JPH0127846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an apparatus for pre-foaming expandable thermoplastic resin particles, such as expanded styrene beads, and in particular, an apparatus for pre-foaming expandable thermoplastic resin particles, such as expanded styrene beads. This invention relates to an easy continuous prefoaming machine.

In the case of bead-processed styrene foam, etc., the raw material, styrene foam beads, is usually foamed to the required apparent specific gravity before being molded in a mold using a molding machine.In the industry, this is called pre-foaming. For pre-foaming, there is a continuous method in which raw material particles such as the expanded styrene beads mentioned above are continuously supplied into a cylindrical foaming container, heated and foamed with a heating medium, and continuously taken out, and a continuous method in which raw material particles for a fixed amount are supplied into the foaming container. However, there are two methods: a batch method in which the foam is heated and foamed and taken out in batches. However, in the conventional pre-foaming described above, there is considerable variation in the expansion ratio within the foaming container, which naturally affects the quality of the foamed molded product and creates products that require a high level of quality. It had become a big bottleneck. Among these, especially in continuous pre-foaming, there is a large difference in the circumferential speed of the stirring blades installed inside the foaming container near the wall and in the center, and this is a major factor in the variation in foaming ratio. .

The difference in circumferential speed of the stirring blade near the wall and the center of the foaming container has a large effect on the stirring force, but at the same time, the effect of the shear force of the stirring blade is insufficient. The reality was that blocking could not be avoided.

For example, if we look at the pre-foaming machines currently in use, the specifications are as follows: Processing capacity: 300Kg/H Container dimensions: 750 x 790H (mm) Stirring blade dimensions: 720 (mm) Stirring Stirring shaft diameter: 76〓 (mm) Stirrer rotation speed: For a pre-foaming machine with 90rpm, the circumferential speed at the tip of the stirring blade is 3.14 x 0.36 (m) x 1.5 (1/sec) = 1.7 (m/sec) The circumferential speed of the stirring shaft surface is 3.14 x 0.036 (m) x 1.5 (1/sec) = 0.18 (m/sec) Therefore, the circumferential speed ratio inside the container is 0.18/1.7 = 1 between the center of the container and the outer peripheral wall. /9.44, that is, there is a circumferential speed difference of about 10 times. It can be seen from this result that sufficient stirring is not performed near the stirring shaft due to the low circumferential speed, making it difficult to apply shearing force to the pre-expanded particles, and blocking is likely to occur.

Thus, the present invention reduces the speed difference between the inner and outer circumferences in the foaming container in a continuous pre-foaming machine,
The first step is to improve the stirring conditions for pre-foaming.
The purpose of

Furthermore, considering the flow path of pre-foamed particles inside a normal pre-foaming machine, the raw material particles supplied to the lower part of the foaming container are foamed while being stirred by a stirring blade by steam heating from a steam supply slit. As this foaming progresses, the volume expands, the apparent density of the particles decreases, the particles become lighter, rise to the top of the container, and are discharged from the overflow port at the top, completing the pre-foaming operation. In this case, the foaming ratio is 10 to 100 times, and generally around 50 times, but even if you carry out the preliminary foaming operation with the aim of foaming 50 times, the average value is that a product with a magnification of 50 times will be obtained. too,
Stirring causes vertical flow, resulting in products with low magnification and large variations.

This can be improved by, for example, reducing the diameter and increasing the height of the container, but since the amount of steam is constant, this will reduce the steam supply density per unit base area. As the size increases, the problem of easy blocking will inevitably occur.

Thus, the second object of the present invention is to provide a novel continuous type pre-foaming machine that can prevent blocking regardless of the diameter of the container and can equalize the expansion ratio.

Hereinafter, specific embodiments of the pre-foaming machine of the present invention will be explained based on the accompanying drawings, but the present invention is not limited to the following examples and can be modified in various ways without departing from its purpose. Of course.

FIG. 1 shows an example of the pre-foaming machine of the present invention, in which 1 is a cylindrical container forming a foaming tank, 2 is a stirring shaft equipped with stirring blades 3, and 4 is a pre-foaming machine provided on the top of the container 1. A particle discharge chute, 5 a raw material particle supply device consisting of a screw conveyor with a hopper provided at the bottom of the container, 6 a steam supply slit,
7 is a steam supply inlet, 8 is a drain outlet, 9 is the stirring shaft driving device, and 12 is a steam chamber, and each of these parts is exactly the same as a conventional prefoaming machine. Therefore, with the above configuration, raw material particles are supplied into the container 1 by the raw material particle supply device 5,
In the retention section 11, the steam blown from the steam supply slit 6 at the bottom of the container is heated to about 100°C, and the foaming agent in the raw material particles performs heating and foaming. This is different from conventional pre-foaming machines in that the rotation of the shaft 2 rotates the stirring blades 3 attached to it, which together with its shearing action prevents blocking, that is, mutual fusion of the pre-foamed particles, to some extent. Never.

However, in the pre-foaming machine shown in FIG. 1, since the prevention of blocking by the pre-foaming machine with the above-mentioned configuration is incomplete, a hollow cylinder 10 is provided on the outer periphery of the stirring shaft 2, and a hollow cylinder 10 is provided on the outer periphery of the stirring shaft 2. The aim is to reduce the amount of water and improve the stirring condition.

In this case, the pre-expanded particles are usually 2 to 5 mm spherical solids, so they have poor fluidity compared to liquids and are difficult to flow unless a fairly strong stirring force is applied. According to the method of the present invention,
It should be noted that this is sufficiently guaranteed by the reduction of the circumferential speed difference.

Now, considering the specific specifications of the pre-foaming machine according to the present invention, and comparing it with the conventional case described above, container dimensions: 776 × 790H (mm) Stirring blade dimensions: 746 (mm) Stirring shaft diameter ;76〓(mm) Stirrer rotation speed: 90rpm Hollow cylinder dimensions: 20〓×790H/(mm) According to the above specifications, the circumferential speed ratio inside and outside the container is 200/776=
It is 1/3.88, that is, compared to the conventional peripheral speed ratio of 1/9.44, it is 1/3.88, which is about 2.5 times better, and it is confirmed that the stirring condition is improved and blocking is significantly improved.

Furthermore, with the configuration of the present invention described above, the scale-up of the pre-foaming machine becomes easy, and its practicality is further doubled.

As a specific example of this, FIG. 2 shows an example of a pre-foaming machine having twice the performance of the pre-foaming machine shown in FIG. 1. According to Fig. 2, the height of the container is approximately twice that of the container shown in Fig. 1, and the pre-foaming machine in Fig. 1 is used in two stages. The supply device 5 is provided at the lower part of the upper container, while the discharge chute 4 for overflowing the pre-expanded particles is provided at the upper part of the lower cylindrical container. The stirring shaft 2 is configured to be rotated all at once by a drive device 9, which is a common shaft passing through the upper and lower stages, and forms retention portions 11 and 11' in each of the upper and lower containers, respectively. Each stage of containers is provided with a steam supply slit 6, 6' and a drain outlet 8, 8', respectively.

In a pre-foaming machine with such a configuration,
The hollow cylinder 10, which is a feature of the present invention, is installed around the stirring shaft 2 so as to communicate with the center of both the upper and lower containers, and the upper part of the hollow cylinder 10 is provided with a flow-down mechanism that automatically flows down the pre-expanded particles that have risen to the upper stage. The pre-expanded particles heated and foamed in the upper stage are further retained in the lower stage, where they continue to be heated and expanded and are discharged from the discharge chute 4.

Reference numeral 13 denotes a pre-foamed particle scraping member provided at the lower end inside the hollow cylinder 10.

Of course, the method of simply connecting two ordinary pre-expanding machines in series is also theoretically effective for sharpening the average value of the pre-expanding ratio; however,
This is not practical from the following two points.

(b) Since the pre-expanded particles discharged from the first unit are solid foam particles and have a pulsating flow, it is necessary to place a cushion section at the joint of the second stage.
The issue is the capacity of the cushion; if it is too large, the pre-foamed particles in the cushion bath will cool down, making it necessary to reheat the cushion to a temperature close to 100°C. Also, if the capacity of the cushion tank is small,
Since the processing capacities of the first and second machines are fixed, they cannot be balanced and overflow, resulting in a loss.

(b) As for the second feeding device, a pushing device using a rotating screw is economically practical, but it has the disadvantage that the pre-expanded particles are subjected to compressive force by the screw and undergo contraction deformation.

On the other hand, the device of the present invention is an extremely effective device in which the above-mentioned drawbacks have been corrected.

In addition, in the apparatus of the present invention, the diameter and height of the container can be set arbitrarily and are selected appropriately depending on the processing capacity, but in order to further increase the capacity, it is possible to use multiple stages and increase the processing speed at each stage. Hurry up,
It can also be easily designed to increase processing power.

In any of these cases, the diameter of the hollow cylinder can also be selected as appropriate to suit each case, but usually the diameter of the hollow cylinder is 1/1/2 of the diameter of the container.
The most preferable range is about 3 to 1/4.

As described above, the device of the present invention is equipped with a hollow cylinder around the outer periphery of the stirring shaft, and the difference in velocity between the inner and outer circumferential surfaces within the container is significantly reduced, and relatively uniform stirring is performed, and the stirring added to the pre-expanded particles is The shearing force by the blades is sufficient, which greatly reduces the amount of blocking that occurs during pre-foaming, and also ensures uniformity of temperature distribution and expansion ratio of pre-foamed particles, which requires stability in the average expansion ratio. In addition, it is easy to manufacture a pre-foaming machine that can be scaled up and has a large processing capacity, and in particular, by using an upper and lower two-stage foaming system, This is an industrially advantageous pre-foaming machine that far exceeds the performance of conventional pre-foaming machines, as the foaming ratio in the upper and lower sections, combined with the automatic downstream mixing, further promotes the uniform effect of the stirring blades.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the pre-foaming machine of the present invention, and FIG. 2 is a schematic cross-sectional view of a two-tiered pre-foaming machine according to a modified embodiment of the pre-foaming machine of the present invention. 1... Cylindrical container, 2... Stirring shaft, 10... Hollow cylinder, 11, 11'... Retention part.

Claims (1)

[Claims] 1. A cylindrical container 1 is provided with a stirring shaft 2 at its center, a raw material particle supply device 5 at the bottom of the container 1, and a pre-expanded particle discharge chute 4 at the top of the container 1. 1 Heating device 6 using a heating medium at the bottom,
In a pre-foaming machine equipped with 7, 8 and 12,
Inside the cylindrical container 1, there is a slight gap between the outer periphery of the stirring shaft 2 and the shaft 2, and the cylindrical container 1
A pre-expanding machine for expandable thermoplastic resin particles, characterized in that a hollow cylinder 10 is arranged concentrically with a pre-expanded particle retention section 11 space between the pre-expanded particle storage section 11 and the inner wall. 2 A cylindrical container 1 divided into two vertically serial stages has a stirring shaft 2 penetrating the top and bottom in the center thereof, a raw material supply device 5 is installed at the bottom of the upper stage, and a pre-expanded particle discharge chute 4 is installed at the upper part of the lower stage. In addition, heating devices 6, 7, 8, 1 using heating medium are provided at the bottom of each stage.
2, 6', 7', 8', and 12', and inside the cylindrical container 1, there is a slight gap between the outer periphery of the stirring shaft 2 and the shaft 2, and the cylindrical Upper and lower pre-expanded particle retention sections 11, 1 are provided between the inner wall of the container 1 and the inner wall of the container 1.
A hollow cylinder 10 that communicates the upper and lower chambers with a 1' space.
1. A pre-expanding machine for expandable thermoplastic resin particles, characterized in that the pre-expanded particles are provided concentrically to form a flow path for the pre-expanded particles.