Method for manufacturing plastic containers, liquid-filled products, and method for inhibiting antimony leaching from plastic containers

Abstract

To relate to a plastic container capable of suppressing elution of antimony, while containing a polyester resin composition containing a recycled polyester resin.SOLUTION: Disclosed is a plastic container comprising a polyester resin and a polyester resin composition containing an antimony compound. At least a portion of the polyester resin is recycled polyester resin. The polyester resin composition has an intrinsic viscosity of 0.70 dl / g or more and 0.85 dl / g or less, and an L value is 60.0 or more and 90.0 or less according to a color coordinates of the polyester resin composition. A b value is -5.0 or more and 5.0 or less according to the color coordinates of the polyester resin composition. When the intrinsic viscosity is V, and the b value is B, a value X calculated by the formula: X=L4×|B|1 / 4 / (1000000×V4) is 76.3 or more and 167.8 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a plastic container, a method for producing a liquid-filled product, and a method for inhibiting the leaching of antimony from a plastic container. [Background technology]

[0002] BACKGROUND ART Polyester resins (for example, polyethylene terephthalate resins) are widely used as raw materials for containers (for example, bottle containers) that hold liquids such as beverages.

[0003] Antimony compounds used as catalysts in the production of polyester resins may remain in small amounts in the polyester resins, and therefore, methods for preventing antimony from leaking out of polyester resin containers have been investigated (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-20598 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-152250 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of reducing the environmental load, there is a demand for the production of plastic containers using recycled polyester resins. In particular, in recent years, with the enforcement of the Containers and Packaging Recycling Law and the growing momentum toward realizing a society in which plastics are continuously recycled, the reuse of beverage containers (PET bottles) made of polyester resins (mainly polyethylene terephthalate resins) has been considered. However, according to the research of the present inventors, it has become clear that when plastic containers are produced using recycled polyester resins produced using an antimony compound as a catalyst as all or part of the raw materials, antimony tends to be easily eluted from the containers.

[0006] One aspect of the present invention relates to a plastic container that contains a polyester resin composition that contributes to reducing the environmental load by containing recycled polyester resin, and that suppresses the elution of antimony. [Means for solving the problem]

[0007] One aspect of the present invention relates to a plastic container comprising a polyester resin and a polyester resin composition containing an antimony compound. At least a portion of the polyester resin is recycled polyester resin. The polyester resin composition has an intrinsic viscosity of 0.70 dL / g or more and 0.85 dL / g or less, an L value of the color coordinate of the polyester resin composition of 60.0 or more and 90.0 or less, and a b value of the color coordinate of the polyester resin composition of -5.0 or more and 5.0 or less. When the intrinsic viscosity is V, the L value is L, and the b value is B, the formula: X=L 4 ×|B| 1 / 4 / (1000000×V 4 ) is greater than or equal to 76.3 and less than or equal to 167.8.

[0008] According to the findings of the present inventors, in a polyester resin composition exhibiting specific ranges of intrinsic viscosity, L value, and b value, when the value X calculated by the above formula is within the specific range, a plastic container in which antimony elution is effectively suppressed can be obtained. This plastic container is particularly suitable for use as a beverage container and can contribute to reducing environmental impact. The present inventors speculate as follows about the reason for this. First, a high intrinsic viscosity indicates a high entanglement density of the molecular chains of the polyester resin, and it is believed that a high entanglement density of the molecular chains makes it difficult for antimony to leach out of the plastic container. Furthermore, a high proportion of recycled polyester resin tends to increase the intrinsic viscosity. Therefore, a high intrinsic viscosity above a certain level can contribute to both the prevention of antimony leach-out and the reduction of environmental impact. On the other hand, a high L value indicates a high degree of crystallinity of the polyester resin, and it is believed that a high degree of crystallinity makes it difficult for antimony to leach out. Furthermore, a small absolute value of the b value indicates a low degree of hydrolysis of the polyester resin, and it is believed that a low degree of hydrolysis makes it difficult for antimony to leach out. However, a high proportion of recycled polyester resin tends to decrease the L value and increase the absolute value of the b value. Therefore, from the perspective of reducing environmental impact, it is desirable for the L value to be small and the absolute value of the b value to be large. In consideration of these circumstances, both the L value and the b value are set within a predetermined range in order to simultaneously suppress the leach-out of antimony and reduce environmental impact. Here, when the proportion of recycled polyester resin is large, the elution of antimony tends to be suppressed in terms of intrinsic viscosity, but the elution of antimony tends to be difficult to suppress in terms of L value and b value. The value of X is used to determine the antagonism between these tendencies, particularly "(L 4 / V 4 )×|B| 1 / 4 The inventors presume that this is appropriately reflected by the "" part. When the intrinsic viscosity, L value, and b value are each within a predetermined range, and at the same time the value of X is within a predetermined range, it is possible to highly effectively suppress the elution of antimony and reduce the environmental load. In the formula for calculating X, the "1 / 1000000" part is introduced to adjust the number of digits of the value of X.

[0009] Another aspect of the present invention relates to a method for producing a liquid-filled product, which comprises filling the above-described plastic container with a liquid by hot-pack filling.

[0010] Yet another aspect of the present invention relates to a method for suppressing antimony leaching from a plastic container, the method comprising: a polyester resin and a polyester resin composition containing an antimony compound, at least a part of which is recycled polyester resin, the method comprising: a polyester resin composition having an intrinsic viscosity of 0.70 dL / g or more and 0.85 dL / g or less, an L value of the color coordinate of the polyester resin composition of 60.0 or more and 90.0 or less, and a b value of the color coordinate of the polyester resin composition of -5.0 or more and 5.0 or less, wherein when the intrinsic viscosity is V, the L value is L, and the b value is B, the method comprises: 4 ×|B| 1 / 4 / (1000000×V 4 The method includes selecting a polyester resin composition having a value X calculated by the following formula: [Effects of the Invention]

[0011] According to one aspect of the present invention, a plastic container can be provided that contains a polyester resin composition that has a reduced environmental impact due to the inclusion of recycled polyester resin, while suppressing the elution of antimony. The plastic container according to one aspect of the present invention can have good heat resistance. A moderately high intrinsic viscosity can also contribute to improving the dimensional stability of the plastic container. A moderately low intrinsic viscosity contributes to good fluidity of the plastic resin composition, which is particularly advantageous for molding beverage containers that require uniform thickness and smoothness. "Suppressed elution of antimony" means, for example, that the amount of antimony eluted from the plastic container into the liquid filled in the plastic container is less than 0.01 mg / L, as measured by the method described in the Examples below. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0013] An example of a plastic container is a resin molded article formed from a polyester resin and a polyester resin composition containing an antimony compound.

[0014] At least a portion of the polyester resin is recycled. From the viewpoint of reducing environmental impact, the proportion of recycled polyester resin in the polyester resin composition may be 20% by mass or more, more than 50% by mass, or 80% by mass or more, or 100% by mass or less. The recycled polyester resin may be, for example, a recycled product regenerated by mechanical recycling or chemical recycling. The polyester resin may be, for example, a polymer of at least one monomer selected from dimethyl terephthalate, terephthalic acid, dimethyl isophthalate, methyl paratoluate, diethylene glycol, isophthalic acid, and monomethyl terephthalate with a diol compound. Examples of polyester resins include polyethylene terephthalate resin, polybutylene terephthalate resin, and polytrimethylene terephthalate resin. Polyethylene terephthalate resin is particularly suitable for use in beverage containers.

[0015] The antimony content in the polyester resin composition or a plastic container formed therefrom may be 10 ppm by mass or more, 100 ppm by mass or more, 155 ppm by mass or more, or 160 ppm by mass or more, and 500 ppm by mass or less, 400 ppm by mass or less, 300 ppm by mass or less, or 250 ppm by mass or less, based on the mass of the polyester resin composition or the mass of the plastic container. The antimony content can be measured, for example, by a method comprising: dissolving shredded plastic containers in sulfuric acid and nitric acid while heating on a hot plate; adjusting the volume of the resulting solution to 50 mL to prepare a measurement sample; analyzing the measurement sample using an inductively coupled plasma mass spectrometer; and quantifying the antimony based on the analysis results. The total content of polyester resin and antimony in the polyester resin composition or a plastic container formed therefrom may be 80% by mass or more, 90% by mass or more, or 95% by mass or more, or may be 100% by mass or less.

[0016] The polyester resin composition can be selected based on its intrinsic viscosity, L value, and b value in terms of color coordinates. Specifically, the selected polyester resin composition may have an intrinsic viscosity of 0.70 dL / g or more and 0.85 dL / g or less, an L value of 60.0 or more and 90.0 or less, and a b value of -5.0 or more and 5.0 or less. A polyester resin composition that satisfies these requirements can be selected from commercially available products available to those skilled in the art. In this specification, the intrinsic viscosity refers to a value measured by the measurement method described below. The polyester resin composition is dissolved in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 mass%) to prepare a solution containing the polyester resin composition at a concentration of 0.5 wt %. The viscosity of the prepared solution is measured at 30°C using a capillary viscometer according to the method of ASTM D-4603-18 to determine the intrinsic viscosity.

[0017] The L value and b value of a polyester resin composition are measured with a color difference meter using pellets of the polyester resin composition as a measurement sample. The L value represents lightness, with a larger value meaning a brighter color. The b value represents a yellow to blue hue, with + reflecting yellowish color and - reflecting bluish color. The L value and b value may also be measured with a color meter using pellets prepared by processing a plastic container.

[0018] From the viewpoints of suppressing antimony elution and improving the moldability and heat resistance of plastic containers, the intrinsic viscosity of the polyester resin composition may be 0.70 dL / g or more and 0.82 dL / g or less, 0.81 dL / g or less, or 0.80 dL / g or more, 0.75 dL / g or more and 0.85 dL / g or less, 0.82 dL / g or less, 0.81 dL / g or less, or 0.76 dL / g or more and 0.85 dL / g or less, 0.82 dL / g or less, 0.81 dL / g or less, or 0.77 dL / g or more and 0.85 dL / g or less, 0.82 dL / g or less, 0.81 dL / g or less, or 0.80 dL / g or more. When the molecular weight of the polyester resin in the polyester resin composition is high, the intrinsic viscosity tends to be high. Furthermore, as the content of recycled polyester resin in the polyester resin composition increases, the intrinsic viscosity tends to increase.

[0019] From the viewpoints of suppressing antimony elution and heat resistance, the L value of the polyester resin composition may be 60.0 or more and 80.0 or less, or 74.0 or less, or 65.0 or more and 90.0 or less, 80.0 or less, or 74.0 or less, or 66.0 or more and 90.0 or less, 80.0 or less, or 74.0 or less. As the content ratio of recycled polyester resin in the polyester resin composition increases, the L value tends to decrease.

[0020] From the viewpoints of suppressing antimony elution and heat resistance, the b value of the polyester resin composition may be -5.0 or more and 3.5 or less, or 3.3 or less, -3.5 or more and 5.0 or less, 3.5 or less, or 3.3 or less, 0.5 or more and 5.0 or less, 3.5 or less, or 3.3 or less, or 2.0 or more and 5.0 or less, 3.5 or less, or 3.3 or less. The b value tends to increase as the content ratio of recycled polyester resin in the polyester resin composition increases.

[0021] In addition to the intrinsic viscosity, L value, and b value described above, when the intrinsic viscosity of the polyester resin composition is V, the L value is L, and the b value is B, the polyester resin composition satisfies the formula: X=L 4 ×|B| 1 / 4 / (1000000×V 4 ) is 76.3 or more and 167.8 or less. From the viewpoint of suppressing elution of antimony and heat resistance, X may be 76.3 or more and 107.3 or less, or 94.2 or less, or 85.6 or more and 167.8 or less, 107.3 or less, or 94.2 or less, or 81.2 or more and 167.8 or less, 107.3 or less, or 94.2 or less. A polyester resin composition that satisfies the desired requirements for intrinsic viscosity, L value, b value, and X can be selected from commercially available products available to those skilled in the art.

[0022] The elution of antimony from plastic containers can be suppressed by a method including selecting a polyester resin composition that satisfies the requirements for intrinsic viscosity, L value, b value, and X exemplified above, and molding the composition to obtain a plastic container.

[0023] The plastic container can be formed, for example, by blow molding a polyester resin composition. The thickness of the plastic container is adjusted depending on the application, etc. The plastic container may be a beverage container (e.g., a bottle). Here, the beverage container typically has a main body for containing a beverage and a mouth formed by tapering one end of the main body. The main body may be cylindrical or rectangular tubular. If the main body of the beverage container is cylindrical, its diameter may be 5 to 10 cm. If the main body of the beverage container is rectangular tubular, its side length may be 5 to 10 cm. The thickness of the main body of the beverage container may be 0.2 to 0.4 mm. The mouth of the beverage container may have an outer diameter of 2 to 4 cm and a thickness of 0.1 to 1 cm. The height of the plastic container is, for example, 10 to 30 cm. Due to its excellent heat resistance, the plastic container may be used as a container for hot pack filling (particularly, a beverage container for hot pack filling). Hot pack filling is a filling method that involves filling a plastic container with a liquid at a high temperature (e.g., 65 to 95°C). After filling, the plastic container is often immediately cooled, for example, by a cold water shower. Various liquid-filled products, such as beverages, can be produced by a method that involves filling a plastic container with a liquid product, such as a beverage, by hot pack filling or the like. [Example]

[0024] The present invention is not limited to the following examples. 1. Polyester resin composition Recycled resins A, B, and C containing recycled polyethylene terephthalate resin were prepared as polyester resin compositions, each having the intrinsic viscosity, L value, and b value shown in Table 1. The proportion of recycled material in the polyester terephthalate resin exceeded 50 mass% for recycled resins A and C, and was 20 mass% or more and 50 mass% or less for recycled resin B. For comparison, a virgin resin containing only non-recycled polyethylene terephthalate resin was also prepared.

[0025] 2. Bottle containers Each polyester resin composition was molded at a molding temperature of 280°C using a blow molding machine manufactured by Nissei ASB Co., Ltd. to produce a bottle container with a capacity of 500 mL (20°C serving capacity) and a mouth that can be fitted with a cap. 3. Evaluation Antimony elution The soft drink was filled into the bottles by hot pack filling. The bottles filled with the soft drink were kept at 60°C for two weeks. The antimony concentration in the soft drink removed from the bottles was then measured by hydride generation atomic absorption spectrometry. The antimony elution was evaluated based on the measured concentration (amount of antimony elution) according to the following criteria. OK: Less than 0.01 mg / L NG: 0.01mg / L or more

[0026] heat resistance The bottle was filled with 500 mL of pure water at 90°C. A polypropylene cap with an outer diameter of 30 mm, an inner diameter of 26 mm, and a height of 20.1 mm was then tightly fitted to the mouth of the bottle to seal it. The inner surfaces of the bottle and cap were heat-sterilized at 83°C for 30 seconds using a cap inversion sterilizer (Shibuya Machinery Co., Ltd., model number: IZN1250U) with the bottle in a sideways position. The bottle was then observed, and its heat resistance was evaluated according to the following criteria. OK: There was no deformation of the bottle container and no leakage of pure water from the cap. NG: The bottle container was deformed or pure water leaked from the cap.

[0027] [Table 1]

[0028] The evaluation results are shown in Table 1. It was confirmed that the bottle containers produced using the polyester resin compositions of Examples 1 and 2 had good heat resistance and also inhibited the elution of antimony.

Claims

1. A plastic container comprising a polyester resin and a polyester resin composition containing an antimony compound, At least a portion of the polyester resin is a recycled polyester resin, The intrinsic viscosity of the polyester resin composition is 0.75 dl / g or more and 0.82 dl / g or less, the L value of the polyester resin composition according to color coordinates is 65.0 or more and 80.0 or less, the b value of the color coordinates of the polyester resin composition is −3.5 or more and 3.5 or less, When the intrinsic viscosity is V, the L value is L, and the b value is B, the formula: X = L 4 ×|B| 1 / 4 / (1000000 x V 4 ) The value X calculated by the above method is 85.6 or more and 94.2 or less.

2. 10. The plastic container of claim 1, which is a hot pack filling container.

3. A method for producing a liquid-filled product, comprising filling the plastic container of claim 1 or 2 with a liquid by hot-pack filling.

4. A method for suppressing antimony elution from a plastic container, comprising: selecting a polyester resin composition containing a polyester resin and an antimony compound, wherein at least a portion of the polyester resin is recycled polyester resin; and molding the polyester resin composition to obtain a plastic container, the method comprising: The method comprises: When the intrinsic viscosity of the polyester resin composition is 0.70 dl / g or more and 0.85 dl / g or less, the L value of the polyester resin composition according to the color coordinate is 60.0 or more and 90.0 or less, and the b value of the polyester resin composition according to the color coordinate is −5.0 or more and 5.0 or less, and the intrinsic viscosity is V, the L value is L, and the b value is B, the formula: X=L 4 ×|B| 1 / 4 / (1000000 x V 4 The method includes selecting a polyester resin composition having a value X calculated by the above formula (1) above, which is 76.3 or more and 167.8 or less.

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