JP2002201598A - Forming base paper and paper forming container using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulp containing a pulp as a main component, which is suitable for press molding, which has good moldability in which cracks and unevenness of folding wrinkles do not occur during press molding and high productivity. To provide a molded base paper. Further, the present invention provides a paper drawn container (deep drawn container) applicable to applications such as relatively deep trays and cups. In particular, the present invention provides a paper drawn container having excellent flange smoothness. In addition, it is deep drawn,
It is lightweight and does not cause blistering or blistering of the container.
Provide a highly rigid paper container. A base paper that satisfies the following four conditions: Tensile strength (JIS-P8113) is 2.0 kN / m
that's all. Elongation at break (JIS-P8113) is 1.5% or more. Critical compressive stress defined by the following equation is 1 to 10MP
a range. Critical compressive stress = A / B where A indicates the compressive strength according to JIS-P8126, and B indicates the load area of the test piece at the time of measuring the compressive strength. The amount of compressive deformation when a compressive stress of 20 kgf / cm ² is applied in the thickness direction is 10% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded base paper used as a material of a packaging container for packaging industrial products and the like. Further, the present invention relates to a molded base paper which is a raw material of a container for storing fresh food products such as meat, vegetables, and fresh fish, or various processed foods such as lunches, prepared dishes, frozen foods, confectioneries, and noodles. More specifically, the present invention relates to a molded base paper having a low environmental load at the time of disposal and having characteristics particularly suitable for press molding.

[0002]

2. Description of the Related Art Conventionally, plastic containers have been used in large quantities as food containers or packaging materials for various industrial products because of their ease of molding, mass production, and inexpensive production. As these plastic containers, for example, foamed polystyrene beads obtained by molding or foaming polystyrene sheets by press molding, styrene foam containers, polypropylene containers, polyethylene terephthalate containers, polyvinyl chloride containers and the like are widely used. However, the plastic container as described above has a problem that the burden on the environment at the time of disposal is high. In other words, it is not decomposed semi-permanently when it is landfilled and remains in the ground, and when it is incinerated, it burns easily because of the high calorie burn, and it is difficult to completely burn it. Has a problem that hydrogen chloride gas which is highly corrosive may be generated.

Therefore, in recent years, in consideration of environmental problems, recycling problems, and resource saving, as an alternative to the above-mentioned plastic container, it is possible to recycle, to burn less calories when discarded, and to have biodegradability. There is a need for a container made of pulp having a low environmental load.
BACKGROUND ART As a molded article having a three-dimensional shape made of pulp or a material mainly composed of pulp, there has conventionally been a pulp mold container. Pulp mold containers have long been widely used as packaging containers. The method for manufacturing a pulp mold container is to prepare a mesh having a concave-convex shape corresponding to the intended container shape, suction-pulp the pulp slurry into the mesh, and dry the pulp raw material into a desired shape. It is a molding method. Therefore, the container shape obtained by this method has a high degree of freedom. However, the production of pulp mold takes time and there is a problem in productivity. Further, it has been difficult to provide pulp mold containers with sufficient water resistance and oil resistance often required for food tray containers, and this has been accompanied by an increase in cost.

As a method of obtaining a molded product mainly composed of pulp other than pulp mold, a method of press-molding a base sheet mainly composed of pulp such as paperboard while heating is known. In this method, a base sheet having a ruled line previously inserted between a male and a female mold is loaded and press-formed by hot pressing. In such a press molding method, since a molded body can be obtained by one press, productivity is very high. However, unlike resins and metals, base sheets mainly composed of paper pulp generally have poor stretchability, spreadability, and stretchability. Therefore, if deep press molding is performed to form a tray having a certain depth, the base sheet may not be able to withstand the stretching and may be broken. Therefore, when using normal paperboard etc. as the base material,
Only a molded container having almost no depth such as a so-called paper plate could be manufactured, and the shape of the obtained molded body was very limited. Even if no break occurs, it is difficult to make a step at the fold of the ruled line or to smooth the surface of the container. In addition, when a step is generated at the edge of the container of the tray, a gap of the step is formed when a lid is attached or when sealing with a film or the like is performed. Was. Further, the breaking point originating from the fold of the paper causes a reduction in the strength of the tray.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. Hei 5-28623 discloses a method in which a corrugated paper provided with a large number of corrugated bent portions in a paper material and given stretchability is heated and pressed in a mold. Japanese Patent Application Laid-Open No. 6-134898 discloses a method of press-molding a paper material provided with stretchability by forming irregularities over the entire surface and imparting stretchability while heating the material after heating.
No. 5 discloses a method of laminating a plurality of humidified base papers via an adhesive, followed by corrugating and then press forming. However, in these methods, the base sheet is pre-wrinkled in a corrugated shape or the like in advance so as to have stretchability, and press working is performed after imparting press workability. Therefore, not only a wrinkling process is required before press working, but also wrinkles are present in the whole container after press working, which not only impairs aesthetic appearance but also is insufficient in strength. Also,
Japanese Patent Application Laid-Open No. 7-315358 discloses a method in which a corrugated cardboard sheet is press-formed while being heated in a metal mold. This method uses a corrugated cardboard sheet as a base material and absorbs a certain amount of distortion due to press working by its flute structure. It is to let. However, this method requires the use of a corrugated cardboard sheet as the substrate sheet, and is not applicable to a general substrate such as paperboard. Moreover, the unevenness of the wrinkles generated by the press working was not sufficiently absorbed. Japanese Patent Application Laid-Open No. Hei 6-239334 discloses a method of press-molding a sheet obtained by adding an olefin resin to pulp fibers and imparting stretchability.
There is disclosed a method of hot press-molding a sheet having improved stretchability by mixing a thermoplastic resin fiber and a pulp fiber. However, these methods are intended to impart press workability to the base sheet by adding a thermoplastic resin to the base sheet mainly composed of paper, and the recyclability of the paper base, It impairs characteristics such as low environmental load.

In the case of a base sheet obtained by the above-mentioned method, when a molded product obtained by press-pressing these has a curved surface portion with a large distortion, the folded wrinkle portion generated on this curved surface has large irregularities. Even after pressing, the surface was not smooth, and the moldability was not good.

[0007] Further, in order to use the content containing a large amount of water, or a liquid such as a beverage, a soup, or a container for cup noodles, the content is more than the tray shape. Plastic molded containers and cup molded containers having tall sidewalls have been used.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to be suitable for press molding which has good moldability in which cracks and unevenness of folding wrinkles do not occur during press molding and high productivity. And a molded base paper mainly composed of pulp. An object of the present invention is to provide a draw-formed container made of paper (deep drawn container) applicable to applications such as relatively deep trays and cups. In particular, the present invention provides a paper drawn container having excellent flange smoothness. Further, the present invention provides a paper container having high rigidity, which is formed by deep drawing, is lightweight, and does not cause the swelling or bottom swelling of the container.

[0009]

The present invention has the following arrangement to solve the above-mentioned problems.

That is, a first aspect of the present invention is the following 4)
This is a base paper that satisfies two conditions. Tensile strength (JIS-P8113) is 2.0 kN / m
that's all. Elongation at break (JIS-P8113) is 1.5% or more. Critical compressive stress defined by the following equation is 1 to 10MP
a range. Critical compressive stress = A / B where A indicates the compressive strength according to JIS-P8126, and B indicates the load area of the test piece at the time of measuring the compressive strength. The amount of compressive deformation when a compressive stress of 20 kgf / cm ² is applied in the thickness direction is 10% or more.

A second aspect of the present invention is the base paper for forming according to the first aspect of the present invention, which comprises mechanical pulp as a raw material pulp for the base paper for forming.

A third aspect of the present invention is that a density of 0.7 to 0.9 g /
dense layer of cm ^3, and density 0.7 g / cm have less than ³ low-density layer, a basis weight is 100 to 500 g / ^{m 2,} the overall density of 0.4 to 0.7 g / cm ³ and, The low-density layer is a formed base paper mainly composed of pulp selected from at least one of mechanical pulp, curled fiber, and mercerized pulp.

A fourth aspect of the present invention is the molded base paper according to the third aspect of the present invention, wherein the low-density layer mainly comprises mechanical pulp.

A fifth aspect of the present invention is a formed base paper according to any one of the first to fourth aspects of the present invention, wherein a paper sheet having a breaking elongation (JIS-P8113) of 5% or more is laminated on at least one surface.

A sixth aspect of the present invention is that at least one of the outer layers is a high-density layer, and the elongation at break of the outer layer (JIS-P811).
3) The molded base paper according to the third or fourth aspect of the present invention, wherein the content is 5% or more.

A seventh aspect of the present invention is a paper-made container using the base paper for forming and processing according to the first to sixth aspects of the present invention.

An eighth aspect of the present invention is the paper-made container according to the seventh aspect, which is formed by drawing.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION As the natural pulp fiber constituting the base paper for forming according to the present invention, wood fiber (chemical pulp, mechanical pulp), non-wood fiber, waste paper pulp and the like are optionally used as required. Among the wood fibers, examples of the chemical pulp include kraft pulp using caustic soda and sodium sulfide during wood chip digestion, and sulfite pulp using sulfurous acid and bisulfite. These pulp may be unbleached or bleached. Also,
As mechanical pulp, ground wood pulp (GP) obtained by grinding logs with a grinder, refiner ground wood pulp (RGP) obtained by grinding (refining) waste wood from a sawmill, and wood chips are used. Thermomechanical pulp (TMP) obtained by heating and refining treatment is exemplified. Among these mechanical pulps, TMP is most suitable in terms of bulkiness and strength of the sheet. As TMP, wood chips are chemically treated and then refined under pressure.
-TMP, and further, BC-TMP and the like subjected to bleaching treatment. Also, of these wood fiber pulp,
Pulp with a long fiber length obtained from conifers such as pine, larch, cedar, fir, cypress and the like is suitably used for improving the stretchability and strength of a paper sheet. Further, pulp having a short fiber length obtained from hardwood such as hippo, beech, maple, elm, chestnut and the like can be used in combination as long as the effects of the present invention are not impaired.

The non-wood fibers usable in the present invention include bast fibers such as cucumber, mitsumata, ganpi, flax, thyme, kenaf, choma, jute, sun hemp, and seed hair fibers such as cotton and cotton linter. And leaf fibers such as manila hemp, sisal, esparto, bamboo,
Stem fibers such as rice straw, wheat straw, sugarcane bagasse and the like. In particular, mulberry, mitsumata, kenaf, manila hemp, sisal, cotton, cotton linter, etc.
Since the fiber length is long and the stretchability and strength of the base paper of the present invention can be improved, it is preferably used. The digestion of non-wood fibers can be performed in the same manner as wood fibers.

The waste paper pulp usable in the present invention includes:
Used corrugated paper, used magazine paper, etc., especially corrugated used paper, which can improve the stretchability and strength of the paper sheet, are preferably used.

These pulp fibers may be used alone or
More than one type can be used in combination. In addition, synthetic resin fibers can be mixed as needed within a range that does not impair the effects of the present invention. Examples of the synthetic resin fibers that can be used include polyethylene fibers, polypropylene fibers, polyamide fibers, polyethylene terephthalate fibers, and polybutylene terephthalate fibers.

<Description of First and Second Inventions> The base paper formed from the pulp fibers has a tensile strength (JI
(S-P8113) is preferably 2.0 kN / m or more, and the elongation at break (JIS-P8113) is preferably 1.5% or more. If the tensile strength of the forming base paper is lower than 2.0 kN / m or the breaking elongation is lower than 1.5%, the stretchability is low and the sheet is broken during press forming, which is not suitable. In order to control to the above range, in the case of a single layer, one of the pulp
Known methods such as using NBKP in the part, or adjusting the blending amount of the paper strength enhancer, or forming the paper layer into multiple layers and using NBKP in at least one of the layers or blending the paper strength enhancer. Control method.

In the case where the press-formed body has a curved portion having a large distortion, it is necessary to absorb the distortion by forming a folding wrinkle in the curved portion at the time of press molding. At this time, the folded wrinkles are folded in a plane direction like an accordion to form irregularities, and then the irregularities are compressed in the thickness direction by pressing. For this reason, in order to obtain good formability, it is preferable that the critical compressive stress is in the range of 1 to 10 MPa and the compressibility in the thickness direction is in the range of 10% or more. Note that the compression ratio in the present invention is a load of 20 kgf / cm.
² shows the compressibility in the thickness direction when a compressive stress of ² is applied.
When the critical compressive stress exceeds 10 MPa, the folded wrinkle portion is not sufficiently folded, and when the compression ratio is lower than 10%, compression molding of the folded wrinkle portion becomes insufficient, and good moldability cannot be obtained.

In order for the critical compressive stress and the compressibility in the thickness direction to be within the above ranges, it is necessary to lower the density of the paper sheet. For this purpose, it is preferable to use rigid pulp fibers. Generally, pulp fibers are beaten (a mechanical external force is applied to the pulp fibers to fibrillate a part of the cell wall of the fibers) to obtain a paper sheet having a uniform formation.
The beating must be mild to maintain the stiffness of the fiber. As the degree of beating, for example, in the case of chemical pulp, freeness (Tappi T-227 Canadian standard type)
Is more than 500mlcsf, 180ml for mechanical pulp
500ml for hemp pulp and kenaf pulp
csf or more, 500mlcs for corrugated waste paper pulp
Those having f or more are preferable. A beater, a conical-type refiner, a drum-type refiner, a disk-type refiner, or the like is used for beating pulp fibers.

In addition, within a range that does not impair the effects of the present invention,
It is also possible to lower the sheet density by mixing a foaming agent into the sheet. As the foaming agent, a heat-expandable microcapsule in which a low-boiling-point solvent is sealed in a microcapsule can be used. This capsule is about 4 to 5 times in diameter and 50 to 1 in volume by heating for a short time at a relatively low temperature of 80 to 200 ° C.
These particles have an average particle diameter of 10 to 30 μm that expands 00 times. Its composition consists of volatile organic solvents (swelling agents) such as isobutane, pentane, petroleum ether, hexane, low-boiling halogenated hydrocarbons and methylsilane, vinylidene chloride,
Acrylonitrile, wrapped with a thermoplastic resin made of a copolymer such as acrylate, etc.When the capsule is heated above the softening point of the polymer, the membrane polymer begins to soften, and the vapor pressure of the contained expanding agent is reduced. As it rises, the membrane expands and the capsule expands. Such a foaming agent is added to the pulp slurry, and foams by heating and drying during paper sheet making, or foams by passing a sheet containing the foaming agent through high-temperature water. In addition, a lightweight inorganic pigment such as a shirasu balloon may be added to the pulp slurry during paper sheet making to reduce the sheet density.

As the papermaking chemicals to be added to form the base paper of the present invention, the same sizing agent, paper strength agent, retention agent and the like as used in ordinary papermaking may be used as necessary. it can. For example, internal sizing agents such as alkyl ketene dimer, styrene acrylic resin, and rosin are used as the sizing agent. Further, as a paper strength agent and a retention aid, polyacrylamide resin, polyamide epichlorohydrin resin, polyethyleneimine and derivatives thereof, polyethylene oxide, polyamine, polyamide, polyamidepolyamine and derivatives thereof, cationic and amphoteric starch, starch oxide, carboxymethyl Organic compounds such as modified starch, vegetable gum, polyvinyl alcohol, etc., and inorganic compounds such as sulfate band, alumina sol, colloidal silica, bentonite and the like can be used in appropriate combination. It is also possible to add these by spraying between paper layers during the papermaking process, or by coating the base paper surface during or after papermaking.

In the present invention, a filler can be added during papermaking. As filler, talc, kaolin,
Mineral fillers such as calcined kaolin, clay, diatomaceous earth, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, magnesium sulfate, silica, aluminosilicate, bentonite, and organic materials such as polystyrene particles and urea formalin resin particles A synthetic filler or the like can be appropriately selected and used. These may be used arbitrarily in combination.

Further, papermaking additive aids such as dyes, pH adjusters, slime control agents, defoamers, and tackifiers can be used as appropriate depending on the intended use. The pH during papermaking of the present invention can be arbitrarily selected as needed, from around 4.5 for acidic papermaking to about 6 to 8 for neutral papermaking.

A slurry of the raw materials and chemicals made of the above-mentioned materials is paper-made by a conventional method. The papermaking may be any of ordinary fourdrinier paper machine, circular net paper machine, short net paper machine, inclined paper machine, various combination paper machine, and the like, and is not particularly limited. In addition, drying may be performed by any of ordinary multi-cylinder dryers, Yankee dryers, through dryers, and the like, and is not particularly limited. In the present invention, the formed base paper obtained from the papermaking step may be not only a single layer but also a laminated paper having two or more layers.

The basis weight of the base paper thus obtained is preferably in the range of 100 to 500 g / m ² , more preferably in the range of 200 to 400 g / m ² . If the basis weight is less than 100 g / m ^{2, the} molded article obtained after press molding does not exhibit sufficient strength, and if the basis weight exceeds 500 g / m ² , the formability of the folded wrinkles is undesirably reduced.
According to the above-mentioned method, paper satisfying the requirements of the present invention can be produced. between the two outer layers of 0.9 g / cm ^3, having a middle layer of a density less than 0.7 g / cm ³ consisting mainly of mechanical pulp, using a multi-layer sheet of density 0.4 to 0.7 g / cm ³ Is most preferred.

<Description of Third and Fourth Inventions> In order to manufacture a light-weight, highly rigid deep drawn container which does not swell at the trunk or at the bottom, a low-density layer having a density of less than 0.7 g / cm ³ , It is a multilayer paper having two or more layers including a high-density layer of 0.7 to 0.9 g / cm ³ , and has an overall density of 0.4 to 0.7.
g / cm ³ of paper is used. Low-density layer is preferably has a density 0.2 to 0.6 g / cm ^3.

The multi-layer paper according to the third and fourth aspects of the present invention may have one low-density layer and one high-density layer. More preferably, both outer layers on the front and back are high-density layers. Is more effective in obtaining a bulky and highly rigid base paper.

The stiffness S of a sheet such as paper, paperboard, etc. is given by: S = EI / B / W = ET
^{3/12 · W, (E} : Young's modulus MPa, I: moment of inertia of N · ^cm 2, B: sample width mm, W: sample weight k
g, T: sample thickness mm). That is, the stiffness S can be considered to be proportional to the cube of the Young's modulus and the sheet thickness.

Further, the stiffness of a sheet having a multilayer structure such as a paperboard can be measured according to Tappi Nov, 1963, Vol. 4
6, no. 11A. T. According to Luey, the stiffness value of each layer is obtained from the Young's modulus of each layer and the second moment of area using the above-described formula, and the stiffness value of the entire sheet is obtained by the sum of the stiffness values of each layer. Based on this concept, the greater the distance from the center of the thickness of the paper, that is, the greater the thickness of the paper, the more rigidity can be obtained. Therefore, the middle layer may be made bulky. In addition, since the stiffness is represented by the product of the cube of the thickness and the Young's modulus, the higher the Young's modulus of the outer layer, the more effective the improvement of the stiffness.

From this, the density of the middle layer is 0.7 g / c
m ^3, more preferably 0.2 to 0.6 g / cm ^3. More preferably, it is 0.3 to 0.5 g / cm ³ . Severe decrease in interlaminar strength when the density of the middle layer to less than 0.2 g / cm ^3, also exceeds 0.7 g / cm ^3, that the density of the whole base paper and 0.4 to 0.7 g / cm ³ Can not. In the third and fourth aspects of the present invention, the outer layer needs to have a density of 0.7 to 0.9 g / cm ³ . If it is less than 0.7 g / cm ³ , the Young's modulus of the outer layer decreases, and the improvement in rigidity of the present invention cannot be expected. When the density exceeds 0.9 g / cm ³ , the surface of the outer layer of the base paper becomes too tight, so that it is practically difficult to obtain a higher density layer at the papermaking stage, and it is also difficult to obtain a press. No formability is involved.

There are no particular restrictions on the type of pulp used for the high-density layer. However, it is particularly desirable to use a material such as NUKP, NBKP, etc., which has a high degree of beating of pulp of N material (softwood) so as not to lose its rigidity. . In order to make the present invention effective, the basis weight of the outer layer as a high-density layer is 15 to 10
It is preferably 0 g / m ² . That is, if it is less than 15 g / m ² , it is difficult to obtain a layer having a high Young's modulus, and it is also difficult to make paper itself. On the other hand, when the outer layer is 100
g / m ² , the basis weight of the low-density layer relatively decreases, so that the density of the entire base paper increases, and the density becomes 0.4 to 0.7 g / cm 2.
^This is because it is difficult to set the range to ³ .

The production of the multilayer paper of the present invention is carried out using a multilayer paper former in the same manner as the production of general paperboard. For example, a pulp slurry corresponding to several tens of g / m ² of dried rice tsubo is sequentially laminated on a plurality of wire parts of about 10 stations to form a wet sheet. More specifically, first, a pulp layer of about 40 g / m ² is formed on a wire part forming a paper layer serving as an outer layer, dewatered, and then transferred to a blanket. Next, a paper layer is similarly formed on the middle layer with another wire part, and the step of laminating the required number of layers on the outer layer is repeated to form a middle layer. Finally, a paper layer to be the other outer layer is formed to obtain the molded base paper of the present invention.

In the present invention, the pulp used as the low-density layer preferably has a freeness in the range of 200 to 650 ml in a re-disintegrated state according to JIS-P8121 Canadian standard form. Freeness is 200
If it is less than ml, the drained sheet is likely to have a dense structure, and it is difficult to obtain a low-density paper layer structure because drainage of pulp fibers is poor. On the other hand, if the freeness exceeds 650 ml, the sheet becomes too low in density and delamination occurs in the press step during papermaking, so that balloon-like swelling is likely to occur. The stock having a freeness of 200 to 650 ml in the re-disintegrated state has a Canadian standard freeness of 250 to 700 m irrespective of the pulp raw material used.
l. Further, measuring the freeness of the used pulp by re-disintegrating the base paper is effective for grasping the necessary pulp characteristics from a product showing good operability in a single time.

The pulp raw material used for the low-density layer is mainly composed of a pulp raw material from which a low-density paper layer can be easily obtained. Specifically, such pulp includes mechanical pulp. Mechanical pulp is usually pulp produced by crushing wood, especially N material, with mechanical force and then disintegrating it.
There are P, RGP and the like, but TMP and RGP are more preferable. Among them, those made from radiata pine, southern pine, Douglas fir, etc. have characteristics that the fibers are rigid and hard to deform, so that a low-density paper layer can be obtained, and the density during press molding also decreases. Particularly preferred because it is small. However, it is also possible to use various non-wood raw materials such as kenaf, reed, bamboo and bagasse which are sugar pomace of sugarcane. It should be noted that pulp obtained by adding chemicals during mechanical crushing and pulp partially chemically treated, such as pulp subjected to a bleaching step, are also treated as mechanical pulp.
Further, those obtained by imparting low-density characteristics to pulp by chemical treatment, such as mercerized pulp and curled fiber, can also be suitably used. In the present invention, the above-mentioned pulp is mainly used to constitute the low-density layer, but other commonly used chemical pulp using wood as a raw material or various non-woven materials such as kenaf, reed, bamboo, bagasse, etc. It is also possible to appropriately mix and use chemical pulp or the like made from wood. In any case, in the present invention, various kinds of pulp are selected so that the density of the low-density layer is 0.2 to 0.6 g / cm ^3, and if necessary, a plurality of types are blended and used. I do. In the present invention, it is further desirable that at least one of mechanical pulp, mercerized pulp and curled fiber is contained in 50% or more of the total pulp of the base paper for forming.

<Description of the Fifth Invention> In order to prevent cracks generated on the surface of the container during deep drawing, the breaking elongation (J
IS-P8113) is 5% or more, more preferably 7%
It is effective to stack the paper sheets described above. Alternatively, a paper sheet having a breaking elongation of 5% or more may be laminated on paper that does not satisfy the conditions of the first and third inventions so that the conditions of the first and third inventions are satisfied. it can.

A molded container having a large drawing depth is stretched more during molding than a container having a small drawing depth. In particular, the paper layer on the outer side of the molded container has more paper layers than the inner side (content side). Because it is stretched, a high elongation at break is required, so at least the outermost layer on the outer side of the container of the forming base paper,
By laminating the above-mentioned paper sheets having a breaking elongation of 5% or more, it is possible to prevent cracks or the like generated by stretching during drawing.

As the pulp used as a raw material for the outermost layer paper sheet, various pulp described above can be used. Among the wood fiber pulp, pine, larch, cedar, fir, hinoki and the like have a long fiber length obtained from conifers. Pulp is suitably used for improving the stretchability and strength of a paper sheet. Among the non-wood fibers, mulberry, mitsumata, kenaf, manila hemp, sisal, cotton, cotton linter, and the like are particularly preferably used because they have a long fiber length and can improve the stretchability and strength of the paper sheet.

As the papermaking chemicals, sizing agents, paper strength agents, retention agents, mineral fillers, mineral fillers, and the like, which are used in the above-mentioned forming base paper of the present invention and used in ordinary papermaking, are used.
Organic rigid fillers, dyes, pH adjusters, slime control agents, defoamers, tackifiers, etc. can be used as appropriate.

The outermost layer paper sheet having a high elongation at break can be made by the following paper making process using a slurry of the raw materials and chemicals composed of the above materials. That is, in a wet paper machine, a device for pressing and rotating an endless thick rubber belt is attached to a part of a dryer roll through a nip roll, and a wet paper is passed between the dryer and the belt, and a belt that has been stretched in advance is used. And a creping method in which paper is peeled off from a press roll of a paper machine or a processing machine or a cylinder dryer or a Yankee dryer with a doctor to give a crimp-like wrinkle. Regarding the creping method, there are various devices and methods at the doctor device and the position where creping is performed, for example, creping is performed by a doctor at a press part of a paper machine called a duostress method, and further through a grooved roll in the middle part of the dryer. There is a method of giving elongation in the vertical and horizontal directions of the paper. In the present invention, the outermost layer paper sheet obtained from the above-mentioned paper making step may be not only a single layer but also a laminated paper having two or more layers. The range of the basis weight of the outermost layer paper sheet is 40 to 300 g /
range of m ^2, more preferably 50~150g
/ M ² . The outer layer paper sheet has a basis weight of 40 g
/ M ^2, the tensile strength of the sheet is insufficient and the sheet is easily broken at the time of molding. If it exceeds 300 g / m ² , the density of the formed base paper on which the outermost layer paper sheet is laminated increases,
It is not preferable because the moldability of the folded portion of the molded body is deteriorated.

The outermost layer paper sheet obtained by the above method can be laminated with a paper support via an adhesive to produce a molded base paper. Examples of the bonding method include a wet lamination method in which a water-based adhesive such as a synthetic resin emulsion, starch, and PVA is applied to paper and then pressed and dried with a nip roll, or a hot-melt adhesive that is hot-melted is applied to the paper and the nip roll is used. The method is not particularly limited, and may be a hot melt lamination method in which pressure is applied, or an extrusion lamination method in which a thermoplastic resin such as polyethylene or polypropylene melted into heat is formed into a film and spread on paper, and then pressure-bonded with a nip roll.

<Explanation of the Sixth Invention> In order to prevent cracks generated on the surface of the container during deep drawing, a multilayer sheet having a low density layer and a high density layer according to the third and fourth inventions of the present invention is provided. In the paper, at least one outer layer is a high-density layer,
It is effective to obtain a base paper by forming a paper so that the elongation at break of the outer layer is 5%, more preferably 7% or more. By subjecting the outer layer to the outside of the molding container and performing the drawing process, it is possible to prevent the occurrence of cracks during the drawing process. As the pulp raw material and papermaking chemical that can be used for the outer layer, those usable for the outer layer paper sheet having an elongation at break of 5% or more described in the fifth invention can be similarly used.

<Other Descriptions> The forming base paper of the present invention may be provided with a coating layer comprising a pigment and an adhesive on one or both sides thereof, if necessary. By providing such a coating layer, good printability can be imparted to the surface of the forming base paper. Furthermore, it is also possible to provide a printing layer using an arbitrary ink such as a dye ink or a pigment ink using a commonly used printing machine. Known pigments such as calcium carbonate, kaolin, clay, talc, titanium oxide, and plastic pigment can be arbitrarily used as the pigment used in the coating layer. Known adhesives such as starch, casein, SBR latex, and polyvinyl alcohol can be arbitrarily used as the adhesive used for the coating layer. These coating layers can be formed as a single layer or a multilayer. The coating amount is desirably about ²⁰ to 30 g / m ^{2 as a} whole. When such a coating layer is provided, it is more preferable that the layer immediately below the coating layer has a higher beating degree and has a smoother surface. Such a coating layer can be applied using various known coating apparatuses as appropriate. Further, it is possible to further provide a printing layer on such a coating layer.

The forming base paper of the present invention may be provided with a water-resistant coating on one or both sides thereof, if necessary, in order to prevent infiltration or leakage of liquid. This water-resistant coating can be provided directly on the base paper, or on any of the above-mentioned pigment coated layers or printed layers. As a method of providing the water-resistant coating, there are coating of a water-resistant paint, lamination of a synthetic resin, and the like, which can be arbitrarily selected according to the situation. Examples of coatings that impart water resistance by coating the base paper surface include wax emulsions such as microcrystalline wax and paraffin wax, latexes such as SBR latex and polyvinylidene chloride latex, acrylic emulsions, self-emulsifying polyolefins, Various synthetic resin emulsions such as a polyethylene copolymer resin emulsion exist. The coating equipment for these water-resistant paints may be any of a commonly used bar coater, air knife coater, roll coater, blade coater, gate roll, size press, etc.
There is no particular limitation. Further, the coating amount of these is preferably about 1.0 to 20.0 g / m ^{2 as a} whole, and these coating layers can be formed in a single layer or a multilayer. Examples of the synthetic resin layer laminated on the base paper surface include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; saturated polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamide resins such as nylon; and ethylene vinyl. Examples thereof include an alcohol copolymer, a polystyrene resin, and a polyacrylonitrile resin. These water-resistant coatings are formed by coating these synthetic resins alone, or by mixing or laminating two or more kinds thereof. The method for laminating the synthetic resin layer may be any of commonly used wet lamination, hot melt lamination, extrusion lamination, dry lamination, thermal lamination and the like, and is not particularly limited.

When drawing is performed at a higher press pressure, color unevenness occurs at the crease-forming ruled line portion of the forming base paper which is the surface of the container, which significantly impairs aesthetics and impairs the commercial value. is there. To solve that problem,
It is effective to mix a pigment in the synthetic resin layer.

The amount of the pigment in the synthetic resin is preferably in the range of 3 to 40% by weight. If the content is less than 3% by weight, there is a possibility that the effect of hiding the color unevenness on the container surface may not be sufficiently obtained.
On the other hand, when the content is 40% by weight or more, the physical properties of the synthetic resin,
Chemical stability is reduced, and it is difficult to form a stable synthetic resin layer on the base paper. For example, a neck-in of the molten film occurs at the T-die, and a lack occurs due to lack of extensibility of the synthetic resin layer. When the synthetic resin is a polyolefin resin and the pigment is titanium oxide, the compounding amount of titanium oxide is 5 to 10% by weight,
60 g / m ² is preferred.

The above-mentioned water-resistant paint or synthetic resin may be a biodegradable thermoplastic resin. The type of the biodegradable thermoplastic resin is not particularly limited as long as the resin has a biodegradability equal to or higher than that of paper. That is, 3-hydroxybutyrate / 3-hydroxyvalerate copolymer, 3-hydroxybutyrate polymer, aliphatic polyester such as polycaprolactone, polyglycolide such as polylactic acid, polyvinyl alcohol, a complex of polyvinyl alcohol and starch, Synthetic or natural resins such as cellulose derivatives such as cellulose acetate can be used alone or in combination. Among these biodegradable thermoplastic resins, resins particularly suitable for the present invention are aliphatic polyesters. The biodegradable aliphatic polyester has excellent workability when laminated on base paper, and also has excellent water resistance of the product. For the purpose of improving the processability and physical properties of these thermoplastic resins, a resin or an additive having no biodegradability may be added to the resin. When adding non-biodegradable resin or additives, it is desirable to add the resin in an amount that does not exceed the weight of the original resin, and if it exceeds this, the biodegradability of the entire tray will be adversely affected. There is a possibility that it will.

Next, press forming of the forming base paper will be described. <Regarding the Forming Method> (1) Adjustment of Moisture of Base Paper As a method for producing the paper-made molded container of the present invention, a formed base paper is punched into a container blank sheet, a ruled line is formed at a required portion, and a press die composed of a male mold and a female mold is formed. A so-called draw forming method is adopted in which the blank sheet is sandwiched, heated and pressed to form. At this time, it is preferable that the formed base paper is previously conditioned and the base paper moisture is adjusted. The base paper moisture is preferably in the range of 10 to 20%, preferably 11 to 1%.
7%, more preferably 12-15%, most preferably 1
2.5-14.5%. The term “base paper moisture” as used herein refers to the percentage by weight of moisture based on the absolute dry weight of all pulp in the processed base paper. When the base paper moisture is in this preferred range, plasticization of the formed base paper occurs, and the moldability is improved, and
Destruction of the paper layer during molding can be reduced. As a result,
A drawn container having a greater depth, a smoother and more beautiful appearance, and a high rigidity can be obtained. If the water content of the base paper is less than 10%, the molded product cannot have sufficient rigidity,
On the other hand, if it exceeds 20%, blisters may be generated in the base paper for forming and processing, and the paper layer of the base paper may be peeled off. Absent. In addition, as a method of adjusting the base paper moisture, a method of supplying water to the base paper immediately before press molding,
At the time of papermaking, a method of humidifying after leaving the dryer and transporting / preserving the paper while the moisture is maintained may be mentioned.

(2) Forming Method Next, a process of manufacturing a formed container from a blank sheet will be described. In the present invention, drawing is performed by a pair of press dies. The pair of heating press dies are a convex shape having a convex shape corresponding to the inner volume of the molded product and a concave shape having a concave shape corresponding to the outer shape of the molded product. The pair of press dies can press a molded product by moving at least one of the dies in the front-back or up-down direction. For convenience of description, the convex mold is referred to as an upper mold, and the concave mold is referred to as a lower mold,
The method of pressing by moving the upper die downward (FIG. 1) will be described.

As a method of heating the blank sheet,
A method such as high-frequency heating, hot air heating, or infrared heating may be used. Further, the entire mold may be heated. In this case, means for heating the mold is required. As the mold heating means, it is common to provide an electric heating device to the press mold and heat it, but there is also a means for connecting a high frequency oscillator to the press mold and applying high frequency to dry. . Also,
Electric heating and high-frequency heating can be used in combination.

The heating temperature during molding is 10
The range which becomes 0 to 150 degreeC is preferable, More preferably, it is 110 to 140 degreeC. If the temperature is lower than 100 ° C., it takes a long time for molding, and the productivity is lowered. 150 ° C
Exceeding the range is not preferable, especially when the moisture content of the base paper is high, since blisters are easily generated. The forming base paper can be set to the predetermined temperature when it is set on the heated press machine described above. Further, as another means, a method in which an electromagnetic wave such as a microwave is applied to a processed base paper containing water to raise the temperature, and then introduced into a press machine is also possible.

The container after the completion of drawing may be taken out of the mold and air-cooled. However, in order to enhance the dimensional stability, a high-temperature container may be fixedly cooled in a cooling mold for a certain period of time. preferable.

As the material for the heating press mold, known materials such as aluminum, aluminum-based alloy, brass, iron, stainless steel, and ceramic can be used.

As a method of operating the mold, any of a hydraulic press, an air cylinder, and a cam mechanism can be used. As a specific method of controlling the clearance between the upper mold and the lower mold in the present invention, when using hydraulic pressure or air pressure, the pressure may be controlled by computer control according to the thickness of the molded product, or the position of the stopper may be controlled. May be controlled. In the case of using a cam mechanism, it is possible to perform control based on a cam shape designed in advance and a descending speed of a mold.

The press pressure at the time of press molding is as follows.
The range is preferably 0 to 100 kgf / cm ² . If the pressing pressure is lower than 10 kgf / cm ^2, the compression deformation of the ruled line portion becomes insufficient, and if it exceeds 100 kgf / cm ² , the paper layer at the folded wrinkle portion is broken, which is not preferable.

The press time for press molding is preferably in the range of 2 to 30 seconds from the viewpoint of moldability and workability.

<Characteristics of base paper under high temperature and high humidity> Under high temperature and high humidity conditions such as drawing, the breaking strength (tensile strength) of the formed base paper becomes weak, and the base paper breaks with a small force. Become. Furthermore, under high humidity conditions, the higher the temperature is, the smaller the elongation at break is, that is, there is a tendency that it is easy to break. For this reason, the tensile properties of the base paper under high temperature and high humidity are important requirements for draw forming aptitude, but it is difficult to measure the temperature and moisture of the paper during actual forming. Also, it is not easy to measure the tensile properties of paper under high temperature and high humidity.

However, as a result of the study, the present inventors found that the temperature 2
Under the conditions of 3 ° C. and a moisture content in paper of 14% by weight, it has been found that a forming base paper satisfying the following conditions is suitable for draw forming under high temperature and high humidity. The elongation at break (JIS-P8113) in the machine direction is 2%, more preferably 3% or more. The tensile modulus in the machine direction is in the range of 1000 to 2000 MPa, more preferably 1200 to 1800 MPa. In addition, the above-mentioned water content in paper means the weight of water in paper at the time of elongation and elastic modulus measurement, the total weight of paper (pulp + additive +
Water). When a synthetic resin layer is formed on a paper layer, the above measurement is a measurement in a state where no synthetic resin layer is present.

The above temperature of 23 ° C. and the water content in paper of 14% by weight
If the elongation at break in the longitudinal direction is less than 2.0%, there is a possibility that a problem of breakage may occur due to low stretchability during press molding.

Further, at a temperature of 23 ° C. and a water content of paper of 14% by weight.
When the tensile modulus in the range of 2500 MPa or less,
The fluidity of the pulp fibers of the forming base paper is enhanced, and the breakage of the paper layer at the folded wrinkles at the time of forming can be reduced. As a result, a formed article having high strength can be obtained. If the tensile modulus is less than 1000 MPa, there is a possibility that the rigidity of the molded container is insufficient. The first mentioned above
By using the constitutions of the invention and the third invention, a molded base paper having the above properties can be easily obtained.

<Container Shape> The container targeted by the present invention is a container obtained by drawing one sheet of paper with a pair of convex and concave press dies, and the upper part of the container is open. Typically, the upper edge has a flange. Further, the flange may be formed by curling.

As described above, the draw-formed container using the formed base paper of the present invention can provide a product having a smooth surface and a beautiful appearance as compared with those using conventional base paper and the like. However, the smoothness of the flange portion is particularly excellent. That is, in products using conventional base paper,
In the present invention, the step of unevenness of the flange portion, which was 0.20 mm to 0.50 mm, is changed to 0.03 mm to 0.10 mm in the present invention.
mm. Therefore, when using a sheet-like base material such as paper or film to cover the opening of the tray-shaped paper-made molding container having a flange,
Since the smoothness of the flange portion is high, the sealing property is extremely good, and a container with high sealing property can be obtained.

The outer shape of the plan view of the container is a square, a rectangle, a circle, an ellipse, or the like. For each shape, the corners are usually rounded. 2 and 3 show an example of the draw-formed container of the present invention as a sketch.

<Regarding Container Height> The present invention relates to a formed base paper capable of producing a relatively deep paper drawn container and a manufactured paper molded container. ) Is to be considered in relation to the container bottom area. When the bottom area and the height of the draw-formed paper container of the present invention are S1 and H, respectively, the following equation (1) is obtained. It is possible to produce a deep drawn container that fills it. Equation (1): 0.2 ≦ H / (S1) ^1/2

When the container does not have a substantially flat bottom (for example, the shape shown in FIG. 4), a deep drawing container satisfying the following expression (2) in relation to the height H and the upper opening area S2. Can be produced. Formula (2): 0.15 ≦ H / (S2) ^1/2 By using the forming base papers of the first to sixth inventions of the present invention, deep drawing satisfying the above formula (1) or formula (2) Containers are easily obtained.

In order to form the formed base paper of the present invention into a shape as a paper-made forming container, the base paper is divided into a bottom surface and side surfaces by ruled lines without drawing, and the side portions are folded up. Further, there is also a method of molding by folding the corners of the side portions, or overlapping and gluing (see FIG. 8).
Since the molded base paper of the present invention is bulky, paper breakage does not occur even if the ruled line is deeply inserted, and the deepened ruled line makes it difficult for gaps to be formed in the bent and joined portions, and as a result, the content Leakage can be prevented. Further, the molded base paper of the present invention can be used as a material for various general paper containers, a material for disposable paper pots, and the like.

The base paper for forming according to the present invention contains natural pulp as a main component and has better moldability than conventional forming base paper.

[0072]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited to the following embodiments. Unless otherwise specified, parts by weight are shown by solid content weight.

<Example 1-1> Using a disc refiner, commercially available NBKP was mixed with 550 mlcsf (TappiT).
-227 Canadian standard type), radiata pine TMP to 300 mlcsf, and commercial NUKP to 550 mlcsf.
Was beaten. These were used as stock, and the first layer NBKP 40 g / m ² and the second layer TMP250 were used using a multi-layer paper machine.
g / m ^2, a cardboard composed of three layers of the third layer NUKP40g / m ² to papermaking, and the molding base paper. The base paper was measured for tensile strength, elongation at break, critical compressive stress, and amount of compressive deformation in the thickness direction by the measuring methods described below. Further, it was formed into a tray shape and the formability was evaluated.

<Example 1-2> 80 parts of commercially available LBKP beaten to 500 mlcsf with a disc refiner, 20 parts of commercially available NBKP also beaten to 500 mlcsf, and expandable microcapsule particles (trade name: Matsumoto Microsphere F-30D, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) ) A stock of 10 parts was prepared. From this stock, paper having a basis weight of 150 g / m ^{2 was made with} a laboratory hand-making machine, and then dried with a rotary dryer.
Dried at 10 ° C. This handmade paper was evaluated as a forming base paper in the same manner as in Example 1-1.

<Example 1-3> From a stock obtained by beating commercial NBKP to 600 mlcsf with a disc refiner,
Paper having a basis weight of 260 g / m ^{2 was made with} a laboratory hand-making machine and dried at 110 ° C. with a rotary dryer. This handmade paper was evaluated as a forming base paper in the same manner as in Example 1-1.

<Example 1-4> Radiator pine TMP
Was crushed to 300 ml csf with a disc refiner, and a paper having a basis weight of 280 g / m ² was formed with a laboratory hand-making machine, and dried at 110 ° C. with a rotary dryer.
This handmade paper was evaluated as a forming base paper in the same manner as in Example 1-1.

<Comparative Example 1-1> 50 parts by weight of curled fiber (manufactured by Warehauser) and radiata pine TMP
A paper having a basis weight of 290 g / m ² was formed from a mixed stock of 50 parts by weight without defibering and mixing. This paper was evaluated as a forming base paper in the same manner as in Example 1-1.

<Comparative Example 1-2> Evaluation was made in the same manner as in Example 1-1, wherein the forming base paper was filter paper for production (trade name: filter paper No. 2 for standard, Advantech Toyo, basis weight 125 g / m ² ). did.

<Comparative Example 1-3> A base liner was processed with a K liner (trade name: NRK280, manufactured by Oji Paper, basis weight 280 g).
/ M ² ) and evaluated in the same manner as in Example 1-1.

<Comparative Example 1-4> Evaluation was made in the same manner as in Example 1-1, except that the forming base paper was cup base paper (manufactured by Shinfuji Paper, weighing 290 g / m ² ).

[Evaluation Method] (1) Tensile Strength A width of 15 mm and a length of 250 m in the flow direction and the width direction, respectively.
m at 24 ° C. under the conditions of 23 ° C. and 50% RH.
After adjusting the humidity for more than an hour, it was measured at a tensile speed of 20 mm / min using a Strograph M2 tester (manufactured by Toyo Seiki Seisakusho) in accordance with JIS-P8113.

(2) Elongation at break 15 mm in width and 250 m in length in the flow direction and the width direction, respectively.
m at 24 ° C. under the conditions of 23 ° C. and 50% RH.
After adjusting the humidity for more than an hour, it was measured at a tensile speed of 20 mm / min using a Strograph M2 tester (manufactured by Toyo Seiki Seisakusho) in accordance with JIS-P8113.

(3) Critical compressive stress 12.7 mm in width and 15 in length in each of the flow direction and the width direction
The test piece cut to 2.4 mm was conditioned at 23 ° C. and 50% RH for 24 hours or more, and then compressed using a digital ring crush tester X-1104 (manufactured by Orientec) in accordance with JIS-P-8126. Measure strength A,
Furthermore, the load portion area B of the test piece when measuring the compressive strength
Was calculated from the following equation. Critical compressive stress = A / B where Critical compressive stress unit: MPa Compressive strength unit: N Area of load portion of test piece = Thickness of test piece (mm) × 15
2.4 mm (The thickness of the test piece is a value measured according to JIS-P8118 for a sample conditioned for at least 24 hours at 23 ° C. and 50% RH)

(4) Amount of Compressive Deformation A test piece having a size of 50 mm × 50 mm was conditioned at 23 ° C. and 50% RH for 24 hours or more, and then compressed using a strograph M2 tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.). Speed 1.0mm
One specimen was compressed in the thickness direction at / min to draw a stress-strain curve, and the amount of compression (strain) at a compressive stress of 20 kgf / cm ² was measured.

(5) Formability A blank sheet for forming was obtained in which 24 ruled lines were provided on the forming base paper as shown in FIG. This blank sheet was pressed at a pressing pressure of 35k using a molding die and a press molding machine.
gf / cm ² , a press temperature of 150 ° C., and a press time of 5 seconds, a tray shape as shown in FIG.
cm, height about 4 cm). The moldability at this time was evaluated in three steps as follows. ：: Can be molded into a tray shape, and the surface of the molded body is smooth. Δ: Although it can be formed into a tray shape, there are large irregularities on the surface of the formed body, particularly on the folded wrinkle portion. ×: The blank was broken at the time of molding and could not be molded into a tray shape.

The evaluation results are shown in Tables 1 and 2.

[0087]

[Table 1]

[0088]

[Table 2]

From Tables 1 and 2, it can be seen that the molded base paper according to the present invention has no cracks and no irregularities in the folded wrinkles during molding and is excellent in moldability.

<Example 2-1> The following three types of pulp were successively laminated by a laboratory oriented paper machine manufactured by Kumagai Riki Kogyo at a wire speed of 300 m / min in this order. went. Commercial NBKP, 450mlcsf, 50g / ^{m 2} Radiata pine TMP, 350mlcsf, 180
g / m ² Commercially available NBKP, 450 mlcsf, 50 g / m ² (Each stock was beaten to a predetermined freeness by a KRK high-concentration disc refiner type beater manufactured by Kumagaya Riki Kogyo Co., Ltd.) Starch (trade name: ONL510, manufactured by Oji Cornstarch) was sprayed on the front side (felt side) of each layer so that the starch concentration was 2.0%, and the solid content was 1.0 g / m ² . Later, they were combined. Then, the wet paper-like laminated sheet obtained above was calendered (produced by Yuri Roll Machine) using a nip pressure of 1
At a pressure of 0 kg / cm and a speed of 30 m / min, it is sandwiched between monoplastic canvas sheets (made by Shikishima Canvas) and subjected to pressure treatment. Next, the sheet is dried by a ferro-type cylindrical heating dryer type dryer. Next, the sheet is heated at 20 ° C.
Humidity control at 65% RH, calender (made by Yuri Roll Machine), nip pressure 20kg / cm, speed 20m / min
After the calendering process, a 2.0 g / m ² coating of PVA having a concentration of 8.0% (Kuraray Povar PVA-KL118: manufactured by Kuraray) is applied manually, and a nip pressure of 40 kg is applied by a calender (made by Yuri Roll Machine). / Cm, speed 20m / m
The material subjected to heat calendering at 120 ° C. was used as a forming base paper. The base paper for forming is processed at 20 ° C./65% RH.
After humidity control, the grammage, thickness, density and Z-strength Taber stiffness are measured. Further, polypropylene was laminated on the front side of the forming base paper by melt extrusion to a thickness of 40 μm to form a sheet for a paper-made container. Engrave (see FIG. 5). The sheet for a paper-made container was heated and pressed at 130 ° C. and 35 kg / cm ² in an oval-shaped paper-made container having male and female concavities and convexities using a test press molding machine (manufactured by Daiichi Koki). A molded paper container having a size of about 20 cm, a minor axis of about 14 cm, and a height of about 4 cm was obtained (see FIG. 6). 70% starch (trade name: Oji Ace A, manufactured by Oji Cornstarch) having a concentration of 7% was supposed to be a food in the paper-made container.
After cooling the gelatinized liquid gelatinized at 0 ° C. to room temperature, 250 g is charged. The appearance of the paper-made container after the gelatinization liquid has been loaded,
After confirming that there is no swelling at the bottom and that it is in a normal form, cover the opening with a polyethylene film, put it in a refrigerator, and leave it at 5 ° C for 12 hours. And the degree of bottom swelling was evaluated and determined by the method described below.

<Example 2-2> Three types of pulp shown below
Use the following coating liquid when applying to the surface.
The weight after drying by hand coating with a Meyer bar
Undercoat 9.0g / m ², Top coat 10.0 g / m²become
Coated in a hot air dryer at 105 ° C (Advantech
The same as in Example 2-1 except for drying for 60 seconds
Papermaking was performed by the method. Commercially available NBKP, 450mlcsf, 50g / m² Radiata pine TMP300mlcsf / commercially available NB
KP, 150mlcsf product = blended at 70/30, after blending
Freeness 280mlcsf, 230g / m² Commercially available NBKP 450mlcsf, 50g / m² [Painting composition] Top coat: Kaolin (Product name: Ultra White 90, D
Ngelhard Co., Ltd.) / Calcium carbonate (brand name: BRILLI)
Ant, manufactured by Shiraishi Kogyo) / Titanium oxide (trade name: TCA3)
33, manufactured by Tochem Products) = 50/35/15,
And latex (trade name: L1410, manufactured by Asahi Kasei) / Urine
Phosphorylated esterified starch (trade name: MS4600, Japan
= 15/5). (Blending part based on solid content weight
Number, same below. Undercoat: Kaolin (Product name: Kaobright, Seal Inc.)
Made) / Calcium carbonate (Product name: Softon 2200, Bei
Kitaoka Chemical) = 50/50, and latex (trade name: 0)
668, manufactured by JSR) / Urea phosphate esterified starch (product)
Name: MS4600, manufactured by Nippon Shokuhin Kako) = 15/5. Then, for a paper-made container in exactly the same manner as in Example 2-1.
Obtain a sheet and a paper-made container and measure and evaluate in the same way
Was done.

<Example 2-3> [0092] Except for using the following three types of pulp, a papermaking process was performed in the same manner as in Example 2-1. Commercially available NBKP, 450 mlcsf, 50 g / m ² radiata pine TMP, 350 mlcsf / commercial L
BKP, blended at 350 mlcsf product = 70/30, freeness after blending 350 mlcsf, 200 g / m ² Commercially available NBKP 380 mlcsf, 50 g / m ² Then, a molded base paper was obtained in exactly the same manner as in Example 2-1 to obtain 20 ° C / 65% After humidity control with RH, basis weight, thickness, density,
The Z strength Taber stiffness was measured. Then, Example 2-1
In the same manner as described above, the front side is subjected to polypropylene lamination to obtain a sheet for a paper-made molded container, and the sheet is punched into the shape shown in FIG. 7 to form a ruled line. About 20 long sides as shown in
cm, a short side of about 14 cm, and a height of about 4 cm were obtained, and measured and evaluated in the same manner.

<Example 2-4> A laminated paper was prepared in the same manner as in Example 2-1 except that the following three types of pulp were used. Commercial NBKP, 450 mlcsf, 50 g / m ² Commercial mercerized pulp 300 mlcsf / NBK
P, blended at 150 mlcsf product = 70/30, freeness after blending 250 mlcsf, 200 g / m ² Commercially available NBKP 450 mlcsf, 50 g / m ² Then, in exactly the same manner as in Example 2-1, sheet for paper-made container and paper-made molding A container was obtained, and measurement and evaluation were performed in the same manner.

<Example 2-5> Except for using the following three types of pulp, a papermaking process was performed in the same manner as in Example 2-1. Commercially available NBKP, 450 mlcsf, 50 g / m ² Commercially available NBKP, 150 mlcsf product / Curled fiber (manufactured by Warehauser) 750 mlcsf product = 70 /
30 blended, freeness after blending 300mlcsf, 16
0 g / m ² Commercially available NBKP 450 mlcsf, 40 g / m ² Then, a sheet for a paper-made molded container and a paper-made molded container were obtained in exactly the same manner as in Example 2-1 and were measured and evaluated in the same manner.

<Example 2-6> Except for using the following three types of pulp, a paper was made in the same manner as in Example 2-1. Commercial NBKP, 450mlcsf, 50g / ^{m 2} kenaf TMP, 350mlcsf, 185g / ^{m 2} commercial NBKP, 380mlcsf, 50g / ^{m 2} and then, in the same manner as in Example 2-1 sheet paper molded containers, and paper molding A container was obtained, and measurement and evaluation were performed in the same manner.

<Reference Example 2-1> Papermaking was performed in the same manner as in Example 2-1 except that the following pulp was used, and only one layer was used. Commercially available NBKP, 450 mlcsf, 350 g / m ² Then, the processed base paper was formed in exactly the same manner as in Example 2-1.
Then, a molded container made of paper was obtained, and measurement and evaluation were similarly performed.

<Reference Example 2-2> Papermaking was performed in the same manner as in Example 2-1 except that the following two types of pulp were used, and only two layers were used. Commercial NBKP, 450mlcsf, 50g / ^{m 2} Radiata pine TMP, 350mlcsf, 250
g / m ² Next, a sheet for a paper-made molded container and a paper-made molded container were obtained in exactly the same manner as in Example 2-1 and were similarly measured and evaluated.

<Reference Example 2-3> Papermaking was performed in the same manner as in Example 2-1 except that the following three types of pulp were used. Commercially available NBKP, 450 mlcsf, 28 g / m ² radiata pine TMP, 350 mlcsf, 28 g
/ M ² Commercially available NBKP, 450 mlcsf, 28 g / m ² Then, a sheet for a paper-made container and a box-shaped container were obtained in exactly the same manner as in Example 2-3, and measurement and evaluation were performed in the same manner.

<Reference Example 2-4> Papermaking was performed in the same manner as in Example 2-1 except that the following pulp was used, and only one layer was used. Commercially available NBKP, 450 mlcsf, 360 g / m ² Then, a sheet for a paper-made molded container and a paper-made molded container were obtained in exactly the same manner as in Example 2-1 and were measured and evaluated in the same manner.

Tables 3 and 4 show the measurement and evaluation results of the above Examples and Reference Examples. The evaluation method is as follows.

[Density of Each Paper Layer] Each layer was peeled off by the delamination method described in JIS P 8139 for the peel strength of the laminated layer of the paperboard, and the thickness (mm) and the basis weight (g / g) were measured.
m ² ). Since the thickness of each peeled layer is fluffed due to peeling and becomes thicker than the actual thickness, the correction factor value is calculated by the following method, and the thickness value of each layer after peeling is corrected. Is calculated. Correction factor value = total layer thickness before peeling / total value of each layer thickness after peeling It is difficult to peel each layer by the interlayer peeling method described in the peel strength test method of the laminated layer of the paperboard of JIS P8139. In such a case, the multi-layer assorted sheet sample is immersed in warm water at 60 ° C. for 1 hour and then separated into a surface layer, a middle layer and a back layer.
Dry each stripped layer, thickness (mm), basis weight
(g / m ² ). Thereafter, the above correction factor value is similarly calculated, the thickness of each of the separated layers is corrected, and the density of each of the layers is calculated.

[Judgment of Body Swelling Ratio] The outer peripheral value of the central portion of the paper tray body was measured, and the difference between the normal state before the evaluation test and the outer peripheral value of each body central portion after 12 hours was measured. Calculate the rate. Body bulge rate% = (Body central outer circumference value after 12 hours−Body central outer circumference value before evaluation test) / Body central outer circumference value before evaluation test 1.5% to 3.0
% And X was less than 1.5%.

[0103]

[Table 3]

[0104]

[Table 4]

<Example 3-1> Using a disc refiner, commercially available NBKP was 550 mlcsf (TapiT
-227 Canadian standard type), and radiata pine TMP was beaten to 300 mlcsf. These were used as stock, and the first layer NBKP 40 g / m ² ,
A paper support having a two-layer constitution of a second layer TMP of 250 g / m ^{2 was} prepared (see Table 5 below for the density of each layer of the support).

[0106]

[Table 5]

A bleached kraft stretched paper (75 g / m ² basis weight, manufactured by Oji Paper) was laminated as an outer layer sheet to the paper support to obtain a molded base paper. Lamination was performed in the following procedure. Immediately after applying 20 g / m ^{2 in} terms of solid content of an EVA emulsion type adhesive (trade name: Vinizol 1412, manufactured by Daido Kasei Co., Ltd.) on the surface of the TMP layer of the paperboard with a Meyer bar, The bleached kraft stretched paper was pressed with a hand roll and dried at 110 ° C. for 20 seconds with a hot air drier. The molded base paper thus obtained was evaluated for elongation at break and moldability by a test method described later.

<Example 3-2> An outer layer sheet to be bonded to a paper support was unbleached kraft stretched paper for cement bags (with a basis weight of 83).
g / m ² , manufactured by Oji Paper Co., Ltd.), and a molded base paper was produced and evaluated in the same manner as in Example 3-1.

<Example 3-3> The second layer of the paper support was replaced with TM.
A molded base paper was produced and evaluated in the same manner as in Example 3-1 except that P180 g / m ² and the outer layer sheet to be bonded to the paper support were kraft stretched paper for adhesive tape.

<Reference Example 3-1> From a stock obtained by beating commercial NBKP to 640 mlcsf with a disc refiner,
Paper with a basis weight of 70 g / m ^{2 is made with} an experimental hand-making machine,
Dry at 110 ° C. with a rotary dryer. A molded base paper was manufactured and evaluated in the same manner as in Example 3-1 except that this handmade paper was used as an outer layer sheet to be bonded to a paper support.

<Evaluation method> (1) Elongation at break 15 mm in width and 250 m in length in each of the flow direction and the width direction
m at 24 ° C. under the conditions of 23 ° C. and 50% RH.
After adjusting the humidity for more than an hour, it was measured at a tensile speed of 20 mm / min using a Strograph M2 tester (manufactured by Toyo Seiki Seisakusho) in accordance with JIS-P8113. (2) Formability By applying steam to the forming base paper and adjusting the humidity, the water content in the paper was adjusted to 12%, punched out in a circular shape, and radially engraved ruled lines from the center to form a blank sheet. The blank sheet was molded at 130 ° C. by a test press molding machine (manufactured by Daiichi Koki Co., Ltd.) using a male and female concave and convex cup container molding die
And heating and pressurizing treatment at 35 kg / cm ^2, it is in 7cm height,
The opening is circular with a diameter of 12 cm and the bottom is 6 cm in diameter
A cup-shaped drawn compact having a circular shape, a flange portion having a width of 0.8 cm, and a curved surface extending from the side wall to the bottom surface was formed (FIG. 9). At this time, molding was performed so that the outer layer sheet bonding side was outside the molded body. And the moldability at this time was evaluated as follows. ：: Moldable into a cup shape, the outer layer of the molded body was not broken, and the surface of the molded body was smooth. C: Moldable into a cup shape, but the outer layer of the molded body was broken. Table 6 shows the evaluation results.

[0112]

[Table 6]

According to Table 6, the forming base paper of the present invention in which an outer layer sheet having a breaking elongation of 5% or more was laminated as the outer layer sheet, even when the drawing depth of a cup or the like was large, the outer paper layer surface was cracked during molding. It can be seen that no cracking or tearing occurred and the moldability was excellent.

[0114]

Industrial Applicability According to the present invention, a pulp containing, as a main component, a pulp suitable for press molding which has good moldability in which cracks and unevenness of a folded wrinkle portion do not occur during press molding and high productivity. It is possible to provide a base paper for forming. Further, according to the present invention, it is possible to provide a paper drawn container (deep drawn container) applicable to applications such as relatively deep trays and cups. In particular, it is possible to provide a paper-made drawn container having excellent flange smoothness. In addition, according to the present invention, it is possible to provide a highly rigid paper container which is formed by deep drawing, is lightweight, and does not cause the swelling or bottom swelling phenomenon of the container.

[Brief description of the drawings]

FIG. 1 is a schematic view of a drawing method using a press.

FIG. 2 is a perspective view of an embodiment of the present invention.

FIG. 3 is a perspective view of an embodiment of the present invention.

FIG. 4 is a perspective view of an embodiment of the present invention.

FIG. 5 is a plan view of a blank sheet of a drawn paper molded container.

FIG. 6 is a perspective view of a formed paper container.

FIG. 7 is a plan view of a blank sheet of a box-formed container.

FIG. 8 is a perspective view of a box-shaped container.

FIG. 9 is a perspective view of an embodiment of the present invention.

[Explanation of symbols]

 1. Male type 2. Female type 3. Forming base paper 4. Ruled line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 11/20 D21H 11/20 // D21J 3/10 D21J 3/10

Claims (8)

[Claims] (1) A molded base paper characterized by satisfying the following four conditions: Tensile strength (JIS-P8113) is 2.0 kN / m
that's all. Elongation at break (JIS-P8113) is 1.5% or more. Critical compressive stress defined by the following equation is 1 to 10MP
a range. Critical compressive stress = A / B where A indicates the compressive strength according to JIS-P8126, and B indicates the load area of the test piece at the time of measuring the compressive strength. The amount of compressive deformation when a compressive stress of 20 kgf / cm ² is applied in the thickness direction is 10% or more. 2. The molded base paper according to claim 1, wherein the raw pulp of the formed base paper includes mechanical pulp. ^3. A high density layer having a density of 0.7 to 0.9 g / cm ^{3 and} a low density layer having a density of less than 0.7 g / cm ³ ,
Rice tsubo is 100-500 g / m ² , and the overall density is 0.4-
A molded base paper characterized in that the base paper is 0.7 g / cm ³ and the low-density layer is mainly composed of pulp selected from at least one of mechanical pulp, curled fiber, and mercerized pulp. 4. The base paper according to claim 3, wherein the low-density layer mainly comprises mechanical pulp. 5. Elongation at break (JIS-P8)
The molded base paper according to any one of claims 1 to 4, wherein paper sheets in which 113) is 5% or more are laminated. 6. At least one outer layer is a high-density layer,
The molded base paper according to any one of claims 3 to 4, wherein the elongation at break (JIS-P8113) of the outer layer is 5% or more. 7. A molded container made of paper, wherein the molded base paper according to claim 1 is used. 8. The paper container according to claim 7, wherein the container is formed by drawing.