WO2008038750A1

WO2008038750A1 - Container made of paper and process for producing the same

Info

Publication number: WO2008038750A1
Application number: PCT/JP2007/068928
Authority: WO
Inventors: Kouichiro Hiroshige; Masaaki Fukunaga; Tamijiro Kaneyuki; Katsuyuki Ookubo; Sadao Hara
Original assignee: Nippon Paper Industries Co., Ltd.; Nippon Paper-Pak Co., Ltd.
Priority date: 2006-09-29
Filing date: 2007-09-28
Publication date: 2008-04-03
Also published as: JP5047668B2; JP2008105747A

Abstract

A container made of paper which is in an evenly foamed state and has excellent heat-insulating properties. The container made of paper comprises a barrel member and a bottom member, wherein the barrel member comprises a paper base and a foamed thermoplastic resin layer formed thereon. The foamed thermoplastic resin layer is one obtained by forming a thermoplastic resin layer on at least one side of the paper base by extrusion laminating under such conditions that the time required for the thermoplastic resin in a molten state extruded from a T-die to reach the paper base is 0.11-0.33 seconds and thermally evaporating the water contained in the paper base to thereby foam the thermoplastic resin layer.

Description

Specification

Paper container and manufacturing method thereof

Technical field

The present invention relates to a paper container that requires heat insulation and a raw material sheet for the container. More specifically, cups for filling hot coffee used in vending machines, etc., so-called instant food containers that make the fillings ready for consumption by pouring hot water, Relates to a disposable container with heat insulation used for a container for cooking by a microwave oven.

Background art

[0002] Insulations are generally used in fast food stores such as hamburger shops, in trains, vending machines, etc., where hot drinks such as soups are served to buyers, and instant ramen in cups, etc. Container is used.

Conventionally, as a container used for such an application, a container having a heat insulating property made of expanded polystyrene (EPS) is known. This is manufactured by adding a foaming agent to polystyrene, casting the material into a mold, then foaming the raw material by applying heat and pressure, 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 garbage increases. Also, when incinerated as waste after use, the incinerator is damaged because it generates high heat and burned out, and there is a need to review it from the viewpoint of saving oil resources. In addition, there are concerns about adverse effects on the human body as environmental hormones.Further, 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. However, the thickness of the container is weaker than that of a paper cup, and relatively large containers such as instant bowls may be broken during transportation.

[0003] On the other hand, in addition to the above-mentioned foamed plastic container, for example, Patent Document 1 (Japanese Unexamined Patent Publication No. 57-1 10439) discloses a paper container comprising a container body member and a bottom plate member. Laminate and heat a low-melting thermoplastic synthetic resin film on the outer wall surface Describes a technique for foaming a film into irregularities by utilizing the vapor pressure of moisture contained in paper as a base material. At this time, it is described that the other surface of the paper is laminated with a thermoplastic synthetic resin film which becomes a similar foamed layer as a layer for maintaining the vapor pressure during heating or is coated with an aluminum foil. Yes. This container has an advantage that it has a relatively good heat insulating property, and can be easily manufactured at low cost.

Patent Document 2 (Patent No. 3596681) discloses a technique for foaming by heating and evaporating moisture contained in the same paper, and has a low melting point heat from the paper surface side to one wall surface of the body member. A two-layer heat insulating film consisting of a foamed inner layer of a plastic resin and a non-foamed outer layer of a thermoplastic resin having a higher melting point is applied. The interlayer strength between the foamed inner layer and the paper, the basis weight of the paper, A paper container that defines the thickness of the foamed layer and the non-foamed outer layer is described. Patent Document 2 also describes laminating a high-melting-point thermoplastic resin as a layer for maintaining the vapor pressure during heating on the other side of the paper!

[0004] Patent Document 1: Japanese Patent Laid-Open No. 57-110439

Patent Document 2: Japanese Patent No. 3596681

Disclosure of the invention

Problems to be solved by the invention

[0005] The container described in Patent Document 1 or 2 uses paper as the base material and the laminate layer (resin layer) is made of petroleum as a raw material, but its thickness is the minimum necessary for heat insulation. I'm suppressed. For this reason, the use of fossil fuels has been reduced as much as possible, and the environmental impact is smaller and the printability is superior compared to containers made entirely of expanded polystyrene.

However, the moisture contained in the paper substrate is heated and evaporated, and the thermoplastic resin layer is foamed by the evaporated moisture to provide heat insulation. Sufficient heat insulation can be obtained if the foaming condition occurs, such as holes, over-foaming, partial rupture, or the paper substrate strength thermoplastic resin layer being peeled off, or if the foamed state becomes uneven immediately. Nare ,.

Therefore, the present invention is to provide a paper container that can obtain a uniform foamed state and is excellent in heat insulation.

Means for solving the problem (1) The time until the molten thermoplastic resin comes into contact with the paper substrate from the T-die on at least one side of the paper substrate of the body material sheet of the barrel member in the paper container is 0.11-0.33 seconds. A body member raw material sheet of a paper container provided with a thermoplastic resin layer by extrusion lamination.

(2) A paper container comprising a barrel member and a bottom plate member, wherein the barrel member is formed with a foamed thermoplastic resin layer on the paper base material, and the foamed thermoplastic resin layer is made of a paper base material. The time required for at least one side of the molten thermoplastic resin to contact the paper substrate from the T die is 0.11 to 0

A paper container characterized in that a thermoplastic resin layer extruded and laminated so as to have 33 seconds is provided, and the thermoplastic resin layer is foamed by heating and evaporating moisture in the paper substrate.

(3) The paper container according to (2), wherein the extrusion-laminated thermoplastic resin layer has a resin oxidation degree of 0.4% to 1.5% by ESCA analysis.

(4) The paper container according to (2) or (3), wherein the extrusion-laminated thermoplastic resin layer is made of low-density polyethylene.

(5) It has a thermoplastic resin layer on both wall surfaces of the barrel member, and is made of a thermoplastic resin layer having a strength S on one wall surface and a thermoplastic resin having a higher melting point than the thermoplastic resin layer on the other wall surface. (2)-(4)! /, A paper container according to any of the above.

(6) Of the thermoplastic resin layers provided on both wall surfaces of the barrel member, the thermoplastic resin layer having a high melting point has a melting point of 125 ° C or higher and is a thermoplastic resin layer on the inner wall surface side of the barrel member. The paper container according to (2) to (5), characterized in that

(7) A method for producing a paper container comprising a body member and a bottom plate member, having the following steps A to C

Yes

A. At least one side of the paper base is extruded and laminated with a molten thermoplastic resin from the T-die to the paper base so that the time is 0.1;! To 0.33 seconds. A step of laminating a resin layer to produce a body member raw material sheet,

B. A process of assembling a body material sheet and a bottom material sheet to form a paper container,

C. A step of heat-treating the molded paper container to evaporate moisture in the paper base of the body member and foam the thermoplastic resin layer. (8) The paper container according to (4), wherein the low density polyethylene is MFR 10.0 to 14. Og / 10 min.

The invention's effect

[0007] 1. A paper container having a uniform foamed state and good heat insulation can be provided.

2. A uniform foam layer is formed, so clean printing is possible.

3. A container mainly composed of paper that does not use expanded polystyrene. It is an environment-friendly container and a container that has little adverse effect on the human body, and can be treated as paper-based waste. Brief Description of Drawings

FIG. 1 is a cross-sectional view of an example of a paper container according to the present invention.

FIG. 2 is a partial enlarged cross-sectional view of the body indicated by! /, Y in FIG.

FIG. 3 is an explanatory view showing a production method by extrusion lamination.

FIG. 4 is an optical micrograph (magnification 150) of a cross section of a container body member molded and foamed by a heat insulation test using the body member raw material sheet obtained in Example 1. The thickness of the foamed thermoplastic resin layer is about 700 m.

FIG. 5 is an optical micrograph (magnification 150) of a cross-section of the same container member molded and foamed in a heat insulation test using the body member raw material sheet obtained in Comparative Example 1.

Explanation of symbols

[0009] 1 Paper container

2 Body member

3 Bottom plate material

4 Paper base material

5 Foamed thermoplastic resin layer

5 'thermoplastic resin layer

6 Foam cell

7 Non-foamed thermoplastic resin layer

8 Winding

9 T-die

10 Cooling Ronore 11 Nipple

12 Body member raw material sheet BEST MODE FOR CARRYING OUT THE INVENTION

[0010] The paper container of the present invention can be roughly divided into three process forces: A. Production of body member raw material sheet, B. Molding of paper container, and C. Foaming by heat treatment. Hereinafter, the present invention will be described based on the drawings. The present invention is not limited to these.

[0011] A. Fabrication of body material sheet

(Composition of paper container)

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 basically includes a body member 2 and a bottom plate member 3.

FIG. 2 is a partially enlarged cross-sectional view of the body portion indicated by Y in FIG. In this example, a thermoplastic resin layer 5 (hereinafter referred to as a foamed thermoplastic resin layer 5) foamed on the surface of the paper substrate 4 is present on the outer wall surface side (outside of the container) of the body member. The plastic resin layer 5 has a structure in which foam cells 6 are arranged. On the inner wall surface side (inside the container) of the body portion, a thermoplastic resin layer 7 (hereinafter referred to as non-foamed thermoplastic resin) having a higher melting point than the thermoplastic resin of the foamed thermoplastic resin layer 5! Layer 7) exists. As will be described later, this non-foamed thermoplastic resin layer 7 does not foam during the heat treatment in container production, and prevents the escape of vaporized moisture from the paper base material to ensure the foamed thermoplastic resin layer 5 securely and securely. It should be fully foamed.

[0012] In addition, the bottom plate member 3 is preferably used as the bottom plate member raw material sheet provided with at least one thermoplastic resin layer, aluminum foil, etc. on at least one side of the paper base material. Is done. This is to prevent penetration of liquid or the like into the paper. The thermoplastic resin used for the bottom plate member can be the same as or different from that of the body member. Extrusion laminating methods, as well as pre-film-like ones such as wet laminating methods and dry laminating methods can be used. Any suitable method can be used.

[0013] (Extruded laminate)

FIG. 3 shows a manufacturing process of a sheet that is a raw material of the body member 2. Rolled out from winding 8 A thermoplastic resin layer 5 'is extruded from a T die 9 in the form of a molten resin film onto one surface of a paper base material 4, and is crimped while being cooled between a cooling roll 10 and a nip roll 11 facing the same. Obtain raw material sheet 12. Here, the distance until the extruded thermoplastic resin in the molten film state comes into contact with the paper substrate is called an air gap. In extrusion laminating, the operating conditions such as the melting temperature and laminating speed of the resin are not particularly limited as long as they are appropriately set depending on the type and apparatus of the resin used. In general, however, the melting temperature is, for example, 200 to 350 ° C. The stacking speed is about 50 to 200 m / min. If necessary, a corona treatment, an ozone treatment, or the like may be performed to improve the adhesiveness of the paper substrate or the thermoplastic resin. 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.

[0014] Although not shown, the non-foamed thermoplastic resin layer 7 is laminated with the non-foamed thermoplastic resin layer 7 on the opposite side of the body member raw material sheet 12 provided with the thermoplastic resin layer 5 '. The thermoplastic resin layer 5 ′ is laminated by a method of pasting together with a film-like material such as extrusion lamination, wet lamination method, dry lamination method, etc. before, simultaneously with, or after lamination.

In the present invention, the time required for the molten thermoplastic resin to pass through the air gap is 0.1;

It is important that it is 33 seconds. Due to the time range specified in the present invention, a uniform foamed state can be obtained when heat treatment is performed. The reason for this is not clear, but is presumed as follows.

Usually, in the extrusion laminating method, the higher the temperature of the molten thermoplastic resin, the higher the adhesiveness with the paper substrate, so the passage time of the air gap is set short. Usually, there is an example in which the air gap is 130 mm and the lamination speed is about 130 to 100 m / min (see, for example, Japanese Patent Laid-Open No. 2006-168775, Japanese Patent No. 3586868). In terms of transit time, this corresponds to 0.06-0.078 seconds.

On the other hand, the present invention has been found that the time during which the thermoplastic resin passes through the air gap has an effect on the foaming property. In the present invention, the thermoplastic resin is appropriately oxidized, so that the resin surface Is hard and easily stretched in the vertical direction, and it is considered that a good foamed state can be obtained. Insufficient oxidation if air gap transit time is less than 0.11 seconds When the foamed cell is foamed and the foamed cell becomes soft, the foamed cell stretches in the horizontal direction instead of vertically, becomes overfoamed, the foamed cell wall is thin and weak, and it tends to burst. A uniform foamed state cannot be obtained such as delamination. On the other hand, if it is longer than 0.33 seconds, the adhesion to the paper substrate is lowered, and the thermoplastic resin layer is pushed up by the evaporated water from the paper substrate, causing peeling, and the adhesion to the paper substrate. If it is inferior in nature, it tends to cause excessive foaming. A more preferable air gap passage time is 0.15 seconds or more, 0.30 seconds or less, more preferably 0.25 seconds or less. The degree of oxidation is preferably 0.4 to 1.5% by ESCA analysis.

[0016] (paper substrate)

The paper used in the present invention is produced by tangling plant fibers or plant fibers with other fibers! /, Les, wood fibers such as conifers or hardwoods as raw materials for plant fibers , Bast fibers such as Mitsumata and Kozo, non-wood fibers such as nogas, kenaf and hemp, cotton fibers, waste paper, etc., and the ability to mention high-quality paper, coated paper, recycled paper, etc. It is not limited to these. The basis weight of the paper is suitably of the order 400 g / m ² or less on 100 g / m ² or more, the basis weight is too low, foaming small, hydrous rate required les, because enough or foam allowed In addition, it is easy to feel the heat when holding the container by hand. Preferably it is 200 g / m ² or more, more preferably 250 g / m ² or more. On the other hand, if the basis weight is too high, it is uneconomical because it exceeds the desired rigidity as a body member, and bubbles are formed more than necessary, and molding processability is also reduced. Further, the water content in the paper substrate is preferably 5 to 15% by weight because if the amount is too large, the rigidity decreases, resulting in inferior moldability of the container, and excessive foaming or rupture of the foamed cells. Is more preferably 6 to 10% by weight.

[0017] (Foamed thermoplastic resin layer)

The thermoplastic resin used as the foamed thermoplastic resin layer is not particularly limited as long as it can be extruded and foamed, and it is possible to use either a crystalline resin or an amorphous resin. it can. Crystalline resins include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, polyethylene pentene and other polyolefin resins, polyester-based resins, polyamide, polyacetal, PPS resins, etc. The power to raise S. Non-crystalline resins include polystyrene and poly Examples include butyl chloride, ABS resin, acrylic resin, modified PPE, polycarbonate, polyurethane, poly (vinyl acetate), and non-crystalline polyethylene terephthalate (PET). These thermoplastic resins may be a single resin or a plurality of resins, but are preferably a single layer from the viewpoint of foamability.

The melting point of the thermoplastic resin is preferably about 80 to 120 ° C. In the present invention, polyethylene is preferred because of its 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 888~9 10kg / m ^3, low density polyethylene 910~925kg / m ^3, medium density polyethylene 925 ~940kg / m ^3, higher density polyethylene 940～970Kg / m ³ or so. The melting point for linear low density polyethylene is 55 ° C ~; 120 ° C, for low density polyethylene 105 ~ 120. C, 120 to 125 for medium density polyethylene; C, and higher density polyethylene is 125 to 135 ° C. When low density polyethylene is used as the thermoplastic resin, the melting temperature at the time of extrusion lamination is 315 ° C or higher, preferably 330 ° C or higher. In normal cases, the force is about 300 ° C. Since the time to pass through the air gap is longer than usual, the high temperature is set taking this into consideration.

When low density polyethylene is used as the thermoplastic resin, the MFR is preferably 10.0 to 14 .Og / 10 min. MFR is an index of resin fluidity, and MFR low density polyethylene in this range is used under the conditions of the present invention where the time required for the molten thermoplastic resin to pass through the air gap is 0.11-0.33 seconds. By doing so, the foamability is improved.

(Non-foamed thermoplastic resin layer)

In the present invention, in order to increase the foaming efficiency, the wall surface opposite to the wall surface having the foamed thermoplastic resin layer of the body member has a higher melting point than the foamed thermoplastic resin layer and is made of a thermoplastic resin and heat-treated. It is preferable to cover with a thermoplastic resin layer (non-foamed thermoplastic resin layer) that does not foam when it is blown, or with an aluminum foil or the like. If one side of the paper substrate is ground, the moisture in the paper will evaporate from the uncoated surface into the atmosphere during the heat treatment, and it will be difficult to generate bubbles sufficiently. Therefore, by providing such a coating layer, moisture in the paper Can be efficiently contributed to foaming. It is preferable that these non-foamed thermoplastic resin layers and aluminum foils are present on the inner wall surface side of the body member because 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 the presence of the non-foamed thermoplastic resin layer provides a smooth hand and glossy appearance. This also improves the waterproofness of the container.

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 same case, it is possible to generate a difference in melting point by giving 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 in melting point between 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 There is no particular limitation as long as it does not melt and the spread of the evaporated water can be suppressed, but it is preferably 125 ° C or higher.

The method for forming the non-foamed thermoplastic resin layer is not particularly limited, and it may be laminated by extrusion lamination on the opposite side of the foamed thermoplastic resin layer of the paper substrate or on the foamed thermoplastic resin layer, or wet. A method of laminating with a previously formed film such as a laminating method and a dry laminating method can be used as appropriate. When laminating multiple 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. From the viewpoint of adhesion between thermoplastic resin layers and production efficiency, each thermoplastic resin is led to each T die in a molten state using multiple extruders, and extruded from each T die at the same time to be laminated and bonded. The method to do is suitable. Such a method capable of simultaneously forming two or more thermoplastic resin layers is called a co-extrusion 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, in order to improve the adhesiveness of the thermoplastic resin to the paper base as necessary, corona treatment, Done processing, etc.

[0020] (Other)

Regarding the thickness of each of the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer, the foamed thermoplastic resin layer should be thick enough to give the desired heat insulation when foamed. Although it is not particularly limited, the thickness before foaming is about 40 to 80 m, and after foaming is about 400 to 2000 ^ 111. In addition, the non-foamed thermoplastic resin layer is also thick enough to prevent evaporation of evaporated water, and if it is on the inner wall surface side of the body member, it should be thick enough to ensure liquid penetration resistance. It is not specifically limited, It is about 20-50 m. Further, the outer wall surface side and the inner wall surface side of the body member may have the same laminated structure or may be different. The type of resin used and other materials may be the same or different.

[0021] In addition, various additives that are generally used 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. it can. These additives include, for example, antistatic agents, white pigments (inorganic pigments such as titanium oxide, calcium carbonate, clay, talc, silica, etc.), anti-blocking agents (acrylic beads, glass beads, silica, etc.), ultraviolet absorption There are agents.

[0022] B. Molding of paper containers

In the present invention, the body member raw material sheet 12 and the bottom plate member raw material sheet are formed by a conventional force cup manufacturing apparatus or cup molding machine. First, the trunk member raw material sheet 12 is fed out from the take-up roll, and necessary printing is performed at predetermined locations. At this stage, barcodes can be printed. Use a normal means or procedure to position the printed part, etc. Use force S.

Next, the blank for the body member and the blank for the bottom plate member are punched out from each raw material sheet, and assembled into a container shape by a conventional cup molding machine. Here, if the foamed thermoplastic resin layer 5 is present on one or both of the outer wall surface side and the inner wall surface side of the body member, the heat insulation, the touch, the appearance aesthetics, etc. may be appropriately determined as desired. However, if the inside of the container has a foamed surface, the foamed resin may be damaged by chopsticks, forks, etc. during food and drink and enter the mouth. So, for example For example, the body member raw sheet 12 is assembled so that the thermoplastic resin layer 5 '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.

[0023] C. 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 4 of the body member 2 evaporates, and the thermoplastic resin layer 5 ′ foams to become the foamed thermoplastic resin layer 5.

The heating temperature and heating time vary depending on the paper substrate and the type of thermoplastic resin used, and the optimal combination of heating temperature and heating time for the thermoplastic resin used can be determined as appropriate. A temperature slightly higher than the melting point of the thermoplastic resin to be used (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. ~ About 6 minutes. 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 with hot air or electric heat in a tunnel equipped with a conveyor, it can be mass-produced at low cost.

[0024] Other.

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 technology that partially suppresses foaming by applying a paint containing 5 wt% to 40 wt% of a synthetic resin component on a part of the body member that becomes the outer wall surface (Patent No. 3014629), which becomes the outer wall surface A technique for applying a synchronized ink that forms a smooth printing surface in synchronism with foaming on the surface of the barrel member (Japanese Patent No. 3408156), and a technique for providing a flange portion at the upper edge of the opening of the container barrel member. A force that includes a technique for forming a double structure by forcibly processing the mold and polymerizing the inner winding end on the upper part of the flange (Japanese Patent Laid-Open No. 2001-354226) is not limited thereto. Further, in order to enhance the printability, an ink receiving layer mainly composed of a pigment and a binder may be provided on the outermost layer serving as the outer wall surface of the body member.

[0025] As described above, the present invention heats a paper provided with a thermoplastic resin layer to vaporize water contained in the paper, thereby confining water vapor bubbles in the molten thermoplastic resin layer. Thus, the technology for forming the foam layer is utilized. This is because the molten state of the thermoplastic resin layer is low. If it is viscous, there is a risk that steam will escape and pinholes will be generated, or small bubbles will join and break.

In contrast, in the present invention, the resin layer surface is formed in a skin shape by advancing the oxidation of the resin, which is considered to have an adverse effect in ordinary lamination, by increasing the time for passing through the air gap. The foam is retained in the resin layer to maintain a small bubble state and prevent the occurrence of pinholes. In addition, after extrusion from the τ die, extrusion is performed at a higher temperature than usual in order to ensure the adhesive force that the thermoplastic resin contacts and adheres to the paper substrate. In addition, this high temperature is thought to fulfill the function of promoting oxidation.

The present invention vaporizes the moisture contained in the paper and confines it in a thin molten thermoplastic resin layer to form a large number of small bubbles to exert heat insulation. It was difficult to form a heat-insulating layer in a good state, but it was found that it can be controlled by increasing the time required to pass through the air gap in the laminated laminate.

Furthermore, a resin layer having a high melting temperature is provided on the opposite surface of the paper base material to prevent vapor escape when the water contained in the paper base material is vaporized, thereby forming a low temperature molten thermoplastic resin layer. It is intended to improve the accuracy of keeping steam.

Example

[0026] The effects of the present invention will be described in detail below with reference to examples.

[Example 1]

As a foamed thermoplastic resin layer that forms the outer wall of the body member when used as a paper container on one side of a base paper with a basis weight of 300g / m ² (water content 8%), melting point 108 ° C, MFR 13.8g / 10min Low-density polyethylene (LDPE) is extruded at a melting temperature of 340 ° C to a thickness of 70 111, and this molten resin and base paper are linearly 15kgf / cm using a cooling roll and a nip roll with a hardness of 70 degrees. Press with 'crimped. At this time, the time until the molten resin discharged from the T-die contacts the base paper (air gap passage time) was set to 0.112 seconds. On the opposite side of the base paper, a non-foamed thermoplastic resin layer serving as the inner wall of the lunar member has a melting point of 128 ° C, MFR 6.5 g / 10 min medium density polyethylene (medium density PE), 40 m thick. In such a manner, extrusion lamination was performed at a melting temperature of 320 ° C. to obtain a body member raw material sheet. [Example 2]

A body member raw material sheet was obtained in the same manner as in Example 1 except that the time until the molten resin discharged from the T-die contacted the base paper was 0.186 seconds.

[0029] [Example 3]

A body member raw material sheet was obtained in the same manner as in Example 1 except that the time until the molten resin discharged from the die was in contact with the base paper was 0.223 seconds.

[0030] [Example 4]

A body member raw material sheet was obtained in the same manner as in Example 1 except that the base paper having a basis weight of 300 g / m ² was changed to a base paper having a basis weight of 320 g / m ² (water content 8%).

[0031] [Example 5]

Example: The non-foamed thermoplastic resin layer used as the inner wall surface of the body member was changed to polypropylene (PP) having a melting point of 165 ° C instead of medium density polyethylene (medium density PE) having a melting point of 128 ° C. A body member raw material sheet was obtained in the same manner as in 1.

[0032] [Example 6]

A body member raw material sheet was obtained in the same manner as in Example 1 except that low density polyethylene (LDPE) having a melting point of 108 ° C was laminated to a thickness of 50 m.

[Example 7]

The body member raw material sheet obtained in Example 1 was heated at 123 ° C. for 4 minutes to obtain a foam sample piece.

[Example 8]

Low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13.8g / 10min instead of low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13.8g / 10min as the foamed thermoplastic resin layer 88. Low-density polyethylene (LDPE) with 5 wt%, melting point 107 ° C, MFR8.2g / 10min 11.5% except mixed resin (melting point 108 ° C, MFR13. Og / 10min) A body member raw material sheet was obtained in the same manner as in Example 1.

[0035] The MFR of the mixed resin was determined by the following formula.

logX = aiogY + blogZ

(a, b: mixing ratio of each resin, X: MFR of mixed resin, Y, Z: MFR of each resin) [Example 9]

As a foamed thermoplastic resin layer, low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13. 8g / 10min instead of low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13.8g / 10min 90. 0% by weight, melting point 108 ° C, low density polyethylene (LDPE) with MFR 7.5g / 10min 10.0% by weight mixed resin (melting point 108 ° C, MFR13. Og / 10min) A body member raw material sheet was obtained in the same manner as in Example 1.

[0037] [Example 10]

As a foamed thermoplastic resin layer, low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13.8 g / 10 min instead of low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13.8 g / 10min20. Except for changing to a mixed resin (melting point 106 ° C, MFR20. Og / 10 min) consisting of 0 wt%, melting point 106 ° C, MFR22. Og / 10 min low density polyethylene (LDPE) 80.0 wt% In the same manner as in Example 1, a body member raw material sheet was obtained.

[0038] [Example 11]

As the foamed thermoplastic resin layer, low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13. 8g / 10min instead of low-density polyethylene (LDPE) with a melting point of 108 ° C and MFR13.8g / 10min 77. 0% by weight, melting point 108 ° C, MFR 7.5 g / 10 min low density polyethylene (LDPE) 23.0 wt% mixed resin (melting point 108 ° C, MFR12. Og / 10 min) A body member raw material sheet was obtained in the same manner as in Example 1.

[0039] [Comparative Example 1]

A body member raw material sheet was obtained in the same manner as in Example 1 except that the time until the molten resin discharged from the T die contacted the base paper was 0.335 seconds.

[0040] [Comparative Example 2]

A body member raw material sheet was obtained in the same manner as in Example 1 except that the time until the molten resin discharged from the T-die contacted the base paper was 0.098 seconds.

Table 1 shows the results of the following evaluation tests using the body member raw material sheets obtained in the above Examples and Comparative Examples. The case where the body member raw material sheet obtained in Example 1 was used and foaming was not performed was referred to as Reference Example 1.

[0041] <Oxidation degree> The degree of oxidation was measured by ESCA analysis for the foamed thermoplastic resin layer of the body material sheet before foaming. A smaller value power S indicates a lower oxidation degree.

ESCA is an abbreviation for electron spectroscopy for analysis. It irradiates X-rays, measures the energy of photoelectrons from atoms excited by X-rays, analyzes the energy specific to atoms, and identifies constituent elements.

In the present invention, the polyethylene layer forming the surface layer is irradiated with X-rays, and the ratio is determined according to the ratio of C and O.

2

To obtain the degree of oxidation. Polyethylene usually has only CH bonds, so it does not contain O

2

(Note that H has too little energy and cannot be measured by X-ray analysis! /).

To measure, cut a 5mm square sample and irradiate the surface with X-rays. The irradiated X-rays are the force S that reaches the paper base S, and the photoelectron that excites the base paper is absorbed and dispersed in the middle. Actually, the energy of the surface layer of μm is measured!

[0042] <Foaming (thickness)>

The total thickness of the body member raw material sheet before foaming was measured. Next, the sample piece (10 cm × 10 cm) was placed in a dryer at 115 ° C. or 123 ° C. and heated for 4 minutes to foam the foamed thermoplastic resin layer, thereby obtaining a foamed sample piece. The total thickness after foaming was measured.

[0043] <Foaming (state)>

About said foam sample piece, the foaming state was visually evaluated on the following reference | standard.

◎ · · · Uniform and fine foamed state, good.

○ · · · Although there is some over-foaming, there is no problem as a heat-insulating container.

Δ: Although it is slightly over-foamed, it can be used as a heat insulating container.

X: Over-foamed or insufficiently foamed and cannot be used as a heat insulating container.

[0044] <Adhesion with paper substrate>

The sample piece (10cm x 10cm) of the body material sheet before foaming was peeled manually between the base paper and the low-density polyethylene layer, and the degree of ease of peeling at that time was evaluated according to the following criteria.

A: It is firmly attached and cannot be peeled off.

○ ··············································································.

Δ: There is resistance but peeling is possible. x-· · Adhesion is weak or can be easily peeled off.

[0045] <Insulation>

Combining the body material sheet with the bottom plate material sheet (medium density polyethylene extruded to a thickness of 40 m on a base paper with a basis weight of 220 g / m ² ), a container with a diameter of 95 mm and a height of 115 mm Was molded and heated in a dryer at 115 ° C for 4 minutes to foam. Then, 90 ° C hot water was poured into the foamed container, and after 3 minutes, the outer wall surface of the container was touched by hand and evaluated according to the following criteria.

A: The container can be sufficiently held with a hand that is too hot and has excellent heat insulation. 〇 ···· Slightly hot, but can hold the container by hand and has good thermal insulation.

Δ: Slightly good thermal insulation that makes it difficult to hold the container sufficiently with a hot hand.

X · · · Poor insulation that makes it difficult to hold the container with hot hands.

[0046] [Table 1]

From this result, the air gap transit time is suitably in the range of 0.11-0.33 seconds, preferably 0.15-0.25 seconds. The degree of oxidation is preferably 0.4 to; 1.5%, particularly preferably 1.0% or less.

Claims

The scope of the claims

[1] The time required for the molten thermoplastic resin to contact the paper base from the T-die on at least one side of the paper base of the body material sheet in the paper container is 0.11 to 0.33 seconds. A raw material sheet for a trunk member of a paper container provided with a thermoplastic resin layer by extrusion lamination.

[2] A paper container comprising a trunk member and a bottom plate member,

The body member is formed with a foamed thermoplastic resin layer on the paper substrate.

The foamed thermoplastic resin layer is formed by extrusion laminating so that the time required for the molten thermoplastic resin to contact the paper substrate from the T-die is at least 0.1; A paper container, wherein a thermoplastic resin layer is provided and the thermoplastic resin layer is foamed by heating and evaporating water in the paper substrate.

[3] The paper container according to [2], wherein the extrusion-laminated thermoplastic resin layer has a resin oxidation degree of ESCA analysis value of 0.4% to 1.5%.

4. The paper container according to claim 2 or 3, wherein the extrusion-laminated thermoplastic resin layer is made of low-density polyethylene.

[5] It has a thermoplastic resin layer on both wall surfaces of the body member, and the thermoplastic resin layer on one wall surface has a higher melting point than the thermoplastic resin layer on the other wall surface, and is made of a thermoplastic resin. The paper container according to any one of claims 2 to 4, which is characterized by the above.

[6] Of the thermoplastic resin layers provided on both wall surfaces of the trunk member, the thermoplastic resin having a high melting point has a melting point of 125 ° C or higher, and is a thermoplastic resin layer on the inner wall surface side of the trunk member. The paper container according to any one of claims 2 to 5, wherein the paper container is provided.

[7] A method for producing a paper container comprising a body member and a bottom plate member, comprising the following steps A to C.

B. The process of assembling the body member raw material sheet and the bottom member raw material sheet, and molding the paper container, C. heat-treating the molded paper container to evaporate the moisture in the paper base material of the body member, and A step of foaming the plastic resin layer.

[8] The low-density polyethylene has an MFR of 10.0 to 14. Og / 10 minutes. The paper container described.