JPH05318555A - Method for extrusion molding of thermoplastic resin material - Google Patents

Abstract

PURPOSE:To prevent the damage of quality due to the lowering of the dimensional accuracy of a product and the increase of a fish eye by using an extruder to which a level meter having a stirrer provided to the lower part thereof is provided so as to position the same inside the line formed by allowing the inclined locus surface from the vertical plane drawing the end ege of a lower discharge port to cross the upper opening surface of a hopper. CONSTITUTION:A powdery thermoplastic resin material 3 mixed with a recovered product in a predetermined ratio is received in the hopper 1 of an extruder from the supply pipe 2 provided above the hopper 1 and a discharge port 4 is provided to the lower part of the hopper 1 to be connected to the extruder 5 and the thermoplastic resin material 3 in the hopper 1 falls to be sent into the extruder 5 by a screw 6. A level meter 7 is provided to the hopper 1 so as to be positioned inside the line L formed by allowing the inclined locus surface S opened upwardly and outwardly at 15 deg., pref., at 10 deg. from the vertical plane V drawiang the upper part of the hopper 1 and the end edge of the discharge port 4 to cross the upper opening surface of the hopper 1 and has a stirrer 7 provided to the lower part thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of extrusion molding a thermoplastic resin material, and more particularly, to a recovery product of the thermoplastic resin material such as both ends (ears) of the sheet generated when finishing the product in the extrusion molding of a T die sheet. Even when mixed with a powder material, it is possible to always ensure a uniform amount of extrusion molding with a uniform blending, which results in a sheet with high thickness accuracy, less fish eyes, and excellent quality extrusion molding. The present invention relates to an extrusion molding method of the obtained thermoplastic resin material.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resin products such as pipes, profile products, extruded films and electric wires have been manufactured by extrusion molding. In these extrusion moldings, the mixed powder material charged from the hopper is kneaded and gelled in the process of being conveyed by the screw in the extruder, extruded from the die at the tip of the extruder to be molded into a predetermined shape, and cooled to produce the product. Becomes In this manufacturing process, it is important to maintain the dimensional accuracy of the product, and particularly in the extrusion of the T die sheet, the product thickness accuracy is required. It is also required to make the gelling zone in the cylinder uniform to reduce fish eyes and improve the quality. In order to satisfy these requirements, the powder material in the extruder is always uniform in composition,
And it is important to keep the supply constant.

For this reason, in the conventional extruder for T die sheet, when a level meter is attached to the middle or upper part of the inclined wall surface of the material receiving hopper to keep the powder material amount in the hopper constant and to drop the screw naturally. Measures were taken to keep the pressure of the. This will be described with reference to the apparatus shown in FIGS. 3 and 4. In this apparatus, the powder material 32 in the storage tank 31 is sent by a suction machine 33 through a pipe 34 to a hopper 36 equipped with a level meter 35, and the extruder is The sheet is kneaded and gelled at 37, extruded as a sheet 39 from the T die 38, cooled by a cooling roll 40, and wound up.

FIG. 4 shows in sequence the process in which the powder material 32 in the hopper 36 of this apparatus is discharged by the screw 41 of the extruder 37. In FIG. 4 (a), the powder material 32 is discharged by the screw 41. Then, the amount is reduced and the state is detected by the level meter 35. The information detected by the level meter 35 is the suction device 33.
The powder material 32 in the storage tank 31 is supplied into the hopper 36 by the operation thereof, and the state shown in FIG. Normally, the powder material 32 in the hopper 36 is maintained in this state because the supply by the suction device 33 and the discharge by the screw 41 are continuously performed. , (D), a bridge or a cavity 42 may be formed in the central portion of the hopper 36. In this case, although the supply of the powder material 32 to the screw 41 is interrupted or the capacity is reduced, Since the level meter 35 does not detect, the pressure applied to the powder material 32 decreases and the supply amount to the screw 41 decreases, or the bridge suddenly collapses and a large amount of powder material 32 is supplied to the screw 41 at one time. However, the amount of the powder material 32 in the screw 41 is largely varied, and the accuracy of the thickness of the sheet 39 from the T die 38 is lowered and the fish eye is increased.

Therefore, in order to prevent the formation of bridges and cavities in the hopper, measures have been taken such as installing a stirrer in the hopper and giving vibration to the hopper itself. However, in the extrusion of T-die sheet, it is necessary to cut both ends with a predetermined width when winding the product, and both ends (ears) are cut into chips of 2 to 6 mm square and mixed with the powder raw material. Has been reused. Since this recovered product has a different specific gravity and shape from the powder raw material,
Even if they are mixed evenly before the hopper is charged, the ratio of recovered products is large, and if they are agitated or vibrated in the hopper, the recovered products will separate and float up, and will not be uniform when fed to the screw. .. As a result, the amount of extrusion varied, unevenness in product thickness due to nonuniform gelation and increase in FE occurred, and a better product could not be obtained.

[0006]

Accordingly, the object of the present invention is to prevent the powder raw material and the recovered product from being separated in the hopper even when the powder raw material is mixed with the recovered product in the extrusion molding of the thermoplastic resin. A thermoplastic resin material that does not impair the quality by reducing the dimensional accuracy of the product or increasing the fisheyes, because the supply amount fluctuates even if it becomes uniform or creates bridges and cavities even if it is not separated. An extrusion molding method is provided.

[0007]

As a result of various studies to solve this problem, the inventors of the present invention have found that the mounting position of the level meter in the hopper for an extruder plays an important role in forming a bridge or a cavity of the raw material. That is, the present invention has been reached. That is, the extrusion molding method of the thermoplastic resin material according to the present invention, the upper part of the extruder hopper, the inclined locus surface that is opened 15 degrees upward and outward from the vertical surface that defines the edge of the lower discharge port is the upper opening of the hopper. Inside the line intersecting the plane, using an extruder with a level meter equipped with a stirrer at the bottom,
The present invention is characterized by performing extrusion molding of a thermoplastic resin.

This will be described in more detail with reference to FIG. 1. The extruder hopper 1 is of a conventional type having an inverted conical shape or an inverted polygonal pyramid shape with an open upper portion, and is provided above. A powdery thermoplastic resin material 3 in which the recovered products are mixed at a predetermined ratio is supplied from the pipe 2. At the center of the bottom of the hopper 1, there is an outlet 4
Is provided and connected to the extruder 5, and the thermoplastic resin material 3 in the hopper 1 falls by its own weight and is fed into the extruder 5 by the screw 6. An inclined locus surface S opened 15 degrees upward, preferably 10 degrees upward from the vertical plane V that defines the upper edge of the hopper 1 and the edge of the discharge port 4 intersects with the upper opening surface H of the hopper (in FIG. In the area inside the line L (shown), a level gauge 7 is provided via suitable supporting means. The level meter 7 may be of any type such as a blade rotation torque detection type or a capacitance type that is generally used, but it has a stirrer at the bottom.

In the extruder hopper 1, when the thermoplastic resin material 3 is fed into the extruder 5 by the screw 6, the level of the thermoplastic resin material 3 in the hopper 1 is lowered from position a to position b. Then, the level meter 7 operates to transmit a signal to a suction device (not shown) attached to the supply pipe 2, and a predetermined amount of the thermoplastic resin material 3 is supplied into the hopper 1 through the supply pipe 2 by this operation. Then, the level of the thermoplastic resin material 3 is raised to the position a. In this case, when the mounting position of the level meter 7 is outside the line L, the variation in the load on the screw 6 increases, the thickness accuracy of the obtained T die sheet decreases, and the occurrence of fisheye increases. It is not preferable. Also,
Since the level meter 7 is provided with a stirrer at the bottom, no bridge or cavity is formed in the hopper 1.

Examples of the thermoplastic resin used in the present invention include polyvinyl chloride resin, polyvinylidene fluoride resin, polyethylene resin, polypropylene resin, polyvinyl alcohol resin, polyethylene terephthalate resin, and the like. MBS as needed
Resin, ABS resin and other modifiers, tin malate-based, tin laurate-based, tin mercaptide lead-based stabilizers, D
A plasticizer such as OP, an acrylic processing aid, a lubricant, an inorganic filler, an ultraviolet absorber, and a colorant are mixed and used.

The recovered products used in combination with these thermoplastic resin materials are both ends (ears) of the sheet generated when the product is finished in the extrusion molding of the T die sheet as described above, and usually 2 It is cut into chips of about 6 mm square. As a method of mixing the recovered product with the thermoplastic resin raw material, a generally used mixer such as a Henschel mixer is used to uniformly mix the recovered raw materials. The mixing ratio at that time is: recovered product / thermoplastic resin raw material (weight ratio) = 5
/ 95 to 30/70, particularly 10/90 to 20/80 is preferable. If it is less than 5/95, the effect of the present invention is small, and if it exceeds 30/70, a large amount of fish eyes are generated, which is not preferable.

[0012]

EXAMPLES Next, specific embodiments of the present invention will be described based on examples. PVC with an average degree of polymerization of 800: 100 parts by weight, tin malate stabilizer: 4 parts by weight, MBS resin: 10 parts by weight, DOP: 6
Parts by weight, lubricant: A powdered thermoplastic resin material consisting of 1.5 parts by weight, 85 parts by weight of a powdered thermoplastic resin material, and 15 parts by weight of an extruded and recovered product of this material are used as a raw material. Extruder with different level gauges installed from A to E. Cylinder temperature: 120 to 185 ° C, die temperature: 200 to 205 ° C, average extrusion rate: 200 kg / hour, average thickness A transparent film having a size of 120μ, a width of 1000 mm and a length of 2000 m was manufactured. In the figure, 21 is a hopper, 22 is an outlet connected to an extruder (not shown),
Reference numeral 23 is a thermoplastic resin material supply pipe, and 24 is a level meter.
At that time, the current of the screw motor, the thickness accuracy of the film, and the number of fish eyes were measured, and the results shown in Table 1 were obtained. From this, it is understood that according to the extrusion molding method of the thermoplastic resin material of the present invention, the raw materials are stably supplied, the operation is stabilized, and the quality of the film is improved.

[0013]

[Table 1]

[0014]

EFFECTS OF THE INVENTION According to the method of the present invention, in extrusion molding of a thermoplastic resin, even if a recovered material is mixed with a powdered raw material, the powdered raw material and the recovered material are separated in the hopper to cause non-uniformity. Moreover, the supply amount does not fluctuate due to the generation of bridges or tunnels even if they are not separated, and the dimensional accuracy of the product does not decrease and the fisheye does not increase to deteriorate the product quality.

[Brief description of drawings]

FIG. 1 shows an example of an extruder hopper used in an extrusion molding method of a thermoplastic resin material of the present invention, (a) is a cross-sectional explanatory view thereof, and (b) is a cross-section taken along a line I-I. It is a top view.

FIG. 2 shows details of an extruder hopper used in an example of the present invention, (a) is a cross-sectional explanatory view thereof, and (b) is a plan view thereof.

FIG. 3 is an explanatory view showing an example of an apparatus used in a conventional extrusion molding method of a thermoplastic resin material.

4A to 4D are cross-sectional explanatory views sequentially showing a process of discharging the powder material in the hopper in the apparatus shown in FIG.

[Explanation of symbols]

1 ... Extruder hopper, 3 ... Thermoplastic resin material,
4 ... Discharge port, 5 ... Extruder, 7 ... Level meter,
V: a vertical plane that defines the edge of the discharge port, S: an inclined trajectory surface that is opened upward by 15 degrees from the vertical surface V, H: an upper opening surface of the hopper, L: an inclined trajectory surface I and an upper opening surface of the hopper A line that intersects H.

Claims (1)

[Claims] 1. An upper part of an hopper for an extruder and a lower part inside a line where an inclined trajectory surface opened 15 degrees upward from a vertical plane defining an edge of a lower discharge port of the extruder intersects an upper opening surface of the hopper. Using an extruder equipped with a level meter equipped with a stirrer,
A method for extrusion-molding a thermoplastic resin material, which comprises extruding a thermoplastic resin.