JP2014159134A - Heat-resistant food container and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant food container which can be inexpensively manufactured by using general polyethylene terephthalate (PET) resins low in cost or PET resins for fibers or recycled PET flakes even lower in cost and which has a high heat resistance of tolerating up to 250°C.SOLUTION: After a chain extender and talc have been added to a PET resin, the obtained admixture is charged into an extruder 30 having two or more vent holes, and after the PET resin has been suctioned and degassed, in a state of being heated and melted, through vent holes 33 and 34 in a high vacuum of -99.99 kPa or above, a sheet is formed therefrom by extrusion molding. The sheet is vacuum/compressed air-formed by a thermal molding machine and retained within a molding mold at 100 to 220°C so as to form a container. The combined sum of the crystalline portion of the container expressed by the following formula and the content of the talc is 25% or higher: crystalline portion (%)=(per-mole melting caloric value-per-mole cold crystallization caloric value)/per-mole melting caloric value of totally crystallized PET (26.9 KJ)×100.

Description

  The present invention relates to a heat-resistant food container, and more particularly to a heat-resistant food container that can withstand a cooking temperature of 180 to 250 ° C., which is a temperature cooked in a microwave oven.

  In food stores such as convenience stores, department stores and supermarkets, food containers such as trays, cups and bowls are packed with various foods such as side dishes, fried foods, noodles and salads. The heat resistance required for these food containers is the temperature that can withstand microwave heating of foods with low oil content (90 ° C), the temperature that can withstand microwave heating of foods with high oil content (150 ° C), gratin, and doria The heat resistance up to the temperature (180 to 250 ° C.) for scoring such as the like is required. As a food container having heat resistance up to 90 to 150 ° C., a PP layer containing four layers of A, B, C and D from the inside and containing 20 to 60% by weight of inorganic filler in the outermost layer D is used. Molding a resin composition comprising a container (see Patent Document 1) using heat resistance and a mixture of 40 to 80% by weight of a PP resin and PE resin of 10% by weight or more and 20 to 60% by weight of talc. A processing technique (see Patent Document 2) has been proposed. However, the containers molded by these techniques are mainly made of PP resin, and the melting point of PP resin is 160 ° C inside or outside, so it is used for containers with heat resistance up to 250 ° C corresponding to gratin etc. It was impossible.

Generally as a container which has heat resistance to 180-250 degreeC, the shaping | molding container using C-PET resin (crystallization accelerator addition) is used.
Repeating unit

よりなり光学的に異方性の溶融相を形成する全芳香族ポリエステル１００重量部に対して、２５〜５００重量部の無機化合物を充填してなる混合物から成形され、−４０〜２５０℃まで対応できるオーブン容器が提案されている（特許文献３参照）。

It is molded from a mixture of 25 to 500 parts by weight of an inorganic compound with respect to 100 parts by weight of a wholly aromatic polyester that forms an optically anisotropic melt phase, and can handle up to -40 to 250 ° C. An oven container has been proposed (see Patent Document 3).

  In addition, although the method of manufacturing the sheet | seat for food containers using undried collection | recovery PET flakes etc. is proposed (refer patent document 4), this sheet | seat for food containers has no heat resistance.

JP-A-9-11419 JP-A-2-68015 JP-A-1-171515 JP11-184580

  However, the container molded using the C-PET resin is expensive because the C-PET resin itself is expensive. Moreover, the container shape | molded using the said fully aromatic polyester had to synthesize | combine a wholly aromatic polyester resin newly, and became expensive. As described above, conventionally, only expensive food containers have heat resistance up to 250 ° C. and can withstand cooking by a microwave oven.

  The present invention solves the above-mentioned problems, and can be manufactured at low cost by using a general PET resin with a low cost, a PET resin for fibers and a recovered PET flake with a low cost, and has a high heat resistance up to 250 ° C. The food container which has property is provided.

  As a result of diligent research, the present inventors have mixed talc with a chain extender that binds the end of the PET resin chain to a general PET resin with low cost, a PET resin for fibers, recovered PET flakes, and the like. This mixed resin is put into an extruder having a vent hole, and is heated and melted without suction and degassing at a high vacuum of −99.99 kPa or more from the vent hole to dry the raw PET resin, After the molecular weight is increased with a chain extender, the extruded sheet is molded by a thermoforming machine, and is kept at 100 to 220 ° C. in a molding die to crystallize the PET resin. It has been found that if the content is 25% or more, heat resistance of 180 to 250 ° C. of the microwave oven can be imparted, and the present invention has been completed.

  In the heat-resistant food container according to claim 1, a chain extender and talc are added to PET resin, and the vent hole is put into an extruder having two or more, and -99.99 kPa from the vent hole in a state where the PET resin is heated and melted. After sucking and degassing under the above high vacuum, a sheet is formed by extrusion molding, the sheet is vacuum-compressed with a thermoforming machine, and held at 100 to 220 ° C. in a molding die to form a container The total amount of the crystal portion and the talc content represented by the following formula of the container is 25% or more.

  The heat-resistant food container according to claim 2 is characterized in that the chain extender is a styrene / acryl oligomer having 4 or more epoxy groups, and the amount of the talc added is 2 to 15%.

  The heat-resistant food container according to claim 3 is provided with an inner layer made of a PET resin layer, and the interior is formed by a coextrusion method.

  The heat-resistant food container according to claim 4 is provided with an outer layer made of a printing film obtained by gravure printing on an A-PET film or a film obtained by stretching an A-PET film 1.5 to 2.5 times in the MD direction, The outer layer is formed by heat bonding.

  The method for producing a heat-resistant food container according to claim 5 comprises adding a chain extender having 4 or more epoxy groups and 2 to 15% by weight of talc to a PET resin as a main layer, and a main extrusion having 2 or more vent holes. The PET resin as the inner layer is put into a sub-extrusion machine with one or more vent holes, and the PET resin is heated and melted and sucked from the vent holes under a high vacuum of -99.99 kPa or more. -After degassing, a main layer and an inner layer are formed by a coextrusion method, and A-PET film or A-PET film is gravure-stretched in the MD direction 1.5 to 2.5 times in the main layer. The outer layer composed of the printed printing film is laminated by heat bonding, and the laminated sheet composed of the inner layer, the main layer and the outer layer is formed by vacuum and pressure forming with a thermoforming machine, and the temperature is set to 100 ° C. to 220 ° C. in the molding die. Configured to hold There.

  The heat-resistant food container according to claim 1 is formed of a resin composition obtained by adding a chain extender and talc to PET resin. By adding a chain extender to the PET resin, the end of the low molecular weight PET molecule can be linked and modified to a high molecular weight PET resin with a three-dimensional structure. As a result, PET resin for fibers and recovered PET can be obtained. Even a resin such as flakes having a low melt tension that cannot be extruded can increase the melt tension and can be extruded. Moreover, the heat resistance of a container can be improved by adding talc.

  After the resin composition composed of the above PET resin is put into an extruder having two or more vent holes, and the PET resin is heated and melted, it is sucked and degassed from the vent hole under a high vacuum of -99.99 kPa or more. Since the sheet is formed by extrusion, the PET resin can be used without drying, and the manufacturing cost can be reduced. In particular, even recovered PET flakes can be used without passing through the drying step. Therefore, it can be manufactured at low cost.

  Furthermore, since the sheet | seat formed by extrusion molding is vacuum-pressurized with a thermoforming machine, and it hold | maintains at 100-220 degreeC in a shaping | molding metal mold | die, crystallinity can be raised. And since the total amount of the crystal | crystallization part and content of talc is 25 weight% or more, it will have heat resistance to 250 degreeC, and the heating which burns the gratin etc. in a microwave oven will be attained.

  In the heat-resistant food container according to claim 2, since the chain extender has four or more epoxy groups, the end of the PET molecule can be bound to the epoxy group, and the high molecular weight PET resin having a three-dimensional structure. Can be efficiently modified. In addition, since the amount of talc added is 2 to 15% by weight, the heat resistance itself can be surely improved and crystallization can be promoted by becoming a crystal nucleating agent for PET. Crystallization can be promoted.

  In the heat-resistant food container according to claim 3, an inner layer made of a PET resin layer is provided, and this inner layer is formed by a coextrusion method. Therefore, the main layer (formed by the resin composition according to claims 1 and 2). Even when recovered PET flakes or the like are used as the raw material of the layer, by forming the inner layer with virgin PET resin, high safety and hygiene can be secured, and it can be used as a food container without any problem.

  In the heat-resistant food container according to claim 4, an outer layer made of a printing film obtained by gravure printing on a film obtained by stretching A-PET film or A-PET film 1.5 to 2.5 times in the MD direction is provided, Since this exterior is formed by heat bonding, cosmetics can be imparted to the appearance of the container.

  In the method for producing a heat-resistant food container according to claim 5, a chain extender having 4 or more epoxy groups and 2 to 15% by weight of talc are added to a PET resin as a main layer, and a main hole having 2 or more vent holes. While being put into the extruder, the PET resin as the inner layer is put into a sub-extruder having one or more vent holes, and each PET resin is heated and melted under a high vacuum of -99.99 kPa or more from the vent holes. After sucking and degassing, a main layer and an inner layer are formed by a co-extrusion method. A-PET film or A-PET film is stretched 1.5 to 2.5 times in the MD direction on the main layer. An outer layer made of a printing film subjected to gravure printing is laminated by heat bonding, and a laminated sheet consisting of the inner layer, the main layer and the outer layer is formed by vacuum and pressure formation with a thermoforming machine, and 100 to 220 ° C. in a molding die. To maintain the above-mentioned resistance. The food container can be easily manufactured, a result, it is possible to inexpensively manufacture the excellent heat food containers in heat resistance, safety and health properties and beautification of up to 250 ° C..

Schematic of the manufacturing equipment for heat-resistant food container sheets, Schematic diagram of the cylinder part of an extruder used in heat-resistant food container sheet manufacturing equipment Schematic diagram of laminated sheet heating section It is a schematic diagram of a thermoforming machine. Figure showing the effect of talc on the crystallization rate of PET

  In the heat-resistant food container of the present invention, first, a PET resin material is prepared by adding and mixing a chain extender and talc to a PET resin. The PET resin is not particularly limited, such as virgin PET resin, PET resin for fibers, and recovered PET flakes. However, it is preferable to use PET resin for fibers and recovered PET flakes because it can be manufactured at a lower cost.

  The chain extender binds the end of a low molecular weight PET molecule and is modified to a high molecular weight PET resin having a three-dimensional structure. The chain extender preferably has four or more epoxy groups in one molecule, and the reactivity increases as the number of epoxy groups increases. Examples of such chain extenders include highly reactive styrene / acryl oligomers (Mn = 3,000) having 9 to 10 epoxy groups in one molecule, specifically ternary styrene- (meta ) "ADR4368S" (BASF Japan Ltd.), which is methyl acrylate-glycidyl methacrylate.

  The addition amount of the chain extender may be determined according to the addition amount specified by each company depending on the performance of the chain extender sold. In the case of the “ADR4368S”, it is 0.5% by weight or less based on the PET resin. . When the addition amount is small, a master batch (hereinafter referred to as “MB”) kneaded with PETG resin at 20 to 40% by weight may be prepared and added as MB.

  Talc improves heat resistance and serves as a nucleating agent for crystallization to increase the crystallization speed, and improves heat resistance up to 250 ° C. in combination with the crystallization portion of the PET resin.

  FIG. 5 shows the crystallization speed of PET when 0.5% of talc is added, and the horizontal axis represents the crystallization temperature and the vertical axis represents the half crystallization time. From this figure, PET added with 0.5% talc has a crystallization speed that is about 1.5 times faster even in the range of 150 to 160 ° C., which is the closest to pure PET, and at temperatures below 150 ° C. Further, the difference is greatly widened, and crystallization can be promoted to a lower temperature side than pure PET.

  In general, there are few examples that report the mechanism of action of the added nucleating agent, and the theory that PET is adsorbed on the nucleating agent and the trans-conformation of the molecular chain increases, There is a chemical nucleation theory by reaction.

  In addition to acting as a nucleating agent, talc also plays a role in improving heat resistance and rigidity. That is, PET consists of a non-crystalline part and a crystalline part. At temperatures above the glass dislocation point (inside and outside of 70 ° C.), the non-crystalline part becomes gradually softer as the temperature rises, and the holding power against deformation becomes weak. On the other hand, the crystal portion is solid until it melts at the melting point temperature (260 ° C. in PET), and the holding power against deformation does not become weak. Talc is also an inorganic substance and is solid even at 260 ° C. Accordingly, the heat resistance is improved by the combined action of PET crystals. The improvement in heat resistance is that there is a solid PET crystal part and talc island in the sea of the amorphous part of PET, the temperature rises beyond the glass transition point of PET, and the amorphous part becomes soft and deforms. However, if there are many crystal parts and solid parts of talc, the distance between the solids is close, so even if the amorphous part is soft and tries to deform, the solid does not deform, so it can withstand deformation It is done.

  Finally, the total amount of the crystal portion and the talc content represented by the following formula of the container is set to 25% or more. When the total amount is 25% or more, heat resistance up to 250 ° C. can be secured.

タルクの平均粒径は、２０μｍ以下が好ましく、１０μｍ以下がより好ましい。平均粒径が２０μｍを超えると、分散が悪くなり、また同じ添加量でも核剤としての数が少なくなる。

The average particle size of talc is preferably 20 μm or less, and more preferably 10 μm or less. When the average particle size exceeds 20 μm, the dispersion becomes worse, and the number as the nucleating agent decreases even with the same addition amount.

  Since talc is in the form of powder, handling is troublesome, and since it becomes lumpy in PET resin and difficult to disperse uniformly, it is preferably added as MB of PET resin. As MB of talc, a high concentration of talc mixed with 50 to 80% by weight is preferable.

  The PET resin material uniformly dispersed and mixed as described above is put into an extruder having two or more vent holes, and sucked under a high vacuum of -99.99 kPa or more from the vent holes with the PET resin heated and melted. -After deaeration, a sheet is formed by extrusion.

  Thus, by extruding after deaeration in an extruder, a sheet can be formed without going through a drying step, so that the cost can be reduced. That is, in general, when a PET resin is extruded by an extruder, if the PET resin contains water, it will be hydrolyzed and deteriorated, so it is usually necessary to dry it to 50 ppm or less. Drying is performed at a temperature of 120 to 140 ° C., and depending on the water content, several hours in the case of virgin PET resin, 10 hours in the case of recovered PET flakes, enormous energy costs and high costs It is. Therefore, since non-drying PET resin, recovered PET flakes, and the like can be used as they are without passing through the drying process, the cost required for the drying process can be reduced.

  Next, the sheet is subjected to vacuum / pressure forming with a thermoforming machine, and held at 100 to 220 ° C. in a molding die to form a container. That is, the temperature of the sheet is heated to 80 to 130 ° C., and formed into a container by vacuum or vacuum / pressure forming with a thermoforming machine, and 100 to 220 ° C., preferably 3 to 100 to 200 ° C. in the same molding die. Hold for 10 seconds and remove from mold. The molding die may be a normal female die and a die formed by plug assist, or a so-called match mold die in which a female die and a male die are similar. In the case of a match mold, if one of the female mold and the male mold is a heating mold, and the other mold is a cooling mold, the PET crystal is first formed with the heating mold. The time until the container can be taken out can be shortened by accelerating the process and then cooling with a cooling mold.

  For example, when the male mold is a heating mold, the vacuum port of the male mold is evacuated and the compressed air is blown out from the female mold of the cooling mold to mold the container. Then, the molded container is brought into close contact with the male mold and heated and held at a temperature of 100 to 220 ° C. for a predetermined time to promote crystallization. Next, the compressed air is blown out from the vacuum port of the male mold and the vacuum port of the female mold is evacuated to press the container against the female mold and cool.

  When the female mold is a heating mold, the vacuum port of the female mold is evacuated and the compressed air is blown out from the vacuum port of the male mold to mold the container. And the shape | molded container is closely_contact | adhered and it heats and hold | maintains to 100-220 degreeC for predetermined time, and accelerates | stimulates crystallization. Next, the vacuum port of the male mold is evacuated and the compressed air is blown out from the vacuum port of the female mold to cool the container against the male mold.

  As described above, the crystal portion of the container is set to 25% or more in total amount with talc by being held at 100 to 220 ° C. in the molding die.

  Further, a container may be formed only with a PET resin layer obtained by adding a chain extender and talc to a PET resin, but this PET resin layer may be used as a main layer and a virgin PET resin layer may be formed as an inner layer inside the PET resin layer. Good. By forming the inner layer, extremely high hygiene can be ensured even if the PET resin used for the main layer is a recovered flake. In order to form the inner layer, it can be formed simultaneously with the formation of the main layer by a coextrusion method. Also, the inner layer can be manufactured at low cost by omitting the drying step by extruding undried PET resin using a sub-extruder having one or more vent holes and sucking and degassing from the vent holes. . The thickness of the inner layer is preferably 25 μm or more.

  Furthermore, a printing film in which gravure printing is applied to a PET resin layer obtained by adding a chain extender and talc to a PET resin, and A-PET film or A-PET film stretched 1.5 to 2.5 times in the MD direction. May be formed as an outer layer. By forming the outer layer, the cosmetic properties of the container surface can be improved. In order to form the outer layer, the PET resin layer can be formed by extruding and simultaneously laminating by heat bonding.

  Next, the manufacturing apparatus of the sheet | seat for heat-resistant food containers by this invention is demonstrated.

  FIG. 1 is a schematic view of a heat-resistant food container sheet manufacturing apparatus, FIG. 2 is a schematic view of a cylinder portion of an extruder used in a heat-resistant food container sheet manufacturing apparatus, and FIG. 3 is a schematic view of a heating section of a laminated sheet. 4 is a schematic view of a thermoforming machine.

  In FIG. 1, 10 is a quantitative feeder, 20 is a mixer, 30 is a main extruder, 40 is a sub-extruder, 50 is a feed block, 60 is a T die, 70 is a cooling roll, 80 is a printing film feed roll, 90 is It is a winding roll. The quantitative feeder 10 includes a PET resin feeder 11, a chain extender feeder 12, a talc feeder 13, and a pigment feeder 14, and a predetermined amount of each is fed into the mixer 20. The mixer 20 is composed of a main body 21 and a rotary valve 22 provided at the lower end, and the PET resin material is adjusted by uniformly mixing the materials introduced from the quantitative feeders 11, 12, 13, and 14 in the main body 21. At the same time, a predetermined amount is supplied from the rotary valve 22 to the main extruder 30. In the main extruder 30, the injected PET resin material is extruded after being sucked and degassed from a vent hole under a high vacuum of −99.99 kPa or more in a heated and melted state.

A schematic diagram of the cylinder portion of the main extruder 30 is shown in FIG. In FIG. 2, reference numeral 31 denotes a cylinder. A screw 32 is provided inside the cylinder 31, and a first vent hole 33 and a second vent hole 34 are formed from the base end side (resin charging side). In the screw 32, the pressure compression unit 35 and the seal unit 36 are alternately arranged. In the seal unit 36, the groove width of the screw is narrowed, and the space between them is filled with molten PET resin, and the pressure compression unit 35. The pressure difference between the high pressure of 9807 to 19613 kPa (100 to 200 kg / cm ² ) and the high vacuum of −99.99 kPa in the vent holes 33 and 34 is sealed, and the resin is pushed only by the rotation of the screw 32. As it advances, the molten PET resin is prevented from blowing up from the vent holes 33 and 34.

  The vent holes 33 and 34 are connected to an oil rotary vacuum pump via a condenser (condenser), and the condenser is used to maintain the degree of vacuum and the oil quality of the oil rotary vacuum pump. Is. Without a condenser, for example, if a PET resin with a water content of 3,000 ppm is operated at a discharge rate of 500 kg / hr, 500,000 g × 0.3 / 100 = 1,500 g / hr of water vapor is generated and high. The vacuum cannot be maintained, and the oil in the oil rotary vacuum pump is also altered by water.

In the extruder as described above, in order to melt and extrude the PET resin, the PET resin is put into the cylinder 31, the extrusion temperature is 280 ° C., the back pressure is 9807 to 19613 kPa (100 to 200 kg / cm ² ), and the vent hole 33. , 34 to −99.99 kPa or higher and extruding while sucking and degassing.

  In the first zone, the charged PET resin is first kneaded with MB of chain extender and MB of talc added by heating and melting. It is considered that melted PET is depolymerized by hydrolysis and thermal decomposition with water and heat, and low molecular weight PET chains, ethylene glycol, and acetaldehyde are generated. However, since a chain extender is added and kneaded, it is considered that a polymerization reaction such as three-dimensional high molecular weight and capture of ethylene glycol or acetaldehyde has started to occur by linking low molecular weight PET chains. Ie epoxy group

は開裂して、カルボキシル基（−ＣＯＯＨ）、アルデヒド基（−ＣＨＯ）、水酸基（−ＯＨ）等の官能基と結び付き、ＰＥＴ分子鎖を３次元の網目構造の高分子にするとともに、解重合で生じたエチレングリコール、エチレングリコールから発生するアセトアルデヒドをも高分子の一部として捕捉する。又、含有している水分は、２８０℃における飽和水蒸気圧は６３７４ｋＰａ（６５ｋｇ／ｃｍ^２）であるので、背圧９８０６ｋＰａ（１００ｋｇ／ｃｍ^２）以上では液体の状態である。

Is cleaved and combined with a functional group such as a carboxyl group (—COOH), an aldehyde group (—CHO), a hydroxyl group (—OH), etc., and the PET molecular chain is converted into a polymer having a three-dimensional network structure. The generated ethylene glycol and acetaldehyde generated from ethylene glycol are also captured as part of the polymer. In addition, since the saturated water vapor pressure at 280 ° C. is 6374 kPa (65 kg / cm ² ), the contained water is in a liquid state at a back pressure of 9806 kPa (100 kg / cm ² ) or more.

  And when the molten PET resin containing ethylene glycol, acetaldehyde, and water comes to the first vent hole 33, it is under a high vacuum of -99.99 kPa or more, so ethylene glycol (boiling point 198 ° C.), acetaldehyde ( Water (boiling point 20 ° C.) and water (boiling point 100 ° C.) become gas and are sucked and degassed from the first vent hole 3. Then, ethylene glycol, acetaldehyde and water that have not been completely sucked and degassed from the first vent hole 33 are sucked and degassed by the second vent hole 34. In the second zone, it is considered that a part of the depolymerization has occurred, but most of the polymerization reaction by the chain extender is considered to have occurred.

  In the third zone, almost only the polymerization reaction with the chain extender has occurred, so acetaldehyde is not newly generated, and the molten PET resin is extruded without any residual acetaldehyde.

  In this way, since it can be modified to a three-dimensional high molecular weight by polymerization reaction, not only PET resin used in bottles and containers but also low-cost PET resin and recovered PET flakes are modified. It can be usefully used.

  The sub-extruder 40 is also similar to the main extruder 30 in the cylinder 41, screw 42, first vent hole 43, second vent hole 44, pressure compression section (not shown), and seal section (not shown). The water is removed from the input PET resin in substantially the same process.

  The extrusion ports 37 and 45 of the main extruder 30 and the sub-extruder 40 are connected to the T die 60 via the feed block 50, and the PET resin supplied from the main extruder 30 by the T die 60 The laminated sheet a composed of the main layer and the inner layer is formed by co-extrusion with the virgin PET resin supplied from the sub-extruder 40. At this time, the printing film b is fed from the printing film feeding roll 80, and is superposed on the main layer of the laminated sheet a in the cooling roll 70, and thermally bonded as an outer layer. Then, the laminated sheet c composed of the inner layer, the main layer, and the outer layer is wound around the winding roll 90.

  Next, to form the laminated sheet formed as described above into a container, as shown in FIG. 3, the laminated sheet c is heated with a heater 100 and then formed into a container with a thermoforming machine shown in FIG. To do. In FIG. 4, reference numeral 111 denotes a female mold, and 112 denotes a male mold. A heater 113 is embedded in the female mold 111 and the male mold 112. The female die 111 has a number of vacuum ports (not shown), and the male die 112 has a number of vacuum ports (not shown).

  In order to manufacture a heat-resistant transparent container with such a thermoforming machine, the laminated sheet c is introduced into the thermoforming machine, sucked from the vacuum port of the male mold 112 and blown out of compressed air from the vacuum port of the female mold 111. The laminated sheet c is brought into close contact with the male mold 112 and formed into a container shape. In this state, after holding and heat-fixing for a while, the compressed air is blown out from the vacuum port of the male mold 112 and sucked from the vacuum port of the female mold 111 to press the container against the female mold 111, and the outside of the container is Cooling.

[Preparation of PET resin material]
PET resin (manufactured by Unitika Ltd. “MA-2101M”: intrinsic viscosity 0.62 dl / g, water content 2,900 ppm) 87 parts by weight and talc MB (Matsumura Chemical Co., Ltd. prototype: PETG 40% by weight + talc 60) 8 parts by weight), chain extender MB (Maisai Chemical Co., Ltd. prototype: PETG 70% by weight + BASF Japan ADR4368S 30% by weight) 1 part by weight, white pigment MB (Dai Nippon Ink Co., Ltd.) “L-9583” (50% by weight of PET + 50% by weight of white pigment) 4 parts by weight were weighed using a gravimetric metering feeder and uniformly mixed with a mixer.

[Production of laminated sheet]
This PET resin material (for the main layer) is put into a main extruder (“TEX105α” manufactured by Nippon Steel Works Co., Ltd .: L / D = 31.5, biaxial, 2 vent holes), extrusion temperature 280 ° C., vent While extruding while sucking and degassing under a high vacuum of -101 kPa from the hole, PET resin (for inner layer: "MA-2101M" manufactured by Unitika Ltd .: inherent viscosity 0.62 dl / g, water content 2,900 ppm) Was introduced into a sub-extruder (“TEX65α” manufactured by Nippon Steel Works Co., Ltd .: L / D = 31.5, 2 shafts, 2 vent holes). The sheet was extruded while being sucked and degassed, and a laminated sheet composed of a main layer and an inner layer was formed by coextrusion from a T die.

  At the same time, a printing film (for outer layer) in which a cooked gratin pattern and characters such as explanatory text are printed on an A-PET film having a thickness of 30 μm is fed out, and a co-extruded resin layer (main layer / A laminated sheet having a total thickness of 360 μm was prepared by heat bonding in accordance with the outer side of the main layer of the inner layer).

<Behavior of moisture content>
The screw and vacuum suction during continuous extrusion were temporarily stopped, the resin at the first and second vent hole positions of the main extruder and the sub-extruder was sampled, and the water content was measured. The moisture measurement was performed using a moisture vaporizer for plastics ("ADP-351 type" manufactured by Kyoto Electronics Industry Co., Ltd.) and a Karl Fischer moisture meter ("MKC-210 type" manufactured by Kyoto Electronics Industry Co., Ltd.). The results are shown in Table 1.

  Both the resin of the main extruder and the resin of the sub-extruder have a large amount of moisture before charging at the position of the first vent hole, which is 10 ppm or less, clearing 50 ppm or less, which is usually essential when extruding PET resin. It turns out that it becomes 0 ppm in the position of a 2nd vent hole, and it is not necessary to dry beforehand by sucking and deaerating from a vent hole.

<Evaluation of residual acetaldehyde>
The laminated sheet is cut into a size of 1 cm × 2 cm to produce a cut piece of a food tray, and a large number of cut pieces corresponding to a total surface area of 250 cm ² on the front and back sides are attached with a 500 ml slit plug. Into a glass Erlenmeyer flask. Next, the air in the Erlenmeyer flask was replaced with N ₂ gas at 40 ° C. in a room at 40 ° C. (N ₂ gas 2 ml / surface area 1 cm ² ), then sealed with a stopper and left at 40 ° C. for 24 hours.

  The acetaldehyde in the gas phase of the Erlenmeyer flask treated in this way was measured with a gas chromatograph (with “GC-6A type” FID detector manufactured by Shimadzu Corporation). The results are shown in Table 2.

  Acetaldehyde was not detected by gas chromatography. Therefore, it was confirmed that there was no residual acetaldehyde.

[Molding of heat-resistant food containers]
Using a vacuum / pneumatic molding machine ("FVS-5000P" manufactured by Wakisaka Engineering Co., Ltd.), the molding die is made in a similar shape so that the spacing between the female die and the male die is 1.0 mm. A 0.7 mm vacuum / compressed air port was formed in both the female mold and the male mold, and suction and compressed air blowing were made possible by switching between vacuum and compressed air. The mold shape was a female mold with an upper diameter of 128 mmΦ, a lower diameter of 95 mmΦ, a depth of 35 mm, and a rounded bottom corner.

  The prepared laminated sheet was heated and softened with a heater so that the surface temperature became 130 ° C., and then the female mold was set at 170 ° C. and the male mold was set at 70 ° C. In this state, the vacuum / pressure port of the female mold is evacuated, the vacuum / pressure port of the male mold is evacuated and 0.5 MPa of compressed air is blown, and the laminated sheet is brought into close contact with the female mold for 5.0 seconds. Then, the vacuum / pressure port of the female mold is pressurized and blown with 0.5 MPa of pressure, and the vacuum / pressure port of the male mold is evacuated and the container is brought into close contact with the male mold for 5.0 seconds. The container was removed after cooling. The molded product was well released from the mold, and the mold shape was completely reproduced without wrinkles or deformation. Also, the appearance was excellent in cosmetic properties without fading or discoloration of printing ink.

<Crystallinity of molded product>
A part of the bottom of the molded product was cut out, 10.0 mg of the sample was taken as a sample, each calorific value was obtained with a differential scanning calorimeter (Seiko Electronics “DSC220”), and calculated based on the following formula. The measurement conditions were a measurement sample (10.0 mg) and nitrogen of 50 ml / min. Flow rate is 10 ° C / min. The temperature was raised to 20 to 300 ° C. and measured.

結晶化度は２１．９％であった。

The crystallinity was 21.9%.

<Solid content contributing to heat resistance>
As described above, the total amount of PET crystal portion and talc, which are solid in the soft sea of the amorphous portion of PET, contributes to heat resistance, and the amount present affects the heat resistance.

  The crystallinity of PET is the amount of the entire molded product, and the talc content is the content of only the main layer, but it is mainly the heat resistance of this main layer that contributes to the heat resistance. Can determine heat resistance. Further, as is apparent from FIG. 5, the crystallization rate of PET added with talc is higher than that of pure PET, and therefore the crystallinity of the main layer is larger than the above value (21.9). I think that the.

<Heat resistance of molded products>
The molded product was placed in a constant temperature dryer at 200 ° C. and left for 30 minutes. When the appearance was observed, the shape before the test was maintained without any distortion or wrinkles. When the degree of crystallinity was measured by DSC, 21.9% before the test was 27.9% after the test, and it is considered that crystallization progressed, and at 200 ° C., 0 minutes, 10 minutes, 20 minutes, and 30 minutes. The crystallinity over time was measured. The results are shown in Table 3.

時間の経過とともに結晶化が進み耐熱性が向上していると考えられる。

It is thought that crystallization progresses with time and heat resistance is improved.

<Cooking>
A commercial frozen gratin was put in a molding container, and cooking was performed at 250 ° C. for 15 minutes in an oven. Gratin was well cooked, the contents were taken out, washed and rinsed with water, and the container was observed for deformation and the appearance of the inner PET resin layer, but there was no deformation such as twisting or kinking. That is, no change was observed in the molded container before and after cooking.

  After the contents were taken out and washed with water, the crystallinity of the container was measured by DSC. As a result, it was 25.3% (crystallinity + talc = 30.1%). Although the container was heated at 250 ° C., the container was in contact with the contents, so the temperature did not rise, and crystallization progressed at the time when 220 ° C. from the optimal crystallization temperature shown in FIG. It is considered a thing.

[Production of laminated sheet]
For the main extruder, 88 parts by weight of PET resin (“MA-2101M” manufactured by Unitika Ltd.), 1 part by weight of chain extender MB (Maisai Chemical Co., Ltd.), and talc MB (Matsumura Chemical ( Co., Ltd. Prototype: PET consisting of 8 parts by weight PETG 40% by weight + talc 60% by weight and 3 parts by weight of black pigment MB (Dainippon Ink Co., Ltd. “BK-250DCT”: 70% PET + 30% black pigment) The main layer (300 μm) / inner layer (with the same equipment and conditions as in Example 1 except that the resin material was used and the PET resin (“MA-2101M” manufactured by Unitika Ltd.) was used for the sub-extruder. 30 μm) A laminated sheet having a total thickness of 330 μm was produced. In addition, the printing film (outer layer) is not bonded.

[Molding of heat-resistant food containers]
Using the same vacuum / pressure forming machine and mold as in Example 1, the male mold was molded as a heating mold and the female mold as a cooling mold. That is, the laminated sheet is heated and softened with a heater so that the surface temperature becomes 130 ° C., and then the vacuum / pressure port of the male mold set at 170 ° C. is evacuated, and the female metal set at 70 ° C. The mold vacuum / pressure port is pressurized and 0.5 MPa pressure is blown in, the laminated sheet is closely attached to the male mold for 5.0 seconds and molded into a container, and then the female mold vacuum / pressure port is evacuated. At the same time, the vacuum / pressure port of the male mold was pressurized and blown with 0.5 MPa of compressed air, the container was brought into close contact with the female mold and cooled, and the container was taken out. The molded product was well released from the mold, and the mold shape was completely reproduced without wrinkles or deformation.

<Crystallinity of molded product>
As in Example 1, a part of the bottom was cut out and the crystallinity was measured by DSC. The result was 23.0%. Combined with 4.8% talc content,

となる。
したがって、実施例２の固体分量（結晶化度＋タルク量）は、実施例１の固体分量より多いので、実施例１より大きい耐熱性があると考えられる。

It becomes.
Therefore, since the solid content (crystallinity + talc content) of Example 2 is larger than that of Example 1, it is considered that the solid content is higher than that of Example 1.

10: quantitative feeder 20: mixer 30: main extruder 31: cylinder 33, 34: vent hole 41: cylinder 43, 44: vent hole 60: T die 70: cooling roll 80: printing film feed roll

Claims (5)

A chain extender and talc are added to PET resin, put into an extruder with 2 or more vent holes, and sucked and degassed under high vacuum of -99.99 kPa or more from the vent holes with PET resin heated and melted After that, a sheet is formed by extrusion molding, and the sheet is vacuum-compressed with a thermoforming machine, and a container is formed by holding at 100 to 220 ° C. in a molding die. A heat-resistant food container, wherein the total amount of crystal parts and talc content is 25% or more.

The heat-resistant food container according to claim 1, wherein the chain extender is a styrene / acryl oligomer having 4 or more epoxy groups, and the amount of the talc added is 2 to 15%. The heat-resistant food container according to claim 1 or 2, wherein an inner layer comprising a PET resin layer is provided, and the inner layer is formed by a coextrusion method. An A-PET film or an A-PET film is provided with an outer layer made of a printing film obtained by gravure printing on a film obtained by stretching 1.5 to 2.5 times in the MD direction, and the outer layer is formed by heat bonding. The heat-resistant food container according to claim 1, 2 or 3. Add a chain extender having 4 or more epoxy groups and 2 to 15% by weight of talc to the PET resin as the main layer, put it into the main extruder with 2 or more vent holes, and vent the PET resin as the inner layer The holes were introduced into a sub-extruder having one or more holes, and each PET resin was heated and melted and sucked and degassed from the vent hole under a high vacuum of -99.99 kPa or more, and then the main layer was formed by co-extrusion. An inner layer is formed, and an outer layer made of a printing film obtained by performing gravure printing on a film obtained by stretching the A-PET film or A-PET film 1.5 to 2.5 times in the MD direction is thermally bonded to the main layer. And a laminated sheet comprising the inner layer, the main layer, and the outer layer is vacuum-compressed with a thermoforming machine and maintained at 100 ° C. to 220 ° C. in a molding die. .

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