JP2007111886A - Preform sterilizing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preform sterilizing method capable of performing the sterilization treatment of a preform in a short time and having no remaining fear of a sterilant. <P>SOLUTION: The PET preform 1 is subjected to steam sterilization in an inverted posture wherein its mouth part 2 is turned downward. In this case, the steam sterilization is performed by injecting steam to the inner surface 1a of the preform 1. The sterilizing condition of the preform 1 is set so that the inner surface 1a of the preform 1 is held to a temperature higher than the glass transition temperature of the preform 1 for a predetermined time and the outer surface 1b of the preform 1 is held to a temperature lower than the glass transition temperature. Next, aseptic air is ejected using a common nozzle pipe 3 immediately after the completion of steam sterilization to remove water from the preform 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a preform sterilization method.

  Beverages such as fruit juice drinks, coffee, soft drinks, and mineral water are generally provided to consumers by filling plastic containers represented by PET bottles. Recently, plastic containers have been molded from preforms in the same facility, and beverages are being filled into the molded plastic containers. FIG. 1 is a process diagram from filling a preform into a plastic container and capping the contents. Referring to FIG. 1, the preform is formed into the shape of a container by blow molding after heating it to a formable state. The molded plastic container is subjected to washing and sterilization processes, filled with a beverage such as mineral water, and then sealed with a cap.

  Since the preform is generally supplied from the packaging material manufacturer in an unsterilized state, the preform is sterilized as a preparatory step before forming the preform. With respect to this sterilization, Patent Document 1 discloses a conventional sterilization method in which a preform is immersed in a sterilization liquid and dry heated air is blown onto the preform pulled up from the sterilization liquid. A sterilization method in which ozone gas or the like is brought into contact with the preform is proposed, and this sterilization method insists on the advantage that a step of removing the sterilizing liquid is unnecessary.

Patent Document 2 describes that after a preform is manufactured, the preform immediately after molding is in a high temperature state until the preform is blow molded, that is, during storage of the preform. In this case, it is proposed that the sealing is performed, and a sterilizing agent is added to the preform after molding to sterilize the interior and then the sealing is performed.
JP 2001-212874 A JP-A-9-136350

  As pointed out in Patent Document 1, when the preform is immersed in a sterilizing liquid, if the subsequent liquid removal is incomplete, the probability that a defective product will occur in the plastic container made from this preform increases. . Moreover, when sterilizing using the hydrogen peroxide gas etc. which patent document 1 proposes, the possibility that hydrogen peroxide will remain in a preform cannot be denied.

  In addition, when the preform is sealed as in Patent Document 2, a process of removing the sealing plug from the preform is required before the plastic container is molded from the preform, which is not preferable from the viewpoint of work efficiency.

  An object of the present invention is to provide a preform sterilization method that can be sterilized in a short time and does not have a risk of the sterilizing agent remaining.

According to the present invention, the above technical problem is
A step of sterilizing the preform in a series of steps of filling the plastic container with a beverage after molding the plastic container from the preform;
The step of sterilizing the preform includes a steam sterilization step of spraying water vapor toward the inner surface of the preform,
In the steam sterilization step, the temperature of the outer surface of the preform is maintained at a temperature lower than the glass transition temperature of the preform material, while the temperature of the inner surface of the preform is the glass transition temperature of the preform material. This is achieved by providing a preform sterilization method characterized in that it is executed under the condition that the above temperature is continued for a predetermined time.

  That is, according to the present invention, there is no possibility that the disinfectant remains due to sterilization using water vapor, but the outer surface of the preform is sandwiched between the glass transition temperature of the plastic material of the preform. Since the temperature is lower than the glass transition temperature, even if the inner surface of the preform is steam-heated to a temperature equal to or higher than the glass transition temperature, the initial sterilization is performed without any risk of deformation of the preform. be able to. Since the time satisfying the sterilization condition set by the present invention is relatively short, the preform can be sterilized in a short time.

  In a preferred embodiment of the present invention, immediately after the steam sterilization step, a water removal step of removing water by injecting gas toward the inner surface of the preform is further included. According to this, since water removal is performed immediately after steam sterilization of the inner surface of the preform, an increase in the moisture content of the preform accompanying steam sterilization can be suppressed, and therefore molding when molding a plastic container thereafter. It is possible to prevent inhibition of sex.

  In the water removal step, the water vapor adhered to the inner surface of the preform can be accurately discharged to the outside by moving the nozzle tube for removing the inner surface of the preform relatively. By spraying the water vapor on the inner surface of the preform using the nozzle tube for performing water removal, the apparatus for performing water vapor sterilization of the preform and water removal immediately thereafter can be simplified. And the subsequent water removal step, the change in the moisture content of the preform can be suppressed. Of course, the nozzle tube for removing water and the nozzle tube for injecting water vapor into the preform may be constituted by different nozzle tubes.

  Further, in the steam sterilization process and the water removal process of the preform, it is preferable to perform the preform in an inverted posture with the mouth portion of the preform facing down, which is a posture of the preform excellent in drainage performance during the steam sterilization and water removal. .

  The preferred embodiments of the present invention will be described below. FIG. 1 is a flowchart showing the working process of the embodiment. In the preform sterilization method of the embodiment, the preform is sterilized using water vapor just before molding a plastic container from the preform. This preform sterilization method is typically applied to the molding of PET bottles. The PET bottle blow-molded after applying this preform sterilization method is preferably filled with a beverage that does not contain protein such as mineral water, fruit juice beverage, and carbonated beverage.

  Referring to FIG. 3, the preform 1 is held in an inverted state with the mouth portion 2 facing downward in the sterilization process, and a nozzle tube 3 extending in the vertical direction is inserted from the mouth portion 2 of the preform 1, The tube 3 is positioned in a state where the upper end of the tube 3 is positioned in the vicinity of the top 3 of the preform 1.

  That is, the nozzle tube 3 is formed of an elongated bottomed tube, and the upper end of the nozzle tube 3 is closed. The nozzle tube 3 is arranged in a vertically standing state with the closed upper end 3a facing upward, and the nozzle tube 3 and the preform 1 are aligned with each other in a state where the axis of the nozzle tube 3 coincides with the axis of the preform 1 The preform 1 is inserted into the tube 3 or the nozzle tube 3 is lowered relative to the fixed preform 1 and positioned in the state shown in FIG.

  The nozzle tube 3 is provided with a plurality of small holes 4 at the upper end portion 3 a and the tip end portion 3 b, and normal-pressure water vapor is supplied to the nozzle tube 3, and the water vapor passes through the small holes 4 to perform the preform 1. It is injected into the inside. What is necessary is just to determine the small hole 4 of the nozzle tube 3 by experiment so that the inner surface 1a of the preform 1 can be heated uniformly.

  The sterilization process of the preform 1 includes a first process in which atmospheric pressure steam is injected through the nozzle tube 3 to heat the inner surface 1a of the preform 1, and air is injected through the nozzle tube 3 to remove the inner surface 1a of the preform 1. It is preferable to move the nozzle tube 3 up and down relatively with respect to the preform 1 while ejecting air through the nozzle tube 3 in the water removal of the second step. . Thus, the water can be accurately removed from the inner surface 1a of the preform 1 by injecting the gas toward the inner surface 1a of the preform 1 while relatively moving the nozzle tube 3 up and down. In addition, instead of air, the inner surface 1a of the preform 1 can be obtained at a relatively low price, such as nitrogen gas, without causing harm to the human body or changing the beverage taste. Gas may be used.

  The sterilization process using water vapor and the subsequent water removal process using gas such as air may be performed using the common nozzle tube 3 as described above. You may make it perform a water removal process using another nozzle pipe. In this case, the sterilization process and the water removal process may be performed at the same station, but the sterilization process is performed at another station, that is, the first station, and the next second station adjacent to the first station. A water removal step may be performed.

  The heating condition of the preform 1 is set in consideration of the glass transition temperature at which the material (PET) of the preform 1 starts to soften. That is, on the condition that the outer surface 1b of the preform 1 does not exceed the glass transition temperature, the state where the temperature of the inner surface 1a of the preform 1 is higher than the glass transition temperature is set to a minimum or the outer surface of the preform 1. It is set so that 1b continues for a predetermined time in a range not exceeding the glass transition point.

  The sterilization time varies depending on the sterilization target, but is obtained by the following formula.

Fr = Fi × 10 ^{− {(Tr-Ti) / Z}}

  Here, Fr is the sterilization time, Fi is the basic sterilization time (seconds), Tr is the sterilization temperature to be performed, Ti is the basic temperature to be performed, and the Z value is 1/10 of the sterilization time. This is the temperature required to For example, Z = 5 ° C. is a temperature at which the same sterilization effect can be obtained even if the sterilization time is shortened to 1/10 if the temperature is increased by 5 ° C. In addition, it is said that Z = 5 ° C. for mold and yeast.

For example, if the sterilization conditions for mold and yeast are 65 ° C. × 10 minutes (600 seconds), the sterilization temperature to be carried out is calculated as 85 ° C. based on the above formula,
Fr = 600 × 10 ^{− {(85-65) / 5}}
= 600/10 ⁴
= 0.06 (seconds).

  In the experiment, normal pressure steam at about 100 ° C. was used to inject through the small hole 4 for 2 seconds (the amount of steam was about 3 kg / h), and immediately after that, sterilized air was injected through the small hole 4 for about 5 seconds (about 80 m / s), the inner surface 1a of the preform 1 was dried.

  The temperature change of the inner surface 1a and the outer surface 1b of the preform 1 in this sterilization process is shown in FIG. 3 indicates the temperature change of the inner surface 1a of the preform 1, the alternate long and short dash line indicates the temperature change of the outer surface 1b of the preform 1, and the two-dot chain line indicates the glass transition temperature of PET.

  From the graph of FIG. 3, the time during which the temperature of the inner surface 1a of the preform 1 exceeds the glass transition temperature is about 2 seconds, and during that time, the temperature of the outer surface 1b is significantly lower than the glass transition temperature. I understand. Therefore, the preform 1 is not softened or deformed by the steam sterilization.

Table 1 below shows the moisture content of the preforms that were not subjected to the sterilization step and the preforms that were subjected to the sterilization step. The following Table 2 shows a cross-sectional rectangle obtained by blow molding a 2-liter PET bottle having a rectangular cross section obtained by blow molding a preform that has not been subjected to a sterilization process, and a preform subjected to a sterilization process. The various measurement values regarding the PET bottles containing 2 liters are shown.

  In Table 1 and Table 2 above, the upper part is the average value, and the numerical value enclosed in parentheses at the lower part is the standard deviation. Here, the standard deviation is a known scale representing variation, and is a square root of a numerical value obtained by dividing the sum of squares of the difference between the measured value and the average value by the number of samples. In addition, “front” seen in Table 2 means a relatively long side surface among the four side surfaces of the rectangular bottle, and “side surface” means a relatively short side surface. Yes.

  From Table 1 and Table 2 above, the moisture content of the preform 1 affecting the moldability of the preform 1, the thickness distribution, crystallinity, and heat resistance of the PET bottle obtained by blow molding are almost unchanged. I understand.

  From the above, according to the sterilization method using water vapor of the embodiment, since the sterilization can be performed in a short time without adversely affecting the preform 1 and sterilization using water vapor, there is no possibility that the bactericide remains. No. In addition, since the preform 1 is sterilized and no sterilizing agent remains by sterilization, the sterilization conditions of the blow-molded PET bottle can be relaxed, and the PET bottle can be sterilized. The apparatus which performs can be simplified.

It is a flowchart of an Example, and is a figure for demonstrating a series of work processes until it fills a PET bottle which carried out the blow molding of the preform, and a cap is closed. It is a figure for demonstrating the operation | work performed by the steam sterilization of the preform shown in FIG. 1, and the water removal process immediately after that. It is the graph which plotted the temperature change of the inner surface and outer surface of a preform when the steam sterilization of the preform shown in FIG. 1 and the water removal process just after that were performed. It is a conventional flowchart, and is a figure for explaining a series of operation steps from filling a PET bottle blow-molded with a beverage to closing the cap.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Preform 1a Inner surface of preform 1b Outer surface of preform 2 Mouth part of preform 3 Nozzle pipe 3a Upper end part where nozzle pipe is closed 4 Small hole in nozzle pipe

Claims (6)

A step of sterilizing the preform in a series of steps of filling the plastic container with a beverage after molding the plastic container from the preform;
The step of sterilizing the preform includes a steam sterilization step of spraying water vapor toward the inner surface of the preform,
In the steam sterilization step, the temperature of the outer surface of the preform is maintained at a temperature lower than the glass transition temperature of the preform material, while the temperature of the inner surface of the preform is the glass transition temperature of the preform material. A preform sterilization method, which is performed under a condition that the above temperature is continued for a predetermined time.   The preform sterilization method according to claim 1, further comprising a water removal step of removing water by injecting gas toward the inner surface of the preform immediately after the steam sterilization step. The gas injection is performed by a nozzle tube inserted into the preform;
The preform sterilization method according to claim 2, wherein the nozzle tube injects gas toward the inner surface of the preform while moving relative to the preform. The spray of water vapor is performed by a nozzle tube inserted into the preform;
The preform sterilization method according to claim 3, wherein the nozzle pipe for injecting the water vapor and the nozzle pipe for injecting the gas are configured by a common nozzle pipe. The spray of water vapor is performed by a nozzle tube inserted into the preform;
The preform sterilization method according to claim 3, wherein the nozzle pipe for injecting the water vapor and the nozzle pipe for injecting the gas are constituted by different nozzle pipes.   The preform sterilization method according to claim 4 or 5, wherein the steam sterilization step and the water removal step are performed immediately after the inverted posture with the mouth portion of the preform held down.

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