JP7271384B2 - Method for producing expanded polycarbonate resin particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing expanded polycarbonate resin particles.

Conventionally, foamed resin particles (expanded resin particles) have been used for various purposes.
Such expanded resin particles are not only used as a filler for cushions and the like as they are, but also used as a raw material for foamed beads.
This type of foamed resin particles is not only insufficient in strength if it contains a large number of coarse cells, but also does not have good secondary foamability when producing a bead-expanded molded product. It is required to be in a foamed state.

By the way, in Patent Document 1 below, resin particles composed of a resin composition containing a polycarbonate resin are contained in a pressure vessel, and the resin particles are impregnated with a foaming agent under high pressure in the pressure vessel to produce expandable resin particles. is obtained, and the expandable resin particles are expanded to produce expanded resin particles (pre-expanded particles) as a raw material for bead expanded molded articles.

JP-A-06-100724

The method using a pressure vessel as described in Patent Document 1 is a method that is sufficiently efficient in producing polycarbonate resin expanded beads because the process of impregnating resin particles with a foaming agent is a batch process. Hard to say.
On the other hand, a method using an extruder is considered to be capable of continuous production, but a method using an extruder to obtain foamed polycarbonate resin particles in a favorable foaming state has not been sufficiently established.
Accordingly, an object of the present invention is to provide a method for producing expanded polycarbonate resin particles suitable for obtaining a polycarbonate resin in a favorable foamed state.

In order to solve the above problems, the present invention
Using an extruder equipped with a granulation die with a die hole,
Melt-kneading a polycarbonate resin composition containing a polycarbonate resin together with a foaming agent in the extruder,
The kneaded product obtained by the melt-kneading is extruded from the die hole of the granulation die to foam,
cutting the extruded kneaded material at the outlet of the die hole to produce a granular material;
Water-cooling the granules to produce polycarbonate resin expanded particles,
Provided is a method for producing expanded polycarbonate resin beads, wherein a polycarbonate resin satisfying the following formula (1) is used as the polycarbonate resin.

1.6≦[η ^* _(0.01) /η ^* _(0.1) ]≦10 (1)

Here, [η ^* _(0.01) ] in formula (1) represents the complex viscosity measured at a frequency of 0.01 Hz in frequency dispersive dynamic viscoelasticity measurement at 240°C, and [η ^* _(0.1) ] represents the complex viscosity measured at a frequency of 0.1 Hz in a frequency dispersive dynamic viscoelasticity measurement at 240°C.

According to the present invention, expanded polycarbonate resin particles in a favorable foaming state can be provided.

Schematic diagram showing an apparatus for producing resin particles. FIG. 2 is an enlarged view of a main portion of the apparatus of FIG. 1; FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2;

Embodiments of the present invention will be described below.
In the following, as an example of the polycarbonate resin foamed particles, resin particles in a secondary foamed state (hereinafter also referred to as "secondary foamed particles") are obtained by being subjected to secondary foaming by heating in a mold. Next, the present invention will be described by exemplifying an embodiment in which the expanded beads are heat-sealed to form a bead-expanded molded article having a shape corresponding to the molding space of the mold.

The polycarbonate resin foamed particles in the present embodiment are composed of a polycarbonate resin composition containing a polycarbonate resin as a main component.
The polycarbonate resin foamed particles in the present embodiment are produced by melt-kneading a polycarbonate resin composition containing a polycarbonate resin together with a foaming agent in an extruder equipped with a granulating die having a die hole, The kneaded material obtained by the melt-kneading is extruded from the die hole of the granulation die to foam, and the extruded kneaded material is cut at the exit of the die hole to produce a granular material, and the granular material is It is made by water cooling an object.

As the polycarbonate resin in the present embodiment, one that satisfies the following formula (1) is used.

1.6≦[η ^* _(0.01) /η ^* _(0.1) ]≦10 (1)

Here, [η ^* _(0.01) ] in formula (1) represents the complex viscosity measured at a frequency of 0.01 Hz in frequency dispersive dynamic viscoelasticity measurement at 240°C, and [η ^* _(0.1) ] represents the complex viscosity measured at a frequency of 0.1 Hz in a frequency dispersive dynamic viscoelasticity measurement at 240°C.

By the way, in the frequency-dispersive dynamic viscoelasticity measurement of a polymer in a hot-melt state, the degree of viscosity of the polymer tends to appear as a value and its change in the low-frequency range, and the value and the degree of change in the low-frequency range are large. This means that it has high elasticity.
Also, the degree of viscosity of the polymer can be reflected in the value of the phase angle in the low frequency region.
In other words, a large phase angle of the polymer means that the viscous property is exhibited to a high extent with respect to the elastic property.

When producing the foamed polycarbonate resin particles in the present embodiment, a polycarbonate resin composition in a hot melt state is extruded by an extruder and foamed with a foaming agent.
At that time, in order to obtain foamed polycarbonate resin particles in a good foaming state, it is advantageous for the polycarbonate resin to exhibit a certain degree of elasticity.

From the above, in the present embodiment, each value of the complex viscosity (η ^* _(0.1) ) at 0.1 Hz and the complex viscosity (η ^* _(0.01) ) at 0.01 Hz is 1 ×10 ³ or more is preferable.
These values (η ^* _(0.1), η ^* _(0.01) ) are more preferably 1×10 ⁴ or more.
Each of these values (η ^* _(0.1), η ^* _(0.01) ) is preferably 1×10 ⁶ or less, more preferably 1×10 ⁵ or less.
Further, in the present embodiment, the ratio of the complex viscosity (η* _(0.01) ) at 0.01 Hz to the complex viscosity (η ^* ( _0.1 )) at 0.1 Hz ([ ^{η* (} _0.01) /η ^* _{( 0.1)} ], hereinafter also referred to as "viscosity change") is preferably within the above range.

The degree of viscosity change (η ^* _(0.01) /η ^* _(0.1) ) is preferably 9 or less, more preferably 8 or less.
The degree of viscosity change (η ^* _(0.01) /η ^* _(0.1) ) is preferably 1.65 or more, more preferably 1.7 or more, and even more preferably 1.75 or more. .

The polycarbonate resin preferably has a phase angle of 85° or less, more preferably 80° or less at 0.01 Hz, as determined by frequency dispersion dynamic viscoelasticity measurement at 240°C.
However, it is desirable that the phase angle has a value equal to or greater than a certain value.
The phase angle is preferably 40° or more, more preferably 50° or more.

The complex viscosity and the phase angle are obtained as follows.
Dynamic viscoelasticity measurements were made with Anton Paar's "PHYSICA MCR301" viscoelasticity measuring device and "CTD450" temperature control system.
First, the resin is vacuum-dried at a temperature of 120° C. for 3 hours.
The vacuum-dried resin is pressed with a hot press set at a temperature of 220° C. to prepare a disk-shaped test piece with a diameter of 25 mm and a thickness of 3 mm.
Next, the test piece is set on a plate of a viscoelasticity measuring device heated to 240° C. and heated for 5 minutes in a nitrogen atmosphere to melt it.
After that, the test piece is crushed with a parallel plate having a diameter of 25 mm until the interval between the slides becomes 2 mm, and the resin protruding from the plate is removed.
Furthermore, dynamic viscoelasticity measurement is performed after heating for 5 minutes after reaching the measurement temperature ±1°C.
Conditions for dynamic viscoelasticity measurement are strain 5%, frequency 0.01 to 100 (Hz), number of measurement points 21 (5 points/digit), measurement temperature 240°C, measurement start at high frequency side (100Hz ).
Then, from the measurement results, the complex viscosity at a frequency of 0.01 Hz or a frequency of 0.1 Hz and the phase angle δ at a frequency of 0.01 Hz can be obtained.

As the polycarbonate resin contained in the polycarbonate resin composition, one having a repeating structure represented by the following general formula (X) in the molecule can be employed.

-(OR ₁ -O-CO)- (X)

Here, “R ₁ ” in the formula represents a divalent organic group.

The polycarbonate resin in this embodiment is preferably an aromatic polycarbonate resin rather than an aliphatic polycarbonate resin such as poly(propylene carbonate).
That is, "R ₁ " is preferably an organic group represented by the following general formula (Y).

-(Ph-C(CH ₃ ) ₂ -Ph)- (Y)

Here, "Ph" in the formula represents a phenylene group.
The phenylene group may be an o-phenylene group, an m-phenylene group, or a p-phenylene group.

The polycarbonate resin of the present embodiment may have a linear molecular structure or a branched structure.
The polycarbonate resin preferably has a branched structure in that the viscosity change degree and phase angle values easily satisfy the above conditions.
The branched structure of the polycarbonate resin may be provided during polymerization or may be provided by modification after polymerization.
The polycarbonate resin may be modified to have a branched structure during polymerization to further improve the degree of branching.

The polycarbonate resin may be polymerized by a phosgene method using phosgene or may be polymerized by a non-phosgene method that does not use phosgene.
The polycarbonate resin may be polymerized by interfacial polymerization or transesterification.
The polycarbonate resin is preferably polymerized by a non-phosgene method, and preferably polymerized by a transesterification method.

The polycarbonate resin is tested at a temperature of 300 based on JIS K7210-1:1999 "Plastics-Determination of melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics-Part 1: standard test method". C. and a nominal load of 1.2 kgf (hereinafter also referred to as "MFR") is preferably 0.1 g/10 min or more, more preferably 0.5 g/10 min or more.
The MFR of the polycarbonate resin is preferably 3.0 g/10 min or less, more preferably 2.5 g/10 min or less, even more preferably 2.3 g/10 min or less.

The polycarbonate resin composition in the present embodiment may be composed of only one or more of the polycarbonate resins.
The polycarbonate resin composition may contain a resin other than the polycarbonate resin.
Examples of resins other than the polycarbonate resin include polyester resins such as polyethylene terephthalate resin; polystyrene resins such as GPPS and HIPS; polyethylene resins such as LDPE, L-LDPE and HDPE; homopolypropylene, block polypropylene and random polypropylene. polypropylene resin; acrylic resin such as poly(meth)acrylic acid ester; and the like.
Resins other than the polycarbonate resin are usually contained in the polycarbonate resin composition so that the ratio of the resin to the total of the polycarbonate resin is less than 50% by mass.
The ratio may be, for example, anywhere in the range of 10% by mass or more and 45% by mass or less.

The polycarbonate resin composition may contain various additives in addition to the polycarbonate resin.
Examples of the additives include inorganic fillers such as talc that function as cell control agents and organic fillers such as polytetrafluoroethylene powder.
Examples of the additives include plasticizers, lubricants, antioxidants, antistatic agents, ultraviolet absorbers, light stabilizers, colorants, antibacterial agents, anti-rat agents, and insect repellents.
In addition, in order to make the polycarbonate resin foamed particles remarkably exhibit the properties derived from the polycarbonate resin, the content of components other than the polycarbonate resin, such as the additives, in the polycarbonate resin foamed particles should be 20% by mass or less. It is preferably 15% by mass or less, more preferably 10% by mass or less.

As a foaming agent for foaming the polycarbonate resin composition, known volatile foaming agents and inorganic foaming agents can be used.
Volatile foaming agents include aliphatic hydrocarbons such as propane, butane, and pentane, aromatic hydrocarbons, alicyclic hydrocarbons, and aliphatic alcohols.
Examples of inorganic foaming agents include carbon dioxide gas, nitrogen gas, air, and inert gases (helium, argon, etc.).
You may use together 2 or more types of these foaming agents.
Among these, the foaming agent in the present embodiment is preferably an inorganic foaming agent, and more preferably a carbon dioxide gas.

The expanded polycarbonate resin particles of the present embodiment are produced using an extruder as described above.
FIG. 1 shows a granulating apparatus T for producing polycarbonate resin expanded particles, and FIG. 2 shows a granulating die 1 for the water ring hot cut method and its peripheral equipment.
FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, and shows a front view of the die body 10 (also called a die plate).

As shown in the figure, the granulating apparatus T has a granulating die 1 attached to its tip end and a hopper HP for material supply at its base end. It has an extruder 2 provided with a foaming agent introduction hole BH for introducing a foaming agent BA into the inside on the way to 1.
The granulating device T accommodates a cutter 3 for cutting the melt-kneaded material 20 (a polycarbonate resin composition in a molten state) discharged from the die hole 15 of the granulating die 1. A chamber 4 is provided for forming a space 4a covering the front surface (resin discharge surface 10f) in the extrusion direction.

As shown in the figure, the granulator T includes a die body 10 (also called a die plate) and a die holder 11 fixed to the tip side of the extruder 2. The die body 10 is fixed to the tip side of the die holder 11 .

The die holder 11 has an internal channel 11a that communicates with the cylinder of the extruder 2, and is configured to supply the melt-kneaded material 20 from the extruder 2 toward the die body 10 through the internal channel. there is

The die body 10 branches the melt-kneaded material 20 supplied through the internal flow path 11a of the die holder 11 so as to flow through a plurality of resin flow paths 14 extending along the extrusion direction and parallel to each other. The melted and kneaded material 20 is discharged from the die hole 15 which is an opening at the tip of each resin channel 14 .

In the resin discharge surface 10f of the die main body 10, the plurality of die holes 15 serving as the outlets of the melt-kneaded material 20 from the respective resin flow paths 14 are arranged on the same circumference (on the circumference of the virtual circle CX in FIG. 4). distributed at intervals.

The cutter 3 includes a substrate 31 arranged to face the resin ejection surface 10f, a plurality of cutting blades 32 arranged to protrude from the substrate 31 toward the resin ejection surface 10f, and the substrate. and a rotating shaft 33 that rotates 31 .
The rotating shaft 33 passes through the center of the circumference where the outlet of the resin flow path 14 is arranged and extends along a direction (extrusion direction) perpendicular to the resin discharge surface 10f. It is connected to the substrate 31 so as to rotate the substrate 31 while maintaining it parallel to the resin discharge surface 10f.
The plurality of cutting blades 32 are arranged so that the cutting edge extends in a direction radially extending from the connecting position of the rotating shaft 33 and the substrate 31, and the cutting edge moves circularly while sliding on the resin discharge surface 10f. is distributed to
The cutter 3 is arranged so that when the substrate 31 is rotated by the rotary shaft 33 , the cutting edge of the cutting blade 32 cuts the molten kneaded material 20 extruded from the die hole 15 into granules.

The chamber 4 in the granulator T has a flat columnar internal space 4a having a central axis that overlaps the rotating shaft 33, and a water supply for introducing cooling water AQ into the internal space 4a. A port 4b and a drain port 4c for discharging the cooling water AQ introduced into the internal space 4a from the water supply port 4b are provided.
The chamber 4 has a front wall 41 disposed forward in the extrusion direction with a distance from the die plate, and a peripheral side wall extending in a cylindrical shape from the outer peripheral edge of the front wall 41 to the rear (toward the die plate). 42.
The front wall 41 in this embodiment has a disc shape with a diameter larger than that of the die plate, and the peripheral side wall 42 has a cylindrical shape.
In the chamber 4, the cooling water AQ is introduced from the water supply port 4b so that the cooling water AQ circulates along the inner wall surface 42a of the peripheral side wall 42, and the cooling water AQ flowing along the inner wall surface 42a flows. It is configured to be discharged from the drain port 4c.
That is, the chamber 4 is configured so that a water film can be formed by the cooling water AQ along the inner wall surface 42a.

In the granulator T, the melt-kneaded product 20 is extruded into the air from the die hole 15 in the chamber 4 while foaming, and the melt-kneaded product 20 immediately after being extruded from the die hole 15 is the outlet of the die hole 15. , the granular material B' is cut by the cutting blade 32 of the cutter 3 to form a granular material B', and the granular material B' is flung outward in the radial direction by the rotating cutting blade 32, and the flicked granular material B' is It collides with the water film formed along the inner wall surface 42a and is cooled by the water film (cooling water AQ).

That is, in the water ring hot cut method, the melt-kneaded material 20 is foamed immediately after extrusion, and a short time is provided until the melt-kneaded material, which has started foaming and has become granular, is cooled with water and foaming is suppressed. It is designed to be
Therefore, the degree of foaming of the foamed polycarbonate resin particles in the present embodiment can be adjusted by the speed of the cutter 3, the temperature of the cooling water AQ, etc., in addition to the amount of foaming agent used.

The granulator T of the present embodiment is configured so that the granular material B' after cooling can be recovered as the expanded polycarbonate resin particles B. As shown in FIG.
A pipeline 5 for supplying the cooling water AQ is connected to the granulating die 1 , and one end of the pipeline 5 is connected to a water tank 7 via a water pump 6 .
In the granulator T, the melt-kneaded material 20 that has been cooled and solidified becomes polycarbonate resin foamed particles B and is discharged from the chamber 4 together with the cooling water AQ, and the expanded particles are separated from the cooling water by the dehydrator 8. .
The cooling water AQ separated by the dehydrator 8 can be cooled by, for example, a chiller (not shown) and then returned to the water tank 7 for reuse.

The temperature of the cooling water AQ supplied to the chamber 4 from the water supply port 4b is, for example, preferably 5° C. or higher and 40° C. or lower, more preferably 8° C. or higher and 30° C. or lower, and 10° C. or higher and 35° C. or higher. °C or less is more preferable.
Incidentally, the temperature and the circulation amount of the cooling water AQ can be appropriately selected according to the production amount of the polycarbonate resin expanded particles and the degree of foaming of the polycarbonate resin expanded particles.

When producing polycarbonate resin foamed particles having a low expansion ratio, a production method by an underwater hot cut method may be employed in place of the production method by a water ring hot cut method as described above.
The underwater hot-cutting method is carried out with the same equipment as the water-ring hot-cutting method except that the die holes are always in contact with the cooling water in the chamber.
In the underwater hot cutting method, the melt-kneaded product 20 is directly extruded into water, so it is possible to suppress the progress of foaming in the melt-kneaded product 20 immediately after extrusion. Resin particles can also be obtained.

The size and shape of the polycarbonate resin foamed particles produced in the present embodiment are not particularly limited, but the size (average particle diameter) is such that the diameter when the apparent volume is converted to a true sphere is 1 mm to 6 mm. Preferably.
More preferably, the diameter is between 1.5 mm and 5 mm.

The volume multiple of the expanded polycarbonate resin particles produced as described above is preferably 2 or more and 5 or less.
Incidentally, the bulk multiple can be obtained by the following method.
(How to find bulk multiple)
About 1000 cm ³ of polycarbonate resin foamed particles are filled into a graduated cylinder to the mark of 1000 cm ³ .
When the graduated cylinder is visually inspected from the horizontal direction and even one of the expanded polycarbonate resin particles reaches the scale of 1000 cm ³ , the charging of the expanded polycarbonate resin particles into the graduated cylinder is terminated at that point.
Next, the mass of the foamed polycarbonate resin particles filled in the graduated cylinder is weighed to two significant figures after the decimal point, and the mass is defined as W (g). Then, the bulk density of the expanded polycarbonate resin particles is determined by the following formula.

Bulk density (g/cm ³ ) = W/1000

The bulk multiple can be determined by multiplying the reciprocal of the bulk density by the density (g/cm ³ ) of the polycarbonate resin composition (density in the non-foamed state).

The density of the polycarbonate resin composition can be determined by JIS K7112: 1999 "Plastics - Determination of density and specific gravity of non-foamed plastics", Method A (water substitution method), or the like.

The expanded polycarbonate resin particles can be used as pre-expanded particles, which are raw materials for producing the foamed beads as described above.
A bead-expanded molded article is a molded article in which a plurality of resin expanded particles are heat-sealed and integrated.
In the present embodiment, a bead-expanded molded article in which a plurality of polycarbonate resin expanded particles are integrated is formed, so that the bead-expanded molded article has excellent strength and heat resistance.

When producing the expanded beads molded article, a mold having a molding space corresponding to the expanded beads molded article is used, and the pre-expanded particles (expanded polycarbonate resin particles) are accommodated in the molding space in the mold. heating the pre-expanded particles in a state in which the molding space is filled with a plurality of pre-expanded particles, and secondary expansion of the pre-expanded particles to form secondary expanded particles; A heat-sealing method can be employed.

The apparent density of the beads-expanded molded product produced as described above can be adjusted by the amount of pre-expanded particles filled in the mold, the bulk density, etc. The apparent density is 10 kg/m ³ or more and 500 kg/m ³ or less. is preferably

The apparent density of the foamed beads can be determined, for example, as follows.
Cut out a sample of 100 cm ³ or more by cutting so as not to change the original cell structure as much as possible, and condition this sample for 16 hours in a JIS K7100: 1999 symbol 23/50, class 2 environment. is measured, and the density is calculated by the following formula.

Apparent density (kg/m ³ ) = sample mass (kg)/sample volume (m ³ )

For the dimensional measurement of the sample, for example, "DIGIMATIC" CD-15 type manufactured by Mitutoyo Co., Ltd. can be used.

It is preferable that the pre-expanded particles and the foamed beads have a dense structure with an average cell diameter of 300 μm or less. The average cell diameter is more preferably 200 μm or less, and even more preferably 100 μm or less.

The average bubble diameter can be obtained as follows.
(How to find the average bubble diameter)
When the bead-expanded molded article is composed of secondary expanded particles, the size of the bubbles at the interface between adjacent particles may differ greatly from the inside. Avoid measuring.
That is, the average cell diameter can be measured based on the image obtained by photographing a cross section obtained by cutting the secondary expanded bead into two at the center approximately with a scanning electron microscope. Specifically, a photograph of the cross section is taken with a scanning electron microscope (for example, S-3000N manufactured by Hitachi, Ltd. or S-3400N manufactured by Hitachi High-Technologies Corporation).
The photographing is performed by photographing the central portion of each of four secondary foamed beads randomly selected from the secondary foamed beads that are considered to be divided into two at the center.
Print the photographs taken on A4 paper, two images each horizontally and vertically, for a total of four images, and calculate the average chord length (t) of the bubbles from the number of bubbles on an arbitrary straight line (length 60 mm) parallel to the vertical and horizontal directions. Calculated by the formula. However, an arbitrary straight line should be drawn so that bubbles do not come into contact with each other as much as possible (if they do, they are included in the number of bubbles).
Measurement shall be made at 6 points each in length and width for each image.

Average chord length t (mm) = 60/(number of bubbles x magnification of photo)

Then, the bubble diameter in each direction is calculated by the following equation.

D (mm) = t/0.616

Furthermore, let the square root of the product of them be the average bubble diameter.

Average bubble diameter (mm) = (D length x D width) ^1/2

The polycarbonate resin foamed particles of the present embodiment and the beads foamed molded product obtained by using the polycarbonate resin foamed particles are suitable for mobile objects such as automobiles, trains, ships, and airplanes; It can be used in various applications such as home appliances such as machines, room air conditioners, heaters, ovens, microwave ovens, and rice cookers; electronic devices such as smartphones, tablets, and personal computers;
The resin foam of the present invention can be used for applications other than those described above, and is not limited to the examples given in this specification.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these.

First, the following four kinds of polycarbonate resins were prepared.
PC1:
Aromatic polycarbonate resin PC2 having a branched structure and an MFR of 1.7 g/10 min:
Aromatic polycarbonate resin PC3 having a branched structure and an MFR of 2.2 g/10 min:
Aromatic polycarbonate resin PC4 having a branched structure and an MFR of 3.9 g/10 min:
An aromatic polycarbonate resin having a branched structure and an MFR of 4.6 g/10 min

(Example 1)
1) Production of Polycarbonate Resin Expanded Beads The polycarbonate resin expanded beads of Example 1 were produced by the water ring hot cut method using the apparatus shown in FIGS.
A granulating die in which 20 die holes with a diameter of 1 mm are arranged at equal intervals on a circumference of a diameter of 139.5 mm was used to produce the expanded polycarbonate resin particles.
The granulating die was attached to the tip of the second extruder of a tandem type extruder in which the second extruder with a diameter of 65 mm was connected to the tip of the first extruder with a diameter of 50 mm.
Polycarbonate resin (PC1) was supplied to the first extruder and melt-kneaded at 300°C.
Carbon dioxide was supplied to the first extruder at a rate of 1.5 parts by mass per 100 parts by mass of the polycarbonate resin, and a melt-kneaded product containing the polycarbonate resin and carbon dioxide was prepared in the extruder.
In the second extruder, the melt-kneaded product was continuously melt-kneaded and cooled to a resin temperature of 261°C.
The melt-kneaded product is extruded from the die hole of the granulation die at a total discharge rate of 30 kg/hour, and the melt-kneaded product immediately after being extruded from the die hole and foamed is cut with a cutter rotating at a speed of 3400 rpm to produce granules. was prepared, and the granules were plunged into cooling water and cooled to prepare expanded polycarbonate resin particles.
When the bulk density and bulk multiple of the obtained polycarbonate resin foamed particles were measured, the bulk density was 0.346 g/cm ³ and the bulk multiple was 3.5 times.

2) Evaluation For the polycarbonate resin used, frequency dispersion dynamic viscoelasticity measurement was performed at 240 ° C., and the complex viscosity and viscosity change degree at 0.01 Hz and 0.1 Hz were measured, and the phase angle at 0.01 Hz. was measured.
Further, the secondary foamability of the obtained expanded polycarbonate resin particles was evaluated.
The secondary foamability was evaluated by calculating a value obtained by dividing the bulk density before secondary foaming by the bulk density after secondary foaming.
Specifically, secondary foamability was evaluated when secondary foaming was performed as follows.
- Secondary foamability evaluation method Polycarbonate resin foamed particles were placed in a pressure vessel and sealed.
The inside of the sealed pressure vessel was pressurized to a gauge pressure of 1 MPa using nitrogen gas and allowed to stand for 24 hours to apply the internal pressure.
The nitrogen gas in the pressure vessel in which the internal pressure was applied was slowly released, and the expanded polycarbonate resin beads were taken out, heated by introducing steam at 0.34 MPa for 15 seconds, and cooled to obtain secondary expanded beads.
The bulk density of the secondary expanded particles obtained by secondary expansion of the polycarbonate resin expanded particles of Example 1 was 0.152 g/cm ³ .

(Examples 2-3, Comparative Examples 1-2)
Polycarbonate resin expanded beads were prepared in the same manner as in Example 1 except that the resin and the amount of the foaming agent used were changed as shown in Table 1, and evaluated in the same manner as in Example 1.

From the above, it can be seen that the present invention can provide polycarbonate resin foamed particles in a favorable foaming state.

1: Granulation die, 2: Extruder, 3: Cutter, 4: Chamber, 15: Die hole, 20: Melt-kneaded material, AQ: Cooling water, B': Granular material, B: Polycarbonate resin expanded particles

Claims (3)

Using an extruder equipped with a granulation die with a die hole,
Melt-kneading a polycarbonate resin composition containing a polycarbonate resin together with a foaming agent in the extruder,
The kneaded product obtained by the melt-kneading is extruded from the die hole of the granulation die to foam,
cutting the extruded kneaded material at the outlet of the die hole to produce a granular material;
Water-cooling the granules to produce polycarbonate resin expanded particles,
A method for producing expanded polycarbonate resin particles using a polycarbonate resin satisfying the following formula (1) as the polycarbonate resin.

1.6≦[η ^* _(0.01) /η ^* _(0.1) ]≦10 (1)

(Here, [η ^* _(0.01) ] in formula (1) represents the complex viscosity measured at a frequency of 0.01 Hz in frequency dispersive dynamic viscoelasticity measurement at 240°C, and [η ^* _{(0.1 )} ] represents the complex viscosity measured at a frequency of 0.1 Hz in a frequency dispersive dynamic viscoelasticity measurement at 240°C.) 2. The method for producing expanded polycarbonate resin particles according to claim 1, wherein the phase angle at 0.01 Hz of the polycarbonate resin determined by frequency dispersion dynamic viscoelasticity measurement at 240[deg.] C. is 40[deg.] or more and 80[deg.] or less. 3. The method for producing expanded polycarbonate resin beads according to claim 1 or 2, wherein the expanded polycarbonate resin beads having a bulk multiple of 2 times or more and 5 times or less are manufactured.

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