JP2018158981A - Method for producing foamable thermoplastic resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a method for producing a foamable thermoplastic resin particle that allows stable operation of a production line.SOLUTION: A method for producing a foamable thermoplastic resin particle includes a dehydration step for dehydrating resin particles, a spraying step for spraying an antistatic agent to the resin particles with a moisture content 5-500 wt. ppm after the dehydration step, and an addition step for adding a blocking inhibitor to the resin particles after the spraying step.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing expandable thermoplastic resin particles.

  When the expandable resin particles are obtained by the melt extrusion method, it is necessary to take measures for preventing electrostatic ignition between the dehydration step and the surface treatment step. For example, Patent Document 1 discloses that a moisturizing agent and a surfactant are essential components before a product is produced by performing a surface treatment process for coating a foaming thermoplastic resin particle made of a styrene resin with a surface treatment agent. A technique for spraying an antistatic agent containing it onto expandable thermoplastic resin particles is disclosed.

JP 2006-206753 A

  In the above-described conventional technology, it is necessary to attach both the moisturizing agent and the surfactant to the expandable thermoplastic resin particles, which increases the cost. In addition, when the humectant and the surfactant are not uniformly attached, the antistatic effect may be insufficient, and there remains room for improvement in the method for producing expandable thermoplastic resin particles. The present inventor has found out.

  An object of one embodiment of the present invention is to realize a method for producing expandable thermoplastic resin particles capable of stably operating a production line by efficient spraying of an antistatic agent.

  In order to solve the above-mentioned problems, a method for producing expandable thermoplastic resin particles according to one aspect of the present invention is to produce resin particles by extruding a molten resin containing a thermoplastic resin and a foaming agent through a die in pressurized water. A method for producing granulated foamable thermoplastic resin particles, a dehydration step for dehydrating the resin particles, and a spraying step for spraying an antistatic agent to resin particles having a moisture content of 5 to 500 ppm by weight after the dehydration step And an addition step of adding an anti-blocking agent to the resin particles after the spraying step.

  According to one aspect of the present invention, the production line can be stably operated by the efficient spraying of the antistatic agent.

  An embodiment of the present invention will be described below, but the present invention is not limited to this. Unless otherwise specified in this specification, “A to B” representing a numerical range is intended to be “A or more (including A and greater than A) and B or less (including B and less than B)”.

[1. (Raw material of foamable thermoplastic resin particles)
First, raw materials for expandable thermoplastic resin particles, that is, raw materials used in the method for manufacturing expandable thermoplastic resin particles according to an embodiment of the present invention (hereinafter also referred to as the present manufacturing method) will be described. In the present specification, the expandable thermoplastic resin particles are also simply referred to as resin particles. In this production method, a thermoplastic resin, a foaming agent, an antistatic agent and an antiblocking agent, and optionally other additives can be used.

<1-1. Thermoplastic resin>
Examples of the thermoplastic resin include styrene resins, vinyl resins, polyolefin resins, polyamide resins, polyester resins, and engineering plastics. Among them, the thermoplastic resin is preferably a styrene resin because it is inexpensive and easy to foam. The styrenic resin may be copolymerized with not only a styrene homopolymer (polystyrene homopolymer) but also other monomers copolymerizable with styrene or derivatives thereof within a range not impairing the effects of the present embodiment. Good.

  Examples of other monomers copolymerizable with styrene or derivatives thereof include, for example, styrene derivatives, polyfunctional vinyl compounds, (meth) acrylic acid ester compounds, vinyl cyanide compounds, diene compounds and derivatives thereof, and unsaturated compounds. Examples thereof include carboxylic acid anhydrides and N-alkyl-substituted maleimide compounds. These may be used alone or in combination of two or more.

  For example, examples of the styrene derivative include methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, and trichlorostyrene. Examples of the polyfunctional vinyl compound include divinylbenzene. Examples of the (meth) acrylic acid ester compound include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate and butyl methacrylate. Examples of the vinyl cyanide compound include (meth) acrylonitrile. Examples of the diene compound include butadiene. Examples of the unsaturated carboxylic acid anhydride include maleic anhydride and itaconic anhydride. N-alkyl substituted maleimide compounds include N-methylmaleimide, N-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2) -chlorophenylmaleimide, N- (4) -bromophenylmaleimide and N- (1) -Naphthylmaleimide and the like.

  The styrenic resin may be a homopolymer of the above-mentioned other monomer or derivative, or a blend with the copolymer as long as the effects of the present embodiment are not impaired. For example, diene rubber reinforced polystyrene, acrylic rubber reinforced polystyrene and / or polyphenylene ether resin can be blended with the styrene resin.

<1-2. Foaming agent>
Although the said foaming agent is not specifically limited, A C4-C5 hydrocarbon is desirable. If it is a C4-C5 hydrocarbon, sufficient foaming power will be easy to be obtained and it will become easy to be highly foamed. As the hydrocarbon having 4 to 5 carbon atoms, butane or pentane is preferable. For example, normal butane, isobutane, etc. are mentioned as butane. Examples of pentane include normal pentane, isopentane, neopentane, and cyclopentane. These may be used individually by 1 type and may be used in combination of 2 or more type. That is, the foaming agent may contain butane and / or pentane.

<1-3. Antistatic agent>
The antistatic agent is not particularly limited as long as it can impart low electrical resistance to the foamable thermoplastic resin particles, but a surfactant is preferable from the viewpoint of excellent antistatic effect.

  As the surfactant, one or more selected from anionic surfactants, cationic surfactants and nonionic surfactants can be used.

  Examples of the anionic surfactant include alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates and alkyl diallyl ether sulfonates.

  Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts. More specifically, N-hydroxyethyl (2-hydroxyalkyl) amine is mentioned.

  Examples of nonionic surfactants include polyethylene glycol, alkyl betaines, amine oxides, imidazolinium betaines, and alkyl glycines.

  These surfactants are preferably used in a state of being dissolved in an appropriate solvent such as water or alcohol, preferably water.

<1-4. Anti-blocking agent>
Examples of the anti-blocking agent include higher fatty acid esters of polyhydric alcohols, higher fatty acid amides, inorganic salts and metal soaps. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the higher fatty acid ester of the polyhydric alcohol include esters of a saturated aliphatic carboxylic acid or unsaturated carboxylic acid having 12 to 22 carbon atoms and a polyhydric alcohol. Examples of the saturated aliphatic carboxylic acid include lauric acid, stearic acid, hydroxystearic acid, and behenic acid. Examples of the unsaturated carboxylic acid include oleic acid, erucic acid, and linoleic acid. Examples of the polyhydric alcohol include glycerin, sorbitan, pentaerythritol and the like.

  Examples of the higher fatty acid amide include the above-mentioned saturated aliphatic carboxylic acid or unsaturated carboxylic acid amide. Examples of inorganic salts include calcium carbonate and magnesium carbonate. Examples of the metal soap include zinc stearate, magnesium stearate, and calcium stearate.

<1-5. Other additives>
In this production method, for example, other additives such as a flame retardant, a flame retardant aid, a radiant heat transfer inhibitor, a heat stabilizer and a nucleating agent may be used.

  Examples of the flame retardant include bromine-based flame retardant, phosphorus-based flame retardant, nitrogen-based flame retardant, silicon-based flame retardant, and hydrated metal-based flame retardant. Among them, a brominated flame retardant having a high flame retardancy imparting effect is desirable.

  Examples of the flame retardant aid include a radical generator and a metal compound. In particular, when a brominated flame retardant is used, a radical generator is preferably used. The radical generator is decomposed by heat to generate radicals.

  Examples of the radiation heat transfer inhibitor include graphite, graphene, activated carbon, carbon black, titanium oxide, and metal aluminum. Among these, at least one compound selected from the group consisting of graphite, graphene, activated carbon, carbon black and titanium oxide is preferable from the viewpoint of improving the heat insulating property of the in-mold foam molded body obtained from the resin particles, and graphite is more preferable. preferable.

  As the heat stabilizer, a hindered amine compound, a phosphorus compound, or an epoxy compound is desirable because the 1% weight reduction temperature in the thermogravimetric analysis of the brominated flame retardant-containing mixture can be arbitrarily controlled. By using a heat stabilizer in combination, it is possible to suppress deterioration of flame retardancy and degradation of expandable thermoplastic resin particles due to decomposition of the brominated flame retardant in the production process.

  Examples of the nucleating agent include inorganic compounds, polymer compounds, olefin waxes, and fatty acid bisamides.

[2. Method for producing expandable thermoplastic resin particles]
This production method is a method for producing expandable thermoplastic resin particles by extruding a molten resin containing a thermoplastic resin and a foaming agent through a die in pressurized water, and granulating the resin particles, wherein the resin particles are dehydrated. A dehydration step, a spraying step of spraying an antistatic agent on resin particles having a moisture content of 5 to 500 ppm by weight after the dehydration step, an addition step of adding an antiblocking agent to the resin particles after the spraying step, including.

  In the method described in the example of Patent Document 1, since there is no moisture adhering to the surface of the expandable thermoplastic resin particles before attachment of the antistatic agent, the surfactant alone is not uniformly applied to the surface of the resin particles. The inventors of the present application have found that it is difficult to achieve the effect.

  Therefore, the inventor of the present application diligently studied a method of applying an antistatic agent that can stably exhibit antistatic performance. As a result, it was found that the antistatic performance can be stably exhibited by controlling the water content of the expandable thermoplastic resin particles after the dehydration step. As a result, it has been found that the production line can be stably operated in the sieving step and the surface treatment step after the spraying of the antistatic agent, and one embodiment of the present invention has been completed.

  Further, the inventor of the present application has further researched and developed, and with such foamable thermoplastic resin particles, it is possible to significantly prevent charging due to contact with the wall surface of piping and the like and electrostatic charging between resin particles. It was found that sex can be secured. At the same time, it has also been found that the amount of the antistatic agent used can be reduced.

  Each step that can be included in the manufacturing method will be described below. In addition, [1. For the items already described in [Raw Material of Expandable Thermoplastic Resin Particles], the description is omitted below and the above description is incorporated as appropriate.

<2-1. Extrusion process>
This production method includes a step of extruding a molten resin containing a thermoplastic resin and a foaming agent through a die in pressurized water to granulate resin particles.

  In this step, for example, an apparatus in which an extruder, a channel pipe, and a die are continuously connected can be employed. First, a thermoplastic resin is put into an extruder and melted at a resin temperature of, for example, 100 ° C. or more and 300 ° C. or less. From the viewpoint of suppressing the decomposition of the thermoplastic resin, it is preferable to melt the thermoplastic resin at a resin temperature of 110 ° C. or higher and 250 ° C. or lower. Note that additives other than the above-described thermoplastic resin may be added to the extruder according to the type and characteristics of the foamable thermoplastic resin particles to be produced. In this case, it is possible to add other additives at the same time as the thermoplastic resin by putting the additive previously blended with the thermoplastic resin into the extruder. Alternatively, an addition port different from the hopper for charging the thermoplastic resin into the extruder may be provided, and other additives may be charged into the extruder through this addition port.

  The extruder can be appropriately selected from conventionally known extruders depending on the type of thermoplastic resin to be granulated, and examples thereof include an extruder using a screw. As an extruder using a screw, for example, a single screw extruder or a twin screw extruder can be adopted. The screw rotation direction when the twin-screw extruder is employed may be the same direction or different directions. Two or more extruders may be used. For example, a tandem configuration in which two extruders are connected in series may be used.

  When one extruder is provided, there is an advantage that it is easy to suppress the residence time of the molten resin in a short time and to easily suppress deterioration of the molten resin. On the other hand, when two or more extruders are provided, there is an advantage that the molten resin and other additives are easily mixed more uniformly. Considering this, the configuration of the extruder can be determined.

  In addition, molten resin will flow toward a die | dye by extrusion with an extruder. From such a flow of molten resin, in the extruder and the die, the side on which the molten resin is discharged is the downstream side, and the opposite side is the upstream side.

  In addition, when adopting a tandem configuration using two extruders, it is preferable to adopt a configuration of a single screw extruder-single screw extruder or a twin screw extruder-single screw extruder, The configuration of a twin screw extruder—single screw extruder employing a twin screw extruder is more preferable. In this case, the raw material supply to the extruder is stable, the foaming agent and other additives are easily dispersed evenly, and the flame retardancy of the obtained thermoplastic resin in-mold foamed molded product is stable and highly easily developed. Moreover, in this case, the flame retardance level for each test piece cut out from one thermoplastic resin in-mold foam molded product tends to be stable.

  The foaming agent may be added directly to the extruder, or may be added in a channel pipe connected downstream of the extruder. When the foaming agent is added directly to the extruder, the thermoplastic resin is easily plasticized in the extruder, so the resin temperature in the extruder can be lowered, and the thermoplastic resin can be decomposed or other additives. It becomes easy to suppress decomposition | disassembly. Alternatively, there is a case where an operation of lowering the resin temperature to a predetermined temperature before adding other additives may be employed. In this case, there is also an advantage that it is easy to cool to the predetermined temperature. Moreover, since the operation | movement which made the screw torque of an extruder low can be performed, there also exists an advantage that consumption of extruder components, such as a screw, cannot advance easily that power consumption can be suppressed.

  On the other hand, when the foaming agent is added in the flow passage pipe connected downstream of the extruder, the added foaming agent does not backflow (out of gas) from the extruder raw material addition port (the hopper or another addition port). It is easy to be stably contained in the thermoplastic resin. As a result, variation in the content of the foaming agent contained in the obtained individual foamable thermoplastic resin particles is reduced.

  The foaming agent can be press-fitted with a conventionally known press-fitting pump or the like, and the temperature can be controlled by heating or cooling in advance if necessary.

  The flow path piping downstream from the extruder may have any configuration, but preferably includes at least one member of a static mixer, a static cooler, and a gear pump. The static mixer is useful for uniformly mixing the molten resin. The static cooler is useful for cooling the molten resin to a predetermined temperature. When both the static mixer and the static cooler are employed, the molten resin is mixed and cooled by the mixing function by the static mixer and the cooling function by the static cooler.

  The gear pump is a useful member for maintaining the pressure of the molten resin flow or for appropriately increasing the pressure. When a gear pump is provided in the flow path piping from the extruder to the die, it is easy to maintain the pressure of the molten resin in the flow path, and a stable discharge amount can be realized.

  For example, a static mixer, a static cooler, or an integrated static mixer and static cooler can be obtained from SULZER, FLUITEC, or STAMIXCO. The gear pump can be obtained from PSI-POLYMER SYSTEM, EXTRUSION AUXILARY SERVICES, or the like.

  A molten resin containing a thermoplastic resin and a foaming agent is melt-kneaded in an extruder and then extruded into pressurized water through a die. The molten resin extruded in pressurized water is cut by a cutting device to granulate resin particles. As the cutting device, for example, a rotary cutter that contacts the die lip can be used.

<2-2. Dehydration process>
The dehydration step is a step of dehydrating the resin particles. This step can be performed in a dewatering unit connected to the die by piping. A centrifugal dehydrator or the like can be used for the dehydrating unit.

  The resin particles after the dehydration step preferably have a water content of 5 to 500 ppm by weight, more preferably 10 to 250 ppm by weight with respect to the resin particles. The water content can be measured by the method described in the examples described later.

  If the amount of water is 5 ppm by weight or more, the antistatic agent is uniformly applied, so that the antistatic effect can be exhibited stably. Although the detailed cause is not clear, when there is no moisture on the surface of the foamable thermoplastic resin particles, the antistatic agent is uniformly on the surface of the resin particles due to the wettability of the foamable thermoplastic resin particles with the antistatic agent solution. It is estimated that it will not be applied. In addition, when the expandable thermoplastic resin particles before attachment have too much water, the antistatic agent tends to flow with the water and is not applied to the surface of the expandable thermoplastic resin particles.

  In the technique described in Patent Document 1, antistatic performance cannot be expressed without both a moisturizing agent and a surfactant. This is considered to be because the water content of the expandable thermoplastic resin particles before attaching them was too small or too large. If the moisture content before attaching the antistatic agent is adjusted to the claim range, the required performance can be achieved only by attaching a small amount of the antistatic agent.

<2-3. Spraying process>
The spraying step is a step of spraying the antistatic agent onto the resin particles having a water content of 5 to 500 ppm by weight after the dehydration step. A preferable range of the spray amount of the antistatic agent is 10 to 200 ppm by weight. If the sprayed antistatic agent is 10 ppm by weight or more, it is easy to prevent electrostatic ignition in the subsequent process. Moreover, if the sprayed antistatic agent is 200 ppm by weight or less, it is preferable because the amount of the antistatic agent used can be suppressed and the resin particles can be easily dried after spraying. The antistatic agent to be sprayed is more preferably 30 to 150 ppm by weight, and further preferably 50 to 100 ppm by weight.

  The antistatic agent sprayed in the spraying process is not intended to improve the antistatic performance of the foamable thermoplastic resin particles as the final product. That is, it is not intended for antistatic in the step of pre-foaming using the obtained foamable thermoplastic resin particles. The purpose is merely to prevent electrostatic ignition (for example, electrostatic ignition in the piping) in the manufacturing process of the foamable thermoplastic resin particles. Therefore, a relatively small amount of the antistatic agent sprayed in the spraying process is sufficient.

  The spraying step is performed, for example, by coating the surface of the foamable thermoplastic resin particles with an antistatic agent using a spray device or the like. Spraying with a spray device is preferable because it can continuously and uniformly coat the antistatic agent.

  In the spraying step, it is preferable to spray the antistatic agent toward the outlet of the resin particles in the dehydrating part used in the dehydrating step. Accordingly, there is an advantage that the contact between the foamable thermoplastic resin particles and the pipe or the like at the stage where the antistatic agent is not applied can be reduced as much as possible.

<2-4. Addition process>
The adding step is a step of adding an antiblocking agent to the resin particles after the spraying step. Thereby, it can prevent more that resin particles adhere | attach and lump in a post process. The addition process is also referred to as a surface treatment process.

  The adding step is performed, for example, by coating the surface of the foamable thermoplastic resin particles with an anti-blocking agent using a mixer or the like.

  The amount of the anti-blocking agent added is preferably 0.01 to 0.2% by weight, more preferably 0.02 to 0.15% by weight, based on 100% by weight of the resin particles. If the addition amount of the anti-blocking agent is 0.01% by weight or more, it is possible to sufficiently prevent the resin particles from adhering to each other at the time of preliminary foaming. Moreover, if the addition amount of an antiblocking agent is 0.2 weight% or less, since the usage-amount of an antiblocking agent can be suppressed and adhesion | attachment of resin particles is easy at the time of shaping | molding, it is preferable.

  Moreover, you may apply | coat an antistatic agent with respect to the resin particle after the said spraying process simultaneously with the addition process, or the resin particle after the said addition process. Thereby, electrification can be prevented also in the process of carrying out preliminary foaming using the obtained foamable thermoplastic resin particles. In this case, the application amount of the antistatic agent is preferably 0.3 to 3% by weight and more preferably 0.5 to 2% by weight with respect to 100% by weight of the resin particles. If the application amount of the antistatic agent is 0.3% by weight or more, charging of the resin particles can be sufficiently prevented even in the steps after the preliminary foaming. Moreover, if the application amount of the antistatic agent is 3% by weight or less, the use amount of the antistatic agent can be suppressed, and drying after preliminary foaming is easy, which is preferable.

<2-5. Drying process>
The production method preferably includes a drying step of drying the resin particles sprayed with the antistatic agent after the spraying step. Thereby, the solvent at the time of spraying the antistatic agent can be removed, and stable foreign particle removal in the sieving step described later can be carried out, which is preferable. In addition, a drying process may be performed after spraying an antistatic agent after the above-mentioned addition process or after the addition process.

  The drying process is performed using, for example, an apparatus capable of airflow drying. It is preferable that a drying process is performed at 30-60 degreeC, and it is more preferable to be performed at 35-55 degreeC. If the temperature of a drying process is 30 degreeC or more, a solvent can fully be removed. Moreover, if the temperature of a drying process is 60 degrees C or less, since it is suppressed that a foamable thermoplastic resin particle foams during drying, it is preferable.

<2-6. Sieve process>
The production method preferably includes a sieving step for classifying the resin particles. The sieving step can be performed using, for example, a known sieving machine. The sieving step is preferably after the spraying step from the viewpoint of suppressing charging. In addition, since the antistatic agent sprayed on the resin particles in the spraying process is relatively small as described above, the resin particles are less likely to be agglomerated in the sieving process. Moreover, it is preferable that a sieving process is before an addition process from a viewpoint of preventing that the antiblocking agent apply | coated at the addition process peels.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The method for producing expandable thermoplastic resin particles according to the first aspect of the present invention includes the steps of extruding a molten resin containing a thermoplastic resin and a foaming agent through a die in pressurized water, and granulating the resin particles. A dehydration step of dehydrating the resin particles, a spraying step of spraying an antistatic agent onto resin particles having a moisture content of 5 to 500 ppm by weight after the dehydration step, and a resin after the spraying step And an addition step of adding an antiblocking agent to the particles.

  In the method for producing expandable thermoplastic resin particles according to aspect 2 of the present invention, in aspect 1, the antistatic agent may be a surfactant.

  The method for producing expandable thermoplastic resin particles according to aspect 3 of the present invention includes, in aspect 1 or 2, a drying step of drying the resin particles sprayed with the antistatic agent after the spraying step. Also good.

  The method for producing expandable thermoplastic resin particles according to aspect 4 of the present invention is the method for producing foamed thermoplastic resin particles according to any one of aspects 1 to 3, wherein in the spraying step, the resin particle outlet in the dehydrating part used in the dehydrating step is used. An antistatic agent may be sprayed toward the surface.

  In any one of Embodiments 1 to 4, the method for producing expandable thermoplastic resin particles according to Embodiment 5 of the present invention may be such that the water content is 10 to 250 ppm by weight.

  The manufacturing method of the expandable thermoplastic resin particle which concerns on aspect 6 of this invention is sprayed with 10-200 weight ppm of antistatic agents in the said spraying process in any one of aspects 1-5. Good.

  The method for producing expandable thermoplastic resin particles according to Aspect 7 of the present invention, in any one of Aspects 1 to 6, with respect to the resin particles after the spraying step simultaneously with the addition step, or after the addition step An antistatic agent may be further applied to the resin particles.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[Measurement of water content]
The trace amount of water contained in the sample changes over time in the atmosphere in the air. Therefore, in order to measure the water content after the dehydration process, the foamable thermoplastic resin particles immediately after the dehydration process are sealed in a vial with a sealed stopper, and the water content inside the sealed vial is measured. There is a need to. Also, perform the same vial sealing work without collecting the sample at the same location where the sample was collected, measure the moisture content of the atmosphere, and subtract the moisture content of the sample by subtracting it from the moisture content at the time of sample collection. Can be measured.

  The equipment used for the measurement is shown below.

Moisture analyzer: Trace moisture analyzer CA-200 (coulometric method) manufactured by Mitsubishi Chemical Analytech
Moisture vaporizer: Mitsubishi Chemical Analitech moisture vaporizer VA-230 type Anolyte: Aquamicron AX
Catholyte: Aquamicron CXU
Vials: GL Siences 10 mL HS-iodine Cr-vial Tomei F-btm 20 mm
Cap: GL Sciences open top crimp cap S 20mm
Packing: 20 mm PTFE / Si septum manufactured by GL Sciences Sample collection was performed 1 hour after combining the rotational speed of the centrifugal dehydrator and the rotational speed of the centrifugal dehydrator exhaust blower with each numerical value.

  Measure the weight of the vial, cap and packing in advance. About 0.5 mg of foamable thermoplastic resin particles immediately after being discharged from the centrifugal dehydrator outlet is collected in a vial (sample collection amount varies depending on the amount of water), and immediately sealed with a packing and a cap. And

  Further, the foamable thermoplastic resin particles are sealed with a packing and a cap so as not to enter the vial bottle at the same place where the foamable thermoplastic resin particles are collected, thereby obtaining a blank vial.

  Remove any water droplets on the outside of the sealed vial, leave it in a constant temperature and humidity chamber at 23 ° C. and 50% humidity for 6 hours, and then measure the sample weight with an electronic balance.

  Next, a sealed vial was placed in a moisture vaporizer set at 150 ° C, and the moisture content was measured by the Karl Fischer method (coulometric method) after transferring the moisture in the vial to the moisture analyzer for 2 minutes. To do.

  Calculate the water content using the following formula.

Water content (ppm by weight) = (Water content in sample vial (mg) −Water content in blank vial (mg)) / Sample weight (mg) × 10,000
In order to reduce the measurement error when the amount of water is small, the amount of sample collected should be adjusted so that the amount of water in the sample vial (mg)-the amount of water in the blank vial (mg) is 0.1 mg or more. Good.

[Example 1]
[Preparation of expandable thermoplastic resin particles]
As a thermoplastic resin, 100 parts by weight of a polystyrene resin (PS Japan Co., Ltd., 680) was connected in series to the same-direction twin screw extruder (first extruder) and single screw extruder (second extruder). It was supplied to a tandem type two-stage extruder and melt kneaded. From the middle of the first extruder, 7 parts by weight of mixed pentane (normal pentane: isopentane = 80: 20 (weight ratio)) is press-fitted, and then the foaming agent-containing molten polystyrene resin is supplied to the second extruder through a continuous pipe. did.

  A blowing agent-containing molten polystyrene resin was extruded into pressurized circulating water from a die having a small hole attached to the downstream side of the second extruder. The extruded foaming agent-containing molten polystyrene resin was cut and pulverized using a rotary cutter having a blade in contact with a die and transferred to a centrifugal dehydrator [TVE1000ED manufactured by BKG Co., Ltd.] with circulating water. Dehydration was carried out with a centrifugal dehydrator rotating at 1700 rpm and a centrifugal dehydrator exhaust blower rotating at 2167 rpm.

  When the water content of the expandable polystyrene resin particles discharged from the outlet of the dehydrator was measured, it was 5.1 ppm by weight.

  A 7.5% aqueous solution of N-hydroxyethyl (2-hydroxyalkyl) amine as an antistatic agent was sprayed on the expandable polystyrene resin particles discharged from the dehydrator outlet. At this time, N-hydroxyethyl (2-hydroxyalkyl) amine was sprayed to 50 ppm by weight with respect to the expandable polystyrene resin particles discharged from the dehydrator outlet. The expandable polystyrene resin particles to which the antistatic agent was attached were dried with an air dryer.

  In a state where 300 g of expandable polystyrene resin particles to which the dried antistatic agent is attached is placed in a polyethylene bag (OK bag No. 15, manufactured by Okura Kogyo Co., Ltd.) and the mouth of the bag is opened, 23 ° C. And stored overnight in a constant temperature room with a humidity of 20%. After storage, it was shaken 100 times with the mouth of a polyethylene bag containing 300 g of expandable polystyrene resin particles bound. Thereafter, the mouth of the polyethylene bag was opened, and the amount of charge on the surface of the expandable polystyrene resin particles was measured three times or more with a static electricity measuring device (Statidon DX made by Cycido Static Electricity). As a result of calculating the average value, it was -0.5 kV (measurement distance 30 mm, charge amount measurement was performed in an atmosphere of 23 ° C. and relative humidity 20%).

[Examples 2 to 12 and Comparative Examples 1 to 7]
In Example 1, the antistatic agent was attached in the same manner as in Example 1 except that the dehydrator rotation speed, the dehydrator exhaust blower rotation speed, and the antistatic agent application amount were changed as shown in Tables 1 to 3. Expandable polystyrene resin particles were obtained. The charge amount of the obtained expandable polystyrene resin particles was measured in the same manner as in Example 1, and the results are shown in Tables 1 to 3. In Examples 1 to 12 and Comparative Examples 1 to 7, since the purpose is to measure the charge amount, the addition of an antiblocking agent is omitted.

  As can be seen from Tables 1 to 3, when the antistatic agent was sprayed onto the resin particles having a water content of 5 to 500 ppm by weight after the dehydration step, the charge amount could be efficiently suppressed.

  INDUSTRIAL APPLICATION This invention can be utilized for the manufacturing method of the expandable thermoplastic resin particle which can be operated stably.

Claims (7)

A method for producing foamable thermoplastic resin particles by extruding a molten resin containing a thermoplastic resin and a foaming agent through a die in pressurized water and granulating the resin particles,
A dehydration step of dehydrating the resin particles;
A spraying step of spraying an antistatic agent to resin particles having a water content of 5 to 500 ppm by weight after the dehydration step;
An addition step of adding an anti-blocking agent to the resin particles after the spraying step, and a method for producing expandable thermoplastic resin particles.   The method for producing expandable thermoplastic resin particles according to claim 1, wherein the antistatic agent is a surfactant.   The manufacturing method of the expandable thermoplastic resin particle of Claim 1 or 2 including the drying process of drying the said resin particle sprayed with the antistatic agent after the said spraying process.   The foamable thermoplastic resin particle according to any one of claims 1 to 3, wherein in the spraying step, an antistatic agent is sprayed toward an outlet of the resin particle in a dehydrating part used in the dehydrating step. Manufacturing method.   The method for producing expandable thermoplastic resin particles according to any one of claims 1 to 4, wherein the moisture content is 10 to 250 ppm by weight.   The method for producing expandable thermoplastic resin particles according to any one of claims 1 to 5, wherein 10 to 200 ppm by weight of an antistatic agent is sprayed in the spraying step.   The foaming heat according to any one of claims 1 to 6, wherein an antistatic agent is further applied to the resin particles after the spraying step simultaneously with the addition step or to the resin particles after the addition step. A method for producing plastic resin particles.