JP3465741B2 - How to determine heat sealing conditions for plastics - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sealing operation which is often performed in sealing and bag-forming a sheet-like plastic by press-fitting and heating. The present invention relates to a method for providing theoretical support and easily implementing the empirical operation speed and the temperature setting of a heating element that must be changed for each used material. 2. Description of the Related Art In a packaging material for sealing a container using a sheet-like plastic or for stacking a sheet-like material into a bag-like shape, the sealing and the thermocompression bonding of the bag-making are simply mechanical. Ranging from chemically binding to protecting the ingress and egress of gases and microorganisms. For the latter purpose,
It requires reliable welding of the bonding surface. Conventionally, production machines have been suspended for a long time, sealing has been performed using actual materials, heat sealing tests have been conducted using a large amount of materials and humans, and welding samples obtained under a wide range of operating conditions of heating temperature and crimping time have been tested according to JIS. Determined by the indirect inspection based on the tensile test and observation specified in [0003] Conventionally, there are the following problems in determining the heat-compression bonding conditions for plastic materials. (1) Production stoppage of actual equipment (2) Preparation of large amount of test materials (3) Manual operation of test operation and evaluation of test results (4) Since the temperature of the welding surface is not directly controlled,
Heating conditions will be set higher, which may cause heat damage to the heat-sealed part.The present invention measures the above-mentioned problems by actually measuring the welding temperature of each material and reducing the surface temperature of the heating block of the production machine. By simply providing them, an attempt is made to theoretically and economically improve the setting of the thermocompression bonding conditions. [0004] The setting of the temperature of the heating element and the determination of the compression time in the heat seal are determined by the following method using a small number of test pieces and a thermal compression test apparatus in a test room. (1) Welding surface A fine temperature sensor is inserted between the two test pieces facing each other with the inside facing inside, and the temperature of the welding surface is automatically stored or recorded. Attach the same surface material as the surface material such as polytetrafluoroethylene tape to be installed. (3) Adjust the surface temperature of the heating element with high precision, and at a temperature higher than the estimated welding temperature at intervals of about 10 ° C. The test piece is heated by changing the setting. (4) The test piece is pressed and heated for each heating, and the welding surface temperature is stored or recorded with time. (5) The time-dependent change of the welding surface temperature for each heating is As a welding surface temperature curve, one sheet with temperature on the vertical axis and time on the horizontal axis (6) Select the desired welding surface temperature and insert a horizontal line indicating the welding surface temperature position on the graph. (7) Copy the actual crimping time of the actual machine on the graph. Obtain the surface temperature of the heating body in the welding surface temperature curve passing through the intersection of the surface temperatures. (8) The obtained surface temperature of the heating body is realized in the actual machine by correcting the difference between the surface temperature in the actual machine and the adjustment set temperature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for measuring a welding surface temperature will be described with reference to FIG. 1 (the scale of each part is different for easy understanding of the form). The plastic to be tested consists of the heat sealant layers (1) and (1 '), the substrate (2),
The composite of (2 ′) is shown. The fine temperature sensor (4) installed on the welding surface is installed so as to be sandwiched between the welding surfaces of the heat sealant layers (1) and (1 '), and the temperature is converted into a voltage signal, and the recorder (6) Is connected to and used for data analysis. Heating block (5), (5 ')
Is set to one-side heating or two-side heating under actual operating conditions. The heating blocks (5) and (5 ') can be pressed and released from a test piece of the plastic under test by an operating mechanism (not shown). Heating block
The surfaces of (5) and (5 ') are covered with a polytetrafluoroethylene sheet (3) and (3') with an actual machine in order to make it difficult for the plastic under test to be scorched and to maintain the uniformity of pressure bonding. If so, take the same action. Heating block (5),
(5 ′) Both or one of the surface temperatures at which one is adjusted is sequentially changed from the estimated welding temperature at intervals of about 10 ° C.
A new test piece having a size of about 2 to 3 cm is used for each compression, and the temperature of the welding surface is recorded. Organize the collected temperature data into a graph or table of temperature and time. By selecting the desired welding surface temperature and the crimping time of the actual machine, the surface temperatures (7) and (7 ') of the corresponding heating blocks (5) and (5') are obtained. In other words, the desired welding surface temperature is replaced by the heating block surface temperature and is made universal. Temperature control of actual equipment often does not always detect the surface temperature of the temperature sensor,
Measure the surface temperature of the actual machine and correct it with the set value. Details will be described in [Example]. An embodiment will be described in the case of heating at the same temperature on both sides. The welding surface temperature for each temperature of the heating block obtained by the measurement method shown in FIG. 1 is collected in FIG. 2 and shown in a graph. The rate at which the temperature of the welding surface rises is determined by the thermal conductivity and thickness of the heat sealant layer and the base material of the test piece, which is a plastic sheet. In the embodiment, the desired welding surface temperature is set to 125 ° C., and a horizontal line is added to the graph. A perpendicular line is drawn from the intersection of this horizontal line and each graph. When the surface temperature of the heating block is 160 ° C., the pressing time is 0.38 seconds. Similarly, at 150 ° C., 0.43 seconds are obtained, at 143 ° C., 0.53 seconds, and at 130 ° C., 0.71 seconds. The crimping time is not the time during which the machine performs the crimping operation, but the time from when the heating block comes into contact with the plastic under test until it separates. It should be noted that usually, the pressing operation time of the machine and the pressing time of the heating element (heat bar) are often confused. Conversely, in the case where peeling occurs due to denaturation of the adhesive layer of a composite film or a substrate having a heating temperature limitation such as an OPP film, priority is given to the heating limitation temperature, for example, 143 ° C. Surface temperature is lower than this value).
The crimping time is 0.52 seconds, and the operating speed determined from the crimping time is the upper limit speed. Speed settings beyond this speed significantly reduce heat seal finish. If the surface temperature obtained here is realized by an actual machine, it is possible to operate under the heat sealing condition of a predetermined welding temperature, and it is possible to omit the conventional expensive and troublesome work. According to the present invention, the following effects can be obtained by setting the heat sealing conditions based on data obtained by directly measuring the actual welding temperature of the plastic material. (1) Heat sealing conditions (heating temperature, compression time) for each material (including lot) are set to be easy, reliable, and inexpensive by achieving production suspension of equipment, eliminating the need for large-volume materials for testing, and speeding up. Can be used (2) Can be used as a universal quality assurance index of heat sealing technology. (3) Can have the function of "CCP" in heat sealing process which requires "HACCP"

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an outline of a method for measuring a welding surface temperature according to the present invention. FIG. 2 is an outline of a method for determining a heating temperature and a pressing time according to the present invention. [Description of Signs] 1,1 'Heat sealant layer 2, 2' Base material 3, 3 'Polytetrafluoroethylene 4 Temperature sensor 5 Heating block 6 Temperature recorder 7, 7' Surface temperature

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 65/00-65/82 B65B 51/00-51/32

Claims (1)

(57) [Claims 1] The temperature setting of the heating element and the determination of the compression time in the heat sealing are determined by the following method using a small number of test pieces and a thermal compression test apparatus in a test room ( 1) A fine temperature sensor is inserted between two test pieces facing each other with the welding surface inside, and the temperature of the welding surface is automatically stored or recorded. (2) On the surface of the heating element of the test device Is to install the same surface material as the surface material such as polytetrafluoroethylene tape to be mounted on the actual machine. (3) The surface temperature of the heating element is adjusted with high precision, and it is higher than the estimated welding temperature, about 10 ° C. (4) The test specimen is pressed and heated for each heating, and the welding surface temperature is stored or recorded with time. (5) The welding surface temperature for each heating is changed. The change with time is shown as a welding surface temperature curve, with the temperature on the vertical axis and the time on the horizontal axis. (6) Select the desired welding surface temperature and insert a horizontal line indicating the welding surface temperature position on the graph. (7) Copy the actual crimping time of the actual machine on the graph, and copy this crimping time and the desired welding time. Obtain the surface temperature of the heating element in the welding surface temperature curve passing through the intersection of the surface temperatures (8) The obtained surface temperature of the heating element is realized in the actual machine by correcting the difference between the surface temperature in the actual machine and the adjustment set temperature