JPH059330A - Method for automatically selecting expanding condition - Google Patents

Abstract

PURPOSE:To automatically regulate expanding conditions so as to eliminate fluctuation in expansion ratio and increase productivity by feeding expandable thermoplastic resin particles to a batch type preexpanding machine, preexpanding the resin particles with a heating medium, then automatically regulating conditions to the optimum heating conditions and expanding the resin particles. CONSTITUTION:Raw material particles 36 composed of expandable thermoplastic resin particles in a prescribed amount are fed from a feed port 4 into an expanding vessel 1 of a batch type preexpanding machine composed of the expanding vessel 1, a particle feeding hopper 2 and a heating medium feeding means 3. A heating medium 37 is then fed into the expanding vessel 1 under heating conditions predetermined for the kind and preexpansion ratio of the aforementioned raw material particles to preexpand the raw material particles at a prescribed preexpansion ratio. The time required for the preexpansion is measured with a timer 35 for measuring the heating time. When the measured heating time is not within the optimum heating time zone preset according to the kind and preexpansion ratio of the raw material particles, the heating conditions are automatically regulated with a controlling means 13 to carry out the next preexpansion under the heating conditions after the regulation. Thereby, the expanding conditions are automatically selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically selecting foaming conditions when foamable thermoplastic resin particles are prefoamed by a batch type prefoaming machine.

[0002]

2. Description of the Related Art Usually, when the expandable thermoplastic resin particles are used as raw material particles and pre-expanded by a batch type pre-expanding machine,
A certain amount of raw material particles are supplied into the foaming tank of the pre-foaming machine, and then a heating medium such as steam is supplied to cause thermal expansion, and the upper surface of the foamed particle layer is detected at a predetermined height inside the foaming tank. After pre-foaming until detected by the container, it is taken out of the foaming tank. The expansion ratio of the pre-expanded particles thus obtained depends mainly on the supply amount of the raw material particles.

However, when the pre-foaming is performed rapidly, as shown in FIG.
As indicated by the curve a, the heating time is shortened, but the expansion ratio suddenly increases, and a large difference Δa is generated between the actual expansion ratio and the predetermined expansion ratio due to the operation delay Δt of the level detector. On the other hand, when pre-foaming is performed slowly, as shown by the curve b in FIG. 6, the heating time becomes longer, but the foaming ratio also increases slowly, and the actual foaming ratio and the predetermined expansion ratio caused by the operation delay Δt of the level detector. The difference Δb from the magnification is Δa
Smaller than that. Further, at the same time when the level detector senses the upper surface of the foamed particle layer, the supply of the heating medium is stopped, and cold air is supplied by an air compressor, a blower or the like to stop the foaming. Since it is cooled rapidly, foaming stops immediately, but it takes some time for the upper part of the foaming tank to cool and stop foaming. for that reason,
There may be a difference in foaming ratio between the upper and lower parts in the foaming tank. This phenomenon varies depending on the type of raw material particles and the expansion ratio, and also occurs with the same raw material particles and the same expansion ratio depending on the length of the period from the production of the raw material particles to pre-expansion. Therefore, for pre-foaming, it is necessary to select proper foaming conditions according to the type of raw material particles and the foaming ratio, and perform foaming so that the foaming speed, that is, the heating time falls within the optimum range.

For the above reasons, conventionally, an operator performing a pre-foaming operation measures the heating time required for foaming by once foaming, and the pressure or supply of a heating medium such as steam is supplied according to the measured value. In principle, foaming was performed so that the heating time was appropriate by adjusting the amount.

[0005]

However, according to the above-mentioned conventional working method, it is necessary to find an appropriate foaming condition and foam each time the type of the raw material particles or the expansion ratio changes.
Since this is very complicated, there is a problem that the foaming is often performed up to the final number of times under a predetermined foaming condition for the kind of raw material particles and the expansion ratio. The present invention has been made in view of such conventional problems, and automatically selects appropriate foaming conditions according to the type of raw material particles and the expansion ratio so that the heating time falls within the optimum range. It is an object of the present invention to provide a method for foaming into.

[0006]

In order to achieve the above object, the method for automatically selecting the foaming conditions of the present invention is such that the raw material particles made of expandable thermoplastic resin particles are kept constant in the foaming tank of the batch type prefoaming machine. Amount of the raw material particles, and a heating medium is supplied to the inside of the foaming tank under predetermined heating conditions for the type and expansion ratio of the raw material particles to pre-expand the raw material particles to a predetermined expansion ratio, and the heating time required for the pre-expansion. Is not within the preset optimum heating time zone according to the type of raw material particles and the expansion ratio, the heating conditions are automatically adjusted, and the subsequent pre-foaming is performed under the adjusted heating conditions. It is configured. Then, a mixture gas of water vapor and compressed air is used as the heating medium, and a mixing ratio of water vapor and compressed air is automatically controlled by respective flow rate control valves to automatically adjust heating conditions. May be

[0007]

In the pre-foaming using the method of the above construction, the raw material particles are heated under the heating conditions planned for the type and the foaming ratio in the first pre-foaming, and are pre-foamed to a predetermined expansion ratio. In this case, as the planned heating conditions, the final heating conditions when the same kind of raw material particles were previously pre-expanded at the same expansion ratio are used. Then, the heating time required for pre-foaming is automatically measured,
It is detected whether or not the heating time is within the preset optimum heating time zone according to the type of raw material particles and the expansion ratio. As a result of the detection, when it is included, the second pre-foaming is performed under the first heating condition, but when it is not included, the first heating condition is automatically adjusted, and after the adjustment, the second preliminary expansion is performed. Foaming occurs.
The heating condition adjustment is automatically repeated until the heating time falls within the optimum heating time zone, the heating condition at the time of entering is selected as the final heating condition, and as the heating condition for the subsequent pre-foaming. used. As described above, the final heating condition is also used as the heating condition for the first pre-expanding when the same kind of raw material particles are pre-expanded at the same expansion ratio later.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the batch type pre-foaming machine to which the method of the present invention is applied comprises a foaming tank 1, a granulating hopper 2, and a heating medium supplying means 3. Foaming tank 1
Has a raw material particle supply port 4 at the upper part and a pre-expanded particle discharge port 5 at the lower part, an agitator 6 at the inner center, and a level detector 7 at a predetermined height on the inner wall surface. The discharge port 5 is opened and closed by an air cylinder drive type lid 8. The granulating hopper 2 receives the pre-expanded particles discharged from the discharge port 5 of the foaming tank 1 and supplies the pre-expanded particles to the molding machine from the discharge port 9 at the lower part through the aging silo. Equipped with 10.

The heating medium supply means 3 blows a mixed gas of water vapor and compressed air into the foaming tank 1 as a heating medium, and includes a steam line 11, an air line 12 and a control device 1.
It consists of three. The steam line 11 connects a steam generation source 14 such as a boiler to the bottom of the foaming tank 1 with a pipe 15 having a diameter of 40 A, and a steam pressure of 0.8 kg in the middle from the upstream side.
/ Cm ^{2 to} 1.0 kg / cm ² pressure reducing valve 16 and three electromagnetic flow control valves 17, 18 and 19 with bores of 40 A, 25 A and 15 A, and temperature for measuring the temperature of the heating medium It has a total of 20 and. Each flow control valve 17, 18,
19 has a diameter of 4 branched from the pipe 15 in parallel.
It is connected to the pipes 21, 22, and 23 of 0A, 25A, and 15A. The air line 12 connects an air source 24 such as an air compressor that generates compressed air with a pressure of 2 kg / cm ² to the upstream side of the thermometer 20 of the steam line 11 with a pipe 25 having a diameter of 25 A, and from the upstream side to the middle. Sequentially, the caliber is 10A, 8 respectively
Three A, 6A electromagnetic flow control valves 26, 27, 28 and three fine adjustment needle valves 29, 30, 31 are provided. The flow control valves 26, 27, 28 and the needle valves 29, 30, 31 are paired with the same diameter, and the diameters of the pipes 25 branched in parallel are 10 respectively.
The pipes 32, 33, and 34 of A, 8A, and 6A are connected in series with each other. The control device 13 includes a timer 35 that measures a heating time required for pre-foaming, receives an electric signal of the heating time measured from the timer 35, and receives the flow control valve 1
The optimum heating time zone in which the heating time is preset by controlling the opening / closing of 7, 18, 19, 26, 27, 28 and the opening degree of the needle valves 29, 30, 31 (see FIGS. 2 to 5)
The supply amount and temperature of the heating medium are automatically adjusted so as to enter the inside. With the heating medium supply means 3 having the above-mentioned configuration, it is possible to perform pre-foaming under 12 kinds of heating conditions in which the supply amount and temperature of the heating medium are different as shown in Table 1.

[0010]

[Table 1]

The steam flow control valves 17 and 1 in Table 1 are shown.
8 and 19 and the compressed air flow control valves 26, 27 and 28 are used in combination with four kinds of raw material particles Kanepar UB, SG and S.
When K and FB (both are trade names of expanded polystyrene resin particles manufactured by Kanegafuchi Chemical Industry Co., Ltd.) are pre-expanded at various expansion ratios, the results are shown in Table 2. Table 2
Is input to the control device 13 in advance.

[0012]

[Table 2]

As a result of performing a pre-expansion test on the above-mentioned four kinds of raw material particles with various expansion ratios by using the combination of the flow control valves shown in Table 2, the closed curves shown in FIGS. 2, 3, 4 and 5 for each kind of raw material particles. It was possible to set the optimum heating time zone as shown in the graph. Each graph shows the optimum heating time (sec) on the horizontal axis
Is plotted on the vertical axis. Here, "optimal" means that if the heating time is deviated to the shorter side than the time zone, the foaming rapidly passes, and as described above, the foaming ratio varies between the upper and lower parts of the foaming tank 1, and conversely the heating time. Is shifted to a direction longer than the time zone, it means that the foaming agent (butane gas, etc.) in the raw material particles is decreased and the productivity is decreased. The optimum heating time zone is input to the control device 13 in advance.

In the batch type pre-foaming machine constructed as described above, first, the raw material particles 36 of the type SG are expanded to a foaming ratio of 5
The case of pre-foaming at 5 times will be described based on Table 3.

[0015]

[Table 3]

The supply amount of the raw material particles 36 is 17.3 kg each time calculated from the expansion ratio. When the raw material particles 36 are supplied from the supply port 4 into the foaming tank 1 in the first foaming, the controller 13 selects the combination of the flow rate control valves 18 and 26 from Table 2 stored as the heating condition, and the temperature 99 The heating medium 37 at a temperature (see Table 1) is blown into the foaming tank 1 to pre-foam the raw material particles 36 at a predetermined ratio. When the level detector 7 senses the upper surface of the pre-expanded particles 38, the foaming is completed, the pre-expanded particles 38 are discharged from the discharge port 5 into the granulating hopper 2 and sized by the sieve 10, and then from the discharge port 9. It is supplied to the molding machine via the aged silo. On the other hand, timer 3
5 measures the heating time of 116 seconds required for foaming, and sends the measured time to the control device 13 as an electric signal. Upon receiving the signal, the control device 13 detects that the measurement time of 116 seconds is within the stored optimum heating time zone 92 seconds to 128 seconds of FIG. 3, and performs the second foaming under the same heating condition.
In this way, as shown in Table 3, as long as the heating time in each foaming is within the optimum heating time zone, the same heating condition is applied until the final foaming. Controller 13
Keeps the memory of the heating condition of the first foaming as it is,
Prepare for pre-foaming with the same raw material and the same magnification at a later date. Table 4 shows a case where the raw material particles 36 of SK type were pre-expanded at an expansion ratio of 76 times in the same manner as described above.

[0017]

[Table 4]

In the first foaming, from Table 2, the flow control valve 1
A combination of 7 and 27 is selected, but heating time 242
Since the second is too long than the optimum heating time zone 164 seconds to 216 seconds in FIG. 4, the combination of the flow control valves is 1 in the second foaming.
Changed to 7 and 28. However, since the heating time 234 seconds is still longer than the optimum heating time zone, the combination of the flow rate control valves is changed to only 17 again in the foaming after the third time, and the heating time 185 seconds to 194 seconds are all the optimum heating time. It is in the obi. By the way, in the first and second foaming, the pre-foamed particles 38 showed shrinkage due to over-foaming. The control device 13 corrects and stores Table 2 to the foaming heating conditions for the third time and thereafter, and prepares for preliminary foaming at a later date.
Further, Table 5 shows a case where the raw material particles 36 of FB type were pre-foamed at a foaming ratio of 60 times.

[0019]

[Table 5]

In the first to third foaming, the combination of the flow rate control valves 18 and 27 selected from Table 2 is maintained, and the heating time 162 seconds to 167 seconds is the optimum heating time zone 124 seconds to 169 seconds in FIG. Although it is included, it is too close to the upper limit, so the combination of flow control valves is 1 in the fourth and subsequent foaming.
It was changed to 8 and 28, and the heating time is proper from 150 seconds to 154 seconds. The control device 13 corrects and stores Table 2 to the heating conditions for foaming after the fourth time, and prepares for preliminary foaming at a later date.

As described above, the control device 13 always stores the optimum heating condition and applies it to the pre-foaming of the same raw material and the same magnification. However, when further fine adjustment of the heating condition becomes necessary. The opening degree of the needle valves 29, 30, 31 is adjusted. In the above embodiment, the heating conditions are adjusted stepwise by the combination of opening and closing of the electromagnetic type flow control valves provided for steam and compressed air, respectively. It is also possible to provide one electronic flow control valve for each of the air conditioner and the compressed air, and to continuously adjust the heating conditions by continuously adjusting the openings of both flow control valves. can get.

[0022]

As described above, the present invention automatically selects an appropriate heating condition according to the type of raw material particles and the expansion ratio in the prefoaming by the batch type prefoaming machine,
Since the pre-foaming is performed so that the heating time falls within the optimum heating time zone, the foaming can be performed at the optimum foaming speed. Therefore, not only is there no variation in the expansion ratio between the upper and lower parts in the foaming tank, but productivity is improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a batch type pre-foaming machine to which the present invention is applied.

FIG. 2 is a graph showing the optimum heating time zone according to the type of raw material particles and the expansion ratio.

FIG. 3 is a graph showing an optimum heating time zone according to the type of raw material particles and the expansion ratio.

FIG. 4 is a graph showing an optimum heating time zone according to the type of raw material particles and the expansion ratio.

FIG. 5 is a graph showing an optimum heating time zone according to the type of raw material particles and the expansion ratio.

FIG. 6 is a graph showing the influence of the length of heating time on the variation in foaming ratio.

[Explanation of symbols]

1 foaming tank 3 heating medium supply means 11 Steam line 12 Air line 13 Control device 17, 18, 19 Flow control valve for steam 26, 27, 28 Flow control valve for compressed air 35 Timer for measuring heating time 36 Raw material particles 37 Heating medium

Claims (2)

[Claims] 1. A constant amount of raw material particles composed of expandable thermoplastic resin particles are fed into the foaming tank of a batch type pre-foaming machine, and the inside of the foaming tank is heated under predetermined heating conditions for the type and expansion ratio of the raw material particles. A heating medium is supplied to pre-expand the raw material particles to a predetermined expansion ratio, and the heating time required for the pre-expansion is within the optimum heating time zone preset according to the type of the raw material particles and the expansion ratio. When not included, the above-mentioned heating conditions are automatically adjusted, and the subsequent pre-foaming is carried out under the adjusted heating conditions. 2. The heating medium is composed of a mixed gas of water vapor and compressed air, and the mixing ratio of water vapor and compressed air is automatically controlled by respective flow rate control valves to automatically adjust heating conditions. The method for automatically selecting foaming conditions according to claim 1.