JP3177000B2 - Method and apparatus for measuring gas permeability of plastic bottle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to polyester resins such as polyethylene terephthalate PET, polyethylene naphthalate PEN and polybutylene terephthalate PBT,
The present invention relates to a method and an apparatus for measuring the gas (carbon dioxide, oxygen) permeability of a plastic bottle made of polycarbonate PC or the like.

[0002]

2. Description of the Related Art A major use of a plastic bottle is a bottle for carbonated beverages, and usually about 4 kg / cm ² of carbon dioxide gas is enclosed together with drinking water. A carbonated beverage loses its flavor if carbon dioxide gas is radiated or oxygen enters and oxidizes. Therefore, a plastic bottle containing a carbonated beverage that has low permeability to carbon dioxide gas and oxygen is desired. In order to obtain a bottle with low permeability, it is necessary to know the gas permeability of the bottle.However, there has been established a method for automatically measuring the permeability of a bottle in the short term up to the bottle. Absent. Regarding the carbon dioxide permeation test,
A method of filling a bottle with carbon dioxide gas and installing a pressure gauge at the mouth to measure the permeability of carbon dioxide gas from a decrease in pressure in a unit period has been adopted. In the oxygen permeation test, a certain amount of nitrogen is passed through the bottle and the amount of oxygen permeating from the outside of the bottle is measured using a coulometric electrode (a measuring instrument sold under the trade name of Paxtran from MOCON, USA) Has been adopted).

[0003]

The above-mentioned conventional test method has the following problems. That is, with respect to carbon dioxide permeation, in the case of a bottle having a small permeability, the pressure drop rate due to the permeation of carbon dioxide is small, and the measurement accuracy of the pressure gauge is generally low, so that the measurement accuracy of the permeability is poor. Regarding permeation, it is impossible to measure under various conditions in which the internal pressure of the bottle is changed, or the temperature and humidity are changed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to accurately test the permeability of carbon dioxide or oxygen, and furthermore, to change the internal pressure, temperature and humidity in a bottle. It can be performed automatically under the following conditions.

[0005]

According to the method for measuring carbon dioxide gas permeability of the present invention, the amount of carbon dioxide gas permeating from the bottle to the outside is set in a state in which carbon dioxide gas is put in a plastic bottle and set in a thermo-hygrostat. Gas permeability is measured by gas chromatography, and the permeability is calculated from the change over time of the accumulated permeation amount. When measuring the permeability of oxygen, a plastic bottle is used to measure N ₂ gas or Ar gas. After introducing the active gas, the amount of permeation of oxygen from the gas containing oxygen such as external oxygen or air into the bottle is measured by gas chromatography, and the transmittance is calculated from the change over time of the accumulated permeation amount. Things.

FIG. 1 shows the change with time of the amount of accumulated gas permeated. In the initial stage, the gas does not change linearly due to adsorption and dissolution of the gas into the bottle material, but thereafter changes linearly. Is shown. The transmittance is calculated by selecting an arbitrary period from the straight line portion in FIG.

[0007] According to the present method, the measurement accuracy is improved by performing the transmittance on the basis of the measured value of gas chromatography, and further, by using a constant temperature and constant temperature chamber, under various conditions where the temperature and humidity are changed. Can be easily measured. A gas supply device having a valve mechanism is provided to supply gas to the inside and outside of the bottle, and the inside and outside of the bottle are purged with carbon dioxide, an inert gas such as Ar gas or N ₂ gas, or a gas containing oxygen or oxygen. Thereby, the accuracy of the measurement can be further increased, and the pressure of the gas inside and outside the bottle can be arbitrarily set.

When the outside of the bottle is purged with a gas other than air, the bottle is placed in a sealed container and placed in a thermo-hygrostat in order to reduce the amount of gas used and shorten the gas purge time. It is desirable to set and gas purge the inside of the container. The above method can be carried out manually or automatically, and the device for the automatic operation is a constant temperature and humidity condition in which a plastic bottle is put directly or in a container. And a sampling unit equipped with a valve mechanism for supplying gas to the inside and outside of the bottle or opening and closing a line for sampling gas from inside and outside the bottle, and separating and detecting the gas sampled through the sampling unit to detect the permeated gas. Gas chromatography for measuring the concentration of gas, a control unit for controlling the sampling unit and gas chromatography based on a built-in program, and the accumulated gas permeation amount and the gas per unit period based on the concentration of the permeated gas measured by gas chromatography. And a data processing device for calculating the amount of transmittance.

The above apparatus is preferably provided with a measuring device for measuring the pressure, temperature and humidity inside and outside the bottle, and sends various data obtained to a data processing device to measure the gas permeability under various conditions. It can be obtained in time series.

[0010]

FIG. 1 is a block diagram of a measuring apparatus for performing a plurality of sets of a carbon dioxide gas permeability test and an oxygen permeability test in parallel. 1
a and a plurality of thermo-hygrostats 1b for measuring the amount of permeated oxygen are arranged in parallel, and a plastic bottle 2 is placed in a container 3 in each thermo-hygrostat 1a. Each is directly put into the wetter 1b.

A sampling unit 4a for measuring the transmission of carbon dioxide and a sampling unit 4b for measuring the transmission of oxygen.
Each contain a valve mechanism composed of a solenoid valve, a rotary valve, a switching cock, etc., and by switching the valve mechanism in the sampling unit 4a, each constant temperature / humidifier 1a
Purging carbon dioxide into the bottle and N ₂ gas into the container through lines 5 and 6 to the sampler, or sampling the gas in the container through line 7 and sending it to the automatic gas chromatography 8 Carbon dioxide gas is separated and detected, and the carbon dioxide gas concentration is measured.

On the other hand, by switching the valve mechanism in the sampling unit 4b, the line 9 to each thermo-hygrostat 1b is
Or purged with N ₂ gas into the bottle through, or by sampling the gas inside the bottle through line 10, which also crowded sent to the automatic gas chromatographic 8 detects separation of oxygen in the gas, to measure the concentration It has become.

As described above, the automatic gas chromatograph 8 sends data on the concentration of carbon dioxide passing through the outside of the bottle and the concentration of oxygen passing through the inside of the bottle for each of the thermo-hygrostats 1a and 1b from the detector via the control device 11. To the data processing device 12. The data processing device 12 also includes pressure data inside and outside the bottle detected by the pressure sensor 13 and a temperature and humidity sensor (not shown).
The data processing device processes the respective data together with the permeated gas concentration data and displays the data on the CRT (not shown) in time series for each bottle together with the permeated gas concentration data. Print out and calculate the cumulative gas permeation amount and the gas permeation amount per unit period from the concentration of each gas.

The control device 11 controls the sampling units 4a and 4b based on a built-in program, and supplies and discharges a purge gas or a sampling gas into and out of the bottle, sampling of gas inside and outside the bottle by switching a valve mechanism. The vacuum pump 14 drives the valve mechanism and eliminates the gas remaining in the line, controls the automatic gas chromatography 8, supplies the carrier gas, and detects the concentration of carbon dioxide and oxygen from the sampling gas. Let

The present apparatus is configured as described above, and an example of a measuring method using the apparatus will be described below. The valve mechanism of each sampling unit 4a, 4b is switched by a control signal from the control device, and for all valves, carbon dioxide gas is stored in the bottle 2 in the constant temperature and humidity chamber 1a for permeating carbon dioxide gas. with respectively fixed period purging N ₂ gas to the container 3 to be, the N ₂ gas for a predetermined time gas purge against the bottle in the oxygen permeability for thermo-hygrostat 1b. After the gas purge, close each discharge valve, continuously supply carbon dioxide gas or N ₂ gas until the gas pressure inside and outside the bottle reaches the set pressure, close the supply valve when the set pressure is reached, and stop the supply of each gas. .

The above is a gas purge and a set pressure of carbon dioxide,
The example in which the N ₂ gas is filled while the bottle or its container is placed in the thermo-hygrostat has been described.
The N ₂ gas may be filled outside the thermo-hygrostat, and after the gas is filled, the N ₂ gas may be set in the thermo-hygrostat. Thereafter, the automatic gas chromatography 8, the control device 11 and the data processing device 12 are turned on, and the respective sampling units 4a,
The gas inside and outside the bottle is sampled by switching the valve mechanism of 4b, and the concentration of carbon dioxide and oxygen in the gas is measured for each bottle by the automatic gas chromatography 8. Then, the measured values are transmitted to the data processing device 12 via the control device 11, and the data processing device 12 calculates the amount of accumulated carbon dioxide and oxygen permeated from the carbon dioxide and oxygen concentrations, and then calculates the amount of each gas per unit period. Is calculated.

At the same time, pressure data, temperature and humidity data inside and outside the bottle are transmitted to the data processing device 12 via the control device 11, and the data of the carbon dioxide gas concentration, oxygen concentration, pressure, temperature and humidity are transmitted by the device 12. The bottles are arranged in chronological order for each bottle, displayed on a CRT and printed out.

[Experimental Example] A pressure-resistant container having a diameter of 9 cm and a height of 31 cm was molded using a biaxial stretch blow molding machine (LB01 manufactured by Corporast) using PET resin (J135 intrinsic viscosity 0.85 manufactured by Mitsui PET Co., Ltd.). . The volume of this container was 1613 ml and the weight was 43 g. Under the conditions of a carbon dioxide gas permeability of this container at a temperature of 23 ° C. and an initial bottle internal pressure of 5.11 kg / cm ² , FIG.
The measurement was performed using the apparatus shown in FIG. The results are shown in Table 1 and FIG. As shown in FIG. 3, the amount of transmission is small at the beginning of the test, and the rate of increase becomes constant from the third day. FIG. 4 shows a graph from the fourth day to the eighth day. When the transmittance is calculated from the slope, it is 2,596 cc / da
y · atm was obtained. FIG. 4 shows the results of the carbon dioxide gas permeability calculated in the straight section from the fourth day to the eighth day.

[Table 1]

The present invention is configured as described above and has the following effects. According to the measuring method according to claim 1 or 2, the carbon dioxide or oxygen permeability test of the plastic bottle can be performed non-destructively while the bottle is kept, and the permeability can be obtained based on the measured value of gas chromatography. Therefore, the measurement accuracy can be improved, and the measurement under the condition where the temperature and the humidity are changed can be easily performed by changing the temperature and the humidity of the thermostat. If a gas supply device is provided as in the method of claim 3, the inside and outside of the bottle can be purged with gas, so that the measurement accuracy can be further increased and the bottle is subjected to internal pressure for measurement. It is also possible to easily evaluate the pressure vessel. If the measurement is carried out by placing the bottle in a container as in the method according to claim 4, the amount of oxygen or gas containing oxygen can be reduced, and the amount of gas used during gas purging can be reduced. The time required for gas purging can be shortened. In the apparatus according to the fifth aspect, gas supply, exhaust, measurement of permeated gas, data collection and analysis can be further automated, so that measurement can be unmanned. When a measuring device for measuring pressure, temperature and humidity is provided as in the device according to claim 6, data of gas concentration, pressure, temperature and humidity can be obtained in time series for each bottle.

[Brief description of the drawings]

FIG. 1 is a graph of a cumulative gas permeation amount.

FIG. 2 is a block diagram of a measuring device according to the present invention.

FIG. 3 is a graph showing a permeation amount of carbon dioxide gas.

FIG. 4 is a graph showing carbon dioxide gas permeability.

[Explanation of symbols]

1a, 1b ... constant temperature and humidity chamber 2 ... plastic bottle 3 ... container 4a, 4b ...
・ Sampling unit 8 ・ ・ ・ Automatic gas chromatography 11 ・ ・ ・ Control device 12 ・ ・ ・ Data processing device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-172942 (JP, A) JP-A-57-58029 (JP, U) JP-A-63-33440 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) G01N 33/44 G01N 17/00 G01N 15/08 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. In a state in which carbon dioxide gas is put into a plastic bottle, and set in a thermo-hygrostat, the amount of carbon dioxide gas permeating out of the bottle is measured by gas chromatography. A method for measuring the gas permeability of a plastic bottle, wherein the gas permeability is calculated. 2. A plastic bottle containing N ₂ gas or Ar gas.
Put an inert gas such as gas, and measure the amount of oxygen permeated from the gas containing oxygen such as external oxygen or air into the bottle by gas chromatography while setting it in a thermo-hygrostat. A method for measuring the gas permeability of a plastic bottle in which the permeability is calculated from a change over time. 3. The method for measuring gas permeability of a plastic bottle according to claim 1, wherein a gas is supplied from inside and outside of the bottle from a gas supply device. 4. The method for measuring gas permeability of a plastic bottle according to claim 2, wherein the bottle is placed in a container and set in a thermo-hygrostat. 5. A thermo-hygrostat in which a plastic bottle is placed directly or in a state of being contained in a container, and a line for supplying gas to the inside and outside of the bottle or sampling a gas from inside and outside the bottle. A sampling unit having a valve mechanism to perform, a gas chromatography for separating and detecting the gas sampled through the sampling unit and measuring the concentration of the permeated gas, and a control device for controlling the sampling unit and gas chromatography based on a built-in program. An apparatus for measuring the gas permeability of a plastic bottle, comprising: a data processing device for calculating a cumulative gas permeation amount and a gas permeation amount per unit period from a gas permeation concentration measured by gas chromatography. 6. The apparatus for measuring gas permeability of a plastic bottle according to claim 4, further comprising a measuring device for measuring pressure, temperature and humidity inside and outside the bottle and transmitting the data to a data processing device.