JP5658431B2 - Heat sealing method for packaging bags - Google Patents

Description

  The present invention relates to a heat sealing method for a packaging bag, which can control the sealing temperature of the packaging bag.

  Conventionally, when liquids such as spices and wheat flour, or liquids such as pasta sauce are sold to general consumers, a certain amount of the content of 3 g to 2 kg is packed into a small bag as a packaging bag. Packaged and distributed as household sachets. Such a filling and packaging process for home sachets is mechanized and provided as a filling and packaging apparatus.

  Synthetic resin packaging bags are often used as packaging bags for household sachets. Synthetic resin bags have a merit that they are highly sealed and can prevent moisture from entering from the outside, and can have light shielding properties depending on the material.

  In Patent Document 1, when a container forming material film is sandwiched between a pair of sealing molds and heated and pressed to form a seal portion, optical information is obtained from the seal portion immediately after formation via a light detection device. An invention is disclosed in which the temperature, pressing force and the like of the sealing mold are controlled to a predetermined value via a control operation unit based on the calculation processing result of the optical information.

Japanese Patent Laid-Open No. 09-030514

  By the way, Patent Document 1 discloses that optical information is obtained from a seal portion immediately after formation (heating), and that the temperature, pressing force, and the like of a sealing mold are controlled to predetermined values based on the optical information. However, the container forming material is only described as a film, and nothing is disclosed regarding the material of the film and the optimum heat sealing condition when the film is changed to various materials.

  In the conventional heat sealing method, the heat sealing conditions are different each time due to the difference in the material of the film, the difference in the packaging apparatus to be used, and the like, and the defective rate of the heat sealing varies accordingly. When two or more packaging devices of the same model are used, even if the plurality of heat seal bars are set to the same set temperature, the obtained seal strength differs depending on the packaging device. Differences in the usage frequency, age, or maintenance status of the packaging equipment, as well as the number of revolutions of the sealing operation of the packaging equipment, uneven temperature of the heat seal bar, shape and material of the heat seal bar, and changes in the ambient temperature around the packaging equipment due to seasonal changes Furthermore, it is rare that they are intertwined in a complicated manner, and even in the same model, the same seal strength can be realized in a plurality of packaging devices of different individuals. Eventually, the operator of the packaging equipment was adjusting the set temperature of the heat seal bar based on experience and intuition.

  If the optimal temperature setting of the heat seal was not well understood and the adjustment was not successful, even though it seemed that there was no difference from the normal product after applying the heat seal under moderate conditions, they were actually underheated In some cases, there was a problem that a large amount of defective seals were finally generated.

  The present invention has been made in view of the above points. Regardless of the difference in film material or the packaging device used, any material film or any packaging device can be used for pseudo-adhesion or overheating due to insufficient heating. It is an object of the present invention to provide a method for heat-sealing a packaging bag that does not cause edge breakage or thinning due to the above-mentioned, and can perform good heat-sealing without relying on operator experience or intuition.

The present invention is a heat sealing method for forming a seal portion by sandwiching an opening of a synthetic resin packaging bag between a pair of heat seal bars, the temperature of the seal portion immediately after heat sealing, and the seal A temperature-strength curve which is a curve representing the relationship by measuring a relationship with the seal strength of the portion in advance, and a second from the low temperature side among the bending points where the slope of the temperature-strength curve changes. When the second bending point is the second bending point and the third bending point from the low temperature side is the third bending point, the second bending point and the third bending point of the temperature-intensity curve The relationship between the temperature zone in the interval between the step of obtaining the optimum heat seal temperature zone, the set temperature of the heat seal bar during heat sealing, and the temperature of the seal portion immediately after heat sealing is measured in advance. A step of creating a set temperature curve which is a curve representing the relationship, and a step of obtaining an optimum set temperature zone which is a set temperature zone of the heat seal bar corresponding to the optimum heat seal temperature zone based on the set temperature curve And a step of setting the set temperature of the heat seal bar within the optimum set temperature range, and sandwiching the opening of the packaging bag by the heat seal bar to form the seal portion, and the seal immediately after the heat seal Measuring the temperature of the part from one end to the other end of the seal part to obtain the packaging bag surface temperature, and when the packaging bag surface temperature is not larger than the lower limit value of the optimum heat seal temperature zone Determining that the packaging bag is defective, and if the packaging bag surface temperature is not smaller than the upper limit of the optimum heat seal temperature zone, the packaging bag is defective. Possess and determining and that the said synthetic resin of the packaging bag is the material of the bag with the second bending point, and the third bending point, characterized in that.

  According to the present invention, no matter what kind of film or packaging device is used, regardless of the film material or the packaging device used, pseudo-adhesion due to insufficient heating or edge cutting or thinning due to overheating can occur. Good heat sealing can be performed.

  That is, in the present invention, good heat sealing can be performed.

  The heat sealing method of the packaging bag according to the present invention is such that the synthetic resin packaging bag is PET /.../ retort CPP type, OPP /.../ CPP type, in addition to PET /.../ LDPE type. The present invention is not limited to a multilayer structure such as ONY /... / LDPE system or an LDPE system single layer structure, and can be applied to any film.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view showing an outline of a filling and packaging apparatus to which the present invention is applied.

  As shown in FIG. 1, the filling and packaging apparatus 1 includes a bag supply unit 2 that supplies a packaging bag, a main body unit 3 that fills and packs the contents into the packaging bag, and is filled with the contents. And a discharge unit 4 for discharging the packaged product.

  The bag supply unit 2 includes a conveyor 2 a and conveys the packaging bag 5 placed on the conveyor 2 a so as to be supplied to the main body unit 3.

  The main body 3 has a rotary 8 that rotates clockwise. Ten combinations of claws 15 and 16 are provided on the outer periphery of the rotary 8, and the packaging sandwiched between the claws 15 and 16 as the rotary 8 rotates. The bag 5 is carried to each process.

  In the main body 3, the packaging bag 5 supplied from the bag supply unit 2 is taken up, and both sides of the packaging bag 5 are sandwiched between the claws 15 and 16 at the position 8 a of the rotary 8.

  When the rotary 8 rotates clockwise and the packaging bag 5 sandwiched between the claws 15 and 16 reaches the position 8b, the filling portion 7 fills the packaging bag 5 with the contents.

  Here, a bag before filling the contents is called a packaging bag, a bag in the middle of filling and packaging the contents is called a filling packaging bag, and a bag after filling and packaging the contents is called a package.

  Further, the process proceeds, and at the position 8c, the upper part of the filling and packaging bag 50 is heat-sealed with heat by the heat seal device 17 which is a sealing part, and the packaging of the contents is completed. The heat sealing device 17 has heat sealing bars 17a and 17b, and performs heat sealing by sandwiching the upper portion of the filling and packaging bag 50 with heat sealing bars 17a and 17b heated by heaters 20a and 20b described later.

  The temperature sensors 18 and 19 detect the temperature of the heat-sealed portion of the filling and packaging bag 50, and will be described in detail later.

  The package 500 in which the contents are filled and packaged is placed on the conveyor 4a of the discharge unit 4 and discharged at a position 8d. At this time, the package 500 in which any abnormality is detected during the filling and packaging process in the main body 3 is repelled by the flipper device 4b.

  Next, the structure of the heat seal device 17 shown in FIG. 1 will be described in detail with reference to the drawings. FIG. 2 is a schematic perspective view showing the heat sealing device 17 of the filling and packaging apparatus 1 shown in FIG. FIG. 3 is a cross-sectional view of the heat sealing device 17 shown in FIG. 2 as viewed from the side.

  As described above, the filling and packaging bag 50 is filled with the contents with the claws 15 and 16 sandwiched on both sides, and then the filling port 50a is thermocompression bonded and heat-sealed, whereby the filling and packaging bag 50 is Sealed.

  Each of the heat seal bars 17a and 17b of the heat seal device 17 has heaters 20a and 20b, and the filling port 50a of the filling packaging bag 50 is heated by the heat seal bars 17a and 17b heated by the heaters 20a and 20b. Heat seal. The packaging bag 5 made of synthetic resin has, for example, a PET /... / LDPE multilayer structure. The packaging bag 5 is made of PET / PE /.../ LLDPE, ONY /.../ LLDPE, OPP /.../ CPP, PET // ONY // retort CPP multilayer films, LDPE, etc. It can be anything like a single layer.

  The temperature of the heat seal bars 17a and 17b when the heat seal is performed by the heat seal device 17 is too low, too high, the heat seal pressure is high or low, the heat seal time is long or short, the packaging material If the temperature is high or low, etc., heat sealing cannot be performed properly, resulting in a defective product. In the present embodiment, such defective product detection and control for optimizing the temperature are performed.

  FIG. 4 is a schematic perspective view showing the temperature sensor 18 of the filling and packaging apparatus 1 shown in FIG.

  In the present embodiment, the temperature sensors 18 and 19 are provided as shown in FIG. 1, but only one of the temperature sensor 18 or the temperature sensor 19 may be provided. The temperature sensors 18 and 19 detect infrared rays and measure the temperature of the object in a non-contact manner.

  The temperature sensor 18 is an infrared radiation thermometer, and has an infrared sensor that detects infrared rays from the object to be measured with a point. As the package 500 is moved by the rotation of the rotary 8, the heat seal location of the package 500 is detected. For example, the temperature from the left end toward the right end in the (sealing portion) 500a is sequentially detected, and the temperature waveform in the lateral direction of the heat seal portion 500a is acquired. According to this configuration, temperature unevenness in the lateral direction of the heat seal portion 500a can be detected, and a partial heat seal failure can also be detected.

  The temperature sensor 19 is an infrared camera that captures infrared rays from the object to be measured on a surface. According to the temperature sensor 19, when the rotary 8 is stopped, the entire surface of the heat seal portion 500a of the package 500 is photographed, and the temperature distribution of the heat seal portion 500a is acquired. According to this configuration, the temperature unevenness in the lateral direction of the heat seal portion 500a can also be detected, and a partial heat seal failure can also be detected.

  It is desirable that the heat-sealed portion 500a of the package 500 heat-sealed by the heat-sealing device 17 is heated to a predetermined temperature necessary for heat-sealing. Therefore, it is possible to detect whether or not the heat sealing has been performed correctly by detecting the temperature of the heat sealing portion 500a. That is, if the detected temperature is within a predetermined temperature range (for example, 90 ° C. or higher and 130 ° C. or lower), it is determined that the heat seal is correct. If the detected temperature is not within the predetermined temperature range, the heat seal is not correct. Judge that The filling and packaging apparatus 1 includes a control unit 100, and this determination is performed by the control unit 100 described later.

  The package 500 in which the contents are packaged and heat-sealed as described above is placed on the conveyor 4a of the discharge unit 4 and discharged.

  At this time, if it is determined that the heat seal has been correctly performed as a result of the determination by the control unit 100 based on the detection results by the temperature sensors 18 and 19, the package 500 passes over the conveyor 4a. Go.

  On the other hand, if it is determined that the heat seal is not correctly performed as a result of the determination by the control unit 100 based on the detection results by the temperature sensors 18 and 19, the flipper device 4b shown in FIG. 1 is driven. The package 500 is repelled by the flipper device 4b.

  By the way, in the control part 100 of this Embodiment, based on the detection result by the temperature sensors 18 and 19, temperature control of the heaters 20a and 20b is also performed. A block diagram of a configuration related to control by the control unit 100 is shown in FIG.

  The control unit 100 inputs detection results of the temperature sensors 18 and 19, performs opening / closing control of the heat seal bars 17a and 17b, performs temperature control of the heaters 20a and 20b, and performs drive control of the flipper device 4b.

  FIG. 6 is a flowchart showing the temperature control processing of the heaters 20a and 20b by the control unit 100.

  The heat seal bars 17a and 17b are provided with temperature sensors (not shown), and the control unit 100 performs heating by the heaters 20a and 20b so that the temperature detected by the temperature sensors becomes the set temperature Ts (A-1: No, A-2). This set temperature Ts may be determined in advance according to the material of the packaging bag 5 and stored in a nonvolatile memory (not shown) of the control unit 100. If the material of the synthetic resin packaging bag 5 is a PET /... / LDPE multi-layer structure, the set temperature Ts is set to about 120 ° C., for example. This set temperature Ts is within the range of the optimum set temperature range described later.

  If the temperature of the heat seal bars 17a and 17b reaches the set temperature Ts (A-1: Yes), the filling and packaging bag 50 is heat sealed by the heat seal bars 17a and 17b (A-3).

  Subsequently, the temperature sensors 18 and 19 detect the temperature Tm of the heat seal portion 500a of the package 500 (A-4). As this temperature Tm, in order to prevent a partial heat seal failure in the width of the package 500, it is preferable to adopt a numerical value at each position of the width of the package 500.

  In the present embodiment, a temperature range in which heat sealing is favorably performed (that is, an optimum set temperature range) is set in advance and stored in a non-illustrated nonvolatile memory of the control unit 100. This temperature range may be determined according to the material of the packaging bag 5. This temperature range will be described below with reference to FIGS. 7, 8 and 9. FIG.

  The seal strength of the heat-sealing packaging material is determined by JIS (JIS Z 0238) to perform a tensile test on a test piece having a width of 15 to 20 mm.

  FIG. 7 illustrates a conventional method, and is a diagram illustrating a heat seal curve in which the heat seal strength is measured for each set temperature of the heat seal bar. The packaging material used here is PET 12 μm / PE 20 μm / LDPE 40 μm, and heat sealing is performed by stacking two sheets so that the LDPE side surfaces of the film are in contact with each other.

  In FIG. 7, for example, “PA4 (40 rpm)” refers to the case where the heat seal packaging is performed 40 times per minute in the packing machine No. 4, and the “heat seal tester 0.3 MPa”. This is the case where heat sealing tester (TP-701-B) manufactured by Tester Sangyo Co., Ltd. is used and heat sealing is performed by stacking two films under a pressure of 0.3 MPa.

  According to FIG. 7, it can be seen that the heat seal strength is determined for each set temperature of the heat seal bar. Conventionally, the set temperature of the heat seal bar is determined using this curve. This method is a method for confirming the sealing strength of packaging materials that are generally used. However, even if this is for a single packaging material, operating conditions such as machine type, rotation speed, etc., pressure unevenness on the seal surface, and application of Teflon (registered trademark) tape to the heat seal bar surface It shows that a number of heat seal curves exist depending on various conditions such as attachment (for the purpose of preventing attachment of the packaging material to the heat seal bar). In addition, this heat seal curve fluctuates due to disturbances such as packaging material temperature, outside air, and warming of the apparatus, so it cannot be used for optimizing machine operating conditions.

  Therefore, in the present embodiment, the operating conditions are optimized by the following method. First, the optimum heat seal temperature zone is obtained.

  FIG. 8 shows the relationship between the temperature of the heat-sealed portion 500a of the package 500 immediately after heat-sealing and the tensile stress (heat-sealing strength) that can be endured without being peeled off when the heat-sealed portion is peeled off at that temperature. It is a graph which shows. That is, this curve is a temperature-intensity curve. The heat seal strength was measured according to JIS (JIS Z 0238) as in FIG.

  The graph shown in FIG. 8 shows the data of four experiments conducted in an environment where the material of the packaging bag 5 is the same as in FIG. 7 and the temperature is different, and the temperature of the heat seal portion 500a is 90 ° C. It can be seen that sufficient tensile stress is obtained at ˜130 ° C. (optimal heat seal temperature zone (referred to herein as the optimum heat seal temperature zone because of heat seal)). On the other hand, if it is 90 ° C or lower, it is easy to peel off in a state called pseudo-adhesion (pseudo-adhesive danger region), and if it is 130 ° C or higher, the temperature is too high and it may be partially broken (edge breakage). The problem that the seal part becomes thin (thinning) occurs (edge cutting edge thinning danger area).

  Referring to FIG. 8, this curve has the characteristic of having three bending points where the inclination changes, and the bending point (where the curve rises when the temperature of the heat seal portion 500a of the packaging bag 5 is low) Up to the next bend point (second bend point) past the first bend point) is the pseudo-adhesion risk region, and the subsequent bend point (third bend point) is the optimum heat seal temperature zone, After that is the edge cut thinning danger area.

  Therefore, in the present embodiment, 90 ° C. to 130 ° C. (see FIG. 8) is stored in a non-volatile memory (not shown) of the control unit 100 as the optimum heat sealing temperature range that is a temperature range in which heat sealing is performed satisfactorily. .

  FIG. 9 is a graph showing the relationship between the set temperature of the heat seal bars 17a and 17b and the temperature of the heat seal portion 500a of the package 500 immediately after the heat seal. That is, this curve is a set temperature curve.

  In order to set the temperature of the heat seal portion 500a immediately after heat-sealing the package 500 to the optimum heat seal temperature zone obtained with reference to FIG. 8, the set temperature curve is set for the heat seal bars 17a and 17b. This is to find out how to set the temperature. By applying the optimum heat seal temperature zone to FIG. 9, the optimum set temperature zone can be obtained.

  According to FIG. 9, it can be seen that the set temperature x of the heat seal bar and the packaging material temperature y immediately after the heat seal can be expressed by a linear function, and y = 0.85551x-11.676. When it is rewritten, it becomes x = 1.695y + 13.655. For example, if you want to set the packaging material temperature immediately after heat sealing to 100 ° C., substitute 100 for y and set x = 130, that is, the heat sealing bar to 130 ° C. That's all you need to do.

この例では、最適ヒートシール温度帯（ｙ）が９０℃〜１３０℃であるとすると、最適設定温度帯（ｘ）はおよそ１２０℃〜１７０℃となる。

In this example, if the optimum heat seal temperature zone (y) is 90 ° C to 130 ° C, the optimum set temperature zone (x) is approximately 120 ° C to 170 ° C.

  Returning to the description of FIG. 6, in step (A-5), it is determined whether or not the detected temperature Tm is higher than the lower limit Ti (90 ° C. in this case) of the optimum heat seal temperature zone.

  If the detected temperature Tm is not higher than the lower limit Ti (90 ° C. in this case) of the optimum heat seal temperature zone (A-5: No), it is determined as a defective product (A-6), and the package 500 is flipped. It is repelled by the device 4b (A-7). Thereafter, to increase the temperature of the heat seal bars 17a and 17b, the coefficient (here, 1.1695) in Equation 1 is multiplied by (Ti−Tm), and this is added to the set temperature Ts to obtain a new set temperature. If it is still operating (A-14: Yes), the process returns to step (A-1) and the process is continued using the set temperature Ts updated in step (A-8). .

  In step (A-5), if the detected temperature Tm is higher than the lower limit Ti of the optimum heat seal temperature zone (A-5: Yes), then in step (A-9), the detected temperature Tm is the optimum heat seal temperature. It is determined whether the band is lower than the upper limit value Th (here 130 ° C.).

  If the detected temperature Tm is not lower than the upper limit value Th (130 ° C. in this case) of the optimum heat seal temperature zone (A-9: No), it is determined as a defective product (A-10), and the package 500 is flipped. It is repelled by the device 4b (A-11). Thereafter, to reduce the temperature of the heat seal bars 17a and 17b, the same coefficient as described above (here, 1.1695) is multiplied by (Tm-Th) and subtracted from the set temperature Ts to obtain a new set temperature Ts. (A-12) If it is still in operation (A-14: Yes), the process returns to step (A-1), and the process is continued using the set temperature Ts updated in step (A-12).

  In step (A-9), if the detected temperature Tm is lower than the lower limit value Th of the optimum heat seal temperature zone (A-9: Yes), it is determined that the product is non-defective (A-13), and the package 500 is conveyed to the conveyor. If transported by 4a and still operating (A-14: Yes), the process returns to step (A-1).

  In step (A-14), if the process is completed (A-14: No), the process ends.

  In addition, this invention can be applied with respect to the bag of various forms as the packaging bag 5, a four-side seal bag (thing which heat-seals all the circumference | surroundings), a three-side seal bag (a heat seal is applied to three sides) What to do) Three-sided back-sealed seal bag (top-bottom + back-to-back three-sided heat-sealed one), tube roll bag (one to heat-seal at the top and bottom of the inflation tube), gusset bag It can also be applied.

It is a top view which shows the outline of the filling packaging apparatus by one embodiment of this invention. It is a schematic perspective view which shows the heat seal apparatus 17 of the filling packaging apparatus 1 shown in FIG. It is sectional drawing which looked at the heat seal apparatus 17 shown in FIG. 2 from the side. It is a schematic perspective view which shows the temperature sensor 18 of the filling packaging apparatus 1 shown in FIG. 3 is a block diagram of a configuration related to control by a control unit 100. FIG. It is a flowchart which shows the temperature control process of the heat seal bars 17a and 17b by the control part 100. FIG. It is a figure which shows the conventional heat seal curve which measured the heat seal intensity | strength for every preset temperature of a heat seal bar. It is a graph which shows the relationship between the temperature of the heat seal location 500a of the package 500 just after heat sealing, and the tensile stress which can be endured without peeling when trying to peel the heat sealed location. It is a graph which shows the relationship between the preset temperature of heat seal bar 17a and 17b, and the temperature of the heat seal location 500a of the package 500 immediately after the heat seal in that case.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Filling and packaging apparatus 2 Bag supply part 2a Conveyor 3 Main body part 4 Discharge part 4a Conveyor 4b Flipper apparatus 5 Packaging bag 7 Filling part 8 Rotary 15, 16 Claw 17 Heat seal apparatus 17a, 17b Heat seal bar 18, 19 Temperature sensor 20a, 20b Heater 50 Filling packaging bag 100 Control unit 500 Packaging

Claims (1)

A heat sealing method for forming a seal portion by sandwiching an opening of a synthetic resin packaging bag between a pair of heat seal bars,
A step of measuring a relationship between the temperature of the seal portion immediately after heat sealing and the seal strength of the seal portion in advance and creating a temperature-strength curve that is a curve representing the relationship;
Of the bending points where the slope of the temperature-intensity curve changes, the second bending point from the low temperature side is the second bending point, and the third bending point from the low temperature side is the third bending point. Obtaining a temperature zone of a section between the second bending point and the third bending point of the temperature-intensity curve as an optimum heat seal temperature zone;
A step of measuring a relationship between a set temperature of the heat seal bar at the time of heat sealing and a temperature of the seal portion immediately after the heat seal to create a set temperature curve which is a curve representing the relationship;
Based on the set temperature curve, obtaining an optimum set temperature zone that is a set temperature zone of the heat seal bar corresponding to the optimum heat seal temperature zone;
Setting the set temperature of the heat seal bar within the optimum set temperature zone, and sandwiching the opening of the packaging bag by the heat seal bar to form the seal portion;
Measuring the temperature of the seal part immediately after heat sealing from one end to the other end of the seal part to obtain the packaging bag surface temperature;
A step of determining that the packaging bag is defective when the packaging bag surface temperature is not greater than a lower limit value of the optimum heat seal temperature zone;
A step of determining that the packaging bag is a defective product when the packaging bag surface temperature is not smaller than the upper limit value of the optimum heat seal temperature zone;
I have a,
The synthetic resin packaging bag is a bag made of a material having the second bending point and the third bending point.
The heat sealing method characterized by the above-mentioned.

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