KR20200071155A - 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 foamed polyethylene terephthalate sheet, a manufacturing method thereof, a molded product, and a manufacturing method thereof. According to the present invention, the foamed PET sheet comprises a resin layer having a multilayered structure, wherein the resin layer is made of a PET resin, reaction extraction is induced by adding 0.1 to 2 parts by weight of a chain extender including an anhydride functional group with respect to the weight of the PET resin, the foamed PET sheet is manufactured through a continuous process using a tandem foaming extruder which includes a coextrusion die installed therein, and the resin layer has a multilayered structure including at least one foamed PET layer and at least one non-foamed PET layer. Accordingly, a thermal molding process is performed for the foamed PET sheet having the multilayered structure, thereby manufacturing various three-dimensional food containers having excellent heat resistance and safety.

Description

Polyethylene terephthalate foam sheet, manufacturing method thereof, 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 manufacturing method thereof, a molded article and a method for manufacturing the molded article. Specifically, the present invention relates to a polyethylene terephthalate foam sheet having a multilayer structure using a coextrusion foaming method, which is a continuous process, a manufacturing method thereof, a molded article using the foamed sheet, and a method for manufacturing the molded article.

Because of its low cost and convenience, foamed polystyrene molding containers, which are widely used around the world, have a high risk of elution of environmental hormones when heated at high temperatures or when heated in a microwave oven. In addition, the foamed polystyrene molded container only has a heat resistance of about 105 degrees Celsius and cannot be used in a steam oven or roasting oven. Therefore, there is a 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 with proven stability to be used in many beverage bottles or beverage cups. In addition, since the price of raw materials is also low, it is the most realistic eco-friendly plastic that can replace various packaging materials based on conventional expanded polystyrene resin.

However, 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 about 75 degrees Celsius, and through the crystallization, its heat resistance rises up to 220 degrees Celsius. Since polyethylene terephthalate resin is a linear polymer and has 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 has very narrow limitations. In many cases, the polyethylene terephthalate resin discharged from the extruder exhibits a very low viscosity compared to the general purpose polymer polyethylene resin. Therefore, it is very difficult to manufacture a low-density foam having a high foaming ratio by extrusion, which is a continuous process.

Various studies and attempts have been made to overcome the limitations of polyethylene terephthalate resins. A technology has been developed for reacting and extruding a chain extender having an anhydride functional group with a polyethylene terephthalate resin. When the chain extender reacts with the polyethylene terephthalate resin, the molecular weight of the resin is increased, and the side chain of the long chain is attached to the back bone. In this case, since the polyethylene terephthalate molecular form in which long chains are attached in the form of branches is obtained, the melt strength is markedly increased and the strain hardening behavior is exhibited, so that the foam sheet has excellent cell structure and high foaming magnification. 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 by 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 fruit, but it has not yet been confirmed to be used in environments such as boiling water, microwave ovens, and high-temperature ovens. That is, since the molecular mobility of the unreacted chain extender is high and the elution is relatively easy at a high temperature, the human body safety cannot be guaranteed because the chain extender is included in the contained food.

There is a method of bonding the barrier layer of the thin film to the foam layer in order to solve this disadvantage of the chain extender, which is essential for the foamability of the polyethylene terephthalate resin. The most representative methods include a non-foaming film lamination method and an extrusion coating method. In Korean Patent Publication (Patent Publication No. 10-2018-0036418), a polyethylene terephthalate single-layer foam sheet is first manufactured by extrusion, and a non-foamed polyethylene terephthalate resin or a non-foamed polyethylene terephthalate glycol resin is used. A method of manufacturing a foam sheet having a multi-layer structure was proposed through a method of coating with a subsequent process, an extrusion coating method. Through this method, a multi-layered foam sheet can be produced, 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 prepared by the extrusion foaming process as described above, lamination bonding of the non-foaming film and foam sheet, which has already been made, using heat, or foaming sheet by extrusion coating method A method of coating the non-foaming layer on top may be considered.

However, these methods have a fatal disadvantage. These methods basically require a separate follow-up process to create a multi-layered structure, so the process cost increases rapidly, and the loss due to defects between processes increases. Particularly, 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 greatly increases the manufacturing cost burden.

First, in the thermal bonding lamination method, it is possible to adhere without bursting in the process of applying heat only by using a very thick film having a thickness of 80 to 100 μm. Therefore, the overall density of the film is increased and the cost of raw materials is also increased, which limits the commercialization.

Second, the method of forming a non-foaming layer by extrusion coating is extremely difficult to coat a film of uniform thickness due to the extremely low melt strength of polyethylene terephthalate resin, and for this reason it is very difficult to lower the extrusion coating thickness to 100 μm or less. . Therefore, high cost becomes a problem, and at the same time, defective losses due to coating thickness non-uniformity are also significant. Particularly, the variation in the thickness of the non-foaming layer occurs in the degree of softening due to heating in the thermoforming process, which leads to a variation in the thickness of the molded article.

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

The present invention aims to solve the following problems.

An object of the present invention is to provide a multi-layer foam sheet comprising a foamed layer and a non-foaming layer prepared in a continuous process.

An object of the present invention is to provide a method of manufacturing a multi-layer foam sheet comprising 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 multi-layered foam sheet comprising a foamed layer and a non-foaming layer produced in a continuous process.

An object of the present invention is to provide a method for producing a foamed molded article produced by processing a multi-layered foam sheet comprising a foamed layer and a non-foaming layer produced in a continuous process.

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

In a polyethylene terephthalate (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 comprising an anhydride functional group 0.1 to 2 parts by weight of the extender is added to the resin to induce the 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 PET non-foaming layer.

PET resin foamed molded article having a three-dimensional shape prepared by processing a PET resin foam sheet having a resin layer having a multi-layer structure according to an embodiment of the present invention, the PET resin foam sheet is heated in an oven of 200 to 350 degrees Celsius 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 after pressing with a molding mold, the crystallinity of the PET resin foam sheet is 10% or more.

The present invention can provide a multi-layer foam sheet comprising a foam layer and a non-foaming layer prepared in a continuous process.

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

The present invention can provide a foamed molded article produced by processing a multi-layered foam sheet comprising a foamed layer and a non-foaming layer prepared in a continuous process.

The present invention can provide a method for producing a foamed molded article manufactured by processing a multi-layered foam sheet comprising a foamed layer and a non-foaming layer produced in a continuous process.

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

Figure 1 shows a process for producing a polyethylene terephthalate resin foam sheet of a two-layer structure according to various embodiments of the present invention.
Figure 2 shows a process for manufacturing a polyethylene terephthalate resin foam sheet of a three-layer structure according to various embodiments of the present invention.
Figure 3 shows a cross-section of a polyethylene terephthalate resin foam sheet of a three-layer structure according to various embodiments of the present invention.
Figure 4 shows a process for 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, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily practice. The present invention can be implemented in many different forms and is not limited to the embodiments described herein.

The present invention relates to a foamed sheet of a multilayer structure polyethyleneterephthalate (PET) resin using a coextrusion foaming method, which is a continuous process, a manufacturing method, a molded article, and a method for manufacturing the molded article. The finished product realized through the present invention is characterized by excellent heat resistance and safety suitable for bowl side containers and disposable food containers, instant food containers, steam ovens, high temperature ovens and heating containers for microwave ovens. In addition, not only the high productivity of the continuous process, but also the low density of the foam layer and the low thickness of the non-foaming layer, the overall raw material cost is low, so commercial competitiveness is high. The excellent oxygen barrier property, which is an intrinsic characteristic of polyethylene terephthalate resin, also 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 unique rheological properties not suitable for foam extrusion due to its low resin viscosity and melt strength. Therefore, it is essential to improve the molecular weight through reaction extruding by adding a chain extender and to modify the polymer structure to attach the long side chain branch to the main chain. However, because of the toxicity of the chain extender, when used as a food container, even a very small amount may be eluted as food, and there is a fear of human effect when used in applications such as heating high-temperature food or microwave heating.

As a method of adding a non-foaming layer to a polyethylene terephthalate resin single-layer foam sheet prepared by an extrusion foaming process, lamination bonding of a non-foaming film and a resin foam sheet, which has already been made, using heat, or resin foam sheet by extrusion coating method A method of coating on top can be considered. However, these methods have a fatal disadvantage. These methods basically require a separate follow-up process to create a multi-layered structure, so the process cost increases rapidly, and the loss due to defects between processes increases. Particularly, 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 greatly increases the manufacturing cost burden.

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

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

Figure 1 shows a process for producing a polyethylene terephthalate resin foam sheet of a two-layer structure according to various embodiments of the present invention. Figure 2 shows a process for manufacturing a polyethylene terephthalate resin foam sheet of a three-layer structure according to various embodiments of the present invention.

Specifically, Figure 1 shows a manufacturing process of a polyethylene terephthalate resin foam sheet composed of two layers prepared in a tandem foam extruder according to various embodiments of the present invention. Figure 2 shows a manufacturing process of a polyethylene terephthalate resin foam sheet composed of three layers prepared in a tandem foam extruder according to various embodiments of the present invention.

1 shows a process for producing a resin foam sheet having a two-layer structure through foam extrusion of a polyethylene terephthalate resin compounded with a functional additive. Figure 2 shows a process for producing a resin foam sheet having a three-layer structure through the foam extrusion of a polyethylene terephthalate resin compounded with a functional additive.

The tandem foam extruder has a structure in which the primary extruders 11 and 21 and the secondary extruders 13 and 23 are continuously connected. In addition, the gas inlet of the blowing agent pumps 12 and 22 is processed so that the blowing agent can be injected in the middle of the primary extruder. Coextrusion dies 14 and 24 are mounted at the end of the tandem foam extruder.

The extruders 17 and 27 for supplying polyethylene terephthalate resin used for the non-foaming layer are directly connected to the body of the coextrusion dies 14 and 24 by connecting pipes. A diverter valve is installed between the connecting pipe and the coextrusion dies 14 and 24 so that a non-foaming layer resin containing no blowing agent is formed on one surface of the foam layer or on both surfaces, respectively. The direction of the flow of the resin can be selected and controlled to form a total of two layers, one layer at a time. Here, the co-extrusion dies 14 and 24 are suitable for the ring-shaped 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 wrapped through a cutter at the end of the mandrel 15 and 25 when passing through the drum-shaped mandrel 15 and 25. . Through the mandrel (15, 25), the surface of the polyethylene terephthalate resin foam sheet becomes smoother, and at the same time, the sheet is effectively cooled in a short period of time, thereby providing sufficient mechanical strength to withstand the tension of the winder. Can be obtained.

After passing through the mandrel (15, 25), a foam sheet 16 of a polyethylene terephthalate resin having a two-layer structure composed 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 composed of two non-foaming layers disposed on each side of each.

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

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

The method of manufacturing a resin foam sheet according to various embodiments of the present invention is a single continuous process, so the processing cost is significantly low, and a high level capable of manufacturing a multi-layer foam sheet containing a non-foaming layer of a thin and uniform thickness of polyethylene terephthalate It has process stability. Polyethylene terephthalate resin and a foaming agent, nucleating agent, chain extender, crystallization accelerator and color pigment are uniformly blended in the foam layer of the multi-layer foam sheet according to various embodiments of the present invention. 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 a coextrusion foaming method according to various embodiments of the present invention, unlike conventional foaming equipment, since a precise coextrusion die is used, two layers (foaming layer-non-foaming layer) or three layers A multilayer foam sheet of (non-foaming layer-foaming layer-non-foaming layer) can be easily produced. 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 thinly below 50 μm, the raw material cost of the entire polyethylene terephthalate multilayer foam sheet is lowered, and one Since it is possible to manufacture a multi-layer foam sheet in a continuous process of, it has an effect of significantly increasing process efficiency and cost competitiveness. Therefore, the method of manufacturing a resin foam sheet according to various embodiments of the present invention has a differentiated manufacturing cost and quality competitiveness compared to a thermal adhesion lamination method or an extrusion coating method.

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

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

The resin foam sheet using the coextrusion foaming method according to various embodiments of the present invention has a foaming ratio of the polyethylene terephthalate foam layer of 2 to 20 times, and an average foaming ratio of the entire multilayer sheet including the non-foaming layer is 1.5 to 18. 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 material as its composition, and preferably, when a physical foaming agent is used, a foaming ratio of 2 to 20 times is obtained. Can be. According to one embodiment, the physical blowing agent is a mixed blowing agent consisting of an inert gas such as carbon dioxide (carbon dioxide), nitrogen (nitrogen) and a hydrocarbon gas (hydrocarbon) such as butane (butane), pentane (pentane), or a combination thereof. Can be used. Addition of the blowing agent should be injected through the primary extruder cylinder 0.1 to 10 parts by weight based on the weight of the resin to be obtained. The polyethylene terephthalate foam layer of the polyethylene terephthalate resin foam sheet according to various embodiments of the present invention is a physical foaming agent by selecting at least one of carbon dioxide, nitrogen, butane, pentane, or a mixture thereof, 0.1 to 10 parts by weight based on the resin weight It can be prepared by kneading.

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

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 mixtures thereof as a nucleating agent. It may be prepared by 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 0.1 to 5 parts by weight of the resin with polyethylene terephthalate resin.

The composition of the non-foaming layer coextruded as a thin film on the surface of the foam layer described above uses polyethylene terephthalate resin as a basic raw material and does not include 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 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 a crystallization accelerator, stearic acid, hydroxystearic acid, ethylenebis stearamide, etc. are suitable.

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

Figure 3 shows a cross-section of a polyethylene terephthalate resin foam sheet of a three-layer structure 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, that is, a non-foaming layer-foaming layer-non-foaming layer, manufactured according to a manufacturing method according to various embodiments of the present invention. Shows an electron microscope picture.

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

Figure 4 shows a process for 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 manufacturing a final desired shape of a finished product by heating a multi-layer polyethylene terephthalate foam sheet fabric according to various embodiments of the present invention and thermoforming it with a molding mold.

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

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

In the thermoforming process, the resin foam sheet is formed into a container or tray having a specific shape by pressing the vacuum forming mold. When heat is applied for a time and a temperature capable of inducing crystallization of a polyethylene terephthalate resin foam sheet in a press-pressed state of a molding mold, the polyethylene terephthalate resin foamed molded article has excellent heat resistance due to a markedly higher crystallinity Can get

The polyethylene terephthalate resin foam sheet having a multilayer structure manufactured according to the method of FIGS. 1 to 2 is wound in a roll 41 and undergoes an aging process of about 3 to 10 days to discharge part of the foaming agent remaining in the foam layer. Is done. That is, the polyethylene terephthalate resin foam sheet having a multilayer structure manufactured by a method according to various embodiments of the present invention should be aged through a degassing step for a predetermined time.

Subsequently, the polyethylene terephthalate resin foam sheet having a multi-layer structure manufactured by a method according to various embodiments of the present invention undergoes a thermoforming process in order to form various molded products such as food containers or trays. At this time, the foam sheet composed of two layers may serve 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 the heating oven 42 to 200 to 350 degrees Celsius to soften to a level capable of deformation. According to one embodiment, a ceramic heater oven may be used as the heating oven. According to one 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 it to have a three-dimensional shape in the form of a container or tray. At this time, the molding mold should 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 the resin foam sheet in 10% or more in a short time. According to one embodiment, the molding mold 43 may be manufactured to have a three-dimensional shape by pressing a 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 cool in a short time, so that the molded product can smoothly exit from the mold.

The molded resin foam sheet is punched by a press trimmer.

The finished final molded product can be used as a container. The structure 44 of the final molded article has a non-foaming layer of polyethylene terephthalate that is safe for direct contact with food on the inner side of the container where food comes into contact.

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

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

Referring to FIG. 5, a cross-sectional structure of a polyethylene terephthalate multi-layer foam sheet and molded products of various shapes are shown.

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

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

The foamed molded article having a multilayer structure of polyethylene terephthalate resin prepared according to various embodiments of the present invention has heat resistance that can be used even in an environment in which high temperature food is stored or heated in a microwave oven without concern for environmental hormones. Since the polyethylene terephthalate non-foaming layer, 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 foamability, and is suitable for various processed food containers or bowl side containers.

In addition, since the inner surface of the food container is formed of a smooth non-foaming layer, it is also possible to cleanly remove residual food and oil components by simply cleaning the water after use as a food container, so it is easy to recycle plastics. Contrast is a big advantage.

Furthermore, because of the excellent oxygen barrier property, which is an inherent property of polyethylene terephthalate resin, when used as a 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 a viewpoint.

Hereinafter, examples 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 uniaxial extruder (primary extruder) and a screw diameter of 130 mm uniaxial extruder (secondary extruder) are continuously connected. In addition, it is a form in which a gas injection port is processed so that a physical blowing agent can be injected in the middle of the primary extruder. A coextrusion die was mounted at the end of the tandem foam extruder. The extruder supplying the resin used for the non-foaming layer is directly connected to the coextrusion die and a connecting pipe. A diverter valve is installed between the connection pipe and the coextrusion die, so that the non-foaming layer resin can be selected to be formed on one or both sides of the foam layer. Here, as the coextrusion die, an annular coextrusion die is suitable to suppress the wrinkle problem of the foam sheet.

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

The multilayer foam sheet obtained through the foam extrusion process consists of a total of two and three layers depending on 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 multi-layer foam sheet was aged for 5 days in a roll state and then subjected to a thermoforming process. After aging, the polyethylene terephthalate resin foam sheet was molded into a bowl surface container 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 proceeded for 20 seconds. Then, the male and female mold molds of 17 cm in diameter and 6 cm in depth were treated to heat the resin foam sheet for about 10 seconds to obtain a crystallinity of polyethylene terephthalate resin of 15% or more, and to produce a thermoformed product with high heat resistance. Did. At this time, the non-foaming layer was disposed inside the container so that the foam layer containing the chain extender was not designed to directly contact hot food.

In the case of the resin foam sheet composed of three layers, since the polyethylene terephthalate non-foaming layer is formed on both surfaces of the foam sheet through the setting of the diverter valve, the inside and outside of the container during molding is irrelevant. In this case, it is easier to match the color of the interior and exterior of the container. The container thus prepared was excellent in heat resistance, so that no deformation occurred when boiling water was poured, and no deformation occurred even in microwave heating. In conclusion, it was possible to manufacture an eco-friendly food container with very good heat resistance and no harm to the human body.

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

In general, the multi-layered polyethylene terephthalate foam sheet in an extruded foam state is not high in crystallinity, so the heat resistance temperature is limited to 70 degrees Celsius. Accordingly, according to various embodiments of the present invention, the crystallinity of the polyethylene terephthalate resin may be maximized by heating the mold temperature of the subsequent thermoforming process to a level of 200 degrees Celsius to obtain a molded article having excellent heat resistance.

According to various embodiments of the present invention, a foamed molded article of polyethylene terephthalate resin having various forms, such as a bowl side container, an instant food container, a lunch tray, and a beverage cup, can be manufactured at a low manufacturing cost and raw material cost. This polyethylene terephthalate resin foam molding container is characterized by excellent heat resistance that can withstand boiling water or microwave heating. In addition, since the inside surface of the container is formed of a smooth non-foaming layer, after use as a food container, it is possible to cleanly remove residual foods and oil components with simple water cleaning, and it is also easier to recycle plastics than conventional polystyrene foam molding containers. It is an advantage.

Furthermore, the foamed molded container of polyethylene terephthalate resin has excellent oxygen barrier property as its unique characteristic compared to foamed products made of polystyrene or polypropylene resin, which are widely used as packaging materials, so processed food storage When used as a container, the contents are not damaged and a long shelf life that can be stored for a long time can be secured.

It will be apparent to those skilled in the art to which the present invention pertains that the present invention may be embodied in other forms without departing from the technical spirit and essential characteristics of the present invention. Accordingly, the above embodiments are to be considered in all respects as illustrative, not restrictive. The scope of rights of the invention should be determined by rational interpretation of the appended claims and all possible changes within the scope of the invention.

11: primary extruder 12: blowing agent pump
13: secondary extruder 14: coextrusion die,
15: Mandrel 16: 2-layer PET resin foam sheet
17: non-foamed PET layer extruder 21: primary extruder
22: blowing agent pump 23: secondary extruder
24: coextrusion die 25: mandrel
26: 3-layer PET resin foam sheet 27: non-foamed PET layer extruder
41: aged resin foam sheet 42: heater oven
43: press molding mold 44: structure of the molded article
51: PET non-foaming layer 52: PET foam layer
53: final molded article

Claims (16)

A polyethylene terephthalate (PET) resin foam sheet provided with a resin layer having a multilayer structure,
The resin layer is made of PET resin, a chain extender containing an anhydride functional group is added to 0.1 to 2 parts by weight based on the weight of the resin to induce reaction extrusion, and a tandem foam compressor equipped with a coextrusion die ( tandem foaming extruder)
The resin layer has a multi-layer structure including at least one PET foam layer and at least one PET non-foaming layer,
PET resin foam sheet.
According to claim 1,
The at least one PET foam layer is foamed 2 to 20 times the volume of the composition before foaming,
PET resin foam sheet.
According to claim 2,
The thickness of the at least one PET foam layer is 1 to 6 mm,
The thickness of the at least one PET non-foaming layer is 5 to 50 μm,
PET resin foam sheet.
According to claim 1,
The at least one PET foam layer and the at least one PET non-foaming layer,
By selecting at least one of stearic acid, hydroxystearic acid, ethylenebis stearamide, or a mixture thereof as a crystallization accelerator, kneading 0.1 to 5 parts by weight based on the resin weight Manufactured,
PET resin foam sheet.
According to claim 1,
The at least one PET foam layer,
Prepared by kneading 0.1 to 10 parts by weight based on resin weight by selecting at least one of carbon dioxide, nitrogen, butane, pentane, or a mixture thereof as a physical blowing agent,
PET resin foam sheet.
According to claim 1,
The at least one PET foam layer,
Prepared by kneading 0.1 to 5 parts by weight based on the weight of the resin by selecting at least one of talc, calcium carbonate, titanium dioxide, or a mixture thereof as a nucleating agent,
PET resin foam sheet.
A PET resin foamed molded article having a three-dimensional shape produced by processing a PET resin foam sheet provided with the resin layer having the multilayer structure of claim 1,
It is manufactured to have the three-dimensional shape by heating the PET resin foam sheet in an oven at 200 to 350 degrees Celsius and then pressing for 3 to 15 seconds with a molding mold heated to 100 to 250 degrees Celsius,
After pressing with the molding mold, the crystallinity of the PET resin foam sheet is 10% or more,
PET resin foam molding.
The method of claim 7,
The PET resin foam molded article has a heat resistance of 120 to 220 degrees Celsius and microwave heating safety,
PET resin foam molding.
As a method for producing a polyethylene terephthalate (polyethyleneterephthalate, PET) resin foam sheet is provided with a resin layer having a multi-layer structure,
A chain extender containing an anhydride functional group is added to the PET resin in an amount of 0.1 to 2 parts by weight based on the weight of the resin to induce reaction extrusion, through a tandem foaming extruder equipped with a coextrusion die. In a continuous process, to prepare the resin layer having a multi-layer structure comprising at least one PET foam layer and at least one PET non-foaming layer,
Way.
The method of claim 9,
The at least one PET foam layer is prepared to foam 2 to 20 times the volume of the composition before foaming,
Way.
The method of claim 9,
The resin layer,
The thickness of the at least one PET foam layer is 1 to 6 mm,
The at least one PET non-foaming layer is prepared to have a thickness of 5 to 50 μm,
Way.
The method of claim 9,
The at least one PET foam layer and the at least one PET non-foaming layer,
By selecting at least one of stearic acid, hydroxystearic acid, ethylenebis stearamide, or a mixture thereof as a crystallization accelerator, kneading 0.1 to 5 parts by weight based on the resin weight Manufactured,
Way.
The method of claim 9,
The at least one PET foam layer,
Prepared by kneading 0.1 to 10 parts by weight based on resin weight by selecting at least one of carbon dioxide, nitrogen, butane, pentane, or a mixture thereof as a physical blowing agent,
Way.
The method of claim 9,
The at least one PET foam layer
Prepared by kneading 0.1 to 5 parts by weight based on the weight of the resin by selecting at least one of talc, calcium carbonate, titanium dioxide, or a mixture thereof as a nucleating agent,
Way.
A method for manufacturing a PET resin foamed molded article having a three-dimensional shape by processing a PET resin foam sheet provided with a resin layer having the multilayer structure manufactured by the method of claim 9,
The PET resin foam sheet is heated in an oven at 200 to 350 degrees Celsius and then pressed for 3 to 15 seconds with a molding mold heated to 100 to 250 degrees Celsius to produce the PET resin molded article to have the three-dimensional shape,
After pressing with the molding mold so that the crystallinity of the PET resin foam sheet is 10% or more,
Way.
The method of claim 15,
The PET resin foam molded article is manufactured to have a heat resistance of 120 to 220 degrees Celsius and microwave heating safety,
Way.

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