KR102173380B1 - Polyethylene terephthalate foam sheet, method for producing the same, molded article and method for producing the molded article - Google Patents

Abstract

The present invention relates to a polyethylene terephthalate foam sheet, a method for producing the same, a molded article, and a method for producing the molded article. According to the present invention, in the polyethylene terephthalate (PET) resin foam sheet provided with a resin layer having a multilayer structure, the resin layer is made of PET resin, and a chain extender containing an anhydride functional group 0.1 to 2 parts by weight relative to the weight of the resin is added to induce reaction extrusion, and it is manufactured in a continuous process through a tandem foaming extruder equipped with a coextrusion die, and the resin layer includes at least one PET foam layer and at least A PET resin foam sheet having a multilayer structure including one non-foaming PET layer is provided. By performing a thermoforming process on the PET resin foam sheet provided with a resin layer having a multilayer structure of the present invention, various three-dimensional food containers having excellent heat resistance and human safety can be manufactured.

Description

Polyethylene terephthalate foam sheet, its manufacturing method, molded article, and manufacturing method of the molded article {POLYETHYLENE TEREPHTHALATE FOAM SHEET, METHOD FOR PRODUCING THE SAME, MOLDED ARTICLE AND METHOD FOR PRODUCING THE MOLDED ARTICLE}

The present invention relates to a polyethylene terephthalate foam sheet, a method for manufacturing the same, a molded article, and a method for manufacturing the molded article. Specifically, the present invention relates to a multi-layered polyethylene terephthalate foam sheet using a continuous process coextrusion foaming method, a method of manufacturing the same, a molded article using the foam sheet, and a method of manufacturing the molded article.

Because of its low price and convenience, the expanded polystyrene molded container, which is widely used around the world, has a high risk of eluting environmental hormones when heated at high temperatures or in a microwave oven. In addition, the foamed polystyrene molded container has only heat resistance of about 105 degrees Celsius and cannot be used in a steam oven or roasting oven. Therefore, there is great interest in new eco-friendly containers that can overcome the disadvantages of expanded polystyrene molded containers.

Polyethylene terephthalate (PET) resin is one of the typical packaging plastics. Polyethylene terephthalate resin is a general-purpose resin that has been proven to be safe enough to be used in many beverage bottles and beverage cups. In addition, the cost of raw materials is also low, making it the most realistic eco-friendly plastic that can replace various packaging materials based on expanded polystyrene resin.

However, the polyethylene terephthalate resin has a low viscosity and poor foaming properties, making it difficult to manufacture a sheet having a pore structure. In addition, the glass transition temperature of the polyethylene terephthalate resin itself is at the level of 75 degrees Celsius, and its heat resistance rises to a maximum of 220 degrees Celsius through crystallization. Since polyethylene terephthalate resin is a linear polymer and does not have a high molecular weight, it is difficult to obtain rheological properties suitable for low-density extrusion foaming, and the window of the foaming extrusion process is very narrow. In many cases, the polyethylene terephthalate resin discharged from the extruder has a very low viscosity compared to the general general polymer polyethylene resin. Therefore, it is very difficult to produce a low-density foam having a high expansion ratio by extrusion, which is a continuous process.

Various studies and attempts have been made to overcome the limitations of polyethylene terephthalate resin. A technology has been developed in which a chain extender having an anhydride functional group is reacted and extruded with a polyethylene terephthalate resin to foam. When the chain extender reacts with the polyethylene terephthalate resin, the molecular weight of the resin is increased, and the long chain side chain is attached to the back bone. In this case, since the molecular form of polyethylene terephthalate with long chains attached in the form of a branch is obtained, the melt strength is remarkably increased and the foam sheet has an excellent cell structure and a high foaming ratio by showing a strain hardening behavior. Alternatively, a foam can be obtained.

However, most chain extenders have two or more reactive functional groups such as epoxy, anhydride, and isocyanate in one molecule, and are known to exhibit toxicity when absorbed into the human body. . It has been confirmed that the foam containing the chain extender having such a reactive functional group is safe to contain low-temperature foods such as meat and fruits, but safety has not been confirmed for use in environments such as boiling water, microwave ovens, and high-temperature ovens. That is, at high temperatures, the molecular mobility of the unreacted chain extender is large and the elution is relatively easy, and thus the safety of the human body cannot be guaranteed because the chain extender is included in the food contained therein.

There is a method of bonding a thin barrier layer to the foam layer in order to solve this shortcoming of a chain extender, which is essential for the foamability of polyethylene terephthalate resin. The most representative methods include non-foaming film lamination method and extrusion coating method. Korean Patent Publication (Patent Publication No. 10-2018-0036418) first manufactures a polyethylene terephthalate single-layer foam sheet by extrusion, and then a non-foamed polyethylene terephthalate resin or a non-foamed polyethylene terephthalate glycol resin. A method of manufacturing a multi-layered foam sheet was proposed through a method of coating with a subsequent process, an extrusion coating method. Through this method, it is possible to manufacture a multi-layered foam sheet, and it is possible to escape the risk of dissolution of toxic chain extenders into food.

As a method of adding a non-foaming layer to the polyethylene terephthalate resin single-layer foam sheet manufactured by the extrusion foaming process as described above, the non-foaming film and the foam sheet that have already been made are laminated by using heat, or the foam sheet is made by extrusion coating method. A method of coating a non-foaming layer on top can be considered.

However, these methods have fatal drawbacks. Basically, these methods require a separate subsequent process to create a multi-layered structure, resulting in a rapid increase in process cost and a large loss due to defects between processes. In particular, in order to form a non-foaming layer on both sides of the foam sheet, it is necessary to go through two discontinuous processes, which increases the manufacturing cost burden.

First, in the thermal adhesive lamination method, only a very thick film having a thickness of 80 to 100 μm is used for the non-foaming film to be bonded without bursting in the process of applying heat. Therefore, the overall density of the film increases and the cost of raw materials increases, which limits commercialization.

Second, the method of forming a non-foaming layer by extrusion coating is extremely difficult to coat a film foil of uniform thickness due to the extremely low melt strength of polyethylene terephthalate resin, and for that reason, it is very difficult to reduce the thickness of the extrusion coating to less than 100 μm. . Therefore, high cost becomes a problem, and at the same time, defect loss due to coating thickness non-uniformity becomes significant. In particular, the variation in thickness of the non-foaming layer leads to a variation in the thickness of the molded article because variation occurs in the degree of softening due to heating in the thermoforming process.

Accordingly, there is a need for a method capable of manufacturing a multilayer foam sheet including a foam layer and a non-foam layer in a continuous process.

An object of the present invention is to solve the following problems in order to solve the above-described problems.

An object of the present invention is to provide a multilayer foam sheet comprising a foamed layer and a non-foamed layer manufactured by a continuous process.

It is an object of the present invention to provide a method for manufacturing a multilayer foam sheet including a foam layer and a non-foam layer in a continuous process.

An object of the present invention is to provide a foamed molded article manufactured by processing a multilayer foam sheet comprising a foamed layer and a non-foamed layer manufactured by a continuous process.

An object of the present invention is to provide a method for manufacturing a foamed molded article manufactured by processing a multilayer foam sheet including a foamed layer and a non-foamed layer manufactured by a continuous process.

The problem of the present invention is not limited to those mentioned above, and other problems that are not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

In the polyethyleneterephthalate (PET) resin foam sheet provided with a resin layer having a multilayer structure according to various embodiments of the present invention, the resin layer is made of PET resin, and a chain including an anhydride functional group Addition of 0.1 to 2 parts by weight of an extender relative to the weight of the resin induces reaction extrusion, and is manufactured in a continuous process through a tandem foaming extruder equipped with a coextrusion die, and the resin layer is at least one PET foam layer And at least one non-foaming PET layer.

A PET resin foam molded article having a three-dimensional shape manufactured by processing a PET resin foam sheet provided with a resin layer having a multilayer structure according to an embodiment of the present invention is obtained by heating the PET resin foam sheet in an oven at 200 to 350 degrees Celsius. Then, it is manufactured to have a three-dimensional shape by pressing for 3 to 15 seconds with a molding mold heated to 100 to 250 degrees Celsius, and the crystallinity of the PET resin foam sheet is 10% or more after pressing with the molding mold.

The present invention can provide a multilayer foam sheet comprising a foam layer and a non-foam layer manufactured by a continuous process.

The present invention can provide a method of manufacturing a multilayer foam sheet comprising a foam layer and a non-foam layer in a continuous process.

The present invention can provide a foamed molded article manufactured by processing a multilayer foam sheet including a foamed layer and a non-foamed layer manufactured by a continuous process.

The present invention can provide a method for manufacturing a foamed molded article manufactured by processing a multilayer foam sheet including a foamed layer and a non-foamed layer manufactured by a continuous process.

The effects of the present invention are not limited to those mentioned above, and other effects that are not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

1 shows a process of manufacturing a two-layered polyethylene terephthalate resin foam sheet according to various embodiments of the present invention.
2 illustrates a process of manufacturing a three-layered polyethylene terephthalate resin foam sheet according to various embodiments of the present disclosure.
3 is a cross-sectional view of a three-layered polyethylene terephthalate resin foam sheet according to various embodiments of the present disclosure.
4 illustrates a process of manufacturing a molded article using a multilayer polyethylene terephthalate resin foam sheet according to various embodiments of the present invention.
5 shows a molded article manufactured using a multilayer polyethylene terephthalate resin foam sheet according to various embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various forms and is not limited to the embodiments described herein.

The present invention relates to a foam sheet of a multi-layered polyethylene terephthalate (PET) resin using a continuous process of coextrusion foaming, a method of manufacturing the same, a molded article, and a method of manufacturing the molded article. The finished product implemented through the present invention is characterized by excellent heat resistance and safety suitable for a bowl noodles container, a disposable food container, a ready-to-eat food container, a steam oven, a high temperature oven, and a heating container for a microwave oven. In addition, not only the high productivity of the continuous process, but also the low density of the foamed layer and the low thickness of the non-foamed layer result in a low total raw material cost, which leads to high commercial competitiveness. The excellent oxygen barrier property, which is an inherent property of polyethylene terephthalate resin, has the advantage of extending the shelf life compared to the weight of polypropylene resin or polystyrene resin when used as a processed food packaging container.

Polyethylene terephthalate resin is a linear polymer and has inherent rheological properties that are not suitable for foam extrusion due to low resin viscosity and melt strength. Therefore, it is essential to add a chain extender to improve the molecular weight through reaction extrusion, and to modify the polymer structure to attach long branched branches to the main chain is required. However, due to the toxicity of the chain extender, when used as a food container, even if it is used in a very small amount, it may be eluted into food, so there is a concern about human body effects when it is used for purposes such as high temperature food or microwave heating.

As a method of adding a non-foaming layer to the polyethylene terephthalate resin single-layer foam sheet manufactured by the extrusion foaming process, the non-foaming film and the resin foam sheet that have already been made are laminated and bonded using heat, or the resin foam sheet using the extrusion coating method. You can consider how to coat the top. However, these methods have fatal drawbacks. Basically, these methods require a separate subsequent process to create a multi-layered structure, resulting in a rapid increase in process cost and a large loss due to defects between processes. In particular, in order to form a non-foaming layer on both sides of the resin foam sheet, it is necessary to go through two discontinuous processes, which increases the manufacturing cost burden.

In the present invention, as an advanced method capable of improving the above-described problems, a method for manufacturing a multilayer foam sheet of polyethylene terephthalate resin using a coextrusion foaming method is proposed.

In the present invention, through a coextrusion foaming process of a polyethylene terephthalate resin and a subsequent thermoforming process, a new method of manufacturing a food container having excellent heat resistance and safety for human body while maintaining low manufacturing cost is proposed.

1 illustrates a process of manufacturing a two-layered polyethylene terephthalate resin foam sheet according to various embodiments of the present disclosure. 2 illustrates a process of manufacturing a three-layered polyethylene terephthalate resin foam sheet according to various embodiments of the present disclosure.

Specifically, FIG. 1 shows a manufacturing process of a polyethylene terephthalate resin foam sheet composed of two layers manufactured by a tandem foam extruder according to various embodiments of the present invention. 2 is a diagram illustrating a manufacturing process of a three-layer polyethylene terephthalate resin foam sheet manufactured by a tandem foam extruder according to various embodiments of the present invention.

1 shows a process of manufacturing a resin foam sheet having a two-layer structure through foam extrusion of a polyethylene terephthalate resin blended with a functional additive. 2 shows a process of manufacturing a resin foam sheet having a three-layer structure through foam extrusion of a polyethylene terephthalate resin blended with a functional additive.

The tandem foam extruder has a structure in which primary extruders 11 and 21 and secondary extruders 13 and 23 are connected in series. In addition, the gas injection port of the foaming agent pumps 12 and 22 is processed so that the foaming agent can be injected in the middle of the primary extruder. At the end of the tandem foam extruder, co-extrusion dies 14 and 24 are mounted.

The extruders 17 and 27 supplying the polyethylene terephthalate resin used for the non-foaming layer are directly connected to the bodies of the coextrusion dies 14 and 24 by a connecting pipe. A diverter valve is installed between the connection pipe and the coextrusion dies 14 and 24, so that a non-foaming layer resin containing no foaming agent is provided as one layer on one surface of the foam layer or on both surfaces. It is possible to control by selecting the direction of the flow of the resin so that it is formed into two layers, one by one. Here, the coextrusion dies 14 and 24 are preferably annular coextrusion dies 14 and 24 in order to suppress the wrinkle problem of the polyethylene terephthalate resin foam sheet.

The tubular foam sheet discharged from the annular coextrusion dies 14 and 24 is unfolded through a cutter at the ends of the mandrels 15 and 25 when passing while surrounding the drum-shaped mandrel 15 and 25 . The surface of the polyethylene terephthalate resin foam sheet becomes smoother through the mandrel (15, 25), and at the same time, the sheet is effectively cooled in a short time, thereby providing a sufficient level of mechanical strength to withstand the tension of the winder. Can be obtained.

After passing through the mandrel (15, 25), a foam sheet 16 of polyethylene terephthalate resin having a two-layer structure consisting of one foam layer and one non-foam layer, or one foam layer and the foam layer It is possible to obtain a foam sheet 26 of a polyethylene terephthalate resin having a three-layer structure consisting of a total of two non-foaming layers arranged one on each side of the.

The basic equipment of the process is a tandem foaming extruder equipped with a co-extrusion die, and a 1 to 6 mm polyethylene terephthalate foam layer and a 5 to 50 μm thickness polyethylene terephthalate on one or both surfaces thereof. The multi-layered foam sheet to which the non-foaming layer is bonded can be manufactured in one continuous process.

The resin layer according to various embodiments of the present invention is made of polyethylene terephthalate resin, and 0.1 to 2 parts by weight of a chain extender containing an anhydride functional group is added to the resin to induce reaction extrusion, and the coextrusion die is It is manufactured in a continuous process through a mounted tandem foaming extruder, and the resin layer has a multilayer structure including at least one polyethylene terephthalate foam layer and at least one polyethylene terephthalate non-foam layer.

The manufacturing method of the resin foam sheet according to various embodiments of the present invention is a single continuous process, so the processing cost is remarkably low, and it is possible to manufacture a multilayer foam sheet including a non-foamed polyethylene terephthalate layer having a thin and uniform thickness. It has process stability. In the foam layer of the multilayer foam sheet according to various embodiments of the present invention, a polyethylene terephthalate resin, a foaming agent, a nucleating agent, a chain extender, a crystallization accelerator, and a color pigment are uniformly blended. The polyethylene terephthalate resin may have an intrinsic viscosity (IV) of 0.5 ㎗/g to 0.8 ㎗/g.

In the method of manufacturing a polyethylene terephthalate resin foam sheet using the coextrusion foaming method according to various embodiments of the present invention, unlike traditional foaming equipment, a precise coextrusion die is used, so two layers (foamed layer-non-foamed layer) or three layers A multilayer foam sheet of (non-foaming layer-foaming layer-non-foaming layer) can be easily prepared. According to the method of manufacturing a polyethylene terephthalate resin foam sheet according to various embodiments of the present invention, since the non-foaming layer has a uniform thickness and is formed as thin as 50 μm or less, the raw material cost of the entire polyethylene terephthalate multilayer foam sheet is lowered. Since the multi-layer foam sheet can be manufactured through a continuous process of, there is an effect of remarkably increasing process efficiency and cost competitiveness. Therefore, the manufacturing method of the resin foam sheet according to various embodiments of the present invention has a differentiated manufacturing cost and quality competitiveness compared to the thermal bonding lamination method or extrusion coating method.

In order to manufacture the polyethylene terephthalate resin foam sheet at high magnification, a tandem foaming extruder is essentially required. That is, two extruders must be connected in series. Here, the first extruder performs uniform kneading and thickening reaction of the raw material, and the second extruder efficiently cools the resin melt in which the foaming gas is dissolved, thereby improving the rheological properties to a viscosity suitable for high magnification foaming.

By installing a coextrusion die in the tandem foam extruder, a 1 to 6 mm polyethylene terephthalate foam layer and a 5 to 50 μm non-foam polyethylene terephthalate thin film layer can be stably applied to one or both surfaces thereof. Therefore, the production method of the resin foam sheet using the coextrusion foaming method according to various embodiments of the present invention has high productivity. In addition, since the non-foaming layer of polyethylene terephthalate, which can prevent the elution of toxic chain extenders despite the low raw material cost, comes in direct contact with food, even in the case of bowl noodles containing boiling water or instant food containers heated in a microwave oven. It can be used safely.

In the resin foam sheet using the coextrusion foaming method according to various embodiments of the present invention, the foaming ratio of the polyethylene terephthalate foaming layer is 2 to 20 times, and the average foaming ratio of the entire multilayer sheet including the non-foaming layer is 1.5 to 18. It doubles. Therefore, the overall raw material cost is very low.

The polyethylene terephthalate foam layer of the resin foam sheet according to various embodiments of the present invention uses a polyethylene terephthalate resin as a basic raw material as its composition, and preferably, when a physical foaming agent is used, a foaming ratio of 2 to 20 times is obtained. I can. According to an embodiment, as the physical blowing agent, a mixed blowing agent composed of an inert gas such as carbon dioxide and nitrogen and a hydrocarbon gas such as butane and pentane, or a combination thereof. Can be used. The addition of the foaming agent is required to inject 0.1 to 10 parts by weight based on the weight of the resin through the primary extruder cylinder according to the desired expansion ratio. The polyethylene terephthalate foam layer of the polyethylene terephthalate resin foam sheet according to various embodiments of the present invention selects at least one of carbon dioxide, nitrogen, butane, pentane, or a mixture thereof as a physical foaming agent, and 0.1 to 10 parts by weight based on the weight of the resin. It can be produced by kneading.

The chain extender is 0.2 to 2 parts by weight of an additive having a reactive functional group such as epoxy, anhydride, and isocyanate, based on the weight of the polyethylene terephthalate resin.

As a nucleating agent, talc having a diameter of 1 to 50 μm may be added in an amount of 0.1 to 5 parts by weight based on the weight of the resin. The polyethylene terephthalate foam layer of the polyethylene terephthalate resin foam sheet according to various embodiments of the present invention is at least one of talc, calcium carbonate, titanium dioxide, or a mixture thereof as a nucleating agent. It can be prepared by selecting and kneading 0.1 to 5 parts by weight based on the weight of the resin.

In addition, it is preferable to add a crystallization accelerator in order to improve the crystallization rate in the thermoforming process. The crystallization accelerator should be mixed with a polyethylene terephthalate resin in an amount of 0.1 to 5 parts by weight based on the weight of the resin.

The composition of the non-foaming layer coextruded into a thin film on the surface of the foam layer described above uses a polyethylene terephthalate resin as a basic raw material and does not contain a chain extender, a foaming agent, and a nucleating agent. However, according to an embodiment, a crystallization accelerator may be added to the non-foaming layer in order to improve the crystallization rate in the thermoforming process. For example, additives such as color pigments and antistatic agents may be added. According to various embodiments, as the crystallization accelerator, stearic acid, hydroxystearic acid, ethylenebis stearamide, and the like are suitable.

According to various embodiments of the present invention, the polyethylene terephthalate foam layer and the polyethylene terephthalate non-foam layer of the polyethylene terephthalate resin foam sheet according to various embodiments of the present invention, as crystallization accelerators, are stearic acid and hydride. It may be prepared by selecting at least one of hydroxystearic acid, ethylenebis stearamide, or a mixture thereof and kneading 0.1 to 5 parts by weight based on the weight of the resin.

3 is a cross-sectional view of a three-layered polyethylene terephthalate resin foam sheet according to various embodiments of the present invention.

Specifically, FIG. 3 is a cross-sectional view of a polyethylene terephthalate resin foam sheet having a three-layer structure manufactured according to a manufacturing method according to various embodiments of the present invention, that is, a non-foaming layer-foaming layer-non-foaming layer. An electron microscope picture is shown.

An example of a polyethylene terephthalate resin foam sheet manufactured according to the method presented in the present invention is a very thin film with a thickness of 20 μm, a non-foaming polyethylene terephthalate layer located on the surface of the polyethylene terephthalate foam layer, and has a very uniform thickness. .

4 shows a process of manufacturing a molded article using a multilayer polyethylene terephthalate resin foam sheet according to various embodiments of the present invention.

Specifically, FIG. 4 shows a process of heating a multilayer polyethylene terephthalate foam sheet fabric according to various embodiments of the present invention and thermoforming with a molding mold to produce a final product having a desired shape.

4 shows the overall flow of a thermoforming process for a multilayer polyethylene terephthalate foam sheet consisting of two layers as an embodiment.

The polyethylene terephthalate multilayer foam sheet fabric manufactured according to the method of FIGS. 1 to 2 is a subsequent process, and can be used after being molded into a heat-resistant food container having a three-dimensional shape or a heat-resistant tray for packaging through the thermoforming process of FIG. 4. have.

In the thermoforming process, the resin foam sheet is molded into a container or tray having a specific shape by pressing a vacuum mold. When heat is applied for a temperature and time that can induce crystallization of the polyethylene terephthalate resin foam sheet in the press-compressed state of the molding mold, the crystallinity of the polyethylene terephthalate resin foam sheet is remarkably increased, resulting in a polyethylene terephthalate resin foam molded product having excellent heat resistance. Can be obtained.

The multi-layered polyethylene terephthalate resin foam sheet manufactured according to the method of FIGS. 1 to 2 is wound in a roll 41 state and subjected to an aging process for about 3 to 10 days, and then some of the foaming agent remaining in the foam layer is discharged. Is done. That is, the multi-layered polyethylene terephthalate resin foam sheet manufactured by the method according to various embodiments of the present invention must be aged through a degassing step for a predetermined time.

Subsequently, the multilayered polyethylene terephthalate resin foam sheet manufactured by the method according to various embodiments of the present invention undergoes a thermoforming process to form various molded products such as food containers or trays. In this case, the foam sheet consisting of two layers can function as a barrier layer to prevent elution of the chain extender only when the non-foaming layer is disposed inside the food container.

As the start of the thermoforming process, the resin foam sheet is heated in a heating oven 42 to 200 to 350 degrees Celsius to soften it to a level capable of deformation. According to an embodiment, a ceramic heater oven may be used as the heating oven. According to an embodiment, the heating oven 42 may heat the resin foam sheet at 200 to 350 degrees Celsius.

Then, the heated resin foam sheet is pressed with a molding mold 43 to deform to have a three-dimensional shape in the form of a container or a tray. At this time, the molding mold must be heated in order to maximize the crystallinity so that the resin foam sheet has heat resistance. According to one embodiment, the molding mold 43 must be heated to 100 to 250 degrees Celsius to obtain a crystallinity of 10% or more of the resin foam sheet in a short time. According to an embodiment, the molding mold 43 may be manufactured to have a three-dimensional shape by pressing the resin foam sheet for 3 to 15 seconds.

According to various embodiments of the present invention, cooling water is circulated in the molding mold to allow cooling in a short time, so that the molded product can be smoothly exited from the mold.

The molded resin foam sheet is punched by a press trim machine.

The finished final molded article can be used as a container. In the structure 44 of the final molded article, a non-foaming layer of polyethylene terephthalate, which is safe for direct contact with food, is positioned on the inner side of the container to which the food touches.

5 shows a molded article manufactured using a multilayer polyethylene terephthalate resin foam sheet according to various embodiments of the present invention.

Specifically, FIG. 5 shows an example of a molded article having heat resistance that can be manufactured by thermoforming a multi-layered polyethylene terephthalate resin foam sheet manufactured according to a manufacturing method according to various embodiments of the present invention.

Referring to FIG. 5, a cross-sectional structure of a multi-layered polyethylene terephthalate foam sheet and various types of molded articles are shown.

According to various embodiments of the present invention, a polyethylene terephthalate resin foam sheet having at least one non-foaming polyethylene terephthalate layer 51 and at least one polyethylene terephthalate foaming layer 52 has various three-dimensional shapes through a thermoforming process. It can be manufactured as a final molded article 53 having.

The multi-layered foamed molded article 53 of polyethylene terephthalate resin molded by the method according to various embodiments of the present invention has heat resistance of 120 to 220 degrees Celsius and microwave heating safety depending on the crystallinity of the resin. Therefore, there is no problem in using it as a bowl of boiling water, a coffee cup, etc., there is no deformation of the container even when it is used as a lunch box to heat food by putting it in a microwave, and the risk of dissolution of toxic chain extenders is also a source. Can be excluded. Furthermore, since the foam layer is included and has thermal insulation, it is convenient to hold it with bare hands, and it has the advantage of being an eco-friendly molded product that can keep food warm and cold.

The foamed molded article having a multi-layered structure of a polyethylene terephthalate resin manufactured according to various embodiments of the present invention has heat resistance that can be used in an environment containing high-temperature food or heating in a microwave oven without concern for environmental hormones. Since the non-foaming layer of polyethylene terephthalate, which is safe for direct contact with food, is formed as a thin film, there is no risk of elution of the toxic chain extender added to secure foaming, so it is suitable as a container for various processed foods or bowl noodles.

In addition, since the inner surface of the food container is formed as a smooth non-foaming layer, after use as a food container, residual food and oil components can be removed cleanly with simple water cleaning, making plastic recycling easy. That's a big advantage over the

Furthermore, because of the excellent oxygen barrier property, which is the inherent property of polyethylene terephthalate resin, when used as a processed food packaging container, it can significantly extend the shelf life compared to polypropylene resin or polystyrene resin, so product distribution management It is more advantageous from the point of view.

Hereinafter, an embodiment of the present invention will be described. The following examples are only examples of the present invention, and the present invention is not limited to the following examples.

(Example)

The tandem foam extruder used has a structure in which a screw diameter of 100 mm single screw extruder (primary extruder) and a screw diameter of 130 mm single screw extruder (second extruder) are connected in series. In addition, the gas injection port is processed so that the physical blowing agent can be injected in the middle of the primary extruder. At the end of the tandem foam extruder, a coextrusion die was mounted. The extruder that supplies the resin used for the non-foaming layer is directly connected to the coextrusion die and the connecting pipe. A diverter valve is provided between the connection pipe and the coextrusion die, so that the non-foaming layer resin may be selected to be formed on one side or both sides of the foam layer. Here, as for the coextrusion die, an annular coextrusion die is suitable in order to suppress the wrinkle problem of the foam sheet.

The polyethylene terephthalate resin used in the foamed layer and the non-foamed layer was a resin having an intrinsic viscosity (IV) of 0.8 ㎗/g. As a foaming agent, 4 parts by weight of iso-butane, a chain extender having a molecular weight of 6800, and 0.5 parts by weight of a polymer type chain extender including glycidyl methacrylate as a reactive functional group were added. In addition, 1 part by weight of talc was added as a nucleating agent and 1 part by weight of stearic acid was added as a crystallization accelerator. The composition of the non-foamed polyethylene terephthalate layer on the surface was the same composition, except for the nucleating agent, the foaming agent, and the chain extender from the above-described polyethylene terephthalate foaming layer composition.

The multi-layer foam sheet obtained through the foam extrusion process is composed of a total of two and three layers according to the number of non-foaming layers by controlling the setting of the diverter valve.The polyethylene terephthalate foam layer has a thickness of 2.5 mm and a density of 100 kg. /m ³ , and the thickness of the coextruded polyethylene terephthalate non-foaming layer is 15 μm. The multilayer foam sheet was aged for 5 days in a roll state, and then a thermoforming process was performed. After aging, the polyethylene terephthalate resin foam sheet was molded into a bowl shape through thermoforming.

When heating using an infrared heater (IR heater), the surface temperature of the foam sheet was about 350 degrees Celsius, and the heating time was carried out for 20 seconds. Then, by pressing the male and female mold mold in the form of a bowl with a diameter of 17 cm and a depth of 6 cm, the resin foam sheet is heated for about 10 seconds to obtain a crystallinity of more than 15% of the polyethylene terephthalate resin, and a thermoformed product with high heat resistance is manufactured. I did. At this time, the non-foaming layer is disposed inside the container, so that the foamed layer containing the chain extender does not directly contact food at high temperature.

In the case of a three-layered resin foam sheet, a non-foaming layer of polyethylene terephthalate is formed on both surfaces of the foam sheet through the setting of the diverter valve, so the placement of the inside and the outside of the container is irrelevant during molding. In this case, it is easier to match the color of the inside and the outside of the container. The container thus manufactured was excellent in heat resistance, and there was no deformation when boiling water was poured, and no deformation occurred even when heated in a microwave oven. In conclusion, it was possible to manufacture an eco-friendly food container with excellent heat resistance and no harm to humans.

According to various embodiments of the present invention, polyethylene terephthalate (PET) resin, which is widely used as a variety of packaging materials, is used as a basic material, and a foam layer and non-foaming method are used using a coextrusion foaming method, a continuous process with excellent productivity. Polyethylene terephthalate resin foam sheet fabric having a multilayer structure in which the layers are in contact can be manufactured.

In general, the multilayered polyethylene terephthalate foam sheet in the state of being extruded and foamed does not have a high degree of crystallinity, so the heat resistance temperature is limited to the level of 70 degrees Celsius. Accordingly, according to various embodiments of the present invention, the crystallinity of the polyethylene terephthalate resin can be maximized by heating the mold temperature of the subsequent thermoforming process to a level of 200 degrees Celsius in order to obtain a molded article having excellent heat resistance.

According to various embodiments of the present invention, foamed molded articles of polyethylene terephthalate resin having various shapes, such as bowl noodles, ready-to-eat food containers, lunch trays, beverage cups, etc., can be manufactured at low manufacturing cost and raw material cost. This polyethylene terephthalate resin foam molding container is characterized by excellent heat resistance capable of withstanding boiling water or microwave heating. In addition, since the inner surface of the container is formed as a smooth non-foaming layer, after use as a food container, residual food and oil components can be removed cleanly with simple water cleaning, and plastic recycling is easy compared to conventional polystyrene foam molding containers. That's an advantage.

Furthermore, the foamed molded container made of polyethylene terephthalate resin has excellent oxygen barrier properties as its intrinsic properties compared to the foam molded product made of polystyrene or polypropylene resin, which is widely used as a packaging material. When used as a container, the contents are not damaged and a long shelf life can be secured for long-term storage.

It will be apparent to those skilled in the art that the present invention may be embodied in other forms without departing from the technical spirit and essential features of the present invention. Therefore, the above embodiments should be considered from all viewpoints, not limiting. The scope of the present invention should be determined by rational interpretation of the appended claims and all possible changes within the equivalent scope of the present invention.

11: primary extruder 12: blowing agent pump
13: secondary extruder 14: coextrusion die,
15: mandrel 16: two-layer structure PET resin foam sheet
17: non-foaming PET layer extruder 21: primary extruder
22: blowing agent pump 23: secondary extruder
24: coextrusion die 25: mandrel
26: 3-layer structure PET resin foam sheet 27: non-foaming PET layer extruder
41: aged resin foam sheet 42: heater oven
43: press molding mold 44: structure of a molded product
51: PET non-foaming layer 52: PET foaming layer
53: final molded article

Claims (16)

As a method of manufacturing a polyethylene terephthalate (PET) resin foam sheet provided with a resin layer having a multilayer structure,
By adding 0.1 to 2 parts by weight of a chain extender containing an anhydride functional group to the PET resin to induce reaction extrusion, a tandem foaming extruder equipped with a coextrusion die and the above The resin layer having a multi-layered structure including at least one PET foam layer and at least one non-foamed PET layer having a thickness of 5 to 9 μm in a continuous process through a second extruder directly connected to the body of the coextrusion die Including the process of manufacturing,
The at least one PET foam layer is extruded through the tandem foam extruder,
The at least one non-foaming PET layer is extruded through the second extruder,
Method for producing a PET resin foam sheet.
The method of claim 1,
The at least one PET foam layer is prepared to foam at a foaming ratio of 2 to 20 times the composition before foaming,
Method for producing a PET resin foam sheet.
The method of claim 1,
The at least one PET foam layer is manufactured to have a thickness of 1 to 6 mm,
Method for producing a PET resin foam sheet.
The method of claim 1,
The at least one PET foam layer and the at least one PET non-foam layer,
By selecting at least one of stearic acid, hydroxystearic acid, ethylenebis stearamide, or a mixture thereof as a crystallization accelerator and kneading 0.1 to 5 parts by weight based on the weight of the resin Manufactured,
Method for producing a PET resin foam sheet.
The method of claim 1,
The at least one PET foam layer,
Prepared by selecting at least one of carbon dioxide, nitrogen, butane, pentane, or a mixture thereof as a physical blowing agent and kneading 0.1 to 10 parts by weight based on the weight of the resin,
Method for producing a PET resin foam sheet.
The method of claim 1,
The at least one PET foam layer is
Prepared by selecting at least one of talc, calcium carbonate, titanium dioxide, or a mixture thereof as a nucleating agent and kneading 0.1 to 5 parts by weight based on the weight of the resin,
Method for producing a PET resin foam sheet. delete delete delete delete delete delete delete delete delete delete

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