JPH11138612A - Extrusion molding method of vinyl chloride-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a product excellent in quality by attaining the degree of gelling, at which the characteristics of a vinyl chloride-based resin are demonstrated at their maximum by a method wherein the vibration having a specified frequency is applied from a specified angle to a melt flowing through a resin flow passage having a specified gap. SOLUTION: A resin composition as raw materials is fed through a hopper 1 to an extruder 2 so as to be melted and kneaded. The obtained resin melt is fed from an adapter 3 to a resin flow passage 4 in a pipe forming die 15 so as to apply a vibration from a mandrel 8, which vibrates to the extruding direction at the predetermined frequency and amplitude to the resin melt flowing in the resin flow passages with the predetermined shearing viscosity. The resin melt is extruded through a resin discharge orifice 6, resulting in obtaining a resin pipe 7 having a desired dimensions. The resin flow passage 4 has the predetermined gap, while a mandrel 8 has a taper part 16 having the predetermined gradient. The vibration developed with a vibrator 11 by means of high frequency current supplied from as oscillator 12 is amplified with a cone 10 and finally transmitted to the mandrel 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extruding a vinyl chloride resin product having excellent quality such as mechanical strength.

[0002]

2. Description of the Related Art Generally, in order to produce a plastic product by extrusion molding, a thermoplastic resin composition is melt-kneaded by an extruder, extruded from a die, shaped into a desired shape, and cooled and solidified by an appropriate sizing device. Let it. At this time, the characteristics of the obtained product often depend on the kneading condition of the resin composition in the extruder. For example, a pipe made of a vinyl chloride resin has a remarkable correlation between the kneading degree of the resin and the mechanical strength of the pipe.

[0003] Usually, a vinyl chloride resin is produced by a water suspension polymerization method. Resin particles produced by this method contain polyvinyl alcohol used as a dispersant during polymerization,
It is composed of particles called grains having a particle size of 50 μm to 150 μm whose surface is covered with a skin layer mainly composed of cellulose or the like. This grain further has a particle size of 0.5 μm to 2.
It is composed of an aggregate of particles called primary particles of 0 μm.

In order to produce a tube having excellent mechanical strength by extruding a vinyl chloride resin, the resin composition is sufficiently kneaded in an extruder to disintegrate the grain particles and fuse the primary particles (hereinafter referred to as fusion). , "Gelling" and the degree of gelation as a whole
Call. ) Needs to be advanced.

[0005] Usually, gelation of a vinyl chloride resin is carried out mainly by shearing at a screw engagement portion using a twin screw extruder. However, since the vinyl chloride resin has the property of dechlorinating and decomposing due to excessive heat, when local heat such as shearing at the screw engagement portion accompanies, the resin partially becomes highly gelled before it gels. In some cases, a problem of decomposition of the polymer may occur.

Japanese Patent Publication No. 3-48842 discloses a method of improving the kneading effect by providing a cutout in a screw flight of a compression section in which a screw groove depth changes in a plasticizing kneading zone of an extruder.

[0007]

[Problems to be solved by the invention]
In the method disclosed in Japanese Patent No. 8842, the kneading effect is improved, but local shear heat generation is basically unavoidable,
It is difficult to sufficiently bring out the properties of a thermally decomposable resin such as a vinyl chloride resin.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a method for producing a product of excellent quality by achieving a gelling degree that maximizes the properties of a vinyl chloride resin. It is in.

[0009]

Means for Solving the Problems As a result of investigations to solve the above problems, the present inventors have found that when extruding a vinyl chloride resin composition, the resin flows through a resin flow path having a specific gap. By applying a vibration having a specific frequency to the melt from a specific angle, the vibration can be propagated to the inside of the melt, and as a result, the degree of gelation is improved over the entire thickness direction, and Have been found to be able to effectively bring out the characteristics of the present invention, leading to the present invention.

First, the mechanism by which vibration propagates inside the molten resin will be described. When the wall surface (or a part thereof) of the flow path through which the molten resin flows is vibrated at a specific frequency, a part of the vibration is refracted at the interface between the flow path wall surface and the molten resin and permeates the resin. The sound velocity in the metal material constituting the flow path wall surface is c ₁ , the sound velocity in the molten resin is c ₂ , the incident angle when vibration is transmitted from the flow path wall surface to the molten resin is θ _i , and the refraction angle is θ _t (θ _i and θ _t
Are the angles with respect to the normal line of the interface. However, 0 °
If <θ _i <90 °), these relationships follow Snell's law shown in equation (1). sin θ _i / sin θ _t = c ₁ / c ₂ (1) Generally, c ₁ > c ₂ , so that θ _i > θ _t . Also, assuming that the normal component of the vibration velocity and the sound pressure are continuous at the interface, when the density of the metal material is ρ ₁ and the density of the molten resin is ρ ₂ , the transmittance T _i of the vibration energy is expressed by the following equation ( It can be represented by 2). T _i = 4ρ ₁ c ₁ ρ ₂ c ₂ cos ² θ _i / (ρ ₂ c ₂ cos θ _i + ρ ₁ c ₁ cos θ _t ) ² (2) From the equations (1) and (2), the incident angle θ _i is smaller it can be seen that the transmittance T _i of the vibration increases.

On the other hand, the vibration propagating in the medium is attenuated by mechanical loss due to the viscosity of the medium, heat conduction, and the like. In particular, if the medium has a large contribution of viscosity, such as a molten resin, the degree of attenuation increases as the viscosity increases. In other words, the propagation distance of the vibration decreases as the viscosity increases. It is also known that the degree of attenuation increases as the frequency increases. The present invention has been found based on the propagation characteristics of these vibrations.

Accordingly, the present invention provides a method of extruding a vinyl chloride resin composition by applying a vibration having a frequency of 10 kHz to 50 kHz to a melt flowing in a flow path having a gap of 1 mm to 10 mm in the vibration direction and the flow of the melt. Angle between directions is 20 ° ~
A method for extruding a vinyl chloride resin, characterized in that the voltage is applied so as to fall within a range of 90 °.

In the present invention, the frequency of vibration is limited to the range of 10 kHz to 50 kHz because the larger the frequency, the larger the attenuation of the vibration, and the lower the vibration, the lower the possibility of the noise. , Preferably 15 kHz to 22 kHz.

When the angle between the direction of vibration and the flow of the melt becomes small, the transmittance of the vibration decreases as shown by the above equation (2), and the vibration does not propagate to the inside of the resin. Therefore, it is limited to the range of 20 ° to 90 °, preferably 30 ° to 90 °.

The thickness of the resin flow path that gives vibration to the melt is as follows:
If it is large, the vibration does not propagate in the entire thickness direction, resulting in a non-uniform state. If it is small, the pressure loss of the resin flow becomes too large, and the productivity must be reduced. Therefore, it is limited to the range of 1 mm to 10 mm, preferably 2 mm. ５5 mm.

On the other hand, if the shear viscosity of the melt when imparting vibration to the melt is too large, the vibration will be greatly attenuated, and will not propagate into the molten resin. , 1.0 × 10 ^{3 to} 1.0 × 10 ⁶ (poi
se) is preferable, and more preferably 1.0 × 1
0 ^{4 to} 1.0 × 10 ⁵ (poise).

If the average amplitude of the vibration applied to the resin is too small, no effect is obtained. If the average amplitude is too large, heat generation of the vibrator increases and continuous operation becomes difficult. Therefore, the average amplitude is preferably in the range of 5 μm to 50 μm, more preferably 10 μm. ３０30 μm.

The vinyl chloride resin used in the present invention comprises:
One or two of various additives such as stabilizers, lubricants, processing aids, impact modifiers, pigments, etc., including vinyl chloride resins, chlorinated vinyl chloride resins, etc. More than one species may be contained.

The die used in the present invention is not particularly limited, and any die such as a pipe molding, a sheet molding, a film molding, and a hetero-forming die can be applied.

As a method of vibrating the die or a part thereof at a specific frequency, a vibrator (electroacoustic transducer) for converting high-frequency power into mechanical vibration power is joined to a portion to be vibrated with a screw or the like, and the vibrator is vibrated. For supplying high-frequency power to the power supply. As a vibrator, a bolted Langevin type vibrator is generally used in which a piezoelectric material (barium titanate or lead zirconate titanate), which generates a displacement or a force when a voltage is applied thereto, and a metal are tightened with a bolt and integrated. It is preferably used. The high-frequency power supply that drives the vibrator includes an oscillation circuit,
An oscillator composed of a voltage amplifier, a power amplifier, an impedance matching circuit and the like is usually used.

The vibrating part of the die needs to be designed to resonate at a specific frequency. If the resonance condition is not satisfied, it is difficult in principle to vibrate the metal body at a frequency of 10 kHz or more.

The extruder used in the present invention is a screw extruder generally used in plastic molding, and is not particularly limited, but is a single screw extruder, a twin screw extruder, or the like. A multi-screw extruder equipped with three or more screws is mentioned, and any of them is suitably used. Among them, a biaxially different-direction rotary screw extruder having an excellent kneading effect is more preferably used.

In the present invention, when cooling and shaping the resin, a shaping device such as a forming die and a cooling water tank may be provided as necessary.

According to the present invention, when extruding a vinyl chloride resin composition, a vibration having a frequency of 10 kHz to 50 kHz is applied to the melt flowing through the flow path having a thickness of 1 mm to 10 mm in the vibration direction and the flow of the melt. Angle between directions is 20 ° -9
By applying the vibration so as to be in the range of 0 °, the vibration propagates to the inside of the melt, the degree of gelation is improved in the entire thickness direction of the molded body, and the characteristics of the resin can be effectively extracted. .

[0025]

FIG. 1 is a schematic diagram showing an example of a resin pipe manufacturing apparatus used in one embodiment of the present invention.
FIG. 2 is an enlarged view of the vicinity of the resin flow path 4 in FIG. In FIG. 1, a resin composition as a raw material is supplied to an extruder 2 via a hopper 1, where it is melt-kneaded. Extruder 2
Is a two-axis counter-rotating screw extruder in which two screws 19 having a plurality of screw flights 13 rotate in different directions. The resin melt obtained here is sent from the adapter 3 to the resin flow path 4 in the pipe molding die 15 and flows through the resin flow path 4 at a predetermined frequency and amplitude into a resin melt flowing at a predetermined shear viscosity. Vibration is applied from the mandrel 8 which vibrates in the extrusion direction. The resin melt is then extruded from a resin discharge port 6 to obtain a resin tube 7 having a desired size.

As shown in FIG. 2, the resin flow path 4 has a predetermined gap d, and the mandrel 8 has a tapered portion 16 having a predetermined gradient α. The mandrel 8 is vibrated by the vibrator 11 through the cone 10 in the pushing direction. That is, the oscillator 12 (frequency 20 kHz, maximum output 3.6 k
The vibration generated in the vibrator 11 by the high-frequency current supplied from W) is widened by the cone 10 and transmitted to the mandrel 8. A flange 18 is provided at a node portion of the cone 10 and supports the vibrator by being connected to the cavity 5 of the die 15. Also, on the outer periphery of the mandrel 8,
An auxiliary mandrel 9 having a manifold 17 is attached to the outer surface, so that the distribution of the residence time of the molten resin in the die 15 is made uniform.

FIG. 3 is a schematic configuration diagram showing an example of a resin sheet manufacturing apparatus used in another embodiment of the present invention, and FIG. 4 is an enlarged view near the resin flow path 4 in FIG. In FIG. 3, an extruder 2 is the same as that in FIG. 1, and a resin melt obtained here is transferred from an adapter 3 to a resin flow path 4 having a predetermined gap d in a sheet forming die 20. Vibration is applied from a horn 21 that vibrates at a predetermined frequency and amplitude to the resin melt that is sent and flows through the resin flow path 4 at a predetermined shear viscosity. The resin melt is then extruded from the resin discharge port 6 and a resin sheet 22 having a desired size is formed.
Is obtained.

The horn 21 is driven by the vibrator 11 to make the cone 10
The flange 18 provided at the node of the cone 10 and the cavity 5 of the die 20 are connected so that the vibration direction of the horn 21 and the flow direction of the molten resin are 90 °.

[0029]

The present invention will be described in more detail with reference to the following examples.

(Example 1) [Blend of raw materials] 100 parts of vinyl chloride resin (degree of polymerization: 1000) Organotin stabilizer 1.5 parts Calcium stearate 1 part Stearic acid 1 part Polyethylene wax 0.5 part As shown in FIG. Using the apparatus, the above raw material mixture is supplied from the hopper 1, and the barrel temperature is 175 ° C, 190 ° C,
Extruder set at 190 ° C. (φ = 50 mm, L / D =
30) In 2, the resin composition was melt-kneaded. The melt is sent from the adapter 3 to the resin flow path 4 having a thickness of 3 mm.
Vibration was applied to the melt from a mandrel 8 vibrating in the extrusion direction at 0 kHz and a maximum amplitude of 30 μm. Next, the resin was extruded from the resin discharge port 6 at a discharge rate of 100 kg / h,
A vinyl chloride resin tube 7 having a diameter of 2 mm and an inner diameter of 25 mm was obtained.

The gradient of the tapered portion 16 of the mandrel 8 used in this embodiment is 45 °, and the average amplitude of the tapered portion 16 in the extrusion direction is 20 μm. The shear viscosity of the molten resin in the resin flow path 4 is 3.0 × 10 ⁴
Poise.

The obtained resin pipe was measured for Charpy impact strength using a Charpy impact tester in accordance with JIS K 7111. Table 1 shows the results.

(Example 2) [Raw material blend] 100 parts of vinyl chloride resin (degree of polymerization: 1000) Organotin stabilizer 1.5 parts Calcium stearate 1 part Stearic acid 1 part Polyethylene wax 0.5 part As shown in FIG. Using the apparatus, the above raw material mixture is supplied from the hopper 1, and the barrel temperature is 175 ° C, 190 ° C,
Extruder set at 190 ° C. (φ = 50 mm, L / D =
30) In 2, the resin composition was melt-kneaded. The melt is sent from the adapter 3 to the resin flow path 4 having a thickness of 2 mm,
Vibration was applied to the melt from a horn 21 having a frequency of 0 kHz and a maximum amplitude of 30 μm and vibrating in a direction perpendicular to the flow direction of the melt. Subsequently, it was extruded from the resin discharge port 6 at a discharge rate of 100 kg / h to obtain a vinyl chloride resin sheet 22 having a thickness of 4 mm and a width of 300 mm.

The shear viscosity of the molten resin in the resin flow path 4 is 3.0 × 10 ⁴ poise. The Charpy impact strength of the obtained resin sheet was measured. Table 1 shows the results.

(Comparative Example 1) The thickness of the resin flow path 4 is 15 mm
The procedure was performed in the same manner as in Example 1 except that
A vinyl chloride resin tube 7 having a diameter of 2 mm and an inner diameter of 25 mm was obtained. About the obtained pipe | tube, the same measurement as Example 1 was performed.
Table 1 shows the results.

Comparative Example 2 The procedure was the same as in Example 1 except that the mandrel had a tapered portion having a gradient of 5 ° as shown in FIG.
A 5 mm vinyl chloride resin tube 7 was obtained. About the obtained pipe | tube, the same measurement as Example 1 was performed. Table 1 shows the results.
Shown in

(Comparative Example 3) The same procedure as in Example 1 was carried out except that the frequency was set to 60 kHz.
A vinyl chloride resin tube 7 having an inner diameter of 25 mm was obtained. About the obtained pipe | tube, the same measurement as Example 1 was performed. Table 1 shows the results.

(Comparative Example 4) The same procedure as in Example 1 was carried out except that the mandrel 8 was not vibrated.
Thus, a vinyl chloride resin tube 7 having an inner diameter of 25 mm and an inner diameter of 25 mm was obtained. About the obtained pipe | tube, the same measurement as Example 1 was performed. Table 1 shows the results.

(Comparative Example 5) The same procedure as in Example 2 was carried out except that the horn 21 was not vibrated, and the thickness was 4 m.
m, a vinyl chloride resin sheet 22 having a width of 300 mm was obtained.
About the obtained resin sheet, the same measurement as Example 2 was performed. Table 1 shows the results.

Comparative Example 6 As shown in FIGS. 5 and 6,
The procedure was basically the same as that of Example 1 except that the notch 14 was provided in the screw flight 13 of the plasticizing kneading zone of the screw 19 of the extruder 2 and that the mandrel 8 was not vibrated. However, since the load of the extruder 2 exceeded the limit value, the discharge rate was reduced to 70 kg / h, and the extruder 2 was used.
I got About the obtained pipe | tube, the same measurement as Example 1 was performed. Table 1 shows the results.

[0041]

[Table 1]

[0042]

As described above, according to the present invention, when a vinyl chloride resin composition is extruded, the thickness is from 1 mm to 1 mm.
The frequency of 10 kHz is applied to the melt flowing through the 10 mm flow path.
By applying a vibration of ~ 50 kHz so that the angle between the vibration direction and the flow direction of the melt is in the range of 20 ° to 90 °, the vibration propagates to the inside of the melt and the thickness direction of the molded body The degree of gelation is improved as a whole, and the properties of the resin can be effectively brought out.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of a resin pipe manufacturing apparatus used in an embodiment of the present invention.

FIG. 2 is an enlarged view of the vicinity of a resin flow path 4 in FIG.

FIG. 3 is a schematic configuration diagram illustrating an example of a resin sheet manufacturing apparatus used in another embodiment of the present invention.

FIG. 4 is an enlarged view of the vicinity of a resin flow path 4 in FIG.

FIG. 5 is a schematic view showing an example of a plasticizing kneading zone of a conventional extruder.

FIG. 6 is a sectional view of the screw shown in FIG. 5;

[Explanation of symbols]

 1: Hopper 2: Extruder 3: Adapter 4: Die resin flow path 5: Die cavity 6: Resin discharge port 7: Resin tube 8: Mandrel 9: Auxiliary mandrel 10: Cone 11: Vibrator 12: Oscillator 13: Screw flight 14: Notch 15: Die 16: Taper 17: Manifold 18: Flange 19: Screw 20: Die 21: Horn 22: Resin sheet

Claims (1)

[Claims] 1. When extruding a vinyl chloride resin,
A gap having a frequency of 10 kHz to 50 kHz is applied to a melt flowing in a flow path having a gap of 1 mm to 10 mm so that an angle between the vibration direction and the melt is in a range of 20 ° to 90 °. Extrusion molding method for vinyl chloride resin.