JP2007314246A - Base paper for molded container, and paper-made molded container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper-made molded container which has an oil-proof property, mold-release characteristics, a heat-resistant property, moderate gas-permeability and a high degree of freedom in molding, and can be used repetitively as a re-usable baking mould, and base paper for molded containers that can obtain the paper-made molded container. <P>SOLUTION: The base paper for the molded container is formed in such a manner that a piece of substrate paper that satisfies following four conditions of (1) to (4) has a layer of releasing agent on at least one of its surfaces with air permeability (JIS-P8117) of 100 to 5000: (1) tensile strength (JIS-P8113) is 2.0 kN/m or larger; (2) elongation at break (JIS-P8113) is 1.5% or higher; (3) critical compressive stress defined by the following formula is in a range of 1 to 10 MPa (critical compressive stress=A/B, wherein A denotes compressive stress according to JIS-P8216, while B denotes the loaded area of a test piece at the time of measuring compressive stress); (4) a compressive deformation amount at the time of adding a compressive stress of 20 kgf/cm<SP>2</SP>in the direction of a thickness is 10% or higher. The foregoing base paper for the molded container is molded by means of press-forming into the paper-made molded container. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention particularly relates to a base paper for forming containers and a paper forming container for obtaining a paper forming container that can be suitably used as a baking mold for foods produced by cooking such as bread, cakes, and confectionery.

Conventionally, foods manufactured by heat cooking such as bread, cakes, confectionery and the like are usually cooked by putting food materials in baking molds made of various materials. For example, a baking mold is manufactured from a base paper for food containers, which is provided with a release layer such as a silicone resin on a paper base and has been provided with oil resistance, heat resistance, and releasability (Patent Document 1, Patent). Reference 2).
Paper-based baking molds are cheaper than metal and silicone resin baking molds, and are still widely used today. However, the strength of such a paper base material may not be sufficient in some cases.
In addition, in such an application as a baking mold, a container shape having no seam at the bottom and side portions is suitable. In the case of a cylindrical mold, a cup-shaped container by press molding (see Patent Document 2 and FIG. 5) is suitable, and in the case of a rectangular mold, a four-corner tray (see Patent Document 2 and FIG. 4) is suitable. However, in the case of a cup-type container formed by press-molding general base paper, strength and shape stability are not sufficient, and there is almost no freedom of shape, and products with complex and diverse shapes are currently available. It was impossible to manufacture. Moreover, when the base paper which apply | coated the release agent to the base material is used, adhesion | attachment with the adhesive of a release agent coating surface is difficult, As a result, there existed a problem in productivity and shape stability.
Moreover, using the baking mold which bonded films and paper base materials, such as a polyethylene terephthalate, in order to improve shape retainability and intensity | strength is also performed (patent document 3, patent document 4). However, there has been a problem that the easy disposal and recyclability of the paper is impaired by laminating the paper substrate and the film. Moreover, the problem that there is no freedom of shape has not been solved. Furthermore, by laminating the film, gas permeability such as air permeability or water vapor permeability of the base material is impaired, and as a result, the gas such as water vapor generated from the food material during cooking is prevented from being released, and the container May be deformed or the appearance of food may be affected. In addition, when cooking, high temperature gas does not reach the inside of the container, and thus there is a problem that food is not burnt or uniform heating is prevented. Although such a problem was dealt with by providing a hole at the bottom of the container, an extra step of drilling was necessary, and a problem of appearance of food could occur.
Furthermore, there is a baking tray such as a bread formed using a mixture of pulp and synthetic fiber as a base paper in order to increase the degree of freedom of shape by press molding (Patent Document 5). Since such a tray contains a lot of thermoplastic synthetic resin fibers, it has poor heat resistance when used as a baking mold and has no air permeability, so there was a problem in terms of durability when repeatedly used. .

JP-A-53-086819 JP 2002-326691 A JP 07-264964 A JP 2000-109157 A Utility Model Registration No. 3116832 JP 2002-201598 A

The present invention solves the above problems.
That is, according to the present invention, it is used as a baking mold having oil resistance, mold release property, heat resistance, moderate gas permeability, high degree of freedom in molding, and strength and shape stability that can be used repeatedly. It becomes possible to obtain a paper-molded container that can be obtained and a base paper for a molded container that can obtain the container.

In order to solve the above problems, the present invention has the following configuration.
That is, in the first aspect of the present invention, a release agent layer is provided on at least one surface of a base paper that satisfies the following four conditions (1) to (4), and the air permeability (JIS-P8117) is , 100-5000 base paper for forming containers.
(1) Tensile strength (JIS-P8113) is 2.0 kN / m or more.
(2) Elongation at break (JIS-P8113) is 1.5% or more.
(3) The critical compressive stress defined by the following formula is in the range of 1 to 10 MPa.
Critical compressive stress = A / B
However, A is the compressive strength according to JIS-P8126,
B shows the load part area of the test piece at the time of compressive strength measurement, respectively.
(4) The amount of compressive deformation when a compressive stress of 20 kgf / cm ² is applied in the thickness direction is 10% or more.

  2nd of this invention is the base paper for shaping | molding containers as described in 1st of this invention which contains mechanical pulp as raw material pulp of base paper.

The third of the present invention has a density 0.7～0.9G / dense layer of cm ^3, and has a low density layer density of less than 0.7 g / cm ^3, a basis weight is 100 to 500 g / m ^2, At least a base paper composed mainly of pulp selected from at least one of mechanical pulp, curled fiber, and mercerized pulp, and having a total density of 0.4 to 0.7 g / cm ³ and a low density layer. A release agent layer is provided on one side, and the base paper for molded containers has an air permeability (JIS-P8117) of 100 to 5000.

  4th of this invention is the base paper for shaping | molding containers in any one of 1st-3rd of this invention in which a releasing agent layer is formed from a silicone resin.

  5th of this invention is the base paper for shaping | molding containers in any one of 1st-4th of this invention which provided the undercoat layer between the base paper and the release agent layer.

  A sixth aspect of the present invention is a paper-made container formed by pressing the base paper for forming containers according to the first to fifth aspects of the present invention.

  A seventh aspect of the present invention is a paper molded container obtained by molding the base paper for a molded container according to the first to fifth aspects of the present invention into a tray carton.

  According to the present invention, a paper-molded container that can be used as a baking mold having oil resistance, releasability, heat resistance, high molding freedom, strength and shape stability that can be used repeatedly, and the It has become possible to obtain a base paper for molded containers from which containers can be obtained.

The pulp constituting the base paper of the forming container base paper in the present invention will be described below.
As natural pulp fiber, wood fiber (chemical pulp, mechanical pulp), non-wood fiber, waste paper pulp and the like are arbitrarily used as necessary. Among the wood fibers, examples of chemical pulp include kraft pulp and sulfite pulp. These pulps may be unbleached or bleached. Examples of mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), and thermomechanical pulp (TMP) obtained by heating and refining wood chips.
Of these mechanical pulps, TMP is optimal in terms of the bulkiness and strength of the sheet. In addition, as TMP, C-TMP which refines under pressure after chemically processing a wood chip | tip, BC-TMP etc. which performed the bleaching process etc. shall be included. Moreover, among these wood fiber pulps, a pulp having a long fiber length obtained from conifers is preferably used in order to improve the stretchability and strength of the base paper.

Non-wood fibers include bast fibers such as mulberry, kenaf and jute, seed hair fibers such as cotton and cotton linter, leaf fibers such as manila hemp and sisal hemp, and stem fibers such as bamboo and bagasse. A kind etc. can be used arbitrarily as needed. In particular, Kozo, Mitsumata, Kenaf, Manila hemp, sisal hemp, cotton, cotton linter and the like are preferably used because they have a long fiber length and can improve the stretchability and strength of the base paper of the present invention.
In the present invention, various types of used paper pulp can be used as necessary.

The above various pulp fibers can be used alone or in combination of two or more.
Moreover, a synthetic resin fiber can be mixed as needed in the range which does not impair the effect of this invention.

The base paper for the forming container base paper of the present invention composed of the above pulp fibers has a tensile strength (JIS-P8113) of 2.0 kN / m or more, preferably 10 kN / m or more, and elongation at break (JIS-P8113). ) Is preferably 1.5% or more.
If the tensile strength of the base paper is lower than 2.0 kN / m, or the elongation at break is lower than 1.5%, the stretchability is low, and it is unsuitable because it breaks during press molding.
In order to control the tensile strength and elongation at break in the above ranges, in the case of a single layer, NBKP is used for one part of the pulp, or the amount of the paper strength enhancer is adjusted, or the paper It can be controlled by a known method such as a method in which a layer is formed in multiple layers and NBKP is used in at least one layer or a paper strength enhancer is blended.

When a flat base paper is press-molded, if the molded body has a curved portion with a large distortion, it is necessary to form a folded wrinkle on the curved portion to absorb the distortion. At this time, the folded wrinkle portion is folded in the plane direction like an accordion to form irregularities, and then the irregularities are compressed in the thickness direction by pressing.
Therefore, in order to obtain good press formability, the critical compressive stress of the base paper is in the range of 1 to 10 MPa, preferably in the range of 5 to 10 MPa, and the compressibility in the thickness direction is in the range of 10% or more. Preferably there is.
In addition, the compression rate in this invention shows the compression rate of the thickness direction when a compressive stress with a load of 20 kgf / cm ² is applied. When the limit compressive stress exceeds 10 MPa, the folded wrinkle portion is not sufficiently folded, and when the compression rate is lower than 10%, the 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 fall within the above ranges, it is necessary to lower the base paper density. To that end, it is preferable to use rigid pulp fibers. In general, a pulp sheet is beaten (a mechanical external force is applied to the pulp fiber to fibrillate a part of the cell wall of the fiber) to obtain a paper sheet having a uniform texture. It is necessary to keep beating lightly in order to maintain rigidity.
As the degree of beating, for example, in the case of chemical pulp, the freeness (Tappi T-227 Canadian standard type) is 500 mlcsf or more, in the case of mechanical pulp, 180 mlcsf or more, in the case of hemp pulp or kenaf pulp, 500 mlcsf or more, and in the case of corrugated used paper pulp, 500 mlcsf or more. Those are preferred. In addition, various refiners used conventionally can be used suitably for beating of pulp fiber.

  In addition, a foaming agent may be added during papermaking of the base paper to lower the density within a range not impairing the effects of the present invention. Examples of the foaming agent include thermally expandable microcapsules in which a low boiling point solvent is enclosed in microcapsules. Further, a light inorganic pigment such as Shirasu balloon can be added to lower the density.

As papermaking chemicals added to the stock to make the base paper of the present invention, the same sizing agent, paper strength agent, yield improver, etc. as used in normal papermaking are used as necessary. can do. These papermaking chemicals can also be added by spraying between paper layers during the papermaking process, or by coating on the surface of the base paper during or after papermaking.
In addition, the same filler as that used in ordinary papermaking at the time of papermaking can be added in any combination as necessary.

Furthermore, additive agents for papermaking such as dyes, pH adjusters, slime control agents, antifoaming agents, and stickers can be appropriately used depending on the application.
The pH at the time of papermaking according to the present invention can be arbitrarily selected between about 4.5, which is acidic papermaking, and about 6-8, which is neutral papermaking.

Paper stock made of the above materials is made by a conventional method. The paper machine to be used is not particularly limited, and any type of paper machine conventionally used can be appropriately selected. Also in drying, any type of dryer conventionally used can be appropriately selected and is not particularly limited.
In the present invention, the base paper obtained from the paper making process may be a single layer or a two or more layered paper.

The basis weight of the base paper thus obtained is preferably in the range of 100 to 500 g / m ² and more preferably in the range of 200 to 400 g / m ² . If the basis weight is lower than 100 g / m ^{2, the} molded product obtained after press molding does not exhibit sufficient strength, and if it exceeds 500 g / m ² , the moldability of the folded wrinkle portion is unfavorably deteriorated.
According to the method described above, paper satisfying the requirements (1) to (4) of the present invention can be produced. However, in order to balance strength, elongation, rigidity, and compression rate formation, kraft pulp or high-quality waste paper is mainly used. between the two outer layers of density 0.7~0.9g / cm ³ to have a middle layer of a density less than 0.7 g / cm ³ consisting mainly of mechanical pulp, density 0.4 to 0.7 g / cm ³ It is most preferable to use a multilayer paper.

As the substrate sheet of the forming container base paper in the present invention, the density and the low density layer of less than 0.7 g / cm ^3, the density of 0.7~0.9g / cm ³ of two or more layers including a dense layer It is preferable to use a paper that is a multilayer paper and has an overall density of 0.4 to 0.7 g / cm ³ . The low density layer preferably has a density of 0.2 to 0.65 g / cm ³ .

  The above multi-layer paper only needs to have one low-density layer and one high-density layer. More preferably, both the outer layers on the front and back sides are both high-density layers, and the middle layer, which is a low-density layer, is sandwiched between them. This is more effective in obtaining a bulky and stiff base paper.

Paper, stiffness S of sheet paperboard or the like, when the sheet was considered cantilever, S = E · I / B · W = E · T 3/12 · W, (E: Young's modulus MPa, I: Cross section secondary moment N · cm ² , B: sample width mm, W: sample weight kg, T: sample thickness mm). That is, it can be considered that the stiffness S is proportional to the cube of the Young's modulus and the sheet thickness.

Furthermore, the stiffness of a multi-layered sheet such as paperboard is determined by Tappi Nov, 1963, Vol. 46, no. 11 A.E. T.A. According to Luey, the stiffness value of each layer is obtained from the Young's modulus of each layer and the second moment of section similarly using the above 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 distance from the center of the paper thickness is far, that is, the thicker the paper thickness, the higher the rigidity, so the middle layer may be bulky. Further, since the stiffness is indicated by the product of the cube of the thickness and the Young's modulus, the higher the Young's modulus is, the more effective the stiffness is.

Therefore, the density of the middle layer is less than 0.7 g / cm ^3, more preferably 0.2~0.65g / cm ^3. More preferably, it is 0.3-0.6 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 I can't.
Moreover, it is preferable that the density of an outer layer is 0.7-0.9 g / cm < ³ >. If it is less than 0.7 g / cm ³ , the Young's modulus of the outer layer decreases, and the rigidity of the present invention cannot be expected to improve. Further, when the density exceeds 0.9 g / cm ³ , the outer layer surface of the base paper becomes too tight, so that it is practically difficult to obtain a higher density layer at the paper making stage. Moldability is not accompanied.

There are no particular restrictions on the type of pulp used in the high-density layer, but it is particularly desirable to increase the beating degree of N-material (coniferous) pulp such as NUKP and NBKP so as not to lose rigidity. In addition, in order to make this invention effective, it is preferable that the basic weight of the outer layer made into the high-density layer is 15-100 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 papermaking itself is difficult. On the other hand, when the outer layer exceeds 100 g / m ² , the basis weight of the low density layer is relatively reduced, so that the density of the whole base paper is increased, and it is difficult to make the range from 0.4 to 0.7 g / cm ^3. It is.
The production of the multi-layer paper as the base paper of the present invention is performed using a multi-layer paper former as in the production of general paperboard.

In the present invention, the pulp used as the low density layer is preferably a pulp having a freeness in the range of 200 to 650 ml in the re-disaggregation state according to the Canadian standard form of JIS-P8121. If the freeness is less than 200 ml, the pulp fibers are poorly drained, so that the squeezed sheet tends to have a dense structure, making it difficult to obtain a low-density paper layer structure. On the other hand, if the freeness exceeds 650 ml, the sheet becomes too low in density, and delamination occurs during the pressing process during paper making, and balloon-like swelling tends to occur. In addition, the stock which shows 200-650 ml freeness in a re-disaggregation state can be 250-700 ml by Canadian standard type freeness irrespective of the pulp raw material used.
Further, measuring the freeness of the used pulp by re-disaggregating the base paper is effective for grasping necessary pulp characteristics from a product exhibiting good operability in a single hour.

The pulp raw material used for the low-density layer can be arbitrarily selected, but it is preferable that the pulp raw material is easy to obtain a low-density paper layer. Specifically, mechanical pulp is mentioned as such a pulp. Mechanical pulp includes GP, TMP, RGP and the like, and TMP and RGP are particularly preferable. Among them, those using radiata pine, Southern pine, Douglas fir, etc. as raw materials can obtain a low-density paper layer due to the rigidity of the fibers and are difficult to deform, and there is little decrease in density during press molding. Therefore, it is particularly preferable.
In the present invention, pulp that has been partially chemically treated, such as pulp obtained by adding chemicals during mechanical crushing or pulp that has undergone a bleaching step, is also handled as mechanical pulp. Furthermore, the thing which gave the density reduction characteristic to the pulp by chemical processing, such as mercerized pulp and a curled fiber, can also be used conveniently.
In the present invention, the above-described pulp is mainly used to constitute the low-density layer, but in addition, chemical pulp made from commonly used wood, or chemical pulp made from various non-wood materials, etc. It is also possible to mix and use as appropriate.
In any case, in the present invention, various pulps are selected so that the density of the low density layer is 0.2 g / cm ³ or more and less than 0.7 g / cm ^3, and a plurality of types are blended as necessary. It is desirable to use it.
In the present invention, it is more 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.

In the present invention, a release agent layer is provided on at least one side of the base paper obtained as described above.
As a method for forming the release agent layer, a method using a release agent solution is preferable. The release agent solution can be applied by a known coating equipment arbitrarily selected from a gate roll coater, a bar coater, a roll coater, an air knife coater, a blade coater and the like. More preferably, the coating is performed by a gravure coater or a bar coater because a low concentration and low viscosity coating is applied.
The release agent layer of the present invention is preferably formed from a silicone resin or a fluorine-based resin from the viewpoint of safety with respect to foodstuffs and the peelability from foodstuffs. Most preferably used.

In the present invention, the base paper for forming containers preferably has gas permeability.
The reason is that when the paper-made container made of the base paper is used as a baking mold, the food material contains almost moisture, and a large amount of water vapor is generated during cooking. Further, a large amount of gas such as carbon dioxide is generated from baking powder contained in bread, baked confectionery and the like. Therefore, it becomes possible to avoid the deformation | transformation of a container and the influence on the external appearance of a foodstuff by having appropriate gas permeability | transmittance to a container.
Also, when the water vapor permeability is not sufficient, the escape of water vapor that occurs during cooking is hindered, so the water vapor tends to escape suddenly in the thickness direction of the paper in the container with increased pressure. A pinhole, peeling, etc. may generate | occur | produce in the provided release agent layer, As a result, there exists a possibility that the mold release property of the foodstuff after cooking may deteriorate.
In addition, when the air permeability is not sufficient, since the high-temperature gas outside the container does not reach the inside of the container during cooking, there is a problem that the food is prevented from being burnt or uniform heating is prevented. Such a problem can be dealt with by making a hole in the bottom portion of the container, but there is a possibility that an extra step is required or the appearance of the food is adversely affected.
In the present invention, the air permeability (JIS-P8117) required as a forming container base paper for the above reason is specifically 100 to 5000 seconds. If it exceeds 5000 seconds, the air permeability and water vapor permeability are not sufficient, and there are problems that the food inside is not scorched during cooking, or pinholes are generated in the release agent layer. Moreover, in the case of less than 100 seconds, the release agent layer is not sufficiently formed, and when used as a baking mold, the releasability from food is not exhibited.

In the present invention, the release agent layer is formed from a silicone resin, a fluorine-based resin, or a resin containing these.
Specific examples of the fluorine-based resin that can be used for forming the release agent layer in the present invention include polytetrafluoroethylene resin, 4-fluoroethylene-6-fluoropropylene copolymer resin, and ethylene-4 fluoride. An ethylene copolymer resin, a polyvinylidene fluoride resin, a polyvinyl fluoride resin, or the like can be used. These can be used alone or in admixture of two or more.

In addition, as a silicone resin that can be used to form the release agent layer in the present invention, specifically, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, diphenyldichlorosilane, phenyltrichlorosilane, methylvinyldichlorosilane, and the like. Examples include hydrolysis and polymers. These can be used alone or in admixture of two or more.
Moreover, the form of the silicone resin can be any of a solvent type, a solventless type, and an emulsion type. Of these, the solventless type is preferred from the viewpoint of odor and safety.
The coating amount of the silicone resin is preferably 0.5 to 3.0 g / ^{m 2,} if the coating amount is less than 0.5 g / ^{m 2,} poor peelability with food, also 3. When it exceeds 0 g / m ² , not only the economic efficiency is impaired, but also gas permeability and water vapor permeability are impaired, which is not preferable.

In the present invention, in order to prevent the release agent liquid from penetrating into the base paper and efficiently apply it, and to effectively exhibit the release performance, between the base paper and the above-mentioned release agent layer. It is preferable to provide an undercoat layer. The undercoat layer is particularly preferably a water-soluble resin such as polyvinyl alcohol or polystyrene-acrylic copolymer, or an aqueous emulsion from the viewpoint of effectively preventing penetration of the release agent without reducing air permeability.
Moreover, 0.2-2.0 g / m < ² > is suitable for the coating amount of the said undercoat, More preferably, it is 0.5-1.0 g / m < ² >. When the coating amount is less than 0.2 g / m ² , the peelability from food is poor, and when it exceeds 2.0 g / m ² , gas permeability and water vapor permeability are impaired, which is not preferable.

Next, press forming of the base paper for forming containers and a paper forming container obtained by press forming will be described.
<About molding method>
(1) Moisture adjustment of base paper As a method for producing a paper-molded container of the present invention, a base paper for a forming container is punched into a container blank sheet, ruled lines are put in necessary places, and the blank sheet is formed into a press mold composed of a male mold and a female mold. A manufacturing method called press molding (drawing molding) is employed, in which molding is performed by heating and pressing.
At this time, it is preferable that the base paper for forming containers is preconditioned to adjust the water content of the base paper. The moisture content of the base paper is preferably in the range of 10 to 20%, preferably 11 to 17%, more preferably 12 to 15%, and most preferably 12.5 to 14.5%. The water content of the base paper refers to the weight percent of water with respect to the absolute dry mass of all pulp in the base paper. When the water content of the base paper is within this preferred range, plasticization of the base paper for forming containers occurs, the formability is improved, and the destruction of the paper layer during forming is reduced. As a result, a molded container having a greater depth, a smooth and beautiful appearance, and a high rigidity can be obtained. If the moisture content of the base paper is less than 10%, sufficient rigidity cannot be obtained in the molded body. If the base paper content exceeds 20%, blisters are generated on the molded base paper and the paper layer of the base paper is peeled off. It takes a long time to produce a problem such as a decrease in productivity, which is not preferable.

(2) Molding method Next, a process for producing a paper molding container from a blank sheet by press molding will be described.
In the present invention, press molding is performed by a pair of press dies. The pair of heating press molds are a convex mold having a convex shape corresponding to the inner volume of the molded product and a concave mold having a concave shape corresponding to the outer shape of the molded product. The pair of pressing dies can press the molding container by moving at least one of the dies in the front-rear or vertical direction.

In the present invention, at the time of pressing, it is preferable to heat either or both of the blank sheet and the pressing mold. As a heating method of the blank sheet, any means such as high frequency heating, hot air heating, infrared heating, etc. is used.
Further, as the mold heating means, the press mold is generally provided with an electrothermal heating device and heated, but it can be heated by applying a high frequency by providing a high frequency oscillator. Moreover, both can also be used together.

  Further, the heating temperature at the time of molding is preferably in the range where the processed base paper is 100 to 150 ° C, more preferably 110 to 140 ° C. If it is less than 100 ° C., it takes time for molding and productivity is lowered. On the other hand, when the temperature exceeds 150 ° C., blisters are likely to be generated particularly when the water content of the base paper is high.

  The container that has been press-molded may be taken out of the mold and air-cooled. However, in order to improve the dimensional stability, it is also preferable that the high-temperature container is fixed and cooled to the cooling mold for a certain period of time.

  As a material for the heating press mold, a known material such as aluminum or an aluminum-based alloy can be appropriately selected and used.

  As a method of operating the mold, a conventionally known mechanism such as a hydraulic pressure, an air pressure, a cam mechanism, or the like can be appropriately employed. As a method of controlling the clearance between the upper die and the lower die at the time of press molding, in the case of hydraulic pressure or air pressure, each pressure can be controlled by computer control according to the thickness of the molded product. In addition, the position of the stopper can be controlled. In the case of the cam mechanism, it can be controlled by a pre-designed cam shape and mold lowering speed.

The pressure during press molding is preferably in the range of 10 to 100 kgf / cm ² . When the pressure is lower than 10 kgf / cm ^2, the compression deformation of the ruled line portion may be insufficient, and when it exceeds 100 kgf / cm ² , the paper layer of the folded wrinkle portion may be broken, which is not preferable.
About the press time at the time of press molding, the range of 2-30 seconds is preferable from the point of a moldability and workability | operativity.

<Base paper characteristics under high temperature and high humidity>
Under high-temperature and high-humidity conditions, such as during press molding, the breaking strength (tensile strength) of the forming container base paper becomes weak and breaks with a small force. Further, under high humidity conditions, the higher the temperature, the smaller the elongation at break, that is, the tendency to break easily. For this reason, the tensile properties of the base paper at high temperatures and high humidity are important requirements for drawability, 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 research, the present inventors have found that, under the conditions of a temperature of 23 ° C. and a moisture content of 14% by weight, a forming container base paper satisfying the following conditions can be drawn at high temperature and high humidity. I found it suitable.
(1) Longitudinal breaking elongation (JIS-P8113) is 2%, more preferably 3% or more.
(2) The tensile modulus in the longitudinal direction is in the range of 1000 to 2000 MPa, more preferably 1200 to 1800 MPa.
The moisture content in the paper refers to a value obtained by dividing the moisture weight in the paper by the total weight of the paper (pulp + additive + moisture) at the time of measuring elongation and elastic modulus.
In addition, the said measurement is a measurement in the state of the base paper in which a coating layer does not exist.

If the elongation at break in the machine direction at a temperature of 23 ° C. and a moisture content in the paper of 14% by weight is less than 2.0%, there is a possibility that the film may break due to low stretchability during press forming. There is.
In addition, when the tensile elastic modulus at a temperature of 23 ° C. and a moisture content in the paper of 14% by weight is set to a range of 2500 MPa or less, the fluidity of the pulp fiber of the forming processed paper is increased, and the paper layer breakage of the folded wrinkle portion at the time of molding is reduced. As a result, a molded body having high strength can be obtained. When the tensile elastic modulus is less than 1000 MPa, there is a possibility that the problem of insufficient rigidity of the molded container may occur.

<About the shape of the container>
A paper molding container targeted by the present invention is a container obtained by drawing (pressing) a piece of paper with a pair of convex and concave press dies.
The upper part of the container is open, and the upper edge is typically a form having a flange. Also, the flange may be curled. Further, the container may have a form without a flange. The bottom may be closed or open.

Note that the paper-molded container obtained by press-molding the base paper for the container according to the present invention has a smooth surface, a beautiful appearance, and a higher degree of freedom in shape than those using conventional base paper. It can be a container. That is, it is possible not only to obtain containers of various shapes that are impossible with conventional paper containers, but also to obtain containers having complicated designs such as letters, figures, and even cartoon characters.
By using such a paper-molded container as a baking mold, it is possible to produce foods having a more beautiful appearance and complex shapes having a wide variety of shapes.

As the outer shape of the plan view of the paper molding container, a square, a rectangle, a circle, an ellipse or the like can be arbitrarily manufactured. For each shape, the corners are usually rounded. An example of the press-molding container of the present invention is shown in FIGS. 1 and 2 as a sketch.
Further, when the paper molding container is used as a baking mold, it is possible to provide a hole on the bottom surface. Providing a hole in the bottom makes it easier for heat to be transmitted during cooking, and makes it easier for food to be burnt or baked, and supplements gas permeability and water vapor permeability. Since the gas to escape is easy to escape, there is an advantage that the internal pressure becomes too high to prevent the baking mold and the food produced thereby from being deformed.
Further, in a paper molding container used as a baking mold, the bottom surface portion is not necessarily required, and may be, for example, a cylindrical shape (FIG. 3). In such a case, it is preferable that the bottom surface is manufactured by stamping after press molding or simultaneously with press molding. Moreover, in the case of a baking mold having a shape having no bottom portion, generally, a method is used in which the baking molds are arranged on a top plate of a cooking utensil such as an oven, followed by filling with food materials and cooking.

In addition to the press molding described above, the base paper for a forming container of the present invention can be formed into an arbitrary shape such as a box or a tray using an ordinary box making machine as in the case of general paperboard.
In addition, when processing the forming base paper of the present invention into a tray carton shape and using it as a baking mold, a blank sheet (FIG. 4) is divided into a bottom surface and a side surface by ruled lines, the side surface portion is folded, The tray carton (Fig. 5) is formed by folding the corners of the side surface and overlaying them and joining them to the outside of the side surface by means such as gluing. The bottom and side surfaces are composed of a single blank sheet. This is particularly suitable because the contents do not leak out of the seam.
Incidentally, the molded base paper of the present invention uses kraft pulp or waste paper pulp as a paper material, and there is no difference in density between layers even in the case of multilayer papermaking, and all layers are denser than the base paper for molded containers of the present invention. The paper is less likely to tear even if the ruled line is deeply inserted in the carton molding than the ordinary paperboard made of paper. By forming the ruled line deeply, it becomes difficult to form a gap in the bent and joined portion, so that the molding accuracy is improved. Therefore, it is possible to obtain a paper molded container having a more uniform shape by using the base paper for a molded container of the present invention. Further, when forming ruled lines, the formability of the paper is good, so there is an advantage that the silicone film is not damaged.
In addition, the tray carton container obtained from the molded base paper of the present invention has a low density and a thickness direction when the same load is applied, even if the basis weight is the same as that of the above-described ordinary paperboard. Since the amount of compressive deformation is large, a ruled line to be formed as a crease when forming a tray carton can be deeply inserted, so that the shape stability when the tray carton is formed is excellent. Therefore, the durability at the time of repeated use as a baking mold is extremely excellent.
The shape change of the paper molding container can be easily performed by adjusting the shape at the time of blank sheet punching, the position of the ruled line, and the bending processing molding machine.

Hereinafter, the present invention will be described more specifically with reference to examples.
<Example 1>
Using a disc refiner, commercial NBKP was beaten to 550 mlcsf (Tappi T-227 Canadian standard type), radialatapine TMP was beaten to 300 mlcsf, and commercial NUKP was beaten to 550 mlcsf.
These were a stock, first layer NBKP40g / m ² using a multi Extract alignment paper machine, the second layer TMP260g / m ^2, the third layer NUKP50g / paperboard 350 g / ^{m 2} consisting of three layers of m ² Paper making was performed to obtain a 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 measurement methods described below.
The base paper was coated with a silicone resin release agent (KS835, solvent type: manufactured by Shin-Etsu Chemical Co., Ltd.) using a test gravure coater at a solid content of 2.0 g / m ² to obtain a base paper for molded containers of the present invention. .
Moreover, it shape | molded into the baking mold shape by press molding, and obtained the paper-made container.
The shape of the paper molding container obtained above was as shown in FIG. 1, and the size of the upper opening was approximately a square of 80 mm × 80 mm and the depth was 30 mm.

<Example 2>
The first layer NBKP40g / m ^2, the second layer TMP200g / m ^2, except that a third layer NUKP40g / paperboard 280 g / ^{m 2} consisting of three layers of m ² was obtained a substrate paper papermaking, Example In the same manner as in No. 1, a base paper for a forming container according to the present invention and a paper forming container were obtained.

<Example 3>
The first layer NBKP40g / m ^2, the second layer TMP240g / m ^2, except that a third layer NUKP50g / paperboard 330 g / ^{m 2} consisting of three layers of m ² was obtained a substrate paper papermaking, Example In the same manner as in No. 1, a base paper for a forming container according to the present invention and a paper forming container were obtained.

<Example 4>
The base paper obtained in Example 1 was coated with 0.5 g / m ^{2 of} solid content of PVA (Denkapoval PVA117, manufactured by Denki Kagaku Kogyo Co., Ltd.) as an undercoat layer, and the same as that used in Example 1 A silicone release agent was applied with a test gravure coater to a solid content of 1.5 g / m ² to obtain a base paper for a molding container and a paper molding container.

<Comparative Example 1>
On the surface of the base paper obtained in Example 1, 25 g / m ² of polybutylene terephthalate (PBT) resin (Duranex, manufactured by Polyplastics) was laminated using an extrusion laminating machine to form a base paper for forming containers. . Further, a paper-molded container was obtained from the base paper for molded container by press molding in the same manner as in Example 1.

<Comparative example 2>
Using a disc refiner, commercially available LBKP was beaten to 300 mlcsf.
Using the LBKP and the NBKP and NUKP materials obtained in the same manner as in Example 1, the first layer NBKP 40 g / m ² , the second layer LBKP / NBKP = 70/30, 240 g / m ² , the third layer A paper board of 330 g / m ^{2 having} a three-layer structure of NUKP 50 g / m ² was made in the same manner as in Example 1 to obtain a 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 measurement methods described below.
On the surface of the base paper, 20 g / m ² of polymethylpentene (PMP) resin (TPX, manufactured by Mitsui Chemicals) was laminated using an extrusion laminating machine to obtain a base paper for a forming container. Further, a paper-molded container was obtained from the base paper for molded container by press molding in the same manner as in Example 1.

<Comparative Example 3>
Using each of the NBKP, NUKP, and LBKP materials obtained in Comparative Example 2 obtained in the same manner as in Example 1, the first layer NBKP 40 g / m ² , the second layer LBKP / NBKP = 70/30, 220 g / m ^2, and a third layer NUKP50g / paperboard 310 g / ^{m 2} consisting of three layers of m ² and papermaking in the same manner as in example 1 to obtain a 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 measurement methods described below.
On the surface of the base paper, 25 g / m ² of polybutylene terephthalate (PBT) resin (Duranex, manufactured by Polyplastics) was laminated using an extrusion laminator to obtain a base paper for a forming container. Further, a paper-molded container was obtained from the base paper for molded container by press molding in the same manner as in Example 1.

<Comparative example 4>
A commercially available aluminum baking mold (product number 281; manufactured by Toyo Aluminum Echo Products) was evaluated as a baking mold.

<Comparative Example 5>
A silicone resin release agent was applied to the surface of the base paper obtained in Comparative Example 3 in the same manner as in Example 1 to obtain a base paper for molded containers. Using this, a paper molded container was obtained by press molding in the same manner as in Example 1.

[Evaluation methods]
The base paper for forming containers obtained in Examples 1 to 4 and Comparative Examples 1 to 4 and the paper forming containers were evaluated by the following methods. The results are shown in Table 1.
(1) Density of each paper layer The base papers obtained in Examples and Comparative Examples were peeled from each other layer by the delamination method described in the peel strength test method for the paperboard making layer of JIS-P8139, The thickness (mm) and basis weight (g / m ² ) of each layer are determined. In addition, since the thickness of each peeled layer is fluffed by peeling and becomes thicker than the actual thickness, the correction factor value is calculated by the following method, the thickness value of each layer after peeling is corrected, and each layer The density of is calculated.
Correction factor value = total thickness before peeling / total value of each layer after peeling Peeling of each layer is difficult with the delamination method described in the peeling strength test method for the paper-sheet laminated layer of JIS-P8139 In such a case, the multi-layered 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. Each peeled layer is dried to determine the thickness (mm) and basis weight (g / m ² ). Thereafter, the correction factor value is similarly calculated to correct the thickness of each peeled layer, and the density of each layer is calculated.

(2) Tensile strength A specimen obtained by cutting the base paper obtained in Examples and Comparative Examples into a width of 15 mm and a length of 250 mm in each of the flow direction and the width direction is adjusted for 24 hours or more at 23 ° C. and 50% RH. After moistening, measurement was performed at a tensile speed of 20 mm / min according to JIS-P8113 using a strograph M2 type tester (manufactured by Toyo Seiki Seisakusho).

(3) Elongation at break A test piece obtained by cutting the base paper obtained in Examples and Comparative Examples into a width of 15 mm and a length of 250 mm in the flow direction and the width direction, respectively, was adjusted for 24 hours or more at 23 ° C. and 50% RH. After moistening, measurement was performed at a tensile speed of 20 mm / min according to JIS-P8113 using a strograph M2 type tester (manufactured by Toyo Seiki Seisakusho).

(4) Critical compressive stress A test piece obtained by cutting the base paper obtained in Examples and Comparative Examples into a width of 12.7 mm and a length of 152.4 mm in the flow direction and the width direction, respectively, at 23 ° C. and 50% RH. Measure the compressive strength A in accordance with JIS-P-8126 using a digital ring crush tester X-1104 (manufactured by Orientec), and further adjust the load partial area of the test piece when measuring the compressive strength. B was calculated and calculated from the following formula.
Critical compressive stress = A / B
Where critical compressive stress unit: MPa
Compressive strength unit: N
Area of load part of test piece = thickness of test piece (mm) × 152.4 mm
(The thickness of the test piece is a value measured according to JIS-P8118 for a sample conditioned for 24 hours or more under the conditions of 23 ° C. and 50% RH)

(5) Amount of compressive deformation A test piece obtained by cutting the base paper obtained in Examples and Comparative Examples into 50 mm × 50 mm was conditioned at 23 ° C. and 50% RH for 24 hours or more, and then a strograph M2 type test Using a machine (Toyo Seiki Seisakusho), compress one test piece in the thickness direction at a compression rate of 1.0 mm / min, draw a stress-strain curve, and compress the amount (strain amount) at a compressive stress of 20 kgf / cm ² ) Was measured.

(6) Air permeability The base paper for forming containers obtained in each Example and Comparative Example was measured according to JIS-P8117.

(7) Press-formability The presence or absence of the crack of the paper layer surface of the corner part of the press-molded paper-made container, and the smoothness of the flange part were evaluated. A paper layer with no cracks and a flange part that has been crushed smoothly. ○, a paper layer with a crack at one of the corners. A paper layer with two or more cracks. Or the thing where the flange is not smooth was set as x.

(8) Cooking suitability A baking mold obtained by press-molding a base paper for forming containers was filled with frozen bread dough (made by Ajinomoto Co.) and subjected to a cooking test at 220 ° C. for 15 minutes in an oven to evaluate cooking suitability. .
In the evaluation method, the portion of the baked bread that was in contact with the bottom of the container was scorched and completely burned, and the scorched and semi-baked one was rated as x.

(9) Releasability The cooking test of (8) above was repeated 20 times for the same container to evaluate the releasability between the bread and the baking mold. The evaluation method is that the releasability between the baked bread and the baking mold (the state where the bread does not peel and the dough does not adhere to the baking mold) is maintained even at the 20th time, ○, the releasability at the 15th time or more Was evaluated as “C”, and when X was less than 15 times, the releasability was impaired as “x”.

(10) Shape stability When the heating cooking test of evaluation (8) is repeated 20 times, the shape distortion of the paper molded container is visually observed each time, and even after 20 times use, compared with before the test. The case where almost no distortion was observed was indicated by “◯”, the case where distortion was observed after 20 times of use was indicated by Δ, and the case where distortion was observed after several uses was indicated by “x”.

  In the following, an embodiment formed into a tray carton shape is shown.

<Example 5>
Using the base paper for forming containers obtained in Example 1, punching into a predetermined shape (FIG. 4), dividing into a bottom surface and a side surface by ruled lines, folding the side surface portion, and further forming a corner of the side surface portion The container was folded and overlapped, and the container outer side surface and the corner were bonded with a vinyl acetate adhesive to obtain a paper molded container (FIG. 5).

<Comparative Example 6>
Using the forming container base paper obtained in Comparative Example 5, a paper forming container was obtained in the same manner as in Example 5.

The paper molded containers obtained in Example 5 and Comparative Example 6 were evaluated in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 5 described above (excluding press formability).
The results are shown in Table 2.

It is a perspective view of the Example obtained by press-molding the base paper for forming containers of this invention. It is a perspective view of the other Example obtained by press-molding the base paper for forming containers of this invention. It is a perspective view of the other Example obtained by press-molding the base paper for forming containers of this invention. It is a figure which shows the blank sheet of the other Example of this invention. It is a perspective view of the other Example of this invention obtained by shape | molding the blank sheet | seat of FIG. 4 in tray carton shape.

Claims (7)

A release agent layer is provided on at least one surface of a base paper satisfying the following four conditions (1) to (4), and the air permeability (JIS-P8117) is 100 to 5000. A base paper for forming containers.
(1) Tensile strength (JIS-P8113) is 2.0 kN / m or more.
(2) Elongation at break (JIS-P8113) is 1.5% or more.
(3) The critical compressive stress defined by the following formula is in the range of 1 to 10 MPa.
Critical compressive stress = A / B
However, A is the compressive strength according to JIS-P8126,
B shows the load part area of the test piece at the time of compressive strength measurement, respectively.
(4) 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 base paper for molded containers according to claim 1, wherein mechanical pulp is included as a raw material pulp of the base paper. Dense layer of density 0.7~0.9g / cm ^3, and has a low density layer density of less than 0.7 g / cm ^3, a basis weight is 100 to 500 g / m ^2, the overall density of 0.4 ~0.7g / cm ^3, and the low-density layer is mechanical pulp, curled fibers, and at least a pulp selected from one to at least one surface of a substrate sheet which is mainly composed release agent layer of mercerized pulp is provided The base paper for molded containers characterized by having an air permeability (JIS-P8117) of 100 to 5000.   The base paper for molded containers according to any one of claims 1 to 3, wherein the release agent layer is formed from a silicone resin.   The base paper for forming containers according to any one of claims 1 to 4, wherein an undercoat layer is provided between the base paper and the release agent layer.   A paper molded container, wherein the base paper for molded containers according to claim 1 is molded by press molding.   A paper molded container, wherein the base paper for molded containers according to claim 1 is molded into a tray carton.

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