JP2589606Y2 - Extrusion foaming equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for foam-forming a resin material using an extruder.

[0002]

2. Description of the Related Art A chemical blowing agent is added to a thermoplastic resin,
Alternatively, a foaming nucleating agent such as calcium carbonate or talc is conventionally used as a means for obtaining a fine foamed molding when a physical foaming agent is supplied and extrusion foaming is performed to produce a foamed molded product. I was However, no matter how much the bubble nucleating agent is added, there is a limit to the size that can be miniaturized, and at most the bubble diameter cannot be reduced to 100 mμ or less.

[0003] The reason can be inferred as follows. In order for the foaming agent molecules dissolved in the resin to nucleate, a certain amount or more of nucleation energy is required. In other words, nucleation occurs only when a certain number or more of the blowing agent molecules aggregate. When a cell nucleating agent is added here, the nucleation energy is reduced at the interface between the resin and the cell nucleating agent, and nucleation occurs with a smaller number of blowing agent molecules, resulting in finer bubbles. However, since a certain number or more of the foaming agent molecules are aggregated at the interface between the resin and the cell nucleating agent, bubbles cannot be reduced to 100 mμ or less.

For example, Japanese Patent Application Laid-Open No. Sho 60-31538 discloses a method in which a solvent or gas is injected into an olefin resin using an extruder, and the resulting mixture is extruded and foamed. Also in this method, calcium carbonate or talc is used as a cell nucleating agent to make the cells uniform, but this is not sufficient in terms of making the cells finer, and the cell diameter of the obtained foam is 100 mμ. Was exceeded.

[0005]

As described above, in the conventional technique, a foam having a cell diameter of more than 100 μm is formed,
Although it is possible to make the size of the cells uniform, it has been difficult to produce a foam having fine cells having a cell diameter of 100 mμ or less. An object of the present invention is to solve the above problems and to provide an extrusion foaming apparatus which is effective for molding a foam having ultra-fine bubbles having a bubble diameter of 100 mμ or less.

[0006]

In order to achieve the above object, various extrusion foaming apparatuses have been studied, and based on the consideration of the nucleation energy of bubbles described above, a molten resin in which a blowing agent has been dissolved has been developed. In addition, it has been found that by applying vibration energy from the outside, nucleation can be caused even in a state where the aggregation of the foaming agent molecules is small, and as a result, a foam of ultrafine bubbles of 100 mμ or less is formed. That is, the extrusion foaming apparatus of the present invention has a die attached to the tip of the extruder, and has a loss coefficient of 1 × 10 ^-3 to 1 at the discharge port of the die.
A vibration absorbing member for vibration frequency 1K～100MHz, vibration
And a vibration generator that generates a dynamic amplitude of 0.1 to 1000 μm .

The device of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an extrusion foaming apparatus when a physical foaming agent such as carbon dioxide gas or nitrogen gas is used as a foaming agent. FIGS. 2 and 3 are side views showing a tip of a mold. FIG. 1 to 3, 1 is an extruder, 2 is a mold, 3 is a vibration generator, and 4 is a vibration absorber. The extruder 1 is provided with an injection port 13 for injecting a foaming agent. In addition, 11 is a screw and 12 is a hopper. The vibration generator 3 is attached to the tip of the mold 2 via a vibration absorbing material 4. 5 is a plunger pump, 6 is a foaming agent container, and the foaming agent is a foaming agent container 6.
From the supply port 13 to the extruder 1 through the foaming agent supply pipe 7 by the plunger pump 5.

In order to produce a foam by the above apparatus, the resin composition is supplied to the hopper 12 of the extruder 1, melted and kneaded with the screw 11, and the foaming agent is injected from the inlet 13 using the plunger pump 5. It is pressed into the resin melt in the extruder 1. The foaming agent is further kneaded with the molten resin by the screw 11, and the molten resin mixed with the foaming agent foams when being discharged from the mold 2. Is manufactured.

The vibration generator used in the present invention includes:
There are a piezoelectric vibrator, a polymer piezoelectric film, a piezoelectric ceramic vibrator, a Langevin type vibrator, a magnetostrictive vibrator, an ultra-high frequency ultrasonic generator, an electrodynamic type converter, a capacitor type converter, an electromagnetic induction type converter and the like. The frequency of the vibration generated by this vibration generating device is in the range of 1 kHz to 100 MHz, and the amplitude of the vibration depends on the frequency.
The range is 1 to 1000 μm . If the vibration frequency is too low or the amplitude is too small, sufficient nucleation energy cannot be given, and the bubbles cannot be made ultrafine. Conversely, if the frequency of the vibration is too high or the amplitude is too large, it consumes a lot of energy to give the vibration, which is not desirable.

The thickness of the vibration generator is determined by the frequency and amplitude of the generated vibration and the amount of resin extruded. For example, when the frequency is 1 MHz and the amplitude is 100 μm, it is necessary to pass through the vibration generator. Time is 0.
It must be between 1 and 10 milliseconds.

The vibration absorbing material used in the present invention converts vibration energy into heat energy or the like and dissipates the same to attenuate the vibration. The vibration generated by the vibration generator is cut off and not transmitted to the mold. Play a role. As the material, for example, a damping alloy having a very high internal friction, a damping steel plate or a Teflon plate, a hard rubber plate, an asbestos plate, a thermosetting plastic plate, a ceramic plate mainly containing alumina, and the like are preferable. . Loss coefficient of this vibration absorbing material (shows the damping rate of vibration energy)
Depends on temperature and frequency, but is in the range of 1 × 10 ^-3 to 1.
And

Although the thickness of the vibration absorbing material is determined by the frequency and amplitude of the generated vibration and the amount of resin extruded, the thickness is generally determined by an experiment because it is affected by the material. For example, when the material is a thermosetting plastic, the thickness must be set so that the frequency is 1 MHz, the amplitude is 100 μm, and the time required to pass through the vibration absorbing material is 0.1 to 1 second.

When the vibration absorbing material and the vibration generating device are attached to the mold in this order, plastic bolts, ceramic bolts, or separate fixing jigs are used so that the vibration does not propagate to the mold. For example, in FIG. 2, the vibration absorbing member 4 and the vibration generator 3 are fixed to the mold 2 with heat-resistant plastic bolts 9. FIGS. 3A and 3B show a structure in which a vibration absorbing material 4 and a vibration generating device 3 are integrated and fixed separately from a mold 2.
This is an example in which one is connected and the whole is fixed by an anchor 10.

In the extrusion foaming apparatus of the present invention, when a chemical blowing agent is used as a blowing agent, a single-screw or multi-screw extruder usually used for extrusion molding is used. Also, when using a physical foaming agent such as an organic gas, a volatile liquid, an inorganic gas, or water, an extruder equipped with a vent type screw and provided with an inlet through which the foaming agent can be pressed into the vent portion from the middle of the cylinder is used. used.

The resin extruded and foamed by the device of the present invention is:
It is not particularly limited as long as it is a thermoplastic resin, for example, polyethylene, polypropylene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-ethyl acrylate copolymer, propylene Polyolefin resins such as copolymers, ethylene-vinyl acetate copolymers, polystyrene, polyvinyl chloride, polyvinyl fluoride, polycarbonate, polyacetal, polyphenylene sulfide, polyphenylene oxide, polyetherimide, polyetheretherketone and nylon 6, nylon 6 -6, polyamide resin such as nylon 12, polyester such as polyethylene terephthalate and polybutylene terephthalate, acrylic resin, acrylonitrile-butadiene Ren-based resin, such as cellulose plastic, and the like. These may be used alone or in combination of two or more.

The foaming agent is not particularly limited as long as it does not deteriorate the above-mentioned thermoplastic resin. For example, a chemical generating gas by chemical decomposition such as azodicarbonamide or azobisisobutyronitrile can be used. Blowing agent or butane, pentane, dichlorodifluoromethane (CF
C-12), Monochlorodifluoroethane (HCFC-1
An organic gas having a boiling point lower than the melting point of the resin, such as 42b), or a volatile liquid, or an inorganic gas such as carbon dioxide, nitrogen, air, argon, or neon, or water is used.

These may be used alone or in combination of two or more. From the viewpoints of safety and environmental protection, inorganic gas and water are preferable, and among them, when it is desired to obtain a foam having a high expansion ratio, a gas having high solubility in a thermoplastic resin such as carbon dioxide gas is preferable. Further, in addition to the thermoplastic resin and the foaming agent, additives such as synthetic rubber, paraffin, plasticizer, pigment, flame retardant, and antistatic agent may be mixed.

The operating conditions for extrusion foaming with the present invention apparatus vary depending on the properties of the thermoplastic resin to be molded, but the extrusion temperature is determined by the melting point of the thermoplastic resin.
It is preferable that the temperature range is higher by about 10 ° C., and the mold temperature is in the temperature range of 5 ° C. lower than the melting point of the thermoplastic resin to 10 ° C. higher. The amount of resin discharged from the mold is 1 to 10
It can be extruded in the range of 0 kg / hour. In addition, the resin is normally extruded from the high-pressure extruder into the atmosphere, but if the extruded atmosphere is placed at a pressure lower than the atmospheric pressure, the foaming is completed instantaneously, and the bubbles become finer. .

[0019]

When the extrusion foaming apparatus of the present invention is used, the molten resin mixed with the foaming agent is subjected to vibration energy from the vibration generator at the exit of the mold of the extruder, and even when the aggregation of the foaming agent molecules is small. Nucleation occurs and a foam of fine cells is obtained. At this time, since the vibration is blocked by the vibration absorbing material and is not transmitted to the mold, there is no problem that foaming due to the vibration occurs in the mold. The diameter of the cells of the obtained foam is 0.1 to 20 μm on average, and the range is determined by the manner of applying vibration. In particular, when the average bubble diameter is 1μ
If it is desired to reduce the vibration energy to m or less, it is necessary to shorten the time of the vibration application and increase the vibration energy application.

[0020]

Next, an example in which foam molding is carried out using this apparatus will be described. The equipment used was the apparatus shown in FIG. 1 and a vent type screw (φ = 65 mm, L
/ D = 35), and the die diameter of the die was 2 mm. A Teflon plate having a thickness of 5 mm was attached as a vibration absorbing material, and a ring having a diameter of 2 mm and a thickness of 2 mm equipped with a piezoelectric ceramic vibrator was attached as a vibration generator. The resin used was low-density polyethylene (density 0.921, melt flow rate 2.0 g / 10 min, melting point 110.7 ° C.), antioxidant (Mark32, manufactured by Adeka Argus Chemical Co., Ltd.).
8) A mixture of talc (manufactured by Nippon Talc, MS), the composition of which is as shown in Table 1. Carbon dioxide gas was used as the foaming agent.

The production conditions of the foam molding are as follows: the cylinder temperature is set to 130 ° C. and 150 ° C. from the hopper side toward the tip.
℃, 130 ℃, 130 ℃, mold temperature is 105 ℃
And Carbon dioxide gas from cylinder 6 to plunger pump 5
Thus, it was press-fitted into the cylinder 1 from the injection port 4 through the pipe 7. The resin extrusion rate was 12 kg / hr.
The vibration given by the vibrator 11 is as shown in Table 1.

The obtained foam was rod-shaped, and the average cell diameter and expansion ratio were measured as evaluation items. The average cell diameter is a cross-sectional photograph of the obtained foam (100 times magnification).
And draw a 2cm wide grid on the photo, define the longest line segment as the diameter of the bubble connecting the outer circumference of one bubble parallel to the grid, and define all the bubbles in the photo. The cell diameter was measured and averaged to obtain the average cell diameter. The expansion ratio was obtained by measuring the specific gravity of the obtained foam using an electronic hydrometer (Model ED-120T, manufactured by Mirage Co.), and calculating the expansion ratio by dividing the average density of the raw resin.

[0023]

[Table 1]

As is clear from the above Examples and Comparative Examples, when no vibration is applied, the average bubble diameter is several tens times and several hundred times larger than when vibration is applied. However, the bubbles are only reduced to a size of a few hundred μm. When vibration is applied, the bubble diameter is several μm to several tens μm.
It can be seen that it is ultrafine to m. However, when no vibration absorbing material is used, the effect is remarkably inferior.

[0025]

[Effects of the Invention] When foaming is performed using the extrusion foaming apparatus of the present invention, extremely fine bubbles of 100 μm or less can be generated, and a foam of ultrafine bubbles which has been difficult to achieve conventionally. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an example of an extrusion foaming apparatus of the present invention.

FIG. 2 is a side view showing an example of a state in which a vibration absorbing material and a vibration generating device are attached to a tip of a mold.

FIG. 3 is a side view of another example of a mounted state of the vibration absorbing material and the vibration generating device.

FIG. 4 is a side view showing still another example of a mounted state of the vibration absorbing material and the vibration generating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 13 Foaming agent injection port 2 Die 3 Vibration generator 4 Vibration absorber 5 Plunger pump 6 Foaming agent container 8 Foam

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-256721 (JP, A) JP-A-56-137938 (JP, A) JP-A-6-320598 (JP, A) JP-A-3-320 213325 (JP, A) JP-A-64-75219 (JP, A) JP-A-60-31538 (JP, A) JP-A-6-320598 (JP, A) JP-A-60-105513 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 47/00-47/96

Claims (1)

(57) [Scope of request for utility model registration] 1. A die is attached to a tip of an extruder , a vibration absorbing material having a loss coefficient of 1 × 10 ⁻³ to 1 at a discharge port of the die , a vibration frequency of 1 k to 100 MHz, and a vibration amplitude of 0.1 μm. 1 to
An extrusion foaming apparatus comprising: a vibration generator that generates 1000 μm ;