on the application, but is not limited thereto.
The water repellency specified in ISP 8137 is R8 to R10
Is desirably within the range. Those in this range are characterized in that swelling of pulp fibers due to moisture can be ideally prevented, and the range of application as a material is wide.

The water-resistant low-density structure obtained by the above method can be used as it is depending on the application, but can be used in various fields after further post-processing. For example, sheets or relatively thin boards can be used for paper containers such as paper cups and paper trays, water-resistant paper bags, buffer envelopes, frozen food cool bags, lunch mats, desk mats, and the like. The board can be used for civil engineering / architecture structures, display boards, photographic panels, and the like. Further, by processing into a box form, a box requiring water resistance, cushioning property, and heat insulation, such as a return box or a fish box, is obtained. still,
Depending on the application, a portion having poor water resistance and water repellency such as a cut surface poses a problem. In this case, after post-processing such as cutting, joining, and forming, a water-resistant / water-repellent treatment is further performed. Printing on the water-resistant low-density structure of the present invention can be performed before or after the water-resistant / water-repellent treatment.

[0047]

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 80% of glass beads having an average particle diameter 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 300 ml / min, fine fibers having a number average fiber length of 0.26 mm and a bond reinforcing factor of 0.58 were obtained. The water retention of this fine fiber was measured and was 293%. Water was added to a mixture of 10 parts of this fine fiber and 90 parts of a commercially available curled fiber (trade name: NHB405, manufactured by Warehauser, USA) having a curl factor of 0.70 and a water retention of 48%. It was adjusted to 2% and stirred sufficiently to obtain a fiber slurry. A 1.0% sulfuric acid band based on pulp was added to the slurry, the pH was adjusted to 6.5 with baking soda, and then cationized starch (trade name: Ace K100, manufactured by Oji Cornstarch) dissolved in hot water was added. Pulp 1%, neutral sizing agent (trade name: A
S-262, manufactured by Nippon PMC Co., Ltd.) was stirred while sequentially adding 3% to pulp and a wet strength agent (trade name: WS-570, manufactured by Nippon PMC Co., Ltd.). This slurry is used as a stock, and is a square (25) having an 80 mesh bronze wire.
(cm × 25 cm) A wet sheet having a basis weight of 60 g / m ² was formed on a wire of a hand-made sheet machine, and was restrained and dried with a hot air dryer at 105 ° C. without applying a wet press to obtain a sheet. The basis weight of the sheet after moisture conditioning under an environment of 20 ° C. and 65% RH until the weight became constant was 62.3 g /
m ² and density were 0.10 g / cm ³ . Subsequently, a fluorine-based coating agent (trade name: AG-) was applied to this sheet using an applicator bar having a clearance of 50 μm.
530, solid content concentration 15%, manufactured by Asahi Glass Co., Ltd.)
It was coated in such a way that m ^2. After restraining the sheet and drying it with a blow dryer, the sheet was placed in an oven at 100 ° C. and subjected to a heat treatment for 1 minute. After moisture-conditioning the coated paper obtained as described above, the basis weight and the density were measured, and a water repellency test was performed for evaluation. Table 1 shows the results. Hereinafter, evaluation methods for the properties of the used fine fibers, curled fibers, and the obtained sheets and the like will be described.

[ Measurement Method [ Measurement Method of Bond Reinforcement Factor of Fine Fibers]] 50 parts of bleached hardwood kraft pulp and 50 parts of softwood bleached kraft pulp were mixed and adjusted to a concentration of 2%. ) And beaten to a Canadian standard freeness (CSF) of 500 ml. Take 3.7 g of this paper stock absolutely dry and add 150 g without adding chemicals.
Square wire (25cm × 25c) using mesh wire
m) A sheet is formed by a hand making machine, and after a coaching process, a wet press is performed for 5 minutes (first press) and 2 minutes (second press) at a pressure of 3.5 kg / cm ² according to a conventional method. After that, drying was carried out at room temperature by a blast dryer between the 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 heated at 20 ° C. and 65% RH.
It was conditioned. On the other hand, 3.7 g of absolutely dry 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.
% 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: S
The elastic modulus (GPa) of the sheets 1 and 2 was measured by measuring the ultrasonic wave propagation velocity using ST-210A). The elastic modulus (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] The number average fiber length was measured by a Kayani fiber length measuring instrument (model: FS-200).

[Method of measuring water retention] Water retention was measured by JAPAN
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 absolutely dry paper stock and 100 ml of distilled water
The mixture was sufficiently dispersed therein and allowed to stand at room temperature for 24 hours to be sufficiently impregnated with water. Then, the stock is collected on a filter,
Next, the mixture was placed in a centrifuge tube of a centrifuge (model: H-103N, manufactured by Domestic Centrifuge Co.) having a glass filter of G2,
The mixture was centrifuged and dehydrated at 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. In the case of fine fibers, the solid content concentration 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 the same as above. , And the water retention was calculated from the wet weight and the dry weight 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.

[Measurement Method of Wet Curl Factor of Curled Fiber] The value of 1 after immersion in distilled water at room temperature for 24 hours.
The 00 curled fibers are placed on a glass microscope slide, and the actual (linear) length LA (μm) and the maximum projected length (surrounding the fibers) of each fiber are determined using an image analyzer. The length of the longest side of the rectangle is equal to) LB (μ
m) was measured, the wet curl factor was determined from the following equation, and the average value was used. Wet curl factor = (LA / LB) -1

[Physical Properties] The obtained sheet had a basis weight of JIS P 8142 and a thickness and density of JISP 811.
8. The water repellency was determined based on JIS P 8137, and the tensile strength (break length) was determined based on JIS P 8113. In the case of a board or a molded article, the measurement was carried out according to these.

Example 2 70 parts of the commercially available curled fibers and 10 parts of fine fibers used in Example 1 were mixed with unbeaten softwood bleached kraft pulp 20
Parts, and water was added to dilute to a solid concentration of 2%.
The mixture was sufficiently stirred to obtain a fiber slurry. Using this slurry as a stock, a wet sheet is formed on a wire of a square (25 cm × 25 cm) hand-made sheet machine equipped with an 80-mesh bronze wire, and after a coaching treatment, 3.5 kg / cm ² according to a conventional method. A wet press was applied, followed by restraint and blast drying to obtain a base paper. After humidification, the sheet has a basis weight of 102.5 g / m ² and a density of 0.25.
g / cm ³ . Further, this base paper was treated with a fluorine resin emulsion (trade name: AG-533, solid content concentration 1).
(8%, manufactured by Asahi Glass Co., Ltd.) was impregnated by passing a solution diluted 10-fold with water through an experimental etching processor filled in a vat, followed by constraint drying with a hot air dryer at 105 ° C. Subsequently, the sheet was placed in an oven at 120 ° C. and heat-treated. Table 1 shows the results of the basis weight, density, and water repellency of the sheet after humidity control. In addition, a circle having a diameter of 4 cm and a fan-shaped sheet are cut out from the sheet one by one, and are laminated using a commercially available vinyl acetate resin emulsion adhesive (trade name: Bond for woodwork, manufactured by Konishi). As a result, a paper cup having an upper inner diameter of 5 cm and a lower inner diameter of 4 cm was produced. When the paper cup was filled with water and allowed to stand for 24 hours, there was no liquid leakage.

Example 3 The same slurry as in Example 1 to which a chemical was added was prepared as a raw material slurry. A raw material equivalent to 55 g of absolutely dry was taken from this slurry, dehydrated by the same square-shaped hand making machine as in Example 1, and a wet board was formed on the wire. The wet board was transferred from a wire onto a stainless steel plate having a myriad of 3 mm holes covered with filter paper and dried at 105 ° C. in a blow dryer as it was. After drying, 20
The weight of the board after humidity control at 65 ° C. and 65% RH is 57.
4 g, the thickness was 10 mm, and the density was 0.09 g / cm ³ . From this board, 7
4 boards of size 0mm x 70mm and 80mm x
One 80 mm board was cut out. Then, 8
A commercially available vinyl acetate resin emulsion adhesive (trade name: Bond for woodworking, manufactured by Konishi Co., Ltd.) is used to attach the 80 mm × 80 mm board so that the 0 mm square board is on the bottom and the 70 mm square board is on the side. A cube (box) having an upper surface of × 80 mm and open was prepared. After the adhesive is dried, using a spray gun, a silicone water repellent (trade name: TSW831, manufactured by Toshiba Silicone Co., Ltd.) and this catalyst (trade name: CW80, manufactured by Toshiba Silicone Co., Ltd.)
Was mixed at a volume ratio of 1: 1 and sprayed uniformly over the entire inside and outside of the box so as to have a coating amount of 50 cc / m ² . Next, the box was placed in a blow dryer at 105 ° C., pre-dried for 10 minutes, and then placed in an oven at 160 ° C. for 2 minutes to perform a heat treatment. Table 1 shows the density and the water repellency of the surface of this box after humidity control.

Example 4 An aqueous slurry of bleached hardwood kraft pulp having a solid content of 2.5% was repeatedly treated with a 12-inch refiner (manufactured by Kumagaya Riki Kogyo Co., Ltd.) to give CSF (Canadian Standard Freeness) 2
20 ml of beaten pulp were obtained. The number average fiber length of this fiber was 0.38 mm, the bond reinforcing factor was 0.17, and the water retention was 158%. 40 parts of the beaten fiber and 60 parts of the commercially available curled fiber used in Example 1 were mixed,
After diluting with water to a solid content concentration of 2%, the mixture was stirred to obtain a sufficiently dispersed fiber slurry. A board was prepared in the same manner as in Example 3 except that the chemicals added in Example 1 were added to this slurry at the same addition rate, and 75 g of the absolute dryness of the mixed slurry was used as a raw material. After drying and humidity control, the board had a thickness of 6.1 mm and a density of 0.21 g / cm ³ . A commercially available synthetic paper having a thickness of 115 μm (trade name: YUPO FCG110, manufactured by Oji Yuka Synthetic Paper Co., Ltd.) and a commercially available chloroprene rubber-based adhesive (trade name: G
17, manufactured by Konishi Co., Ltd.), and cut into a size of 20 cm × 20 cm with a cutter knife to produce a square board. Table 1 shows the density and water repellency of this structure.

Example 5 A 1.5-liter Dynomill (model: KDL-PIL) filled with 80% of glass beads having an average particle diameter of 2 mm was filled with an aqueous slurry of bleached 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 number average fiber length of 0.32 mm, a bond reinforcing factor of 0.43, and a water retention of 223% were obtained. 40 parts of these fine fibers,
A mixed slurry was prepared in the same manner as in Example 1 except that 60 parts of the commercially available curled fiber used in Example 1 was mixed and used as a raw material. Subsequently, an outer width of 190 mm and a total length of 1 attached to a small pulp mold molding machine (model: SDM type, manufactured by Noritake Company)
A molding die for a flat bottom tray having a size of 60 mm × a depth of 40 mm was immersed in the above-mentioned slurry that had been sufficiently stirred, and then vacuum-suctioned to adsorb the pulp in a stacked manner on the molding die. Next, the mold is pulled up from the slurry, and the suction is continued by inverting the mold by 180 degrees, and then the vacuum suction mold is placed on the pulp mold from above, and at the same time, the vacuum pressure of the molding mold is reduced to zero and the pulp mold is removed. Was transferred to the mold. Next, the pulp mold was removed from the mold, dried with far infrared rays and hot air, and the obtained pulp mold flat bottom tray having a thickness of 8 mm was conditioned at 20 ° C. and 65% RH. Next, Example 3
The same pulp mold as above was processed with a silicone water repellent. Table 1 shows the density of the obtained pulp mold after humidity control and the degree of water repellency of the surface.

Example 6 A base paper of 60 g / m ² was prepared in the same manner as in Example 1 except that 32 parts of curled fiber and 68 parts of fine fiber used in Example 1 were used. A coating process of -530 was performed. Table 1 shows the density and water repellency of this sheet after humidity control.

Comparative Example 1 A sheet was prepared in the same manner as in Example 1 except that a raw material slurry was prepared only from curled fibers without using fine fibers. However, the wet paper sheet was not peeled off from the wire. A sheet could not be made.

Comparative Example 2 The density and water repellency of the base paper before coating in Example 1 were measured.

Comparative Example 3 Softwood bleached kraft pulp
0.5 g of phosphorus (manufactured by Wako Pure Chemical Industries, Ltd.) in isopropanol
Solution dissolved in 20 ml, 5% sodium hydroxide
20 ml of the solution and water were added to make the total amount 250 g,
Mix well. This mixture was placed in a 1-liter double-arm
(Model: S1-1, manufactured by Moriyama Seisakusho), room temperature
Rotate both arms at 60rpm and 100rpm respectively
And stirred for 5 minutes. Subsequently, the mixture is
Place in a heat-resistant plastic bag and seal at 80 ° C for 30 minutes.
A minute heat treatment was performed to crosslink. Then left in the pulp
After washing the alkali well with water, use a Buchner funnel
Concentrate to 20% solids, loosen the fibers well
It was put into a blow dryer at 0 ° C. and dried for 1 hour. This
After removing the dried pulp from the dryer and cooling it,
The pulp mass is disintegrated with a burger blender
It was turned off. Curled fiber obtained in this way
-Has a wet curl factor of 0.35 and a water retention of 113
%Met. The curled phi obtained as above
Replace 70 parts of bar with 70 parts of commercially available curled fiber.
The basis weight was 60 g in the same manner as in Example 2 except that
/ M ^TwoAfter making the base paper of
Then, a sheet was obtained. Density and repellency of this sheet after humidity control
Table 1 shows the water degrees.

Comparative Example 4 The density and water repellency of the surface of the board of Example 3 before spraying with the silicone water repellent were measured. Table 1 shows the results.

[0063]

[Table 1]

As is clear from Table 1, the water-resistant low-density structures of Examples 1 to 5 have a sufficiently low density, have a surface exhibiting water repellency of R8 or more, and have desired water resistance. Met. The density can be changed by changing the combination of the curled fiber and the fine fiber, or by mixing other fibers (Examples 1 and 2). Further, a paper cup can be manufactured using the water-resistant low-density structure of the present invention (Example 2), and a water-resistant box can be manufactured (Example 3). The water-resistant low-density structures of Examples 1 to 3 are obtained by impregnating and applying a water-resistant and water-repellent liquid to a low-density body, while Example 4 is obtained by bonding a water-resistant sheet. It is a thing. Further, the water-resistant low-density structure of the present invention can also be obtained by processing a low-density body produced by a pulp molding method (Example 5).

On the other hand, even if an attempt is made to produce a sheet using only the curled fibers, the fiber bond between the curled fibers is not sufficient, and the sheet strength is low (Comparative Example 1). Further, even if a low-density sheet is produced by appropriately blending curled fibers and fine fibers, the water resistance is insufficient unless water-resistant treatment is performed (Comparative Examples 2 and 4).

[0066]

According to the present invention, there is provided an effect of providing a low-density water-resistant structure using pulp as a main raw material.

Claims (6)

[Claims] 1. A wet curl factor of 0.4 to 1.0.
Water-resistant and / or water-repellent treatment is applied to a low-density body containing a curled fiber having a binding reinforcing factor of 0.15 or more and a fine fiber having a bonding reinforcement factor of 0.15 or more. Structure. 2. The water resistance according to claim 1, wherein the water repellency of the surface of the structure subjected to the water resistance and / or water repellency treatment specified in JIS P 8137 is in the range of R8 to R10. Low density structure. 3. The water resistance according to claim 1, wherein the curled fiber is contained in a proportion of 35 to 97% by weight based on the total dry weight of the fibers, and the fine fibers are contained in a proportion of 3 to 65% by weight based on the total dry weight of the fibers. Low density structure. 4. The low-density body has a density of 0.05 to 0.45.
water resistant low density structure according to claim 1 wherein the g / cm ^3. 5. The water-resistant low-density structure according to claim 1, wherein the low-density body is in a sheet form. 6. The water-resistant low-density structure according to claim 1, wherein the low-density body is a molded body.