JP6770838B2 - Manufacturing method of foamable styrene resin particles - Google Patents

Description

The present invention relates to a method for producing foamable styrene resin particles, a method for producing a foamed molded product in a styrene resin mold, and a foamed molded product in a styrene resin mold.

A method for producing effervescent styrene resin particles having excellent impact resistance such as HIPS (impact resistant polystyrene) by a suspension (seed) polymerization method is known. However, in order to blacken the foamable styrene resin particles, if carbon black is added at the time of polymerization to obtain blackened foamable styrene resin particles, the amount of residual styrene monomer increases and the polymerization stability is impaired. Therefore, it has been difficult to produce blackened foamable styrene resin particles having impact resistance. That is, according to the seed polymerization method, in general, only foamable styrene resin particles having a natural color (a color based on the resin itself and often white) could be produced.

On the other hand, a resin composition containing a polystyrene resin, an additive, and a volatile foaming agent is melt-kneaded in an extruder, and the obtained melt-kneaded product is extruded from a die into pressurized water and extruded. A method for producing substantially unfoamed foamable styrene resin particles (hereinafter referred to as a quenching method) is also known.

According to the quench method, impact-resistant styrene-based resin such as HIPS and carbon black can be melt-kneaded, so that blackened foamable styrene-based resin particles having impact resistance can be produced. ..

However, the effervescent styrene resin particles produced by the quench method tend to vary in weight and size per grain, and the effervescent styrene resin particles tend to coalesce (aggregate) with each other during production. When the styrene-based resin pre-foamed particles obtained by pre-foaming such foamable styrene-based resin particles are foam-molded in the mold, color unevenness and particle gaps are conspicuous in the obtained styrene-based resin in-mold foam molded product. The surface property tends to be poor, and it is difficult to achieve a beautiful and uniform blackening surface.

In addition, there is a problem that the impact resistance (break height) decreases when carbon black is added, and the inside of the styrene resin mold produced from the impact resistant natural-colored foamable styrene resin particles obtained by the polymerization method. It was difficult to develop the same impact strength as the foam molded product.

Patent Document 1 describes that an impact-resistant styrene resin is produced by a quenching method. More specifically, in Patent Document 1, a rubber-modified polystyrene-based resin composed of a continuous phase of polystyrene-based resin and a dispersed phase of butadiene-based rubber particles is mixed with a foaming agent in a heat-melted state in an extruder to obtain a molten mixture. Step, A step of holding the melt mixture in an extruder under a predetermined pressure at a predetermined temperature or higher for a predetermined time or longer (15 minutes or longer) to obtain a rubber-modified polystyrene resin impregnated with a foaming agent, a step of obtaining a rubber-modified polystyrene resin impregnated with a foaming agent. A method for producing polystyrene-based foamed particles is described, which comprises a step of extruding a modified polystyrene resin, cutting it, and granulating it to obtain foamable particles, and a step of heating the foamable particles.

Further, Patent Document 2 describes a method for producing foamable polystyrene-based resin particles having excellent impact resistance. More specifically, in Patent Document 2, a physical foaming agent is press-fitted and kneaded into a polystyrene-based resin melted containing a colorant in a resin supply device, and a molten resin containing a foaming agent is attached to the tip of the resin supply device. The extruded product is extruded directly into the cooling liquid from the small holes of the die, and the extruded product extruded into the cooling liquid is cut with a rotary blade in the cooling liquid, and the extruded product is cooled and solidified by contact with the liquid. A method for producing foamable polystyrene-based resin particles for obtaining foamable polystyrene-based resin particles is described.

Japanese Unexamined Patent Publication No. 9-104782 Japanese Unexamined Patent Publication No. 2014-095064

However, Patent Document 1 does not disclose any suggestion or disclosure regarding the inclusion of carbon black in an impact-resistant styrene resin such as HIPS, and also includes agglomeration that occurs when carbon black is added in the quench method. There is no description about color unevenness, and therefore there is no description about the technology for eliminating it. Further, there is no description about the problem that the impact resistance is lowered as compared with the polymerization method, and of course, there is no description about the solution technique. Further, it is necessary to hold the molten mixture in the extruder for 15 minutes or more, which remains a problem of inferior productivity, and there is also a problem that the resin deteriorates due to the long holding time and the impact resistance strength tends to decrease.

Patent Document 2 states that carbon black is contained in an impact-resistant styrene resin such as HIPS, and agglomeration is likely to occur in the blackened foamable styrene resin particles obtained by the quench method, and the obtained styrene resin is obtained. There is no description about the difficulty of uniform and beautiful blackening such as color unevenness and particle gaps in the foamed molded product in the mold, and therefore there is no description about the solution technique. Further, in the quench method, there is a problem that the impact strength (break height) is lowered when carbon black is simply added to the impact-resistant styrene resin such as HIPS, and the impact-resistant styrene resin type obtained from the polymerization method is used. There is no description that it is difficult to develop the impact strength equivalent to that of the inner foam molded product (natural color), and of course, there is no description about the solution technology.

Therefore, an object of the present invention is a method for producing foamable styrene-based resin particles capable of stably obtaining foamable styrene-based resin particles from an impact-resistant styrene-based resin containing carbon black by a quenching method, a styrene-based resin type. It is an object of the present invention to provide a method for producing an inner foam molded product and a styrene-based resin mold inner foam molded product.

Another object of the present invention is a method for producing foamable styrene resin particles, which can obtain a carbon black-containing styrene resin in-mold foam molded article having a beautiful surface with improved color unevenness and particle gaps, styrene. It is an object of the present invention to provide a method for producing an in-foam molded product in a based resin mold and a foamed molded product in a styrene resin mold.

Still another object of the present invention is carbon black-containing styrene resin in-mold foam molding having impact resistance equivalent to that of an impact-resistant styrene resin in-mold foam molded product which is a natural color obtained by a polymerization method. It is an object of the present invention to provide a method for producing foamable styrene resin particles capable of obtaining a body, a method for producing a foamed molded product in a styrene resin mold, and a foamed molded product in a styrene resin mold.

According to the present invention, an impact-resistant styrene resin, carbon black, and a foaming agent are melt-kneaded to form a molten resin, and the molten resin is extruded into pressurized water through a die having small pores and extruded into pressurized water. A method for producing foamable styrene-based resin particles that cuts molten resin with a rotary cutter, in which the amount of molten resin that passes through the small holes per hour is 1.0 kg / hole or more and 2.5 kg / hole or less. Provided is a method for producing foamable styrene resin particles in which the pressure of the pressurized water is 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less and the temperature of the pressurized water is 50 ° C. or more and 70 ° C. or less. Will be done.

When a carbon black-containing impact-resistant styrene resin is produced by the quench method, the discharge rate of the molten resin passing through the small pores per hour is 1.0 kg / hole or more, 2.5 kg / hole or less, and pressurized water. By setting the pressure of 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less and the temperature of the pressurized water to 50 ° C or more and 70 ° C or less, there is little variation in the size of the particles, and the foaming styrene type Blackened effervescent styrene resin particles having a desired appearance without agglomeration between resin particles can be stably produced, and have a beautiful surface with improved color unevenness and particle gaps, and have a sufficient impact. A styrene-based resin mold in-foam molded product having strength can be finally obtained.

The residence time, which is the time spent for melt-kneading, is preferably less than 15 minutes.

It is also preferable that the flexural modulus of the impact-resistant styrene resin is 2000 MPa or more and 2300 MPa or less.

It is also preferable to melt-knead the impact-resistant styrene resin, carbon black, a foaming agent, and general-purpose polystyrene to obtain a molten resin.

In this case, it is more preferable that general-purpose polystyrene is contained in an amount of 0.15 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin.

It is also preferable that carbon black is contained in an amount of 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin.

According to the present invention, (a) impact-resistant styrene resin, carbon black, and foaming agent are melt-kneaded to form a molten resin, and the molten resin is extruded into pressurized water through a die having small pores to obtain pressurized water. 2. In the process of manufacturing foamable styrene resin particles that cuts the molten resin extruded into the resin with a rotary cutter, the discharge rate of the molten resin passing through the small pores per hour is 1.0 kg / hole or more. Foamable styrene resin particles having a pressure of 5 kg / hole or less, a pressure of pressurized water of 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less, and a temperature of pressurized water of 50 ° C. or more and 70 ° C. or less. And (b) a step of heating the produced foamable styrene resin particles to produce styrene resin pre-foamed particles, and (c) in-mold foaming of the produced styrene resin pre-foamed particles. Provided is a method for producing a styrene resin in-mold foam molded product, which comprises a step of molding and producing a styrene-based resin in-mold foam molded product.

According to the present invention, the impact-resistant styrene resin and carbon black having a ratio of 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin are further contained. The following formula (1), which is the relational expression between the foaming ratio of the molded product and the half-break height.
Half fracture height (cm) ≧ -27.52 ln (molded foam expansion ratio (times)) +
123.26 ... (1)
(However, ln is the natural logarithm)
A styrene-based resin in-mold foam molded product satisfying the above requirements is provided.

The flexural modulus of the impact-resistant styrene resin is preferably 2000 MPa or more and 2300 MPa or less.

It is also preferable that it is a helmet core material.

According to the present invention, there is little variation in the size of the effervescent styrene resin particles, and there is no agglomeration between the effervescent styrene resin particles, and the effervescent styrene resin containing blackened carbon black has a desired appearance. Particles can be stably produced, color unevenness and particle gaps are improved, the surface is beautiful, and sufficient impact resistance (natural color styrene resin obtained from impact resistant styrene resin by polymerization method). A carbon black-containing styrene resin in-mold foam molded product having the same impact resistance as the in-mold foam molded product can be finally obtained. As described above, since it is possible to obtain a carbon black-containing styrene resin in-mold foam molded product that is blackened and has excellent impact resistance (impact resistance), white color that is conspicuously colored over time due to stains, light deterioration, etc. Carbon black-containing styrene-based products that can be used in applications (helmet core materials, etc.) where a black (or gray) -based molded product is disliked and the appearance of the system is disliked, enabling easier and more stable production than before. The foamed molded product in the resin mold can be provided for a wide range of applications.

It is a graph which shows the relationship between the foaming ratio of a molded product, and the half fracture height in a reference example.

Hereinafter, the method for producing the foamable styrene resin particles of the present invention, the method for producing the foamed molded product in the styrene resin mold, and the foamed molded product in the styrene resin mold will be described with reference to the embodiments.

[Effervescent styrene resin particles]
The foamable styrene-based resin particles of the present invention contain carbon black and a foaming agent in impact-resistant styrene-based resin particles. In addition, other additives can be contained, if necessary.

Hereinafter, the essential components and optional components contained in the effervescent styrene resin particles of the present invention will be described in more detail.

(Impact resistant styrene resin)
The impact-resistant styrene-based resin (HIPS) used in the present invention is not particularly limited, and conventionally known ones having improved impact resistance by adding a rubber component to the styrene-based resin can be used. Specifically, for example, a method of mechanically blending a block copolymer of styrene and butadiene with a polystyrene resin (see JP-A-47-17465, JP-A-54-158467, etc.), a conjugated diene system. An impact-resistant styrene-based resin can be obtained by a method obtained by polymerizing a styrene monomer in the presence of polymer particles, but a commercially available impact-resistant styrene-based resin can also be used. In addition, acrylic rubber-reinforced polystyrene can also be used.

Although the flexural modulus of such impact-resistant styrene-based resin is not particularly limited, from the viewpoint of excellent moldability and impact-resistant strength of the obtained styrene-based resin in-mold foam molded product, 2000 MPa or more and 2300 MPa or less. Is preferable. The flexural modulus is a value measured according to ISO 178.

The melt mass flow rate of the impact-resistant styrene-based resin is not particularly limited, but from the viewpoint of excellent moldability and impact resistance of the obtained styrene-based resin in-mold foam molded product, 1 g / 10 minutes or more. It is preferably 7 g / 10 minutes or less. The melt mass flow rate is a value measured according to ISO 1133.

(Carbon black)
The carbon black used in the present invention is not particularly limited, and conventionally known carbon blacks can be used, and commercially available carbon blacks can also be used.

Specifically, Ketjen black, thermal black, furnace black, channel black, lamp black, gas black, roller black, acetylene black and the like can be used.

The particle size of such carbon black is not particularly limited, but the particle size is preferably 0.1 to 10000 nm. A carbon black having such a particle size range is easy to handle, has good dispersibility in a resin, and tends to be less likely to cause color unevenness in a foamed molded product in a styrene resin mold.

The amount of carbon black added is not particularly limited and may be adjusted as appropriate. However, the formability of the obtained styrene-based resin in-mold foam molded product is uniformly blackened (grayed), and the surface is beautiful and resistant. From the viewpoint of excellent impact strength, it is preferable that carbon black is contained in an amount of 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact resistant styrene resin, and 0.5 parts by weight or more. It is more preferably contained in an amount of 7 parts by weight or less, and most preferably contained in an amount of 1 part by weight or more and 6 parts by weight or less.

(Foaming agent)
The foaming agent used in the present invention is not particularly limited, but a hydrocarbon having 4 to 5 carbon atoms is desirable. Hydrocarbons having 4 to 5 carbon atoms can easily obtain sufficient foaming power and can easily undergo high foaming. Examples of the hydrocarbon having 4 to 5 carbon atoms include hydrocarbons such as normal butane, isobutane, normal pentane, isopentane, neopentane, and cyclopentane. One of these may be used alone, or two or more thereof may be used in combination.

The amount of the foaming agent added in the present invention is preferably 2 parts by weight or more and 15 parts by weight or less, and more preferably 4 parts by weight or more and 9 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin. Most preferably, it is 5 parts by weight or more and 8 parts by weight or less.

By setting the amount of the foaming agent added within the above range, it becomes easier to manufacture a styrene resin in-mold foam molded product having excellent impact resistance, and high foaming becomes possible, resulting in a high foaming ratio of 50 times or more. It will also be possible to manufacture foamed molded products in styrene resin molds.

(General-purpose polystyrene)
The general-purpose polystyrene (GPPS) used in the present invention is not particularly limited, and a styrene homopolymer commercially available as general-purpose polystyrene can be used.

The carbon black-containing styrene resin in-mold foam molded product obtained by the present invention is a styrene-based resin in-mold foam molded product having a beautiful surface with improved color unevenness and particle gaps. By using general-purpose polystyrene in combination with the impact-resistant styrene resin, the surface beauty is further improved and the impact resistance tends to be improved, which is a preferable embodiment.

The amount of such general-purpose polystyrene added is not particularly limited, but from the viewpoint of excellent surface beauty and impact resistance, the general-purpose polystyrene is added to 100 parts by weight of the impact-resistant styrene resin. It is preferably contained in an amount of 15 parts by weight or more and 15 parts by weight or less, more preferably 0.5 parts by weight or more and 10 parts by weight or less, and more preferably 1 part by weight or more and 8 parts by weight or less. Is most preferable.

Carbon black and general-purpose polystyrene may be added to the impact-resistant styrene resin separately, but a masterbatch resin composed of carbon black and general-purpose polystyrene may be prepared in advance, and this masterbatch resin may be used for impact resistance. It is preferable to add it to a styrene resin. According to such a method, the handleability is improved, the productivity is improved, and the surface beauty of the foamed molded product in the styrene resin mold tends to be further improved.

The concentration of carbon black in such a masterbatch resin is not particularly limited, but from the viewpoint of further improving the surface beauty and the impact resistance, 10 carbon blacks are used in 100% by weight of the masterbatch resin. It is preferably 20% by weight or more and 70% by weight or less, and more preferably 20% by weight or more and 60% by weight or less.

(Other additives)
The effervescent styrene resin particles of the present invention are, if necessary, a flame retardant, a flame retardant aid, a radiant heat transfer inhibitor, a heat stabilizer, a nucleating agent, and a processing aid, as long as the effects of the present invention are not impaired. It may contain one or more other additives selected from the group consisting of agents, light resistance stabilizers, foaming aids, antistatic agents, and colorants such as pigments. The amount of the other additive added in the present invention is preferably 0 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin.

Other additives will be further described.

(Flame retardants)
The flame retardant used in the present invention is not particularly limited, and a bromine-based flame retardant, a phosphorus-based flame retardant, a nitrogen-based flame retardant, a silicon-based flame retardant, etc. can be used. From the viewpoint of flame retardancy, a bromine-based flame retardant can be used. Flame retardants are preferred, for example 2,2-bis [4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl] propane (also known as tetrabromobisphenol A-bis (2,3-)). Dibromo-2-methylpropyl ether)), 2,2-bis [4- (2,3-dibromopropoxy) -3,5-dibromophenyl] propane (also known as tetrabromobisphenol A-bis (2,3-dibromo)) Brominated butadiene-vinyl aromatic hydrocarbon copolymers such as propyl ether)), hexabromocyclododecane, or brominated styrene-butadiene copolymers (for example, disclosed in Japanese Patent Application Laid-Open No. 2009-516019), And so on.

One of these brominated flame retardants may be used alone, or two or more thereof may be used in combination.

The amount of the brominated flame retardant added in the present invention is not limited, but in order to exhibit good flame retardancy, 0.5 parts by weight or more and 10 parts by weight or more with respect to 100 parts by weight of the impact-resistant styrene resin. It is preferably less than a part by weight.

(Flame retardant aid)
The flame-retardant aid used in the present invention is not particularly limited, but a flame-retardant aid (radical generator) that decomposes by heat to generate radicals is preferably used.

Examples of such a flame retardant aid include di-t-butyl peroxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and the like. Examples thereof include radical generators such as poly-1,4-isopropylbenzene, and organic nitroxy radical compounds.

From the viewpoint of improving flame retardancy, the amount of the flame retardant aid added in the present invention is preferably 0.01 parts by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin.

(Radiation heat transfer inhibitor)
The radiant heat transfer inhibitor used in the present invention is not particularly limited, but a substance having a property of reflecting, scattering or absorbing light in the near infrared or infrared region (for example, a wavelength region of about 800 to 3000 nm) is preferable. For example, graphite, graphene, activated carbon, titanium oxide, metallic aluminum and the like can be mentioned.

The amount of such a radiant heat transfer inhibitor added is preferably 1 part by weight or more and 9 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin from the viewpoint of improving the heat insulating property.

(Heat stabilizer)
The heat stabilizer used in the present invention is not particularly limited, and a commercially available heat stabilizer can be used, for example, tetrakis (2,2,6,6-tetramethylpiperidyloxycarbonyl) butane, bis ( 2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, 3,9-bis (2,4-di-tert-butylphenoxy) -2,4,8,10-tetraoxa-3 , 9-Diphosphaspiro [5.5] undecane, pentaerythritol tetrakis [3- (3', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate], and cresol novolac type epoxy resin. It is desirable that there is at least one species.

The amount of the heat stabilizer added in the present invention is impact-resistant styrene from the viewpoint of suppressing the thermal decomposition of the impact-resistant styrene resin or also suppressing the decomposition of the flame retardant when the flame retardant is used in combination. It is preferably 0.001 part by weight or more and 0.7 part by weight or less with respect to 100 parts by weight of the based resin.

(Nucleating agent)
Examples of the nucleating agent used in the present invention include inorganic compounds such as silica, calcium silicate, wallastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogen carbonate, and talc, and methyl methacrylate. Copolymer, polymer compound such as ethylene-vinyl acetate copolymer resin, olefin wax such as polyethylene wax, methylene bisstearyl amide, ethylene bisstearyl amide, hexamethylene bispalmitate amide, or ethylene bisolein Examples thereof include fatty acid bisamide such as acid amide.

The amount of the nucleating agent added in the present invention is preferably 0 parts by weight or more and 3 parts by weight with respect to 100 parts by weight of the impact-resistant styrene resin from the viewpoint that the average cell diameter (average cell diameter) tends to be uniform. It is as follows.

(Additives other than the above)
In the present invention, a processing aid, a light resistance stabilizer, a foaming aid, an antistatic agent and the like can be further added as long as the effects of the present invention are not impaired.

Examples of the processing aid include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, liquid paraffin and the like.

Examples of the light resistance stabilizer include the above-mentioned hindered amines, phosphorus stabilizers, epoxy compounds, phenolic antioxidants, nitrogen stabilizers, sulfur stabilizers, benzotriazoles and the like.

As the foaming aid, a solvent having a boiling point of 200 ° C. or lower under atmospheric pressure can be preferably used, and for example, an aromatic hydrocarbon such as styrene, toluene, ethylbenzene, or xylene, or an alicyclic such as cyclohexane or methylcyclohexane. Examples thereof include formula hydrocarbons and acetates such as ethyl acetate and butyl acetate.

As the antistatic agent and the colorant, those used in various resin compositions can be used without particular limitation.

[Manufacturing method of foamable styrene resin particles]
In the method for producing foamable styrene resin particles in the present invention, an impact-resistant styrene resin, carbon black, and a foaming agent are melt-kneaded to obtain a molten resin, and the molten resin is passed through a die having small pores in pressurized water. This is a method for producing foamable styrene resin particles that is extruded into a pressurized water and cuts the molten resin extruded into pressurized water with a rotary cutter. The amount of molten resin that passes through the small pores per hour is 1.0 kg / hole or more. , 2.5 kg / hole or less, the pressure of the pressurized water is 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less, and the temperature of the pressurized water is 50 ° C. or more and 70 ° C. or less.

In carrying out this manufacturing method, for example, an apparatus in which a main extruder and a die are continuously connected can be adopted, and an impact-resistant styrene resin, carbon black, and a foaming agent are used by the main extruder. It is melt-kneaded to obtain a molten resin. It is also possible to provide a static mixer, a static cooler, a gear pump, continuous piping, a screen changer, a diverter valve, or the like between the main extruder and the die.

A known main extruder can be used. For example, a single-screw extruder or a twin-screw extruder can be used, and the screw rotation direction when the twin-screw extruder is adopted is the same direction. It does not matter whether it is in a different direction. Further, one or two or more main extruders may be used. For example, when two machines are used, it is possible to adopt a tandem type in which the first extruder and the second extruder are connected in series. Hereinafter, such a first extruder and a second extruder are referred to. Together, it is called the main extruder. If necessary, continuous piping can be used to connect the first extruder and the second extruder.

The continuous piping is useful for facilitating the connection when connecting an extruder, a static mixer, a static cooler, a gear pump, a screen changer, a diverter valve, or the like in an appropriate combination.

In the method for producing the foamable styrene resin particles of the present invention, the main extruder can be used as described above, but carbon black, general-purpose polystyrene or other additives are previously blended with the impact-resistant styrene resin. It can be added to the main extruder at the same time as the impact-resistant styrene resin. Further, an addition port different from the impact-resistant styrene resin addition port may be provided in the main extruder and put into the main extruder separately from the impact-resistant styrene resin addition port.

The molten resin melt-kneaded by the main extruder can have a resin temperature of 100 ° C. or higher and 300 ° C. or lower, but from the viewpoint of suppressing unexpected coloring of the foamable styrene-based resin particles, foaming in the styrene-based resin mold. From the viewpoint of suppressing a decrease in mechanical strength of the molded product and from the viewpoint of productivity, the temperature is preferably 150 ° C. or higher and lower than 200 ° C.

The resin temperature of the molten resin in the present invention refers to the resin temperature of the molten resin from the main extruder to the die, and does not refer to the resin temperature of the molten resin passing through the die described later. It does not mean the resin temperature of the molten resin extruded from the die.

In the present invention, the foaming agent may be added directly to the main extruder or may be added on the way from the main extruder to the die.

When the foaming agent is added directly to the main extruder, the impact-resistant styrene resin is easily plasticized in the main extruder, so that the resin temperature in the main extruder can be lowered and the resin is deteriorated by heat. It becomes easier to suppress. Further, since the operation with a low screw torque of the main extruder can be performed, there is an advantage that power consumption can be suppressed and that consumption of main extruder components such as screws is less likely to proceed.

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

In the method for producing the foamable styrene resin particles of the present invention, a method of extruding the molten resin into pressurized water through a die having small pores is adopted.

In this case, since the die comes into direct contact with pressurized water, if the set temperature of the die is too low, the small holes may be clogged with resin. To avoid this, the set temperature of the die is 200 ° C or higher, 300. The temperature is preferably 230 ° C or higher, more preferably 230 ° C or higher and 270 ° C or lower. At such a set temperature, foamable styrene resin particles having a desired particle shape can be easily obtained without clogging the small pores. In addition, the foamable styrene resin particles do not unintentionally foam, the viscosity of the molten resin extruded from the die becomes appropriate, and the molten resin does not wind around the rotary cutter, resulting in stable foaming. It becomes possible to produce sex styrene resin particles.

As described above, since the die comes into direct contact with the pressurized water, it is considered that the resin temperature of the molten resin passing through the die is substantially lower than the set temperature of the die due to the cooling effect of the pressurized water. Further, even when the resin temperature of the molten resin passing through the die exceeds 200 ° C., the time required for passing through the die is very short. For this reason, even if the set temperature of the die is 200 ° C. or higher, problems such as unexpected coloring of the foamable styrene resin particles or a decrease in mechanical strength of the foamed molded product in the styrene resin mold become apparent. It is thought that it will not change.

The number of small pores of the die having small pores used in the method for producing foamable styrene resin particles of the present invention may be one, but from the viewpoint of productivity, it is preferable to have a plurality of small pores. The shape and size of the small holes are not particularly limited, and examples thereof include small holes having a diameter of 0.3 mm or more and 2.0 mm or less, and more preferably 0.4 mm or more and 1.0 mm or less. Be done.

In the present invention, the discharge amount of the molten resin passing through the small holes per hour is 1.0 kg / hole or more and 2.5 kg / hole or less. If it is less than 1.0 kg / hole, the small holes of the die are likely to be clogged, and the productivity tends to decrease. On the other hand, if it exceeds 2.5 kg / hole, the molten resin tends to generate heat by shearing, and resin deterioration tends to be promoted, and the obtained foamable styrene resin particles are partially foamed, so that the styrene resin reserve When the foamed particles are used, the magnification varies widely, and the moldability when producing the foamed molded product in the styrene resin mold tends to decrease. In this case, the surface beauty of the styrene-based resin in-mold foam molded product at the time of in-mold foam molding tends to decrease, and / or the impact resistance tends to decrease. Further, when the molten resin extruded from the small holes of the die is cut by the rotary cutter, troubles such as the molten resin being wound around the rotary cutter are likely to occur.

From the viewpoint of further improving productivity, surface beauty, and impact resistance, the discharge rate of the molten resin passing through the small holes per hour is 1.4 kg / hole or more and 2.3 kg / hole or less. Is more preferable, and 1.6 kg / hole or more and 2.1 kg / hole or less are further preferable.

The pressure of the pressurized water in the present invention is 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less. If the pressure is less than 0.8 MPa (gauge pressure), the obtained foamable styrene-based resin particles are partially foamed, and the magnification varies greatly when the styrene-based resin pre-foamed particles are used, and a styrene-based resin in-mold foam molded product is manufactured. There is a tendency that the moldability is lowered, the surface beauty of the foamed molded product in the styrene resin mold is lowered, and / or the impact resistance is lowered. If it exceeds 1.2 MPa (gauge pressure), the small holes of the die are likely to be clogged, and the productivity tends to decrease.

From the viewpoint of further improving productivity, surface beauty, and impact resistance, the pressure of the pressurized water is more preferably 0.9 MPa (gauge pressure) or more and 1.1 MPa (gauge pressure) or less.

The temperature of the pressurized water in the present invention is 50 ° C. or higher and 70 ° C. or lower. If the temperature is lower than 50 ° C., the small holes of the die are likely to be clogged, and the productivity tends to decrease. On the other hand, when the temperature exceeds 70 ° C., the obtained foamable styrene-based resin particles are easily coalesced (aggregated), and when the styrene-based resin pre-foamed particles are obtained as they are and foam-molded in the mold, the mold filling property is improved. The moldability tends to decrease due to the decrease. In addition, the obtained foamable styrene-based resin particles are partially foamed, and the magnification variation when the styrene-based resin pre-foamed particles is increased becomes large, so that molding is performed when the styrene-based resin in-mold foam molded product is manufactured. The sex tends to decrease. In this case, the surface beauty of the styrene-based resin in-mold foam molded product at the time of in-mold foam molding tends to decrease, and / or the impact resistance tends to decrease.

The temperature of the pressurized water is more preferably 55 ° C. or higher and 70 ° C. or lower from the viewpoint of further improving productivity and further improving surface beauty and impact resistance.

In the present invention, the time (residence time) spent for melt-kneading is preferably less than 15 minutes. If it is less than 15 minutes, the deterioration of the resin is suppressed, the surface beauty of the styrene-based resin in-mold foam molded product at the time of in-mold foam molding is improved, and the impact resistance strength is easily improved.

From the viewpoint of further improving the surface beauty and impact resistance, the residence time is more preferably 10 minutes or less, and most preferably 6 minutes or less.

The residence time can be adjusted, for example, by adopting a twin-screw extruder as the main extruder and appropriately adjusting the screw rotation speed of the twin-screw extruder. Further, the residence time can be adjusted by adopting main extruders having different L / D. Furthermore, by appropriately providing a static mixer, static cooler, gear pump, continuous piping, screen changer, diverter valve, etc. between the main extruder and the die, and adjusting the distance between the main extruder and the die as appropriate, the residence time can also be adjusted. Can be adjusted.

The residence time can be measured as follows. That is, after determining the equipment operating conditions and equipment configuration as described above in order to adjust the residence time, the equipment is supplied with impact-resistant styrene resin for operation, and then the molten resin is discharged from the die tip. There is a method of measuring the time until. In addition, the time from the time when the impact-resistant styrene resin that does not contain carbon black is supplied in advance and operated and then switched to the mixed resin that contains carbon black until the black resin is discharged from the tip of the die is measured. The method and the like can also be mentioned.

The electrical conductivity of the pressurized water used in the method for producing the foamable styrene resin particles of the present invention is preferably 0.00 mS / m or more and 25 mS / m or less. By setting the electric conductivity within this range, even if the impact-resistant styrene resin is thermally decomposed to some extent to generate decomposition gas, the effect of reducing the offensive odor of the pressurized water caused by the decomposition gas can be obtained. ..

There is no particular limitation on the method for obtaining pressurized water having such an electric conductivity, and it can be produced by a conventionally known technique such as a distillation method or an ion exchange resin method. Further, it is also possible to adjust the electric conductivity by appropriately mixing pressurized water having various electric conductivitys.

In the method for producing foamable styrene-based resin particles of the present invention, the cutting device for cutting the molten resin extruded into pressurized water is not particularly limited, but for example, it is cut by a rotary cutter in contact with a die lip to form small spheres. Examples thereof include a device that is transferred to a centrifugal dehydrator to dehydrate and consolidate without foaming in pressurized water. The pressurized water is preferably recycled from the viewpoint of suppressing the generation of wastewater.

[Styrene-based resin pre-foamed particles]
The styrene-based resin pre-foamed particles of the present invention can be obtained by foaming the foamable styrene-based resin particles of the present invention described above by a method described later, and can be foamed by a method for producing styrene-based resin pre-foamed particles described later or the like. Styrene-based resin particles are foamed approximately 3 times or more and 110 times or less.

The content of carbon black, general-purpose polystyrene, and other additives in the obtained styrene-based resin pre-foamed particles is, for example, the content of carbon black, general-purpose polystyrene, and other additives in the foamable styrene-based resin particles. It can be adjusted by appropriately selecting the amount. However, the content ratio of carbon black, general-purpose polystyrene, and other additives in the styrene-based resin pre-foamed particles is determined by the volatilization of the foaming agent in the pre-foaming step described later, and the carbon in the foamable styrene-based resin particles. It tends to be slightly higher than the content ratio of black, general-purpose polystyrene, and other additives, so in consideration of this point, carbon black, general-purpose polystyrene, and other additives of foamable styrene resin particles The content may be selected.

[Manufacturing method of styrene resin pre-foamed particles]
As the method for producing the styrene-based resin pre-foamed particles in the present invention, a conventionally known pre-foaming step can be adopted. According to this pre-foaming step, for example, styrene-based resin pre-foamed particles can be obtained by foaming with heated steam to about 3 times or more and 110 times or less.

The preliminary foaming process will be described in detail below.

A known prefoaming machine can be used, for example, a can equipped with a stirrer and containing effervescent styrene resin particles, a steam chamber installed below the can and supplying steam to the can, and the like. A pre-foaming machine equipped with a pre-foaming particle outlet is used. Steam is supplied to the steam chamber from the boiler. It is also possible to mix steam and compressed air and supply them to the steam chamber. In the present specification, the steam temperature is the temperature of the steam introduced into the steam chamber, and more specifically, the temperature of the steam 10 cm upstream from the steam introduction port of the steam chamber. In addition, the steam injection time (seconds) is such that after starting the supply of steam to the foamable styrene resin particles placed in the can, the foamable styrene resin particles become pre-foamed particles, which are used by the pre-foaming machine. This is the time during which steam was added before it was taken out of the can. When steam is charged into the can of the pre-foaming machine in a plurality of times, the total of the charged time is defined as the steam charging time.

The pressure inside the can (gauge pressure) can be controlled, for example, by adjusting the opening degree of the exhaust valve. In the present specification, the pressure inside the can is the internal pressure of the can during the addition of steam, and if the internal pressure fluctuates during the addition of steam, the internal pressure is measured every predetermined time (for example, 1 second) to obtain the pressure. It is calculated as the arithmetic mean value of the measured values. In the pressure foaming method, steam injection may be performed intermittently. Even if the supply of steam from the steam chamber to the inside of the can is stopped, the steam atmosphere inside the can continues. Therefore, in this case, steam is added during the time when the pressure inside the can is maintained above the atmospheric pressure. Include in time.

In the prefoaming step, the steam injection time is 50 seconds to 500 seconds, preferably 80 seconds to 300 seconds, and more preferably 100 seconds to 200 seconds. When the steam injection time is within the above range, the styrene-based resin mold in-foamed molded product of the present invention, which has a high foaming ratio and an independent foaming rate and is also excellent in surface beauty, can be obtained. Further, when a radiant heat transfer inhibitor such as graphite is added, it is possible to maintain a very low thermal conductivity for a long period of time from the beginning of production.

When the steam injection time is less than 50 seconds, it is necessary to raise the steam temperature in order to make the foamable styrene resin particles have a predetermined foaming ratio, but then the foamable styrene resin particles during the preliminary foaming adhere to each other. The blocking phenomenon tends to occur, and the preliminary foaming yield tends to decrease. If the steam injection time exceeds 500 seconds, the shrinkage of the obtained styrene-based resin pre-foamed particles becomes large, so that it is difficult to obtain styrene-based resin pre-foamed particles having a high foaming ratio, and a high foaming ratio (particularly 50 cm ³ /). It tends to be difficult to obtain a foamed molded product in a styrene resin mold (g or more), or the surface beauty of the obtained foamed molded product in a styrene resin mold tends to be impaired.

The pressure inside the can (cage pressure) at the time of adding steam is not particularly limited, but is preferably 0.001 to 0.15 MPa, more preferably 0.01 to 0.10 MPa, and even more preferably 0.03 to 0.08 MPa. .. Within such a can pressure range, even when a high foaming ratio (particularly 65 cm ³ / g or more) is obtained, the time required for pre-foaming can be shortened, and the steam injection time can be easily reduced to 500 seconds or less. In addition, the blocking phenomenon is unlikely to occur, and it is easy to obtain a high preliminary foaming yield.

By mixing steam with air, it is easy to adjust the steam temperature, control the steam injection time until the pre-foamed particles reach a predetermined foaming ratio, and increase the closed cell ratio of the pre-foamed particles. You can also do it.

The temperature of the water vapor introduced into the can is not particularly limited, but is preferably more than 95 ° C. and 130 ° C. or lower, more preferably 100 to 125 ° C., and even more preferably 105 to 120 ° C. Within such a temperature range, even when a high foaming ratio (particularly 65 cm ³ / g or more) is obtained, the time required for pre-foaming can be shortened, and the steam injection time can be easily reduced to 500 seconds or less. In addition, the blocking phenomenon is unlikely to occur, and it is easy to obtain a high preliminary foaming yield.

Preliminary foaming of the foamable styrene resin particles is preferably performed in one step. By performing pre-foaming in one step, not only excellent heat insulation and light weight, but also surface beauty and fusion between foamed particles inside are further improved. Obtainable. When the pre-foaming is performed in two steps, a high foaming ratio (for example, 50 cm ³ / g or more) can be easily obtained, but the surface beauty and the fusion property between the foamed particles inside tend to be deteriorated. is there.

Further, the preliminary foaming step can be performed by either a continuous method or a batch method.

The continuous method is a method in which the foamable styrene resin particles are continuously supplied into the can and the pre-foamed particles are continuously discharged from the discharge port provided on the upper part of the can. The expansion ratio of the pre-expanded particles can be adjusted, for example, by appropriately selecting the amount (weight) of the effervescent styrene-based resin particles charged into the can per hour. In the case of the continuous method, the residence time in the pre-foaming machine can from the time when the foamable styrene resin particles are supplied into the can until the pre-foaming particles are discharged is defined as the steam injection time.

In the batch method, a predetermined amount of foamable styrene resin particles are placed in a can, the particles are pre-foamed to a predetermined foaming ratio, the supply of water vapor is stopped, and then air is introduced into the can as needed. This is a method of blowing in to cool and dry the prefoamed particles and then taking them out of the can. The expansion ratio of the styrene-based resin pre-expanded particles can be adjusted by appropriately selecting the amount (weight) of the effervescent styrene-based resin particles charged into the can per batch. Since the batch method is a method of pre-foaming the charged foamable styrene resin particles to a predetermined volume, the foaming ratio of the obtained pre-foamed particles increases as the input amount per batch is reduced.

[Styrene-based resin mold foam molded product]
The styrene-based resin in-mold foam molded product of the present invention is an in-mold foam-molded product of the above-mentioned styrene-based resin pre-foamed particles of the present invention.

As in the case of the styrene resin pre-foamed particles, the content of carbon black, general-purpose polystyrene, and other additives in the foamed molded product in the styrene resin mold is, for example, carbon black in the foamable styrene resin particles. It can be adjusted by appropriately selecting the content of general-purpose polystyrene and other additives. The content ratio of carbon black, general-purpose polystyrene, and other additives in the foamed molded product in the styrene resin mold is determined by the volatilization of the foaming agent in the preliminary foaming step and the molding step, and the foamable styrene resin particles. It tends to be slightly higher than the content ratio of carbon black, general-purpose polystyrene, and other additives in it, so in consideration of this point, carbon black, general-purpose polystyrene, and other foamable styrene resin particles The content of the additive may be selected.

The foamed molded article in the styrene resin mold of the present invention is a carbon black having a ratio of 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin and the impact-resistant styrene resin. The following formula (1), which is the relational expression between the foaming ratio of the molded product and the half-break height.
Half fracture height (cm) ≧ -27.52 ln (molded foam expansion ratio (times)) +123.26 ... (1)
(However, ln is the natural logarithm)
It is preferable to satisfy.

The half-break height is a physical property that exhibits impact resistance, and is equivalent to an impact-resistant styrene resin in-mold foam molded product that is a natural color (white) obtained by the polymerization method by satisfying the above formula (1). It is a black (gray) styrene resin in-mold foam molded product containing carbon black while having the impact resistance of, and the natural color (white) is a helmet core material that is disliked to be colored over time due to stains and light deterioration. Even if it can be used.

This formula (1) shows the characteristics of the impact-resistant styrene-based resin in-mold foam molded article, which is a natural color (white) obtained from a conventionally known polymerization method, and is the carbon black-containing styrene of the present invention. When the foamed molded product in the resin mold satisfies the formula (1), the impact resistance of the foamed molded product in the styrene resin mold is sufficiently large, and even if it is blackened, it has sufficient impact resistance. Become.

The half-break height, which indicates the strength of crack resistance, can be measured by a falling ball impact test in accordance with JIS K 7211.

From the viewpoint of providing sufficient impact resistance even when blackened in this way, as described above, carbon black is 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact resistant styrene resin. It is more preferably 0.5 parts by weight or more and 7 parts by weight or less, and most preferably 1 part by weight or more and 6 parts by weight or less. If the amount of carbon black is less than 0.1 parts by weight, it may be difficult to suppress coloration over time due to stains, photodegradation, etc., and if it exceeds 10 parts by weight, the impact resistance tends to decrease, and an impact absorbing material such as a helmet core material tends to decrease. It may be difficult to use as.

The average cell diameter of the foamed molded article in the styrene resin mold of the present invention is preferably adjusted to 70 μm or more and 250 μm or less, more preferably 90 μm or more and 200 μm or less, and further preferably 100 μm or more and 180 μm or less. When the average cell diameter is within the above range, the foamed molded product in a styrene resin mold has less color unevenness, excellent coloring property, and high heat insulating property. The average cell diameter can be adjusted, for example, by appropriately selecting the amount of the nucleating agent.

Further, in the present invention, it is preferable to adjust the closed cell ratios of the styrene-based resin pre-foamed particles and the styrene-based resin in-mold foam molded product to 95% or more and 100% or less, respectively. By adjusting to this range, it is easy to obtain a styrene resin in-mold foam molded product having a high foaming ratio, and it is easy to obtain a styrene-based resin in-mold foam molded product having a beautiful surface and excellent heat insulating properties. The closed cell ratio can be adjusted, for example, by introducing a mixture of water vapor and air into a can in the prefoaming step or a molding die in the molding step, and appropriately selecting the ratio of water vapor in the mixture.

The foaming ratio of the foamed molded product in the styrene resin mold of the present invention is not particularly limited and may be the required foaming ratio, but is preferably 3 times (cm ³ / g) or more, 100 times ( cm ³ / g) or less.

[Manufacturing method of foam molded product in styrene resin mold]
As a method for producing the foamed molded product in the styrene resin mold in the present invention, a molding process using a conventionally known molding machine can be adopted. Then, depending on the shape of the mold used, it is possible to obtain a molded product having a complicated shape or a block-shaped molded product.

As the molding step, a molding step including the following steps (1) to (6) can be exemplified.
(1) A step (filling step) of filling a mold composed of a fixed mold and a mobile mold mounted on a molding machine with styrene-based resin pre-foamed particles in the mold through a filling machine.
(2) A step of expelling air existing in the mold and the mold chamber by flowing water vapor into the mold and heating the entire mold (preheating step).
(3) A step of expelling and heating the air existing between the styrene-based resin prefoamed particles filled in the mold by flowing water vapor from the fixed mold side to the mobile mold side (on the other hand, a heating step).
(4) Next, by flowing water vapor from the mobile mold side to the fixed mold side, the air existing between the styrene resin prefoamed particles filled in the mold is further expelled and heated (reverse one-sided heating). Process).
(5) By flowing water vapor from both the fixed mold side and the mobile mold side, the temperature is sufficiently raised until the surface of the styrene resin prefoamed particles filled in the mold is softened, and the styrene resin prefoamed. A step of finally fusing the particles together to form a foamed molded product in a styrene resin mold having a constant shape (double-sided heating step).
(6) A step of opening the mold after cooling the mold and taking out the foamed molded product in the styrene resin mold (cooling / taking out step).

[Use of foamed molded product in styrene resin mold]
The foamed molded product in a styrene resin mold of the present invention can be suitably used for, for example, a shock absorbing material, a heat insulating material for buildings, and the like.

Since the foamed molded product in the styrene resin mold of the present invention has a beautiful surface with few color unevenness and voids between the styrene resin pre-foamed particles, impact resistance is also required while being required to have a beautiful appearance. It is preferably used for various purposes. Examples of such applications include helmet core materials, automobile bumper core materials, automobile tivia pads, and the like. Since the helmet core material is provided in a portion of the helmet that can be easily seen, it is required that stains and coloring over time are inconspicuous, and the styrene-based resin mold in-foam molded product of the present invention is more preferably used.

Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto.

The measurement method and evaluation method in the following Examples and Comparative Examples are as follows.

(Residence time)
The black resin is discharged from the tip of the die from the time when the impact-resistant styrene resin containing no carbon black is supplied to the extruder in advance and operated, and the resin is switched to the mixed resin containing carbon black described in Examples or Comparative Examples. The time required for melting and kneading was measured and used as the residence time.

(Grain weight)
After arbitrarily extracting 100 effervescent styrene resin particles and measuring the weight, this weight was divided by 100 to calculate the grain weight (mg / grain).

(Appearance of foamable styrene resin particles)
The obtained foamable styrene resin particles were visually observed and evaluated as follows.
◯: There is little variation in the size of the foamable styrene resin particles. That is, the foamable styrene resin particles are in an unfoamed state, and there is little variation in the weight and size of each particle. In addition, there is no coalescence (aggregation) between the foamable styrene resin particles.
X: There is a clear variation in the size of the foamable styrene resin particles. That is, there is a clear variation in the weight and size of each of the effervescent styrene resin particles due to partial foaming or uneven discharge. Alternatively, coalescence (aggregation) of the effervescent styrene resin particles is observed.

(Surface beauty of foamed molded product in styrene resin mold)
The obtained foamed molded product in the styrene resin mold was visually observed and evaluated as follows.
⊚: There is no color unevenness, and there are few voids between the styrene-based resin pre-foamed particles constituting the styrene-based resin in-mold foam molded product.
◯: Some color unevenness is observed, but there are few voids between the styrene resin pre-foamed particles constituting the styrene-based resin mold in-foamed molded product.
X: Color unevenness is clearly observed, and voids between the styrene-based resin pre-foamed particles constituting the styrene-based resin in-mold foam molded product are conspicuous.

(Molded body foaming magnification)
The weight (g) of the crack resistance evaluation test piece (dimensions: 200 mm × 40 mm × 20 mm rectangular parallelepiped) described later was measured, and the vertical dimension, the horizontal dimension and the thickness dimension were measured using a caliper. The volume (cm ³ ) of the sample was calculated from each of the measured dimensions, and the foaming ratio of the molded product was calculated according to the following formula (2).
Mold foaming ratio (cm ³ / g) = sample volume (cm ³ ) / sample weight (g) ... (2)
The foaming magnification of the molded product "times" is also customarily expressed as "cm ³ / g".

(Crack resistance (half fracture height))
The falling ball impact test, which shows the strength of the crack resistance of the foam, is performed in accordance with JIS K 7211-1976. A 200 mm × 40 mm × 20 mm test piece is cut out from the foamed molded product in the styrene resin mold with a vertical slicer with a saw blade. This test piece has two surfaces of 200 mm × 40 mm, one of which is the surface skin of the foamed molded product in the styrene resin mold (the surface skin of the foamed molded product in the styrene resin mold is inside the styrene resin mold). The part exposed on the surface of the foamed molded product in the styrene resin mold when the foamed molded product is molded, which is different from the inside of the foamed molded product in the styrene resin mold cut out by the vertical slicer.) The other side is the surface cut out with a saw blade vertical slicer. Further, two surfaces of 200 mm × 20 mm and two surfaces of 40 mm × 20 mm shall be surfaces cut out with a vertical slicer. Prepare 20 test pieces.

A 321 g hard ball is dropped on the surface of the test piece where the skin is located as the surface on which the falling ball collides. Calculate the half fracture height by the following formula (3). The larger the value, the greater the crack resistance.

・・・・・（３）
Ｈ_５０：半数破壊高さ（ｃｍ）、
Ｈ_Ｉ：高さ水準（ｉ）が０のときの試験高さ（ｃｍ）であり、試験片が破壊することが予測される高さ、
ｄ：試験高さを上下させるときの高さ間隔（ｃｍ）、
ｉ：Ｈ_Ｉのときを０とし、１つずつ増減する高さ水準（ｉ＝…−３、−２、−１、０、 １、２、３、…）、
ｎ-_ｉ：各水準において破壊した（または破壊しなかった）試験片の数、
Ｎ：破壊した（または破壊しなかった）試験片の総数（Ｎ＝Σｎ_ｉ）、いずれか多いほうのデータを使用する、同数の場合はどちらを使用してもよい、
±０．５：破壊したデータを使用するときは負、破壊しなかったデータを使用するときは正とする。

(3)
H ₅₀ : Half destruction height (cm),
H _I: the height level (i) the test height when the 0 (cm), height test piece is predicted to be destroyed,
d: Height interval (cm) when raising and lowering the test height,
i: when the _{H I} is 0, the height level of increasing or decreasing one by 1 (i = ... -3, -2 , -1,0, 1,2,3, ...),
n- _i : Number of test pieces destroyed (or not destroyed) at each level,
N: Total number of disrupted (or were not destroyed) specimens (N = .SIGMA.n _i), using either more often than the data, in the case of the same number may be used either,
± 0.5: Negative when using destroyed data, positive when using undestroyed data.

Equation (1), which is a relational expression between the foaming ratio of the molded product and the half fracture height.
Half fracture height (cm) ≧ -27.52 ln (molded foam expansion ratio (times)) +123.26 ... (1)
Was evaluated as ◯, and if not satisfied, it was evaluated as ×. However, ln is a natural logarithm.

The raw materials used in the examples and comparative examples are as follows.

(Impact resistant styrene resin)
(A-1) High Impact Polystyrene [manufactured by PS Japan Corporation, 475D, flexural modulus 2250 MPa]
(A-2) High Impact Polystyrene [manufactured by PS Japan Corporation, H0103, flexural modulus 2050 MPa]
(A-3) High Impact Polystyrene [manufactured by PS Japan Corporation, H9152, flexural modulus 2600 MPa]

(Carbon black)
(B) Carbon Black [Made by Regino Color Industry Co., Ltd., Black SMF-TT1608, Pigment Content 50%]

(Carbon Black Masterbatch)
(C) Carbon Black Masterbatch [Manufactured by Regino Color Industry Co., Ltd., Black SBF-T-1683DK, Pigment content 40%, Base resin: GPPS (General-purpose polystyrene)]

(General-purpose polystyrene)
(D) Styrene homopolymer [manufactured by PS Japan Corporation, 680]

(Foaming agent)
(E) Mixed pentane (mixture of 80% by weight of normal pentane and 20% by weight of isopentane) [both normal pentane and isopentane are manufactured by Wako Pure Chemical Industries, Ltd., reagent products]

(Example 1)

[Preparation of foamable styrene resin particles]
Impact-resistant styrene resin (A-1) and carbon black (B) were put into a blender at the blending ratios shown in Table 1 and blended for 10 minutes to obtain a resin mixture.

The obtained resin mixture is supplied to a tandem type two-stage extruder in which a twin-screw extruder (first extruder) having a diameter of 40 mm and a single-screw extruder (second extruder) having a diameter of 90 mm are connected in series. The first extruder was melt-kneaded at a screw rotation speed of 150 rpm. The mixed pentane (E) was press-fitted into 100 parts by weight of the resin mixture at a ratio of 7 parts by weight from the middle of the 40 mm diameter extruder (first extruder). At this time, the resin temperature measured by the thermocouple installed at the tip of the first extruder was 190 ° C. Then, it was supplied to a 90 mm diameter extruder (second extruder) through a continuous pipe. The screw rotation speed of the second extruder was appropriately adjusted so that the same amount as the amount of the resin mixture supplied per unit time to the first extruder was discharged from the second extruder.

After cooling the molten resin to 160 ° C (measured by a thermocouple installed at the tip of the second extruder) with a 90 mm diameter extruder (second extruder), it was attached to the tip of the second extruder. From a die (die set temperature 250 ° C.) having 60 small holes with a diameter of 0.65 mm and a land length of 3.0 mm attached via continuous piping, the total discharge rate is 60 kg / hour (1.0 kg / hour per hole). Hole / time)), extruded into pressurized circulating water at a temperature of 50 ° C. and 0.8 MPa (gauge pressure). The extruded molten resin is cut and granulated under the condition of 1500 rpm using a rotary cutter having 10 blades in contact with the die, transferred to a centrifugal dehydrator, and has a grain weight of 1.0 mg / grain. Foamable styrene resin particles were obtained. At this time, the total residence time in the first extruder and the second extruder was about 6 minutes.

0.08 part by weight of zinc stearate was dry-blended with respect to 100 parts by weight of the obtained foamable styrene resin particles, and then stored at 15 ° C.

[Preparation of styrene resin pre-foamed particles]
Two weeks after the foamable styrene resin particles were prepared and stored at 15 ° C., the foamable styrene resin particles were put into a preliminary foaming machine [BHP-300 manufactured by Daikai Kogyo Co., Ltd.] and 0.08 MPa (gauge). Pressure) steam was charged into a pre-foaming machine (steam injection time: 190 seconds) to foam the particles to obtain styrene-based resin pre-foamed particles having a bulk ratio of 23 times.

[Preparation of foamed molded product in styrene resin mold]
Inside the in-mold molding die (length 450 mm x width 310 mm x thickness 25 mm) in which the obtained pre-foamed particles with a bulk ratio of 23 times were attached to a styrofoam molding machine [KR-57, manufactured by Daisen Kogyo Co., Ltd.]. Was filled with water vapor at 0.06 MPa (gauge pressure) to cause foaming in the mold, and then water was sprayed onto the mold for 3 seconds to cool the mold. After holding the foamed mold in the styrene resin mold in the mold until the pressure at which the foamed mold in the styrene resin mold pushes the mold becomes 0.015 MPa (gauge pressure), the foamed mold in the styrene resin mold is taken out. A rectangular styrene resin in-mold foam molded product was obtained. The foaming ratio was 23 times.

The appearance of the foamable styrene resin particles in Example 1, the surface beauty of the foamed molded product in the styrene resin mold, the magnification of the molded product, and the half-break height were evaluated. The results are shown in Table 1.

(Examples 2 to 12, Comparative Examples 1 to 8)
The same procedure as in Example 1 was carried out except that the production conditions such as the blending ratio were changed as described in Table 1 or Table 2, and the foamable styrene resin particles, the styrene resin pre-foamed particles and the styrene resin in-mold foaming were carried out. A molded product was obtained. However, when the effervescent styrene resin particles were obtained, the rotation speed or the number of blades of the rotary cutter was appropriately adjusted to obtain effervescent styrene resin particles having a grain weight of 1.0 mg / grain in any case. Further, when the styrene-based resin pre-foamed particles were obtained, the steam injection time was appropriately changed to adjust the foaming ratio.

The appearance of the foamable styrene resin particles in Examples 2 to 12 and Comparative Examples 1 to 8, the surface beauty of the foamed molded product in the styrene resin mold, the magnification of the molded product, and the half fracture height were evaluated. The results are shown in Table 1 or Table 2.

(Reference Examples 1 to 4)
Using Kanepearl HS manufactured by Kaneka Co., Ltd., which is an effervescent styrene-based resin particle (not including carbon black) using high-impact polystyrene as a base resin obtained from the suspension polymerization method, styrene is used in the same manner as in Example 1. Pre-foamed particles of based resin and foamed molded article in styrene resin mold were obtained. When the styrene resin pre-foamed particles were obtained, the steam injection time was appropriately changed to adjust the foaming ratio.

The appearance of the foamable styrene resin particles in Reference Examples 1 to 4, the surface beauty of the foamed molded product in the styrene resin mold, the foaming ratio of the molded product, and the half-break height were evaluated. The results are shown in Table 2. Further, FIG. 1 shows a graph showing the relationship between the foaming ratio of the molded product and the half fracture height. As a result of logarithmic approximation based on these results, a result of half fracture height (cm) = −27.52 ln (molded foam expansion ratio (times)) +123.26 was obtained.

From Tables 1 and 2, as in Examples 1 to 12, the discharge amount of the molten resin passing through the small holes when extruded into the pressurized water is 1.0 kg / hole to 2.5 kg / hole per hour. By setting the pressure of the pressurized water to 0.8 MPa (gauge pressure) to 1.2 MPa (gauge pressure) and the temperature of the pressurized water to 50 ° C to 70 ° C, there is little variation in the size of the foamable styrene resin particles. It was possible to obtain foamable styrene resin particles having a desired appearance without agglomeration between the foamable styrene resin particles. In addition, it was possible to obtain a styrene-based resin in-mold foam molded product having a beautiful surface with improved color unevenness and particle gaps. Further, as can be seen from the result of the formula (1) regarding the half fracture height, it was possible to obtain a styrene resin in-mold foam molded product having sufficient impact strength according to the foaming ratio.

In Comparative Examples 1 to 7 which do not satisfy the above conditions, foamable styrene resin particles having a desired appearance cannot be obtained, and a styrene resin in-mold foam molded product having a beautiful surface can be obtained. could not. Since Comparative Example 8 did not contain an impact-resistant styrene-based resin, it was not possible to obtain a styrene-based resin in-mold foam molded article having sufficient impact strength.

Since Reference Examples 1 to 4 did not contain carbon black, a black or gray styrene resin foam molded product could not be obtained.

As described in detail above, according to the present invention, when foamable styrene resin particles containing impact-resistant styrene resin as a main component and containing carbon black are produced by the quench method, they pass through small pores. The 1-hour discharge rate of the molten resin is 1.0 to 2.5 kg / hole, the pressure of the pressurized water is 0.8 to 1.2 MPa, and the temperature of the pressurized water is 50 to 70 ° C. Conventionally, the carbon black-containing impact-resistant styrene resin mold in-foam molded product obtained by the quench method can exhibit the same impact strength as the impact-resistant styrene resin mold in-foam molded product obtained by the polymerization method. It was not possible, and the impact-resistant styrene resin in-mold foam molded body obtained by the polymerization method was difficult to blacken. However, according to the present invention, the impact-resistant styrene resin containing carbon black is used. Although it is a styrene resin in-mold foam molded product, it has the same impact strength as the impact-resistant styrene resin in-mold foam molded product obtained by the polymerization method, and it also improves black color unevenness and particles. It is possible to achieve a beautiful blackening with uniform gaps. As for the foamable styrene resin particles, it is possible to obtain foamable styrene resin particles having a desired appearance with little variation in particle size and no agglomeration between the particles.

The embodiments and examples described above are all exemplary and not limited to the present invention, and the present invention can be carried out in various other modifications and modifications. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

Claims (6)

The impact-resistant styrene resin, carbon black containing 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin, and a foaming agent are melt-kneaded to obtain a molten resin. A method for producing foamable styrene resin particles in which a molten resin is extruded into pressurized water through a die having small pores, and the molten resin extruded into the pressurized water is cut by a rotary cutter. The molten resin passing through the small pores. The discharge rate per hour is 1.0 kg / hole or more and 2.5 kg / hole or less, and the pressure of the pressurized water is 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less. A method for producing foamable styrene resin particles, wherein the temperature of the pressurized water is 50 ° C. or higher and 70 ° C. or lower. The method for producing foamable styrene-based resin particles according to claim 1, wherein the residence time, which is the time spent for melt-kneading, is less than 15 minutes. The method for producing foamable styrene resin particles according to claim 1 or 2, wherein the impact-resistant styrene resin has a flexural modulus of 2000 MPa or more and 2300 MPa or less. The foamable styrene according to any one of claims 1 to 3, wherein the impact-resistant styrene resin, carbon black, a foaming agent, and general-purpose polystyrene are melt-kneaded to obtain the molten resin. Method for manufacturing styrene resin particles. The foamable styrene resin particles according to claim 4, wherein the general-purpose polystyrene is contained in an amount of 0.15 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin. Production method. (A) Impact-resistant styrene resin, carbon black containing 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the impact-resistant styrene resin, and a foaming agent are melt-kneaded and kneaded to form a molten resin. This is a process for producing foamable styrene resin particles in which the molten resin is extruded into pressurized water through a die having small pores, and the molten resin extruded into the pressurized water is cut by a rotary cutter, and passes through the small pores. The discharge rate of the molten resin per hour is 1.0 kg / hole or more and 2.5 kg / hole or less, and the pressure of the pressurized water is 0.8 MPa (gauge pressure) or more and 1.2 MPa (gauge pressure) or less. A step of producing foamable styrene resin particles in which the temperature of the pressurized water is 50 ° C. or higher and 70 ° C. or lower.
(B) A step of heating the produced effervescent styrene resin particles to produce styrene resin pre-expanded particles, and
(C) Production of a styrene-based resin in-mold foam molded product, which comprises a step of in-mold foam molding of the produced styrene-based resin pre-foamed particles to produce a styrene-based resin in-mold foamed molded product. Method.

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