JP6043562B2 - Method for producing thermoplastic resin particles, method for producing foamable thermoplastic resin particles, method for producing pre-foamed particles, and method for producing foamed molded article - Google Patents

Description

  The present invention relates to thermoplastic resin particles such as polystyrene-based resin and a production method thereof, expandable thermoplastic resin particles and a production method thereof, pre-expanded particles obtained using the expandable thermoplastic resin particles, and a foam molded article. . The thermoplastic resin particles are suitably used as a seed (nucleus) material or the like when producing expandable thermoplastic resin particles by a seed polymerization method or the like.

Thermoplastic resin foam moldings such as polystyrene resin foam moldings are pre-expanded particles by heating and foaming foamable thermoplastic resin particles containing a foaming agent with a heating medium such as water vapor, and molding the pre-expanded particles. After filling the mold cavity, a heating medium such as water vapor is press-fitted into the mold to heat and foam the pre-foamed particles, and they are fused and integrated with each other by the foaming pressure while filling the gaps between the foamed particles. After that, it is manufactured through a cooling process in which the obtained thermoplastic resin foam molded article is cooled in a mold.
Conventionally, as one of the methods for producing the foamable thermoplastic resin particles, for example, a melt extrusion method (also referred to as an underwater cut method, a hot cut method, etc.) disclosed in Patent Documents 1 and 2 is known. Yes.

  Patent Document 1 discloses a method for producing foamable thermoplastic resin particles obtained by cutting a foaming agent-containing molten resin extruded from a die with a rotary cutter into resin particles, and using a die whose surface is thermally insulated, and a die surface And a method for producing expandable thermoplastic resin particles, characterized in that a rotating cutter is disposed in a non-contact state.

  In Patent Document 2, the temperature (T1) of the foaming agent-containing resin in the granulation die and the temperature (T2) of the granulation die satisfy T1> T2, and the flow rate (L1) of the cooling medium and the nozzle Foamability by a hot cut method for obtaining expandable thermoplastic resin particles while controlling the ratio (L1 / L2) to the discharge amount (L2) of the foaming agent-containing resin to be discharged from 100 to 200 A method for producing thermoplastic resin particles is disclosed.

JP-A-6-31726 International Publication No. 2011/066551

However, the above-described conventional technique has the following problems.
Since the die and the cutter are not in contact with each other, the manufacturing method disclosed in Patent Document 1 has a problem in that irregularly shaped particles are likely to be generated due to cut defects and resin particles are likely to be bonded together.
In the manufacturing method disclosed in Patent Document 2, since the die temperature is lower than the resin temperature, there is a problem that the resin is easily clogged and the opening ratio of the small holes of the die is low.

  The present invention was made in view of the above circumstances, in the production of thermoplastic resin particles and foamable thermoplastic resin particles by melt extrusion method, the porosity is high, the production efficiency is high, the generation of irregular particles can also be suppressed, Method for producing thermoplastic resin particles and expandable thermoplastic resin particles capable of obtaining uniform and substantially spherical resin particles, and further suppressing pre-foaming and resin particle coalescence during extrusion of the foaming agent-containing resin The issue is to provide

  In order to achieve the above object, the present invention extrudes a thermoplastic resin melted in a resin supply device directly into a cooling medium from a small hole formed in a resin discharge surface of a die attached to the tip of the resin supply device, Thermoplastic by melt extrusion method that cuts the extrudate with a cutter provided in a state of being pressed against the resin discharge surface of the die, and obtains thermoplastic resin particles by cooling and solidifying the extrudate by contact with a cooling medium. In the resin particle manufacturing method, the mass ratio (L1 / L2) of the flow rate (L1) of the cooling medium and the resin discharge amount (L2) is in the range of 40 to 250, and the pressing force of the cutter against the resin discharge surface is 0. Provided is a method for producing thermoplastic resin particles, which is characterized in that thermoplastic resin particles are obtained under conditions of a range of 05 to 2.0 MPa.

  In the method for producing thermoplastic resin particles of the present invention, the temperature of the cooling medium is preferably in the range of 20 to 80 ° C.

  In the method for producing thermoplastic resin particles of the present invention, the pressure of the cooling medium is preferably in the range of 0.1 to 2.0 MPa.

  Further, the present invention provides a small hole formed in a resin discharge surface of a die attached to the tip of a resin supply device by adding a foaming agent to a thermoplastic resin melted in a resin supply device and kneading the mixture. The extruded product is extruded directly into a cooling medium from the die and cut by a cutter provided in a state of being pressed against the resin discharge surface of the die, and the extrudate is cooled and solidified by contact with the cooling medium to expand the thermoplastic resin. In the method for producing expandable thermoplastic resin particles by melt extrusion to obtain particles, the mass ratio (L1 / L2) of the flow rate (L1) of the cooling medium and the resin discharge amount (L2) is in the range of 40 to 250. There is provided a method for producing expandable thermoplastic resin particles, wherein expandable thermoplastic resin particles are obtained under a condition that the pressing force of a cutter against a resin discharge surface is in a range of 0.05 to 2.0 MPa.

  In the method for producing expandable thermoplastic resin particles of the present invention, the temperature of the cooling medium is preferably in the range of 20 to 80 ° C.

  In the method for producing expandable thermoplastic resin particles of the present invention, the pressure of the cooling medium is preferably in the range of 0.1 to 2.0 MPa.

  Moreover, this invention provides the thermoplastic resin particle obtained by the manufacturing method of the said thermoplastic resin particle.

  Moreover, this invention provides the expandable thermoplastic resin particle obtained by the manufacturing method of the said expandable thermoplastic resin particle.

  The present invention also provides pre-expanded particles obtained by heating and foaming the expandable thermoplastic resin particles.

  The present invention also provides a foamed molded article obtained by filling the pre-expanded particles into a cavity of a mold and heating and molding in-mold.

The method for producing thermoplastic resin particles of the present invention is such that a thermoplastic resin melted in a resin supply device is extruded directly into a cooling medium from a small hole formed in a resin discharge surface of a die attached to the tip of the resin supply device. When cutting the extrudate with a cutter provided in a state of being pressed against the resin discharge surface of the die, and cooling and solidifying the extrudate by contact with the cooling medium to obtain thermoplastic resin particles, The condition that the mass ratio (L1 / L2) between the flow rate (L1) and the resin discharge amount (L2) is in the range of 40 to 250, and the pressing force of the cutter against the resin discharge surface is in the range of 0.05 to 2.0 MPa. By obtaining the thermoplastic resin particles below, it is possible to maintain a high rate of opening of the die small holes and to maintain high production efficiency of the thermoplastic resin particles.
Moreover, since generation | occurrence | production of irregular-shaped particle | grains and coalescence of resin particles can be suppressed, uniform and substantially spherical thermoplastic resin particles can be produced efficiently.

  The method for producing expandable thermoplastic resin particles according to the present invention includes adding a foaming agent to a thermoplastic resin melted in a resin supply device and kneading the foamed thermoplastic resin particles in a die attached to the tip of the resin supply device. The extrusion is directly extruded into the cooling medium from the small holes formed in the resin discharge surface, and the extrudate is cut by a cutter provided in a state of being pressed against the resin discharge surface of the die, and the extrudate is contacted with the cooling medium. When solidifying by cooling to obtain expandable thermoplastic resin particles, the mass ratio (L1 / L2) of the flow rate (L1) of the cooling medium to the resin discharge amount (L2) is in the range of 40 to 250, and the resin discharge surface By obtaining expandable thermoplastic resin particles under the condition that the pressing force of the cutter against the range of 0.05 to 2.0 MPa, it is possible to maintain a high opening ratio of the die small holes, and foamability Production of thermoplastic resin particles It is possible to maintain high efficiency. Moreover, since generation | occurrence | production of irregular-shaped particle | grains and coalescence of resin particles can be suppressed, uniform and substantially spherical foamable thermoplastic resin particles can be produced efficiently.

It is a block diagram which shows an example of the manufacturing apparatus of the thermoplastic resin particle by a melt extrusion method, and an expandable thermoplastic resin particle. It is a principal part expanded sectional view of the manufacturing apparatus of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The method for producing thermoplastic resin particles of the present invention is such that a thermoplastic resin melted in a resin supply device is extruded directly into a cooling medium from a small hole formed in a resin discharge surface of a die attached to the tip of the resin supply device. In addition, the extruded product is cut by a cutter provided while pressed against the resin discharge surface of the die, and the extruded product is cooled and solidified by contact with a cooling medium to obtain thermoplastic resin particles. In the method for producing plastic resin particles, the mass ratio (L1 / L2) between the flow rate of the cooling medium (L1) and the resin discharge amount (L2) is in the range of 40 to 250, and the pressing force of the cutter against the resin discharge surface is 0. It is characterized in that thermoplastic resin particles are obtained under the condition of 0.05 to 2.0 MPa.

  The thermoplastic resin particles obtained by the method for producing thermoplastic resin particles of the present invention are substantially spherical resin particles having a substantially uniform particle size and mass, and can be used in various applications. For example, the thermoplastic resin particles of the present invention are suitably used as a seed (core) material or the like when producing expandable thermoplastic resin particles by a seed polymerization method or the like.

  Further, in the method for producing expandable thermoplastic resin particles of the present invention, a foaming agent is added to and kneaded with a thermoplastic resin melted in a resin supply device, and the foaming agent-containing molten resin is attached to the tip of the resin supply device. The extrusion is directly extruded into the cooling medium from the small holes formed on the resin discharge surface of the die, and the extrudate is cut by a cutter provided in a state of being pressed against the resin discharge surface of the die. In the method for producing expandable thermoplastic resin particles by melt extrusion, which is cooled and solidified by contact to obtain expandable thermoplastic resin particles, the mass ratio (L1) between the flow rate of the cooling medium (L1) and the resin discharge amount (L2) / L2) is in the range of 40 to 250, and expandable thermoplastic resin particles are obtained under conditions where the pressing force of the cutter against the resin discharge surface is in the range of 0.05 to 2.0 MPa.

  In the present invention, the type of thermoplastic resin is not limited. For example, a polystyrene resin, a polyethylene resin, a polypropylene resin, a polyester resin, a vinyl chloride resin, an ABS resin, an AS resin, or the like can be used alone or in combination. Can be used. Furthermore, it is possible to use a recovered resin of a thermoplastic resin obtained after being used once as a resin product. In particular, polystyrene resins such as amorphous polystyrene (GPPS) and high impact polystyrene (HIPS) are preferably used.

  Examples of polystyrene resins include homopolymers of styrene monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromostyrene, or copolymers thereof. A polystyrene-based resin containing 50% by mass or more of styrene is preferable, and polystyrene is more preferable. Further, the polystyrene resin may be a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, the main component of which is the styrene monomer. As, for example, alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl In addition to fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

  If a polystyrene resin is the main component, other resins may be added. Examples of the resin to be added include polybutadiene, styrene-butadiene copolymer to improve the impact resistance of the foam molded article. Examples thereof include rubber-modified polystyrene resins to which a diene rubbery polymer such as a polymer, ethylene-propylene-nonconjugated diene three-dimensional copolymer is added, so-called high impact polystyrene. Alternatively, a polyethylene resin, a polypropylene resin, an acrylic resin, an acrylonitrile-styrene copolymer, an acrylonitrile-butadiene-styrene copolymer, and the like can be given. In addition, as a polystyrene resin as a raw material, a polystyrene resin (virgin polystyrene) that is not a recycled raw material, such as a commercially available ordinary polystyrene resin, a polystyrene resin newly produced by a method such as a suspension polymerization method, or the like is used. In addition to being usable, it is possible to use a recycled material obtained by regenerating a used polystyrene resin foam molded article. As this recycled material, used polystyrene-based resin foam moldings such as fish boxes, household appliance cushioning materials, food packaging trays, etc. are collected, and recycled materials that are regenerated by the limonene dissolution method or heating volume reduction method are used. Can do. Recyclable raw materials that can be used include home appliances (eg, TVs, refrigerators, washing machines, air conditioners) and office work, in addition to those obtained by reprocessing used polystyrene-based resin foam moldings. A non-foamed polystyrene resin molded product that has been separated and collected from an industrial machine (for example, a copying machine, a facsimile machine, a printer, etc.), pulverized, melt-kneaded, and repelletized can be used.

The foaming agent used in the foamable thermoplastic resin particles of the present invention is not particularly limited, but examples thereof include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, and cyclopentane, dimethyl ether, diethyl ether, and the like. Ethers, various alcohols such as methanol and ethanol, carbon dioxide, nitrogen, water and the like can be used. Of these, aliphatic hydrocarbons are preferred, and normal butane, isobutane, normal pentane, isopentane alone or a mixture thereof is more preferred. Further, normal pentane, isopentane, neopentane, cyclopentane, cyclopentadiene alone or a mixture thereof, which is a hydrocarbon having 5 carbon atoms, is particularly suitable. Of these, a mixture of one or both of isopentane and normal pentane is preferable. Further, it mainly comprises the hydrocarbon having 5 carbon atoms, has a boiling point of 20 ° C. or less, and may contain a blowing agent other than the hydrocarbon having 5 carbon atoms (for example, normal butane, isobutane, propane, carbon dioxide gas, etc.). .
The amount of the foaming agent added is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and particularly preferably 2 to 8 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

  In the present invention, the thermoplastic resin contains, as a foam nucleating agent, inorganic or organic fine particles such as talc, calcium silicate, synthetically or naturally produced silicon dioxide, ethylene bis-stearic acid amide, and methacrylic acid ester copolymers. It is desirable to add powder. The amount of the foam nucleating agent added is preferably 1.5 parts by mass or less, more preferably 0.1 to 1.0 part by mass with respect to 100 parts by mass of the thermoplastic resin.

  In the present invention, the thermoplastic resin includes, in addition to the foaming agent and the foaming nucleating agent, a binding inhibitor, a bubble regulator, a crosslinking agent, a filler, a difficult agent within the range that does not impair the physical properties of the obtained prefoamed particles. You may add additives, such as a flame retardant, a flame-retardant adjuvant, a lubricant, and a coloring agent.

FIG. 1 is a configuration diagram illustrating an example of a production apparatus used in the method for producing thermoplastic resin particles and the method for producing foamable thermoplastic resin particles of the present invention. The manufacturing apparatus of this example includes an extruder 1 as a resin supply device, a die 2 attached to the tip of the extruder 1 and having a large number of small holes, and a raw material supply hopper 3 for charging a resin raw material into the extruder 1. And a high pressure pump 4 for press-fitting the foaming agent into the molten resin in the extruder 1 through the foaming agent supply port 5 and a resin discharge surface in which a small hole of the die 2 is made to contact the cooling water, A cutting chamber 7 in which a cooling medium such as cooling water (hereinafter referred to as cooling water) is circulated and supplied into the chamber, and a rotation inside the cutting chamber 7 is provided so that the resin extruded from the small hole of the die 2 can be cut. A cutter 6, a dehydrating dryer 10 having a solid-liquid separation function for separating resin particles carried along with the flow of cooling water from the cutting chamber 7 from the cooling water and dehydrating and drying to obtain resin particles; To dehydrating dryer 10 with separation function A water tank 8 for storing the separated cooling water, a high-pressure pump 9 for sending the cooling water in the water tank 8 to the cutting chamber 7, and a storage for storing the resin particles dehydrated and dried by the dehydration dryer 10 with a solid-liquid separation function. And a container 11.
When the manufacturing apparatus shown in FIG. 1 is used and the thermoplastic resin particle manufacturing method is performed, the high-pressure pump 4 is not used, and the foaming agent is not pressed into the molten resin in the extruder 1 through the foaming agent supply port 5. On the other hand, when implementing the manufacturing method of a foamable thermoplastic resin, the foaming agent is press-fitted into the molten resin in the extruder 1 through the foaming agent supply port 5 using the high-pressure pump 4.

  As the extruder 1, either an extruder using a screw or an extruder not using a screw can be used. Examples of the extruder using a screw include a single-screw extruder, a multi-screw extruder, a vent-type extruder, and a tandem extruder. Examples of the extruder that does not use a screw include a plunger type extruder and a gear pump type extruder. Moreover, any extruder can use a static mixer. Among these extruders, an extruder using a screw is preferable from the viewpoint of productivity. Moreover, the conventionally well-known thing used in the granulation method by melt extrusion of resin can also be used for the cutting chamber 7 which accommodated the cutter 6. FIG.

FIG. 2 is an enlarged cross-sectional view of a main part in which the die 2 and the cutting chamber 7 in the manufacturing apparatus shown in FIG.
The die 2 attached to the front end of the extruder 1 has a plurality of resin flow paths 22, and a plurality of small holes 21 are formed at the front ends of the respective resin flow paths 22. The molten resin 20 fed from is pressed into the die 2, passes through each resin flow path 22, passes through a large number of small holes 21, and is extruded from the resin discharge surface 23 side of the die 2.
The resin discharge surface 23 through which the molten resin 20 is pushed out from the small hole 21 is connected to the cutting chamber 7 in which cooling water is circulated and supplied into the chamber. A cutter 6 is rotatably disposed in the cutting chamber 7. The cutting edge tip of the cutter 6 is in contact with the resin discharge surface 23 and pressed with a pressing force P.
A heat insulating material 24 is provided at an appropriate place of the resin discharge surface 23 of the die 2, for example, in the center portion, and the die 2 is excessively cooled by cooling water and the small holes 21 are blocked by the solidified resin, and the hole area ratio is reduced. It is preferable to prevent this. A plurality of heaters 25, 26, 27, and 28 and a temperature sensor 29 are inserted into the die 2 so that the die 2 can be kept at a predetermined temperature.

  In order to produce expandable thermoplastic resin particles using the production apparatus shown in FIGS. 1 and 2, first, a thermoplastic resin such as polystyrene resin as a raw material, a foam nucleating agent, and a flame retardant added as necessary A desired additive such as the above is weighed and charged into the extruder 1 from the raw material supply hopper 3. The raw material thermoplastic resin may be mixed in advance in the form of pellets or granules and then charged from one raw material supply hopper. For example, when a plurality of lots are used, the supply amount for each lot may be reduced. A plurality of adjusted raw material supply hoppers may be charged and mixed in an extruder. Also, when using a combination of recycled materials from multiple lots, mix the raw materials from multiple lots in advance and remove foreign matter using appropriate sorting methods such as magnetic sorting, sieving, specific gravity sorting, and air blowing sorting. It is preferable to keep it.

  After supplying thermoplastic resin, foaming aid, and other additives into the extruder 1, the resin is heated and melted, and foamed by the high-pressure pump 4 from the foaming agent supply port 5 while transferring the molten resin to the die 2 side. The blowing agent is mixed into the molten resin 20 by press-fitting the agent, and the molten resin 20 is moved to the tip side while being further kneaded through a foreign matter removing screen provided in the extruder 1 as necessary. Is extruded from the small hole 21 of the die 2 attached to the tip of the extruder 1.

  The resin discharge surface 23 in which the small hole 21 of the die 2 is formed is disposed in the cutting chamber 7 in which cooling water is circulated and supplied into the chamber, and the resin extruded from the small hole is placed in the cutting chamber 7. A cutter 6 is rotatably provided so that it can be cut. When the molten resin 20 to which the foaming agent has been added is extruded from the small hole of the die 2 attached to the tip of the extruder 1, the molten resin 20 is cut into granules, rapidly cooled in contact with cooling water, and expandable thermoplastic resin particles It becomes.

  In the method for producing thermoplastic resin particles and the method for producing expandable thermoplastic resin particles of the present invention, the mass ratio (L1 / L2) between the flow rate of cooling water (L1) and the amount of discharged resin (L2) is 40 to 40. The range is 250. This mass ratio (L1 / L2) is preferably in the range of 50 to 150, and more preferably in the range of 60 to 120. When the mass ratio (L1 / L2) is less than 40, the cooled state of the cut resin particles is deteriorated, and the resin particles are easily bonded to each other. When the mass ratio (L1 / L2) exceeds 250, the resin discharge surface 23 of the die 2 is excessively cooled, so that the small holes 21 are blocked by the solidified resin, and the hole area ratio is reduced. .

  In the method for producing thermoplastic resin particles and the method for producing foamable thermoplastic resin particles of the present invention, the pressing force P of the cutter 6 against the resin discharge surface 23 is set in the range of 0.05 to 2.0 MPa. The pressing force P is preferably in the range of 0.10 to 1.2 MPa, and more preferably in the range of 0.2 to 0.8 MPa. If the pressing force P is less than 0.05 MPa, the cutter 6 is likely to be separated from the resin discharge surface 23 due to the supply water pressure of the cooling water, the resin supply pressure, etc., and the extrudate cannot be stably cut. Incidence generation rate increases. When the pressing force P exceeds 2.0 MPa, the frictional resistance of the cutter 6 against the resin discharge surface 23 increases, the rotation of the cutter 6 becomes unstable, and the size of the obtained resin particles tends to vary.

  In the method for producing thermoplastic resin particles and the method for producing expandable thermoplastic resin particles of the present invention, the temperature of the cooling water is preferably in the range of 20 to 80 ° C, more preferably in the range of 25 to 70 ° C. A range of 30 to 60 ° C. is more preferable.

  In the method for producing thermoplastic resin particles and the method for producing expandable thermoplastic resin particles of the present invention, the pressure of the cooling water is preferably in the range of 0.1 to 2.0 MPa, and 0.15 to 1. The range of 8 MPa is more preferable, and the range of 0.2 to 1.6 MPa is more preferable.

  In the method for producing the thermoplastic resin particles and the method for producing the foamable thermoplastic resin particles of the present invention, the die temperature (T1) is preferably higher than the resin temperature (T2) (T1> T2), more preferably than the resin temperature. Is preferably 5 to 150 ° C., more preferably 30 to 120 ° C.

  The formed expandable thermoplastic resin particles are transferred from the cutting chamber 7 to the flow of cooling water and carried to the dehydrating dryer 10 with a solid-liquid separation function, where the expandable thermoplastic resin particles are separated from the cooling water. And dehydrated and dried. The dried foamable thermoplastic resin particles are stored in the storage container 11.

  The method for producing expandable thermoplastic resin particles according to the present invention includes adding a foaming agent to a thermoplastic resin melted in a resin supply device and kneading the foamed thermoplastic resin particles in a die attached to the tip of the resin supply device. The extrusion is directly extruded into the cooling medium from the small holes formed in the resin discharge surface, and the extrudate is cut by a cutter provided in a state of being pressed against the resin discharge surface of the die, and the extrudate is contacted with the cooling medium. When solidifying by cooling to obtain expandable thermoplastic resin particles, the mass ratio (L1 / L2) of the flow rate (L1) of the cooling medium to the resin discharge amount (L2) is in the range of 40 to 250, and the resin discharge surface By obtaining expandable thermoplastic resin particles under the condition that the pressing force of the cutter against the range of 0.05 to 2.0 MPa, it is possible to maintain a high opening ratio of the die small holes, and foamability Production of thermoplastic resin particles It is possible to maintain high efficiency. Moreover, since generation | occurrence | production of irregular-shaped particle | grains and coalescence of resin particles can be suppressed, uniform and substantially spherical foamable thermoplastic resin particles can be produced efficiently.

The foamable thermoplastic resin particles of the present invention are pre-foamed by heating with steam heating or the like using a well-known apparatus and technique in the field of foamed resin molding production to obtain pre-foamed particles. The pre-expanded particles are pre-expanded so as to have a bulk density equivalent to the density of the foamed molded product to be manufactured. In the present invention, its bulk density is not limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the bulk density of the pre-expanded particles refers to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”.
<Bulk density of pre-expanded particles>
First, Wg was sampled from pre-expanded particles as a measurement sample, this measurement sample was naturally dropped into a graduated cylinder, and the volume Vcm ³ of the measurement sample dropped into the graduated cylinder was measured using an apparent density measuring instrument based on JIS K6911. The bulk density of the pre-expanded particles is measured based on the following formula.
Bulk density (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Bulk expansion ratio of pre-expanded particles>
Moreover, the bulk expansion ratio of the pre-expanded particles is a numerical value calculated by the following equation.
Bulk foaming factor = 1 / bulk density (g / cm ³ )

The pre-expanded particles are filled in a cavity of a mold using a well-known apparatus and method in the field of manufacturing a foamed resin molded body, heated by steam heating or the like, and subjected to in-mold foam molding, A plastic resin foam molded article (hereinafter referred to as a foam molded article) is produced.
Although the density of the foamed molded article of the present invention is not particularly limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the density of the foamed molded product refers to the density of the foamed molded product measured by the method described in JIS K7122: 1999 “Measurement of foamed plastic and rubber-apparent density”.
<Density of foam molding>
A test piece of 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) was cut so as not to change the original cell structure of the material, its mass was measured, and calculated by the following formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
Test piece condition adjustment and measurement test pieces were cut out from samples that had passed 72 hours or more after molding, and were subjected to atmospheric conditions of 23 ° C. ± 2 ° C. × 50% ± 5% or 27 ° C. ± 2 ° C. × 65% ± 5%. It has been left for more than an hour.

<Folding multiple of foamed molded product>
Further, the expansion factor of the foamed molded product is a numerical value calculated by the following equation.
Foaming factor = 1 / density (g / cm ³ )

[Example 1]
(Manufacture of foamable thermoplastic resin particles)
As a thermoplastic resin, 0.3 parts by mass of fine powder talc is added to 100 parts by mass of a polystyrene resin having a weight average molecular weight (Mw) of 200,000 (trade name “HRM10N”, manufactured by Toyo Styrene Co., Ltd.). Continuous supply to the screw extruder. As the extruder internal temperature, the maximum temperature was set to 210 ° C., and after the resin was melted, 5 parts by weight of pentane (isopentane: normal pentane = 20: 80 (mass ratio)) as a blowing agent with respect to 100 parts by weight of the resin. Was press-fitted from the middle of the extruder. The resin and foaming agent are kneaded and cooled in the extruder, the temperature of the molten resin flowing into the die from the tip of the extruder is 180 ° C., the die temperature is 105 ° C. higher than the temperature of the molten resin, and the die resin The pressure of the introduction portion is maintained at 12 MPa, and a die having 200 holes having a diameter of 0.6 mm and a land length of 3.0 mm is connected to the discharge side of the die, and the temperature of the cooling water is 40 ° C. In addition, the foaming agent-containing molten resin is extruded at a resin discharge rate of 170 (kg / hr) into a cutting chamber in which cooling water is circulated at a cooling water pressure of 0.5 MPa and a cooling water flow rate of 18000 (kg / hr). The extrudate was cut with a high-speed rotary cutter having 10 blades in the circumferential direction. The mass ratio of the cooling water flow rate / resin discharge amount was 106. The pressing force against the resin discharge surface of the cutter was set to 0.4 MPa. The temperature of the molten resin is measured between the outlet of the extruder 1 shown in FIG. 2 and the inlet of the die 2, and the die temperature is a thermocouple provided at a thickness about half the thickness of the die 2 shown in FIG. 2. The temperature was measured at the tip of the temperature sensor 29. While cooling the cut particles with circulating cooling water, the particles were conveyed to a particle separator to separate the particles from the cooling water. Further, the collected particles were dehydrated and dried to obtain expandable polystyrene resin particles. The obtained expandable polystyrene resin particles were almost perfect spheres without the occurrence of deformation or beard, and the average particle size was about 1.1 mm.
Polyethylene glycol 0.03 parts by mass, zinc stearate 0.15 parts by mass, stearic acid monoglyceride 0.05 parts by mass, hydroxystearic acid triglyceride 0.05 parts by mass with respect to 100 parts by mass of the obtained expandable polystyrene resin particles. The part was uniformly coated on the entire surface of the expandable polystyrene resin particles.

(Manufacture of foam moldings)
The expandable polystyrene resin particles produced as described above are placed in a 15 ° C. cool box and allowed to stand for 72 hours, and then supplied to a cylindrical batch type pre-foaming machine to generate steam with a blowing pressure of 0.05 MPa. To obtain pre-expanded particles. The obtained pre-expanded particles had a bulk density of 0.020 g / cm ³ (bulk expansion ratio: 50 times).
Subsequently, the pre-expanded particles obtained were allowed to stand at room temperature for 24 hours, and then the pre-expanded particles were filled into a mold having a rectangular cavity of length 400 mm × width 300 mm × height 50 mm. Thereafter, the inside of the cavity of the mold is heated with water vapor at a gauge pressure of 0.08 MPa for 20 seconds, and then cooled until the pressure in the cavity of the mold reaches 0.01 MPa. Opened, a rectangular foam molded body having a length of 400 mm, a width of 300 mm, and a height of 50 mm was taken out. The obtained foamed molded article had a density of 0.020 g / cm ³ (foaming factor: 50 times).
At the time of producing the expandable polystyrene resin particles of Example 1 produced by the method as described above, an evaluation test on the following <aperture ratio> and <ratio of coalesced particles> was performed, and based on the respective results. It evaluated based on <judgment criteria of comprehensive evaluation>. The results are shown in Table 1.

<Aperture ratio>
One hour after the start of the production of the expandable resin particles, the resin discharge surface of the die was examined, and the aperture ratio of small holes was calculated as follows.
Opening rate (opening rate during extrusion of small holes on the die surface) = number of holes / total number of small holes of the die × 100 (%)
Discharge rate (kg / hr) = total mass of all expandable resin particles cut out by a cutter per hour = number of holes × number of cuts × 1 particle mass = number of holes × number of cutter blades × number of cutter rotations × 1 particle The number of apertures by mass is
Since the number of holes = discharge amount (kg / hr) / [number of cutter blades × cutter rotation speed (rph) × 1 grain mass (kg / piece), the hole area ratio can be calculated by the following equation.
Opening ratio (E) = number of holes / total number of small holes × 100 (%)
= [Q / (N × R × 60 × (M / 100) / 1000)] / H × 100 (%)
(In the formula, Q is the discharge amount (kg / hr), N is the number of cutter blades, R is the number of revolutions of the cutter (rpm), M is 100 grains mass (g) (choose any 100 grains from foamable resin particles) The mass of 100 grains weighed with an electronic balance having a minimum graduation of 0.000 lg, H represents the total number of small holes in the die.)
The hole area ratio was evaluated according to the following criteria.
Good (◯): 70% or more Slightly good (△): 50% or more and less than 70% Defect (x): Less than 50%

<Ratio of coalescing particles>
About 1 g of the arbitrarily selected expandable resin particles was precisely weighed with an electronic balance to determine the mass (W1). Among them, two or more bonded particles were selected and similarly weighed with an electronic balance to determine the mass (W2) and calculated according to the following formula.
Fused particle ratio = W2 / W1 × 100 (%)
The coalesced particles were evaluated according to the following criteria.
Good (◯): Less than 0.5% Slightly good (△): 0.5 or more, less than 1.0% Defect (x): 1.0% or more

<Criteria for comprehensive evaluation>
Particularly good (◎): Both the open area ratio and the coalescence ratio are ○
Good (O): Either one of the open area ratio or the bonding ratio is O or Δ, or both are Δ
Defect (x): Either one of the hole area ratio or the bonding rate is x or both are x

[Example 2]
The same operation as in Example 1 was performed except that the cooling water pressure was changed to 1.0 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 1.

[Example 3]
The same operation as in Example 1 was performed except that the cooling water pressure was changed to 1.7 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 1.

[Example 4]
It implemented similarly to Example 1 except having changed the pressing force of the cutter into 0.1 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 1.

[Example 5]
It implemented similarly to Example 1 except having changed the pressing force of the cutter into 0.2 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 1.

[Example 6]
It implemented similarly to Example 1 except having changed the pressing force of the cutter into 1.2 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 1.

[Example 7]
It implemented similarly to Example 1 except having changed the pressing force of the cutter into 0.8 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 1.

[Example 8]
Except not using a foaming agent, it implemented similarly to Example 1 and obtained the polystyrene-type resin particle which does not contain a foaming agent. During the production of the polystyrene-based resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 2.

[Example 9]
Except that ethylene-vinyl acetate copolymer (manufactured by Asahi Kasei Chemicals Corporation, product name “Suntech EF0510”) was used as the thermoplastic resin, the resin temperature was changed to 250 ° C., and the temperature of the cooling medium was changed to 60 ° C. In the same manner as in No. 8, thermoplastic resin particles were obtained. At the time of production of the thermoplastic resin particles, evaluation tests were conducted on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 2.

[Example 10]
Performed in the same manner as in Example 8 except that polypropylene (product name “F-744NP” manufactured by Prime Polymer Co., Ltd.) was used as the thermoplastic resin, the resin temperature was changed to 260 ° C., and the temperature of the cooling medium was changed to 60 ° C. Thus, thermoplastic resin particles were obtained. At the time of production of the thermoplastic resin particles, evaluation tests were conducted on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 2.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the cooling water flow rate was 6000 kg / hr and the mass ratio of the cooling water flow rate / resin discharge amount was changed to 35. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 3.

[Comparative Example 2]
The same operation as in Example 1 was performed except that the pressing force of the cutter was changed to 0.04 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 3.

[Comparative Example 3]
The same operation as in Example 1 was performed except that the pressing force of the cutter was changed to 2.5 MPa. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 3.
In Comparative Example 3, the extruder stopped due to the load due to the pressing force of the cutter, and continuous operation was difficult.

[Comparative Example 4]
The same procedure as in Example 1 was performed except that the cooling water flow rate was 44200 kg / hr and the mass ratio of the cooling water flow rate / resin discharge amount was changed to 260. During the production of the expandable polystyrene resin particles, an evaluation test was performed on the porosity and the ratio of coalesced particles in the same manner as in Example 1, and comprehensive evaluation was performed based on the respective results. The results are shown in Table 3.

From the results of Tables 1 to 3, the mass ratio of the cooling water flow rate / resin discharge amount is in the range of 40 to 250, and the pressing force of the cutter against the resin discharge surface is in the range of 0.05 to 2.0 MPa. Examples 1 to 10 according to the present invention, in which thermoplastic resin particles were produced under conditions, can maintain a high rate of die small hole opening, and maintain high production efficiency of thermoplastic resin particles. I was able to.
Moreover, since generation | occurrence | production of irregular shaped particle | grains and coalescence of resin particles can be suppressed, the uniform and substantially spherical thermoplastic resin particle was able to be produced efficiently.

On the other hand, Comparative Example 1 in which the resin particles were produced under the condition that the mass ratio of the flow rate of the cooling water / the amount of the discharged resin was lower than the range of the present invention was 35. Became bad.
Moreover, the comparative example 2 which manufactured the resin particle on the conditions which made the pressing force of a cutter less than the range of this invention and was 0.04 Mpa becomes higher than Examples 1-10, and the coalescence particle rate becomes higher. Evaluation was poor.
Further, Comparative Example 3 in which the resin particles were produced under the condition that the pressing force of the cutter exceeded the range of the present invention was set to 2.5 MPa had a high coalescing particle ratio and a low hole area ratio. Became bad. Furthermore, in Comparative Example 3, the extruder stopped due to the load due to the pressing force of the cutter, and continuous operation was difficult.
Moreover, the comparative example 4 which manufactured the resin particle on the conditions made into 260 which the mass ratio with the flow volume / resin discharge amount of a cooling water exceeds the range of this invention has a very low opening rate, and is comprehensive. Evaluation was poor.

  In the production of thermoplastic resin particles and expandable thermoplastic resin particles by the melt extrusion method, the present invention has a high porosity, high production efficiency, can suppress the generation of irregularly shaped particles, and is uniform and substantially spherical resin particles. Further, the present invention provides a method for producing thermoplastic resin particles and expandable thermoplastic resin particles, which can further suppress pre-foaming and extrusion of resin particles during extrusion of the foaming agent-containing resin.

  DESCRIPTION OF SYMBOLS 1 ... Extruder (resin supply apparatus), 2 ... Die, 3 ... Raw material supply hopper, 4 ... High pressure pump, 5 ... Foam supply port, 6 ... Cutter, 7 ... Cutting chamber, 8 ... Water tank, 9 ... High pressure pump, DESCRIPTION OF SYMBOLS 10 ... Dehydration dryer with a solid-liquid separation function, 11 ... Storage container, 20 ... Molten resin, 21 ... Small hole, 22 ... Resin flow path, 23 ... Resin discharge surface, 24 ... Thermal insulation, 25, 26, 27, 28 ... heater, 29 ... temperature sensor.

Claims (8)

A state in which the thermoplastic resin melted in the resin supply device is directly extruded into a cooling medium from a small hole formed in the resin discharge surface of the die attached to the tip of the resin supply device, and is pressed by the resin discharge surface of the die In the method for producing thermoplastic resin particles by the melt extrusion method, the extrudate is cut by the cutter provided in the above, and the extrudate is cooled and solidified by contact with a cooling medium to obtain thermoplastic resin particles.
The mass ratio (L1 / L2) of the flow rate (L1) of the cooling medium and the resin discharge amount (L2) is in the range of 40 to 250, and the pressing force of the cutter against the resin discharge surface is in the range of 0.10 to 1.2 MPa . A method for producing thermoplastic resin particles, characterized in that thermoplastic resin particles are obtained under a condition in which a relationship between a die temperature (T1) and a resin temperature (T2) satisfies T1> T2 .   The temperature of a cooling medium is the range of 20-80 degreeC, The manufacturing method of the thermoplastic resin particle of Claim 1 characterized by the above-mentioned.   The method for producing thermoplastic resin particles according to claim 1 or 2, wherein the pressure of the cooling medium is in the range of 0.1 to 2.0 MPa. A foaming agent is added to the thermoplastic resin melted in the resin supply device and kneaded, and the foaming agent-containing molten resin is directly put into the cooling medium from a small hole formed on the resin discharge surface of the die attached to the tip of the resin supply device. The extrudate is cut by a cutter provided in a state where it is pressed against the resin discharge surface of the die, and the extrudate is cooled and solidified by contact with a cooling medium to obtain expandable thermoplastic resin particles. In the method for producing expandable thermoplastic resin particles by an extrusion method,
The mass ratio (L1 / L2) of the flow rate (L1) of the cooling medium and the resin discharge amount (L2) is in the range of 40 to 250, and the pressing force of the cutter against the resin discharge surface is in the range of 0.10 to 1.2 MPa . A process for producing expandable thermoplastic resin particles, characterized in that expandable thermoplastic resin particles are obtained under a condition in which a relationship between a die temperature (T1) and a resin temperature (T2) satisfies T1> T2 .   The method for producing expandable thermoplastic resin particles according to claim 4, wherein the temperature of the cooling medium is in the range of 20 to 80 ° C.   The method for producing expandable thermoplastic resin particles according to claim 4 or 5, wherein the pressure of the cooling medium is in the range of 0.1 to 2.0 MPa. A step of producing a foamed thermoplastic resin particles by the method for producing expandable thermoplastic resin particles according to any one of claims 4 to 6, thereby the expandable thermoplastic resin particles by heating the foam A process for producing pre-expanded particles. Foam molding comprising the steps of producing pre-foamed particles by the method of producing pre-foamed particles according to claim 7, and filling the pre-foamed particles into a cavity of a mold and heating to mold in- mold. Body manufacturing method.

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