JPS6326549A - Method and instrument for automatic measurement of specific gravity of foamed particle - Google Patents

Abstract

PURPOSE:To measure the true specific gravity of foamed particles with good accuracy in a short period by packing the foamed particles which is preliminarily measured of the weight into one of two hermetic vessels and determining the volume of the foamed particles from a pressure change by a decrease of the inside volume. CONSTITUTION:A pressurized air supply port 2 and a pressurized air discharge port 4 are connected to a pressurized vessel 1 which is one of the hermetic vessels. A foamed particle supply port 10 and a foamed particle discharge port 11 are connected to a volume measuring vessel 9 which is the other hermetic vessel. The volume measuring vessel 9 is connected via a pressure equalizing port 3 to the pressurized vessel 1. Pressurized air is first fed from the pressurized air supply port 2 to the vessel 1 and after the pressure is increased up to the specified pressure, the foamed particles which are preliminarily measured of the weight are supplied through the foamed particle supply port 10 into the volume measuring vessel 9. A pressure equalizing valve 6 is then opened to equalize the pressures in the volume measuring vessel 9 and the pressurized vessel 1 and after the pressure is measured, a foamed particle discharge valve 13 is opened to discharge the foamed particles through the foamed particle discharge port 11 to the outside of the system. The volume of the foamed particle is thereupon determined from the pressure change and further the true specific gravity is calculated by using the prescribed equation from the resulted volume and the preliminarily measured weight.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an automatic specific gravity measurement method and device for pre-expanded particles used in in-mold foam molding. The present invention relates to a method and apparatus for measuring specific gravity.

"Prior Art and Problems" Conventionally, in-mold foam molding has been performed using pre-expanded particles of polystyrene, polyethylene, and polypropylene. In the above-mentioned in-mold foam molding, pre-expanded particles are generally filled into a mold, heated and fused, and then cooled and taken out from the mold to obtain a molded product.

By the way, in these pre-foaming and molding processes, control of the specific gravity of the pre-expanded particles and the specific gravity of the molded product has not been done in the past, despite the fact that it is closely related to the quality and cost of the molded product. The method is not necessarily satisfactory.

For example, JP-A No. 56-53612 discloses a method for automatically measuring the apparent specific gravity of pre-expanded particles. Since the apparent specific gravity is calculated, there is a drawback that there is large variation depending on the degree of filling and the shape of the particles.

On the other hand, as a method for measuring the true specific gravity, a method is usually used in which the weight of the pre-expanded particles is measured in advance, the volume of the pre-expanded particles is measured by the submersion method, and the volume is converted. Measuring expanded particles is a complicated operation, and since the measured pre-expanded particles get wet with water, the pre-expanded particles may stick to the equipment, which not only takes time and effort to clean up afterwards, but also prevents the pre-expanded particles from getting wet. This includes problems such as the inability to reuse the particles.

"Means for Solving the Problems" The present invention has been completed in order to solve the above problems.

That is, the first aspect of the present invention is to measure the internal pressure of two closed containers, and to calculate the pressure caused by reducing the internal volume of one of the closed containers by filling the foamed particles whose weight has been measured in advance into one of the closed containers. The second aspect of the present invention is an automatic specific gravity measurement method for foamed particles, which is characterized in that the volume of the foamed particles is determined by detecting a change, and the true specific gravity of the foamed particles is measured. It consists of two connected sealed containers, one of which has a foamed grain supply port and a foamed grain supply valve at the top.
The lower part is equipped with a foamed grain discharge port and a foamed grain discharge valve, and the other sealed container is equipped with a pressurized air supply port and a pressurized air supply valve, a pressurized air discharge port and a pressurized air discharge valve, and Each of these includes an automatic specific gravity measuring device for foamed particles equipped with a recorder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an apparatus used in the present invention will be explained based on the drawings.

In Fig. 1, a pressurized air supply port (2), a pressure equalization pipe (3), and a pressurized air exhaust port (4) are connected to a pressurized tank (1), which is one of the closed containers. Supply valve (5)
, a pressure equalization valve (6), and a pressurized air exhaust valve (7). (8) is a pressure recorder. The volume measuring tank (9), which is the other airtight container, is connected to a foam grain supply port (10) at the top and a foam grain discharge port (11) at the bottom. 13).

Further, the volume measuring tank (9) is connected to the pressurizing tank (1) through the pressure equalizing pipe (3). The shapes of the pressure tank (1) and the volume measurement tank (9) are not particularly limited;
) is preferably formed into a conical shape to facilitate discharge of the pre-expanded particles after volume measurement. In addition, there are no particular limitations on the capacity, but there may be a pressurized tank (1), a volume measuring tank (
9) Both 0.2-30j! The degree is practical. Both tanks may have the same volume or different volumes.

To measure the specific gravity of foamed particles using the above device, the first step is to pressurize the pressure tank (1), close the pressure equalization valve (6) and exhaust valve (7), and supply pressurized air. When the valve (5) is opened, pressurized air is fed into the pressurized tank (1) from the pressurized air supply port (2) and the pressure is increased to a constant pressure, and then the supply valve (5) is closed. The pressure inside the pressurized tank at this time is p, mmAq,,G
shall be.

As a second step, the foamed grains are fed to the volume measuring tank (9), that is, with the foamed grain discharge valve (13) closed and the foamed grain supply valve (12) open, the foamed grains are weighed in advance. After the grains have been fed into the volumetric tank (9) through the foamed grain supply port (10), the foamed grain supply valve (12) is closed.

The third step is to equalize and measure the pressure in the volume measuring tank (9) and pressurizing tank (1).The pressure equalizing valve (6) opens and the pressure recorder (8) shows the equalizing pressure in both tanks. The pressure P, mmAq, G
is displayed.

The fourth step is to discharge the foamed grains from the volume measuring tank (9) and measure the atmospheric pressure.The foamed grain discharge valve (13) is opened and the foamed grains in the volume measuring tank (9) are discharged from the foamed grain outlet (13). ) is discharged to the outside of the system. Thereafter, the exhaust valve (5) is opened and the pressure recorder (8) measures and displays atmospheric pressures P, mmAq, and G.

After the series of steps described above is completed, pressurized air is supplied into the pressurized tank (1) again, and the steps from the first step described above are repeated to perform the next measurement. Note that the order of the first to fourth steps described above is not restricted, and may be rearranged as appropriate.

From the above measurement values, the volume (Vx) of the expanded beads is determined by the relational expression (1) between gas volume and pressure: V X = ((P+V++PtVz)-h(V++
Vz)l /(P!h) (1) (However,
V is the volume of the pressurized tank, v2 is the volume of the volumetric tank), and the true specific gravity (ρ) of the foamed grains is calculated from the following formula (2)% formula% (2
1 (where W is the weight of the expanded beads used in the measurement).

FIG. 2 is a schematic diagram showing an example of a system from sampling foam beads to weighing them.

The foamed grains (21) are sampled by connecting the sampling location to the weighing machine installation location via a sampling pipe (23) equipped with a two-way valve (22). This two-way valve (
The role of 22) is to switch from foamed grain suction to atmospheric suction shortly before the sampling tank (24) is filled, to prevent the sampling tube (23) from being filled with foamed grains and causing a blocking blockage. The timing of switching the two-way valve (22) from foamed particle suction to atmospheric suction is set according to the actual situation. Also, the switching is controlled by a timer (not shown).
carried out by The sampling tank (24) has a cylindrical shape with a cone, has a volume of several 101, and has a wire mesh (2 fl) near the top end.
5) is provided. This money! (25) is used to separate expanded particles from entrained air. The capacity of the exhaust blower (29) is determined by the length and diameter of the sampling pipe.

The foamed particles received in the sampling tank (24) are supplied to the sampling receiver (30) through the sample outlet valve (27). The operation timing of the sample outlet valve (27) is set according to the actual situation using a weighing machine and a volume measuring system as shown in FIG.

Also, when the sample outlet valve (27) is operating.

At this point, if the exhaust blower (29) is activated, foam particles cannot be supplied to the sample receiver (30), so a system (not shown) for controlling the operation of the exhaust blower (29) is installed.
is provided separately. The sample receiver (30) has an actual volume of about 200 cc to 201 cc, and is provided with a butterfly valve (31) at the bottom for discharging foam particles. There are two or more sample receivers (30), and a sampling tank (24).
The sample outlet valve (27) is operated directly below the foamed pellets, which are supported by the rotating disk (32) so that they can be moved directly above the automatic weighing device (40). )
It is rotationally driven by. The rotating disk (32) is provided with a rising part on its circumference to prevent the foam particles from escaping to the outside, and the foam particles spilled onto the rotating disk (32) are discharged via the excess particle discharge pipe (34). and is returned by the discharge blower (35).

When the sampling receiver (30) supplied with foam particles moves directly above the weighing receiver (36), the butterfly valve (31)
) opens and falls into the weighing receiver (36) and is supplied.

The operation of the butterfly valve (31) is controlled by a rimming switch and a timer (not shown).

The foamed grains supplied to the weighing receiver (36) are weighed by an automatic weighing machine (40) and held as a signal. When weighing is completed, the linear cylinder (38) moves, the weighing receiver (36) is clamped by the weighing receiver holder (37), and the linear cylinder (38) returns to its original position. The original position of the linear cylinder (38) is the position where the volume measuring tank hopper (41) is located directly below the weighing receiver (36).

At the same time that the weighing receiver (36) returns to its original position, the weighing receiver (36) is rotated by the rotating cylinder (39).
Rotates at 80℃, and the foamed particles are placed in the hopper for volume measurement tank (41)
It falls and is supplied.

The weighed foamed beads are supplied into the volume measuring tank (9) by the foamed grain supply valve (12) as described above, and the volume is automatically measured.

"Action/Effect" According to the present invention, it is possible to measure the true specific gravity of expanded beads in a shorter time and more accurately than with the conventional submersion method.

"Examples" The present invention will be described below with reference to Examples, but it goes without saying that the present invention is not limited in any way by these.

Example 1 The true specific gravity of foamed polypropylene granules was measured in the following manner; (1) Measurement sample: foamed polypropylene granules (2) Measuring device: as shown in Figure 1 ■Electronic balance: J manufactured by Nagabin Seisakusho P-3000W type, measurement accuracy 10mIIIg) ■Pressure tank: W4 pressure container ■Volume measurement tank: WII pressure container ■Pressure gauge: Manostar gauge type (Sugihara Keiki W-O type,
Measurement accuracy IQmo+Aq, ) (3) Measurement method: ■Measure the volume of the pressurized tank using the water filling method: V + (cc)
■Measure the volume measurement tank using the water filling method: Vz (cc) ■Weigh the foamed grains: W (g) ■Measure the pressure when pressurizing the pressure tank: P + (mmAq)
, G) ■ Pressure when the measurement tank is not pressurized (atmospheric pressure): P
z-0 (mmAq, G) ■Measurement of the pressure when the measurement tank containing expanded beads is equalized with the pressurized tank from a sealed state: Pco (llllAQ, G) (4) Measurement result; V+ -10, OOO (c c) Comparative Example 1 Measurement was carried out using the submersion method as follows: (1) Measurement sample: polypropylene foam granules (same as Example 1) (2) Measuring device ■Electronic scale; implementation Items used in Example 1 ■ Graduated cylinder: maximum 200 cc, minimum 2 cc ■ Foam grain presser (details are shown in Figure 3).

In the figure, (50) is a measuring cylinder, (51) is a foam grain presser, (52) is a foam grain, and (53) is a water surface.) (3) Measuring method: ■Measure the weight of foam grains: W ( g) ■Pour approximately 100cc of water into a graduated cylinder, and measure the amount of water with the head of the foam grain presser immersed approximately 1cm below the water surface: V, ((, C) ■The foam beads weighed in ■ above. Place it in a measuring cylinder, and make sure the head of the presser is about 1cm below the water surface.
Press down and measure the amount of water so that: Vz (cc) True specific gravity of foamed grains (ρ) ρ-W/ (Vz -V+) (g/cc)
(4) Measurement results: Measured value of true specific gravity ρ of expanded beads: X -0,0307 (g/cc) σ -0,0016

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the apparatus of the present invention, Fig. 2 is a schematic diagram showing an example of a system including sampling and weighing of expanded beads, and Fig. 3 is a submersion method used in Comparative Example 1. FIG. 1 is a schematic diagram of a measuring device according to. 1... Pressurized tank, 2... Pressurized air supply port 3.
... Pressure equalization pipe, 4 ... Pressurized air outlet 5 ... Pressurized air supply valve, 6 ... - Pressure equalization valve 7 ... Pressurized air exhaust valve, 8 ... Pressure recorder 9 ...・Volume measurement tank, 10
... Foamed grain feeding port 11... Foamed grain discharge port, 12.
...Foamed grain supply valve 13...Foamed grain discharge valve 3 diagram

Claims (1)

[Claims] Measure the internal pressure of one or two closed containers, and fill one of the closed containers with foamed particles whose weight has been measured in advance to reduce the internal volume of the closed container. 1. A method for automatically measuring the specific gravity of foamed particles, characterized in that the volume of the foamed particles is determined by detecting the volume of the foamed particles, and the true specific gravity of the foamed particles is measured. 2. Consists of two sealed containers connected by a pressure equalizing pipe equipped with a pressure equalizing valve; one sealed container has a foamed grain supply port and foamed grain supply valve at the top, and a foamed grain outlet and foamed grains at the bottom. the other closed container is equipped with a pressurized air supply port and a pressurized air supply valve, a pressurized air discharge port and a pressurized air discharge valve, and is equipped with a pressure recorder. Specific gravity measuring device.