JP5573421B2 - Paper container - Google Patents

Description

  The present invention relates to a paper container, and more particularly to a paper container used in the shape of a paper squeeze tray, a paper cup, or the like.

  Paper containers used for containers such as liquid or viscous foods, liquid foods containing solids, or solid foods need to be waterproof and prevent penetration. A resin layer laminated is used. In addition, the heat resistance required when heating food in a microwave oven and the perfume retention to prevent odorous components from escaping to the outside when filled with foods with strong odors are also important performances. It becomes.

  As an improved technique related to a paper container, for example, Patent Document 1 discloses an aroma retaining resin layer (A), a polypropylene layer (B), an adhesive resin layer (C), a gas barrier layer (D), and adhesive strength with paper. There is disclosed a multilayer container in which a laminate composed of an ethylene copolymer layer (E) having a 180-degree peeling (peeling speed 300 mm / min.) Width of 150 g / 15 mm or more is bonded to the paper (E) layer surface. Yes. Patent Document 2 discloses that a polypropylene film formed by air-cooled inflation molding film formation of a resin composition containing 50 to 97% by weight of a polypropylene resin and 3 to 50% by weight of an α-olefin copolymer is at least a paper layer. The package is a paper container in which a laminated material is formed by laminating and a polypropylene film layer as the innermost layer of the laminated material.

JP 2000-135664 A (Claims etc.) JP 2003-31718 A (Claims etc.)

  As described above, various studies have been made on paper containers in the past, but they are not yet sufficient, and in particular, there is a demand for the realization of paper containers having superior performance with respect to aroma retention and heat resistance. It was done.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a paper container having better aroma retention and heat resistance than conventional ones.

  Among resin materials, polybutylene terephthalate (PBT) resin is known to have excellent fragrance retention and heat resistance. However, since PBT resin generally has poor laminating workability when a resin layer is formed on a paper substrate, a paper container using PBT resin has a drawback that it cannot be easily manufactured.

  As a result of diligent investigation focusing on the processability of such PBT resin, the present inventor can easily form a resin layer on a paper substrate by using a PBT resin having a specific range of physical property values. Thus, the present inventors have found that a paper container having excellent fragrance retention and strength can be realized, and have completed the present invention.

That is, the paper container of the present invention is a paper container that is sealed by sealing a lid member, and is a laminate in which a resin layer made of polybutylene terephthalate resin is laminated on at least one surface of a paper base material by an extrusion lamination method. The polybutylene terephthalate resin has a melting point of 200 to 230 ° C., a melt index of 3 to 13 g / 10 minutes, a glass transition temperature Tg of 30 to 35 ° C., and aroma retention and heat resistance. It is characterized by having.

  The paper container of the present invention preferably has the shape of a paper squeeze tray or paper cup.

    According to the present invention, by adopting the above-described configuration, it is possible to realize a paper container having better fragrance retention and heat resistance than the conventional one.

It is a perspective view which shows an example of the paper container of this invention. It is typical sectional drawing which shows one structural example of the laminated body which concerns on this invention. It is sectional drawing which shows the A-A 'cross section in FIG. It is sectional drawing which shows the B-B 'cross section in FIG. It is sectional drawing and a top view which show the other example of the paper container of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, the perspective view which shows the paper cup of an example of the paper container of this invention is shown. The illustrated paper cup 10 includes a substantially cylindrical body 11 and a bottom 13 joined to the lower end of the body 11, and a curl 15 is formed on the upper end of the body 11. FIG. 2 is a schematic cross-sectional view showing a structural example of a laminate used for the paper container of the present invention.

  The paper container of the present invention comprises a laminate 20 having a resin layer 23 made of PBT resin on one or both sides of a paper base material 21 as shown in FIG. 2, and has a fragrance retention and heat resistance. It is what. By adopting such a configuration, a paper container having excellent heat resistance and aroma retention can be obtained, and a paper container that can be suitably used for foods with a strong smell and also suitable for use in a microwave oven or the like is realized. It became possible.

  Moreover, as PBT resin which comprises the resin layer 23 of the paper container of this invention, melting | fusing point is 200-230 degreeC, Melt index on the conditions of 235 degreeC and a 2160-g load is 3 to 13 g / 10min, Preferably It is necessary to use one having a glass transition temperature Tg of 30 to 35 ° C. of 3 to 6.5 g / 10 minutes. By using a PBT resin having a physical property value in this range, it became possible to secure a processability when forming a resin layer on a paper substrate and to make a paper container that can be easily manufactured. Examples of the PBT resin that satisfies the physical property values include DURANEX 600FP, 700FP, and 800FP manufactured by Polyplastics Co., Ltd.

  In addition, you may add additives, such as a coloring agent, a pigment, an extender pigment, a filler, a lubricant, a plasticizer, surfactant, and an extender, to the said PBT resin.

Examples of the paper base material 21 include moldability, bending resistance, rigidity, and the like, and examples thereof include bleached or unbleached paper, paperboard, processed paper, and the like. Yes, a cup base paper having good suitability for paper cup production can be exemplified. Moreover, the paper base material may contain various additives. The paper substrate, those having a basis weight of about 80~600g / ^{m 2,} in particular, it is preferable to use one having a basis weight of about 100~450g / ^{m 2.}

  As a paper base material, it is preferable to contain kraft pulp and rosin and / or alkyl ketene dimer as a sizing agent because it gives strength to the paper container and has a high degree of sizing, and the contents and the like do not easily permeate. Therefore, it is also preferable in that a water-resistant paper cup or paper squeeze tray can be manufactured. The blending ratio is preferably kraft pulp: sizing agent = 100: 0.15-1.5 on a mass basis. If the blending amount of the sizing agent is too small, the sizing degree is insufficient and the contents and the like are likely to permeate. If the blending amount of the sizing agent is too large, the sizing degree is too high and the adhesion to the resin layer is lowered.

  The resin layer 23 is laminated on the paper substrate 21 using an extrusion lamination method. That is, in this invention, the said PBT resin is laminated | stacked on a base material as a resin layer by the extrusion lamination method. The extrusion lamination method is a so-called method called extrusion coating (EC) by those skilled in the art. First, the extruded resin is heated and melted with an extruder, expanded and expanded in a necessary width direction with a T-die, and extruded into a curtain shape. By letting the molten resin flow down onto the paper substrate and sandwiching it between a rubber roll and a cooled metal roll, the formation of the extruded resin layer and the adhesion and lamination to the paper substrate are performed simultaneously. Since it can be processed in the form of a roll, it is a method with extremely good production efficiency.

  Using the EC method, the temperature of the molten resin when the PBT resin is heated and melted with an extruder and extruded from the T die into a curtain shape is about 220 to 270 ° C., preferably about 240 to 260 ° C. If the temperature of the molten resin is less than this range, there is a possibility that adhesion failure or processing failure may occur. On the other hand, when the temperature of the molten resin exceeds this range, it approaches the decomposition temperature of the resin, so that the flow of the resin from the T die is disturbed or colored.

  The EC method capable of forming a film and a laminate at the same time has the advantage of reducing the cost of high-speed processing, and is usually 80 m / min or higher, preferably 100 m / min or higher, more preferably 120 m / min or higher on the substrate. Thus, the resin layer can be laminated by an extrusion lamination method. In addition, the thickness of the resin layer 23 formed by one EC method is usually 5 to 200 μm, preferably 20 to 100 μm. If the film thickness of the resin layer 23 is less than this range, the resin temperature of the resin flowing down from the T die during EC processing tends to be low, and the heat capacity is small and the adhesion to the paper substrate is poor. On the other hand, if the film thickness of the resin layer 23 exceeds this range, the adhesion to the paper base material will be improved, but the film is likely to be cut off due to the high melt viscosity of the resin from the T dice. Remarkably deteriorates. If thickness is required, EC processing may be repeated a plurality of times.

  In the present invention, an adhesion promoter called an anchor coat agent (AC agent) may be applied in order to firmly bond the resin layer and the substrate, and instead of the anchor coat agent, Easy adhesion treatment such as corona discharge treatment, plasma discharge treatment, and ozone gas treatment may be performed. Examples of the anchor coating agent include organic titanium anchor coating agents such as alkyl titanates, isocyanate anchor coating agents, polyethyleneimine anchor coating agents, polybutadiene anchor coating agents, and polyurethane anchor coating agents. The anchor coating agent may be applied by a known coating method such as roll coating or gravure coating and dried. The thickness of the anchor coating agent is usually 0.01 to 10.0 μm, preferably 0.1 to 5.0 μm.

  The paper container of the present invention may have a shape such as a paper squeeze tray or a paper cup.

  A known production method can be used as a production method for producing the paper container of the present invention in the shape of a paper cup as shown in FIG. That is, first, (1) while preparing the body member 41 that forms the body portion 11, (2) preparing the bottom member 43 that forms the bottom portion 13, and (3) punching the body member 41 into a truncated cone shape. (4) The bottom member 43 is punched into a circular shape to form a bottom material blank. Next, (5) the body blank is wound into a cylindrical shape so that the resin layer 23 is on the inside, and the side end portions are partially overlapped to form a body pasting portion 31 (see FIG. 3). The cylindrical body part 11 is formed by heat-treating and pressing the part 31. Next, (6) the bottom member is inserted into the bottom end portion of the cylindrical body 11 so that the outer periphery of the bottom plate blank is formed upright in a cylindrical shape to form the upright forming portion 33, and the bottom member and the bottom member are inserted. Hot air or the like is blown onto a portion where the bottom end portion of the barrel portion is joined, and the resin layer 23 existing in the portion is heated and melted. Then, the end portion of the cylindrical barrel portion 11 is inward by a curling die. The barrel portion 11 and the bottom portion 13 are covered with the upright forming portion 33 and knurled from the inner diameter side to the barrel pasting portion 31 between the tip end portion of the cylindrical barrel portion 11 and the upright molding portion 33 of the bottom portion 13. Are tightly bonded to each other to seal the joint (see FIG. 4). Next, (7) the curl 15 is formed by curling the upper end of the body 11 outward. As the sealing method, a hot air method is usually used, but other generally used methods such as an ultrasonic method and a heating and pressing method using a heating bar may be used, and there is no particular limitation.

  FIG. 5 is a perspective view showing a paper squeeze tray of another example of the paper container of the present invention. The illustrated paper squeeze tray 110 is formed by a well-known method, and has an opening at the top, a bottom surface 111, a side wall surface 113 through the bottom surface 111, and an outward flange portion 115 around the periphery of the opening. The portion 117 is folded along a ruled line and rises to the flange portion, and has a tray shape or a dish shape. The outer shape of the paper squeeze tray is rectangular in the illustrated example, but may be any polygonal shape such as a triangle, circular shape, elliptical shape, etc., and the depth and flange shape can also be arbitrarily determined. Although not shown, when the paper container of the present invention is formed in the shape of a paper squeeze tray, a lid covering the top of the paper squeeze tray 110 can be heat sealed to the flange portion 115 and sealed. However, when the paper container of the present invention is used for heating in a microwave oven, it is preferable to make a hole in a part of the paper container, partially open it, or provide an opening window in advance.

  As needed, an inorganic compound layer such as silica, alumina, zinc oxide, tin oxide, magnesium oxide, a metal vapor deposition layer, a metal foil, or the like is provided on the interlayer and / or the layer surface of the laminate forming the paper container of the present invention. A protective layer such as a plastic film layer such as a biaxially stretched polyethylene terephthalate (PET) film or a biaxially stretched polyamide (ON) film excellent in heat resistance and / or mechanical strength may be optionally laminated. . In addition, when laminating each layer, an easy adhesion layer and / or treatment such as an adhesion layer, a primer layer, or a corona treatment may be performed in order to improve adhesion and other functions. As a laminating method using a gas barrier layer, a protective layer, a primer layer, etc., a known method can be used. For example, a dry laminating method using a two-component curable polyurethane adhesive or the like, via an anchor coating agent. Examples thereof include an extrusion coating method and a sandwich lamination method.

  In the paper container of the present invention, a known end surface processing method such as skive hemming, hemming, or tape application is used at the joint portion such as the trunk, particularly when the end surface of the paper is exposed inside the paper container. In addition, by preventing exposure of the end face of the paper, water resistance and sealing performance can be improved. Further, the end face of the paper may be exposed at the outer joint portion of the top, bottom and / or trunk of the paper container. Of course, if necessary, using a processing method such as skive hemming or hemming. The paper end face may be hidden to improve water resistance and sealing performance. For example, in the body member 41 (body body blank) shown in FIG. 3, a skive and hemming process is applied to one end portion to improve the adhesiveness in the body pasting portion 31 and improve water resistance and sealing performance. Further, the paper container can be appropriately provided with a cover material, a pull tab type opening mechanism, or the like as an outlet for the contents depending on the shape of the container. Furthermore, the paper container may be provided with a half cut line for opening by laser light irradiation or mechanical means, or a perforation line for half cut, etc. to form a takeout port.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example 1>
Using a cup base paper having a basis weight of 255 g / m ^{2 as} a paper base material and carrying out a corona treatment in-line on one side, PBT resin (Duranex 800FP, manufactured by Polyplastics Co., Ltd.) is used for the extrusion lamination method. A resin layer having a thickness of 30 μm was formed at 0 ° C. to obtain a laminate (body member and bottom member) composed of paper base material 255 μm / resin layer 30 μm.

  The above drum member is punched into a truncated cone shape, and this blank plate is rolled into a cylindrical shape so that the resin layer is on the inside. A cylindrical barrel was formed by pressing twice with a heating bar made of iron at a predetermined temperature.

  A bottom plate in which the outer periphery of the bottom plate blank is erected in a cylindrical shape is inserted into the bottom end portion of the cylindrical body portion, and a predetermined portion is joined to a portion where the bottom portion and the bottom end portion of the body portion into which the bottom portion is inserted are joined. Hot air of temperature is blown to heat and melt the resin layer present in the part, and then the end of the cylindrical body part is bent inward by a curling die to cover the upright molding part, and the cylindrical body is The body part and the bottom part were tightly bonded to each other by sealing the joint part by knurling from the inner diameter side to the body pasting part between the tip part of the part and the upright molding part of the bottom part. Next, the upper end of the barrel was curled outward to form a curl, and a paper cup of Example 1 having a capacity of 500 ml was obtained.

<Example 2>
Using the laminate produced in Example 1, a paper having a short side of 100 mm, a long side of 150 mm, a depth of 35 mm, and a flange width of 7 mm by a known paper drawing method in which the resin layer is placed inside and pressed with upper and lower molds. An aperture tray was formed to obtain a paper aperture tray of Example 2.

<Comparative Example 1>
A paper cup of Comparative Example 1 was obtained in the same manner as Example 1 except that low density polyethylene (LDPE) was used instead of the PBT resin.

<Evaluation method>
<Incense retention>
The paper cups or paper squeeze trays prepared in each Example and Comparative Example were filled with Japanese tea, coffee and solid curry, respectively, and sealed with a lid made of the same laminate. These paper cups or paper squeeze trays were put in a sealed container and stored at room temperature for 1 week, and then the presence or absence of odor in the sealed container was confirmed.

<Heat resistance>
From the opening at the upper end of the paper cup or paper squeeze tray prepared in each example and comparative example, 300 g of curry was filled, heated in a microwave oven at 500 W for 3 minutes, and then the curry was poured out. Thereafter, an empty paper cup or paper squeeze tray was washed with water, and the resin layer on the inner surface was visually observed. Those without oil soaking were accepted, and those with oil soaking were rejected.

<Evaluation results>
<Incense retention>
In Examples 1 and 2, no odor was felt in the sealed container with respect to all the contents, and the effect of aroma retention could be confirmed. On the other hand, in Comparative Example 1, an odor was felt in the sealed container, and an effect of aroma retention was not recognized.

<Heat resistance>
In Examples 1 and 2, the oil was not soaked in all and passed, and the resin layer in contact with the curry was neither colored nor cocoon skin-like. On the other hand, in Comparative Example 1, the oil soaked in and failed, and the resin layer in contact with the curry was colored in yellow, and a cocoon skin-like deformation was also observed.

DESCRIPTION OF SYMBOLS 10 Paper cup 11 trunk | drum 13 bottom part 15 curl 20 laminated body 21 paper base material 23 resin layer 31 trunk pasting part 33 upright molding part 41 trunk | drum member 43 bottom member 110 paper drawing tray 111 bottom part 113 side wall part 115 flange part 117 corner | angular part

Claims (2)

A paper container which is sealed by sealing a lid material, comprising a laminate in which a resin layer made of polybutylene terephthalate resin is laminated on at least one side of a paper base material by an extrusion lamination method, and the polybutylene terephthalate resin A paper container characterized by having a melting point of 200 to 230 ° C., a melt index of 3 to 13 g / 10 min, a glass transition temperature Tg of 30 to 35 ° C., and having aroma retention and heat resistance .   2. A paper container according to claim 1 having the shape of a paper squeeze tray or paper cup.

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