JP2000296545A - Method for continuously manufacturing oriented tubular material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously manufacturing a thermoplastic resin molding by which it is possible to perform orientation control, molding of a thick walled product and rapid molding process and mold a high-viscosity resin continuously under a low extrusion pressure and further orient the resin at a high magnification. SOLUTION: A diameter expanding core part 34 is provided on a mandrel 3 which is inserted into a die body 2 and forms a tubular molding passage between the mandrel 3 and the die body 2. At the same time, a raw material resin supplied into the molding passage is crosslinked in the die 1 and the obtained crosslinked resin tubular material is processed in a molten state using the diameter expanding core 34 so that the material diameter is expanded and the material is thin-walled to be set by cooling. In this continuous manufacturing method, the diameter expanding part 34 is of a circular truncated cone shape having an angle formed by a generant on the side face of a circular truncated cone and the rotary center axis thereof being 10-30 deg. or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for continuously producing an oriented tubular body.

[0002]

2. Description of the Related Art A method for producing a thermoplastic resin molded article in which a resin is stretched during molding for the purpose of increasing strength has been proposed.
JP-B-4-55379, JP-T-5-5019
No. 93, Japanese Patent Publication No. 2-58093 and the like. However, the manufacturing methods disclosed in the above publications have the following problems.

[0003] In the manufacturing method of Japanese Patent Publication No. 4-55379, stretching is performed by pulling out from the downstream side of the die, and the diameter of the expanded core of the mandrel is increased. Since the orientation in the circumferential direction imparted by expanding the diameter of the raw material tube in the portion is alleviated by the drawing force in the axial direction, the orientation is preferentially oriented in the axial direction, and the arbitrariness of the orientation control is poor.

[Production method of Japanese Patent Publication No. 5-501993] The orientation state of a molded article is an orientation imparted only in the circumferential direction. There is low productivity.

[Production method disclosed in Japanese Patent Publication No. 2-58093] This is a method in which the material is pushed into the enlarged-diameter portion by the extrusion pressure, and since there is no need for a drawing force, the orientation control is arbitrarily high, and the control is easy and the production is easy. It has excellent properties. However, in the case of this production method, the film is stretched at a temperature equal to or higher than the glass transition temperature and equal to or lower than the melting point. In particular, in the case of a crystalline thermoplastic resin, a change in elastic modulus in this temperature region is sharp.

Therefore, in order to achieve uniform stretching, it is necessary to make the resin temperature distribution uniform, but it is not possible to achieve uniform temperature in thick products or high-speed molding. That is, there is a problem in the moldability of thick-walled products and high-speed molding.
In addition, since the elastic modulus is also at a high level in this temperature range, the necessary extrusion pressure is high, and it is impossible to continuously achieve high-viscosity resin or high-magnification stretching with an extruder.

Therefore, the inventors of the present invention knead the raw resin and the thermal crosslinking agent in an extruder, and supply the kneaded product from the extruder to a die having a thermal crosslinking zone, a stretching zone, and a cooling zone. A cross-linking step of thermally cross-linking the raw resin in the kneaded product extruded from the extruder in the heat cross-linking zone; While orienting,
A method for continuously manufacturing a resin molded article comprising a stretching step of shaping the molded article into a shape and a cooling step of cooling the shaped article shaped in the stretching zone to a temperature equal to or lower than the orientation relaxation temperature in a cooling zone has been proposed. ing.

That is, according to this manufacturing method, since the stretching is performed in the molten state, the resin deformation force can be greatly reduced. Moreover, since the thermoplastic resin is cross-linked to form a stitch structure between the molecular chains, the molecular orientation can be ensured by stretching even during melting. Therefore, it is possible to perform orientation control, and to mold a thick product or high-speed molding, and to continuously perform molding using a high-viscosity resin or stretching at a high magnification.

However, when an oriented tubular body is to be produced using this continuous production method, the extrusion pressure may be too high depending on the shape of the die, and the oriented tubular body may not be produced properly.

[0010]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention is capable of controlling orientation, forming a thick-walled product and high-speed forming, and having a high extrusion viscosity at a low extrusion pressure. It is an object of the present invention to provide a method for continuously producing a thermoplastic resin molded article capable of performing molding using a resin or stretching at a high magnification.

[0011]

In order to achieve such an object, a method for continuously producing an oriented tubular body according to the first aspect of the present invention (hereinafter referred to as the "method for producing the first aspect").
Is inserted into the die body and the die body,
A mandrel that forms a tubular molding passage between the die body and the die body, the die body having a diameter-enlarging tube portion that expands in diameter toward the outlet side of the molding passage, and the mandrel is enlarged in diameter of the die body. A portion having a truncated cone-shaped enlarged core portion at a portion corresponding to the cylindrical portion, and a forming passage is formed by the enlarged cylindrical portion and the enlarged core portion, and the diameter gradually increases from an inlet side to an outlet side. In the die having a zone, the raw material resin is continuously supplied from the inlet of the molding passage, and after the raw material resin is cross-linked in the die, the cross-linked resin is expanded in the stretching zone while the wall thickness is increased. A method for continuously producing an oriented tubular body comprising a step of stretching while reducing the diameter, wherein the diameter-enlarged core portion has an angle formed by a generatrix on a side surface of a truncated cone and a rotation center axis thereof at least 10 °.
It was configured to be 0 ° or less.

According to a second aspect of the present invention, there is provided a continuous production method of an oriented tubular body (hereinafter referred to as “a second production method”). A cooling zone is provided behind the stretching zone, the raw resin and the thermal crosslinking agent are kneaded in the extruder, and in this kneaded state, the raw resin is extruded from the extruder into the molding passage, and the raw resin is fed before the stretching zone. After being thermally crosslinked, in the stretching zone, the resin is stretched and shaped into a molded product while being oriented in at least one axis or more at a temperature equal to or higher than the melting point of the resin, and the stretched shaped article is oriented in the cooling zone. It was cooled below the relaxation temperature.

According to a third aspect of the present invention, there is provided a method for continuously producing an oriented tubular body according to the third aspect of the present invention. A lubricant is interposed between the wall surface of the molding passage and the resin.

In the present invention, the angle (hereinafter, referred to as "half apex angle") between the generatrix of the side surface of the truncated cone of the enlarged diameter core portion and the rotation center axis is limited to 10 ° or more and 30 ° or less. ,
Preferably it is 15 ° or more and 20 ° or less.

The reason why the half apex angle is limited as described above is as follows.
It is as follows. That is, when the half apex angle is less than 10 °, the stretching zone becomes long, so that the weight of the mandrel itself is inevitably increased and the mandrel is bent, resulting in poor dimensional accuracy of the obtained oriented tubular body. In addition, the length of the molding passage is increased and the resistance applied to the resin increases,
Extrusion pressure also increases. on the other hand. When the half apex angle exceeds 30 °, the extrusion pressure becomes too high, so that the drawing cannot be performed properly. Further, the range where the half apex angle is 15 ° or more and 20 ° or less is the best balance between the dimensional accuracy resulting from the bending of the mandrel and the reduction of the extrusion pressure.

The raw material resin used in the present invention is not particularly limited.
Examples thereof include polystyrene, polyvinyl chloride, polymethyl methacrylate, polycarbonate, and polyester. These may be used alone or in combination, and it is particularly preferable to use a crystalline thermoplastic resin. As crystalline thermoplastic resins, L-LDPE (linear low density polyethylene), LDPE (low density polyethylene), MDPE
Examples include polyethylene such as (medium density polyethylene) and HDPE (high density polyethylene), and polypropylene such as random PP (polypropylene), homo PP (polypropylene), and block PP (polypropylene).

In the continuous production method of the present invention, the method of cross-linking the raw material resin is not particularly limited. For example, general-purpose means such as electron beam, ultraviolet ray, hot water cross-linking and heat cross-linking may be used. However, in the case of thick-walled products, in the case of electron beams or ultraviolet rays, the transmission capability of the radiation source is low, and in the case of hot water crosslinking, the penetration rate of hot water is low. Thermal crosslinking is most effective. The thermal crosslinking agent used for thermal crosslinking is not particularly limited, but an organic peroxide can be used, and can be appropriately selected from the viewpoint of the molding temperature and compatibility of the thermoplastic resin to be used. In
Dicumyl peroxide, di-t-butyl peroxide, methyl ethyl ketone peroxide and the like can be mentioned.

The degree of crosslinking of the crosslinked resin is 5% or more and 50% or more.
% Or less is preferable. That is, when the degree of cross-linking is less than 5%, the molecular chains slip through by stretching at a temperature higher than the melting point, and the
If it exceeds 0%, the elongation of the resin is reduced, so that high-magnification stretching may not be performed. In the present invention, the degree of crosslinking can be represented by a gel fraction (%) represented by the following formula.

[0019]

(Equation 1)

In the above formula, the weight of the sample after the solvent extraction means that the uncrosslinked resin remaining in the sample is dissolved using a solvent capable of dissolving the selected uncrosslinked thermoplastic resin. , The weight of only the remaining insoluble matter.

As a method of supplying the resin into the die, there is a method of supplying the resin by pressure using a pressure pump capable of continuously applying heat to the resin. As such a pressure pump,
A method using an extruder as in the production method of claim 2 is the most efficient and preferable.

As the extruder, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, and the like can be used. When kneading, melt the thermoplastic resin among these,
A twin-screw co-rotating extruder excellent in mixing ability with a thermal crosslinking agent is preferable.

In the production method of the present invention, the term "below the orientation relaxation temperature" means, in the case of an amorphous thermoplastic resin, a temperature below the glass transition temperature, and in the case of a crystalline thermoplastic resin, it means a temperature below the crystallization start temperature. I do. That is, the cooling is performed to cool the stretched shaped article and freeze the orientation.

In the production method of the present invention, it is preferable that the wall surface of the molding passage, that is, the resin contact surface of the die has lubricity so that the drawing can be performed more smoothly. The method of imparting lubricity to the wall surface of the molding passage is not particularly limited, but it is preferable to interpose a lubricant between the wall surface of the molding passage and the resin as in the manufacturing method of claim 3.

The method of interposing the lubricant is not particularly limited, and includes, for example, (1) a method in which a low-molecular-weight lubricant is previously mixed into a thermoplastic resin, and (2) a method in which a lubricant is applied to the resin contact surface of the die. There is a method of supplying the agent,
The method (2) is more preferable from the viewpoint of the stability of the lubricating effect and the long-term performance of the molded article.

Examples of the lubricant used in the method (1) include waxes and oligomers. As the lubricant used in the method (2), ethylene oligomer,
Silicone oil, stearic acid, polyethylene glycol, liquid paraffin, low melting point polymer and the like,
Polyethylene glycol is more preferred from the viewpoint of the stability of forming a lubricating film and the heat resistance of the lubricant.

As a method of supplying the lubricant to the wall of the molding passage, at least a portion to be a wall of the molding passage of the die is formed of a porous material, and pressure is applied to the lubricant from the back side of the porous material. A method of oozing out toward the surface side of the wall of the molding passage, a method of developing a lubricant with a manifold and supplying the lubricant to the shape of a molded product are exemplified. The device for supplying the lubricant is not particularly limited as long as the lubricant can be supplied against the pressure in the die, and examples thereof include a plunger pump and a diaphragm pump.

In the production method of the present invention, uniaxial stretching can be achieved by one or more actions by expanding the inner diameter and reducing the thickness. The stretching ratio can be arbitrarily controlled depending on the magnitude of these actions, and is selected from the range of 5 times or more and 50 times or less in the area reduction rate at which the stretching effect is exhibited.

Additives such as an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a flame retardant, an antistatic agent and the like may be appropriately added to the raw material resin of the present invention in order to obtain desired physical properties. I do not care. It is also possible to add a small amount of a substance that can serve as a crystal nucleating agent to make the crystals finer and to help uniform the physical properties. In addition, fillers and pigments can be used in a range that does not cause deterioration in physical properties. For example,
Examples thereof include fibrous fillers such as glass fiber, carbon fiber, and asbestos, curk, mica, montmorillonite, and aluminum oxide.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described in detail with reference to the drawings. FIG. 1 shows a die of the present invention used in the method for continuously producing an oriented tubular body of the present invention.

As shown in FIG. 1, the die 1 includes a die body 2 and a mandrel 3. The die body 2
A resin supply port 21 for supplying a molten resin extruded from an extruder (not shown) and a lubricant supply port 22 are provided. The small-diameter cylindrical portion 23 extends from the end on the resin supply port 21 side toward the center.
And a large-diameter cylindrical portion 24 is provided from the exit side of the die main body 2 toward the center, and a small-diameter cylindrical portion 23 is provided.
Between the small-diameter cylindrical portion 23 and the large-diameter cylindrical portion 24
There is provided a diameter-enlarging tubular portion 25 that gradually increases in diameter toward.

The mandrel 3 is a small-diameter cylindrical portion 2 of the die body 2.
A small-diameter cylinder; a fitting part 31 which is fitted over the substantially central part of the small-diameter cylindrical part 23 from an end of the small-diameter cylindrical part 23 to fit tightly into the small-diameter cylindrical part 23 to make the die body 2 and the mandrel 3 integrated. The cross-sectional shape of the tube to be substantially formed between the small-diameter core portion 32 forming the small-diameter thick-walled tubular thermal crosslinking zone 4 with the rest of the portion 23 and the large-diameter cylindrical portion 24 of the die body 2 2, a large-diameter core portion 33 forming a cooling zone 5 having the same cross-sectional shape as that of the large-diameter core portion 33, and a stretching zone between the small-diameter core portion 32 and the large-diameter core portion 33. And an enlarged core portion 34 that forms

The enlarged diameter core portion 34 has a truncated conical shape, and is formed with a half apex angle α of 10 ° or more and 30 ° or less. The fitting portion 31 has a spiral groove 31 a that guides the resin supplied from the resin supply port 21 to the thermal cross-linking zone 4 on the outer peripheral surface of the portion from the part facing the resin supply port 21 to the boundary with the small-diameter core part 32. Has been drilled.

The mandrel 3 is provided with a lubricant supply passage 37 extending from the fitting portion 31 toward the small-diameter core portion 32. It communicates with a lubricant supply groove 36 provided spirally over the outer peripheral surface of the core portion 34.

That is, the lubricant supply passage 3 is formed by a pressurizing pump or the like.
The lubricant supplied to 5 is supplied to the outer peripheral surfaces of the small-diameter core portion 32 and the large-diameter core portion 35 which are resin contact surfaces via the lubricant supply groove 36. In FIG. 1, L
Is a generating line, and C is a rotation center axis.

The continuous production method of the oriented tubular body of the present invention using the die 1 will be described below in the order of steps. The raw material resin and the thermal crosslinking agent are mixed and kneaded by an extruder (not shown), and the obtained mixture is continuously supplied to the resin supply port 21 from the tip of the extruder.

The mixture supplied to the resin supply port 21 is sent to the thermal crosslinking zone 4 via the spiral groove 31a and is developed into a thick-walled cylinder, and the raw resin in the mixture is reduced by 5% to 50% by the thermal crosslinking agent. Thermal crosslinking is performed so as to have the following degree of crosslinking. The thermally cross-linked tubular cross-linked resin is sent to the drawing zone 6 and expanded by the taper of the diameter-enlarged core portion 34, and the thickness is reduced to achieve uniaxial or more drawing.

The tubular shaped material shaped into a gap between the large-diameter core portion 33 and the large-diameter cylindrical portion 24 by stretching in the stretching zone 6 is cooled in the cooling zone 5 to an orientation relaxation temperature or lower, that is, crystallization. While maintaining the shape below the starting temperature, cooling is performed to continuously obtain an oriented tubular body. In manufacturing the oriented tubular body as described above, the resin is always exuded through the lubricant supply port 22 and the lubricant supply path 37 to the inner peripheral surface of the die body 2 and the outer peripheral surface of the mandrel 3 which are the resin contact surfaces. Thus, the frictional resistance is reduced by interposing the crosslinked resin and the stretched resin between the inner peripheral surface of the die body 2 and the outer peripheral surface of the mandrel 3 which are the resin contact surfaces.

According to this continuous production method, the raw resin is first cross-linked to form a stitch structure between molecular chains, and the film is stretched in a molten state. As a result, the resin deformation force can be greatly reduced.

Furthermore, since thermal crosslinking is performed so as to have a degree of crosslinking of 5% or more and 50% or less, slippage of molecular chains does not occur and the orientation is excellent. Moreover, die 1
Indicates that the half apex angle α of the expanded core portion 34 of the mandrel 3 is 1
Since the angle is between 0 ° and 30 °, the extrusion pressure can be kept low. That is, the load on the extruder or the like can be reduced, and the manufacturing cost can be reduced.

[0041]

Embodiments of the present invention will be described below in more detail.

(Example 1) A die having a chrome-plated resin contact surface and an extruder as shown in FIG. 1 were prepared. [Die size]-Outer diameter of small-diameter core part 32: 20 mm-Inner diameter of small-diameter cylinder part 23: 70 mm-Outer diameter of large-diameter core part 33: 123 mm-Inner diameter of large-diameter cylinder part 24: 132 mm-Half vertex angle α: 15 °

[Extruder] TEX30α manufactured by Japan Steel Works, L / D = 51, caliber 3
2mm

Then, high density polyethylene (density 0.953, melt flow rate (MFR))
0.03, weight average molecular weight 268,000, melting point 132
° C) into an extruder, and from the position of L / D = 35, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 (Perhexin 25B manufactured by NOF Corporation) as a thermal crosslinking agent , 194 ° C, half-life time of 60 seconds).
5 parts by weight, and the high-density polyethylene and 2,5-dimethyl-2,5-
After mixing and kneading with di (t-butylperoxy) hexyne-3, the obtained mixture is fed from the resin supply port 21 of the die body 2 to 220 ° C. in the thermal crosslinking zone 4 and 1 ° in the stretching zone 6.
It was continuously fed into the die 1 set at 50 ° C. and the cooling zone 5 at 80 ° C. to continuously obtain an oriented polyethylene tube having an outer diameter of 132 mm and an inner diameter of 123 mm. At this time, the extrusion pressure of the high-density polyethylene was 50 kgf / cm ² .

Example 2 An oriented polyethylene pipe was continuously obtained in the same manner as in Example 1 except that a mandrel having a half apex angle of 25 ° was used. At this time, the extrusion pressure of the high-density polyethylene was 52 kgf / cm ² .

Comparative Example 1 An oriented polyethylene tube was continuously obtained in the same manner as in Example 1 except that a mandrel having a half apex angle of 5 ° was used. At this time, the extrusion pressure of the high-density polyethylene was 150 kgf / cm ² .

(Comparative Example 2) Extrusion was performed under the same conditions as in Example 1 except that a mandrel having a half apex angle of 35 ° was used.
At this time, the extrusion pressure of the high-density polyethylene was too high to be extrudable.

From Examples 1 and 2 and Comparative Examples 1 and 2, it can be seen that if the half apex angle is within the range of 10 ° to 30 °, the extrusion pressure can be kept low.

[0049]

As described above, the method for continuously producing an oriented tubular body according to the present invention is capable of controlling the orientation, forming a thick-walled product and performing high-speed molding.
Continuous molding using a high-viscosity resin and stretching at a high magnification can be performed uniformly. That is, a high-strength molded product can be stably manufactured by continuously controlling the orientation arbitrarily. Moreover, the die of the present invention has a half apex angle α of the expanded core portion.
Is set to 10 ° or more and 30 ° or less, the extrusion pressure can be kept low. That is, the oriented tubular body can be continuously manufactured with higher accuracy, the load applied to the extruder and the like can be reduced, and the maintenance cost and manufacturing cost such as miniaturization of the extruder can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a die used in a method for continuously manufacturing a thermoplastic resin molded product according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Die main body 25 Large diameter cylinder part 3 Mandrel 34 Large diameter core part 4 Thermal bridge zone 5 Stretching zone 6 Cooling zone

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) B29L 23:00 (72) Inventor Koichiro Iwasa 2-2 Sekisui Chemicals (72) Inventor Naoki Ueda 2-2 Sekisui Chemical Co., Ltd. F-term (reference) 4F207 AA05 AB03 AG08 KA01 KA17 KF02 KK01 KK45 KK52 KL57 KL74 KL83 KL88

Claims (3)

[Claims] 1. A die body, inserted into the die body,
A mandrel that forms a tubular molding passage between the die body and the die body, the die body having a diameter-enlarging tube portion that expands in diameter toward the outlet side of the molding passage, and the mandrel is enlarged in diameter of the die body. A portion having a truncated cone-shaped enlarged core portion at a portion corresponding to the cylindrical portion, and a forming passage is formed by the enlarged cylindrical portion and the enlarged core portion, and the diameter gradually increases from an inlet side to an outlet side. In the die having a zone, the raw material resin is continuously supplied from the inlet of the molding passage, and after the raw material resin is cross-linked in the die, the cross-linked resin is expanded in the stretching zone while the wall thickness is increased. A method for continuously producing an oriented tubular body comprising a step of stretching while reducing the diameter, wherein the diameter-enlarged core portion has an angle formed by a generatrix on a side surface of a truncated cone and a rotation center axis thereof at least 10 °.
A method for continuously producing an oriented tubular body, which is at most 0 °. 2. A cooling zone is provided behind the stretching zone of the molding passage, and the raw resin and the thermal crosslinking agent are kneaded in the extruder. In this kneaded state, the raw resin is continuously fed from the extruder into the molding passage. The raw material resin is supplied and thermally crosslinked before the stretching zone.
2. The oriented tubular body according to claim 1, wherein the oriented tubular body is stretched into a shape of a molded article while being oriented in an orientation direction equal to or more than the axis, and the stretched shaped article is cooled to an orientation relaxation temperature or lower in a cooling zone. Production method. 3. The continuous production method of an oriented tubular body according to claim 1, wherein a lubricant is interposed between the wall surface of the molding passage and the resin.