JP5258147B2 - Expandable thermoplastic resin particles and method for producing the same, antistatic agent composition for expandable thermoplastic resin particles, and antistatic method for expandable thermoplastic resin particles - Google Patents

Description

  The present invention relates to an expandable thermoplastic resin particle and a method for producing the same, an antistatic composition for the expandable thermoplastic resin particle, and an antistatic method for the expandable thermoplastic resin particle. The foamable thermoplastic resin particles are used as a raw material for thermoplastic resin foam molded products that are widely used in various fields such as various packaging containers for foods, cushioning materials, construction materials and the like.

  Among the foamable thermoplastic resin particles, typical foamable styrene resin particles are generally provided with a stirrer for resin pellets produced using a styrene resin particle obtained by a suspension polymerization method or an extruder. It is produced by a so-called impregnation method in which it is suspended in an aqueous dispersant in a pressure vessel and impregnated with a foaming agent under heating and pressure. After impregnating with the foaming agent, the particles taken out from the container are subjected to washing, dehydration, and classification using a sieve, and then coated with a surface treatment agent such as an antiblocking agent or an antistatic agent by a blender such as a blender or a mixer. Become a product. At this time, in the process from the end of the dehydration until the surface treatment agent is coated with the mixer, in order to prevent a disaster due to electrostatic ignition to the flammable foaming agent that escapes from the resin particles, It is necessary to take measures to prevent ignition such as nitrogen gas replacement in the next stock tank.

  The expandable styrene resin particles can also be produced by a so-called extrusion method in which a foaming agent and a resin are melt-kneaded in an extruder and extruded from a die attached to the tip of the extruder and cut into particles. In this case, since there is no adhesion of impurities such as a dispersant to the particle surface, there is a possibility that charging due to static electricity will be larger than the expandable styrene resin particles obtained by the impregnation method. Therefore, fire prevention measures such as nitrogen gas replacement are essential.

For example, techniques disclosed in Patent Documents 1 to 5 have been proposed as conventional techniques related to the production of foamable thermoplastic resin particles and the addition of antistatic properties.
Patent Document 1 discloses a foaming property in which the surface is coated with a hydroxy higher fatty acid amide and a cationic surfactant for the purpose of obtaining a foamed molded article with little dust adsorption and good heat-fusibility and surface finish. Styrenic resin particles are disclosed. However, these hydroxy higher fatty acid amides and cationic surfactants are powdery surface treatment agents that are coated on products, and Patent Document 1 discloses charging to foamable thermoplastic resin particles before surface treatment. There is no description of imparting preventive properties.
In Patent Document 2, a thermoplastic resin typified by polystyrene and a foaming agent are melt-kneaded in an extruder, then discharged into a heated and pressurized liquid from a die, immediately cut and granulated, and then a dispersing agent. Or the manufacturing method of the expandable thermoplastic resin particle which heat-processes in presence of surfactant is disclosed. However, in this method, the spheroidized resin particles are only dried after being cooled with water, so that the resin particles are easily charged. Patent Document 2 does not describe imparting antistatic properties to the expandable thermoplastic resin particles before the surface treatment.
Patent Document 3 discloses styrene-based expandable resin particles for producing a foamed molded article having a low content of volatile solvents such as styrene, toluene, and xylene. Patent Document 3 describes that the surface can be coated with an antistatic agent such as amines or glycerin, an anti-blocking agent, or a high cycle agent, but Patent Document 3 describes that before surface treatment. It does not describe imparting antistatic properties to the foamable thermoplastic resin particles.

In Patent Document 4, an antistatic agent is added to thermoplastic synthetic resin particles, both of them are stirred and mixed under high shear force, and the surface layer of the resin particles is softened and the antistatic property is applied to the surface of the resin particles. An antistatic agent-containing synthetic resin particle is prepared by adhering an agent, and then a method for producing foaming agent resin particles having an antistatic property in which the antistatic agent-containing synthetic resin is impregnated with a foaming agent in an aqueous medium is disclosed. Yes.
Patent Document 5 is obtained by foaming olefin resin particles containing 1 to 30% by mass of a polymer or copolymer of polyethylene glycol (meth) acrylate and 0.01 to 3% by mass of a surfactant. Antistatic olefinic resin pre-expanded particles are disclosed.
Japanese Patent Laid-Open No. 5-125213 JP-A-9-221562 JP 2002-356575 A Japanese Patent Publication No. 6-860 Japanese Patent Laid-Open No. 10-147660

However, the above-described conventional technique has the following problems.
Patent Documents 1 to 3 describe that the foamable thermoplastic resin particles before the surface treatment process are easily charged when transferred and stored in a granulation line or a primary stock tank, and the need for prevention of charging during the transfer and storage. No specific antistatic measures are described. Therefore, in the prior art described in Patent Documents 1 to 3, when transferring and storing the expandable thermoplastic resin particles before the surface treatment process, the granulation line or the primary stock tank is replaced with nitrogen gas or the like due to static electricity. It is necessary to take measures to prevent the flammable foaming agent that escapes from the resin particles from igniting even if a spark occurs. However, a large amount of nitrogen gas is required to replace the granulation line and the primary stock tank with nitrogen gas, and there is a problem that it takes a lot of man-hours and costs to maintain the apparatus for that purpose.

  In the techniques described in Patent Documents 4 and 5, since the antistatic agent is contained in the expandable thermoplastic resin particles, the resin particles are difficult to be charged when the expandable thermoplastic resin particles are transferred and stored. , Safety measures when transferring and storing foaming thermoplastic resin particles can be reduced to some extent. However, a large amount of antistatic agent must be included in the resin particles in order to prevent electrification during the transfer of the foaming thermoplastic resin particles and to completely prevent ignition due to static electricity without replacing nitrogen gas. The cost of the product will rise. In addition, when a large amount of antistatic agent is contained in the resin particles, the fusion between the foamed particles becomes worse at the time of foam molding, and the mechanical strength of the resulting foam molded article may be lowered, or the heat insulation performance may be lowered. There is.

  The present invention has been made in view of the above circumstances, and is capable of effectively preventing the foaming thermoplastic resin particles from being charged before the surface treatment process and reducing the safety measures such as nitrogen gas replacement during transfer and storage. It is an object of the present invention to provide particles and a production method thereof, an antistatic agent composition for expandable thermoplastic resin particles, and an antistatic method for expandable thermoplastic resin particles.

In order to achieve the above object, the present invention comprises a surface coated with an antistatic agent containing a humectant and a surfactant as essential components, and the humectant contains one or more polyhydric alcohols. The foamable thermoplastic resin particles are characterized in that the surfactant is one or more selected from the group consisting of an anionic surfactant, a cationic surfactant, and an amphoteric surfactant. .

  In the foamable thermoplastic resin particles of the present invention, it is preferable that the powdery surface treatment agent is coated on the surface after the antistatic agent is coated.

The present invention also relates to a charging method comprising a moisturizing agent and a surfactant as essential components in a method for producing expandable thermoplastic resin particles, which is produced by applying a surface treatment step for coating the expandable thermoplastic resin particles with a surface treatment agent. look including the step of coating the agents on expandable thermoplastic resin particles before the surface treatment step, the humectant comprises one or more polyhydric alcohols, wherein the surfactant is an anionic surfactant The present invention provides a method for producing expandable thermoplastic resin particles, which is one or more selected from the group consisting of a cationic surfactant and an amphoteric surfactant .

The present invention is seen containing a humectant and surfactant as essential components, wherein the humectant comprises one or more polyhydric alcohols, wherein the surfactant is an anionic surfactant, a cationic surfactant An antistatic agent composition for foamable thermoplastic resin particles, which is one or more selected from the group consisting of an agent and an amphoteric surfactant .

  Further, the present invention provides an antistatic agent for foamable thermoplastic resin particles, wherein the surface of the foamable thermoplastic resin particles is coated with the antistatic agent composition for foamable thermoplastic resin particles according to the present invention described above. Provide a method.

In the antistatic method of the present invention, the expandable thermoplastic resin particles coated with the antistatic agent composition for expandable thermoplastic resin particles have a volume resistivity ρ measured in an atmosphere at a temperature of 23 ° C. and a relative humidity of 20%. It is preferably less than 1.0 × 10 ¹³ Ωcm.

  According to the present invention, it is possible to effectively prevent the foaming thermoplastic resin particles from being charged before the surface treatment process, and to reduce safety measures such as nitrogen gas replacement at the time of transfer and storage, thereby reducing costs and man-hours. An expandable thermoplastic resin particle and a production method thereof, an antistatic composition for the expandable thermoplastic resin particle, and an antistatic method for the expandable thermoplastic resin particle can be provided.

  The foamable thermoplastic resin particles of the present invention (hereinafter sometimes abbreviated as resin particles) are antistatic agents comprising a moisturizer and a surfactant as essential components on the surface of thermoplastic resin particles containing a foaming agent. It is characterized by being coated.

  Examples of the thermoplastic resin used for the expandable thermoplastic resin particles of the present invention include polystyrene resins, polyethylene resins, polypropylene resins, and polyethylene terephthalate resins. Further, examples of the polystyrene resin include homopolystyrene resin, styrene-butadiene copolymer (high impact polystyrene), styrene- (meth) acrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-modified polyethylene. Examples thereof include resins.

  Examples of the foaming agent used in the foamable thermoplastic resin particles of the present invention include hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, and cyclopentane, ethers such as dimethyl ether and diethyl ether, methanol, Various alcohols such as ethanol can be used, and among these, normal butane, isobutane, normal pentane, isopentane alone or a mixture thereof is particularly suitable. Although the addition amount of a foaming agent can be increased / decreased with the target foaming ratio of an expandable particle, generally the range of 2-15 mass parts is preferable with respect to 100 mass parts of resin.

In the foamable thermoplastic resin particles of the present invention, as an additive component other than the thermoplastic resin and the foaming agent, a cell nucleating agent, an antistatic agent, a colorant, Various additives well known in the art such as ultraviolet absorbers, flame retardants, plasticizers and the like can be added as needed, or one or more.
Examples of the cell nucleating agent include, in the impregnation method, fatty acid amides such as ethylene bis stearic acid amide and methylene bis stearic acid amide, triglycerin fatty acid ester, polyethylene wax and the like. It is preferable to add about 01 to 0.8 parts by mass.
As the cell nucleating agent, in the extrusion method, talc, calcium carbonate, magnesium carbonate, diatomaceous earth, calcium stearate, magnesium stearate, barium stearate, zinc stearate, aluminum stearate, silica, polytetrafluoroethylene resin powder, etc. In addition, sodium bicarbonate citric acid, azodicarboxylic acid amide and the like can be used, and among these, it is preferable to add 0.2 to 2.0 parts by mass of fine powder talc with respect to the resin. A cell nucleating agent used in the impregnation method may be added.

  The shape and dimensions of the expandable thermoplastic resin particles of the present invention are not particularly limited, but due to differences in each production method described later, shapes such as true spheres, cylinders, and substantially spheres are common, and true spheres or substantially spheres. In this case, the particle diameter is usually about 0.3 to 2.0 mm, and in the case of a cylindrical shape, the particle diameter is about 0.5 to 1.5 mm and the particle length is about 2.0 to 8.0 mm.

  In the present invention, the antistatic agent coated on the surface of the expandable thermoplastic resin particles includes a humectant and a surfactant as essential components, and is a liquid antistatic agent composition (for expandable thermoplastic resin particles). It is preferable to use an antistatic agent composition).

  Examples of the humectant used in the antistatic agent composition include various substances that exhibit a moisturizing action when coated on the surface of the foamable thermoplastic resin particles, such as polyhydric alcohols or solutions thereof, phosphoric acid and lactic acid. Acid solutions such as sucrose and glucose, aqueous solutions of water-absorbing polymer compounds such as polyacrylates, inorganic salt aqueous solutions such as calcium chloride, organic acid salt aqueous solutions such as sodium citrate, etc. Of these, polyhydric alcohols or solutions thereof are preferred.

  Examples of the polyhydric alcohol include glycerin, polyethylene glycol, ethylene glycol, diethylene glycol, polypropylene glycol, propylene glycol, dipropylene glycol, sorbitol, mannitol, and pentaerythritol. Among these, glycerin and polyethylene glycol are particularly preferable. . In the antistatic agent composition of the present invention, one kind selected from the various moisturizers described above, or two or more kinds can be blended.

  The humectant used in the antistatic agent composition of the present invention is preferably blended so as to be in the range of 100 to 1500 mass ppm with respect to the uncoated foamable thermoplastic resin particles. If the humectant is less than 100 ppm by mass relative to the uncoated foamable thermoplastic resin particles, the antistatic effect may be insufficient. On the other hand, when the moisturizer exceeds 1500 mass ppm with respect to the uncoated foamed thermoplastic resin particles, the stickiness increases, and the particles tend to adhere during sending or block during tank storage. More preferably, it is the range of 200-500 mass ppm.

  As the surfactant (hereinafter referred to as an activator) used in the antistatic agent composition of the present invention, one or more selected from anionic surfactants, cationic surfactants, and amphoteric surfactants may be used. Can be used.

Examples of the anionic activator include alkyl sulfate ester salts, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, and alkyl diallyl ether sulfonates.
Examples of the cationic activator include alkylamine salts and quaternary ammonium salts.
Examples of amphoteric activators include alkyl betaines, amine oxides, imidazolinium betaines, and alkyl glycines.
In addition, it is preferable to use these activators in the state melt | dissolved in suitable solvents, such as water and alcohol, Preferably water.

  The activator used in the antistatic agent composition of the present invention is preferably blended so as to be in the range of 5 to 500 ppm by mass with respect to the uncoated foamed thermoplastic resin particles. When the activator is less than 5 ppm by mass with respect to the uncoated foamable thermoplastic resin particles, the antistatic effect is insufficient. On the other hand, when the activator exceeds 500 mass ppm with respect to the uncoated foamable thermoplastic resin particles, it becomes difficult to dry the resin particles. More preferably, it is the range of 50-150 mass ppm.

  The antistatic agent composition of the present invention requires various additives such as a solvent such as water and alcohol, a flame retardant, a stabilizer, a pH adjuster, and a film forming agent in addition to the essential components of the humectant and the activator. It can be added depending on.

  The antistatic agent composition of the present invention can be coated on the surface of uncoated foamed thermoplastic resin particles using various coating methods such as coating with a mixer and coating with a spray device. Coating by spraying with a spray device is a preferred coating method because it can be continuously and uniformly coated. After coating the surface of the resin particles with the antistatic agent composition, the solvent can be removed by air-drying if necessary.

The antistatic agent composition of the present invention coats the surface of expandable thermoplastic resin particles, thereby reducing the volume resistivity of the resin particle surface and making the resin particles difficult to charge. In particular, the volume specific resistance ρ of the expandable thermoplastic resin particles can be kept below 1.0 × 10 ¹³ Ωcm even in a dry atmosphere with a relative humidity of about 20% or less. As a result, the foamable thermoplastic resin particles of the present invention obtained by coating the surface of the foamable thermoplastic resin particles with the antistatic agent composition are transferred to each other when the particles are fed in the line or stored in a tank. Nitrogen gas in the process of producing foamable thermoplastic resin particles is less likely to be charged even when rubbed, and even if granulation and storage work is performed in an air atmosphere without replacing nitrogen gas, the possibility of electrostatic ignition is reduced. Safety measures such as replacement can be reduced. In addition, it can be handled more safely than before when storing, transporting and using the product.

Next, a method for producing expandable thermoplastic resin particles according to the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing a process for producing expandable polystyrene resin particles as an embodiment of a method for producing expandable thermoplastic resin particles according to the present invention. In this embodiment, the case where the production method of the present invention is applied to the production process of expandable polystyrene resin particles by each production method of [impregnation method] and [extrusion method (strand cut method and underwater hot cut method)] is exemplified. Moreover, in this embodiment, the case where a humectant and a surfactant are included as essential components as an antistatic agent and a liquid antistatic agent composition is coated by spraying is exemplified.

[Impregnation method]
In the method of producing expandable polystyrene resin particles by the impregnation method, spherical or substantially spherical polystyrene particles prepared in advance by a suspension polymerization method are used as starting materials. An aqueous dispersant is put into an autoclave 1 equipped with a stirrer, and polystyrene particles are put therein, a foaming agent such as pentane is further introduced, and the mixture is stirred under heating and pressure to impregnate the polystyrene particles with the foaming agent. . After a predetermined time, the system is cooled, and the obtained expandable polystyrene resin particles (not shown) are transferred to the washing tank 2 and washed with water. Next, the washed expandable polystyrene resin particles are transferred to the dehydrator 3 and dehydrated and dried.

  After the expandable polystyrene resin particles are dried or in a semi-dry state, the antistatic agent composition is sprayed from the antistatic agent spray device 4 into the dehydrator 3, and the antistatic agent composition is applied to the surface of the expandable polystyrene resin particles. Cover the object. The expandable polystyrene resin particles coated with the antistatic agent composition are further dried as necessary, and then air-granulated in the granulation line 18 and sent to the sieve 5 and selected according to the particle size. The expandable polystyrene resin particles are stored in the primary tank 6. In the case of expandable polystyrene resin particles that are not coated with the antistatic agent composition at the time of this granulation and tank storage, the resin particles rub against each other and become charged, and there is a risk of electrostatic ignition of the dissipated foaming agent in an air atmosphere Therefore, it was necessary to carry out granulation and tank storage in a nitrogen gas atmosphere. On the other hand, in the present embodiment, by covering the surface of the expandable polystyrene resin particles with the antistatic agent composition, even when the resin particles rub against each other during granulation and tank storage, it becomes difficult to be charged, and the air atmosphere The risk of static electricity ignition can be greatly reduced even underneath. Therefore, in this embodiment, it becomes possible to feed and store the expandable polystyrene resin particles before the surface treatment step in an air atmosphere.

An appropriate amount of the expandable polystyrene resin particles stored in the primary tank 6 is sent to a mixer 7, and a surface treatment agent is added and mixed to coat the surface of the resin particles (surface treatment step).
Examples of the surface treating agent used here include powdery antistatic agents such as hydroxy fatty acid amide, and binding inhibitors such as zinc stearate. The amount of the surface treatment agent used is in the range of 0.02 to 2.0 parts by mass of the powdered antistatic agent and 0.05 to 0 of the binding inhibitor with respect to 100 parts by mass of the expandable polystyrene resin particles. It is preferable to be in the range of 5 parts by mass.

  In this embodiment, the surface of the expandable polystyrene resin particles before coating with the surface treatment agent is coated with the antistatic agent composition containing the above-described moisturizing agent and activator as essential components. By mixing and mixing the surface treatment agent with the expandable polystyrene resin particles, the powdery surface treatment agent is efficiently attached to and coated on the surface of the resin particles, which makes it difficult to peel off.

  After the surface treatment agent is coated on the surface of the expandable polystyrene resin particles in the mixer 7, the expandable polystyrene resin particles are sent to the secondary tank 8 and stored. Next, a suitable container is filled with expandable polystyrene resin particles and packaged to obtain a product. This product is further stored in the cold storage warehouse 9 and aged and stored.

[Extrusion method]
1. Strand cut method In the strand cut method, cylindrical (pellet) expandable polystyrene resin particles are produced. The starting polystyrene is not limited as long as it can be supplied to the extruder 10 and its shape and size are not limited. In this method, polystyrene is put into an extruder 10 equipped with a die 11 having a large number of small holes at the tip, heated and melted in the extruder 10, a foaming agent is added to this, and melted and kneaded to obtain a foaming agent. The resin is contained and extruded from the die 11 in the form of a fine string (strand), which is immediately introduced into the cooling water of the cooling water tank 12 and cured to form a strand 16.

  The strand 16 sufficiently cooled in the cooling water tank 12 is pulled up from the cooling water tank 12, sent to the pelletizer 13, and cut into pellets having a predetermined length. The obtained pellets 15 (expandable polystyrene resin particles) are introduced into the spray chamber 14, and the surface is spray-coated with the antistatic agent composition in the chamber.

  FIG. 2 shows an embodiment suitable for coating with an antistatic agent in the production method of the present invention, FIG. 2 (a) is a configuration diagram showing the arrangement state of the spray chamber 14, and FIG. 2 (b) is a charge connected to the spray chamber. It is a block diagram which shows the inhibitor spray apparatus. In the present embodiment, as shown in FIG. 2A, the two fluids attached to the side are supplied while the pellet 15 sent from the pelletizer 13 is supplied from above the spray chamber 14 and falls down the spray chamber 14. The antistatic agent mist 19 sprayed from the nozzle 22 is brought into contact, and the surface of the pellet 15 is coated with the antistatic agent composition. The pellet 15 whose surface is coated with the antistatic agent composition enters the granulation line 18 from the bottom of the spray chamber 14 and is air-granulated in the line by the granulation blower 17.

  In this embodiment, as shown in FIG. 2B, the antistatic agent spray device 4 includes a container that contains the antistatic agent composition 20, and a metering pump that quantitatively pumps the antistatic agent composition 20 from the container. 21 and a two-fluid nozzle 22 provided with a nozzle tip protruding from the side of the spray chamber 14. The two-fluid nozzle 22 has an antistatic agent introduction tube 22b connected to the metering pump 21 and an air introduction tube 22a.

  The pellets 15 whose surfaces are coated with the antistatic agent composition are air-granulated into the primary tank 6 through the granulation line 18. Thereafter, as in the case of the above-mentioned “impregnation method”, the product is manufactured through a surface treatment step of coating the surface treatment agent in the mixer 7.

2. Underwater hot cut method In the underwater hot cut method, substantially spherical expandable polystyrene resin particles are produced. As in the case of the strand cutting method, the polystyrene used as a starting material is not limited as long as it can be supplied to the extruder 1 and its shape and size are not limited. In this method, polystyrene is put into an extruder 23 equipped with a die 24 having a large number of small holes at its tip, heated and melted in the extruder 23, a foaming agent is added to this, melt-kneaded, and then the foaming agent. The resin is contained, and the resin is extruded from the die 24 into the cutting chamber 25. The cutting chamber 25 is connected to a cooling water circulation line 26 and is circulated and supplied with cooling water, and a high-speed rotary blade is provided in the chamber.

  The resin pushed out from the die 24 is cooled by contacting with the cooling water in the cutting chamber 25 and cut out by the high-speed rotary blade and flows out of the cutting chamber 25 together with the circulating water in a state of being dispersed in a substantially spherical shape. The cooling water circulation line 26 is conveyed. A water circulation pump 27 and a dehydrator 28 are connected to the cooling water circulation line 26. The expandable polystyrene resin particles 29 conveyed to the dehydrator 28 while being cooled in the cooling water circulation line 26 are separated from the cooling water, dehydrated and taken out. On the other hand, the cooling water returns to the cooling water circulation line 26.

  The expandable polystyrene resin particles 29 taken out from the dehydrator 28 are put into the spray chamber, and the surface of the expandable polystyrene resin particles 29 is applied by the antistatic agent spray device 4 shown in FIG. The antistatic composition is spray coated.

  The expandable polystyrene resin particles 29 whose surface is coated with the antistatic agent composition are air-granulated into the primary tank 6 through the granulation line 18. Thereafter, as in the case of the above-mentioned “impregnation method”, the product is manufactured through a surface treatment step of coating the surface treatment agent in the mixer 7.

In the present embodiment, by coating the surface of the expandable polystyrene resin particles with the antistatic agent composition, it becomes difficult to be charged even if the resin particles rub against each other during granulation and tank storage, even in an air atmosphere. The risk of static electricity ignition can be greatly reduced. Therefore, in this embodiment, it becomes possible to send and store the expandable polystyrene resin particles before the surface treatment step in an air atmosphere, and therefore, nitrogen gas replacement is performed at the time of sending and storing the tank. Compared with the prior art, a large amount of nitrogen gas and various devices for nitrogen gas replacement can be eliminated, and the manufacturing process can be simplified, so that the manufacturing cost of expandable polystyrene resin particles can be reduced.
In addition, since the antistatic agent can be prevented by a simple operation of spray-coating a liquid antistatic agent composition on the resin particles, the foaming property is less expensive than the conventional technology in which an antistatic agent is mixed in the expandable polystyrene resin particles. Polystyrene resin particles can be provided.

In addition, description of each embodiment of this invention mentioned above and the Example mentioned later is only an illustration, This invention is not limited only to these illustrations, A various change and correction are possible.
For example, in each of the embodiments described above, the antistatic agent composition in which a moisturizing agent and an activator are mixed in advance is coated on the surface of expandable thermoplastic resin particles such as expandable polystyrene resin particles. It is also possible to coat the resin particle surface separately.
Also, when sending and storing expandable polystyrene resin particles coated with an antistatic agent, oxygen after mixing nitrogen gas or carbon dioxide gas in the air or adsorbing oxygen in the air, not in an air atmosphere A reduced gas can also be used.

[Example 1]
After mixing 0.3 parts by mass of powder talc (trade name SP-GB, manufactured by Kihara Kasei Co., Ltd.) with 100 parts by mass of styrene resin (product of Toyo Styrol HRM-10N, manufactured by Toyo Styrene Co., Ltd.), a diameter of 90 mm Using a single screw extruder (barrel diameter (D) to effective screw length (L) ratio L / D is 35), heat melt kneading, and at the same time, pentane (i-pentane / n-pentane = 2) as a blowing agent. / 8 mixture) 6 parts by mass of the mixture was press-fitted into the extruder, the resin temperature at the extruder screw tip was maintained at 170 ° C., and the pressure at the resin introduction part to the die was maintained at 14 MPa. From a die having 150 small holes of 3.5 mm in length, extruding a foaming agent-containing molten resin into a cutting chamber connected to the die and circulating cooling water at 40 ° C., and at the same time, 10 blades in the circumferential direction The extrudate is cut at a high speed rotary cutter having, by dehydration by middle provided the dehydrator of the cooling water circulation line was continuously produce spherical expandable polystyrene resin particles having a diameter of about 1.0 mm. The discharge rate at this time is 1800 g / min. The dehydrated resin particles are continuously introduced into a spray chamber provided with a two-fluid nozzle for spraying an antistatic agent as shown in FIG. 2, and polyethylene glycol (trade name PEG # 300, manufactured by NOF Corporation) and an anionic activator. (Sodium coconut alkyl ether sulfate (C8-18): Nippon Oil & Fats Co., Ltd., trade name Persoft EK, 30% by mass aqueous solution with an effective solid content) mixed in advance at a mass ratio of 50:50 and a metering pump From the two-fluid nozzle, 1.1 g / min is sprayed onto the surface of the expandable polystyrene resin particles in the spray chamber, and the inside of the stainless steel granule having an inner diameter of 75 mm × 20 m is fed to the primary tank by air granulation. Thus, expandable polystyrene resin particles having a surface coated with an antistatic agent were obtained. About this, the antistatic property was evaluated by the method mentioned later.

[Example 2]
90 parts by mass of styrene resin (manufactured by Toyo Styrene Co., Ltd., trade name Toyostyrene HRM-10N), 10 parts by mass of carbon black masterbatch (manufactured by Sumika Color Co., Ltd., trade name black SPAB-851HC), and talc (manufactured by Kihara Kasei Co., Ltd., (Product name SP-GB) After mixing 0.4 parts by mass with a tumbler in advance, a uniaxial extruder with a bore of 90 mm (ratio L / D between barrel diameter (D) and effective screw length (L) is 35) The mixture is heated and melt-kneaded, and at the same time, 8 parts by mass of pentane (i-pentane / n-pentane = 2/8 mixture) as a foaming agent is press-fitted into the extruder, and the resin temperature at the tip of the extruder screw is 127 ° C. When the pressure of the resin introduction part to the mold is kept at 15 MPa, and extruded from a round die having 120 discharge ports with a diameter of 0.7 mm and a land length of 5 mm in a strand shape, In addition, the strand was introduced into a water tank, immediately quenched, cut into pellets with a rotary pelletizer, and colored in a black columnar polystyrene resin particle (particle length L = 3 to 4 mm, particle diameter D = 0.0). 5 to 0.7 mm) is continuously produced at a discharge rate of 1000 g / min, and continuously introduced from the outlet of the pelletizer into the spray chamber provided with the two-fluid nozzle for spraying the antistatic agent shown in FIG. Polyethylene glycol (Nippon Yushi Co., Ltd., trade name PEG # 300) and anion activator (Sodium coconut alkyl ether sulfate (C8-18: Nihon Yushi Co., Ltd., trade name Persoft EK (30% by weight effective solid content aqueous solution)) The foamed poly, which is supplied from the pelletizer at a rate of 0.6 g / min. Foam polystyrene whose surface is coated with an antistatic agent by spraying the surface of the styrene resin particles in the form of a mist, sending the inside of a stainless steel granulation tube with an inner diameter of 75 mm × 20 m to the primary tank by air feeding. Resin particles were obtained, and the antistatic property was evaluated by the method described later.

[Example 3]
An anionic activator is a cationic activator (quaternary ammonium salt: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name Catiogen ES-L (effective solid content 50 mass%) and distilled water is added to adjust the effective solid content to 30 mass%. The foamed polystyrene resin particles whose surface was coated with an antistatic agent were obtained in the same manner as in Example 2 except that the aqueous solution was changed to an aqueous solution. About this, the antistatic property was evaluated by the method mentioned later.

[Example 4]
An anionic activator is an amphoteric activator (lauryl dimethylaminoacetate betaine: manufactured by NOF Corporation, an aqueous solution in which distilled water is added to the trade name Anon BL (effective solid content 36 mass%) to adjust the effective solid content to 30 mass%). Except for the change, in the same manner as in Example 2, expandable polystyrene resin particles whose surfaces were coated with an antistatic agent were obtained. About this, the antistatic property was evaluated by the method mentioned later.

[Example 5]
Expandable polystyrene resin particles whose surfaces were coated with an antistatic agent were obtained in the same manner as in Example 2 except that polyethylene glycol was changed to glycerin (made by Junsei Chemical Co., Ltd., reagent special grade). About this, the antistatic property was evaluated by the method mentioned later.

[Example 6]
Expandable polystyrene resin particles whose surfaces were coated with an antistatic agent were obtained in the same manner as in Example 2 except that the polyethylene glycol was changed to a mixed solution of polyethylene glycol and glycerin (mass ratio 1: 1). About this, the antistatic property was evaluated by the method mentioned later.

[Example 7]
In the same manner as in Example 2, except that the mixing ratio of polyethylene glycol and an anionic surfactant was changed from 50:50 to 75:25, and the spraying amount was changed from 0.6 g / min to 0.15 g / min. Expanded polystyrene resin particles coated with an antistatic agent. About this, the antistatic property was evaluated by the method mentioned later.

[Example 8]
Example 2 except that the mixing ratio of polyethylene glycol and anionic activator was changed from 50:50 to 97.5: 2.5, and the spraying amount was changed from 0.6 g / min to 1.5 g / min. Thus, expandable polystyrene resin particles having a surface coated with an antistatic agent were obtained. About this, the antistatic property was evaluated by the method mentioned later.

[Example 9]
In the same manner as in Example 2, except that the mixing ratio of the polyethylene glycol and the anionic activator was changed from 50:50 to 7:93 and the spraying amount was changed from 0.6 g / min to 1.5 g / min. Expanded polystyrene resin particles coated with an antistatic agent. About this, the antistatic property was evaluated by the method mentioned later.

[Example 10]
Into a reactor having an internal volume of 52 L, 18 kg of distilled water, 58 g of magnesium pyrophosphate, and sodium dodecylbenzenesulfonate (product name NR-R-25, manufactured by NOF Corporation) are put in a pure amount, and the particle size is 0.00. 5.0 kg of polystyrene seed particles having a weight average molecular weight of 300000 with a weight average molecular weight of 300000 (obtained by subjecting styrene to an ordinary suspension polymerization in an aqueous medium using magnesium pyrophosphate and sodium dodecylbenzenesulfonate) Was added and stirred for suspension. Subsequently, 67.6 g of benzoyl peroxide and 16.9 g of t-butylperoxybenzoate were added to a dispersion prepared by adding 5.0 g of magnesium pyrophosphate and 1.0 g of sodium dodecylbenzenesulfonate to 1500 mL of distilled water prepared in advance. Was dissolved in 2160 g of styrene and added by stirring with a homomixer to make a suspension. This suspension was added to a reactor maintained at 75 ° C. In order to allow the polystyrene seed particles to absorb styrene and the polymerization initiator, after holding for 1 hour, styrene is continuously supplied at a rate of 5900 g / hr for 2.5 hours, and reaches 105 ° C. at the end of the supply of styrene. The reactor was warmed up. Subsequently, the temperature was raised to 120 ° C. and held for 30 minutes, and then a dispersion obtained by adding 310 g of toluene and 110 g of styrene to 2000 mL of distilled water, 6.5 g of magnesium pyrophosphate, and 0.26 g of pure dodecylbenzenesulfonate was added to a homomixer. The suspension was added to the reactor as a suspension, cooled to 100 ° C., 2265 g of butane was injected, held for 3 hours, cooled to room temperature, taken out, washed, dehydrated and dried. This operation was repeated twice to obtain 40 kg of expandable polystyrene resin particles having a particle diameter of 0.8 to 1.2 mm. Expandable polystyrene resin particles whose surfaces were coated with an antistatic agent were obtained in the same manner as in Example 2 except that the expandable polystyrene resin particles were introduced into the spray chamber at a rate of 1000 g / min. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 1]
Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that no antistatic agent was added. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 2]
Expandable polystyrene resin particles were obtained in the same manner as in Example 2 except that no antistatic agent was added. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 3]
About the expandable polystyrene resin particle produced in Example 10, antistatic property was evaluated by the method mentioned later with no processing.

[Comparative Example 4]
Expandable polystyrene resin particles whose surfaces were coated with polyethylene glycol were obtained in the same manner as in Example 2 except that the anion activator was changed to distilled water. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 5]
Expandable polystyrene resin particles whose surfaces were coated with glycerin were obtained in the same manner as in Example 5 except that the anion activator was changed to distilled water. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 6]
In the same manner as in Example 2, except that an aqueous solution prepared by adding distilled water to the anionic surfactant used in Example 2 to adjust the effective solid content to 15% by mass was sprayed at 0.6 g / min. Expanded polystyrene resin particles coated with an anionic activator. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 7]
In the same manner as in Example 1, except that an aqueous solution prepared by adding distilled water to the cation activator used in Example 3 and adjusting the effective solid content to 15% by mass was sprayed at 0.6 g / min. Expanded polystyrene resin particles coated with a cationic activator. About this, the antistatic property was evaluated by the method mentioned later.

[Comparative Example 8]
The surface was the same as in Example 1 except that distilled water was added to the amphoteric activator used in Example 4 and an aqueous solution having an effective solid content adjusted to 15% by mass was sprayed in an amount of 0.6 g / min. Expandable polystyrene resin particles coated with an amphoteric activator were obtained. About this, the antistatic property was evaluated by the method mentioned later.

  About the expandable polystyrene resin particles of Examples 1 to 10 and Comparative Examples 1 to 8 collected from the primary tank, the volume resistivity value was measured by the following method, and the antistatic property of the expandable polystyrene resin particles. Evaluated. The results are shown in Tables 1 and 2.

[Volume resistivity measurement method]
FIG. 3 is a diagram showing the configuration of the apparatus used for measuring the volume resistivity, (a) is a configuration diagram of the apparatus, and (b) is a side view of the stainless steel plate 30. In FIG. 3, reference numeral 30 is a stainless steel plate, 30a is a terminal, 31 is a fluororesin plate, 32 is an expandable polystyrene resin particle, and 33 is a hyper insulation meter. In the measuring apparatus shown in FIG. 3A, two stainless steel plates 30 are arranged opposite to each other with a fluororesin plate 31 interposed therebetween, and expandable polystyrene resin particles 32 are filled between these stainless steel plates 30. The resistance value between the steel plates 30 is measured by a hyper insulation meter 33 connected to each terminal 30a. The dimensions of the parts A to C in FIG. 3 are A = 120 mm, B = 75 mm, and C = 11 mm. The thickness of the stainless steel plate 30 is 2 mm.

About 2 kg of expandable polystyrene resin particles are put in a plastic bag, and the plastic bag is opened. After being left in a constant temperature and humidity chamber adjusted to a temperature of 23 ° C., a relative humidity of 55% and 20% for 24 hours, FIG. A container in which two stainless steel plates are insulated with a fluororesin plate is filled with resin particles, and a resistance value R between the stainless steel plates is measured using a hyper insulation meter (SM-10E manufactured by Toa Denpa Kogyo Co., Ltd.) The volume resistivity ρ of the resin particles was calculated from the following formula.
Volume resistivity ρ = 81.8 × R (Ωcm)

  The average value measured repeatedly three times for each sample was taken as the volume resistivity value. The antistatic property was evaluated according to the following criteria based on the volume resistivity measured in an atmosphere at a temperature of 23 ° C. and a relative humidity of 20%.

<Evaluation of antistatic properties>
○: Less than 1.0 × 10 ¹³ Ωcm.
×: 1.0 × 10 ¹³ Ωcm or more (there is a risk of static electricity ignition).

From the results described in Tables 1 and 2, the expandable polystyrene resin particles of Examples 1 to 10 according to the present invention were coated with an antistatic agent containing a polyhydric alcohol and an activator as a humectant on the resin particle surface. Not only showed a low volume resistivity of the order of 10 ⁸ to ¹⁰ 10 in an atmosphere of 55% relative humidity but also a volume resistance of less than 1.0 × 10 ¹³ Ωcm even in a fairly dry atmosphere of 20% relative humidity. The value is shown. When the volume specific resistance value of the expandable polystyrene resin particles is 1.0 × 10 ¹³ Ωcm or more, the resin particles are easily rubbed and charged when the resin particles are fed and stored in the tank, and the resin particles dissipate. Although combustible foaming agents and the like may ignite electrostatically, the expandable polystyrene resin particles of Examples 1 to 10 according to the present invention are less likely to cause such electrostatic ignition and are handled in a dry air atmosphere. be able to.

On the other hand, each of the expandable polystyrene resin particles of Comparative Examples 1 to 3 in which nothing is coated on the surface of the expandable polystyrene resin particles, and Comparative Examples 4 and 5 in which the resin particle surface is coated only with a polyhydric alcohol as a moisturizing agent. Shows a volume resistance value of 1.0 × 10 ¹³ Ωcm or more even in an atmosphere with a relative humidity of 55%, and in a dry air atmosphere, there is a risk of static electricity ignition during grain feeding. It is necessary to replace the atmosphere with nitrogen gas.
Further, the expandable polystyrene resin particles of Comparative Examples 6 to 8 in which only the active agent was coated on the surface of the expandable polystyrene resin particles showed a volume specific resistance value as low as 10 ⁹ order in an atmosphere of 55% relative humidity. The volume resistivity increases rapidly to the order of 10 ¹³ in an atmosphere with a relative humidity of 20%, and in a dry air atmosphere, there is a risk of static electricity ignition at the time of granulation. There is a need to.

It is a block diagram which shows one Embodiment of the manufacturing method of the expandable thermoplastic resin particle which concerns on this invention. It is a block diagram which shows embodiment suitable for the coating of the antistatic agent in the manufacturing method of this invention. It is a block diagram explaining the measuring method of the volume resistivity of the expandable thermoplastic resin particle performed in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Autoclave, 2 ... Washing tank, 3 ... Dehydrator, 4 ... Antistatic agent spray device, 5 ... Sieve machine, 6 ... Primary tank, 7 ... Mixer, 8 ... Secondary tank, 9 ... Cold storage warehouse, 10 , 23 ... Extruder, 11, 24 ... Die, 12 ... Cooling water tank, 13 ... Pelletizer, 14 ... Spray chamber, 15 ... Pellet (expandable thermoplastic resin particles), 16 ... Strand, 17 ... Feeding blower, 18 ... 20 ... Antistatic agent mist, 20 ... Antistatic agent composition, 21 ... Metering pump, 22 ... Two-fluid nozzle, 25 ... Cutting chamber, 26 ... Cooling water circulation line, 27 ... Water circulation pump, 28 ... Dehydrator 29, 32 ... expandable polystyrene resin particles (expandable thermoplastic resin particles), 30 ... stainless steel plate, 31 ... fluororesin plate, 33 ... ultra-insulation meter.

Claims (6)

A surface is coated with an antistatic agent containing a humectant and a surfactant as essential components, the humectant contains one or more polyhydric alcohols, and the surfactant is an anionic surfactant. 1 or 2 or more types selected from the group consisting of a cationic surfactant and an amphoteric surfactant . 2. The foamable thermoplastic resin particles according to claim 1, wherein the surface of the powdery surface treatment agent is coated on the surface after the antistatic agent is coated. Surface treatment with an antistatic agent containing a moisturizing agent and a surfactant as essential components in a method for producing foamable thermoplastic resin particles, which is produced by applying a surface treatment step to coat the foamable thermoplastic resin particles with a surface treatment agent look including the step of coating the step before the expandable thermoplastic resin particles, wherein the humectant comprises one or more polyhydric alcohols, wherein the surfactant is an anionic surfactant, a cationic surfactant 1 or 2 or more types selected from the group which consists of an amphoteric surfactant , The manufacturing method of the foamable thermoplastic resin particle characterized by the above-mentioned . Look including a humectant and surfactant as essential components, wherein the humectant comprises one or more polyhydric alcohols, wherein the surfactant is an anionic surfactant, cationic surfactant, amphoteric surfactant An antistatic agent composition for expandable thermoplastic resin particles, wherein the composition is one or more selected from the group consisting of agents. An antistatic method for expandable thermoplastic resin particles, wherein the surface of the expandable thermoplastic resin particles is coated with the antistatic agent composition for expandable thermoplastic resin particles according to claim 4 . For the expandable thermoplastic resin particles coated with the antistatic agent composition for expandable thermoplastic resin particles, the volume resistivity ρ measured in an atmosphere at a temperature of 23 ° C. and a relative humidity of 20% is less than 1.0 × 10 ¹³ Ωcm. The antistatic method for foamable thermoplastic resin particles according to claim 5, wherein:

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