JP2001162675A - Method for producing multi-layer extruded molding, direct blow molding method, and multi-layer extrusion molding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer extrusion molding method which can reduce the number of extruders, curtails the scale of an apparatus, reduces costs, and is applicable to single-layer extrusion molding. SOLUTION: An apparatus has an extruder 5 for melt-kneading at least two thermoplastic resins different in viscosity and a die 4 fitted to the tip part of the extruder 5, the die 4 has an outer mold 7 having a cylindrical inside surface, an inner mold 8 which has a cylindrical outside surface and is arranged on the same axis in the outer mold 7, and a motor 10 for rotating the outer mold 7 and the inner mold 8 relatively around the axis, by an extrusion molding apparatus 2 in which a ring-shaped channel is formed in the cross section between the inner mold 8 and the outer mold 7, the layer of the higher viscosity rein is formed in the middle in the thickness direction of the ring-shaped channel of small shear stress by the relative rotation of the outer mold 7 and the inner mold 8 by the motor 10, and the layers of the lower viscosity resin are formed inside and outside the higher viscosity resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multilayer extruded product in which a plurality of resin layers having different physical properties are formed in a laminate, and a direct blow molding method using a cylindrical parison molded by the production method. The present invention relates to a multilayer extrusion apparatus which can be suitably used for these production methods and molding methods, and particularly relates to a novel technique capable of extruding a mixed material from a single extruder and laminating in a die.

[0002]

2. Description of the Related Art For example, when a multilayer bottle is formed by a direct blow molding method, a die 20 as shown in FIG.
Is used. The die 20 is a spider head for multi-layer blow molding of two types and three layers, and is connected to two extruders 21 and 22 for supplying two types of molten resin materials.

[0003]

As described above, when a multilayer bottle is manufactured by the direct blow molding method, two or more special extruders equipped with screws for kneading the respective molding materials constituting each layer are provided. In addition, a multilayer direct blow molding machine including a multilayer extrusion head having a flow path for forming a plurality of molding materials in layers is required. However, a molding machine equipped with screws equal to the number of molding materials necessary for forming a layer is extremely expensive, and requires a large-scale device and a large installation area.
Further, with such a multilayer direct blow molding machine, a single-layer molded product cannot be molded, and the product is limited to a multilayer molded product.

Accordingly, the present invention provides a method for producing a novel multilayer resin molded product capable of supplying a mixed material to a die from a single extruder and separating the mixed material into and out of the die to obtain a laminated structure. An object is to provide a direct blow molding method. Another object of the present invention is to provide a multilayer extrusion molding apparatus which can be suitably used in the above-mentioned production method and molding method, and which can extrude a single-layer molded article when necessary.

[0005]

Means for Solving the Problems The inventors of the present invention simply mixed the molding materials constituting the respective layers of the multilayer molded article and applied shearing force to the melted blend. It was found that each material was separated inside and outside in a die at the time of extrusion molding, and was constituted in a layered form.
That is, in extrusion molding, a molten molding material is passed through an annular flow passage formed between an outer die (die) and an inner die (core) of a die, and the shape is hardened during the passage of the flow passage. However, when the molding material flows in the die, the molten resin material is cooled immediately after touching the mold wall surface and its viscosity increases,
As a result, there is always a shear condition between the flowing material immediately inside the increased viscosity material. At this time, if the molding material is composed of a mixed material having a difference in viscosity at the time of melting,
Due to this shearing phenomenon, a phenomenon occurs in which the low-viscosity material moves to the outside of the fluidized bed, and the high-viscosity material tries to move to the center (inside) of the fluidized bed. In addition to such knowledge, the present inventors cannot obtain a good multilayer structure only by the shear phenomenon that occurs in the molding material when simply extruding,
From the start of the extrusion of the molding material, a method was found in which an intense shearing force was generated by relatively rotating the outer mold and the inner mold of the die at high speed, and as a result, a laminated extruded product of the mixed material was obtained.

That is, in the method for producing a multilayer extruded product of the present invention, two or more kinds of thermoplastic resin materials having different viscosities are melt-kneaded, and when the melt-mixed resin material is extruded from a die,
The outer die and the inner die of the die are relatively rotated to form a high-viscosity resin material layer at a predetermined portion in the thickness direction of the annular flow path in the die, and a low-viscosity resin is formed inside and outside the high-viscosity resin layer. It is characterized by forming a layer of a material. In addition,
As the two or more resin materials, a combination of a plurality of thermoplastic resins having different physical properties such as gas barrier properties and chemical resistance can be selected.

[0007] As the above-mentioned two or more resin materials, a resin material having a low compatibility at a temperature near the highest melting point among these plural resin materials (ie, a combination of incompatible systems) is selected. Is preferred. On the other hand, the molten mixed resin material supplied to the annular flow path of the die is desirably a uniform blend in which two or more resin materials are uniformly mixed and melted. Different types of polymers are generally difficult to mix, but the addition of a compatibilizer, which is a polymerizable surfactant, facilitates the formation of a homogeneous blend having desired properties from two or more polymers. In particular, as the compatibilizing agent used in the present invention, those exhibiting large compatibility at a predetermined temperature or higher are preferable. According to this, at the time when the molten mixed resin material is supplied into the die, the temperature of the molten mixed resin material is set to a temperature that shows greater compatibility with the compatibilizing agent, so that the mixed material is mixed in the extruder. It is possible to supply the molten mixed resin material to the die in the state of a uniform blend by eliminating the occurrence of the separation phenomenon. Then, when the resin material is cooled in contact with the mold, it no longer exhibits compatibility, and the resin material in the annular flow path of the die can be easily multi-layered by applying a shear force to the resin material by the relative rotation of the mold. It becomes possible.

According to the manufacturing method of the present invention, a multilayer extruded product can be obtained by a single extruder and a die having a single annular flow path. It is possible to reduce the cost.

In general, when the molten mixed resin material passes through the annular flow path while rotating the outer mold and the inner mold relatively, the shear force becomes greatest near the mold contact surface, and the center of the annular flow path in the thickness direction is increased. Has the lowest shear force. Therefore, the high-viscosity resin layer is formed at the center in the thickness direction of the annular flow path.

[0010] The molded article produced by the above-mentioned production method is limited to a cylindrical article having a transverse cross section, but the type of the molded article is not limited to a specific one. For example,
A resin tube having a laminated structure, a cylindrical parison used for direct blow molding, and the like can be molded by the above-described production method. That is, the direct blow molding method of the present invention to which the above-described manufacturing method is applied is to form a pipe-shaped multilayer parison by the above-described manufacturing method of the present invention, and to insert the parison into a split mold to form a bottle bottom and the axial direction of the parison. A part of the parison is fused, air is blown into the parison, and the parison is pressed against the inner surface of the split mold by air pressure. Such a direct blow molding method can be easily implemented by those skilled in the art by applying a conventionally known technique except for a parison laminating method.

The manufacturing method of the present invention can be carried out by the following manufacturing apparatus. That is, the apparatus for producing a multilayer extruded product of the present invention includes an extruder for melting and kneading two or more kinds of thermoplastic resin materials having different viscosities, and a die attached to a tip portion of the extruder. Is an outer mold having a cylindrical inner peripheral surface, an inner mold having a cylindrical outer peripheral surface and disposed on the same axis in the outer mold, and an outer mold and an inner mold around the axis. And a rotary drive mechanism for relatively rotating the inner and outer dies, and an annular flow path is formed between the inner and outer dies in a cross section. According to such a manufacturing apparatus, a high-viscosity resin material layer is formed at a predetermined portion in a thickness direction of the annular flow path having a small shear stress by relatively rotating the outer mold and the inner mold by the rotation drive mechanism, and It is possible to form a low-viscosity resin material layer inside and outside the high-viscosity resin layer. If the rotary drive mechanism is not operated, it can be used as a single-layer extrusion die, so that a single-layer extruded product can be formed using such a manufacturing apparatus.

The rotary drive mechanism may be configured to drive one of the outer mold and the inner mold to rotate about its axis. According to this, since only one of the outer die and the inner die needs to be provided with the rotation drive mechanism, the structure of the device can be simplified, and the flow path structure in the die and the connection structure between the die and the extruder can be achieved. The degree of freedom in designing such as can be increased.

In the present invention, the molded article is preferably a synthetic resin molded article. The molded article is not limited to the final molded article, but is further subjected to molding processing such as blow molding or secondary processing such as after baking. (Such as parison). The molded article produced by the method of the present invention includes not only a three-layer molded article but also a multilayer molded article having four or more layers.

The rotary drive mechanism may be of any configuration as long as it drives the outer die and the inner die relatively to each other. For example, it drives both the outer die and the inner die. Alternatively, one of the outer mold and the inner mold may be fixed and the other may be rotationally driven. Specifically, for example,
The rotary drive mechanism may be configured to drive the outer die to rotate about its axis. Further, the rotation driving mechanism may be configured to rotationally drive the inner die around its axis.
Further, the outer mold and the inner mold may be configured to rotate relative to each other only in a part of the annular flow path in the axial direction. In this case, two or more types of molten resin materials are separated radially inward and outward in the relative rotation part. However, it is also possible to form an annular flow path for each resin material separately on the downstream side of the relative rotation portion, and to join the resin material layers when the viscosity increases to some extent.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a simplified view of a main part of a direct blow molding apparatus 1 using a multilayer parison according to an embodiment of the present invention. The direct blow molding apparatus 1 includes a multilayer extrusion molding apparatus 2 for extruding a cylindrical multilayer parison P.
And a blow mold 3 for blow molding the parison P immediately after being formed by the apparatus 2 to obtain a bottle product.

The extruder 2 comprises a crosshead die 4, a single kneading extruder 5 for supplying a molten mixed resin material (molding material) to the die 4, and a pelletized raw material supplied to the kneading extruder 5. And a hopper 6 for supplying the water. The hopper 6 is supplied with a plurality of resin materials constituting each layer of the multilayer molded product and, if necessary, with various additive materials (such as a compatibilizer). The combination of the resin materials can be variously selected according to the performance, application, and the like required for the molded article. For example, polyolefin and nylon can be used. Note that a hopper 4 may be provided for each resin material, or it may be configured to perform melt-kneading for each resin material and mix different resin materials in a molten state.

The die 4 is connected to the tip of the extruder 5 and has an outer mold 7 (die) having a cylindrical inner peripheral surface and a coaxial center inside the outer mold 7 having a cylindrical outer peripheral surface. And an inner die 8 (core) disposed thereon. An annular flow path is formed in the cross section between the outer die 7 and the inner die 8, and the molding material kneaded and melted and extruded by the screw 5 a in the extruder 5 passes through the annular flow path. Shaped and cooled in
It is extruded from the tip (lower end) of the die 4. The molding material extruded from the die 4 instantaneously changes from the pressurized state inside the extruder 5 and the die 4 to a normal pressure state, so that the molding material swells in the radial direction to form a parison having a predetermined diameter.

The inner die 8 includes a motor 10 and a transmission gear 1.
It is configured to be able to rotationally drive at high speed by a rotational drive mechanism having 1 and 12. That is, the upper side of the inner die 8 is the outer die 7
The lower side of the inner mold 8 is formed to have a smaller diameter than the upper side, and a gap between the lower side of the inner mold 8 and the outer mold 7 is formed by molding material. Channel. In addition, the inner die 8 can be rotatably supported by bearings fixed to the outer die 7. A gear 12 is integrally provided at the upper end of the inner die 8, and a gear 11 that meshes with the gear 12 is provided on an output shaft of the motor 10.

Below the die 4, the blow molding die 3 is provided. The blow mold 3 is a split mold 3
a, 3b, and a conventionally known device including a blowing nozzle (not shown) and the like, and a detailed description thereof will be omitted.

According to the direct blow molding apparatus of the above embodiment, it is possible to manufacture a blow molded article having a multilayer structure by extruding a polymer blend of a polyolefin such as polyethylene and nylon with a single extruder. . That is, the uniform blended resin material melt-mixed in the extruder 5 is supplied to the die 4 and circulated through the flow path in the die 4. At this time, the motor 10 is driven to drive the inner die 8.
When the is rotated at high speed, the high viscosity nylon moves to the center in the thickness direction of the annular flow path due to the difference in viscosity between the polyolefin and the nylon at the time of melting, and the low viscosity polyolefin moves in both directions in the thickness direction of the annular flow path. Moving outward (outer and inner peripheral sides of nylon), the mixed resin material is multilayered in the annular flow path. Then, the molding material is cooled as it reaches the downstream side of the annular flow path, and the curing of the molding material proceeds,
The multilayered parison (three-layer parison) is extruded from the tip of the die 4 in a multi-layered state.

The parison is sandwiched between the split molds 3a and 3b of the blow molding die, and a part of the parison in the axial direction to be the bottom of the bottle (the upper side of the split molds 3a and 3b in the drawing).
And air is blown into the parison, and the parison is expanded by air pressure, so that the split molds 3a, 3
By pressing against the inner surface of b and cooling and solidifying, a laminated bottle container is formed.

On the other hand, when a single-layer molded product is manufactured, the motor 10 is stopped, so that the single-layer parison can be molded by the die 4, and the single-layer molded product and the multilayer molded product can be formed. The device can be shared. Also,
It suffices to knead and melt two or more resin materials in a single extruder to obtain a multilayer structure, so that the number of extruders can be reduced, the cost of the apparatus can be reduced, and the size of the entire apparatus can be reduced. It is possible.

It should be noted that the present invention is not limited to the above-described embodiment, and the design can be appropriately changed within the scope of the present invention. For example, the die is not limited to a crosshead die, and may have a conventionally known appropriate configuration such as an offset die or a straight die. Further, the present invention is not limited as long as two or more resin materials are kneaded and melted in at least one extruder and are multi-layered in a die. Such two or more resin materials to be multi-layered are kneaded. Along with the extruder for melting, it is possible to provide a conventionally known extruder for molding material for lining.

[0025]

As described above, in the present invention, the resin material constituting each layer of the multilayer molded article is melt-mixed in advance, and the molten mixed resin material is passed through the annular flow path inside the die. By rotating the outer mold and the inner mold relative to each other, each resin material is dispersed inside and outside due to a difference in viscosity of each resin material and a difference in shear force inside the annular flow path. A molded article can be obtained. By manufacturing a multilayer resin molded product using such a novel manufacturing method and manufacturing apparatus, it is possible to simplify the apparatus configuration, reduce equipment costs, and significantly reduce product costs. In addition, the extrusion molding apparatus of the present invention can produce a remarkable effect that both a single-layer molded article and a multilayer molded article can be molded.

[Brief description of the drawings]

FIG. 1 is an overall simplified side sectional view of a direct blow molding apparatus according to an embodiment of the present invention.

FIG. 2 is a simplified side sectional view of a conventional multilayer extrusion molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Direct blow molding apparatus 2 Multi-layer extrusion molding apparatus 3 Blow molding die 4 Die 5 Extruder 7 Outer die (die) 8 Inner die (core) 10, 11, 12 Rotation drive mechanism P Parison

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 101: 12 B29K 101: 12 B29L 9:00 B29L 9:00 22:00 22:00 F term (Reference) 4F201 AG03 AG07 BA03 BC01 BC02 BC12 BD06 BK13 BM06 BM13 BR01 BS10 4F207 AG03 AG07 KA01 KB22 KF01 KK12 KL51 4F208 AG03 AG07 LA01 LA07 LB22 LD16 LG06 LG23 LJ09

Claims (5)

[Claims] 1. An extruder for melting and kneading two or more thermoplastic resin materials having different viscosities, and a die attached to a tip of the extruder, wherein the die has a cylindrical inner peripheral surface. An outer mold having an outer mold, an inner mold having a cylindrical outer peripheral surface and disposed on the same axis in the outer mold, and a rotation drive mechanism for relatively rotating the outer mold and the inner mold around the axis. An annular flow path is formed in the cross section between the inner mold and the outer mold, and the rotational drive mechanism rotates the outer mold and the inner mold relatively to each other so that the thickness direction of the annular flow path having a small shear stress is reduced. A multilayer extrusion molding apparatus capable of forming a layer of a high-viscosity resin material at a predetermined portion and forming a layer of a low-viscosity resin material inside and outside the high-viscosity resin layer. 2. The rotation drive mechanism according to claim 1, wherein one of the outer die and the inner die is driven to rotate about its axis.
2. The multilayer extrusion molding apparatus according to item 1. 3. A method of melting and kneading two or more kinds of thermoplastic resin materials having different viscosities and, when extruding the melt-mixed resin material from a die, relatively rotating an outer die and an inner die of the die to form an annular ring in the die. Manufacturing a multilayer extruded product characterized by forming a layer of a high-viscosity resin material at a predetermined portion in the thickness direction of the flow path and forming a layer of a low-viscosity resin material inside and outside the high-viscosity resin layer Method. 4. The multilayer extrusion molding according to claim 3, wherein the relative rotation between the outer mold and the inner mold is performed by rotating one of the outer mold and the inner mold about its axis. Product manufacturing method. 5. A pipe-shaped multilayer parison is formed by the production method according to claim 3 or 4, the parison is sandwiched between split molds, and a part of the parison serving as the bottom of the bottle is fused in the axial direction. A direct blow molding method characterized by blowing air into the parison, expanding the parison by air pressure, and pressing the parison against the inner surface of the split mold.