JPH10235740A - Method of manufacturing polypropylene flat cylindrical molded item for bath lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture efficiently stably a polypropylene flat cylindrical molded item for a bath lid by the use of polypropylene resin. SOLUTION: A dried material blend is put in an extruder to extrusion mold a flat cylindrical molded item. Next, the flat molded item is subjected to air cooling; subsequently, the flat molded item is sent to a sizing device for performing sizing thereto while being cooled indirectly, and then it is subjected to air cooling again through cooling air so as to prevent its extension. Furthermore, the flat cylindrical molded item is sent in a heating chamber to be heated and then cooled indirectly by water as not being in contact with water. While being taken off by take-off rollers, it is air-cooled, followed by cutting the flat molded item into a predetermined length by a cutter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a flat tubular molded article made of polypropylene for a bath lid, and more particularly, to a method of manufacturing a bath lid using a polypropylene resin as a raw material which has been difficult to produce without causing defective products. The present invention relates to a novel method for producing the same stably.

[0002]

2. Description of the Related Art As shown in FIGS. 1 and 2, flat cylindrical molded products 2 having a hollow portion 1 are arranged side by side in a horizontal shape.
Bath doors 4 in the form of doors, which are connected by a soft resin plate 3, are currently the mainstream of bath lids because they are easy to store and have high heat retention, and are widely used in each household.

[0003]

Many of these armored bath lids are made from vinyl chloride or ABS resin, but these have problems such as generation of toxic gas when incinerated. Use is gradually restricted.

[0004] For this reason, polypropylene resins which do not generate toxic gas even when incinerated have attracted attention in recent years. However, polypropylene resins are difficult to mold due to their physical properties. It could not be easily manufactured on an extruder.

In order to produce a flat tubular molded article for a bath lid made of vinyl chloride, a flat tubular molded article is extruded by an extruder and then directly contacted with water while being sized by a sizing device. Cooled by water cooling,
After draining, a work procedure of cutting to a desired length by a cutting machine was used. However, when a polypropylene resin is used as a raw material, the hollow part 1 of the flat cylindrical molded article 2 is used for sizing in such a work procedure. It is easy to cause accidents, such as crushing, or what is supposed to be sent in a long state being cut in the middle, which is a major problem in manufacturing.

[0006] In the molding operation using an extruder, once the operation of the machine is interrupted, it is difficult to control the temperature when resuming the operation.
Since it takes a lot of time to start up, I hate work interruption as much as possible,
Usually, the operation is performed continuously for 24 hours, and the interruption of the operation due to the occurrence of defective products is a very serious problem in production management.

For this reason, in the case of using this polypropylene resin as a raw material, in order to avoid occurrence of the above-mentioned defective product,
It was unavoidable that the operation speed was greatly reduced, but this reduced production efficiency, increased costs,
There was a problem that a PVC bath lid with a low value as a selling point in the market could not compete with the price at all. By the way, the conventional production line for flat tubular molded products for vinyl chloride bath lids flowed at a speed of about 2.6 m / min. When using polypropylene resin as a raw material, in order to eliminate the occurrence of defective products, I had to drop to about 1/3 this speed.

The inventor of the present invention has intensively studied a method for efficiently and stably producing a flat tubular molded product for a bath lid despite the use of a polypropylene resin. The present inventors have succeeded in developing a novel production method capable of producing the same speed as that made of vinyl chloride, and propose the present invention here.

[0009]

SUMMARY OF THE INVENTION The present invention provides a drying step of thoroughly drying a raw material mixture such as polypropylene resin pellets, talc, coloring agent, etc. with a dryer; extruding the dried raw material mixture with an L / D value of 30 or more. An extrusion molding step of putting into a molding machine and extruding a flat cylindrical molded article; an air cooling step of air cooling a flat cylindrical molded article immediately after being discharged from a die of the extrusion molding machine; A sizing step in which the flat cylindrical molded product is sent to a sizing device in which the air pressure at each position of the sizing passage can be arbitrarily adjusted by a vacuum pump, and sizing is performed while performing indirect cooling with cold water at about 10 ° C; An elongation prevention process of air cooling the flat cylindrical molded product again with cold air to prevent the flat cylindrical molded product from elongating Annealing process in which a flat cylindrical molded product is sent into a heating chamber having a temperature control function that can be set to different temperatures at the top and bottom, and passed therethrough to perform heat treatment work; the flat cylindrical molded product after heat treatment is directly contacted with water Re-cooling step of indirectly cooling with water so as not to take place; air-cooling while taking off with a take-off roller; and cutting step of cutting a flat cylindrical molded product to a predetermined length by a cutting machine; An object of the present invention is to solve the above-mentioned problem by manufacturing a flat cylindrical molded product.

[0010]

An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of an example of an armored bathtub using the polypropylene flat tubular molded product for a bathtub according to the present invention, and FIG. 2 is an enlarged front view of a main part thereof. Shaped product 2
A plurality of the pieces are arranged side by side in a lotus shape, and the back surfaces thereof are connected by a soft synthetic resin plate 3 to constitute a bath lid 4. In addition, caps 5 are provided at both ends of the flat cylindrical molded product 2.
Is fitted. FIG. 3 is an explanatory diagram schematically showing a work process according to an embodiment of the present invention in the order of steps. As is apparent from FIG. 3, the present invention comprises a "drying process", an "extrusion molding process", an "air cooling process", a "sizing process", an "elongation prevention process", an annealing process, a "recooling process" and a "cutting process". I have. Next, these steps will be described one by one.

[Drying Step] This is a step of drying a raw material mixture composed of polypropylene resin pellets, talc, a coloring agent and the like. As shown in FIG. The raw material mixture 19 is sufficiently dried. In this embodiment, drying is performed by sending dry air at 120 ° C. for about 120 minutes.

[Extrusion molding step] As shown in FIG. 4, the dried raw material mixture 19 is charged into an extruder 22, and the flat cylindrical molded article 2 is extruded by this. Therefore, in this embodiment,
An extruder having an L / D value (ratio of the effective length (L) of the screw built into the extruder to the outer diameter (D)) of 30 or more is used. Incidentally, in the case of an extruder used in the production of a conventional vinyl chloride bath lid, an L / D value of about 20 was sufficient. In this step, a die 6 is attached to the tip of the extruder 22 used, and the flat cylindrical molded product 2 is continuously discharged from the die 6.

[Air cooling process] This is a step of cooling the flat cylindrical molded article 2 formed by the extrusion molding step. As shown in FIG. The product 2 is air-cooled by cooler cool air and compressor air. In the figure, 23 is a cooler cool air duct, and 24 is a compressor air discharge port. It is important not to cool with water but to cool with air, and this step is important in order to prevent crushing or cutting of the molded article 2 on the flat cylinder in the next sizing step.

[Sizing Step] As shown in FIG. 4 and FIG. 5, the lower part is immersed in a water tank 8 filled with water 7 so that the sizing passage 9 is positioned on the water surface. The flat cylindrical molded product 2 is fed into a sizing device 11 in which a plurality of suction pipes 10 are provided and the suction pressure at each position of the sizing passage 9 can be set arbitrarily.
This is a step of performing sizing while cooling the sizing device 11 with the water 7. The sizing is a process of passing the flat tubular product 2 discharged from the die 6 again through a passage having the same cross-sectional shape to adjust its outer shape. The flat cylindrical molded article 2 having a smooth surface can be obtained. The temperature of the water 7 into which the lower part of the sizing device 11 is immersed is preferably about 10 ° C. In FIG. 5, 25 is a cooling water supply pipe, and 26 is a cooling water drain pipe.

[Elongation Prevention Step] This is a step of air cooling the flat cylindrical molded article 2 whose outer shape has been formed by the sizing step with cool air, and is directed from the air duct 12 to the flat cylindrical molded article 2 as shown in FIG. It is performed by blowing cold air. This step is performed in order to prevent the flat tubular molded product 2 coming out of the sizing device 11 from elongating, and it is important to perform the process not by water cooling but by air cooling. In the production of a conventional vinyl chloride bath lid, the flat tubular molded article 2 after sizing was directly immersed in cooling water in a water tank.

[Annealing Step] As shown in FIGS. 6 and 7, the inside has a hollow tunnel shape, and the inside of an annealing device 15 provided with electric heaters 13 and 14 whose temperature can be separately adjusted vertically is formed in a flat cylindrical shape. By passing heat through the molded article 2 and applying heat thereto from above and below, the arrangement of molecules is changed, and this is a step of performing a so-called annealing that eliminates the occurrence of changes over time. With the provision, the correction of the warpage of the flat cylindrical molded product 2 is also performed at the same time. In this embodiment, the electric heater 1
The length of each of the members 3 and 14 was about 1500 mm.

[Re-cooling step] This is a step of re-cooling the flat tubular article 2 after annealing. As shown in FIG. 6, the flat tubular article 2 is directly cooled by passing through a metal block 16 cooled by water. The re-cooling of the flat cylindrical molded product 2 is performed without contacting the flat cylindrical molded product 2.

[Cutting Step] In this step, the flat cylindrical molded article 2 thus re-cooled is cut into a predetermined length by a cutting machine 17 as shown in FIG. Although not shown, a plurality of flat cylindrical molded products 2 are arranged in a ladder shape, the bottom surfaces of which are connected by a soft synthetic resin plate 3, and a cap 5 is fitted into a small opening to form a bathtub. In this embodiment, a styrene-based elastomer is used as the soft synthetic resin plate 3 so as to have a sufficient slip resistance value.

The flat cylindrical molded product 2 has a single long continuous rod shape from the time it is discharged from the die 6 until it is cut by the cutting machine 17. A feeding device, a take-up roller, and the like are appropriately disposed, and are accurately drawn out at a preset speed. In this embodiment, the feeding speed is about 2.6 m / min, which is equivalent to the speed at the time of manufacturing a conventional vinyl chloride bath lid.

[0020]

The method for producing a polypropylene flat tubular molded article for a bath lid according to the present invention has the above-described configuration, and is free from accidents such as crushing or cutting during production, and can be made of vinyl chloride. It has an excellent effect of being able to stably produce a flat tubular molded product for a bathtub made of polypropylene at almost the same speed as that for manufacturing a bathtub, and is extremely practical.

[0021]

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of an armor-type bath lid manufactured according to the present invention.

FIG. 2 is an enlarged front view of the main part.

FIG. 3 is a process explanatory view for explaining a manufacturing process of a flat tubular molded product made of polypropylene for a bath lid according to the present invention.

FIG. 4 is a perspective view of each device from a drying process to an air cooling process.

FIG. 5 is a side view showing the arrangement of the sizing device.

FIG. 6 is a perspective view of each device from a sizing process to a cutting process.

FIG. 7 is a sectional view of an annealing device.

[Description of Signs] 1 Hollow portion 2 Flat cylindrical molded product 3 Soft synthetic resin plate 4 Bath lid 5 Cap 6 Die 7 Water 8 Water tank 9 Sizing passage 10 Vacuum suction unit 11 Sizing device 12 Air duct 13 Electric heater 14 Electric heater 15 Annealing device 16 Metal block 17 Cutting machine 18 Hopper 19 Raw material mixture 20 Air dryer 21 Dry air 22 Extruder 23 Cooler cool air duct 24 Compressor air discharge port 25 Cooling water supply pipe 26 Cooling water drain pipe

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29C 71/02 B29C 71/02 // B29K 23:00 503: 04 B29L 31:00

Claims (1)

[Claims] 1. A polypropylene resin pellet, talc,
A drying step of sufficiently drying the raw material mixture such as a colorant with a drier; an extruding step of introducing the dried raw material mixture into an extruder having an L / D value of 30 or more and extruding a flat cylindrical molded product; An air cooling step of air-cooling the flat cylindrical molded article immediately after being discharged from the die of the extrusion molding machine; the air is cooled by water and the air pressure at each position of the sizing passage can be arbitrarily adjusted by a vacuum pump. A sizing step in which the flat cylindrical molded product is sent to a sizing device and sizing is performed while performing indirect cooling with cold water of about 10 ° C .; Elongation preventing process to prevent elongation of flat; flat cylindrical molding in a heating chamber with temperature control function that can be set to different upper and lower temperatures Annealing step of sending heat and passing it through to perform a heat treatment operation; Recooling step of indirectly cooling the flat tubular molded article after heat treatment with water so as not to come into direct contact with water; Cutting the flat cylindrical molded product to a predetermined length by a cutting machine, and then cutting the flat cylindrical molded product to a predetermined length by a cutting machine.