JP2004204110A - Apparatus for manufacture of foaming thermoplastic resin particle, method of manufacturing the particle and the particle obtained - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for efficient and inexpensive manufacture of a foaming thermoplastic resin particle without an aqueous medium and excessive energy, a method of manufacturing the particle, and the particle obtained. <P>SOLUTION: The apparatus has a bulk polymerization process portion 10 for production of a thermoplastic resin by bulk polymerization and an extrusion cutting process portion 20 having an extruder 21 connected to a flow line 25 supplying a molten resin 19 from a deairing section 12 and a flow line 26 supplying a foaming agent and a cutter 23 cutting the resin extruded from a die 22 connected to the extruder 21 to form a foaming thermoplastic resin particle 40. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for producing expandable thermoplastic resin particles, a method for producing expandable thermoplastic resin particles, and a method for producing expandable thermoplastic resin particles for efficiently and inexpensively producing expandable thermoplastic resin particles used for producing an expanded resin molded article. The foamable thermoplastic resin particles obtained.
The expandable thermoplastic resin particles obtained by the present invention are used for cups such as instant foods, for various packing, for fish boxes, for blocks such as lightweight embankment methods, for lost molding in casting, various OA equipment, audio equipment, It is suitably used as a raw material of a foamed resin molded product used as a buffer packaging material for electric appliances and the like.
[0002]
[Prior art]
Conventionally, as a method for producing expandable thermoplastic resin particles used in the production of an expanded resin molded article, a method of producing an expandable thermoplastic resin particle by adding a foaming agent to resin particles obtained by a suspension polymerization method has been known. It is known (for example, refer to Patent Documents 1 and 2).
As another method for producing expandable thermoplastic resin particles, a thermoplastic resin pellet in a solid state is introduced into an extruder, the temperature is raised in the extruder, a foaming agent is injected into a melted resin, mixed, and the resultant is die-died. There is also known a method of producing expandable thermoplastic resin particles by simultaneously extruding the resin into a strand shape and cutting the same (for example, see Patent Documents 3 to 5).
[0003]
[Patent Document 1]
Japanese Patent No. 3192916
[Patent Document 2]
Japanese Patent No. 3054017
[Patent Document 3]
Japanese Patent Publication No. 5-59138
[Patent Document 4]
JP-A-6-32932
[Patent Document 5]
JP-A-6-31726
[0004]
[Problems to be solved by the invention]
However, when producing the resin particles using the above-described suspension polymerization method, since a polymerization reaction is performed in an aqueous medium, a large amount of waste liquid containing a suspension stabilizer, a surfactant, a polymerization initiator, and the like is generated, There remains a problem that a wastewater treatment facility for treating the waste liquid is required and wastewater treatment costs are high.
[0005]
In the method using solid resin pellets, the solid-state thermoplastic resin pellets must be heated to a molten state in an extruder, which requires extra heat energy and increases the energy cost. Had left.
[0006]
The present invention has been made in view of the above circumstances, without using an aqueous medium, without using extra energy, to efficiently and inexpensively produce expandable thermoplastic resin particles used in the production of foamed resin molded articles. It is an object of the present invention to provide an apparatus for producing expandable thermoplastic resin particles, a method for producing expandable thermoplastic resin particles, and an expandable thermoplastic resin particle obtained by the method.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a polymerization section in which a raw material monomer is bulk-polymerized to form a thermoplastic resin, and a degassing section in which volatile components are removed from the obtained thermoplastic resin. The bulk polymerization process section for producing a thermoplastic resin by the, the resin supply line and the foaming agent supply line to which the molten thermoplastic resin is supplied from the degassing section of the bulk polymerization process section, from the upstream to the downstream in the resin flow direction. An extruder that extrudes a blowing agent-containing resin from a die at a terminal in a resin flow direction, and a cutter that cuts the blowing agent-containing resin extruded from the die into granules. The present invention provides an apparatus for producing expandable thermoplastic resin particles, characterized in that:
In the apparatus for producing expandable thermoplastic resin particles of the present invention, a configuration having a second extruder that supplies a resin for blending to the extruder between the resin supply line and the blowing agent supply line of the extruder. It may be.
Further, the blending resin may be supplied to the extruder in a molten state.
Further, the extruder may have an additive supply line between the resin supply line and the foaming agent supply line or connected to the second extruder.
Further, the extruder may be a twin-screw extruder.
Further, the extruder may have a deaeration section upstream of the foaming agent supply line connection position in the resin flow direction in order to remove volatile components in the resin in the extruder.
Further, the extruder may be provided with a cooling means for cooling the resin in the extruder, at a position where the foaming agent supply line is connected to the extruder or at a position downstream of the position in the resin flow direction.
Further, the extruder may be provided with a gear pump for increasing pressure.
Further, the resin supply line may have a blow-down portion for extracting the molten resin supplied through the line.
Preferably, the thermoplastic resin is a polystyrene resin.
[0008]
Also, the present invention provides (A) a step of producing a thermoplastic resin by bulk polymerization of a raw material monomer to produce a thermoplastic resin, and removing volatile components from the obtained thermoplastic resin;
(B) The thermoplastic resin is supplied to the extruder in a molten state, and a foaming agent is injected into the thermoplastic resin while moving the resin toward the die at the end of the extruder in the resin flow direction. Forming,
(C) cutting the resin containing the foaming agent extruded from the die into granules to produce foamable thermoplastic resin particles.
Further, the extruder in the step (B) is preferably a twin-screw extruder.
In the step (C), the foaming agent-containing resin extruded into the cooling liquid in the form of a strand from the hole of the die is extruded and cut into granules at the same time as being extruded. Is a process of producing expandable thermoplastic resin particles by suppressing the resin particles obtained by this, the corners are rounded, so that it becomes easy to handle, and since the fusion of the particles after foaming becomes good, preferable.
In the method of the present invention, the thermoplastic resin is preferably a polystyrene resin.
Further, the polystyrene resin supplied to the extruder has the following conditions a and b:
a. The weight average molecular weight Mw is in the range of 150,000 to 400,000,
b. The volatile matter content is 1000 ppm or less;
It is preferable that the above condition be satisfied.
Further, the polystyrene resin supplied to the extruder preferably has a polymerization conversion of 95% or more.
Further, the weight average molecular weight of the polystyrene resin is preferably 200000 to 350,000.
Further, the volatile content of the polystyrene resin is preferably 500 ppm or less.
Further, in the step (B), a resin for blending can be mixed before a foaming agent is injected into the thermoplastic resin in the extruder.
Further, it is preferable that the blending resin is supplied in a molten state into the extruder.
In the step (B), an additive can be mixed with the thermoplastic resin or the blending resin in the extruder.
In the step (B), the thermoplastic resin in the extruder may be deaerated.
Further, the method may further include a step of extracting a part of the thermoplastic resin in a molten state to be supplied from the step (A) to the step (B) to produce resin pellets.
[0009]
The present invention also provides expandable thermoplastic resin particles produced by the method for producing expandable thermoplastic resin particles according to the present invention described above.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
In the present invention, examples of the thermoplastic resin include thermoplastic resins that can be produced by a bulk polymerization process, such as polystyrene resins, polyethylene resins, polypropylene resins, vinyl chloride resins, ABS resins, and AS resins. In particular, polystyrene resins such as polystyrene (GPPS) and high impact polystyrene (HIPS) are preferably used.
In the present invention, as the foaming agent, an aliphatic hydrocarbon-based foaming agent, a halogenated hydrocarbon-based foaming agent, or the like that can impart foaming properties to the thermoplastic resin by being contained in the thermoplastic resin can be used.
In the present invention, the expandable thermoplastic resin particles refer to resin particles formed into particles, preferably small spheres, by adding a foaming agent to the thermoplastic resin. The expandable thermoplastic resin particles are pre-expanded by heating in a free space, and the pre-expanded particles are put into the cavity of a mold having a cavity of a desired shape, and steam-heated to melt the pre-expanded particles. After being dressed, it can be released and used to produce a foamed resin molded product having a desired shape.
In the present invention, as the blending resin optionally blended with the thermoplastic resin, a thermoplastic resin of a different type from the thermoplastic resin, or the same or the same thermoplastic resin as the thermoplastic resin may be used. For example, when a polystyrene resin is used as the thermoplastic resin, a polyethylene resin or the like can be used as the resin for blending. Further, additives such as a coloring agent and an inorganic powder can be mixed in the resin for blending. Further, as the resin for blending, various kinds of recovered resins obtained by once used as a resin product and then recovered can be blended and used.
[0011]
FIG. 1 is a schematic diagram showing an embodiment of an apparatus for producing expandable thermoplastic resin particles according to the present invention. The apparatus includes a polymerization section 11 for producing a thermoplastic resin by bulk polymerization of raw material monomers, and A deaeration section 12 for removing volatiles from the obtained thermoplastic resin, and a bulk polymerization process section 10 for producing a thermoplastic resin by a bulk polymerization method; and a degassing section 12 of the bulk polymerization process section. The resin supply line 25 to which the molten thermoplastic resin is supplied and the blowing agent supply line 26 are connected in order from upstream to downstream in the resin flow direction, and extrude the blowing agent-containing resin from the die 22 at the end in the resin flow direction. The extruder 21 has an extruding and cutting process unit 20 having a cutting agent 23 for cutting the foaming agent-containing resin extruded from the die 22 into granules. To have.
[0012]
In the present embodiment, the bulk polymerization processing section 10 includes a polymerization section 11, a degassing section 12, a monomer recovery section 13 for recovering volatile components including a monomer separated in the degassing section 12, and a raw material in the polymerization section 11. A monomer supply line 14 for supplying a monomer, a line 15 for sending a liquid containing the thermoplastic resin synthesized in the polymerization section 11 to the degassing section 12, and a molten thermoplastic resin (hereinafter referred to as a molten resin) from the degassing section 12. 19), a line 17 for sending volatile components from the degassing section 12 to the monomer recovery section 13, and a line 18 for sending the monomer recovered in the monomer recovery section 13 to the monomer supply line 14. It is configured.
[0013]
The bulk polymerization process section 10 may be appropriately selected from conventionally known bulk polymerization apparatuses according to the type of thermoplastic resin to be produced, the production scale, and the like, or may be used by changing the apparatus as necessary. it can. For example, when the thermoplastic resin to be produced is a polystyrene resin, a conventionally known continuous bulk polymerization process for producing polystyrene (GPPS or HIPS) can be used (edited by Koji Saeki and Shinzo Omi, “New” Polymer Production Process ", published by the Industrial Research Council (1994).) In a preferred embodiment of the present invention, when the thermoplastic resin is a polystyrene resin, the bulk polymerization process section 10 has a weight average molecular weight Mw in the range of 150,000 to 400,000, preferably in the range of 200,000 to 350,000, and has a volatile content of An apparatus capable of continuously producing a styrene-based resin having a polymer conversion ratio of 1000 ppm or less, preferably a polymerization conversion rate of 95% or more, and preferably a volatile matter content of 500 ppm or less by a bulk polymerization method is used.
[0014]
In the present embodiment, the extrusion cutting process unit 20 includes an extruder 21, a die 22 connected to an end of the extruder 21 in the resin flow direction F, and a cutter 23 that cuts the foaming agent-containing resin extruded from the die 22 into particles. A resin supply line 25 for supplying a molten resin 19 from which volatile components have been removed in the degassing section 12 of the bulk polymerization process section 10 to an extruder 21 and a resin for blending to the extruder 21 through a second resin supply line 29. A second extruder 24, a foaming agent supply line 26 for supplying a foaming agent such as pentane, isopentane, butane, etc. from a foaming agent tank 27 via a feeder 28 to the extruder 21, and a resin supplying line 25 are provided in the middle. Blown-down section 30 and a blending resin storage section 3 for supplying additives such as a blending resin and a colorant through a line 32 to a second extruder 24. And a dehydrator 34, which is cut by the cutter 23 and dewatered from the expandable thermoplastic resin particles 40 sent through the line 33 together with water, and further dried, and the expandable thermoplastic resin particles 40 after dehydration and drying have a desired particle size. The apparatus is provided with a classifier 35 that classifies the particles into a range and sends the particles to a particle receiving unit 36, and a particle storage unit 37 that stores the classified expandable thermoplastic resin particles 40.
[0015]
The extruder 21 may be a conventionally known extruder used in the synthetic resin molding field, and may be an extruder using a screw or an extruder not using a screw. Examples of the extruder using a screw include a single-screw extruder, a twin-screw extruder, and a multi-screw extruder having three or more screws, and examples of the extruder that does not use a screw include a gear pump extruder and a plunger-type extruder. . These can be appropriately selected from these and used, or they may be used by being connected in multiple stages. Preferred are a single-screw extruder and a twin-screw extruder excellent in kneading properties of a resin and a foaming agent, and particularly preferred are a twin-screw extruder excellent in stability of constant-rate extrusion. In the present embodiment, a resin supply line 25, a second resin supply line 29, and a foaming agent supply line 26 are sequentially connected to the extruder 21 from upstream to downstream in the resin flow direction F. The molten resin 19 supplied to the extruder 21 in a molten state flows from the second extruder 24 to the second extruder 24 as necessary while flowing toward the die 22 connected to the end thereof in the resin flow direction F. Is mixed with the blending resin sent through the resin supply line 29. Further, the molten resin 19 or the mixed resin of the molten resin 19 and the blending resin moves to a connection position of the foaming agent supply line 26, where the foaming agent is injected and becomes a foaming agent-containing resin, and becomes a resin-flowing resin F terminal. From the die 22.
[0016]
When an extruder having a low extrusion pressure is used, a gear pump (not shown) for increasing pressure can be provided between the extruder 21 and the die 22. As the gear pump, a gear pump having an appropriate boosting performance can be appropriately selected and used from boosting gear pumps usually used in the synthetic resin molding field.
Further, it is preferable to provide a cooling means for cooling the resin in the extruder, at a connection position of the foaming agent supply line 26 of the extruder 21 or at a position downstream of the position in the resin flow direction F. As this cooling means, a jacket-type cooler attached to the outer periphery of the extruder 21 or the like is used.
Further, a degassing section (not shown) for removing volatile components in the resin in the extruder 21 may be provided upstream of the extruder 21 in the resin flow direction F from the connection position of the foaming agent supply line 26. By providing such a degassing section, volatile components can be removed from the resin in the extruder 21 to further reduce the content of volatile components such as residual monomers.
[0017]
As the die 22 connected to the extruder 21, a conventionally known die used in a general resin molding field, particularly in the production of expandable thermoplastic resin particles, can be used. A large number of extrusion holes for the foaming agent-containing resin provided in the die 22 are set to be approximately the same as or slightly smaller than the diameter of the expandable thermoplastic resin particles 40 to be produced. It is preferable to use a circular hole of about 3 to 1 mm.
[0018]
The foaming agent-containing resin extruded from the die 22 is cut by the cutter 23 to form foamable thermoplastic resin particles 40. As the cutter 23, any of a hot cut method and a cold cut method can be used. In the present embodiment, while supplying circulating water to the cutter 23 in the cutting chamber, the blowing agent-containing resin extruded from the die 22 is cut immediately after being extruded, and the cut foamable thermoplastic resin particles 40 are cut into a line with circulating water. It is configured to be supplied to a dehydrator 34 through 33.
[0019]
The dehydrator 34 separates the expandable thermoplastic resin particles 40 conveyed through the line 33 from the circulating water by a circulating water flow, and dewaters and drys the expandable thermoplastic resin particles 40 by blast drying or the like. A screen, a centrifuge, or the like can be used to separate water from circulating water. In the present example, the water separated from the expandable thermoplastic resin particles 40 is supplied to the cutter 23 in the cutting chamber through the line 38 for circulating use.
As the classifier 35, the particle receiving unit 36, and the particle storage unit 37, conventionally known devices used for classification, storage, and transfer of various particles can be used.
[0020]
In the present embodiment, the resin supply line 25 is provided with a blow-down unit 30 for extracting the molten resin 19 supplied through the line. In a preferred embodiment, the blow-down section 30 has a pellet molding section (not shown) for extracting the molten resin 19 from the resin supply line 25 and forming solid resin pellets. By providing such a blow-down unit 30, when the amount of the molten resin processed by the extrusion cutting process unit 20 is lower than the amount of the molten resin produced by the bulk polymerization process unit 10, the mass is produced by the mass polymerization process unit 10. Excess molten resin 19 can be withdrawn from blowdown section 30 to produce and store solid resin pellets.
Therefore, by providing the blow-down unit 30, the bulk polymerization process unit 10 can be continuously operated irrespective of a decrease in the throughput of the extrusion cutting process unit 20, and the bulk polymerization process unit 10 associated with a decrease in the throughput is increased. Of the production efficiency and energy loss can be prevented.
The solid resin pellets produced from the molten resin 19 extracted in the blowdown section 30 are used as a raw material for producing another thermoplastic resin molded product or for blending supplied to the extruder 21 via the second extruder 24. It can be used as a component of resin.
[0021]
The configurations of the bulk polymerization process section 10 and the extrusion cutting process section 20 are merely examples of the production apparatus according to the present invention, and the types of the thermoplastic resin and the foaming agent to be used, the extrusion method, the cutting method, and the collection of particles. According to changes in the method, the method of drying particles, the method of finishing, and the like, appropriate changes can be made by inserting, replacing, or deleting appropriate devices. For example, when adding an additive such as a coloring agent, the additive is mixed into the resin for blending, and then, instead of supplying the resin for blending to the extruder 21 through the second extruder 24, the additive is added. An additive supply line for mixing directly into the extruder 21 may be provided.
Further, the extruder 21 may adopt a tandem type in which an upstream twin-screw extruder and a downstream single-screw extruder are connected.
Further, in the blow-down unit 30, a control unit for adjusting the amount and timing of extracting the molten resin 19 from the resin supply line 25 may be provided.
[0022]
The apparatus for producing expandable thermoplastic resin particles supplies the thermoplastic resin produced by bulk polymerization to the extruder 21 in a molten state, mixes in the foaming agent, extrudes from the die 22 and cuts the foamed thermoplastic resin. Since the resin particles 40 are formed, a large amount of aqueous medium, which is a problem in the suspension polymerization method, is not required, and a wastewater treatment facility required for wastewater treatment of the aqueous medium is not required. In addition, the operating cost can be reduced. Further, since the expandable thermoplastic resin particles can be efficiently and continuously produced, the production cost is reduced.
Furthermore, compared to the method of introducing solid resin pellets into an extruder, re-melting and injecting and mixing a foaming agent to produce expandable thermoplastic resin particles, there is no energy loss required for re-melting, and energy costs are reduced. be able to.
Therefore, according to the present invention, expandable thermoplastic resin particles can be produced at low cost.
[0023]
Next, a method for producing expandable thermoplastic resin particles according to the present invention will be described.
The method of the present invention comprises the following steps (A) to (C):
(A) a step of producing a thermoplastic resin by bulk polymerization of the raw material monomers to produce a thermoplastic resin, and removing volatile components from the obtained thermoplastic resin;
(B) The thermoplastic resin is supplied to the extruder in a molten state, and a foaming agent is injected into the thermoplastic resin while moving the resin toward the die at the end of the extruder in the resin flow direction. Forming,
(C) a step of producing foamable thermoplastic resin particles by cutting the foaming agent-containing resin extruded from the die of the extruder into granules.
The method of the present invention is preferably carried out using the above-described manufacturing apparatus shown in FIG. 1, and the following description exemplifies the case where the method of the present invention is carried out in the manufacturing apparatus of FIG.
[0024]
In the method of the present invention, the thermoplastic resin is preferably a polystyrene resin. The styrene resin mentioned here may be a homopolymer of a styrene monomer or a copolymer of a styrene monomer and another monomer. Styrene-based monomers include styrene, methylstyrene, dimethylstyrene, chlorostyrene and the like. Examples of the monomer other than the styrene-based monomer include acrylic acid, methacrylic acid, esters thereof, acrylonitrile, maleic anhydride, butadiene, isoprene, chloroprene, and the like.
[0025]
The raw material monomer is sent to a polymerization section 11 through a monomer supply line 14, and is subjected to bulk polymerization in the polymerization section 11. The liquid containing the resin and the monomer removed from the polymerization section 11 is sent to the degassing section 12 through the line 15. In the degassing section 12, volatile components such as monomers in the liquid and the thermoplastic resin are separated, and the thermoplastic resin remains in a molten state through the line 16 and the resin supply line 25 to the extruder 21 of the extrusion cutting process unit 20. Supplied. On the other hand, the volatile matter such as the monomer separated in the degassing section 11 is sent in a gaseous state to a monomer recovery section 13 through a line 17, and the monomer is separated and recovered by a cooling condenser. The recovered monomer is sent to the monomer supply line 14 through the line 18 and used as a raw material monomer.
[0026]
The bulk polymerization conditions here are such that the polystyrene-based resin supplied to the extruder 21 has the following conditions a and b:
a. Weight average molecular weight Mw is in the range of 150,000 to 400,000, preferably in the range of 200,000 to 350,000,
b. Volatile content is 1000 ppm or less,
It is preferable that the above condition be satisfied. More preferably, the polymerization conversion is 95% or more, and the volatile matter content is 500 ppm or less.
[0027]
If the weight average molecular weight Mw is lower than the above range, the molecular weight of the polystyrene resin constituting the expandable thermoplastic resin particles 40 obtained becomes low, and a foamed resin molded product having good mechanical strength cannot be obtained. The polystyrene-based resin supplied to the extruder 21 is deteriorated by being subjected to shearing or the like in the extruder 21, so that the weight-average molecular weight Mw of the resin after extrusion tends to be lower than that of the resin before extrusion. is there. Therefore, it is desirable that the weight average molecular weight Mw of the polystyrene resin produced in the bulk polymerization process section 10 be set higher than the lower limit of the suitable weight average molecular weight Mw of the expandable thermoplastic resin particles 40.
On the other hand, if the weight average molecular weight Mw is higher than the above range, the viscosity of the obtained thermoplastic resin becomes high, and there is a problem that it is difficult to transfer in a molten state.
The weight average molecular weight Mw is measured by gel permeation chromatography (GPC). That is, about 30 mg of a sample is dissolved in 10 ml of chloroform, filtered through a 0.45 μm chromato disk, and then measured as follows.
Measuring device: Waters, HPLC (Detector 484, Pump 510)
Column: μStyragel 10, manufactured by Waters ³ +10 ⁴ +10 ⁵ +10 ⁶ A
Measurement conditions: column temperature (40 ° C.), mobile phase (chloroform), mobile phase flow rate (1.2 ml / min), injection / pump temperature (room temperature), measurement time (60 min), detection (UV254), injection volume (50 μl) )
Standard polystyrene for calibration curve:
Showa Denko KK (Shodes) molecular weight 1,030,000 and Tosoh Corporation molecular weight 5,840,000, 3,840,000, 355,000, 96,400, 37,900, 9,100, 2,630 and 495
In order to further improve the reproducibility after the device was stabilized, the weight average molecular weight Mw was determined by using the measured values of the fourth and subsequent times without using the first three measured values.
[0028]
When the volatile content is 1000 ppm or more, a foamed resin molded article having good mechanical strength cannot be obtained, and the monomer content in the foamed resin molded article increases, which may cause a problem such as an increase in the amount of eluted monomer. is there. In order to reduce the volatile content in the molten resin 19, it is desirable to connect a multistage degassing tank in the degassing section 12 to perform a precise degassing process. In order to reduce the volatile content of the expandable thermoplastic resin particles 40, a degassing section is provided in the extruder 21, and the volatile content is removed from the resin before the blowing agent is injected in the degassing section. Can also be configured.
The volatile content (ppm) is measured based on the Food Sanitation Law (Ministry of Health and Welfare Notification No. 98, polystyrene material test). That is, 1 g of a sample is precisely weighed, dissolved in dimethylformamide (DNF), 1 ml of a 0.1 vol% cyclopentanol DNF solution (internal standard solution) is added, and further diluted with DNF to a constant volume of 20 ml to obtain a measurement sample solution. This is measured as follows.
Measuring device: Shimadzu Corporation, gas chromatograph GC-14A (Detector: FID)
Column: PEG-20MPT (25% UniportB (60/80) 2 m) manufactured by GL Sciences Inc.
Measurement conditions: column temperature (105 ° C.), carrier gas (nitrogen), carrier gas flow rate (50 ml / min), inlet temperature (220 ° C.), detector temperature (220 ° C.), injection amount (3 μl)
Five types of volatile components such as toluene, ethylbenzene, isopropylbenzene, n-propylbenzene and styrene were measured, and the volatile component content (ppm) was calculated from the total amount of these components.
[0029]
Further, when the polymerization conversion is less than 95%, a foamed resin molded product having good mechanical strength cannot be obtained. In the present invention, since the molten resin 19 produced in the bulk polymerization process section 10 is directly supplied to the extruder 21, the polymerization reaction does not proceed in the extruder 21, and the extruder 21 is almost completely, preferably. It is desirable to supply the extruder 21 with the molten resin 19 which has been completely polymerized (that is, the polymerization conversion rate is close to 100%).
The polymerization conversion (%) was determined by measuring the residual styrene concentration (% by mass) and calculating (100−residual styrene concentration (% by mass)). The residual styrene concentration (% by mass) is a value obtained by measuring the amount of styrene using the above-described method for measuring the content of volatile components and expressing the result as a percentage by mass.
[0030]
The molten resin 19 is supplied to the extruder 21 through the resin supply line 25 at a melting temperature range, preferably at about 210 to 220 ° C. A resin supply line 25, a second resin supply line 29, and a blowing agent supply line 26 are sequentially connected to the extruder 21 from upstream to downstream in the resin flow direction F, and the extruder 21 is used for blending a polystyrene resin with a polystyrene resin. When mixing the resin, the blending resin in a molten state is supplied to the extruder 21 from the second extruder 24, kneaded with the polystyrene resin, and sent to the downstream side in the resin flow direction F. As the resin for blending, various thermoplastic resins such as polystyrene resin and polyethylene resin can be used, and additives such as coloring agent are kneaded in advance with the resin for blending to uniformly dissolve or disperse. You can keep it.
[0031]
Examples of the additives that can be used in the present invention include colorants such as pigments, bubble nucleating agents, bubble regulators, ultraviolet stabilizers, antistatic agents, and flame retardants. As the cell nucleating agent, it is preferable to use talc, particularly fine powder talc, calcium carbonate, silica and the like. It is preferable to use about 0.5 to 2.0 parts by mass of talc based on 100 parts by mass of the total resin. Note that these additives can be supplied into the extruder 21 through an additive supply line provided separately.
[0032]
The foaming agent is injected into the resin that moves in the extruder 21 toward the downstream in the resin flow direction F and reaches the connecting position of the foaming agent supply line 26.
Foaming agents suitable for foaming polystyrene resins are roughly classified into hydrocarbons and ethers, and among them, gaseous or liquid organic compounds at room temperature and normal pressure are suitable. Examples of the hydrocarbons include propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, hexane, and petroleum ether. Examples of ethers include those having a low boiling point such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether. In addition, inorganic gases such as carbon dioxide and nitrogen can be used. These foaming agents can be used alone or in combination of two or more. Among these, n-pentane, isopentane, n-butane and isobutane are particularly preferred.
The amount of the foaming agent used varies depending on the type of the foaming agent and the ratio at which foaming is to be performed, but is usually 1 to 20 parts by mass, preferably about 2 to 10 parts by mass with respect to 100 parts by mass of the whole resin.
[0033]
After the injection of the foaming agent, the foaming agent-containing resin sent to the end of the extruder 21 in the resin flow direction F is extruded in a strand form from a hole of a die 22 connected to the extruder 21. In the method of the present invention, it is necessary to prevent the extruded resin containing a foaming agent from foaming. To this end, the resin extruded from the die 22 is extruded into a pressurized liquid, preferably water, and the resin is cooled at the same time as the extrusion, or is extruded once into a gas, preferably into the atmosphere, and is immediately introduced into the water after the extrusion. It is necessary to cool the resin.
[0034]
In the method of the present invention, as a method of cutting the strand extruded from the die 22, any of a cold cut method and a hot cut method can be used, and the hot cut method is preferably used. When using the hot-cut method, the rotating blade of the cutter 23 is arranged near the die 22, and the foaming agent-containing resin that is extruded in a strand shape from the hole of the die 22 is continuously cut into particles by the rotating blade. Is preferred. In this case, the obtained resin particles have a rounded corner and are easy to handle. In addition, after the foaming, the fusion between the particles becomes good, and a foamed resin molded article having good mechanical properties can be obtained.
[0035]
The expandable thermoplastic resin particles 40 cut into particles by the cutter 23 and cooled by the circulating water are supplied to the dehydrator 34 through the line 33 together with the circulating water.
After being separated from circulating water by a dehydrator 34 and dewatered and dried by blast drying and the like, the expandable thermoplastic resin particles 40 are classified by a classifier 35, and particles having a desired particle size distribution range are collected in a particle receiving portion 36. The particles are stored in the particle storage 37. Thereafter, the stored expandable thermoplastic resin particles 40 are weighed and filled in an appropriate container, and are packaged as necessary to produce a product.
[0036]
The method of the present invention is configured such that the thermoplastic resin is supplied to the extruder 21 in a molten state by bulk polymerization, the foaming agent is mixed therein, and the extruder is extruded and cut from the die 22 to form the expandable thermoplastic resin particles 40. Therefore, a large amount of aqueous medium, which is a problem in the suspension polymerization method, is unnecessary, and wastewater treatment equipment required for wastewater treatment of the aqueous medium is not required, so that installation cost and operation cost of the wastewater treatment equipment can be reduced. . Further, since the expandable thermoplastic resin particles can be efficiently and continuously produced, the production cost is reduced.
Furthermore, compared to the method of introducing solid resin pellets into an extruder, re-melting and injecting and mixing a foaming agent to produce expandable thermoplastic resin particles, there is no energy loss required for re-melting, and energy costs are reduced. be able to. Therefore, according to the present invention, the expandable thermoplastic resin particles 40 can be manufactured at low cost.
[0037]
The foamable thermoplastic resin particles 40 thus manufactured are pre-foamed by heating in a free space, and the pre-foamed particles are put into the cavity of a mold having a cavity of a desired shape, and steam-heated. After the pre-expanded particles are fused together, they can be released and used to produce a foamed resin molded product having a desired shape.
Since the expandable thermoplastic resin particles 40 according to the present invention are manufactured by the above-described method of the present invention, it is possible to manufacture a foamed resin molded article having excellent mechanical strength, and it is inexpensive.
[0038]
【The invention's effect】
In the present invention, the thermoplastic resin produced by bulk polymerization is supplied to an extruder in a molten state, a foaming agent is mixed therein, and the composition is extruded from a die and cut to form foamable thermoplastic resin particles. A large amount of aqueous medium, which is a problem in the turbid polymerization method, is not required, and a wastewater treatment facility required for wastewater treatment of the aqueous medium is not required, so that installation cost and operation cost of the wastewater treatment facility can be reduced. Further, since the expandable thermoplastic resin particles can be efficiently and continuously produced, the production cost is reduced. Furthermore, compared to the method of introducing solid resin pellets into an extruder, re-melting and injecting and mixing a foaming agent to produce expandable thermoplastic resin particles, there is no energy loss required for re-melting, and energy costs are reduced. be able to. Therefore, according to the present invention, expandable thermoplastic resin particles can be produced at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing one embodiment of an apparatus for producing expandable thermoplastic resin particles of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Lump polymerization process part, 11 ... Polymerization section, 12 ... Deaeration section, 13 ... Monomer recovery part, 14 ... Monomer supply line, 15-18 ... Line, 19 ... Molten resin (thermoplastic resin in a molten state), 20 ... Extrusion cutting process part, 21 ... Extruder, 22 ... Die, 23 ... Cutter, 24 ... Second extruder, 25 ... Resin supply line, 26 ... Blowing agent supply line, 27 ... Blowing agent tank, 28 ... Supply machine 29, a second resin supply line, 30: a blow-down section, 31: a resin storage section for blending, 32-33 ... a line, 34 ... a dehydrator, 35 ... a classifier, 36 ... a particle receiving section, 37 ... a particle storage Part, 38 ... line, 40 ... foamable thermoplastic resin particles.

Claims (24)

A polymerization section for producing a thermoplastic resin by bulk polymerization of raw material monomers, and a degassing section for removing volatile components from the obtained thermoplastic resin, and a bulk polymerization process section for producing a thermoplastic resin by a bulk polymerization method When,
A resin supply line and a blowing agent supply line to which a thermoplastic resin in a molten state is supplied from the degassing section of the bulk polymerization process section are sequentially connected from upstream to downstream in the resin flow direction, and from the die at the terminal in the resin flow direction. An apparatus for producing expandable thermoplastic resin particles, comprising: an extruder that extrudes a blowing agent-containing resin; and an extrusion cutting process unit having a cutter that cuts the foaming agent-containing resin extruded from the die into granules. . The apparatus for producing expandable thermoplastic resin particles according to claim 1, further comprising a second extruder that supplies a resin for blending to the extruder, between the resin supply line and the blowing agent supply line of the extruder. . The apparatus for producing expandable thermoplastic resin particles according to claim 2, wherein the blending resin is supplied to the extruder in a molten state. The production of expandable thermoplastic resin particles according to claim 2 or 3, further comprising an additive supply line between the resin supply line and the blowing agent supply line of the extruder or connected to the second extruder. apparatus. The apparatus for producing expandable thermoplastic resin particles according to any one of claims 1 to 4, wherein the extruder is a twin-screw extruder. The foaming heat according to any one of claims 1 to 5, further comprising a degassing unit for removing volatile components in the resin in the extruder, on the upstream side of the extruder in the direction of resin flow from a connection position of a foaming agent supply line. Equipment for manufacturing plastic resin particles. The expandable thermoplastic resin particles according to any one of claims 1 to 6, further comprising a cooling unit configured to cool the resin in the extruder, at a position where the extruder is connected to the blowing agent supply line or at a position downstream of the position in the resin flow direction. Manufacturing equipment. The apparatus for producing expandable thermoplastic resin particles according to any one of claims 5 to 7, wherein the extruder has a gear pump for increasing pressure. The apparatus for producing expandable thermoplastic resin particles according to any one of claims 1 to 8, wherein the resin supply line has a blow-down section for extracting a resin in a molten state supplied through the line. The apparatus for producing expandable thermoplastic resin particles according to any one of claims 1 to 9, wherein the thermoplastic resin is a polystyrene resin. (A) a step of producing a thermoplastic resin by bulk polymerization of the raw material monomers to produce a thermoplastic resin, and removing volatile components from the obtained thermoplastic resin;
(B) The thermoplastic resin is supplied to the extruder in a molten state, and a foaming agent is injected into the thermoplastic resin while moving the resin toward the die at the end of the extruder in the resin flow direction. Forming,
(C) cutting the foaming agent-containing resin extruded from the die into granules to produce foamable thermoplastic resin particles. The method for producing expandable thermoplastic resin particles according to claim 11, wherein the extruder in the step (B) is a twin-screw extruder. In the step (C), the blowing agent-containing resin extruded into the cooling liquid in the form of a strand from the hole of the die is extruded and cut into granules at the same time, and is cooled by contact with the liquid to suppress foaming. The method for producing expandable thermoplastic resin particles according to claim 11, wherein the method is a step of producing expandable thermoplastic resin particles by performing the process. The method for producing expandable thermoplastic resin particles according to any one of claims 11 to 13, wherein the thermoplastic resin is a polystyrene resin. The polystyrene resin supplied to the extruder has the following conditions a and b:
a. The weight average molecular weight Mw is in the range of 150,000 to 400,000,
b. The volatile matter content is 1000 ppm or less;
The method for producing expandable thermoplastic resin particles according to claim 14, which satisfies the following. The method for producing expandable thermoplastic resin particles according to claim 15, wherein the polystyrene-based resin supplied to the extruder has a polymerization conversion of 95% or more. The method for producing expandable thermoplastic resin particles according to claim 15 or 16, wherein the polystyrene resin has a weight average molecular weight of 200,000 to 350,000. The method for producing expandable thermoplastic resin particles according to any one of claims 15 to 17, wherein the polystyrene resin has a volatile content of 500 ppm or less. The method for producing expandable thermoplastic resin particles according to any one of claims 11 to 18, wherein in the step (B), a resin for blending is mixed before a blowing agent is injected into the thermoplastic resin in the extruder. The method for producing expandable thermoplastic resin particles according to claim 19, wherein the resin for blending is supplied into the extruder in a molten state. The method for producing expandable thermoplastic resin particles according to claim 19 or 20, wherein in the step (B), an additive is mixed with the thermoplastic resin in the extruder or the blending resin. The method for producing expandable thermoplastic resin particles according to any one of claims 11 to 21, wherein in the step (B), the thermoplastic resin in the extruder is subjected to a degassing treatment. The foamable thermoplastic resin according to any one of claims 11 to 22, further comprising a step of extracting a part of the thermoplastic resin in a molten state to be supplied from the step (A) to the step (B) to produce resin pellets. Method for producing particles. An expandable thermoplastic resin particle produced by the method for producing an expandable thermoplastic resin particle according to any one of claims 11 to 23.

Images