JP6170703B2 - POLYSTYRENE COMPOSITE RESIN PARTICLE AND METHOD FOR PRODUCING THE SAME, FOAMABLE PARTICLE, FOAMED PARTICLE AND FOAM MOLDED - Google Patents

Description

  The present invention relates to a polystyrene-based composite resin particle and a method for producing the same, expandable particles, expanded particles, and an expanded molded body. ADVANTAGE OF THE INVENTION According to this invention, the polystyrene type composite resin particle which can shorten the shaping | molding cycle of a foaming molding can be provided.

Foamed molded articles made of polystyrene resin are widely used as packaging materials and heat insulating materials because they have excellent buffering properties and heat insulating properties and are easy to mold. However, since the impact resistance and flexibility are insufficient, there is a problem that cracks and chips are likely to occur, and it is not suitable, for example, for packaging precision instrument products.
On the other hand, a foam-molded article made of polyolefin resin is excellent in impact resistance and flexibility, but requires a large facility for molding. Also, due to the nature of the resin, it must be transported from the raw material manufacturer to the molding processing manufacturer in the form of expanded particles. Therefore, bulky expanded particles are transported, and there is a problem that the manufacturing cost increases.

Therefore, various polystyrene composite resin particles having the characteristics of the two different resins and foamed molded products using them have been proposed.
For example, Japanese Patent Application Laid-Open No. 2005-97555 (Patent Document 1) discloses an olefin-modified polystyrene system excellent in rigidity, chemical resistance and impact resistance, which is obtained by allowing a polyolefin resin to exist in a rich manner on the particle surface layer. Resin pre-expanded particles, a method for producing the same, and a foam-molded article are disclosed.

In addition, in Japanese Patent Application Laid-Open No. 2006-83221 (Patent Document 2), styrene is added to non-crosslinked linear low density polyethylene resin particles containing an inorganic nucleating agent, and the melting point of the polyethylene resin particles is set to T ° C. Sometimes, styrene-modified polyethylene resin particles obtained by polymerizing styrene at (T + 5) to (T + 25) ° C. are disclosed.
The resin particles are present in a state where 0.8 μm or less of polystyrene resin particles are dispersed on the surface layer, and a foam molded article having excellent impact resistance and the like can be obtained.

On the other hand, in conjunction with the recent increase in fuel prices, efforts have been made to save energy during molding of foam molded articles while maintaining or improving the excellent properties of the foam molded articles.
For example, in JP 2010-209146 A (Patent Document 3), the poorly water-soluble inorganic substance (dispersing agent) on the surface of the pre-foamed particles is reduced to 1000 ppm or less to improve the fusibility, thereby saving steam (energy saving). Discloses a technique for foam molding.

  Japanese Patent Application Laid-Open No. 2010-270284 (Patent Document 4) discloses a fusion property by setting the absorbance ratio of a specific wavelength obtained from the infrared absorption spectrum of the surface of the pre-foamed particle to a range of 2.5 to 11.0. A technique for foaming with improved steam and energy saving is disclosed.

JP-A-2005-97555 JP 2006-83221 A JP 2010-209146 A JP 2010-270284 A

However, the resin particles described in Patent Documents 1 to 3 are rich in polyolefin components such as polyethylene in the skin layer and hardly show polystyrene components. More specifically, there is almost no polystyrene-based resin within the surface depth of 1 μm of the resin particles, and the resin particles are richly present at the center of the resin particles. Since the retention property of the foaming agent of polystyrene resin is high, it is difficult for the foaming agent to dissipate from the resin particles, and such resin particles are disadvantageous for shortening the molding cycle of the foamed molded product.
Patent Document 4 shows that by increasing the presence of the polystyrene resin on the surface of the styrene-modified polyethylene resin foamed molded article, it is possible to save steam and improve the fusion property.
However, when the resin particles for obtaining this foamed molded product were re-examined, styrene was polymerized at 85 ° C., so that the inside was a co-continuous structure, and it was easy to hold the foaming agent. However, a disadvantageous result was obtained for shortening the molding cycle of the foamed molded product.

  Then, this invention solves said subject, and it aims at providing the polystyrene type composite resin particle which can shorten the molding cycle of a foaming molding, its manufacturing method, expandable particle, foaming particle, and a foaming molding. To do.

  The inventor of the present invention is obtained by cutting a melt-kneaded product of a mixed resin of linear low density polyethylene resin containing a specific amount of polystyrene resin as a result of intensive studies to achieve the above problems, Polystyrene composite resin particles obtained by impregnating and polymerizing styrene into core resin particles in which a polystyrene resin having a specific particle size is dispersed, polymerizing, passing through an annealing treatment step, and then polymerizing the particles are specific particles on the surface layer. Since the polystyrene component having a diameter is present in a specific area ratio, that is, a lump of polystyrene component holding the foaming agent is present on the surface layer of the composite resin particle, the dissipation of the foaming agent present on the surface layer is promoted and molding The present inventors have found that the cycle can be shortened and have completed the present invention.

Thus, according to the present invention, polystyrene-based composite resin particles containing a linear low density polyethylene resin and a polystyrene resin in a mass ratio of 50:50 to 15:85,
The polystyrene composite resin particles have a particle diameter of 0.25 to 0.80 μm in a range of 0.5 μm depth and 5 μm length from the particle surface in a TEM image obtained from an arbitrary observation point on the particle surface layer. There is provided a polystyrene-based composite resin particle, wherein the polystyrene-based resin fine particle has an area ratio of 5 to 45% in the range of the polystyrene-based resin fine particle.

Moreover, according to this invention, the expandable particle | grains containing said polystyrene type composite resin particle and a volatile foaming agent are provided.
Furthermore, according to the present invention, there are provided expanded particles obtained by pre-expanding the expandable particles.
Moreover, according to this invention, the foaming molding obtained by carrying out foam molding of said foaming particle is provided.

Furthermore, according to the present invention, there is provided a method for producing the above-mentioned polystyrene composite resin particles,
Water medium in, the nucleus resin particles mixed resin containing a linear low-density polyethylene resin and polystyrene resin, after absorbing the styrene monomer, the step of polymerizing the styrene monomer If, then the steps of a Neil, by polymerizing while further absorb styrene monomer, method of manufacturing polystyrene composite resin particles which comprises the steps of: obtaining a polystyrene composite resin particles Provided.

  ADVANTAGE OF THE INVENTION According to this invention, the polystyrene type composite resin particle which can shorten the shaping | molding cycle of a foaming molding, its manufacturing method, foamable particle, foaming particle, and a foaming molding can be provided.

The polystyrene composite resin particles of the present invention are
(1) Polystyrene composite resin particles have a polystyrene island sea-island structure at the center of the particles.
(2) When about 1 g of the polystyrene composite resin particles are treated with 100 ml of toluene heated in an oil bath at 130 ° C., the gel content contains 10 to 35% by mass of a gel component insoluble in toluene.
(3) The polystyrene-based composite resin particles have an average particle diameter of 0.5 to 3.0 mm.
(4) polystyrene composite resin particles, its absorbance 698cm from polystyrene resin obtained from an infrared absorption spectrum of the particle surface ^-1 (D698) and linear low density absorbance of the polyethylene resin from the 2850 cm ^-1 ( D2850) with an absorbance ratio of 0.5 to 2.5 (D698 / D2850),
The above excellent effect is further exhibited when at least one of the above conditions is satisfied.
Furthermore, in the expandable particle, the above excellent effect is further exhibited when the expanded particle has a bulk density of 0.012 to 0.20 g / cm ³ .

2 is a TEM image of core resin particles of Example 1. It is a TEM image of (a) particle | grain surface part and (b) particle | grain center part in the composite resin particle of Example 1. FIG. It is a TEM image of (a) particle | grain surface part and (b) particle | grain center part in the composite resin particle of the comparative example 1. It is a TEM image of (a) particle | grain surface part and (b) particle | grain center part in the composite resin particle of the comparative example 2.

(1) Polystyrene-based composite resin particles The polystyrene-based composite resin particles of the present invention (hereinafter also referred to as “composite resin particles”) are composed of a linear low-density polyethylene resin and a polystyrene resin in a mass ratio of 50:50 to 15: The polystyrene composite resin particles contained at a ratio of 85, the polystyrene composite resin particles having a depth from the particle surface (vertical direction of the image) of 0 in a TEM image obtained from an arbitrary observation point on the particle surface layer. In the range of 0.5 μm and length (left and right direction of the image) 5 μm, polystyrene resin fine particles having a particle diameter of 0.25 to 0.80 μm are included, and the area ratio of the polystyrene resin fine particles in the range is 5 to 45%. It is characterized by being.
In addition, according to analysis and evaluation of the present inventors such as a TEM image, the area ratio of the polystyrene-based resin in the surface layer of the resin particles described in Patent Documents 1 to 4 is outside the scope of the present invention.

(A) Particle diameter of polystyrene-based resin fine particles on the particle surface layer and area ratio thereof The composite resin particle of the present invention has a depth of 0. 0 from the particle surface in a TEM image obtained from an arbitrary observation point on the particle surface layer. Polystyrene resin fine particles having a particle diameter of 0.25 to 0.80 μm are included in the range of 5 μm and length of 5 μm, and the area ratio of the polystyrene resin fine particles in the above range is 5 to 45%.
The particle diameter of the polystyrene resin fine particles is determined by an average value of the longest diameter and the shortest diameter of the fine particles, and the area ratio is the area of the polystyrene resin fine particles having a particle diameter of 0.25 to 0.80 μm in the image. It is determined by the ratio between the total and the range.
The measuring method of the particle diameter of the polystyrene resin fine particles on the particle surface layer and the area ratio occupied by the polystyrene resin fine particles will be described in detail in Examples.

If the particle diameter of the polystyrene resin fine particles is less than 0.25 μm, a foamed molded article having excellent compressive strength cannot be provided, and the molding cycle may not be shortened.
On the other hand, when the particle diameter of the polystyrene resin fine particles exceeds 0.80 μm, chemical resistance and impact resistance peculiar to the polyethylene resin may not be obtained.

In addition, when the area ratio of polystyrene resin fine particles is less than 5%, a foamed molded article having excellent compressive strength cannot be provided, and the molding cycle may not be shortened.
On the other hand, when the area ratio occupied by the polystyrene resin fine particles exceeds 45%, chemical resistance and impact resistance peculiar to the linear low density polyethylene resin may not be obtained.
The particle diameter of the preferable polystyrene resin fine particles is 0.25 to 0.60 μm, and the preferable area ratio is 5 to 30%.

(B) Structure of Particle Center Part The composite resin particle of the present invention preferably has a polystyrene island sea-island structure in the particle center part.
Thereby, the molding cycle of a foaming molding can be shortened.
The particle central portion means a portion within a radius of 30% from the particle center.
The “sea-island structure of polystyrene-based resin” in the present invention is a linear low-density polyethylene-based resin having a substantially circular and / or indefinite granular polystyrene-based resin (this polystyrene-based resin may be connected to several). ).
On the other hand, polystyrene-based resins that are substantially circular and / or amorphous particles are connected to each other to form a continuous phase, and substantially circular and / or irregular granular linear chains are formed in the continuous phase. A structure including a low density polyethylene resin is defined as a “co-continuous structure”.
The method for evaluating the structure of the particle center will be described in detail in Examples.

(C) Content of gel insoluble in toluene heated at 130 ° C. (gel fraction)
The composite resin particle of the present invention contains 10 to 35% by mass of a gel content insoluble in toluene heated at 130 ° C., more specifically, about 100 g of toluene heated at 130 ° C. about 1 g of the composite resin particle. It is preferable to contain 10 to 35% by mass of a gel content that is insoluble in toluene.
Thereby, the impact resistance of the foaming molding shape | molded using the composite resin particle improves.
When the gel content is less than 10% by mass, the impact resistance of the foamed molded product is lowered, and the impact resistance as a buffer material may not be sufficient.
On the other hand, when the gel content exceeds 35% by mass, processability such as foamability and moldability is deteriorated, and a highly foamed molded article or a molded article having a good appearance may not be obtained.
A more preferable gel content is in the range of 15 to 30% by mass, and more preferably in the range of 15 to 25% by mass.
The method for measuring the gel content will be described in detail in Examples.

(D) Polystyrene resin (PS)
The polystyrene resin constituting the polystyrene composite resin particles is not particularly limited as long as it is a resin mainly composed of a styrene monomer, and examples thereof include styrene or a styrene derivative alone or a copolymer.
Examples of the styrene derivative include α-methyl styrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromostyrene, and the like. These styrenic monomers may be used alone or in combination.

The polystyrene resin may be a combination of a vinyl monomer copolymerizable with a styrene monomer.
Examples of the vinyl monomer include divinylbenzene such as o-divinylbenzene, m-divinylbenzene and p-divinylbenzene, alkylene glycol di (meth) acrylate such as ethylene glycol di (meth) acrylate and polyethylene glycol di (meth) acrylate. And polyfunctional monomers such as (meth) acrylate; (meth) acrylonitrile, methyl (meth) acrylate, butyl (meth) acrylate and the like. Among these, polyfunctional monomers are preferable, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate having 4 to 16 ethylene units, and divinylbenzene are more preferable, and divinylbenzene, ethylene glycol di ( Particularly preferred is (meth) acrylate. In addition, a monomer may be used independently or may be used together.
Moreover, when using a monomer together, it is preferable that the content is set so that it may become the quantity (for example, 50 mass% or more) which a styrene-type monomer becomes a main component.
In the present invention, “(meth) acryl” means “acryl” or “methacryl”.

(E) Linear low density polyethylene resin (LLDPE)
The linear low-density polyethylene resin constituting the polystyrene-based composite resin particles is a linear polyethylene-based resin having a density of 0.910 to 0.925 g / cm ³ , and specifically used in the examples. A commercially available product is mentioned.

The composite resin particle of the present invention contains a linear low density polyethylene resin and a polystyrene resin in a mass ratio of 50:50 to 15:85.
Of the mass ratio of the linear low density polyethylene resin and the polystyrene resin, if the polystyrene resin is less than 50%, foamability and molding processability may be insufficient.
On the other hand, if the polystyrene resin is 85% or more, impact resistance and flexibility may be insufficient.

(F) Particle diameter of composite resin particles The composite resin particles preferably have an average particle diameter of 0.5 to 3.0 mm.
When the average particle diameter of the composite resin particles is less than 0.5 mm, high foamability may not be obtained.
On the other hand, when the average particle diameter of the composite resin particles exceeds 3.0 mm, the filling property of the foamed particles during molding may be insufficient.
More preferably, the average particle size of the composite resin particles is 0.5 to 2.0 mm.

(2) Production method of polystyrene composite resin particles The composite resin particles of the present invention are, for example,
A melt-kneaded product of a mixed resin containing 100 parts by mass of a linear low-density polyethylene resin and 1 to 30 parts by mass of a polystyrene resin is cut to make the polystyrene resin fine with an average particle diameter of 0.01 to 0.60 μm. Obtaining dispersed nuclear resin particles;
Next, after the styrene monomer is absorbed in the core resin particles in the aqueous medium, the step of polymerizing the styrene monomer (first polymerization step), and the step of annealing at 140 to 145 ° C. thereafter And a step of obtaining polystyrene-based composite resin particles (second polymerization step) by further polymerizing the styrene-based monomer while absorbing the styrene-based monomer. be able to.
Here, “finely dispersed” means that fine particles having a specific particle diameter are dispersed in the substrate.

  The polymerization of the above monomer can be performed, for example, by heating at 70 to 150 ° C. for 2 to 40 hours. The polymerization can be performed after the monomer is absorbed into the core resin particles or while the monomer is absorbed into the core resin particles. The amount of monomer and resin is almost the same.

Furthermore, the process of annealing at 140-145 degreeC is included.
Here, the importance of the annealing step will be described in detail.
When 25 to 55 parts by mass of a styrene monomer is absorbed with respect to 100 parts by mass of the core resin particles in the previous stage, the styrene monomer is included in the core resin particles in advance, in addition to the progress of the polymerization reaction alone. The polymerization reaction starting from the finely dispersed polystyrene-based resin also proceeds at the same time.

Among polystyrene resin fine particles produced by polymerizing starting from a polystyrene resin that is uniformly finely dispersed in the core resin particles and pre-containing, in particular, a polystyrene resin generated by polymerizing starting from the surface layer of the core resin particles The fine particles tend to stay on the surface layer of the core resin particle because the particle diameter is larger than that of the polystyrene resin produced by polymerizing the styrene monomer alone. The polystyrene resin fine particles produced by the polymerization reaction of the styrenic monomer alone are sufficiently absorbed by the core resin particles as shown in the conventional technology so far to reach the center of the core resin particles. To complete the polymerization reaction.
When the annealing treatment is performed, the polystyrene resin fine particles having a large particle diameter produced by polymerization starting from the surface layer of the core resin particles are also the same as the polystyrene resin fine particles produced by the polymerization reaction of the styrene monomer alone. It was found that the polymerization reaction was completed while being absorbed from the surface layer to the central part. That is, some of the polystyrene resin fine particles having a relatively large particle diameter remain on the surface layer, while others are absorbed in the direction from the surface layer toward the central portion, thereby completing the polymerization reaction.

On the other hand, when the annealing process is not performed, the amount of polystyrene resin fine particles that complete the polymerization reaction on the surface layer of the core resin particles is increased, and the polystyrene resin present on the particle surface layer when finally becoming composite resin particles Increases the chemical resistance and impact resistance.
By including the step of annealing in this way, a starting point for forming an appropriate amount of polystyrene-based resin fine particles is formed on the surface layer of the core resin particles, and the composite resin particles that characterize the present invention are completed by the polymerization reaction in the next step. It will be. That is, in a TEM image obtained from an arbitrary observation point of the composite resin particle surface layer, polystyrene resin particles having a particle diameter of 0.25 to 0.80 μm in a range of depth 0.5 μm and length 5 μm are contained in polystyrene. The area ratio of the resin fine particles in the above range is 5 to 45%. As a result, it is possible to develop the effect of improving the compressive strength and shortening the molding cycle.

Examples of the styrene monomer include those exemplified in the section of polystyrene composite resin particles.
The usage-amount is the range of 100-667 mass parts normally with respect to 100 mass parts of nucleus resin particles, Preferably it is the range of 100-400 mass parts.

  In addition, after the annealing step, the polymerization step is performed to obtain composite resin particles, or the step of impregnating the foaming agent in the formation process of the composite resin particles is performed to obtain expandable particles described later.

(A) Nuclear resin particles (also referred to as “seed particles”)
The core resin particles are obtained by melting and kneading a mixed resin containing 100 parts by mass of a linear low density polyethylene resin and 1 to 30 parts by mass of a polystyrene resin. The polystyrene resin has an average particle diameter of 0.01 to 0. Resin particles dispersed at 60 μm.
Examples of the core resin particles include a method in which a raw material resin is melt-kneaded with an extruder, extruded into a strand shape, and cut with a desired particle diameter. Further, a linear low density polyethylene resin and a polystyrene resin recovered product can be used for a part or all of the particles, and the particles obtained by suspension polymerization method or cutting method are used as they are or in the aqueous medium. Among them, particles obtained by impregnating and polymerizing a monomer of the core resin may be used.

The core resin particles are preferably extruded after 100 parts by mass of a linear low density polyethylene resin and 1 to 30 parts by mass of a polystyrene resin are mixed in advance. For example, mixing can be performed using a mixer such as a tumbler mixer, a Henschel mixer, a ribbon blender, a V blender, or a Laedige mixer, or a blender included in the blender.
In order to disperse polystyrene resin with an average particle size of 0.01 to 0.60 μm, for example, a twin screw extruder equipped with a high dispersion type screw such as a dull mage type, a mudock type and a mini melt type, a kneading disk, etc. It is preferable to control the resin temperature measured at the center of the resin flow path of the extruder head part to 270 to 320 ° C. and the head part pressure to 15 to 25 MPa.

Furthermore, the diameter of the resin discharge hole of the die for obtaining the core resin particles of a predetermined size is preferably 0.2 to 1.0 mm, and the land length of the resin flow path maintains the high dispersibility of the polystyrene resin. In order to maintain the pressure of the resin flow path of the die at 10 to 20 MPa, the resin temperature at the die inlet of the resin extruded from the extruder is adjusted to 200 to 270 ° C. It is preferable.
Desired core resin particles can be obtained by combining an extruder and a die having the screw structure, extrusion conditions, and underwater cutting conditions.
In addition, the above core resin particles are additives such as a linear low density polyethylene resin and a polystyrene resin compatibilizer, bubble regulator, pigment, antistatic agent, flame retardant, etc., as long as the effects of the present invention are not impaired. Can be contained.

When the particle diameter of the polystyrene resin is less than 0.01 μm, 0.25 to 0.80 μm polystyrene resin particles are not formed at a depth of 0.5 μm from the surface of the composite resin particles, and the compression strength is improved and the molding cycle is increased. The effect sufficient for shortening may not be obtained.
On the other hand, when the particle diameter of the polystyrene resin exceeds 0.60 μm, the particle diameter of the polystyrene resin fine particles existing at a depth of 0.5 μm from the surface of the composite resin particle exceeds the range of 0.25 to 0.80 μm. As a result, sufficient chemical resistance and impact resistance may not be obtained.
The particle diameter of the preferable polystyrene resin fine particles present in the composite resin particles is 0.25 to 0.50 μm.

  The particle diameter of the core resin particles can be adjusted as appropriate according to the average particle diameter of the composite resin particles, and the preferable particle diameter is in the range of 0.4 to 1.5 mm, more preferably 0.4 to 1.0 mm. The average mass is 30 to 90 mg / 100 grains. In addition, examples of the shape include a true spherical shape, an elliptical spherical shape (egg shape), a cylindrical shape, and a prismatic shape.

(B) Polymerization initiator The polymerization initiator used in the above production method is not particularly limited as long as it is conventionally used for polymerization of styrene monomers, and examples thereof include benzoyl peroxide and lauryl peroxide. T-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-bis (t-butylperoxy) butane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, 2,2-di-t- Presence of butyl peroxybutane, di-t-hexyl peroxide, dicumyl peroxide, etc. Examples thereof include organic peroxides, azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. These may be used alone or in combination, but it is preferable to use a plurality of types of polymerization initiators having a decomposition temperature of 60 to 130 ° C. for obtaining a half-life of 10 hours.

(C) Suspension stabilizer Further, in the above production method, a suspension stabilizer may be used in order to stabilize the dispersibility of the droplets of the styrene monomer and the core resin particles. Such a suspension stabilizer is not particularly limited as long as it is conventionally used for suspension polymerization of a styrene monomer, and examples thereof include water-soluble substances such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone. And a poorly soluble inorganic compound such as tribasic calcium phosphate, hydroxyapatite, and magnesium pyrophosphate.
Moreover, when using a poorly soluble inorganic compound, an anionic surfactant is used together normally.

  Examples of such anionic surfactants include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzene sulfonates, alkyl naphthalene sulfonates, and dialkyl sulfosuccinate esters. Sulfates such as alkyl sulfoacetates, α-olefin sulfonates, higher alcohol sulfates, secondary higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, etc. And phosphoric acid ester salts such as alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

(D) Other components It should be noted that the composite resin particles have plasticizers, anti-binding agents, bubble regulators, cross-linking agents, fillers, flame retardants, flame retardant aids, lubricants, and coloring, as long as the physical properties are not impaired. You may add additives, such as an agent, a fusion promoter, an antistatic agent, and a spreading agent.

The composite resin particles can contain a plasticizer having a boiling point exceeding 200 ° C. under 1 atm in order to maintain good foam moldability even when the pressure of water vapor used at the time of heat foaming is low.
Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate and glycerin diacetomonostearate, adipic acid esters such as diisobutyl adipate, and plasticizers such as coconut oil. .
The content of the plasticizer in the composite resin particles is preferably 0.1 to 3.0% by mass.

Examples of the binding inhibitor include calcium carbonate, silica, zinc stearate, aluminum hydroxide, ethylene bis stearamide, tricalcium phosphate, and dimethyl silicon.
Examples of the air conditioner include ethylene bis stearamide and polyethylene wax.
As a crosslinking agent, 2,2-di-t-butylperoxybutane, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t -Organic peroxides such as butylperoxyhexane.
Examples of the filler include silicon dioxide produced synthetically or naturally.

Examples of the flame retardant include tris (2,3-dibromopropyl) isocyanurate, tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol A-bis (2,3-dibromo- 2-methylpropyl ether), tetrabromobisphenol A-bis (2,3-dibromopropyl ether) and the like.
Examples of the flame retardant aid include organic peroxides such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide and cumene hydroperoxide. It is done.
Examples of the lubricant include paraffin wax and zinc stearate.

  Coloring agents include furnace black, ketjen black, channel black, thermal black, acetylene black, carbon black such as graphite and carbon fiber, chromate such as chrome yellow, zinc yellow and barium yellow, and ferrocyanides such as bitumen Sulfides such as cadmium yellow and cadmium red, oxides such as iron black and red husk, silicates such as ultramarine blue, inorganic pigments such as titanium oxide, monoazo pigments, disazo pigments, azo lakes, condensed azo pigments, chelate azos Organic pigments such as azo pigments such as pigments, polycyclic pigments such as phthalocyanine, anthraquinone, perylene, perinone, thioindigo, quinacridone, dioxazine, isoindolinone, quinophthalone, and the like can be mentioned.

Examples of the fusion accelerator include stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride, sorbitan stearate, and polyethylene wax.
Examples of the antistatic agent include polyoxyethylene alkylphenol ether, stearic acid monoglyceride, polyethylene glycol and the like.
Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.

(E) Stirring Power required for stirring (Pv) required to stir the aqueous medium 1 m ³ including the core resin particles, styrenic monomers, and other dispersions and dissolved substances as required is 0.06-0. Stirring conditions adjusted to 8 kw / m ³ are preferred. The power required for stirring was 0. It is preferable that it is 1-0.5 kw / m < ³ >. This required power for stirring corresponds to the net energy per unit volume received by the contents in the reaction vessel.

Here, the power required for stirring refers to that measured in the following manner.
That is, an aqueous medium containing core resin particles, styrene-based monomers, and other dispersions and dissolved substances as necessary is supplied into a polymerization vessel of a polymerization apparatus, and an agitating blade is rotated at a predetermined number of rotations. Stir. At this time, the rotational driving load necessary to rotate the stirring blade is measured as a current value A ₁ (ampere). A value obtained by multiplying the current value A ₁ by an effective voltage (volts) is defined as P ₁ (watts).

Then, the stirring blade of the polymerization apparatus is rotated at the same rotation speed as described above in an empty state of the polymerization vessel, and the rotational driving load required to rotate the stirring blade is measured as a current value A ₂ (ampere). A value obtained by multiplying the current value A ₂ by an effective voltage (volt) is P ₂ (watts), and the required power for stirring can be calculated by the following formula. V (m ³ ) is the volume of the entire aqueous medium including the core resin particles, the styrene monomer, and other dispersions and dissolved substances as required.
Power required for stirring (Pv) = (P ₁ −P ₂ ) / V

The shape and structure of the polymerization vessel are not particularly limited as long as they are conventionally used for the polymerization of styrene monomers.
The stirring blade is not particularly limited as long as the power required for stirring can be set within a predetermined range.
Specifically, paddle blades such as V-type paddle blades, inclined paddle blades, flat paddle blades, fiddler blades, pull margin blades, turbine blades such as turbine blades and fan turbine blades, propeller blades such as marine propeller blades, etc. Can be mentioned. Of these stirring blades, paddle blades are preferable, and V-type paddle blades, inclined paddle blades, flat paddle blades, Ferdler blades, and pull margin blades are more preferable. The stirring blade may be a single-stage blade or a multi-stage blade.
Further, the size of the stirring blade is not particularly limited as long as the required power for stirring can be set within a predetermined range.
Furthermore, you may provide a baffle plate (baffle) in the superposition | polymerization container.

(3) Expandable particles Expandable particles include composite resin particles and a volatile foaming agent, and can be produced by impregnating composite resin particles with a volatile foaming agent by a known method.
When the temperature at which the composite resin particles are impregnated with the volatile foaming agent is low, it takes time for the impregnation, and the production efficiency of the expandable particles may be reduced. Since it may generate | occur | produce in large quantities, 50-130 degreeC is preferable and 60-100 degreeC is more preferable.

(A) Foaming agent The volatile foaming agent is not particularly limited as long as it is conventionally used for foaming polystyrene resins. For example, isobutane, n-butane, isopentane, n-pentane, neopentane, etc. Examples include volatile foaming agents such as aliphatic hydrocarbons having 5 or less carbon atoms, with butane-based foaming agents and pentane-based foaming agents being particularly preferred. Pentane can also be expected to act as a plasticizer.

The content of the volatile foaming agent in the foamable particles is usually in the range of 2 to 10% by weight, preferably in the range of 3 to 10% by weight, and particularly preferably in the range of 3 to 8% by weight.
If the content of the volatile foaming agent is small, for example, less than 2% by mass, it may not be possible to obtain a low-density foam molded product from the foamable particles, and the effect of increasing the secondary foaming power during in-mold foam molding Cannot be obtained, the appearance of the foamed molded product may deteriorate. On the other hand, when the content of the volatile foaming agent is large, for example, it exceeds 10% by mass, the time required for the cooling step in the production process of the foamed molded article using the foamable particles becomes long, and the productivity may be lowered.

(B) Foaming aid The foamable particles can contain a foaming aid together with the foaming agent.
The foaming aid is not particularly limited as long as it is conventionally used for foaming polystyrene resins. For example, aromatic organic compounds such as styrene, toluene, ethylbenzene, xylene, cyclohexane, methylcyclohexane, etc. Examples thereof include solvents having a boiling point of 200 ° C. or less under 1 atm, such as cycloaliphatic hydrocarbons, ethyl acetate, and butyl acetate.

The content of the foaming aid in the expandable particles is usually in the range of 0.3 to 2.5% by mass, and preferably in the range of 0.5 to 2% by mass.
When the content of the foaming aid is small, for example, less than 0.3% by mass, the plasticizing effect of the polystyrene resin may not be exhibited. On the other hand, if the content of the foaming aid is large and exceeds 2.5% by mass, the foamed molded product obtained by foaming the foamable particles may be shrunk or melted to deteriorate the appearance, or foamable. The time required for the cooling step in the production process of the foamed molded article using the particles may be long.

(4) Expanded particles (hereinafter also referred to as “pre-expanded particles”)
The foamed particles are obtained by pre-foaming the foamable particles to a predetermined bulk density by a known method, and examples thereof include batch-type foaming in which steam is introduced, continuous foaming, and release foaming under pressure.
The expandable particles of the present invention preferably have a bulk density in the range of 0.012 to 0.20 g / cm ³ .
When the bulk density of the expandable particles is less than 0.012 g / cm ³ , the foamed molded product tends to shrink and the appearance may be impaired.
On the other hand, if the bulk density of the expandable particles exceeds 0.20 g / cm ³ , the advantage of weight reduction as a foamed molded product may be impaired.
In the pre-foaming, air may be introduced simultaneously with steam when foaming as necessary.

(5) Foam molded body The foam molded body is a known method, for example, the foam particles are filled in a mold of a foam molding machine and heated again to foam the foam particles, and the foam particles are thermally fused. Can be obtained.
The foamed molded product of the present invention preferably has a density in the range of 0.012 to 0.20 g / cm ³ .
When the density of the foamed molded product is less than 0.012 kg / m ³ , the impact resistance may not be sufficient.
On the other hand, if the density of the foamed molded product exceeds 0.20 g / cm ³ , the weight of the foamed molded product increases and the transportation cost increases, which may be undesirable.

According to the present invention, the molding cycle of the foamed molded product can be shortened.
“Molding cycle” refers to the automatic operation of the molding machine, the operation of closing the mold, the filling particles filled in the mold, heating and cooling under desired conditions, and a predetermined surface pressure value. It means the time from when the mold is opened until the foamed molded product is taken out.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, the following examples are only illustrations of this invention and this invention is not limited only to the following examples.
In Examples and Comparative Examples, the obtained core resin particles, composite resin particles, expanded particles, and expanded molded articles were evaluated as follows.

<Dispersion state of polystyrene resin in core resin particles and composite resin particles>
A section is cut out from the core resin particle and the composite resin particle, and the section is embedded in an epoxy resin, and then an ultrathin section (thickness 70 nm) using an ultramicrotome (trade name: LEICA UL TRACUCT UCT, manufactured by Leica Microsystems). Create
Subsequently, the ultrathin section was photographed with a transmission electron microscope (TEM, manufactured by Hitachi High-Technologies Corporation, model: H-7600) at a magnification of 3500 times (5000 times as necessary), and the surface of the composite resin particles And a dispersion state of the polystyrene resin in the center part of the composite resin particles, and a dispersion state of the polystyrene resin of the core resin particles are photographed. Ruthenium tetroxide is used as the staining agent.

  Whether the component constituting the specific region in the TEM image is a “linear low density polyethylene resin” or “polystyrene resin”, the contrast of the component of the “polystyrene resin” is balanced with the surrounding resin. Since there is a case where it changes, not only the contrast depending on the dyeing state but also the distinctive lamellar structure observed in the “olefin resin” is discriminated.

<Average particle diameter of polystyrene resin fine particles in core resin particles>
The polystyrene resin fine particles dispersed in the linear low density polyethylene resin from the above TEM image showing the scale are substantially circular, indefinite, etc., and the longest and shortest diameters are measured. Calculate according to the formula.
(Particle diameter of polystyrene resin fine particles) = (longest diameter + shortest diameter) / 2 (μm)
Of the particle diameters of the polystyrene resin fine particles, an arbitrary average value of 20 is defined as the average particle diameter (μm) of the polystyrene resin fine particles.

<Average particle diameter of polystyrene resin fine particles in composite resin particles>
Similarly to the particle diameter of the polystyrene resin fine particles in the core resin particles, the average particle diameter (μm) of the polystyrene resin fine particles is obtained by the following formula.
(Particle diameter of polystyrene resin fine particles) = (longest diameter + shortest diameter) / 2 (μm)

<Area ratio of surface-layer polystyrene resin fine particles in composite resin particles>
From the TEM image on which the scale is displayed, the depth (up and down direction of the image) is 0.5 μm and the length (left and right direction of the image) is 5 μm from the surface of the composite resin particle in the TEM image obtained from an arbitrary observation point. In the range, the particle diameter of polystyrene resin fine particles of 0.25 μm to 0.80 μm was calculated. Next, the area ratio of the surface polystyrene resin fine particles is calculated as shown in the following formula.
When a part of polystyrene resin fine particles of 0.25 μm or more and 0.80 μm or less is included on the boundary line in the range of depth 0.5 μm and length 5 μm, it is included in the area of the following formula.
(Area ratio of surface polystyrene resin fine particles)
= (Total area of polystyrene resin fine particles A) / (area B) × 100 (%)
The total area A of polystyrene resin fine particles is the total area of polystyrene resin fine particles (PS fine particles) having a particle diameter of 0.25 to 0.80 μm, and is calculated by the following equation.
Σ [(particle diameter of PS fine particles of 0.25 to 0.80 μm / 2) ² × 3.14] (μm ² )
The area B is an area having a depth of 0.5 μm and a length of 5 μm, and is 0.5 × 5 (μm ² ).

<Absorbance ratio (D698 / D2850)>
The absorbance ratio (D698 / D2850) on the surface of the composite resin particles is measured in the following manner.
In addition, each light absorbency obtained from an infrared absorption spectrum says the height of the peak originating in the vibration of each resin component contained in a composite resin particle.
Ten randomly selected particles are subjected to particle cross-sectional analysis by infrared spectroscopic ATR measurement to obtain an infrared absorption spectrum. In this analysis, an infrared absorption spectrum in the depth range from the sample surface to several μm (about 2 μm) is obtained.
An individual absorbance ratio (D698 / D2850) is calculated from each infrared absorption spectrum, and the arithmetic average thereof is defined as the absorbance ratio.
Absorbances D698 and D2850 were measured under the following conditions using a measuring device sold under the trade name “Fourier Transform Infrared Spectrometer MAGNA 560” from Nicolet and “Thunder Dome” manufactured by Spectra-Tech as an ATR accessory. To do.

(Measurement condition)
High refractive index crystal seed: Ge (germanium)
Incident angle: 45 ° ± 1 °
Measurement region: 4000 cm ^{−1 to} 675 cm ⁻¹
Fractional dependence of measurement depth: No correction Number of reflections: 1 Detector: DTGS KBr
Resolution: 4cm ^-1
Number of integrations: 32 times Others: An infrared absorption spectrum is measured under the following conditions without contacting the sample, and the measured spectrum is used as the background. When measuring the sample, the measurement data is processed so that the background does not contribute to the measurement spectrum. In the ATR method, the intensity of the infrared absorption spectrum changes depending on the degree of adhesion between the sample and the high refractive index crystal. Therefore, the maximum load that can be applied by the “Thunder Dome” of the ATR accessory is applied to perform the measurement with a substantially uniform contact degree.

(Background measurement conditions)
Mode: Transparent Pixel size: 6.25 μm
Measurement region: 4000 cm ^{−1 to} 650 cm ⁻¹
Detector: MCT
Resolution: 8cm ^-1
Scan / pixel: 60 times Others: A process that does not participate in the measurement spectrum is performed using the infrared absorption spectrum obtained by measuring the barium fluoride crystal in the portion near the sample where there is no sample.

About the infrared absorption spectrum obtained on the above conditions, the peak process is performed as follows and each light absorbency is calculated | required.
Absorbance D698 at 698 cm ⁻¹ obtained from the infrared absorption spectrum is an absorbance corresponding to the absorption spectrum derived from the out-of-plane deformation vibration of the benzene ring contained in the styrene resin. In this absorbance measurement, peak separation is not performed even when other absorption spectra overlap at 698 cm ⁻¹ . Absorbance D698 is a straight line connecting the 2000 cm ^-1 and 870 cm ^-1 as a baseline, means the maximum absorbance between 710 cm ^-1 and 685cm ^-1.
Further, the absorbance D2850 at 2850 cm ⁻¹ obtained from the infrared absorption spectrum is an absorbance corresponding to an absorption spectrum derived from the CH ₂ symmetrical bending vibration of —C—CH ₂ hydrocarbon contained in the polyethylene resin. . In this absorbance measurement, peak separation is not performed even when other absorption spectra overlap at 2850 cm ⁻¹ . Absorbance D2850 is a straight line connecting the 3125Cm ^-1 and 2720cm ^-1 as a baseline, it means the maximum absorbance between 2875cm ^-1 and 2800 cm ^-1.

As a method for obtaining the composition ratio of polystyrene resin and polyethylene resin from the absorbance ratio, a plurality of types of standard samples are prepared by uniformly mixing polystyrene resin and polyethylene resin at a predetermined composition ratio, and each standard is prepared. A sample is subjected to particle surface analysis by ATR infrared spectroscopy to obtain an infrared absorption spectrum. The absorbance ratio is calculated from each of the obtained infrared absorption spectra. A calibration curve is drawn by taking the composition ratio (polystyrene resin ratio (% by mass) in the standard sample) on the vertical axis and the absorbance ratio (D698 / D2850) on the horizontal axis. Based on the calibration curve, the composition ratio of the polystyrene resin and the polyethylene resin in the composite resin particle of the present invention is determined from the absorbance ratio of the composite resin particle of the present invention.
The calibration curve is approximated by the following equation.
When D698 / D2850 <1.42, Y = 21.112X ₂
When 1.42 <(D698 / D2850) <8.24 Y = 28.415 Ln (X ₂ ) +20.072
In the formula, X ₂ = (D698 / D2850), Y = polystyrene resin amount (%)

<Gel fraction of composite resin particles>
1 g of composite resin particles precisely weighed using an electronic balance (Mettler) capable of measuring up to 4 decimal places in gram units is placed in a 200 ml capacity eggplant flask together with 100 ml of toluene and about 0.4 g of zeolite. Connect to cooling tube and place in oil bath at 130 ° C. Next, an appropriate amount of water is passed through the cooling pipe and heated for 24 hours.
Next, after removing the flask from the oil bath, the contents are immediately filtered using a wire mesh of 80 mesh (φ0.12 mm). Next, the insoluble matter and the zeolite in boiling toluene remaining on the wire mesh are left in an oven at 130 ° C. for 1 hour together with the wire mesh to remove the toluene, and vacuum drying is further performed for 2 hours. Thereafter, the solid matter remaining on the wire mesh and the zeolite are removed from the oven together with the wire mesh and allowed to cool in a desiccator for about 1 hour. Next, the total mass Wt (g) of the solid matter and zeolite remaining on the wire mesh is measured together with the wire mesh.
From the total mass Wt (g), the mass Wz (g) of the zeolite and the mass Wm (g) of the wire mesh, which have been precisely weighed in advance, are subtracted to calculate the mass Ws (g) of the solid, and further weighed. The ratio with respect to the composite resin particles Wb (g) is calculated as a gel fraction (mass%).
Gel fraction (mass%) = (Wt−Wz−Wm) / Wb × 100

<Average particle diameter of composite resin particles>
The particle diameter (median diameter: d50) having a cumulative mass of 50% in the cumulative mass distribution curve is defined as the average particle diameter of the composite resin particles.
Specifically, using a low tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.), sieve openings are 4.00 mm, 3.35 mm, 2.80 mm, 2.36 mm, 2.00 mm, 1.70 mm, 1 .40mm, 1.18mm, 1.00mm, 0.85mm, 0.71mm, 0.60mm, 0.50mm, 0.425mm, 0.355mm, 0.300mm, 0.250mm, 0.212mm and 0.180mm About 50 g of a sample is classified for 10 minutes using a JIS standard sieve (JIS Z8801-1: 2006), and the sample mass on the sieve mesh is measured. A cumulative mass distribution curve is created from the obtained results, and the particle diameter at which the cumulative mass is 50% is defined as the average particle diameter (mm).

<Bulk density of expanded particles>
The graduated cylinder having an inner volume of 100 cm ³ mass B (g) of measured, the expanded beads 110～120Cm ^3, is naturally dropped into the graduated cylinder through a funnel. If the foam particles are clumped and adhere to the funnel, break them apart with a glass rod. The expanded particles rising in the graduated cylinder are removed by moving the straight ruler along the edge of the graduated cylinder, and the mass A (g) of the graduated cylinder containing the expanded particles is measured. The bulk density of the expanded particles is calculated by the following formula.
Bulk density (g / cm ³ )
= [Mass A (g) -mass B (g)] / volume of measuring cylinder (100 cm ³ )

<Density of foam molding>
The volume Va (cm ³ ) and the mass W (g) of the foam molded body obtained after foam molding are measured, and the density of the foam molded body is obtained from the following formula.
Density (g / cm ³ ) of foam molded article = mass W (g) / volume Va (cm ³ )

<Chemical resistance>
Three flat rectangular plate-shaped test pieces having a length of 100 mm, a width of 100 mm and a thickness of 20 mm are cut out from the foamed molded article and left to stand for 24 hours under the conditions of 23 ± 2 ° C. and humidity of 50 ± 5%. In addition, a test piece is cut out from a foaming molding so that the upper surface whole surface of a test piece may be formed from the surface of a foaming molding.
Next, 1 g of different chemicals (gasoline, kerosene, dibutyl phthalate (DBP)) is uniformly applied to the top surfaces of the three test pieces, and left for 60 minutes under the conditions of 23 ± 2 ° C. and humidity of 50 ± 5%. . Then, the chemical | medical agent is wiped off from the upper surface of a test piece, the upper surface of a test piece is visually observed, and it evaluates based on the following reference | standard.
○: Good No change △: Slightly bad Surface softening ×: Bad Surface depression (shrinkage)

<Fusion rate of foam molding>
A notch with a depth of 2 mm is placed on one surface (300 mm length x 400 mm width surface) across the entire width at the center in the horizontal direction of a 300 mm long x 400 mm wide x 50 mm high rectangular foam molded body. Until the foamed molded product breaks in the direction of expanding the width or until both ends abut. Next, the fractured surface is observed, and the number of foamed particles that have been internally fractured and peeled off at the interface are visually measured. Next, the ratio of the internally broken foam particles to the total number of the foam particles peeled at the interface and the internally broken foam particles is calculated, and expressed as a percentage to obtain a fusion rate (%). It measures about arbitrary ranges of 100-150 pieces.

<Appearance of foam molding>
The appearance of the foamed molded product is visually observed and evaluated according to the following criteria.
That is, the larger the numerical value, the smaller the gap between the particles, and 3 or more expressed with a perfect score of 5 points.
5: Gaps between particles are not found 4: Gaps are partially seen 3: Gaps are seen in some places, but acceptable level 2: Gaps are noticeable 1: Gaps are noticeable, and there is no commercial value

<Impact strength of foam molding>
A flat rectangular test piece having a length of 215 mm, a width of 40 mm, and a thickness of 20 mm is cut out from the foam molded article. Then, in accordance with JIS K7211: 1976 “General Rules for Hard Plastic Drop Weight Impact Test Method”, a test piece was installed between a pair of fulcrums arranged at intervals of 150 mm to drop a 321 g steel ball. The falling ball impact value, that is, the 50% breaking height (cm) is calculated based on the following equation. However, the maximum height of the steel ball is 120 cm.
50% fracture height H50 = Hi + d [Σ (i × ni) /N±0.5]

The symbols in the formula mean the following.
H50: 50% fracture height (cm)
Hi: Height of test piece at height level (i) 0 (cm)
Height at which the specimen is expected to break d: Height interval (cm) when raising and lowering the height of the specimen
i: Height level when Hi is 0, and the height level increases or decreases by 1
(I = ...- 3, -2, -1,0,1,2,3, ...)
ni: number of test pieces destroyed (or not destroyed) at each level N: total number of test pieces destroyed (or not destroyed) (N = Σni)
Use whichever data is greater
In case of the same number, either one may be adopted. ± 0.5: Negative when using destroyed data,
Take positive when using unbroken data

<Compressive strength of foam molding>
Measured according to JIS K7220: 2006.
A test piece obtained by cutting a foamed molded product into a length of 50 mm, a width of 50 mm, and a thickness of 25 mm is compressed under a compression speed of 10 mm / min, and the strength (MPa) at 10% compression is measured.

<Bending strength of foam molding>
The bending strength (average maximum bending strength) of the foam is measured according to the method described in JIS K7221-2: 2006.
Five rectangular parallelepiped-shaped test pieces having a length of 25 mm, a width of 130 mm, and a thickness of 20 mm (on one side of the skin) are cut out from the foamed molded article and left for 24 hours under conditions of 23 ° C. ± 2 ° C. and humidity of 50 ± 5%. This test piece is measured for bending strength (MPa) under the following measurement conditions using a bending strength measuring instrument (Orientec Co., Ltd., model: UCT-10T).

(Measurement condition)
Test speed: 10 mm / min Distance between fulcrums: 100 mm
Deflection amount: 50mm
Pressure wedge: 5R
Support base: 5R

<Molding cycle>
In the molding cycle, the automatic operation of the molding machine is started, the operation of closing the mold is started, the expanded particles are filled in the mold, heating and cooling are performed under desired conditions, and a predetermined surface pressure value is obtained. This is the time from when the mold is opened until the foamed molded product is taken out, and is counted (seconds) in the foam molding process.

Example 1
(Preparation of core resin particles)
90 parts by mass of a linear low density polyethylene resin (made by Nippon Polyethylene Co., Ltd., trade name “Harmolex NF-444A”) and polystyrene resin (made by Toyo Styrene Co., Ltd., trade name “Toyostyrene GP HRM-26”) 10 parts by mass was put into a tumbler mixer and mixed for 5 minutes.
Next, the cylinder temperature of the obtained resin mixture was adjusted so that the resin temperature at the center of the resin flow path of the extruder head portion was 280 ° C. It supplied to the φ65mm-50mm tandem type | mold extruder (Toshiba Machine Co., Ltd. make, model: SE-65) provided with the four notch screw, melt-kneaded, and granulated by the underwater cutting system. At this time, the pressure of the head part was 19 MPa, the resin temperature at the die inlet was 245 ° C., the pressure at the inlet of the resin flow path of the die was 15 MPa, and core resin particles cut into an average of 0.4 mg / piece were obtained. A TEM image of the obtained nuclear resin particles is shown in FIG.

(Production of composite resin particles)
To an autoclave with an internal volume of 100 liters equipped with a stirrer, 40 kg of water, 356 g of magnesium pyrophosphate as a dispersant, and 7.0 g of sodium dodecylbenzenesulfonate as a surfactant are added, and the power required for stirring is 0.20 kw / m ^3. To obtain a dispersion medium, and 8.8 kg of the core resin particles were further added to disperse the core resin particles to obtain a suspension (dispersion).
Next, the temperature of the dispersion of the core resin particles was adjusted to 60 ° C., and 4.4 kg of styrene prepared by dissolving 11.0 g of dicumyl peroxide as a polymerization initiator in advance over 30 minutes. Added quantitatively. Thereafter, the power required for stirring was adjusted to 0.22 kw / m ³ , and the core resin particles were impregnated with styrene by stirring for 1 hour while maintaining the temperature of the dispersion at 60 ° C.
The dispersion was then heated at a rate of temperature rise of 0.78 ° C./min and held at 135 ° C. for 2 hours. Next, the temperature was raised to 140 ° C. at 0.5 ° C./min and annealed for 2 hours, and then the dispersion was cooled to 115 ° C. at a temperature drop rate of 0.5 ° C./min.

  Then, 11.5 g of sodium dodecylbenzenesulfonate as a surfactant was added to the dispersion, and after 10 minutes, 109 g of t-butylperoxybenzoate as a polymerization initiator and 200 g of ethylenebisstearic acid amide as a bubble regulator were previously added. And 26.0 kg of styrene prepared by dissolving 800 g of butyl acrylate was added quantitatively over 4 hours.

Next, the dispersion was held at 115 ° C. for 1 hour, heated to 140 ° C. at a temperature increase rate of 0.66 ° C./min, and held at that temperature for 2 hours. Thereafter, the dispersion was cooled to 30 ° C. at a temperature drop rate of 0.94 ° C./min.
The contents were taken out from the autoclave, 400 ml of 20% hydrochloric acid was added to decompose the magnesium pyrophosphate adhering to the surface of the resin particles, and after washing, the contents were dehydrated with a centrifuge and attached to the surface with an air flow dryer. Water was removed to obtain composite resin particles.
The evaluation result about the obtained composite resin particle is shown in Table 1 and FIG. FIG. 2 is a TEM image of (a) particle surface portion and (b) particle central portion in the obtained composite resin particle.

(Production of expandable particles)
Next, 2000 g of the composite resin particles after removal, 2000 g of water, and 2.0 g of sodium dodecylbenzenesulfonate were again put into a 5 L autoclave equipped with a stirrer, and butane as a blowing agent while stirring at a required power of stirring of 0.20 kw / m ^3. (Ratio of isobutane 3: n-butane 7) 624 ml (360 g) was injected. Thereafter, the temperature was raised to 70 ° C., and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out from the 5L autoclave, dehydrated and dried, and obtained expandable particle | grains.

(Production of expanded particles)
Next, the obtained expandable particles were put into a pre-foaming machine with a stirrer having an internal volume of 40 L and stirred while introducing steam having a pressure of 0.02 MPa to pre-expand the expandable particles. At this time, by adjusting the input amount of the foamed particles, by taking out the pre-foaming machine in volume 30L, to obtain expanded beads having a bulk density of 0.033 g / cm ³ and 0.020 g / cm ^3.

(Production of foamed molded product)
Stored in a constant temperature room for 7 days after pre-foaming, fill the foamed particles in a mold of a foam molding machine (manufactured by Sekisui Koki Co., Ltd., model: ACE-3SP), and then pressurize the mold 0.08MPa steam is introduced under heating conditions of mold heating for 2 seconds, one heating for 5 seconds, reverse one heating for 2 seconds, double-sided heating for 10 seconds to foam the foamed particles, and after 10 seconds for water cooling, foaming is performed by cooling in vacuum. When the surface pressure value of the molded body dropped to 0.02 MPa, it was removed from the mold and the molding cycle (seconds) was counted. There was thus obtained the density of 0.033 g / cm ³ and 0.020 g / cm ^3, the foamed molded article of a rectangular parallelepiped shape of vertical 300 mm × horizontal 400 mm × thickness 50 mm.
About the obtained foaming molding, the physical property was measured and evaluated. The results are shown in Table 1.

(Example 2)
80 parts by mass of a linear low density polyethylene resin (made by Nippon Polyethylene Co., Ltd., trade name “Harmolex NF-444A”), polystyrene resin (made by Toyo Styrene Co., Ltd., trade name “Toyostyrene GP HRM-26”) Nuclear resin particles were obtained in the same manner as in Example 1 except that the amount was 20 parts by mass.
Next, 40 kg of water, 356 g of magnesium pyrophosphate as a dispersant, and 7.0 g of sodium dodecylbenzenesulfonate as a surfactant are added to an autoclave having an internal volume of 100 liters equipped with a stirrer, and the required power for stirring is 0.20 kW. The dispersion medium was obtained by stirring at / m ³ , and 14.8 kg of the core resin particles were further added to disperse the core resin particles to obtain a suspension (dispersion).

Next, the temperature of the dispersion of the core resin particles is adjusted to 60 ° C., and 7.4 kg of styrene prepared by dissolving 18.5 g of dicumyl peroxide as a polymerization initiator in advance is added over 30 minutes. Added quantitatively. Thereafter, the power required for stirring was adjusted to 0.22 kw / m ³ , and the core resin particles were impregnated with styrene by stirring for 1 hour while maintaining the temperature of the dispersion at 60 ° C.
The dispersion was then heated at a rate of temperature rise of 0.78 ° C./min and held at 135 ° C. for 2 hours. Next, the temperature was raised to 140 ° C. at 0.5 ° C./min and annealed for 2 hours, and then the dispersion was cooled to 115 ° C. at a temperature drop rate of 0.5 ° C./min.

Next, 11.5 g of sodium dodecylbenzenesulfonate as a surfactant was added to the dispersion, and after 10 minutes, 88 g of t-butylperoxybenzoate as a polymerization initiator and 200 g of ethylenebisstearic acid amide as a bubble regulator were previously added. Then, 17.2 kg of styrene prepared by dissolving butyl acrylate and 600 g of butyl acrylate was added quantitatively over 4 hours.
Thereafter, in the same manner as in Example 1, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained, and measured and evaluated. The results are shown in Table 1.

(Example 3)
70 parts by mass of linear low density polyethylene resin (trade name “Harmolex NF-444A” manufactured by Nippon Polyethylene Co., Ltd.), polystyrene resin (trade name “Toyostyrene GP HRM-26” manufactured by Toyo Styrene Co., Ltd.) Nuclear resin particles were obtained in the same manner as in Example 1 except that the amount was 30 parts by mass.
Next, 40 kg of water, 356 g of magnesium pyrophosphate as a dispersant, and 7.0 g of sodium dodecylbenzenesulfonate as a surfactant are added to an autoclave having an internal volume of 100 liters equipped with a stirrer, and the required power for stirring is 0.20 kW. The dispersion medium was obtained by stirring at / m ³ , and 22.8 kg of the core resin particles were further added to disperse the core resin particles to obtain a suspension (dispersion).

Next, the temperature of the dispersion of the core resin particles was adjusted to 60 ° C., and 9.8 kg of styrene prepared by dissolving 24.5 g of dicumyl peroxide as a polymerization initiator in advance over 30 minutes was added over 30 minutes. Added quantitatively. Thereafter, the power required for stirring was adjusted to 0.22 kw / m ³ , and the core resin particles were impregnated with styrene by stirring for 1 hour while maintaining the temperature of the dispersion at 60 ° C.
The dispersion was then heated at a rate of temperature rise of 0.78 ° C./min and held at 135 ° C. for 2 hours. Next, the temperature was raised to 145 ° C. at 0.5 ° C./min and annealed for 2 hours, and then the dispersion was cooled to 115 ° C. at a temperature drop rate of 0.5 ° C./min.

Next, 11.5 g of sodium dodecylbenzenesulfonate as a surfactant was added to the dispersion, and after 10 minutes, 60 g of t-butylperoxybenzoate as a polymerization initiator and 200 g of ethylenebisstearic acid amide as a bubble regulator were previously added. 6.8 kg of styrene prepared by dissolving butyl acrylate and 600 g of butyl acrylate was added quantitatively over 2 hours.
Thereafter, in the same manner as in Example 1, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained, and measured and evaluated. The results are shown in Table 1.

(Comparative Example 1)
In the production of the composite resin particles, the core resin particles, the composite resin particles, the expandable particles, the expanded particles, and the expanded molded articles are obtained and measured and evaluated in the same manner as in Example 1 except that the annealing process is not performed. did. The results are shown in Table 1 and FIG. FIG. 3 is a TEM image of (a) particle surface portion and (b) particle central portion in the obtained composite resin particle.

(Comparative Example 2)
Nuclear resin particles were obtained in the same manner as in Example 1 except that the amount was 100 parts by mass of a linear low density polyethylene resin (trade name “Harmolex NF-444A” manufactured by Nippon Polyethylene Co., Ltd.).
Next, 40 kg of water, 356 g of magnesium pyrophosphate as a dispersant, and 7.0 g of sodium dodecylbenzenesulfonate as a surfactant are added to an autoclave having an internal volume of 100 liters equipped with a stirrer, and the required power for stirring is 0.20 kW. The dispersion medium was obtained by stirring at / m ³ , and 12.0 kg of the core resin particles were further added to disperse the core resin particles to obtain a suspension (dispersion).

Next, the temperature of the dispersion of the core resin particles is adjusted to 60 ° C., and 6.0 kg of styrene prepared by dissolving 15.0 g of dicumyl peroxide as a polymerization initiator in advance is added over 30 minutes. Added quantitatively. Thereafter, the power required for stirring was adjusted to 0.22 kw / m ³ , and the core resin particles were impregnated with styrene by stirring for 1 hour while maintaining the temperature of the dispersion at 60 ° C.
The dispersion was then heated at a rate of temperature rise of 0.78 ° C./min and held at 135 ° C. for 2 hours. Next, without performing annealing treatment, the dispersion was cooled to 115 ° C. at a temperature lowering rate of 0.5 ° C./min.

Subsequently, 11.5 g of sodium dodecylbenzenesulfonate as a surfactant was added to the dispersion, and after 10 minutes, 98 g of t-butylperoxybenzoate as a polymerization initiator and 200 g of ethylenebisstearic acid amide as a bubble regulator were previously prepared. And 21.4 kg of styrene prepared by dissolving 600 g of butyl acrylate was added quantitatively over 4 hours.
Thereafter, in the same manner as in Example 1, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained, and measured and evaluated. The results are shown in FIG. FIG. 4 is a TEM image of (a) particle surface portion and (b) particle central portion in the obtained composite resin particle.

(Comparative Example 3)
As a polyethylene resin, ethylene-vinyl acetate copolymer resin (manufactured by Nippon Polyethylene Co., Ltd., trade name “NOVATEC EVA LV-115”) is 100 parts by mass, and the resin temperature at the center of the resin flow path of the extruder head is 220 ° C. Except for the above, nuclear resin particles were obtained in the same manner as in Example 1. At this time, the pressure at the head was 18 MPa, the resin temperature at the die inlet was 240 ° C., and the pressure at the resin flow path inlet of the die was 16 MPa. Next, 48 kg of water was placed in an autoclave with an internal volume of 100 liters equipped with a stirrer. Then, 320 g of magnesium pyrophosphate as a dispersing agent and 7.7 g of sodium dodecylbenzenesulfonate as a surfactant were added, and stirred with a required power of stirring of 0.95 kw / m 3 to obtain a dispersion medium. Further, 9.6 kg of the core resin particles Was added to disperse the core resin particles to obtain a suspension (dispersion).

Next, a solution in which 83.2 g of benzoyl peroxide and 192 g of t-butylperoxybenzoate were dissolved as a polymerization initiator was added to 4.8 kg of styrene. Thereafter, the core resin particles were impregnated with styrene by stirring while maintaining at 70 ° C. and maintaining for 30 minutes.
Next, the temperature was raised to 85 ° C., and 17.6 kg of styrene was added quantitatively over 3 hours and 40 minutes. The temperature was further raised to 125 ° C. and maintained for 30 minutes. Next, after cooling at 1 ° C./min, the contents are taken out of the autoclave, 400 ml of 20% hydrochloric acid is added to decompose magnesium pyrophosphate adhering to the surface of the resin particles, and after washing, the contents are dehydrated with a centrifuge. Then, the water adhering to the surface was removed with an airflow drying device to obtain composite resin particles.
Thereafter, in the same manner as in Example 1, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained, and measured and evaluated. The results are shown in Table 1.

From the results in Table 1, it can be seen that the composite resin particles of Examples 1 to 3 can shorten the molding cycle of the foamed molded product.
On the other hand, it turns out that the resin particle of Comparative Examples 1-3 is inferior to the composite resin particle of Examples 1-3.

Claims (10)

Polystyrene composite resin particles containing a linear low density polyethylene resin and a polystyrene resin in a mass ratio of 50:50 to 15:85,
The polystyrene composite resin particles have a particle diameter of 0.25 to 0.80 μm in a range of 0.5 μm depth and 5 μm length from the particle surface in a TEM image obtained from an arbitrary observation point on the particle surface layer. Polystyrene-based composite resin particles, wherein the polystyrene-based resin particles have an area ratio in the range of 5 to 45%.   The polystyrene composite resin particles according to claim 1, wherein the polystyrene composite resin particles have a sea-island structure of the polystyrene resin at the center of the particles. 3. The polystyrene-based composite resin particle according to claim 1 or 2, which contains 10 to 35 mass% of a gel content insoluble in toluene when about 1 g of the polystyrene composite resin particles is treated with 100 ml of toluene heated in an oil bath at 130 ° C. 3. Polystyrene composite resin particles.   The polystyrene composite resin particles according to any one of claims 1 to 3, wherein the polystyrene composite resin particles have an average particle diameter of 0.5 to 3.0 mm. The polystyrene composite resin particles, its absorbance 698cm from polystyrene resin obtained from an infrared absorption spectrum of the particle surface ^-1 (D698) and linear low density absorbance of the polyethylene resin derived 2850cm ^-1 (D2850) The polystyrene-based composite resin particles according to any one of claims 1 to 4, having an absorbance ratio (D698 / D2850) of 0.5 to 2.5.   Expandable particle | grains containing the polystyrene type composite resin particle as described in any one of Claims 1-5, and a volatile foaming agent.   Expanded particles obtained by pre-expanding the expandable particles according to claim 6. The foamed particle according to claim 7, wherein the foamed particle has a bulk density of 0.012 to 0.20 g / cm ³ .   A foam-molded article obtained by foam-molding the foamed particles according to claim 7 or 8. It is a manufacturing method of the polystyrene system composite resin particles according to any one of claims 1 to 5,
Water medium in, the nucleus resin particles mixed resin containing a linear low-density polyethylene resin and polystyrene resin, after absorbing the styrene monomer, the step of polymerizing the styrene monomer When the steps of a Neil thereafter, further by polymerizing while absorbing the styrene monomer, method of manufacturing polystyrene composite resin particles which comprises the steps of: obtaining a polystyrene composite resin particles.