JP2008087765A - Heat insulating paper-made container, and raw material sheet used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper-made container which is easily molded, capable of obtaining sufficient foaming property, and superior in heat insulation. <P>SOLUTION: In a raw material sheet to be used for the paper-made container, a thermoplastic resin layer is formed at least on one side of a base paper material in a raw material sheet to be used for a heat insulating paper-made container. The basic weight of the base paper material is ≥250 g/m<SP>2</SP>, the maceration freeness is ≤360 ml in terms of Canadian Standard Freeness. The thermoplastic resin layer is foamed by heating and evaporating water contained in the base paper material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a paper container requiring heat insulation and a raw material sheet for the container. More specifically, a cup for filling hot coffee or the like used in vending machines, a so-called instant food container that makes it possible to eat and drink the contents by injecting hot water, and a microwave oven The present invention relates to a disposable container having heat insulation used for a cooking container or the like.

Insulated containers are generally used when fast drinks such as coffee or soup are provided to buyers in fast food stores such as hamburger shops, trains, vending machines, and instant ramen in cups. .
Conventionally, as a container used for such a use, what has the heat insulation property made from expanded polystyrene (EPS) is known. This is manufactured by adding a foaming agent to polystyrene, then casting this material into a mold, then applying heat and pressure to foam the raw material, and removing the molding container from the mold. The heat insulating container thus obtained is very excellent in terms of heat insulating properties. However, this container is bulky because the entire plastic is foamed, and the amount of dust increases. And, when incinerated as garbage after use, the incinerator is easily damaged because it emits high heat and it is required to be reviewed from the viewpoint of saving petroleum resources. In addition, there are concerns about adverse effects on the human body as environmental hormones. Furthermore, since the outer surface of expanded polystyrene has many minute irregularities, even if patterns, letters, symbols, etc. are printed on the outer surface, they are not clearly expressed. In addition, the thickness of the container is weaker than that of a paper cup, and in the case of a relatively large container such as instant noodles, the container may be broken during transportation.

On the other hand, in addition to the above-mentioned foamed plastic container, for example, Patent Document 1 (Japanese Patent Laid-Open No. 57-110439) discloses a paper container composed of a container body member and a bottom plate member on the outer wall surface of the container body member. A technique is described in which a low-melting thermoplastic synthetic resin film is laminated and heated to foam the film into irregularities using the vapor pressure of moisture contained in the paper that is the base material. At this time, it is described that the other surface of the paper is laminated with a thermoplastic synthetic resin film that becomes a similar foamed layer or coated with an aluminum foil as a layer for maintaining the vapor pressure during heating. This container has a comparatively good heat insulating property, and has advantages such as being inexpensive and easy to manufacture.
Similarly, as a technique for foaming by heating and evaporation of moisture contained in paper, Patent Document 2 (Patent No. 3596681) discloses a thermoplastic resin having a low melting point on one wall surface of the body member from the surface side of the paper. And a non-foamed outer layer of a thermoplastic resin having a higher melting point than that of the inner layer of the foamed inner layer. The interlayer strength between the foamed inner layer and the paper, the basis weight of the paper, the foamed layer and A paper container that defines the thickness of the non-foamed outer layer is described. Patent Document 2 also describes laminating a thermoplastic resin having a high melting point as a layer for maintaining the vapor pressure during heating on the other side of the paper.
Patent Document 3 describes a paper container having an upper flange portion at the upper edge of the opening of the container body member. By forcibly processing the flange portion into a square cross section, the flange portion does not foam, and the mouth feels. Is described as improving. Furthermore, it describes that the strength is increased by superposing the inner winding end of the flange part on the upper part of the flange part to form a double structure.

JP-A-57-110439 Japanese Patent No. 3596681 JP 2001-354226 A

The container described in Patent Document 1 or 2 uses paper as a base material, and the laminate layer (resin layer) is made of petroleum as a raw material, but its thickness is suppressed to the minimum necessary for heat insulation. For this reason, the use of fossil fuels is reduced as much as possible, and the environmental load is small compared with a container made entirely of expanded polystyrene, and the printability is excellent.
However, since the moisture contained in the paper substrate is evaporated by heating and the thermoplastic resin layer is foamed by the evaporated moisture to provide heat insulation, if the moisture in the paper is low, foaming is not possible. If it becomes sufficient and does not foam sufficiently, high heat insulation cannot be obtained. And since paper with a low basis weight has a low water content and is inferior in foaming properties, a paper substrate with a high basis weight must be used.
On the other hand, the paper container is formed into a cup shape from the body member and the bottom plate member, and in particular, the upper edge of the opening of the container body member is an upper portion as in Patent Document 3 for giving mouthfeel and strength when eating and drinking. Although a flange portion is provided, when paper having a high basis weight is used, it is difficult to perform the molding process, and the entire cost is increased. Furthermore, if the container is lightweight, it is advantageous from the viewpoint of transportation and recycling, and it is desirable that the basis weight of the paper be low.
Therefore, an object of the present invention is to provide a paper container that has sufficient foaming properties and excellent heat insulation properties without increasing the basis weight of the paper.

(1) In the raw material sheet used for the insulating paper container,
A raw material sheet in which a thermoplastic resin layer is formed on at least one side of a paper substrate,
The basis weight of the paper substrate is 250 g / m ² or more and the disaggregation freeness is a Canadian standard freeness of 360 ml or less,
A raw material sheet, wherein the thermoplastic resin layer is foamed by heating and evaporation of moisture contained in a paper substrate.
(2) In a heat insulating paper container composed of a trunk member and a bottom plate member,
The body member and / or the bottom plate member is a heat insulating paper container using a paper material provided with a thermoplastic resin foam layer on at least one side of a paper substrate,
The basis weight of the paper base material is 250 g / m ² or more and the disaggregation freeness is a Canadian standard freeness of 360 ml or less,
2. A heat insulating paper container, wherein the thermoplastic resin foam layer is a foamed layer formed by heating and evaporating moisture contained in a paper base material.
(3) The raw material sheet or heat insulating paper, wherein the paper base material described in (1) or (2) contains NBKP and LBKP as pulp and has an NBKP / LBKP ratio of 30/70 or less. Made container.
(4) The paper substrate density of 0.91 g / cm ³ or less, and wherein the at 0.6 g / cm ³ or more (1) to (3) Raw materials sheet or thermal insulation according to any one of Paper container.
(5) The raw material sheet or heat insulating paper container described in any one of (1) to (4), wherein the paper base has a paper surface PH of 6 or less.
(6) The raw material sheet or heat insulation described in any one of (1) to (5), wherein the paper base material contains polyvinyl alcohol or starch, and the coating amount is 2 g / m ² or less. Sex paper container.
(7) The foamed layer made of a thermoplastic resin has a layer thickness of 1200 μm or more, and is a raw material sheet or a heat insulating paper container described in any one of (1) to (6).
(8) The thermoplastic resin foam layer is formed by multiplying the thermoplastic resin layer before foaming by 15 to 25 times, and is described in any one of (1) to (7), Raw material sheet or insulated paper container.

-A foam container having good foamability and sufficient foam layer thickness can be obtained, and a paper container excellent in heat insulation can be provided.
・ Even if low-basis weight paper is used, the same heat insulation effect as when high-basis weight paper is used can be imparted, so that resource saving and cost reduction are possible.
A container mainly composed of paper that does not use expanded polystyrene, is an environmentally friendly container, and has little influence on the human body, and can be treated as paper-based waste.

Hereinafter, although the paper container of this invention is demonstrated based on drawing, this invention is not limited to these.
FIG. 1 is a cross-sectional view of an example of a paper container according to the present invention. The paper container 1 of the present invention is basically composed of a body member 2 and a bottom plate member 3.
FIG. 2 is a partially enlarged cross-sectional perspective view of the body portion indicated by Y in FIG. In this example, a thermoplastic resin foam layer, that is, a foamed thermoplastic resin layer 5 (hereinafter referred to as a foamed thermoplastic resin layer 5) is present on the surface of the paper substrate 4 on the outer wall surface side (outside of the container) of the body member. The foamed thermoplastic resin layer 5 has a structure in which foamed cells 6 are arranged. A thermoplastic resin layer 7 made of a thermoplastic resin having a melting point higher than that of the thermoplastic resin of the foamed thermoplastic resin layer 5 (hereinafter referred to as a non-foamed thermoplastic resin layer 7) is provided on the inner wall surface side (inner side of the container) of the trunk portion. Is present. As will be described later, the non-foamed thermoplastic resin layer 7 does not foam during the heat treatment in the container production, prevents the escape of evaporated water from the paper base material, and makes the foamed thermoplastic resin layer 5 reliable and sufficient. It is made to foam.

[Paper base]
(paper)
The paper used in the present invention refers to a paper fiber or a paper fiber that is produced by intertwining vegetable fibers and other fibers and is produced by a method known in the papermaking field. Examples of plant fibers include, but are not limited to, wood fibers such as conifers or hardwoods, bast fibers such as Mitsumata and Kozo, non-wood fibers such as bagasse, kenaf and hemp, cotton fibers, and waste paper. From the viewpoint of waste disposal and environmental load against the background of global environmental problems, paper composed of 100% plant fiber is preferred.
Specific examples of wood fiber pulp include chemical pulp using conifers and hardwoods; bleached kraft pulp of conifers (NBKP), unbleached kraft pulp (NUKP), bleached kraft pulp of hardwood (LBKP), unbleached kraft Pulp (LUKP) and the like, mechanical pulp; groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), deinked pulp (DIP) and the like, These may be used alone or in admixture at any ratio. The deinked pulp is also called regenerated pulp. In the present invention, among them, softwood bleached kraft pulp (hereinafter referred to as NBKP) or hardwood bleached kraft pulp (hereinafter referred to as LBKP) is preferable in terms of moisture content and versatility.

  As a method for producing paper, generally, the above pulp, water, and paper material prepared by adding fillers and other chemicals as needed are sprayed onto the wire of the paper machine, and dewatered at the wire part. Squeezed in the press part, dried in the dryer part, and if necessary, made paper by applying a size press that gives the paper strength and water resistance, and a calendar that adjusts the unevenness of the paper surface, and then winding the finished paper Finished to a predetermined winding dimension and completed. The production of paper in the present invention is not limited to this.

(Basis weight)
In the present invention, the basis weight of the paper is important because it is a mechanism in which the thermoplastic resin layer is foamed using the heat-evaporated moisture in the paper, and the basis weight affects the amount of moisture contained. When the basis weight is too low, foaming does not occur sufficiently because of the small amount of water necessary for foaming, and it is easy to feel heat when the container is held by hand. If the basis weight is too high, the amount of water increases and foams more than necessary, leading to over-foaming and rupture of the foamed cells, etc. The workability is lowered and it is difficult to form the upper flange portion.

In the present invention, the basis weight is preferably 100 g / m ² or more and 400 g / m ² or less, preferably 200 g / m ² or more, more preferably 250 g / m ² or more, and even more preferably 270 g / m ² or more. is there. The water content in the paper is preferably 5 to 15% by weight, more preferably 6 to 10% by weight. An appropriate amount of water is about ²⁰ to 32 g / m ² .

(Determination freeness)
In the present invention, paying attention to the degree of freezing and freezing of paper, when the degree of freezing and freezing is 360 ml or less, excellent foamability can be obtained without increasing the basis weight of the paper. It has been found that the basis weight can be lowered without damage. The reason why excellent foamability can be obtained when the disaggregation freeness is 360 ml or less is not clear, but is considered as follows. In the manufacture of paper, pulp is beaten and loosened (beating), but this beating process causes whiskers to come out and soften from the pulp fibers, entanglement of fibers and interfiber bonding are promoted, and the strength of the paper is increased. Rise. The degree of beating is measured by freeness, and the principle is to put a certain amount of pulp and water on a net and check the amount of water falling from the net. The more advanced the beating, the smaller the value and the higher the strength of the paper, but the strength of the fiber itself is reduced, although the adhesion between the fibers increases, but the tensile strength and tear strength are reduced. End up. On the other hand, in the present invention, since the disintegration freezing degree is paper of 360 ml or less, the fiber cell wall is damaged so as to easily release the internal moisture, and thus a significantly excellent foaming property is obtained. Conceivable. When it exceeds 360 ml, foaming is insufficient and high heat insulation cannot be obtained. More preferably, it is 344 ml or less, More preferably, it is 320 ml or less. However, in the case of paper with low disaggregation freeness, there is a problem such as high density and no bulk, opacity decreases, fiber damage is severe and paper strength is remarkably reduced, and it is necessary as a container. Since it is difficult to obtain thickness and rigidity, the lower limit of the disaggregation freeness is preferably 150 ml or more.

The disaggregation freeness in the present invention is represented by the Canadian standard freeness (hereinafter sometimes referred to as CSF) based on JIS-P-8121 when paper is disaggregated again in water. For the measurement of the degree of water removal, the foamed body of the paper container is immersed in water for several days to remove and remove the thermoplastic resin layer, and then left to stand for a whole day and night in a predetermined size soaked in water. Then, it disaggregates to such an extent that a binding fiber is not seen, it cools, and it carries out according to JIS-P-8121.
Further, the freeness at the pulp stage is preferably about 470 ml or less because the paper having a disaggregation freeness of 360 ml or less is easily obtained. The lower limit is 200 ml or more. If the CSF of the pulp is too low, the dewaterability will deteriorate during paper making, it will become a tight paper, a paper with low density and bulk will not be obtained, a paper with high opacity will not be obtained, and a paper with high tear strength will be obtained There are problems such as inability. Further, in the present invention, different types of pulp may be used in combination, and the CSF in that case is not pulverized but mixed to be 470 ml or less. When using a pulp together, it is preferable to use NBKP and LBKP, and it is preferable that the ratio of NBKP is less than 50 weight% with respect to the total pulp weight, Furthermore, it is preferable that it is 30 weight% or less. Normally, NBKP tends to increase the CSF, and the foaming property tends to decrease when the blending ratio of NBKP increases. Since NBKP is mixed in order to increase the tear strength, it is preferable that the NBKP is not hit too much.

(density)
In the present invention, it is preferable that the density is low because it is considered that evaporative moisture easily passes and foamability is improved. However, if it is too low, the paper strength required for the container cannot be obtained, and the thermoplastic resin layer, which will be described later, is inferior in laminating properties. If it is too high, the necessary thickness for the container cannot be obtained, so 0.91 g / cm ³ Hereinafter, 0.6 g / cm ³ or more is preferable. However, the density of the paper may be appropriately set as desired, and is not particularly limited to this range.

(Paper PH)
The paper surface PH is desirably 6 or less. On the alkaline side of the paper PH, the fibers are likely to retain water, whereas on the acidic side, moisture is likely to be released and foamability is considered to be good. However, the type of paper is not limited to this, and the types of paper are acidic paper in which papermaking PH is made in an acidic region, pseudo-neutral paper in which papermaking PH is made in a pseudo-neutral region, and papermaking PH is in a neutral region. Neutral papers made in step (1) and alkaline papers made from paper PH in the alkaline region may be used, and neutral papers coated with an alkaline agent on the surface of the acidic base paper made in the acidic region are also possible.

(Fillers, other chemicals, etc.)
In the paper used in the present invention, the filler may be blended without blending, and blending is desirable because it affects foaming properties, but it may be blended from the viewpoint of increasing opacity. When the filler is blended, the filler generally used in the papermaking field can be used and is not particularly limited. For example, clay, calcined kaolin, deramikaolin, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica composite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide Inorganic fillers such as calcium hydroxide, magnesium hydroxide, and zinc hydroxide, and organic fillers such as urea-formalin resin, polystyrene resin, phenol resin, and fine hollow particles may be used alone or in appropriate combination of two or more. Further, in acidic papermaking, a filler obtained by removing acid-soluble ones from the filler used in the neutral papermaking is used, and these are used alone or in combination of two or more as appropriate.
Various internal sizing agents may be blended, and various types of conventionally used nonionic, cationic or amphoteric yield improvers, freeness improvers, paper strength improvers, etc. An auxiliary agent is appropriately selected and used as necessary. Further, for example, basic aluminum compounds such as sulfuric acid band, aluminum chloride, sodium aluminate, basic aluminum chloride and basic polyaluminum hydroxide, water-soluble aluminum compounds such as water-degradable alumina sol, sulfuric acid A polyvalent metal compound such as ferrous sulfate or ferric sulfate, silica sol, or the like may be internally added.

Other papermaking aids such as various starches, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide, polyamine resin, polyamine, polyethyleneimine, vegetable gum, polyvinyl alcohol, latex, polyethylene oxide, hydrophilic crosslinking Various compounds such as polymer particle dispersion and derivatives or modified products thereof can be used.
Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents, and the like can be appropriately added depending on the application.

(Paper making)
There are no particular restrictions on the type of paper machine, and paper machines can be used on public paper machines such as long paper machines, twin-wire paper machines, circular net paper machines, gap formers, and hybrid formers (on-top formers). it can. The press line pressure is used within the normal operating range. Further, for the purpose of imparting smoothness and improving printability, a calendar process may be performed. The calender is used at a linear pressure within the normal operating range. However, in the present invention, it is more desirable that the paper is easy to evaporate moisture, and the paper is more bulky. In that case, it is as low as possible within the range where the smoothness of the paper can be maintained. Linear pressure or bypass is preferred. A soft calendar is preferable to a normal calendar.
The paper used in the present invention may not be coated at all or may be coated with a surface treatment agent containing no pigment. Moreover, you may apply the surface treating agent which has a water-soluble polymer as a main component in order to improve surface strength or size property. As the water-soluble polymer, those usually used as a surface treating agent such as starch, oxidized starch, processed starch, carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol, etc. can be used alone or a mixture thereof. In addition to the water-soluble polymer, a paper strength enhancer for the purpose of water resistance and surface strength improvement and an external sizing agent for the purpose of imparting sizing can be added to the surface treatment agent. As a method for applying the surface treatment agent, the surface treatment agent can be applied by a coating machine such as a two-roll size press coater, a gate roll coater, a blade metalling coater, or a rod metalling coater. It is preferable to use such a coat transfer type coating machine because the surface treatment agent remains on the paper surface and the increase in density is reduced. The coating amount of the surface treatment agent is about 0.1 g / m ² or more and 3 g / m ² or less per side.

(Size press)
In the present invention, it is also preferable to coat a surface treatment agent such as polyvinyl alcohol or starch, an external sizing agent, or the like during the calendar treatment. Such a method is called a size press and includes a two-roll size press, a film transfer size press, a calendar sizing, and the like. A normal calendar process may be performed after the size press. The application of the surface treatment agent by the size press is highly effective in improving the surface strength and preventing the generation of paper dust. In addition, it is usually difficult to dry the paper machine in the drying process in the center of the paper machine in the width direction, and it is difficult to obtain a uniform moisture profile. As a result, it is possible to obtain a uniform foamed thermoplastic resin layer without unevenness in heating and evaporation. Although water may be used without containing a surface treatment agent, polyvinyl alcohol, starch, and the like are preferable because they have an appropriate viscosity and thus are easier to spread than water, and the effect of water uniformity is increased. In this case, the coating amount of polyvinyl alcohol, starch and the like tends to hinder the evaporation of water even if it is too much, so that it is 2 g / m ² or less, more preferably 0.9 g / m ² or less, still more preferably 0.8. 5 g / m ² or less.

[Foamed thermoplastic resin layer]
The body member raw material sheet of the paper container of the present invention is produced by laminating a thermoplastic resin layer foamed by heating and evaporation of moisture contained in the paper on the paper base material.
The thermoplastic resin used as the foamed thermoplastic resin layer is not particularly limited as long as extrusion lamination is possible and foaming is possible, and either a crystalline resin or an amorphous resin can be used. Examples of the crystalline resin include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene, polyester resins, polyamide, polyacetal, and PPS resins. Examples of the amorphous resin include polystyrene, polyvinyl chloride, ABS resin, acrylic resin, modified PPE, polycarbonate, polyurethane, polyvinyl acetate, and amorphous polyethylene terephthalate (PET). The melting point of these thermoplastic resins is preferably about 80 to 120 ° C. These thermoplastic resins may be a single resin or a plurality of resins, but are preferably a single layer from the viewpoint of foamability.

Furthermore, in the present invention, polyethylene is preferred because of excellent laminating ability and foamability. Polyethylene is roughly classified into linear low density polyethylene, low density polyethylene, medium density polyethylene, and high density polyethylene. The density, linear low density polyethylene 888~910kg / ^{m 3,} low density polyethylene 910~925kg / ^{m 3,} medium density polyethylene 925~940kg / ^{m 3,} higher density polyethylene has 940~970kg / m ^{About three} . As the melting point, linear low density polyethylene is 55 ° C to 120 ° C, low density polyethylene is 105 ° C to 120 ° C, medium density polyethylene is 120 ° C to 125 ° C, and high density polyethylene is about 125 ° C to 135 ° C.

[Non-foamed thermoplastic resin layer]
In the present invention, in order to increase the foaming efficiency, the opposite wall surface side of the wall surface having the foamed thermoplastic resin layer of the body member is made of a thermoplastic resin having a melting point higher than that of the foamed thermoplastic resin layer and foamed when heat-treated. It is preferable to cover with an unheated thermoplastic resin layer (non-foamed thermoplastic resin layer) or an aluminum foil. If one side of the paper base is left ground, the moisture in the paper will evaporate from the uncoated surface into the atmosphere during the heat treatment, making it difficult to ensure sufficient foaming. Therefore, by providing such a coating layer, moisture in the paper can be efficiently contributed to foaming. It should be noted that these non-foamed thermoplastic resin layers, aluminum foils, and the like are preferably present on the inner wall surface side of the body member, so that the filling liquid or the like can be prevented from penetrating into the paper.
Similarly, a non-foamed thermoplastic resin layer can be provided on the foamed thermoplastic resin layer for the purpose of increasing the foaming efficiency. When the foamed thermoplastic resin layer is present on the outer wall surface of the body member, the surface is uneven and not smooth, so that the presence of the non-foamed thermoplastic resin layer provides a smooth hand and glossy appearance. And the waterproofness of the container is further improved.

  The thermoplastic resin of these non-foamed thermoplastic resin layers may be the same as or different from the foamed thermoplastic resin layer. In the case of the same, a difference in the melting point can be caused by making a difference in density. For example, when polyethylene is selected as both thermoplastic resins, the foamed thermoplastic resin layer is low density polyethylene and the non-foamed thermoplastic resin layer is medium density or high density polyethylene. The difference between the melting points of the thermoplastic resin of the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer is preferably 5 ° C. or more. The melting point of the thermoplastic resin of the non-foamed thermoplastic resin layer is the melting point during heating. There is no particular limitation as long as it can prevent the diffusion of evaporated water, but 125 ° C. or higher is preferable.

[Lamination method of thermoplastic resin layer]
The method for forming the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer is not particularly limited, and it is pasted on a paper substrate with a film-like material such as a wet laminate method or a dry laminate method in addition to an extrusion laminate method. The lamination method may be appropriately used for lamination, but the extrusion laminating method is preferable from the viewpoints of adhesion to a paper base material, foamability and the like. For example, extrusion lamination is performed by extruding a thermoplastic resin layer from a T-die in the form of a molten resin film onto one surface of a paper substrate that has been unwound from winding, and cooling between a cooling roll and a nip roll facing it. It is a method of crimping while. In extrusion lamination, the operating conditions such as the melting temperature of the resin and the laminating speed may be appropriately set depending on the type of resin used and the apparatus, but generally the melting temperature is about 200 to 350 ° C. and the laminating speed is 50, for example. It is about ~ 200 m / min. Further, it is preferable to use a nip roll having a hardness of 70 degrees or more (JIS K-6253) and pressing and pressure bonding with a linear pressure of 15 kgf / cm or more.
When laminating two or more thermoplastic resin layers, such as when a non-foamed thermoplastic resin layer is provided on the foamed thermoplastic resin layer, or when the foamed thermoplastic resin layer is formed of a plurality of thermoplastic resin layers, etc. From the viewpoint of adhesion between thermoplastic resin layers and production efficiency, there is a method in which each thermoplastic resin is led to each T die in a molten state using a plurality of extruders, and is extruded from each T die at the same time and laminated and adhered. Is suitable. Such a method capable of simultaneously forming a multilayer thermoplastic resin layer is called a coextrusion laminating method among the extrusion laminating methods. Further, an adhesive resin layer may be sandwiched between the thermoplastic resin layers to improve the adhesion between the resin layers. In any case, corona treatment, ozone treatment, or the like may be performed in order to improve the adhesion of the paper base material or the thermoplastic resin as necessary.

Further, regarding the thickness of each of the thermoplastic resin layers of the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer, the foamed thermoplastic resin layer has a thickness sufficient to impart desired heat insulation properties when foamed. However, the thickness before foaming is about 40 to 80 μm, and after foaming, for example, in the case of the thermoplastic resin layer before foaming having a thickness of 70 μm, it is about 1200 μm to 2000 μm. In the present invention, a foamed layer having a thickness of 1200 to 1600 μm is formed from a thermoplastic resin layer having a thickness of 70 μm before foaming. In the prior art, an example in which a thin layer such as a 20 μm layer is foamed about 10 times is disclosed, but the thermal insulation is not sufficient at that level, but if the thermoplastic resin layer becomes thick, foam control becomes difficult. Therefore, a 1000 μm foam layer is not realized in the conventional known example.
Further, the non-foamed thermoplastic resin layer is also thick enough to prevent scattering of evaporated water, and if it is on the inner wall surface side of the body member, the thickness can ensure liquid penetration resistance. It is not specifically limited, It is about 20-50 micrometers.

Further, the outer wall surface side and the inner wall surface side of the body member and the bottom member of the container may have the same laminated structure or may be different. The type of resin used and other materials may be the same or different.
In addition, various commonly used additives can be added to the thermoplastic resin layers of the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer as long as the desired effects are not impaired. Examples of these additives include antistatic agents, white pigments (inorganic pigments such as titanium oxide, calcium carbonate, clay, talc, and silica), anti-blocking agents (acrylic beads, glass beads, silica, etc.), and ultraviolet absorption. There are agents.

[Molding paper containers]
In the present invention, the body member raw material sheet and the bottom plate member raw material sheet are molded by a conventional cup manufacturing apparatus or cup molding machine. First, the body member raw material sheet is fed out from the take-up roll, and necessary printing is performed at a predetermined location. At this stage, barcodes can be printed. The positioning of the printed part can be performed by conventional means or procedures.

Next, a blank for a trunk member and a blank for a bottom plate member are punched out from each raw material sheet, and assembled into a container shape by a conventional cup molding machine. Here, the foamed thermoplastic resin layer only needs to be present on one or both of the outer wall surface side and the inner wall surface side of the body member, and may be appropriately determined as desired, such as heat insulation, touch, and appearance aesthetics. However, when the inside of the container is a foamed surface, the foamed resin may be damaged by chopsticks, forks or the like during food and drink and enter the mouth, so it is desirable that the container be on the outer wall surface side. Therefore, for example, the body member raw material sheet is assembled so that the thermoplastic resin layer faces the outside of the container, and the bottom plate member is assembled so that the surface of the thermoplastic resin layer faces the inside of the container. In addition, the bottom plate member raw material sheet is preferably used in which one or more thermoplastic resin layers, aluminum stays or the like are provided on at least one side of the paper base material. This is to prevent penetration of liquid or the like into the paper. The thermoplastic resin used for the bottom plate member may be the same as or different from that of the body member, and the lamination method is not only the extrusion lamination method but also a pre-film-like one such as a wet lamination method or a dry lamination method. The method to combine can be used suitably.
In order to prevent heat dissipation from the bottom of the container, it is effective to provide a foam layer on the bottom member of the cup noodles that are allowed to stand for a while after pouring hot water. In particular, it is preferable for outdoor use, winter and cold regions. Moreover, you may use the thing which has a foamed layer similarly.

[Foaming by heat treatment]
The molded paper container is subjected to heat treatment in order to make it foam. In the present invention, due to the heat treatment, moisture contained in the paper base material of the body member evaporates, and the thermoplastic resin layer foams to become a foamed thermoplastic resin layer.
The heating temperature and heat time vary depending on the type of paper substrate and thermoplastic resin to be used, and the optimum combination of heating temperature and heating time for the thermoplastic resin to be used can be appropriately determined. A temperature slightly higher than the melting point of the foamed thermoplastic resin (melting point +5 to 10 ° C.) is suitable. Generally, the heating temperature is about 110 ° C. to about 200 ° C., and the heating time is about 1 minute to about 6 minutes. is there. The heating means is not particularly limited, and any means such as hot air, electric heat, or electron beam can be used. If it is heated by hot air or electric heat in a tunnel equipped with a conveyor means, mass production can be performed at low cost.

[Others]
In the present invention, a technique known in the field of paper containers can be applied as necessary within a range that does not impair the desired effect. For example, a technique for applying a paint containing 5 wt% to 40 wt% of a synthetic resin component on a part of a body member serving as an outer wall surface to partially suppress foaming (Japanese Patent No. 3014629), a body member serving as an outer wall surface A technique for applying a synchronized ink that forms a smooth printing surface in synchronization with foaming on the surface of the container (Japanese Patent No. 3408156), and a technique for providing a flange portion at the upper edge of the opening of the container body member, A technique (for example, Japanese Patent Application Laid-Open No. 2001-354226) and the like in which a forcible processing is performed and the inner winding end is superposed on the upper portion of the flange portion to form a double structure may be mentioned, but is not limited thereto. Moreover, in order to improve printability, you may provide the ink receiving layer which has a pigment and a binder as a main component in the outermost layer used as the outer wall surface of a trunk | drum member.

Hereinafter, the effects of the present invention will be described in detail by way of examples. Unless otherwise specified, parts and% indicate parts by weight and% by weight.
[Base paper production example 1]
10 parts of softwood bleached kraft pulp (NBKP; freeness CSF 600 ml) and 90 parts of hardwood bleached kraft pulp (LBKP; freeness CSF 400 ml) are mixed, and after mixing the pulp raw material having a freeness of CSF 420 ml is used as an internal chemical. Raw material with 2.5% by weight sulfate band, 0.5% by weight rosin sizing agent, 0.2% by weight oil acrylamide as a paper strength agent, and PH of 4.5 per solid dry weight of pulp. Was made into a single layer at a papermaking speed of 40 m / min using a long paper machine to produce a web of paper having a basis weight of 300 g / m ² and a paper thickness of 341 μm.
Next, the obtained paper web was coated with 0.4 g / m ² (absolute dry coating amount) of polyvinyl alcohol (solid content concentration 1.5%) by calendar sizing (linear pressure 30 kgf / cm), and infrared rays were applied. After drying with a dryer, calendar treatment was performed at a linear pressure of 30 kgf / cm to obtain a base paper A having a moisture content of 8.2%.

[Base paper production example 2]
A base paper B was obtained in the same manner as the base paper production example 1 except that the basis weight was changed to 270 g / m ² .

[Base paper production example 3]
A base paper C was obtained in the same manner as in the base paper production example 1 except that the basis weight was changed to 380 g / m ² .

[Base Paper Production Example 4]
A base paper production example 1 except that 5 parts of softwood bleached kraft pulp and 95 parts of hardwood bleached kraft pulp were mixed and beaten, and a pulp raw material having a freeness of CSF of 410 ml after mixing was used and the calender linear pressure was 20 kgf / cm. Base paper D was obtained in the same manner.

[Base Paper Production Example 5]
Base paper E was obtained in the same manner as in base paper production example 1 except that the freeness of hardwood bleached kraft pulp was CSF 450 ml, and the calender linear pressure was 50 kgf / cm.

[Stencil paper production example 6]
A base paper F was obtained in the same manner as in the base paper production example 1 except that the freeness of hardwood bleached kraft pulp was changed to CSF 430 ml.

[Base paper production example 7]
Base paper G was obtained in the same manner as in base paper production example 1 except that the freeness of hardwood bleached kraft pulp was changed to 410 ml of CSF.

[Base paper production example 8]
A base paper H was obtained in the same manner as in base paper production example 1 except that the freeness of hardwood bleached kraft pulp was changed to 300 ml of CSF.

[Base paper production example 9]
25 parts of softwood bleached kraft pulp (NBKP; freezing degree CSF 600 ml) and 75 parts of hardwood bleached kraft pulp (LBKP; freezing degree CSF 400 ml) were mixed, and a pulp material having a freeness of CSF of 450 ml after mixing was used. Base paper I was obtained in the same manner as in Base Paper Production Example 1.

[Base Paper Production Example 10]
Base paper J was obtained in the same manner as in base paper production example 1 except that 100 parts of pulp material of hardwood bleached kraft pulp (LBKP; freeness CSF 400 ml) was used.

[Base Paper Production Example 11]
A base paper K was obtained in the same manner as in the base paper production example 1 except that the calender linear pressure was 70 kgf / cm.

[Base Paper Production Example 12]
A base paper L was obtained in the same manner as in base paper production example 1 except that the calender sizing linear pressure was 20 kgf / cm and no calendering was performed.

[Base Paper Production Example 13]
A base paper M was obtained in the same manner as in the base paper production example 1 except that the solid content was set to 0.9% by weight of the sulfuric acid band per solid dry weight of the pulp as an internal additive.

[Base Paper Production Example 14]
A base paper N was obtained in the same manner as in base paper production example 1 except that no sulfuric acid band was added as an internal additive.

[Base Paper Production Example 15]
A base paper O was obtained in the same manner as in the base paper production example 1 except that no external addition was performed by calendar sizing.

[Base Paper Production Example 16]
Base paper P was obtained in the same manner as in Base Paper Production Example 1 except that 0.9 g / m ² (absolute dry coating amount) of polyvinyl alcohol (solid concentration 2.0%) was applied by calendar sizing.

[Base Paper Production Example 17]
Base paper Q was obtained in the same manner as in base paper production example 1 except that the oxidized starch (solid content concentration: 3.0%) was applied at 0.9 g / m ² (absolute dry coating amount) by calendar sizing.

[Base Paper Production Example 18]
A base paper R was obtained in the same manner as in base paper production example 1 except that polyvinyl alcohol (solid content concentration: 0.3%) was applied at 0.9 g / m ² (absolute dry coating amount) with a two-roll size press. It was.

[Base Paper Production Example 19]
A base paper S was obtained in the same manner as the base paper production example 1 except that the basis weight was 230 g / m ² .

[Base Paper Production Example 20]
A base paper T was obtained in the same manner as in the base paper production example 1 except that the freeness of hardwood bleached kraft pulp was CSF 500 ml and the calendar linear pressure was 70 kgf / cm.

[Base Paper Production Example 21]
Mix 50 parts of softwood bleached kraft pulp (NBKP; freeness CSF 600 ml) and 50 parts of hardwood bleached kraft pulp (LBKP; freeness CSF 400 ml), use a pulp raw material with a freeness of CSF 500 ml after mixing, and calendar line A base paper U was obtained in the same manner as in the base paper production example 1 except that the pressure was 90 kgf / cm.

[Examples 1-18, Comparative Examples 1-3]
On one side of the base paper obtained above, a low density polyethylene (LDPE) having a melting point of 108 ° C. is formed at 340 ° C. so as to have a thickness of 70 μm as a foamed thermoplastic resin layer that becomes an outer wall surface of the body member when a paper container is used. The molten resin and the base paper were pressed and pressure-bonded at a linear pressure of 15 kgf / cm using a cooling roll and a nip roll having a hardness of 70 degrees. Further, on the opposite surface of the base paper, a non-foamed thermoplastic resin layer serving as the inner wall surface of the body member is melted at 320 ° C. so that a medium density polyethylene (medium density PE) having a melting point of 128 ° C. has a thickness of 40 μm. Was extruded and laminated to obtain a body member raw material sheet.
In addition, this body member raw material sheet is combined with a bottom plate member raw material sheet (a medium density polyethylene extruded on a base paper having a basis weight of 220 g / m ² and laminated so as to have a thickness of 40 μm), and has a diameter of 95 mm and a height of 115 mm. The container was molded and heated for 4 minutes with a dryer at 115 ° C. for foaming to obtain a paper container having heat insulation properties.

  The freeness of the pulp used in the above base paper production examples and the paper quality of the obtained base paper were evaluated as follows. Moreover, the following evaluation tests were performed using the body member raw material sheet obtained in the comparative example. Tables 1 and 2 show the results of the base paper production examples 1 to 18 as Examples 1 to 18 and the base paper production examples 19 to 21 as Comparative Examples 1 to 3, respectively.

<Evaluation of pulp and paper quality>
-Canadian Standard Freeness (CSF) JIS P 8121: 1995.
-Basis weight: According to JIS P 8124: 1998 (ISO 536: 1995).
-Thickness: According to JIS P 8118: 1998.
-Density: Calculated from measured values of thickness and basis weight.
-Paper surface PH: The base paper was peeled off at almost the center in the thickness direction, and the peeled surface was measured according to JAPPN TAPPI paper pulp test method No. 49-2.
-Moisture content: According to JIS P 8127.

<Decomposition freeness>
Immerse the body of the foamed paper container in water for at least 2 days, peel off and remove the thermoplastic resin layer, and then tear off the dry weight of 60 g by hand so that the size is 5 cm square. The total volume was made up to 2000 ml. Further, after being left in a state immersed in water for a whole day and night, it was disaggregated to such an extent that a binding fiber was not observed with a TAPPI disaggregator, cooled to 20 ° C., and CSF was measured according to JIS-P-8121.

<Foaming (foamed resin layer thickness)>
A part of the body member of the paper container after foaming was cut out, and the thickness of the foamed thermoplastic resin layer was measured.

The following can be said from the test results of the examples and comparative examples.
Focusing on Examples 1, 2, 3 and Comparative Example 1 regarding the basis weight of the base paper, it can be seen that if the basis weight is low, the foamability is low, and if the basis weight is large, the foamability is high. In these examples, since the density is the same, the basis weight is proportional to the paper thickness and the moisture content is the same, so this difference in basis weight is also a difference in moisture content. Considering these, when other elements are common, it can be said that the water content contributes to the thickness of the foamed layer. As a result of Example 2, when the basis weight was 270 g / m ² , the foamed resin layer thickness was 1200 μm.
Focusing on Examples 1, 5 to 8 and Comparative Example 2 regarding the disaggregation freeness (CSF), even if the basis weight and the water content are the same, foaming is good when the disaggregation freeness (CSF) is low. I understand that The disaggregation freeness is affected by the freeness of the raw pulp. In these examples, adjustment is made by the LBKP beating process. The disaggregation freeness (CSF) is suitably 360 ml or less. In this test example, the foamed layer thickness of 1210 μm can be realized in Example 5 where the disintegration freeness (CSF) is 344 ml.
Focusing on Examples 11 and 12, regarding density, it can be seen that Example 11 having a higher density has a smaller foam thickness than Example 12 having a lower density. In this embodiment, the density is changed by the calendar linear pressure. This density is presumed to affect the ease of evaporating vapor. When the density is 0.91 g / cm ³ with reference to each example, goodness is confirmed. In Example 10, the density is higher than that in Example 1, but the thickness of the foamed layer can be increased. This is considered to reflect the result of reducing the disaggregation freeness (CSF) by setting the blending of the pulp raw material to 100% LBKP. In addition, it has been confirmed that the lower limit is preferably 0.6 g / cm ^{3 in} view of securing the paper strength for containers and laminating properties of the thermoplastic resin layer as described above.
When focusing on Examples 1, 13, and 14, the paper surface PH is less foamable on the neutral side. Considering that the water content, density, basis weight, and the like are common, this is probably because moisture is easily held on paper on the neutral side and moisture is easily released on the acidic side.
Focusing on Examples 1 and 15 to 17 for external addition, Example 15 was slightly larger in thickness than the Example 1, but somewhat uneven by appearance observation. In Examples 16 and 17, the thickness of the foam layer is smaller than that of the example. From these results, it can be understood that when the external addition is increased, the tendency of foaming to be suppressed is grasped, and when there is no external addition, foaming unevenness occurs. With PVA and starch, good foamability is obtained at 0.9 g / m ² and 0.4 g / m ² .
Moreover, the raw material pulp was tested by using NBKP and LBKP, blending them with varying characteristics and beating degree. NBKP is preferably set to an upper limit of 50%, and is unsuitable for increasing the beating property, so it is preferable to keep it within 30%. In this example, the test is performed at a blending ratio of 0 to 25%.

It is sectional drawing of an example of the paper containers by this invention. It is the elements on larger scale of the trunk | drum shown by Y in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper container 2 Body member 3 Bottom plate member 4 Paper base material 5 Foamed thermoplastic resin layer 6 Foamed cell 7 Non-foamed thermoplastic resin layer

Claims (6)

In the raw material sheet used for heat insulating paper containers,
A raw material sheet in which a thermoplastic resin layer is formed on at least one side of a paper substrate,
The basis weight of the paper substrate is 250 g / m ² or more and the disaggregation freeness is a Canadian standard freeness of 360 ml or less,
A raw material sheet, wherein the thermoplastic resin layer is foamed by heating and evaporation of moisture contained in a paper substrate. In a heat insulating paper container composed of a trunk member and a bottom plate member,
The body member and / or the bottom plate member is a heat insulating paper container using a paper material provided with a thermoplastic resin foam layer on at least one side of a paper substrate,
The basis weight of the paper base material is 250 g / m ² or more and the disaggregation freeness is a Canadian standard freeness of 360 ml or less,
2. A heat insulating paper container, wherein the thermoplastic resin foam layer is a foamed layer formed by heating and evaporating moisture contained in a paper base material.   The paper base material described in claim 1 or 2 contains NBKP and LBKP as pulp, and the ratio of NBKP is less than 50% by weight with respect to the total pulp weight. container. The paper substrate density of 0.91 g / cm ³ or less, 0.6 g / cm ³ or more is to raw material sheet or heat-insulating paper container according to claim 1, characterized in that.   The raw material sheet or heat insulating paper container according to any one of claims 1 to 4, wherein the paper base has a paper surface PH of 6 or less. The raw material sheet or heat insulating paper container according to any one of claims 1 to 5, wherein the paper substrate contains polyvinyl alcohol or starch, and the coating amount is 2 g / m ² or less.