KR20230060761A - Manufacturing method of container using polyester resin foam - Google Patents

Abstract

The present invention relates to a method for manufacturing a container using a polyester foam, including: a foam sheet step of manufacturing a polyester foam sheet to have a thickness of 30 to 50 % of the set thickness of the container by extruding and foaming a polyester resin containing inorganic particles; and a container molding step of preheating the extruded polyester foam sheet to induce post-foaming in a container molding mold and molding the container to have a set thickness.

Description

Container manufacturing method using polyester foam {MANUFACTURING METHOD OF CONTAINER USING POLYESTER RESIN FOAM}

The present invention relates to a method for manufacturing a container using a polyester foam, and relates to a method for manufacturing a container using a polyester foam, which increases price competitiveness by lowering the weight of the container and has excellent recyclability.

Generally, products used as food containers are divided into foam type and non-foam type. Foaming products are products made by mixing polystyrene with foaming gas and extruding it. The most commonly used fields are food trays containing vegetables and meat, and insulated containers containing delivered food. It has the advantage of high price competitiveness because it is used, but has the disadvantage of being vulnerable to impact and being easily damaged by external forces and concerns about the generation of harmful substances. In the case of a non-foaming container, a product made in the form of a polypropylene film is used through molding, which has the advantage of shape stability and no harmful substances being detected, but has the disadvantage of being expensive and poor insulation.

In modern society, the use of disposable containers and the demand for delivery containers are gradually increasing due to the convenience of life, and accordingly, the demand for food packaging containers is also increasing. New containers that are safe from harmful substances and have improved stability against damage due to usage As consumer demand for materials is growing, research on disposable packaging containers that have convenience, stability in use, and eco-friendly performance is required.

Recently, a food container using a polyester foam having excellent recyclability has been developed rather than a food container using polystyrene, which generates harmful substances.

Republic of Korea Patent Registration No. 2160454 relates to a foam sheet with excellent heat resistance, a method for producing the same, and a food container including the same, and a plan to significantly improve the heat resistance of the foam sheet by containing calcium carbonate, an inorganic particle, has been proposed.

The food container manufactured by the above method does not generate harmful substances and is superior in safety and recyclability to conventional food containers made of polystyrene, but the manufacturing cost is high, so it is difficult to replace food containers using polystyrene.

The present invention was invented to solve the problems of the prior art as described above, and the weight of the container by using the post-foaming characteristics of the polyester foam sheet, which has stability against impact and external force by utilizing polyester, and hardly generates harmful substances. It is an object of the present invention to provide a method for manufacturing a container using a polyester foam having excellent price competitiveness by significantly lowering the

In addition, an object of the present invention is to provide a method for manufacturing a container using a polyester foam containing an inorganic resin and having excellent heat resistance.

The present invention foam sheet step of producing a polyester foam sheet to have a thickness of 30 to 50% of the set thickness of the container by extruding and foaming the polyester resin containing inorganic particles; Provided is a container manufacturing method using a polyester foam, comprising a container molding step of preheating an extruded polyester foam sheet to form a container to have a set thickness while inducing post-foaming in a container molding mold.

In addition, the inorganic particles provide a method for manufacturing a container using a polyester foam, characterized in that it is contained in an amount of 0.5% to 5% by weight.

In addition, the density of the polyester foam sheet provides a container manufacturing method using a polyester foam, characterized in that 120 ~ 250kg / ㎥.

In addition, the polyester resin provides a method for manufacturing a container using a polyester foam, characterized in that it includes a recycled polyester resin.

In addition, in the container molding step, the surface temperature of the polyester foam sheet is preheated from the holding transition temperature (Tg) of the polyester resin to the crystallization temperature (Tc). .

In addition, it provides a container manufacturing method using a polyester foam, characterized in that the surface temperature of the polyester foam sheet is preheated to 60 ~ 160 ℃ in the container molding step.

In addition, it provides a container characterized in that produced by the above manufacturing method.

As described above, the container manufacturing method using the polyester foam according to the present invention has an effect of manufacturing a container with excellent price competitiveness by dramatically lowering the weight of the container by using the post-foaming property of the polyester foam sheet.

In addition, there is an effect of manufacturing a container having excellent heat resistance by containing an inorganic resin.

In addition, by using polyester, there is almost no generation of harmful substances as well as stability against impact and external force, and there is an excellent effect of eco-friendliness due to excellent recyclability.

Hereinafter, preferred embodiments of the present invention will be described in detail. First of all, in describing the present invention, detailed descriptions of related known functions or configurations are omitted in order not to obscure the gist of the present invention.

As used herein, the terms 'about', 'substantially', and the like are used in a sense at or approximating that number when manufacturing and material tolerances inherent in the stated meaning are given, and are intended to convey an understanding of the present invention. Accurate or absolute figures are used to help prevent exploitation by unscrupulous infringers of the disclosed disclosure.

The present invention relates to a method for manufacturing a container using a polyester foam, and manufactures a container including a foam sheet step and a container molding step.

The foam sheet step is a step of manufacturing a polyester foam sheet by extruding and foaming a polyester resin containing inorganic particles, wherein the polyester foam sheet is prepared to have a thickness of 30 to 50% of the set thickness of the container. This is the manufacturing stage.

The polyester foam sheet is formed to a set thickness through post-foaming in the container forming step, and the container using the polyester foam has a lower density than the polyester foam sheet.

The density of the polyester foam sheet is preferably 120 ~ 250 kg / m 3, and if the density of the polyester foam sheet is less than 120 kg / m 3, the density of the container may be too low to satisfy the physical properties suitable for the container. When the density of the ester foam sheet exceeds 250 kg/m 3 , the density of the container may increase too much and the hard material properties may deteriorate, and the density of the container may become overcrowded, resulting in deterioration in physical properties.

In the present invention, the polyester resin may include a repeating unit derived from an acid component and a diol component. Specifically, the polyester resin may be at least one selected from the group consisting of aromatic and aliphatic polyester resins synthesized from a dicarboxylic acid component and a glycol component or hydroxycarboxylic acid.

The polyester resin may be, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly lactic acid (PLA), polyglycolic acid (PGA) , Polyethylene adipate (PEA), polyhydroxyalkanoate (Polyhydroxyalkanoate, PHA), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (Polyethylene naphthalate, PEN) may be at least one selected from the group consisting of there is. Specifically, in the present invention, polyethylene terephthalate (PET) may be used.

In addition, the polyester resin may use a recycled polyester resin to increase eco-friendliness.

In the case of using the recycled polyester resin, a recycled polyester resin and a new polyester resin may be mixed and used, and it may be manufactured using only the recycled polyester resin.

The melting point of the polyester resin is preferably 250 to 280 ° C, more preferably 252 ° C to 260 ° C.

The inorganic particles may be at least one selected from the group consisting of calcium carbonate (CaCO ₃ ), titanium oxide (TiO ₂ ), talc, silica, and zirconium oxide (ZrO ₂ ). For example, the inorganic particles may be amorphous calcium carbonate (CaCO ₃ ). By including the inorganic particles as described above, the food container molded through the present invention can have a uniform surface and exhibit excellent heat resistance.

The content of the inorganic particles is preferably 0.5 to 5% by weight, more preferably 0.5 to 3.0% by weight.

In the manufacture of the foam sheet according to the present invention, the polyester resin introduced into the extruder is melted and extruded and foamed to produce a foam sheet.

Specifically, polyester resin chips containing calcium carbonate may be melted to form a melt, followed by extrusion foaming. For example, the process of melting the polyester resin may be performed at a temperature of 260 °C to 300 °C.

The foaming process can be performed using various types of extruders. The extrusion foaming can simplify the foaming process by continuously extruding and foaming the resin melt, mass production is possible, and it is possible to implement better flexural strength and compressive strength by preventing cracks and granular destruction through a cooling process after foaming. there is.

It is preferable that the foam sheet according to the present invention is a foam sheet exhibiting a thickness deviation of 12% or less per unit area of 100 cm 2 .

The foam sheet according to the present invention may have barrier performance, hydrophilic function, or waterproof function, and may include surfactants, hydrophilic agents, heat stabilizers, waterproofing agents, cell size expanding agents, infrared attenuators, plasticizers, and fire retardant chemicals. , It may further include one or more functional additives selected from the group consisting of a pigment, an elastic polymer, an extrusion aid, an antioxidant, an antistatic agent, and a UV absorber. Specifically, the resin foam sheet of the present invention may include a thickener, a heat stabilizer and a foaming agent.

The thickener is not particularly limited, but in the present invention, for example, pyromellitic dianhydride (PMDA) may be used.

The thermal stabilizer may be an organic or inorganic phosphorus compound. The organic or inorganic phosphorus compound may be, for example, phosphoric acid and its organic ester, phosphorous acid and its organic ester. For example, the heat stabilizer is a commercially available material and may be phosphoric acid, an alkyl phosphate or an aryl phosphate. Specifically, in the present invention, the thermal stabilizer may be triphenyl phosphate, but is not limited thereto, and any material capable of improving the thermal stability of the resin foam sheet may be used without limitation within a typical range.

Examples of the blowing agent include physical blowing agents such as N ₂ , CO ₂ , Freon, butane, pentane, neopentane, hexane, isohexane, heptane, isoheptane, and methyl chloride. Specifically, in the present invention, butane may be included. can

The container forming step is a step of forming a container while inducing post-foaming by preheating the extruded polyester foam sheet.

The container forming step according to the present invention includes preheating the foam sheet, deforming the sheet into a desired shape through a step of pulling the foam sheet in a vacuum or pressing it using pressure, and cooling the sheet after the shape is completed. consists of

Specifically, the preheating temperature in the preheating step is preferably between the holding transition temperature (Tg) and the crystallization temperature (Tc) of the polyester resin, and by heating the foam sheet using a contact or non-contact heater, the surface temperature of the foam sheet is reduced to a glass transition. It is heated above the temperature (Tg).

At this time, when the surface temperature of the foam sheet reaches the glass transition temperature (Tg) or higher due to the heated heat, secondary foaming (hereinafter referred to as post-foaming) additionally occurs inside the sheet. It can appear differently depending on the severity.

The post-foaming occurs most stably between the glass transition temperature (Tg) and below the crystallization temperature (Tc), and when heated and maintained above the crystallization temperature (Tc), crystallization proceeds rapidly in the sheet, rather than forming During the process, the foam sheet becomes too hard, which may interfere with molding.

The polyester resin generally has a glass transition temperature (Tg) of about 60 ° C and a crystallization temperature (Tc) of about 160 ° C. It is preferable to preheat the surface temperature of the foam sheet to 60 to 160 ° C. in the container molding step.

The thickness of the foam sheet according to the present invention increases from 100% to a maximum of 300% compared to the thickness of the sheet before initial heating due to post-foaming when the surface temperature of the foam sheet reaches from 60 ° C or more to 160 ° C or less after contact or non-contact heating. can know,

Specifically, the foam sheet of the container may have a post-foaming rate of 100 to 300% when the surface temperature of the foam sheet after contact or non-contact heating is 60 to 160 ° C.

In the container manufacturing method using the polyester foam according to the present invention, the density of the container is lowered while the container is formed to a set thickness through post-foaming in the container molding step.

The density of the container is preferably 50 ~ 150 kg / m 2, and if the density of the container is less than 50 kg / m 2, the physical properties of the container may be lowered and the use may be limited, and if the density on the container exceeds 150 kg / m 2, overcrowding The physical properties of the container may be deteriorated due to

It is more preferable that the container has a density of 60 to 120 kg/m 2 .

Hereinafter, the present invention will be described in more detail by examples and experimental examples. However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following Examples and Experimental Examples.

Example 1

1.0% by weight of calcium carbonate and a polyethylene terephthalate resin having a melting point of 254 ° C were mixed, and based on 100 parts by weight of the polyethylene terephthalate resin, 0.5 parts by weight of pyromellitic dianhydride and 0.1 part by weight of Irganox (IRG 1010) were mixed, A resin melt was prepared by heating to 280°C.

Then, 1.5 parts by weight of butane as a foaming agent was added to the first extruder based on 100 parts by weight of polyethylene terephthalate (PET) resin and extruded and foamed. did

The prepared foam sheet was preheated in the preheating zone using upper and lower electric heaters at 350℃/250℃, respectively, for a residence time of 10 seconds, so that the surface temperature of the polyester foam sheet reached 60 After heating the sheet and inducing post-foaming so that molding can be performed at a temperature above ℃, the preheated sheet is vacuum/suctioned under the condition of a mold temperature plug of 60℃, a mold of 60℃, and a gap between the upper and lower molds of 2.5mm. After contacting the mold with a plug, a food container was prepared by pressing for 10 seconds.

Example 2

It was prepared in the same manner as in Example 1, but after extrusion foaming, the foam sheet was made of a polyester foam sheet having a density of 200 kg/m3 and a thickness of 1.5 mm to prepare a food container.

Example 3

It was prepared in the same manner as in Example 1, but after extrusion foaming, the foam sheet was made of a polyester foam sheet having a density of 250 kg/m3 and a thickness of 1.2 mm to prepare a food container.

Comparative Example 1

It was prepared in the same manner as in Example 1, but after extrusion and foaming, the foam sheet was made of a polyester foam sheet having a density of 150 kg/m3 and a thickness of 2.5 mm to prepare a food container.

Comparative Example 2

It was prepared in the same manner as in Example 1, but after extrusion foaming, the foam sheet was made of a polyester foam sheet having a density of 300 kg/m3 and a thickness of 2.5 mm to prepare a food container.

* In molding into a food container according to the present invention, the density and thickness of the molded products manufactured in Examples 1 to 3 and Comparative Examples 1 and 2 were compared before and after molding to prevent post-foaming from the foam sheet during the heat treatment process. The level was confirmed, and it is shown in Table 1.

On the other hand, in order to evaluate the quality of the molded article, the bending moldability, thickness deviation, and tear strength of the molded article manufactured through Examples 1 to 3 were measured and shown in Table 2.

1) Density

Density was measured under KS M ISO 845 conditions.

2) Bending stability

In order to evaluate the appearance quality of the molded product, the degree of matching with the curved part of the mold was visually compared and evaluated according to the following criteria.

- 1 to 3 points: The curved part of the molded foam sheet does not match the curved part of the mold

- 4~7 points: The curved part of the molded foam sheet and the curved part of the mold machine are similar but not uniform

- 8~10 points: The curved part of the molded foam sheet and the curved part of the mold machine are almost identical.

3) Thickness deviation

As for the thickness deviation of the molded product, the deviation level was calculated by measuring the thickness of five randomly selected areas on the side and bottom surfaces.

4) Tear strength

The tear strength was measured by making a knife flaw on the side of the molded container and using a tensile strength tester to measure the maximum load until the tear occurred when pulled at a test speed of 50 mm/min.

item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 before plastic surgery Density (kg/㎥) 150 200 250 150 300 Thickness (mm) 1.5 1.5 1.2 2.5 2.5 After molding Density (kg/㎥) 60 90 120 148 285 Thickness (mm) 2.5 2.5 2.5 2.6 2.8

Looking at the results of Table 1, the polyester foam sheets corresponding to Examples 1 to 3 have a thickness of 2.5 mm, which is the same as the distance between the upper and lower molding molds, due to sufficient post-foaming during the stay in the preheating process, but the density is higher than that of the initially introduced sheet. From a high of 2.5 times reduction (Example 1) to a minimum of about 2 times reduction (Example 3), it can be seen that the density of the initially introduced sheet is reduced due to post-foaming due to expansion of the inner cell during the preheating process. there is. That is, in the case of Example 1, it seems that the final thickness was adjusted by the mold gap used during the molding process after 250% or more was expressed during the preheating process.

In Comparative Examples 1 and 2, post-foaming was developed as in Example, but the processed thickness of the mold and the thickness of the foam sheet were the same, so the actual density of the container did not change significantly, and the thickness of the container was slightly changed due to post-foaming after molding. A growing phenomenon has occurred.

item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 molding
quality bending molding
Stability (Points) 9 8 7 4 3 Thickness deviation (%) 4 3 5 7 9 Tear strength (g) 94 106 88 45 39

As shown in Table 2, which shows the quality evaluation results of molded products, in Comparative Examples 1 and 2, the density of the polyester foam sheet and the molded container are almost similar, and it can be seen that the bending stability is lowered and the thickness deviation is increased due to post-foaming. The container, which is a molded article of Examples 1 to 3, has a constant thickness due to post-foaming in the polyester foam sheet, and the thickness deviation is less than 5%, including results that are almost identical to the bending part of the mold even in bending stability. It can be seen that the molding quality is very good.

In addition, in Comparative Examples 1 and 2, it can be seen that the physical properties of the container are lowered due to the overdensity due to post-foaming and the tear strength is lowered, but the density of the molded products of Examples 1 to 3 is 60 to 120 kg / ㎥ It can be seen that is excellent.

Claims (7)

A foam sheet step of producing a polyester foam sheet to have a thickness of 30 to 50% of the set thickness of the container by extruding and foaming a polyester resin containing inorganic particles;
A container manufacturing method using a polyester foam comprising a container molding step of preheating the extruded and foamed polyester foam sheet to induce post-foaming in a container molding mold and molding the container to have a set thickness.
According to claim 1,
The inorganic particles are container manufacturing method using a polyester foam, characterized in that contained 0.5% by weight to 5% by weight.
According to claim 1,
Container manufacturing method using a polyester foam, characterized in that the density of the polyester foam sheet is 120 ~ 250 kg / ㎥.
According to claim 1,
The polyester resin is a container manufacturing method using a polyester foam, characterized in that it comprises a recycled polyester resin.
According to claim 1,
Container manufacturing method using a polyester foam, characterized in that the surface temperature of the polyester foam sheet in the container molding step is preheated between the holding transition temperature (Tg) and the crystallization temperature (Tc) of the polyester resin.
According to claim 1,
Container manufacturing method using a polyester foam, characterized in that the surface temperature of the polyester foam sheet is preheated to 60 ~ 160 ℃ in the container forming step.
A container characterized in that it is manufactured by the manufacturing method of any one of claims 1 to 6.