KR102560316B1 - Mechanical Recycled PET container and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a method for manufacturing a mechanically recycled PET container comprising manufacturing a preform from mechanically recycled PET material and blowing the preform, and a mechanically recycled PET container manufactured by the manufacturing method.

Description

Mechanical recycled PET container and method for manufacturing the same {Mechanical Recycled PET container and method for manufacturing the same}

The present invention relates to a mechanically recycled PET container and a method for manufacturing the same, and more particularly, to a method of manufacturing a PET container by blowing an injection-molded preform using mechanically recycled PET flakes, that is, a method for manufacturing a PET container by ISBM (Injection Stretch Blow Molding), and a PET container manufactured therefrom.

Plastic recycling methods are largely divided into mechanical recycling and chemical recycling. The mechanical recycling method is to crush, sort, wash and melt waste plastics to make recycled pellets, and the chemical recycling method is to extract raw materials and produce compounds by decomposing the molecular structure of waste plastics through a pyrolysis process, etc. Compared to chemical recycling, the mechanical recycling method has excellent ability to reduce greenhouse gas emissions per ton of PET, and although the recycling process equipment or investment cost is evaluated as low, there is a limitation that only single-component clean waste plastic can be recycled as a raw material, or the quality of recycled plastic is lower than that of plastic produced from crude oil.

(Prior art literature)

(Patent Document 1) Korean Patent Application Publication No. 10-2009-0073567 (2009.07.03)

The present invention is to solve the above conventional problems, and to provide a mechanically recycled PET container capable of providing a mechanically recycled PET container having excellent characteristics while maintaining a mechanical recycling method having advantages over a chemical recycling method, and a method for manufacturing the same.

In order to solve the above problems, a method for manufacturing a mechanically recycled PET container according to an embodiment of the present invention includes manufacturing a preform from mechanically recycled PET material; and blowing the preform.

In the method for manufacturing a mechanically recycled PET container according to an embodiment of the present invention, the manufacturing of the preform includes heating and plasticizing the mechanically recycled PET material, measuring the weight of the mechanically recycled PET material to be introduced into a preform mold, introducing the mechanically recycled PET material having the measured weight into a preform mold and injecting it, and cooling the injected preform in the preform mold.

In the method for manufacturing a mechanically recycled PET container according to an embodiment of the present invention, the temperature of the injection step is in the range of 270 °C to 300 °C.

In the method for manufacturing a mechanically recycled PET container according to an embodiment of the present invention, the temperature of the cooling step is in the range of 5 ° C. or more and less than 10 ° C., and the cooling time is in the range of 0.1 second to 10 seconds.

Another embodiment of the present invention is a mechanically recycled PET container manufactured by the manufacturing method described above.

According to the mechanically recycled PET container and its manufacturing method according to an embodiment of the present invention, a mechanically recycled PET container having excellent mechanical properties such as tensile strength and flexural strength can be provided.

According to the mechanically recycled PET container and the method for manufacturing the same according to an embodiment of the present invention, a mechanically recycled PET container having an excellent appearance regarding transparency can be provided.

According to the mechanically recycled PET container and the manufacturing method according to an embodiment of the present invention, an environmentally friendly mechanically recycled PET container in which the residual amount of harmful substances is reduced can be provided.

On the other hand, the effects of the present invention are not limited to the effects mentioned above, and various effects may be included within a range apparent to those skilled in the art from the contents to be described below.

1 is a schematic view of the injection stretch blow molding used in the present invention.
Figure 2 shows a preform for manufacturing a mechanically recycled PET container according to the present invention.
3 shows a mechanically recycled PET container according to the present invention.

In order to fully understand the present invention and its operational advantages and objectives achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. Like reference numerals in each figure indicate like members.

In general, Injection Stretch Blow Molding (ISBM), a method for manufacturing plastic containers, rapidly cools the molten plastic and then stretches it below the softening temperature to make it thinner. Figures 1 (a) and 1 (b) show ISBM molding methods of a one-step method and a two-step method, respectively. The one-step method in FIG. 1 (a) is a method of immediately injection and blowing after making a preform. On the other hand, the two-step method of FIG. 1 (b) is a method in which preforms are mass-produced in advance using an injection molding machine and then reheated in a blowing machine to form a container, which enables mass production at high speed. The mechanically recycled PET container according to the present invention is manufactured by a two-stage ISBM method capable of mass production compared to the one-stage ISBM method. Hereinafter, the manufacturing method of the mechanically recycled PET container according to the present invention will be described first, and then the characteristics of the PET container manufactured according to the manufacturing method will be described.

A method of manufacturing a mechanically recycled PET container (hereinafter simply referred to as an MR-PET container) includes forming a preform and blowing the preform.

First, the step of molding a preform includes heating and plasticizing a mechanically recycled PET material, for example, a mechanically recycled PET chip or flake, measuring the weight of the mechanically recycled PET material to be introduced into the preform mold, introducing the measured weight of the mechanically recycled PET material into the preform mold and injecting it, and cooling the mechanically recycled PET material in the preform mold. In the present invention, the mechanically recycled PET material for molding the preform preferably means a recycled material containing at least 20% or more mechanically recycled PET material, and virgin PET (virgin PET) material is included in addition to the mechanically recycled PET material. For example, if the mechanically recycled PET material is 25% of the total mechanically recycled PET material content, the remaining 75% is virgin PET material.

The steps of molding these mechanically recycled PET preforms are described with reference to Table 1 below.

division condition Preform injection temperature 270℃ or more and 300℃ or less injection time 5 seconds or more and 20 seconds or less cooling temperature 5℃ or more and less than 10℃ cooling time 0.1 seconds or more and 10 seconds or less Injection speed (multi-stage injection) 10 m/s or more and 30 mm/s or less

Referring to Table 1, the step of injection molding the preform is preferably performed at an injection speed of 10 to 30 m/s for 5 to 20 seconds within a temperature range of 270°C to 300°C. Molding in the form of a preform from a PET material can be effectively performed only when the injection molding temperature is heated within the range of 270° C. to 300° C. for 5 seconds or more and 20 seconds or less.

The cooling temperature and the cooling time are preferably in the range of 0.1 second to 5 seconds at 5° C. or more and less than 10° C., respectively. When the cooling temperature is 10° C. or higher, problems such as non-uniform molding or non-transparent preforms occur, which will be described with reference to FIG. 2 .

The preform obtained according to the conditions of Table 1 is shown in FIG. 2 (a), and it can be seen that the preform in FIG. 2 (a) has particularly good external transparency. On the other hand, FIGS. 2(b) and 2(c) differ from the preform of FIG. 2(a) in that the cooling temperatures are 10° C. and 15° C., respectively, and the other conditions satisfy the injection molding conditions in Table 1. It can be seen that the preform of FIG. 2(b) is defective because it is transparent but the molding is not uniform, and the preform of FIG. 2(c) is opaque and crystallization proceeds, making it defective. As such, during preform injection molding, it is particularly important to control the cooling temperature to 5° C. or more and less than 10° C. rather than the cooling time. In particular, maintaining the cooling temperature at 7° C. to 9° C. is particularly advantageous for crystallization while having a transparent appearance. In order to control the cooling temperature, it is important to ensure that the cooling proceeds smoothly, and the connection between the heat treatment of the core part and the cooling water must be smooth.

In contrast to the conditions in Table 1, when cooling is performed by securing a relatively long cooling time of 20 to 40 seconds while maintaining the cooling temperature at room temperature, not only deformation occurs during extraction, but also defects in which the color of the preform is opaque.

On the other hand, in the case of the cooling time, even though it is relatively less affected by the injection molding conditions of the preform than the cooling temperature, since the cooling time is a factor directly related to productivity, it is advantageous to secure a short cooling time at the cooling temperature. In particular, considering both the productivity and the transparency of the preform and the quality of not being deformed upon taking out, it is preferable to control the cooling time from 0.1 second to 1 second among 0.1 second to 10 seconds.

Next, a step of manufacturing a PET container by blowing the manufactured preform will be described. As an example of the preform being manufactured into a PET container, when a mechanically recycled PET container is manufactured by blowing a mechanically recycled PET 25% preform, the PET container can be manufactured through stretching at the following stretching ratio.

item preform courage elongation ratio blowing area 69mm 176.5mm 156% Bottom width difference 4.73mm 14.7mm 211%

item preform courage elongation ratio blowing area 109.3mm 289.7mm 165% Bottom width difference 6.19mm 22mm 255%

In the case of Table 2, it is the stretching ratio when manufacturing a 500 ml PET container, and in the case of Table 3, it is the stretching ratio when manufacturing a 2 L PET container. Referring to Tables 2 and 3, it can be seen that in the case of mechanically recycled PET of 25%, there is little difference in the stretching ratio compared to manufacturing PET containers from new PET materials.

First, it is preferable to go through a process of preheating by passing through a tunnel type oven immediately before putting the injection-molded preform into a blowing process. In this case, the preheating temperature is particularly preferably set to 90° C. to 100° C. as shown in Table 4 below.

temperature 80℃ 90℃ 100℃ 110℃ result No blowing Good Good Blowing occurs during blowing

Referring to Table 4, the blown container was good when the preheating temperature was 90 ° C to 100 ° C, but blowing was not possible at a preheating temperature lower than the above temperature range, or bursting occurred during blowing at a preheating temperature higher than the above temperature range.

On the other hand, it can be seen that the conditions of pressure and time during blowing the preform for manufacturing mechanically recycled PET containers affect the quality of the PET container as well as the temperature conditions. Referring to Table 5 below, it is preferable to perform blowing under different pressure conditions with primary blowing and secondary blowing as the pressure conditions.

division set value 1st blowing pressure 6-10 bar 1st blowing time 2 seconds or less 2nd blowing pressure 23~40 bar 2nd blowing time 3 to 5 seconds

Referring to Table 5, it is necessary to blow in multiple stages when blowing the preform. On the other hand, if blowing is not performed in multiple stages, problems such as bursting or poor appearance during the blowing process are serious. On the other hand, when blowing in multiple stages, stretching the pressure of 6 to 10 bar for 2 seconds or less as the first preliminary blowing, and then stretching the pressure of 23 to 40 bar for 3 to 5 seconds as the main blowing is preferable to secure both appearance characteristics and physical properties. In particular, in relation to the first and second blowing pressure and time, the present inventors set the pressure of the first preliminary blowing to a range of 25% to 35% of the pressure of the second blowing and set the second blowing time to twice the first preliminary blowing time. In this case, in the case of the first preliminary blowing, as preparation for stretching the preform into a PET container, the pressure of the first preliminary blowing does not need to consider the stretching ratio of the preform and the bottle when substantially setting the pressure. The effect is small, but in the case of the second main blowing pressure, if the target stretching ratio is considered, the ratio of defective products that do not have the appearance characteristics or mechanical properties of mechanically recycled PET containers can be significantly reduced. Specifically, based on 22 bar, when a value obtained by multiplying the stretching ratio (L2/L1), which is the length (L2) of the blowing area of the PET bottle relative to the length (L1) of the blowing area of the preform, is set as the secondary blowing pressure, thickness deviation, transparency, and tensile properties are all within the target range with almost no defective rate. From the secondary blowing pressure set in this way, the primary preliminary blowing pressure is set within the range of 25% to 35% in consideration of process conditions and conditions of production facilities.

3(a) to 3(c) are photographs of actual PET containers for the entirety, bottle neck and lower end of a 2L water bottle composed of 25% mechanically recycled PET and 75% new PET, respectively, and are actual products when the container is manufactured under the conditions of manufacturing the preform and blowing the preform. As can be seen from Figures 3 (a) to 3 (c), the mechanically recycled PET container has excellent appearance including transparency. More specific characteristics of these mechanically recycled PET containers will be described later.

Table 6 below shows the results of the dissolution test of the preform and the container for manufacturing a mechanically recycled PET container according to the present invention.

item unit preform courage [remaining] lead mg/kg 0 0 [Residual] Cadmium mg/kg 0 0 [residual] mercury mg/kg 0 0 [Residual] hexavalent chromium mg/kg 0 0 [Elution] lead mg/L 0 0 [Elution] Consumption of potassium permanganate mg/L 0 0 [Elution] Total amount of elution (water) mg/L 0 0 [Elution] Total amount of elution (4% acetic acid) mg/L 0 0 [Elution] Total amount of elution (n-heptane) mg/L 0 0 [Elution] terephthalic acid (water) mg/L 0 0 [Elution] terephthalic acid (4% acetic acid) mg/L 0 0 [Elution] terephthalic acid (n-heptane) mg/L 0 0

As can be seen from Table 6, both the preform and the mechanically recycled PET container manufactured according to the manufacturing method of the present invention secured stability as food containers.

Table 7 below shows the color value, thickness deviation, and compression load results of the mechanically recycled PET container according to the present invention and the preform provided for its manufacture.

division item result performance indicator preform Color L 93.4 over 68 Color b 1.22 5 or less thickness deviation 0.006 less than 0.1 PET container Color L 95.14 over 68 Color b 0.59 5 or less Top load 50 over 40 N thickness deviation 0.007 0.1 or less

The results of Table 7 are the chromaticity of the preform and the container of 25% mechanically recycled PET obtained through ASTM E1164.

Next, as physical properties of the specimen of the mechanically recycled PET container (25% mechanically recycled PET) according to the present invention, the tensile strength and flexural strength are 54.1 MPa and 87.4 MPa, respectively. It can be seen that the physical properties are substantially equivalent to those of the case where the tensile strength and flexural strength of the 100% new PET container are 66 MPa and 85 MPa, respectively.

Next, the productivity of the mechanically recycled PET container (MR-PET 25%) according to the present invention is shown in Table 8 below.

evaluation items MR-PET 25% container output 10,242 production time 103 minutes 52 seconds production speed Approx. 99/min Production per day (20 hours) 118,800

It can be seen that the productivity in Table 8 is at a similar level compared to the domestic average daily production of 180,000 new PET containers.

As described above, according to the mechanically recycled PET container and its manufacturing method according to the present invention, the physical properties of tensile strength and flexural strength are equivalent to those of the new PET container, and the color is excellent and the thickness deviation is small, so the appearance is equivalent to that of the new PET container. Moreover, even in terms of productivity for mass production, it can be seen that about 99 pieces/minute (118,800 pieces when converted to 20 hours of production per day) of mechanically recycled PET containers are produced.

In the above, the technical idea of the present invention has been described with the accompanying drawings, but this is an illustrative example of a preferred embodiment of the present invention, but does not limit the present invention. In addition, it is obvious that various modifications and imitations can be made by anyone skilled in the art to which the present invention pertains without departing from the scope of the technical idea of the present invention.

Claims (5)

manufacturing a preform from mechanically recycled PET material;
Preheating the preform by passing it through a tunnel oven; and
Including the step of blowing the preheated preform,
Blowing the preheated preform,
A first blowing step of firstly blowing the preheated preform and a second blowing step of secondarily blowing the preform that has passed through the first blowing step,
The pressure applied to the preform in the first blowing step is set to 25 to 35% of the pressure applied to the preform in the second blowing step,
The time for blowing the preform in the first blowing step is set to 2 seconds or less,
The pressure applied to the preform in the second blowing step is a value obtained by dividing the length to be stretched based on the length of the preform before the first blowing step by the length of the preform before the first blowing step, and multiplied by 22 bar.
The time for blowing the preform in the second blowing step is set to twice the time for blowing the preform in the first blowing step. According to claim 1,
The method of manufacturing a mechanically recycled PET container, wherein the step of manufacturing the preform includes the steps of heating and plasticizing the mechanically recycled PET material, measuring the weight of the mechanically recycled PET material to be introduced into a preform mold, introducing the mechanically recycled PET material having the measured weight into a preform mold and injecting it, and cooling the injected preform in the preform mold. According to claim 2,
The temperature of the injection step is in the range of 270 ℃ to 300 ℃, a method for producing a mechanically recycled PET container. The method of claim 2, wherein the cooling temperature ranges from 5° C. to less than 10° C., and the cooling time ranges from 0.1 seconds to 10 seconds. A mechanically recycled PET container manufactured according to any one of claims 1 to 4.

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