JP3351075B2 - Food container manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a food container. More specifically, the present invention relates to a food container used as a cup-shaped or tray-shaped food container required to have high heat retention and heat insulation properties, and a tray-shaped container required to have a cushioning property such as wrapping paper for fruits and vegetables. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, foamed polystyrene containers have been widely used as food containers because they are excellent in heat insulation and heat retention, are good in forming and processing, and are inexpensive. Interest in protection is rapidly increasing, and there is an increasing demand for paper-based food containers that are easily incinerated, recyclable, and biodegradable by microorganisms in soil.

[0003] Such a heat-insulating and heat-insulating container mainly composed of a paper substrate is intended to prevent the heat of the contents from being directly transmitted to the finger holding the container and to improve the strength of the container. A method of providing a large number of ribs on the outer surface of the body of a container is disclosed in JP-A-51-2576. In this method, the temperature of the convex surface of the rib is certainly kept low, and heat is not transmitted to the finger holding the container, so it is easy to hold the container. The heat retention was inferior. Moreover, the ribbed container was excellent in heat insulation, but was inferior in appearance and printability.

[0004] As an alternative to these containers, a density of 0.1 to 0.4 g / cm is obtained by mixing and foaming a particulate material (hereinafter referred to as "expandable particles") which expands by heating.
Containers consisting of ^three paper substrates have been proposed. A container made of a paper base material having such a density has excellent heat insulating properties and cushioning properties, is light in weight, has good workability, and has a flat surface, and thus has good printability. However, when a paper base material having such a density is used, wrinkles tend to be formed in a bent portion during molding, or cracks easily occur, resulting in poor product yield and poor moldability. It has disadvantages and needs to be improved.

[0005]

[0008] The present invention, described above, having a density of conventional 0.1 to 0.4 g / cm ^3, problems of the food container made of paper substrate obtained by foaming a foamable particles It is intended to provide a method of manufacturing a food container having a good product yield without causing wrinkles or cracks in the container at the time of molding.

[0006]

Means for Solving the Problems The present inventors have studied a method of manufacturing a food container using a paper substrate containing expandable particles, and as a result, first produced an unfoamed sheet mixed with expandable particles. In addition, after re-hydrating at the time of molding, it is heated and foamed by hot press, foamed and molded, so that heat is transmitted from both sides of the sheet, it has a good degree of foaming, it has excellent heat insulation and heat retention, and it foams at the time of molding Therefore, they found that a food container without wrinkles and scratches could be manufactured, and completed the present invention.

That is, the method for producing a food container of the present invention comprises:
The paper base containing the fine particles that expands by heating is adjusted to a water content of 30 to 70%, and then heated to 110 to 250 ° C. under a press pressure of 0.05 to 1.0 kgf /
The molding is performed under the condition of cm ² and the density is 0.1 to 0.4 g / c.
It is characterized in that to produce the m ³ container.

Hereinafter, the method of the present invention will be described in detail. As the paper base material used in the present invention, those made of pulp used in ordinary papermaking can be used. For example, wood pulp such as coniferous or hardwood chemical pulp, mechanical pulp, etc.
Waste paper pulp, non-wood natural pulp such as hemp, cotton and the like, synthetic pulp using polyethylene, polypropylene and the like as a raw material, and the like can be used in appropriate combination. In addition to the above pulp, various fibers such as organic fibers such as acrylic fiber, rayon fiber, phenol resin fiber, polyamide fiber and polyester fiber, and inorganic fibers such as glass fiber, carbon fiber and alumina fiber can be mixed. It is. However, considering the papermaking properties of the paper substrate and the flammability at the time of disposal, it is preferable to mix 70% or more of wood pulp with respect to the total weight of the fibers.

[0009] The expandable particles used in the present invention are heat-expandable microcapsules in which a low boiling point solvent is encapsulated in microcapsules. This capsule has an average particle diameter of 5 to 30 μm which expands about 4 to 5 times in diameter and 50 to 100 times in volume by heating for a short time at a relatively low temperature of 80 to 200 ° C.
Particles. These effervescent particles include Matsumoto Microsphere F-3OD, F-30GS, and F-GS.
20D, F-50D, F-80D (Matsumoto Yushi Seiyaku Co., Ltd.), Expancel WU, and Expancel DU (Expensel (Sweden), Nippon Philite) However, the present invention is not limited to these. The blending amount of the expandable particles is preferably 1 to 40%, more preferably 3 to 40% based on the pulp fiber.
20%. If the amount is less than 1%, the foamability is insufficient, and if it exceeds 40%, it is not economically suitable.

In the present invention, various anionic, nonionic, cationic or amphoteric retention improvers, paper strength enhancers, sizing agents, etc., which are conventionally used, are appropriately selected for the paper base material. used.

Specifically, examples of the paper strength enhancer and the retention aid include cationic, nonionic, anionic and amphoteric polyacrylamide resins, polyethyleneimine and its derivatives, polyethylene oxide, polyamine,
Polyamide, polyamide polyamine and derivatives thereof,
Organic compounds such as cationic and amphoteric starch, oxidized starch, carboxymethylated starch, plant gum, polyvinyl alcohol, urea formalin resin, melamine formalin resin, hydrophilic polymer particles, and sulfate band, alumina sol, basic aluminum sulfate, base Aluminum compounds such as basic aluminum chloride and basic polyaluminum hydroxide,
Further, ferrous sulfate, ferric chloride, or an inorganic compound such as colloidal silica or bentonite can be used in appropriate combination.

As the sizing agent, various sizes such as a rosin sizing agent, a petroleum resin sizing agent as an acidic paper sizing agent, an alkyl ketene dimer sizing agent, and an alkenyl succinic anhydride sizing agent as a neutral paper sizing agent. Agents can be mentioned.

The paper substrate of the present invention may also contain fillers generally used in papermaking, such as talc, kaolin, calcined kaolin, clay, diatomaceous earth, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, sulfuric acid. Mineral fillers such as magnesium, silica, aluminosilicate and bentonite, and organic synthetic fillers such as polystyrene particles and urea formalin resin particles can also be appropriately selected and used.

Further, various papermaking aids such as dyes, pH adjusters, slime control agents, defoamers, and tackifiers can be used as appropriate according to the intended use. It is also possible to apply starch, water-soluble polymer substances such as polyvinyl alcohol, various surface sizing agents, pigments and the like to the surface of the paper substrate by a coating method such as a size press or a gate roll.

Using the above-mentioned raw materials, papermaking is carried out by an ordinary papermaking machine to produce a paper substrate. First, after a sheet is formed through a wire part in a paper making process, dehydration is performed by a press part and drying treatment is performed by a dryer part. The dryer temperature at this time needs to be equal to or lower than the foaming start temperature of the foamable particles.
C., preferably around 70 to 85 C. to minimize foaming. The obtained base paper is wound up at a water content of 2 to 50%.

Next, a food container is manufactured using the obtained paper base material. At this time, if the water content of the paper substrate is low,
After the sheet is again hydrated to improve the heat transfer of the sheet, it is formed by a hot press. The water content at this time is preferably 30 to 70%. If the water content of the paper base is less than 30%, foaming is not sufficient, which is inconvenient. If it exceeds 70%, the paper base bursts due to steam pressure during press molding, and a good molded product is obtained. There may not be.

The temperature at the time of hot pressing is preferably 110 to 250 ° C. necessary for the foaming agent to foam sufficiently. Further, the pressure is suitably in the range of 0.05 to 1.0 kgf / cm ² per molding unit area, excluding the pressurizing pressure. If the press pressure is less than 0.05 kgf / cm ² ,
When the heat is not sufficiently transmitted to the sheet, the foaming may be insufficient. When the heat exceeds 1.0 kgf / cm ² , the expanded particles are crushed to exceed the expansion pressure of the expandable particles, and the density is increased. Will be higher.

The molding apparatus includes a press molding machine for electric pressurization, steam pressurization, oil pressurization, and the like, and a single chamfer is preferable.
Any pressure may be used in the initial stage of pressurization, even if the pressure is slightly high, but the pressure will be low at a later time. The pressurization time varies depending on the temperature, but is usually 5 to 60 seconds. Temperature at pressurization is 15
If the temperature is 0 ° C or higher, it will dry excessively when pressed for a long time,
It is necessary to mold in a short time because it may burn. After the molding, if necessary, the molded article can be completely dried by a blow dryer or the like.

[0019] In the present invention, the basis weight of the paper base material containing expandable particles is preferably from 25~400g / m ^2, more preferably from 50 to 300 g / m ^2. If the grammage is less than 25 g / m ² , a food container having sufficient heat insulating properties cannot be obtained. If the grammage exceeds 400 g / m ² , the load of the dryer in the drying step of the paper machine increases, and the drying of the paper base material Becomes insufficient.

The basis weight of the container of the present invention having a density of 0.1 to 0.4 g / cm ³ is preferably 25 to 150 g / m ² for a low-temperature container used for fast food or Chinese steamed bun, while a ramen cup or the like is used. High temperature container used for
It is preferable to use one having 0 to 300 g / m ² . For example, if the surface temperature of the outer layer of the container after 3 minutes is 75 ° C. or less, it is suitable as a high-temperature container. As described above, the density and the basis weight can be appropriately selected and adjusted as needed. Further, the container of the present invention can be used as various trays such as a cushioning tray for fruits and vegetables, a tray for meat, and the like.

The food container of the present invention may be subjected to a water-resistant treatment after the pressure molding, if necessary, by a lamination treatment with a polyethylene resin or the like or a water-repellent treatment with a paraffin wax or the like. The shape of the food container of the present invention is not particularly limited, and may be appropriately molded and processed according to the shape of the food stored therein.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the present invention. In addition, all "%" in an Example shows "weight%."

Example 1 Pulp slurry in which pulp composed of 80% hardwood bleached pulp (LBKP) beaten to a Canadian standard freeness of 450 ml and 20% softwood bleached pulp (NBKP) beaten to a Canadian standard freeness of 470 ml was dispersed. In addition, effervescent microcapsule particles (Matsumoto Yushi Pharmaceutical Co., Ltd.)
Manufactured by Matsumoto Microsphere F-30D, particle size 10
10%, dry paper strength agent (Polystron-117, manufactured by Arakawa Chemical Industries, Ltd.) 0.2%, and cationized starch (CATO-15, manufactured by Oji National Co., Ltd.) 1.0%. , An alkyl ketene dimer-based sizing agent (size span K903, manufactured by Arakawa Chemical Industries, Ltd.)
%, 0.4% wet paper strength enhancer (manufactured by DIC Hercules, Kaimen-557H) was added, and the pulp concentration was 0.03%.
%, PH was adjusted to 7.3 to obtain an inlet raw material. Using the obtained inlet raw material, papermaking is performed using a circular paper machine,
Dry to 10% moisture with a multi-cylinder dryer at 70-75 ° C,
A paper base material having a basis weight of 151 g / m ² and a density of 0.55 g / cm ³ was obtained. Then, off-line, the water content of the paper substrate was adjusted to 55% with a flat bottom tray,
Under a condition of 0 ° C. and a pressure of 0.1 kgf per unit area of molding, the mixture is molded and foamed by a hot press machine, formed into a flat tray of 15 cm long × 9.0 cm × 1.5 cm deep, and then blow-dried. To produce a food container.

Example 2 A paper base material having a basis weight of 320 g / m ² and a density of 0.54 g
Except for using those / cm ³ was prepared food containers in the same manner as in Example 1.

Example 3 Except that the water content of the paper base material offline was 65%.
A food container was produced under the same conditions as in Example 1.

Example 4 A food container was prepared under the same conditions as in Example 1 except that the temperature of the hot press was set to 200 ° C.

Example 5 A food container was produced under the same conditions as in Example 1 except that the pressing pressure of the hot press was changed to 0.08 kgf / cm ² .

Example 6 A food container was produced under the same conditions as in Example 1 except that the pressure of the hot press was changed to 0.4 kgf / cm ² .

Example 7 The press temperature of the hot press was 200 ° C. and the press pressure was 0.7.
A food container was prepared under the same conditions as in Example 1 except that the weight was changed to ² kgf / cm ² .

Comparative Example 1 Except that the water content of the paper base material off-line was 20%
A food container was produced under the same conditions as in Example 1.

COMPARATIVE EXAMPLE 2 Except that the water content of the paper base material off-line was changed to 72%,
A food container was produced under the same conditions as in Example 1.

Comparative Example 3 A food container was produced under the same conditions as in Example 1 except that the pressing pressure of the hot press was 1.3 kgf / cm ² .

The thickness and density of the food containers obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were measured, and the moldability and heat insulation were evaluated. Table 1 shows the results. In addition, about the moldability, it evaluated by the presence or absence of the wrinkle of the bending part of a container. Also,
The heat insulation was evaluated by measuring the thermal diffusivity and calculating the thermal conductivity in the following manner. The value of thermal conductivity is 7.0 × 10 ^-2
If it is less than w / m / k, the heat insulating property is at a practical level. Measurement method: The thermal diffusivity was measured by a laser flash method, and the thermal conductivity (λ) was calculated by the following equation. In addition,
The measurement was performed using LF / TCM (FA8510B manufactured by Rigaku Denki).
Type) The measurement was performed using a measuring machine. λ = α · Cp · ρ λ; Thermal conductivity (w / m / k) α; Thermal diffusivity (cm ² / sec) Cp: Heat capacity (J / g · ° C.), calculated with 1.34 for paper ρ; density (g / cm ³ )

[0034]

[Table 1]

As is clear from Table 1, food containers having good foaming properties were produced from the paper substrates of the present invention of Examples 1 to 4 by hot press foaming. Moreover, the obtained food container has good moldability and good heat insulation.

[0036]

The food container produced by the method of the present invention comprises:
Because of the large number of closed cells made of expandable particles, it has good heat insulation and heat retention properties, is lightweight and has good moldability, and as a paper container, an epoch-making thing is obtained, and it has good appearance, It is extremely useful in practice.

Claims (1)

(57) [Claims] 1. A paper substrate containing fine particles which expands upon heating is adjusted to a water content of 30 to 70%, and then heated to a temperature of 110 to 250 ° C. under a press pressure of 0.05%.
Molding is performed under the condition of 1.0 to 1.0 kgf / cm ² , and the density is 0.
A method for producing a food container, comprising producing a 1 to 0.4 g / cm ³ container.