JP3800073B2 - Molding base paper and paper molding container using the same - Google Patents

Description

【００４９】
【表２】

【００５０】
【発明の効果】
本発明によって、耐水性を有しながら生分解性を有し、プレス成形適性に優れ外観が美しく強度が十分で、しかもガスバリアー性を有する紙製成形容器が得られるプレス成形用の成形加工原紙、及び紙製成形容器を得ることが可能となった。
【００５１】
【図面の簡単な説明】
【図１】紙製成形容器のブランクシートの平面図
【図２】プレス成形した紙製成形容器の斜視図
【符号の説明】
１：罫線[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to water-containing contents, particularly foods such as fresh foods such as meat, vegetables and fresh fish, or various foods such as lunch boxes, prepared dishes, frozen foods, confectionery, noodles, soups, soups and beverages. A paper molded container that is suitable for containing processed foods, has water resistance and gas barrier properties, is excellent in press molding, and has a beautiful appearance.GainThe present invention relates to a molded base paper and a paper molding container.
[0002]
[Prior art]
Conventionally, as a molded container such as a tray used for water-containing contents, particularly foods, a molded container made of various resins, for example, molded polystyrene beads are molded, or expanded polystyrene sheets are press molded. EPS (styrene foam) trays, PS (styrene) trays, PP (polypropylene), PET (polyethylene terephthalate) trays, etc. are widely used. In addition, there is a tray container in which a thin metal such as aluminum is mainly press-formed.
In addition, a paper molding container mainly composed of paper is also widely used. Paper-based materials are widely used in which a base paper is laminated on the surface with various resins such as polyolefin such as polyethylene and polypropylene, polystyrene, polyethylene terephthalate, vinyl chloride, vinylidene chloride, polyvinyl alcohol, and ethylene vinyl alcohol as a resin layer. ing.
Paper molded containers having such a resin layer are widely used because they are inexpensive and lightweight, and have excellent oxygen barrier properties and water vapor barrier properties.
[0003]
[Problems to be solved by the invention]
However, when the conventional base paper for forming is made into a paper-made container by press molding, the depth and smoothness of the container obtained and the strength of the container are insufficient.
For the above reasons, there has been a demand for a molded base paper that has a gas barrier property, has excellent press molding suitability, has a beautiful appearance, and has a sufficient strength.
[0004]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention takes the following method.
  That is, the present invention is densityIs 0.3 g / cm ³ Beyond0.6g / cm³ Less thanLow density layer, and 0.7 g / cm³High density layerAnd the wholedensityBut0.4 to 0.7 g / cm³ The basis weight is 90 to 500 g / m ² Forming base paper composed of a multilayer paper, and a gas barrier layer is laminated on at least one side of the multilayer paperFor press formingThis is a processed paper.
[0005]
A second aspect of the present invention is the molded base paper according to the first aspect of the present invention, wherein the low density layer is mainly composed of a pulp selected from at least one of mechanical pulp, curled fiber, and mercerized pulp.
[0006]
  The third aspect of the present invention is that the gas barrier layer is a thermoplastic resin.ByBeen formedThe present inventionIt is a forming processed base paper described in 1-2.
[0007]
  4th of this invention is a gas barrier layer.ButEthylene vinyl alcohol resincontainsIt is a shaping | molding base paper of this invention 1-3.
[0008]
A fifth aspect of the present invention is a paper-made container formed by press-molding the forming base paper of the first to fourth aspects of the present invention.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
  The forming base paper in the present invention is obtained by multilayered paper making in order to obtain the required rigidity. That is, it is composed of multilayer paper having at least two layers. In the present invention, the density of the entire multilayer paper is 0.4 to 0.7 g / m.³It is necessary to be. In addition, in order to obtain a multilayer paper having a low density, that is, a bulky and high rigidity, the multilayer paper has a density ofIs 0.3 g / cm ³ Beyond0.6g / cm³ Less thanLow density layer, and density 0.7 g / m³More preferably, 0.7 to 0.9 g / m³The high-density multilayer paper is obtained by supplementing the decrease in Young's modulus due to the low-density layer with the high-density layer.
[0010]
In the present invention, the multilayer paper described above may have at least one low-density layer and a high-density layer. However, in order to obtain a bulky and high-stiffness multilayer paper, the high-density layer is made of multilayer paper. It is desirable that the outer layer is at least one side. Further, it is more effective that the outer layers on the front and back sides of the multilayer paper are both high-density layers, and the middle layer, which is a low-density layer, is sandwiched between the outer layers.
In the present invention, the outermost layers on both sides of the multilayer paper are referred to as outer layers, and the middle layer refers to one layer or all of a plurality of layers sandwiched between outer layers.
[0011]
The stiffness S of a sheet of paper, paperboard, etc., when the sheet is considered as a cantilever, S = E · I / B · W = E · T³/ 12 · W, (E: Young's modulus MPa, I: sectional moment of inertia N · cm²B: 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.
[0012]
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.
[0013]
  From this, the density of the low-density layer is0.3 g / cm ³ Beyond0.6g / cm³ Less than,Most preferably 0.3g / cm ³ Beyond0.5g / cm³ Less thanIt is. The density of the low density layer0.3 g / cm ³ Less thanWhen it is made, the fall of the interlayer strength is severe, and 0.6 g / cm³Exceeds the density of 0.4 to 0.7 g / cm³It can not be.
[0014]
In the present invention, the density of the high-density layer is 0.7 g / cm.³That is necessary. More desirably 0.7-0.9 g / cm³It is. 0.7g / cm³If it is less than that, the Young's modulus of the high-density layer decreases, and the rigidity of the present invention cannot be expected to improve. Also, density 0.9g / cm³In the case of exceeding the above, the high density layer becomes too tight, and it may be difficult to obtain a higher density layer at the paper making stage. Furthermore, there may be no press moldability.
[0015]
In the present invention, as described above, in order to improve rigidity, it is preferable to form a low-density layer as an intermediate layer and to form an outer layer with a higher density on both sides to improve the Young's modulus, but only one outer layer is formed. A high-density layer is also possible. By this method, without reducing the overall thickness, and during the making of paper, it is possible to prevent the air inside the paper layer or between the paper layers from permeating through the outer layer and preventing the phenomenon of peeling between layers. You can also.
[0016]
Although there is no special restriction | limiting in the kind of pulp used for an outer layer, The thing which made the beating degree of N material (coniferous) pulp, such as NUKP and NBKP, high, and does not lose rigidity is especially desirable. In addition, in order to make this invention effective, the basic weight of the outer layer made into the high-density layer is 15-100 g / m.²It is preferable that That is, 15g / m²If it is less than this, it is difficult to obtain a paper layer having a high Young's modulus, and it is also difficult to produce paper. On the other hand, the outer layer is 100 g / m²Exceeding the lower limit, the basis weight of the low density layer is relatively reduced, so the density of the entire multilayer paper is increased, and 0.4 to 0.7 g / cm.³This is because it is difficult to achieve the above range.
[0017]
The production of the multilayer paper of the present invention is performed using a multi-layer stitching former in the same manner as the production of general paperboard. For example, several tens of g / m on multiple wire parts of about 10 stations²The wet slurry is formed by sequentially laminating pulp slurries corresponding to the dry rice tsubo.
More specifically, it is 40 g / m for the wire part that first forms a paper layer as an outer layer.²A pulp layer of a certain degree is formed, dehydrated and then transferred to a blanket. Next, in the middle layer, a paper layer is similarly formed with another wire part, and the step of laminating the required number of layers on the outer layer is repeated to form the middle layer. Finally, a paper layer as the other outer layer is formed to obtain the shaped base paper of the present invention.
[0018]
In the present invention, as the pulp raw material used as the raw material for the low density layer, it is preferable to use a pulp material having a freeness in the range of 200 to 650 ml in the re-disaggregation state in accordance with the Canadian standard form of JIS P 8121.
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 is likely 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.
[0019]
Moreover, it is preferable that the pulp raw material used for the low density layer is mainly composed of a pulp from which a low density paper layer can be easily obtained. Specifically, mechanical pulp exists as an example of such a pulp and is preferably used.
Mechanical pulp is usually pulp produced by pulverizing wood, especially N material, and then disaggregating it. There are GP, TMP, RGP and the like, and TMP and RGP are more preferable. Among them, Radiata Pine, Southern Pine, Douglas Fir, etc. have the characteristic that the fiber is rigid and difficult to deform, so it is possible to obtain a low density paper layer, and there is little decrease in density during press molding, so the low density layer Particularly preferred as a raw material. It is also possible to use various non-wood raw materials such as kenaf, straw, bamboo and sugarcane sugarcane bagasse. 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.
[0020]
  Furthermore, those obtained by imparting density reduction properties to the pulp by chemical treatment, such as mercerized pulp and curled fiber, can be suitably used as the raw material. In the present invention, as the raw material of the low-density layer, the above-mentioned pulp suitable for obtaining a low-density paper layer is mainly used, but in addition, chemicals using various kinds of commonly used wood or various non-woods as a raw material. It is also possible to mix and use pulp appropriately. In the present invention, the density of the low density layer is0.3 g / cm ³ Over 0.6g / cm ³ Less thanThus, it is possible to select a pulp raw material and mix and use a plurality of types as required.
[0021]
In the present invention, fillers, pigments, dyes, sizing agents, yield improvers, paper strength enhancers, and the like used in general papermaking can be optionally added to the pulp raw material as necessary. .
For example, sulfuric acid band, rosin internal sizing agent, petroleum resin sizing agent, maleic anhydride sizing agent, styrene acrylic acid sizing agent, styrene acrylic sizing agent, glue, starch, CMC, PVA, AKD, etc. Water resistance of the multilayer paper of the present invention by internally adding a water repellent such as an agent, fluororesin, polyamide resin, wax emulsion, and latex such as urea-formaldehyde resin, melamine-formaldehyde resin, dialdehyde starch, SBR Sexuality can be strengthened.
They can also be added by spraying between the paper layers during the paper making process, or by coating on the surface of the base paper during or after paper making.
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.
In addition, the paper machine used in the production of the present invention may be any machine that can make a combined paper and a multi-layer paper, and a round net type, a long net type, etc. are appropriately used. it can.
[0022]
The forming base paper in the present invention can be provided with a coating layer composed of a pigment and an adhesive on one side or both sides as required. By providing such a coating layer, good printability can be imparted to the surface of the forming raw paper.
As the pigment used in the coating layer, known pigments such as calcium carbonate, kaolin, clay, talc, titanium oxide, and plastic pigment can be arbitrarily used.
As the adhesive used for the coating layer, known ones such as starch, casein, SBR latex, and polyvinyl alcohol can be arbitrarily used.
These coating layers can be formed in a single layer or multiple layers. The total coating amount is 20-30 g / m.²Degree is desirable.
Moreover, when providing such a coating layer, it is still more preferable that the layer immediately under a coating layer raises a beating degree, and makes the surface smoother.
Such a coating layer can be applied by appropriately using various known coating apparatuses. Moreover, it is possible to provide a printing layer further on such a coating layer.
[0023]
The molded base paper of the present invention is formed by laminating a gas barrier layer on one side or both sides of the above-mentioned multilayer paper in order to prevent deterioration of the contents when used as a molded container, particularly to prevent oxidation by oxygen. To do.
The gas barrier layer can be provided directly on the multilayer paper, or at any location such as on the pigment coating layer or the printing layer.
The gas barrier layer in the present invention is 100 cc / m under conditions of oxygen permeability of 23 ° C. and 50% RH.²-It shall refer to the layer that will be 24 hours or less.
As a method of laminating the gas barrier layer, there are a synthetic resin laminate having a gas barrier property, a coating of a gas barrier paint, and the like, and any method can be selected depending on the situation.
A method particularly suitable for the present invention is a method of laminating a thermoplastic gas barrier resin on the surface of a multilayer paper.
The method for laminating the resin layer on the multilayer paper may be any of commonly used wet lamination, hot melt lamination, extrusion lamination, dry lamination, thermal lamination, etc., and is not particularly limited.
[0024]
Specific examples of the gas barrier resin used in the present invention include vinylidene chloride resin (PVD), polyacrylonitrile resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, polyethylene terephthalate resin, and nylon resin. Among these, vinylidene chloride resin, ethylene vinyl alcohol resin, and polyvinyl alcohol resin are preferable in terms of gas barrier properties and moldability. Among these, ethylene vinyl alcohol resin and polyvinyl alcohol resin are most suitable.
[0025]
The ethylene vinyl alcohol (hereinafter referred to as EVOH) will be described in further detail. EVOH is a saponified product of ethylene and vinyl acetate copolymer. The monomer molar ratio of ethylene and vinyl acetate in EVOH used in the present invention has an ethylene content of 20 to 65 mol%, preferably 25 to 55 mol%. . The saponification degree of the vinyl acetate component is 95 mol% or more, preferably 98 mol% or more.
If the EVOH has an ethylene content of less than 20 mol%, it tends to gel during melt molding, and a molded product such as a beautiful film may not be obtained. In addition, gas barrier properties under high humidity may be deteriorated. On the other hand, when the ethylene content is higher than 65 mol%, the gas barrier property may not be sufficient. Further, when the saponification degree of the vinyl acetate component is less than 95 mol%, it is likely to gel during melt molding as in the case where the ethylene content is less than 20 mol%, and there is a possibility that stable operation for a long time cannot be performed.
[0026]
The MI of EVOH used in the present invention is preferably 0.5 to 15 g / 10 min. Furthermore, EVOH referred to in the present invention may be modified with a copolymerization monomer in the range of 5 mol% or less. As the modifying monomer, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, acrylic acid ester, methacrylic acid ester, maleic acid, fumaric acid, itaconic acid, higher fatty acid vinyl ester, alkyl vinyl ether, N -Vinylpyrrolidone, N-normal butoxymethylacrylamide, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, N- (2-dimethylaminoethyl) methacrylamides or quaternized products thereof, N-vinylimidazole or its A quaternized compound etc. can be illustrated.
[0027]
When EVOH resin is used as a gas barrier layer, it may be laminated on paper as a single resin layer. However, the EVOH layer is used in terms of adhesion strength to paper and water resistance, or moldability when molded into a container. It is preferable to laminate | stack on paper as a multilayer laminated body containing.
Examples thereof include a three-type five-layer coextruded film of hydrophobic thermoplastic resin / adhesive resin / EVOH / adhesive resin / hydrophobic thermoplastic resin. The hydrophobic thermoplastic resin is preferably a polyolefin resin such as polyethylene or polypropylene. The adhesive resin is preferably an acid-modified polyolefin resin. As the multilayer film including the EVOH layer, not only the above-mentioned 3 types and 5 layers, but also 4 types and 7 layers or other resin layers laminated as necessary may be used.
In addition, EVOH resin has a property that the oxygen permeability rapidly decreases when the humidity becomes 80% or more, but when packaging the water activity of the content of 0.8 or more, the EVOH layer is thickened, A multilayer film that prevents moisture absorption of EVOH may be laminated by separately providing a layer containing a hygroscopic agent. The hygroscopic agent is not particularly limited as long as it has a property of absorbing moisture such as silica gel, calcium chloride, sodium acetate, potassium acetate, sodium formate, sodium chloride, sodium benzoate and the like.
[0028]
Further, in order to improve the gas barrier property, EVOH and a flat pigment may be used in combination to improve the gas barrier property by a curved path effect. The flat pigments include phyllosilicate minerals (mica, pyrophyllite, talc, chlorite, septite chlorite, serpentine, stilpnomelane, kaolin),
Examples thereof include graphite, phosphate derivative compounds (zirconium phosphate compounds), chalcogen compounds, smectites, vermiculites, and the like.
[0029]
Moreover, what coated the gas barrier resin on synthetic resin films, such as a polyolefin olefin, may be used as the gas barrier layer of this invention.
As the coating type gas barrier resin, the aforementioned EVOH or PVA, or a gas barrier layer containing EVOH and a flat pigment, PVA and a flat pigment, PVA and polyacrylic acid is suitable. In addition, a gas barrier layer of the present invention may be obtained by applying a gas barrier coating composed of an organic-inorganic composite composed of silicic acid condensate (alkali silicate, hydrolyzed alkoxide silane, or colloidal silica) and EVOH or PVA. Can be used.
The coating equipment for the gas barrier paint is not particularly limited, and a commonly used bar coater, air knife coater, roll coater, blade coater, gate roll, size press, gravure coater, die coater and the like are suitable. The coating amount is determined by the properties and required quality of the gas barrier resin.
[0030]
In the present invention, the synthetic resin layer (the thickness of the resin layer including a resin layer other than the gas barrier resin layer) is preferably 1 to 100 μm, and more preferably 5 to 50 μm. When the thickness of the synthetic resin layer is less than 1 μm, sufficient gas barrier properties and water resistance are not exhibited, and the film strength tends to be insufficient. Moreover, when it is thicker than 100 μm, it is not only uneconomical but also inferior in press molding processability, and the texture of the paper molded container after molding is not preferable.
[0031]
  In addition, the method of forming the forming base paper of the present invention as a paper molding container is a method called drawing, in which the forming base paper is manufactured by press forming.sois there. The shaped processed base paper of the present invention is particularly suitable for the production of a paper molding container by drawing.
[0032]
The basis weight of the molded base paper of the present invention is 90 to 500 g / m²Is preferred. 90 g / m²If it is less than the above, after forming the molded container, the strength is insufficient when the contents are loaded, and the container is distorted or the base paper is broken. 500g / m²In the case of exceeding the range, since the base paper becomes too thick, a high pressure and a molding time are required at the time of the drawing, which causes inconvenience that it becomes uneconomical and inefficient.
[0033]
【Example】
The following examples further illustrate the invention. Unless otherwise specified, the numerical values indicating the concentration, the blending amount, the coating amount, etc. are numerical values based on the mass of the solid component or active ingredient.
<Example 1>
The following three types of pulp shown in (1) to (3) were sequentially combined in this order at a wire speed of 300 m / min using an experimental orientation paper machine manufactured by Kumagai Riki Kogyo.
(1) Commercial NBKP, 450mlcsf, 50g / m²
(2) Radiata Pine TMP, 350mlcsf, 180g / m²
(3) Commercial NBKP, 450mlcsf, 50g / m²
(In addition, each paper material was beaten to a predetermined freeness by a KRK high concentration disc refiner type beater manufactured by Kumagai Riki Kogyo.)
In the case of making the combined paper, starch (ONL510: manufactured by Oji Corn Starch) is used as an aqueous dispersion with a starch concentration of 2.0% on the front side (felt side) of each layer, and the solid content adhesion amount is 1.0 g / m.²After spraying, it was combined.
Next, the wet-paper-like sheet-making sheet obtained above is sandwiched between a monoplastic canvas sheet (Shikishima canvas) at a nip pressure of 10 kg / cm and a speed of 30 m / min with a calendar (manufactured by Yuri Roll Machinery). To process.
The sheet is then dried with a ferro-type cylindrical heating dryer.
The sheet was then conditioned at 20 ° C. and 65% RH, calendered with a calender (manufactured by Yuri Roll Machinery) at a nip pressure of 20 kg / cm and a speed of 20 m / min, and then PVA with a concentration of 8.0% ( Kuraray Poval PVA-KL118 (manufactured by Kuraray) by hand coating 2.0 g / m²Multi-layer paper was obtained by applying heat calendering at 120 ° C. with a nip pressure of 40 kg / cm, a speed of 20 m / min using a calender (manufactured by Yuri Roll Machinery).
After adjusting the humidity of the multilayer paper at 20 ° C. and 65% RH, the basis weight, thickness, density, and Z strength Taber stiffness are measured.
Further, EVOH resin (EPF101B: manufactured by Kuraray Co., Ltd.) was laminated with a film thickness of 40 μm by melt extrusion on the front side of the corrugated base paper, and the melt extrusion temperature was 230 ° C.
The forming base paper is punched into an oval mold, and ruled lines are stamped radially from the center (see FIG. 1).
Using the test press molding machine (manufactured by Daiichi Koki Co., Ltd.), the molded base paper punched out in the above is 130 ° C. and 35 kg / cm in a male / female uneven oval paper tray mold.²Then, a paper-molded container having a major axis of about 20 cm, a minor axis of about 14 cm, and a height of about 4 cm was obtained (see FIG. 2).
[0034]
<Example 2>
The following three types of pulp are used, and when the coating is performed on the surface, the coating liquid shown below is used, and the weight after drying by hand coating with a Meyer bar is 9.0 g / m.², Top coat 10.0g / m²In the same manner as in Example 1, except for drying for 60 seconds in a hot air drier at 105 ° C. (manufactured by Advantech Co., Ltd.), paper was made together.
(1) Commercial NBKP, 450mlcsf, 50g / m²
(2) Radiata pine TMP 300ml csf / commercial NBKP, 150ml csf product = 70/30, freeness after blending 280ml csf, 230g / m²
(3) Commercial NBKP 450mlcsf, 50g / m²
[Contains paint]
Topcoat: Kaolin (Ultra White 90: manufactured by Engelhard) / Calcium carbonate (Brilliant 15: manufactured by Shiroishi Kogyo) / Titanium oxide (TCA333: manufactured by Tochem Products) = 50/35/15, and latex (L1410: manufactured by Asahi Kasei) / Urea phosphate esterified starch (MS4600: manufactured by Nippon Shokuhin Kako) = 15/5. (Number of blending parts based on solid weight, the same shall apply hereinafter)
Undercoat: Kaolin (Caobright: manufactured by Seal) / Calcium carbonate (Softon 2200: Bihoku powdered) = 50/50 and Latex (0668: manufactured by JSR) / Urea phosphate esterified starch (MS4600: manufactured by Nippon Shokuhin Kako) = 15/5.
Subsequently, a molding base paper and a paper molding container were obtained in exactly the same manner as in Example 1, and the measurement and evaluation were performed in the same manner.
[0035]
<Example 3>
Except for using the three types of pulp shown below, paper was made in the same manner as in Example 1.
(1) Commercial NBKP, 450mlcsf, 50g / m²
(2) Radiata pine TMP, 350 ml csf / commercial LBKP, 350 ml csf product = 70/30, freeness after blending 350 ml csf, 200 g / m²
(3) Commercial NBKP 380 ml csf, 50 g / m²
Next, a multilayer paper was obtained in exactly the same manner as in Example 1, and after adjusting the humidity at 20 ° C. and 65% RH, the basis weight, thickness, density, and Z strength Taber stiffness were measured.
[0036]
Next, the gas barrier laminate obtained by the method described later was laminated on the front side of the corona-treated multilayer paper by melt extrusion at 230 ° C. to obtain a forming processed base paper.
The molded base paper was punched into an oval mold in the same manner as in Example 1, pressed to obtain a paper molded container, and similarly measured and evaluated.
[Method for producing gas barrier laminate]
Thermoplastic resin (Admer NF518, MI: 2.4 g / 10 min, density 0.911 g / cm³Melting point 120 ° C. (Mitsui Chemicals) is extruded at a rotational speed of 100 rpm with a twin screw extruder (Ikegai, model PCM-46, L / D 41.5, 10 blocks). ) Was completed, an aqueous solution containing 20% NaCl was injected from the side feed barrel using a pump. The injection amount was such that NaCl was 10% with respect to the thermoplastic resin. After passing the kneading part immediately after the pouring position (6 blocks), a twin screw extruder is attached to the second side feeder barrel, and it is operated idly in order to remove moisture and prevent resin from blowing out due to evaporation.
[0037]
After passing through the next kneading part (block 7), the pressure was set to 70 cmHg by a weak vacuum vent to remove a part of the residual moisture. Further, when the next kneading portion (9 blocks) was passed, the pressure was set to 5 cmHg by a second vacuum vent to remove a part of the residual moisture. After passing through the final kneading portion (block 10), the resin was extruded in a strand shape, passed through water, cooled, and the strand was cut with a pelletizer to obtain hygroscopic compound-containing resin pellets. The moisture content of the pellets was 0.1% or less (the moisture content was determined from the reduced mass when the pellets were dried at 110 ° C. for 3 hours). The amount of NaCl contained in the obtained pellet was 9.5% (obtained from the amount of residue obtained by heating the pellet at 550 ° C. for 3 hours). Moreover, MI of this pellet was 1.5 g / min.
[0038]
This hygroscopic compound-containing thermoplastic resin and EVOH resin (EPF101B, MI 1.3 g / 10 min, 1.19 g / cm³Mp 183 ° C .: Kuraray) and polyethylene (LDPE) resin (LC522, MI 3.8 g / 10 min, density 0.923 g / cm³, Melting point 111 ° C .: manufactured by Nippon Polychem Co., Ltd.), gas barrier laminates were manufactured using a three-type five-layer multilayer coextrusion film forming apparatus (feed block method: manufactured by Ikegai).
The temperature conditions of the extruder during film production were 180 to 220 ° C., and the rotation speed was 32 rpm for the hygroscopic compound-containing thermoplastic resin, 16 rpm for the EVOH resin, and 79 rpm for the polyethylene resin. The structure of the obtained laminate and the thickness of each layer were as follows: LDPE resin 20 μm / hygroscopic compound-containing thermoplastic resin 20 μm / EVOH resin 12 μm / hygroscopic compound-containing thermoplastic resin 20 μm / LDPE resin 20 μm (the thickness of each layer is the cross section of the film) Obtained from an electron micrograph).
[0039]
<Example 4>
Except for using the three types of pulp shown below, paper was made in the same manner as in Example 1.
(1) Commercial NBKP, 450mlcsf, 50g / m²
(2) Commercial mercerized pulp 300 ml csf / commercial NBKP, 150 ml csf product = 70/30, blended freeness 250 ml csf, 200 g / m²
(3) Commercial NBKP 450mlcsf, 50g / m²
Subsequently, a molding base paper and a paper molding container were obtained in exactly the same manner as in Example 1, and the measurement and evaluation were performed in the same manner.
[0040]
<Example 5>
Except for using the three types of pulp shown below, paper was made in the same manner as in Example 1.
(1) Commercial NBKP, 450mlcsf, 50g / m²
(2) Commercially available NBKP, 150 ml csf product / curled fiber (made by Warehauser) 750 ml csf product = 70/30, blended freeness 300 ml csf, 160 g / m²
(3) Commercial NBKP 450mlcsf, 40g / m²
Subsequently, a molding base paper and a paper molding container were obtained in exactly the same manner as in Example 1, and the measurement and evaluation were performed in the same manner.
[0041]
<Example 6>
Except for using the three types of pulp shown below, paper was made in the same manner as in Example 1.
(1) Commercial NBKP, 450mlcsf, 50g / m²
(2) Kenaf TMP, 350mlcsf, 185g / m²
(3) Commercial NBKP, 380mlcsf, 50g / m²
Subsequently, a molding base paper and a paper molding container were obtained in exactly the same manner as in Example 1, and the measurement and evaluation were performed in the same manner.
[0042]
<Example 7>
A polyethylene terephthalate resin with a thickness of 25 μm (Dianite FX-0012, 1.335 g / cm) instead of EVOH on the front side of the base paper for tray³Except for laminating a melting point of 260 ° C. (manufactured by Mitsubishi Rayon), a molded base paper and a paper molded container were obtained in the same manner as in Example 1, and similarly measured and evaluated.
[0043]
<Example 8>
Except for EVOH, a 15 μm thick nylon resin (nylon MXD6P6001, MI 7.0 g / 10 min, melting point 237 ° C .: manufactured by Mitsubishi Gas Chemical Co., Ltd.) was laminated on the front side of the tray base paper, and the same method as in Example 1 Thus, a forming base paper and a paper-made container were obtained, and similarly measured and evaluated.
[0044]
<Comparative Example 1>
Polyethylene (LDPE) resin (LC522, MI 3.8 g / 10 min, 0.923 g / cm) instead of EVOH on the front side of the base paper for tray³, Melting point 111 ° C .: manufactured by Nippon Polychem Co., Ltd.) was obtained in the same manner as in Example 1 to obtain a processed raw paper and a paper molded container, and the measurement and evaluation were performed in the same manner.
[0045]
The measurement results and evaluation results of Examples and Comparative Examples are shown in Tables 1 and 2 above.
The evaluation method is as follows.
[0046]
[Density of each paper layer]
The peel strength test method of the paperboard making layer of JIS P 8139 The interlayer was peeled by the delamination method described, and the thickness (mm), basis weight (g / m²)
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 layer thickness before peeling / total value of each layer thickness after peeling
When peeling of each layer is difficult by the delamination method described in the above-mentioned JIS P 8139 paperboard sheet-peeling layer peel strength test method, the multilayer-fabricated sheet sample is impregnated in warm water at 60 ° C. for 1 hour. To separate the surface layer, middle layer and back layer. Each layer peeled off was dried to obtain thickness (mm) and basis weight (g / m²) Thereafter, the correction factor value is similarly calculated to correct the thickness of each peeled layer, and the density of each layer is calculated.
[0047]
[Oxygen permeability]
Measured under conditions of 23 ° C. 50% RH and 23 ° C. 100% RH with the coated surface facing the oxygen detector side by JIS-K-7126 B method (isobaric method) (oxygen permeability measuring device: OX-TRAN100 type, MOCON company) Made). For the oxygen permeability, the value after 48 hours after setting the sample was defined as the oxygen permeability. The sample to be measured was sampled from the bottom of the paper molding container.
[0048]
[Table 1]

[0049]
[Table 2]

[0050]
【The invention's effect】
  According to the present invention, a paper molded container having water resistance, biodegradability, excellent press molding suitability, beautiful appearance, sufficient strength, and gas barrier properties can be obtained.For press formingFormed base paper, And paper molded containersIt became possible to get.
[0051]
[Brief description of the drawings]
FIG. 1 is a plan view of a blank sheet of a paper molding container.
FIG. 2 is a perspective view of a press-molded paper container.
[Explanation of symbols]
1: Ruled line

Claims (5)

Density exceeds 0.3 g / cm ³ and 0. 6 g / cm ³ less to have a low density layer and 0.7 g / cm ³ or more dense layers, the overall density of 0.4 to 0.7 g / cm ^3, a basis weight of 90~500g / ^{m 2} A press-molding base paper, wherein a gas barrier layer is laminated on at least one side of the multilayer paper.   2. The molded base paper according to claim 1, wherein the low density layer is mainly composed of a pulp selected from at least one of mechanical pulp, curled fiber, and mercerized pulp.   The molded base paper according to claim 1, wherein the gas barrier layer is formed of a thermoplastic resin.   The forming processed base paper according to claim 1, wherein the gas barrier layer contains an ethylene vinyl alcohol resin.   A paper-molded container, wherein the forming-processed base paper according to claim 1 is formed by press molding.

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