JPH0333591B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat-resistant paper container, and more specifically, the present invention relates to a heat-resistant paper container, and more specifically, it can be heated in an oven, microwave, toaster oven, etc. The present invention relates to a heat-resistant container capable of

Prior Art and Technical Problems of the Invention Tray-shaped paper containers are used as containers that can be easily filled with food and other contents, but in recent years, with the spread of ovens, microwave ovens, toaster ovens, etc. It is desired to develop a container that can be sold by filling tray-shaped containers with cooked or uncooked foods, and that can be heated or cooked by placing the container in the above-mentioned heater at the time of eating. Although paper containers are inexpensive, they have poor heat resistance, easily ignite or carbonize, and even if they do not, their strength significantly decreases when heated.

This tray-shaped container is made of paper and polyethylene terephthalate or poly-4-methylpentene.
It is already known that a laminate made of a first grade film is formed into a tray shape, but since the temperature reached to about 300°C in the above-mentioned toaster oven etc., the resin film melts and the container is heated. This role is not fully fulfilled.

OBJECT OF THE INVENTION Accordingly, an object of the present invention is to provide a heat-resistant paper container that eliminates the drawbacks of the conventional paper containers described above.

Another object of the present invention is to provide a heat-resistant paper container that can be filled with contents and placed in a heater such as an oven, a microwave oven, or a toaster oven for heating or cooking. It is on offer.

Still another object of the present invention is to provide a heat-resistant paper container that stably maintains a predetermined container shape and required strength not only before heating but also after heating to a high temperature.

Composition of the Invention According to the present invention, there is provided a paper substrate made of long-fiber pulp with an elongation of 1.8% or more in the longitudinal and lateral directions, and pulp fibers and inorganic fibers provided on both sides of the paper substrate with an adhesive layer interposed therebetween. Provided is a heat-resistant paper container comprising a press-molded body of a laminate of at least one of the above and a heat-resistant synthetic paper containing an inorganic flame retardant and filler.

Effect The present invention provides a paper substrate made of long-fiber pulp with an elongation of 1.8% or more in the longitudinal and transverse directions, and at least one layer of pulp fibers and inorganic fibers on both sides of the paper substrate.
When heat-resistant synthetic paper containing seeds and a flame retardant/filler is laminated together with an adhesive to form a laminate, it becomes possible to press-form it into a tray or cup without causing any breakage. This is based on the knowledge that a predetermined container shape and necessary strength are stably maintained even when heated at high temperatures in a heater.

Synthetic paper containing pulp fibers, inorganic fibers, and flame retardants is known as so-called flame-retardant paper or non-combustible paper, but this paper has extremely low elongation and is difficult to use for containers. However, if it is press-molded into a shape such as a tray, it has the disadvantage that it will break during molding. According to the present invention, by making this synthetic paper-made paper with high elongation into a structure in which the paper substrate is sandwiched with synthetic paper, it is possible to press-form it into a container shape, and even after heating, it is possible to The shape and strength of the container can be obtained.

Press forming is performed by causing plastic flow in the sheet between a male mold called a punch and a female mold called a die, but in this case, stress is concentrated in a part of the sheet, and in the synthetic paper making process, this stress This causes rupture. The paper substrate used in the present invention effectively acts as a stress carrier during this molding. Furthermore, when the cross section of the laminate used in the present invention was observed after heating, it was found that the central paper substrate was carbonized. From this, it can be understood that the shape retention and mechanical strength of the container after heating are due to the synthetic paper that exists on both sides of the paper substrate.

Furthermore, even after being heated in an oven, etc., flame-retardant or non-combustible synthetic paper is present on both sides of the paper substrate, so the carbonized layer is hidden by these synthetic papers, resulting in good appearance characteristics and commercial value. is maintained.

Preferred Embodiment of the Invention In FIG. 1 showing the cross-sectional structure of a laminate used in the present invention, adhesive layers 2 and 3 are provided on both surfaces of a paper substrate 1.
Synthetic paper sheets 4 and 5 are bonded together via the .

In FIG. 2, which shows an example of the container of the present invention, this container consists of a flat bottom 6, a body 7 seamlessly connected to the bottom, and a flat flange 8 connected to the upper end of the body.

The paper substrate 1 must have a longitudinal and axial elongation of at least 1.8% to enable press forming of the laminate. Such paper can be obtained by manufacturing paper by increasing the amount of long-fiber pulp, such as softwood pulp, among various pulps. The basis weight of the paper substrate is generally 100 to 500 g/m ² , especially 150 g/m 2
It is desirable that the amount is in the range of 350 g/m ² to 350 g/m 2 .

As the heat-resistant synthetic paper 4, 5, one containing at least one of pulp fibers and inorganic fibers and an inorganic flame retardant/filler is used. Pulp fibers and inorganic fibers provide paper-making properties,
Furthermore, the pulp fibers provide the synthetic paper with the elongation necessary for molding, while the inorganic fibers increase the strength and heat resistance. The inorganic flame retardant/filler performs the functions described below. As the inorganic fiber, glass fiber, rock wool, slag wool, asbestos, ceramic fiber, etc. are used, and glass fiber is preferred. Aluminum hydroxide is most suitable as a flame retardant and filler, but magnesium hydroxide, calcium aluminate, dosonai, etc. are also used. These flame retardants and fillers contain water of crystallization and impart flame retardancy by releasing crystal water near the combustion start temperature of paper, etc., and also improve the texture necessary for paper making due to their effect as fillers. It is something that is given. Of course, in the present invention, inorganic fillers that do not themselves have flame retardant properties, such as silica,
There is no problem in using talc, clay, calcium carbonate, etc. in combination.

An inorganic binder, an organic resin binder, or the like may be added in order to improve paper formability or to bond or fix fibers to each other. Furthermore, an inorganic or organic sizing agent may be included for the purpose of adjusting (reducing) the water permeability of the synthetic paper.

In the present invention, the inorganic fiber is 0 per synthetic paper making.
It is desirable that the content is 50 to 50% by weight, especially 5 to 30% by weight, while the flame retardant/filler is 10 to 60% by weight.
The content is preferably 20 to 50% by weight, particularly 20 to 50% by weight.

Suitable examples of synthetic papermaking compositions include, but are not limited to, the following:

Inorganic fiber 0 to 50% Flame retardant and filler 10 to 60% Pulp fiber 10 to 60% Organic resin binder 0 to 10% Sizing agent 0 to 5% The above-mentioned papermaking composition is charged into a beating machine, and the resulting aqueous The dispersion is made into paper using a known paper machine or the like. The basis weight of synthetic paper is 50 to 300
g/m ² , preferably in the range of 100 to 200 g/m ² .

The synthetic papers on both sides of the paper substrate may be the same or different. for example,
The synthetic paper that forms the inner surface of the container can be provided with a coating layer or an impregnated layer to prevent liquid from permeating. Such a layer may be made of a heat-resistant resin such as polyimide, polyimide imidasopyrrolone, wholly aromatic polyamide, wholly aromatic polyester, epoxy
It may be a coating layer of paint such as phenolic resin or a film layer. It may also be a water-repellent layer made of organosiloxanes, organic titanates, or the like.

Furthermore, it may be an inorganic coating layer made of silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, etc., or a combination thereof.

Adhesives for bonding the paper substrate and synthetic paper include urethane adhesives, epoxy adhesives, emulsion adhesives such as vinyl acetate resin, acrylic resin, vinyl chloride resin, synthetic rubber, etc.
Water-soluble sizing agents such as polyvinyl alcohol, carboxymethyl cellulose, ethyl cellulose, and starch can be used.

The laminate can be easily formed into a container by a press molding method known per se, for example, using a combination of a punch and a die. According to the present invention, by using the above-mentioned laminate, it is a remarkable advantage that press molding from shallowly drawn trays to deeply drawn cup-shaped containers can be easily performed.

The invention is illustrated by the following example.

Example 1 Composition with elongation length: 3.0%, width: 7.0%, basis weight: 220 g/m ² , fibers elongate on both sides of a paper substrate consisting only of wood pulp: length: 1.4%, width: 1.4%, basis weight: 120 g/m ² However, noncombustible paper containing 10% glass fiber, 48% wood pulp fiber, 40% aluminum hydroxide, and 2% binder was laminated using a styrene-acrylic copolymer adhesive.

The thus obtained laminate was press-formed vertically.
A square tray measuring 18 cm, width 10 cm, and depth 2 cm was molded. Three skewers of salted yakitori that had been stored in the refrigerator were placed in this square tray and heated in a gas oven over medium heat for 6 minutes. When the yakitori was removed from the oven after heating, it was found to be at an appropriate temperature and delicious. At this time, the surface of the square tray was not burnt and no discoloration was observed. Furthermore, the surface temperature of the square tray during heating was measured and found to be 250°C.

Example 2 A 10 μm thick polyimide film was laminated on one surface of the three-layer laminate of noncombustible paper/paper substrate/noncombustible paper of Example 1 using a urethane adhesive. A square tray of the same size as in Example 1 was molded from the obtained four-layer laminate by press molding so that the polyimide film was on the inner surface. This rectangular tray was stored in the refrigerator, and three skewers of yakitori with hot sauce were put there together with the sauce, and the mixture was placed in a toaster oven and heated for 4 minutes. When the yakitori was removed from the oven after heating, it was found to be at an appropriate temperature and delicious. At this time, no discoloration of the surface of the square tray was observed. Furthermore, during heating, the surface temperature of the square tray was measured and found to be 270°C.

Example 3 Instead of the three-layer laminate in Example 1,
When a similar test was conducted using a 4-layer laminate coated with a 20μ polyethylene terephthalate film, no discoloration was observed on the surface of the square tray.

Example 4 The inner surface of the square tray obtained in Example 1 was coated with a coating agent based on silicon oxide and titanium oxide by spraying. Macaroni gratin was placed in this square tray and heated in a gas oven over medium heat for 10 minutes. After the heating was completed, the tray was removed from the oven and the macaroni gratin was tasted.The center of the macaroni gratin was sufficiently heated and was delicious. Further, at this time, no discoloration on the surface of the square tray was observed.

On the other hand, when the same square tray containing macaroni gratin was placed in a microwave oven and heated, the heating finished in 5 minutes. As described above, this rectangular container had good microwave transmission and could be heated efficiently in a microwave oven.

Comparative Example 1 Same composition as the paper used as the substrate of the laminate instead of the three-layer laminate in Example 1, but with a basis weight of 400 g/m ²
When a similar test was conducted using a low-grade monomer, the surface of the square tray turned brown after heating. In addition, a decrease in paper strength was observed, and the wall surface of the square tray easily broke when force was applied by hand.

Example 5 A composition with an elongation of 3.5% in length, 7.5% in width, and a basis weight of 250 g/ ^m2 , and a paper substrate consisting of only wood pulp as fibers, with an elongation of 1.2%, 1.2% in width, and a basis weight of 100g/ ^m2. Noncombustible paper containing 50% glass fiber, 32% aluminum hydroxide, 15% colloidal silica, and 3% organic binder was laminated using a styrene-acrylic copolymer adhesive.

The thus obtained laminate was press-molded into a round tray with a diameter of 15 cm and a depth of 2 cm.

Next, the inner surface of this round tray was coated with a silicon oxide film by ion plating.

This round tray was filled with beef stew and heated in a gas oven over medium heat for 10 minutes. When the beef stew was removed from the oven after heating, it was at an appropriate temperature and delicious. At this time, the surface of the round tray was not burnt and no discoloration was observed.

Example 6 When the same test as in Example 3 was conducted using a noncombustible paper with a composition of 58% wood pulp fiber, 40% aluminum hydroxide, and 2% binder, it was found that the surface of the square tray No discoloration was observed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a laminate used in the present invention, and FIG. 2 is a sectional view of an example of a container of the present invention, in which reference numeral 1 is a paper substrate, 2 and 3 are adhesive layers,
4 and 5 are synthetic papers, 6 is a flat bottom of the container, 7 is a body, and 8 is a flat flange.

Claims (1)

[Claims] 1 Longitudinal and transverse elongation made of long fiber pulp
A heat-resistant synthetic paper containing a paper substrate of 1.8% or more, at least one of pulp fibers and inorganic fibers, and an inorganic flame retardant and filler provided on both sides of the paper substrate via an adhesive layer. A heat-resistant paper container characterized by comprising a press-formed body of a laminate.