JP5690632B2 - Polypropylene resin particles for seed polymerization, process for producing the same, composite resin particles, expandable composite resin particles, pre-expanded particles, and expanded molded body - Google Patents

Description

  The present invention relates to polypropylene resin particles for seed polymerization, a method for producing the same, composite resin particles, expandable composite resin particles, pre-expanded particles, and a foam-molded article. More specifically, the present invention relates to a polypropylene resin particle for seed polymerization that can obtain a foam molded article having a high multiple, black, excellent appearance, and high retardance, and a method for producing the same. The present invention also relates to composite resin particles, expandable composite resin particles, pre-expanded particles, and expanded molded articles obtained from polypropylene resin particles for seed polymerization.

  Conventionally, foam molded products containing polystyrene resin or olefin resin as a resin component have excellent physical properties such as molding processability, heat insulation, impact resistance and buffering properties. It is widely used as a member for automobiles.

  In particular, when the foamed molded product is used for an automotive interior member, it is strongly desired to be colored in black, and a beautiful appearance is required. In addition, slow flammability is essential. For this reason, from the above viewpoint, Patent Documents 1 and 2 describe foamed molded articles containing carbon black and a flame retardant as black molded articles having excellent appearance and high retardability.

JP 2008-239794 A JP 2004-263033 A

  At present, from the viewpoint of weight reduction and cost reduction of the foamed molded product, in addition to an excellent appearance, it is desired that the foamed molded product have a higher magnification and a lower specific gravity. However, when resin particles, foamable composite resin particles, etc. used as raw materials for producing foamed molded products contain carbon black, the slow-flammability of the foamed molded products is ensured as the number of expanded foamed products increases. There are things that cannot be done. In addition, carbon black may hinder foaming, and it may not be possible to increase the magnification of the foamed molded product. Similarly, when the foamed molded product is made higher in magnification, uneven coloration and localization of the carbon black may cause uneven color in the foamed molded product.

  On the other hand, although it is described that the foam molded articles described in Patent Documents 1 and 2 are black and excellent in appearance and have high retardability, they are not always satisfactory from the viewpoint of increasing the magnification and reducing the specific gravity. It wasn't going to be good.

  Therefore, in view of these points, it is an object to provide a foamed molded article having a high multiple, black, excellent appearance, and high retardance. Another object of the present invention is to provide resin particles from which the foamed molded product can be obtained.

Thus, according to the present invention, carbon black is contained in a ratio of 2 to 10 parts by mass in 100 parts by mass of resin particles containing a polypropylene resin as a resin component,
In the transmission electron micrograph obtained by photographing a 10 μm × 10 μm portion of the resin particle surface at a magnification of 2000, a dispersion structure of the carbon black having an average area of 1.0 × 10 ^{4 to} 9.9 × 10 ⁴ nm ² is obtained. Polypropylene resin particles for seed polymerization having
Provided is a polypropylene resin particle for seed polymerization, wherein the polypropylene resin particle for seed polymerization has the dispersion structure with an average particle diameter of 110 to 350 nm in the transmission electron micrograph .

  Moreover, according to this invention, the manufacturing method of the polypropylene resin particle for seed polymerization which can obtain the said polypropylene resin particle for seed polymerization is also provided.

  Moreover, according to this invention, the composite resin particle which can be obtained from the said polypropylene resin particle for seed polymerization is also provided.

  Moreover, according to this invention, the expandable composite resin particle which can be obtained from the said composite resin particle is also provided.

  The present invention also provides pre-expanded particles that can be obtained from the expandable composite resin particles.

  Moreover, according to this invention, the foaming molding which can be obtained from the said pre-expanded particle is also provided.

Since the polypropylene resin particles for seed polymerization of the present invention contain carbon black in a suitable ratio in the resin component, the foamed molded product obtained from the polypropylene resin particles of the present invention has a beautiful appearance, and further has a desired appearance. Even at a high magnification, it can have slow flame retardancy. The polypropylene resin particles of the present invention have an average area of carbon black of 1.0 × 10 ^{4 to} 9.9 × 10 in a transmission electron micrograph of a 10 μm × 10 μm portion of the resin particle surface taken at a magnification of 2000 ×. It has a dispersion structure that is ⁴ nm ² . This indicates that carbon black is uniformly dispersed in the resin component. For this reason, compared with the case where carbon black is unevenly distributed in the resin component or the case where carbon black is coarse, the foamed molded article of the present invention is more excellent in appearance and retarding property and can have a high multiple. .
Therefore, according to the present invention, it is possible to provide seed polymerization polypropylene-based resin particles that can obtain a foamed molded article having a high multiple, black, excellent appearance, and high retardability.

  In addition, according to the present invention, when the polypropylene resin particles for seed polymerization have a dispersion structure of 70 to 150 in the transmission electron micrograph, carbon black is more uniformly dispersed in the resin component. Furthermore, it is possible to provide polypropylene resin particles for seed polymerization that can obtain a foamed molded article having a high multiple, black, excellent appearance, and high retardability.

  In addition, according to the present invention, when the polypropylene resin particles for seed polymerization have a dispersion structure with an average particle diameter of 110 to 350 nm in the transmission electron micrograph, carbon black is more uniformly contained in the resin component in this case as well. Since it is dispersed, it is possible to provide a polypropylene resin particle for seed polymerization that can obtain a foamed molded article having a higher multiple, a more excellent appearance, and a high flame retardancy.

  Moreover, according to the present invention, when the polypropylene resin particles for seed polymerization have an average particle size of 0.5 to 1.4 mm, the average particle size in a range suitable for the resin particles to produce a foamed molded product. Therefore, it is possible to provide a polypropylene resin particle for seed polymerization that can obtain a foamed molded article having a higher magnification, excellent appearance, and high retardability.

  According to the present invention, when a resin composition containing carbon black and a polypropylene resin are supplied to an extruder and melt-kneaded, the carbon black can be more uniformly dispersed in the polypropylene resin. Further, it is possible to provide a simpler method for producing polypropylene resin particles for seed polymerization that can obtain a foamed molded product having a black color, excellent appearance, and high retardability.

  According to the present invention, a foamed molded article having a high multiple, black, excellent appearance, and high retarding flammability is obtained by seed polymerizing the polypropylene resin particles for seed polymerization of the present invention with a styrene monomer. It is possible to provide composite resin particles capable of obtaining the above.

  Moreover, according to the present invention, when the composite resin particles contain 100 to 400 parts by mass of the polystyrene resin with respect to 100 parts by mass of the polypropylene resin, the composite resin particles preferably use a polystyrene resin with excellent foamability. Therefore, it is possible to provide a composite resin particle that has a higher magnification, is blacker, has an excellent appearance, and can obtain a foamed molded article having high retardability.

  Moreover, according to this invention, a flame retardant is a ratio of 1.5-5.0 mass parts with respect to 100 mass parts of composite resin particles, and a flame retardant adjuvant is 0.3-2.0 mass parts. When it is included in the ratio, it is possible to provide composite resin particles having a high multiple, black, excellent appearance, and capable of obtaining a foamed molded article having high retardability.

  ADVANTAGE OF THE INVENTION According to this invention, the expandable composite resin particle which can obtain the foaming molding which has a high magnification, is black, is excellent in an external appearance, and has a high flame retardance can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the pre-expanded particle which can obtain the foaming molding which has a high magnification, is black, is excellent in an external appearance, and has a high flame retardance can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the foaming molding which has a high magnification, is black, is excellent in an external appearance, and has high retardance property.

  Moreover, according to this invention, it can provide the foaming molding which has a high multiple of 35-50 times, is black, is excellent in an external appearance, and has a high slow-flammability.

2 is a transmission electron micrograph of the surface of polypropylene resin particles in Example 1. FIG. 2 is a transmission electron micrograph of the surface of polypropylene resin particles of Comparative Example 1. FIG. 4 is a transmission electron micrograph of the surface of polypropylene resin particles of Comparative Example 2. It is a figure which shows the surface of the foaming molding in the case of external appearance evaluation of a foaming molding.

The feature of the present invention is that carbon resin is contained in a proportion of 2 to 10 parts by mass in 100 parts by mass of resin particles containing a polypropylene resin as a resin component.
In the transmission electron micrograph obtained by photographing a 10 μm × 10 μm portion of the resin particle surface at a magnification of 2000, a dispersion structure of the carbon black having an average area of 1.0 × 10 ^{4 to} 9.9 × 10 ⁴ nm ² is obtained. It is a polypropylene resin particle for seed polymerization.

  In the present invention, the dispersion structure means an aggregate of aggregates (agglomerated structure) such as a co-continuous dispersion structure and a granular dispersion structure. Moreover, an average area means the average value of the measurement area per dispersion | distribution structure confirmed in a transmission electron micrograph (TEM).

  Specifically, the resin particles of the present invention are resin particles containing carbon black in a proportion of 2 to 10 parts by mass in 100 parts by mass of resin particles containing a polypropylene resin as a resin component. For this reason, the foam molded article of the present invention has a beautiful appearance due to the coloring effect of carbon black. Moreover, since the polypropylene resin particles of the present invention contain carbon black in a suitable ratio, the carbon black does not hinder the foamability of the resin component, and a high-magnification foamed molded product can be obtained.

On the other hand, the resin particles of the present invention have a carbon black average area of 1.0 × 10 ^{4 to} 9.9 × 10 ⁴ in a transmission electron micrograph obtained by photographing a 10 μm × 10 μm portion of the resin particle surface at a magnification of 2000 times. It has a dispersion structure that is nm ² . That is, the polypropylene resin particles of the present invention have a carbon black dispersed phase having a specific size and a uniform size in a continuous phase composed of a resin component. More specifically, the polypropylene resin particles of the present invention have a so-called sea-island structure having a sea part made of a resin component and an island part made of carbon black. This indicates that the carbon black of the present invention exists uniformly and in a specific size in the polypropylene resin particles.

  Carbon black is also uniform in the composite resin particles obtained by performing seed polymerization using the polypropylene resin particles of the present invention as seed particles, and then in the obtained expandable resin particles, pre-expanded particles, and foamed molded product. Will be distributed. As a result, the foamed molded article of the present invention has a beautiful appearance and high retardability without causing uneven color due to uneven distribution of carbon black, a decrease in retardability, and the like.

  On the other hand, when carbon black is coarse or when these are unevenly distributed, color unevenness occurs in the foamable composite resin. Furthermore, the coarse portion of the carbon black may be the starting point, which may reduce the slow flame retardance. On the other hand, by dispersing carbon black in a specific size, as a result, the foamed molded product of the present invention can have a high multiple while maintaining a beautiful appearance and ensuring slow flammability.

Therefore, according to the present invention, it is possible to provide seed polymerization polypropylene-based resin particles that can obtain a foamed molded article having a high multiple, black, excellent appearance, and high retardability.
Hereinafter, the polypropylene resin particles for seed polymerization of the present invention, the production method thereof, composite resin particles, expandable composite resin particles, pre-expanded particles, and foamed molded products will be described in detail.

The foamed molded article of the present invention is
(1) A melt-kneading step for obtaining polypropylene-based resin particles for seed polymerization by melt-kneading carbon black and a polypropylene-based resin;
(2) A seed polymerization step for obtaining composite resin particles by seed polymerization of a monomer component to polypropylene resin particles for seed polymerization;
(3) an impregnation step of obtaining expandable composite resin particles by impregnating the composite resin particles with a foaming agent;
(4) A pre-foaming step for obtaining pre-foamed particles by pre-foaming expandable composite resin particles; and (5) a production method including a foam molding step for obtaining a foam-molded product by foam-molding the pre-foamed particles. be able to.

(Polypropylene resin particles for seed polymerization)
In the present invention, the polypropylene resin particles for seed polymerization mean resin particles used at the time of seed polymerization, so-called seed particles, and also mean resin particles containing at least a polypropylene resin and carbon black as resin components. .

  It should be noted that the mass ratio between the raw materials used, such as raw material monomers, raw material resins, and other components, and the resin in the polypropylene resin particles for seed polymerization, composite resin particles, expandable composite resin particles, pre-expanded particles, and foam molded products The mass ratio of components and other components is substantially the same.

  In the present invention, the polypropylene resin means a propylene homopolymer or a copolymer of a propylene monomer as a main component and another monomer component copolymerizable with the propylene monomer. Moreover, a propylene monomer being a main component means that a propylene monomer occupies 50 mass parts or more in 100 mass parts of all the monomer components. Furthermore, a propylene homopolymer means that a propylene monomer occupies 93 mass parts or more in 100 mass parts of all the monomer components.

  Specifically, as a polypropylene resin, for example, propylene homopolymer, ethylene-propylene copolymer, propylene-acrylic acid copolymer, propylene-α-olefin copolymer, propylene-vinyl acetate copolymer, and propylene -Polymers such as methyl methacrylate copolymer may be mentioned. In the present invention, since desired physical properties can be obtained more easily, a propylene-ethylene copolymer is preferred as the polypropylene resin.

  On the other hand, as long as the desired physical properties are not affected, the polypropylene resin may be used alone or in combination of two or more. Moreover, when using a copolymer as a polypropylene resin, the copolymer may be a random copolymer or a block copolymer.

The polypropylene resin of the present invention preferably has a Mn of 50 × 10 ^{3 to} 150 × 10 ³ and a Mw / Mn of 2.0 to 6.0 from the viewpoint of ensuring foamability of the resin component. It is more preferable that Mn is 300 × 10 ^{3 to} 400 × 10 ³ and Mw / Mn is 3.0 to 6.0. In the present invention, Mn and Mw mean a number average molecular weight and a weight average molecular weight measured by GPC (gel permeation chromatography), respectively.

  The polypropylene resin of the present invention preferably has a melting point of 125 to 145 ° C, more preferably 140 to 145 ° C, from the viewpoint of ensuring the heat resistance of the resin component.

  Furthermore, unless the polypropylene resin of the present invention and the resin components other than the polypropylene resin described below affect the desired physical properties, vinyl group, carbonyl group, aromatic group, ester group, ether group, It may contain other functional groups such as aldehyde group, amino group, nitrile group and nitro group, may be cross-linked by a cross-linking agent having two or more vinyl groups, etc. More than one species may be used in combination.

From the same viewpoint, the polypropylene resin of the present invention, resin components other than the polypropylene resin described below, and the like may contain other monomer components.
In particular,
1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1- Α-olefinic monomers such as hexene, 1-octene and 1-decene;
Cyclic olefinic monomers such as cyclopentene, norbornene and tetracyclo [6,2,11,8,13,6] -4-dodecene;
Diene monomers such as 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene and 7-methyl-1,6-octadiene;
Vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, maleic anhydride, vinyl such as styrene, methylstyrene, vinyltoluene and divinylbenzene Based monomers. Moreover, these can also be used 1 type, or 2 or more types.

  On the other hand, as carbon black, known carbon black can be used. Specific examples include carbon such as furnace black, channel black, thermal black, acetylene black, graphite, and carbon fiber. Further, furnace black is preferable because a foamed molded article having a more excellent appearance can be obtained.

  In the present invention, since carbon black can be uniformly dispersed in a polypropylene resin, the carbon black preferably has an average particle size of 5 to 100 nm, more preferably 15 to 60 nm, and more preferably 15 to 35 nm. Have. In the present invention, the average particle diameter is an average value of particle diameters measured and calculated by electron micrographs of small spherical components (having a contour due to microcrystals that cannot be separated) constituting an aggregate of carbon black. Is meant.

  Carbon black is contained in 100 parts by mass of polypropylene resin particles in a proportion of 2 to 10 parts by mass, preferably 3 to 8 parts by mass, more preferably 3 to 6 parts by mass. If the amount of carbon black is less than 2 parts by mass, the carbon black may be insufficient and a beautiful foamed molded product may not be obtained. On the other hand, when the carbon black is contained in an amount of more than 10 parts by mass, the carbon component is excessively contained in the resin component, so that it may not be possible to obtain a high-magnification foam molded article.

Furthermore, in a transmission electron micrograph obtained by photographing a 10 μm × 10 μm portion of the polypropylene resin particle surface at a magnification of 2000, the average area of the carbon black is 1.0 × 10 ^{4 to} 9.9 × 10 ⁴ nm ² , The dispersion structure is preferably 4.0 × 10 ^{4 to} 8.9 × 10 ⁴ nm ² . When the average area is larger than 9.9 × 10 ⁴ nm ² , a large amount of coarse carbon black is present in the resin component, which may adversely affect the appearance and retardability. On the other hand, when the average area is smaller than 1.0 × 10 ⁴ nm ² , a large amount of minute carbon black is present in the resin component, which may cause a decrease in the retardability of the foamed molded product.

  On the other hand, the polypropylene resin particles of the present invention preferably have a dispersion structure of 70 to 150, more preferably 80 to 140, in the transmission electron micrograph. When the polypropylene resin particles have a dispersion structure of 70 to 150, this indicates that carbon black is more uniformly dispersed in the resin component. Therefore, in this case, it is possible to provide a seed-polymerized polypropylene-based resin particle that has a higher magnification, is black, has an excellent appearance, and can obtain a foamed molded article having high retardability.

  The polypropylene resin particles of the present invention preferably have a dispersion structure with an average particle diameter of 110 to 350 nm, more preferably an average particle diameter of 150 to 300 nm in the transmission electron micrograph. Also in this case, it is possible to provide a seed-polymerized polypropylene resin particle that has a higher magnification, is black, has an excellent appearance, and can obtain a foamed molded product having a high retardance. In the present invention, the average particle diameter of the dispersion structure means an average value of the particle diameters obtained by measuring the dispersion structure made of carbon black by measuring the distance between two points using image processing software.

  Moreover, as long as a desired physical property can be obtained, the polypropylene resin particles, the foamed molded article and the like may contain other resin components. Examples of other resin components include known thermoplastic resins and thermosetting resins. Specifically, poly (meth) acrylic resins, polyphenylene ether resins, polycarbonate resins, and polylactic acid resins can be used. Examples thereof include polyester-based resins. In addition, (meth) acryl means acryl or methacryl.

  Furthermore, as long as a desired foamed molded product can be obtained, the polypropylene resin particles, the foamed molded product, and the like may contain other additives. Specific examples include additives such as flame retardants, flame retardant aids, colorants, coating agents, light stabilizers, UV absorbers, pigments, dyes, heat stabilizers, nucleating agents, lubricants and antistatic agents. be able to.

  The polypropylene resin particles are preferably spherical to substantially spherical (egg-shaped) from the viewpoint of ensuring fluidity, and preferably 0.5 to 1.4 mm, more preferably 0.5 to 1.18 mm. Even more preferably, it has an average particle size of 0.5 to 1.0 mm.

(Method for producing polypropylene resin particles for seed polymerization (melt kneading step))
In the present invention, as long as polypropylene resin particles having desired physical properties can be obtained, any known production method and production equipment can be used. For example, the polypropylene resin particles of the present invention can be produced by first melt-kneading a polypropylene resin and carbon black using an extruder, then extruding, granulating by underwater cutting, strand cutting, etc. it can. Moreover, the temperature, time, pressure, etc. at the time of the melt-kneading step are appropriately set according to the raw materials used and the production equipment.

In the present invention, the melt kneading temperature in the extruder at the time of melt kneading is preferably 230 to 280 ° C., more preferably 230 to 270 ° C. at which the polypropylene resin is sufficiently softened. Moreover, since carbon black can be uniformly dispersed in a polypropylene resin under suitable shear conditions, the extrusion hole is preferably 3 to 10 kg / mm ² · hr, more preferably 4 to 8 kg / mm ² · hr. Extrusion can be performed at an extrusion rate per unit.

In the present invention, the melt-kneading temperature means the temperature of the melt-kneaded material inside the extruder measured by a thermocouple thermometer at the center temperature of the melt-kneaded material flow path near the extruder head. Moreover, an extrusion hole means the hole for discharging the resin component with which the extruder front end was equipped. Further, the extrusion speed means a value obtained by dividing the amount (kg) of the extrudate discharged per one extrusion hole by the area (mm ² ) of the extrusion hole and time (hour).

  On the other hand, as long as carbon black can be uniformly dispersed, carbon black may be added alone to the polypropylene resin during the melt-kneading step, or a resin composition containing carbon black, so-called master batch, may be added. Also good. In the present invention, since a large amount of carbon black can be more uniformly and easily dispersed in the polypropylene resin, it is preferable to use a resin composition containing carbon black.

  It does not specifically limit as a resin component contained in a resin composition, A well-known thermoplastic resin, a thermosetting resin, etc. can be used. In the present invention, from the viewpoint of compatibility with the polypropylene resin, it is preferable to use a polypropylene resin as the resin component contained in the resin composition.

  Further, since the resin composition can easily disperse a larger amount of carbon black in the resin component, the carbon black is preferably 40 to 80 parts by mass, more preferably 50 to 100 parts by mass of the resin composition. It is included at a ratio of ˜80 parts by mass. For this reason, the polypropylene resin particle for seed polymerization which can obtain the foaming molding which has a high multiple and was excellent in the external appearance can be manufactured still more easily.

  The shape of the polypropylene resin particles obtained by the production method of the present invention is, for example, a true sphere, an oval sphere (egg), a columnar shape, a prismatic shape, a pellet shape, or a granular shape. In the present invention, seed particles made of polypropylene resin are also referred to as micropellets. Further, if necessary, an air conditioner such as talc can be added to the micropellet.

(Composite resin particles)
In the present invention, the composite resin particle means a resin particle containing a plurality of resin components. Specifically, the composite resin particle means a resin particle containing at least a polypropylene resin and another resin as a resin component.

  The composite resin particles of the present invention can be obtained by seed polymerizing a monomer component with polypropylene resin particles. As the resin obtained from the monomer component, any resin can be used as long as a foamed molded article having a high magnification and excellent appearance can be obtained. Specific examples include polymer components such as polystyrene resins, poly (meth) acrylic ester resins, and aromatic resins. In the present invention, a polystyrene polymer is preferable because high foamability can be expected.

  In the present invention, the polystyrene resin means a styrene homopolymer or a copolymer of a styrene monomer as a main component and another monomer copolymerizable with the styrene monomer. The styrene monomer means a styrene monomer or a mixture of a styrene monomer as a main component and another monomer copolymerizable with the styrene monomer. Here, the styrene monomer as a main component means that the styrene monomer occupies 70 parts by mass or more with respect to 100 parts by mass of all monomers.

  Other monomer components such as α-methylstyrene, p-methylstyrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, alkyl acrylate ester, alkyl methacrylate ester, divinylbenzene and polyethylene glycol dimethacrylate A vinyl-type monomer can be mentioned. In the present invention, alkyl preferably means a hydrocarbon chain having 1 to 30 carbon atoms. A styrene homopolymer capable of stably pre-foaming the expandable composite resin particles is preferable.

  In the present invention, since the excellent rigidity (impact resistance) of the polypropylene resin and the excellent foamability of the polystyrene resin can be introduced into the foamed molded article, the polystyrene resin is added to 100 parts by mass of the polypropylene resin. On the other hand, it is preferably used in an amount of 100 to 400 parts by mass, more preferably 150 to 233 parts by mass. When the polystyrene resin is less than 100 parts by mass, it may be impossible to obtain a foamed molded article having a sufficient multiple. On the other hand, when the amount of the polystyrene-based resin is more than 400 parts by mass, a foamed molded article having sufficient impact resistance may not be obtained.

  In addition, as a combination of the polypropylene resin and the polystyrene resin contained in the foamed molded article of the present invention, a higher multiple foamed molded article can be obtained, so a combination of a propylene homopolymer and a styrene homopolymer Is preferred.

  The composite resin particles of the present invention preferably contain a flame retardant and a flame retardant aid from the viewpoint of imparting flame retardancy to the foamed molded article. However, as long as desired physical properties can be obtained, the composite resin particles do not need to contain a flame retardant aid, and the foamed molded product derived from the composite resin particles may not contain a flame retardant aid.

  In the present invention, known flame retardants can be used, such as tris (2,3-dibromopropyl) isocyanurate, tetrabromocyclooctane, hexabromocyclododecane, decabromodiphenyl ether, tribromophenyl allyl ether, tetrabromo Bromine such as bisphenol A diallyl ether, tetrabromobisphenol A dipropyl ether, tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol A di (hydroxyethyl) ether and tetrabromobisphenol A bis (2,3-dibromopropyl ether) -Based flame retardants. Moreover, as long as the desired physical properties are not affected, other flame retardants such as a chlorine-based flame retardant and a bromine-chlorine-based flame retardant may be included.

  A flame retardant may use only 1 type and may use it in combination of multiple types. In the present invention, it is preferable to use tris (2,3-dibromopropyl) isocyanurate as a main component because desired flame retardancy can be easily obtained. In addition, in this invention, a main component means 80 mass parts or more with respect to 100 mass parts of flame retardant whole quantity, More preferably, it means 90 mass parts or more. The same applies to the flame retardant aid.

  The flame retardant of the present invention is contained in an amount of preferably 1.5 to 5.0 parts by mass, more preferably 2.0 to 4.0 parts by mass with respect to 100 parts by mass of the composite resin particles. When content of a flame retardant is less than 1.5 mass parts, the flame retardance of a foaming molding may fall. On the other hand, when the content of the flame retardant is more than 5.0 parts by mass, an amount more than necessary for imparting flame retardancy is included, and the production cost of the foamed molded product may increase.

  In the present invention, known flame retardant aids can be used, such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, cumene. Hydroperoxide etc. can be mentioned. Only one type of flame retardant aid may be used, or a plurality of types may be used in combination. In the present invention, since desired flame retardancy can be easily obtained, it is preferable to use 2,3-dimethyl-2,3-diphenylbutane as a main component.

  The flame retardant aid of the present invention is preferably contained in a proportion of 0.3 to 2.0 parts by mass, more preferably 0.3 to 1.0 parts by mass with respect to 100 parts by mass of the composite resin particles. Also in this case, if the content of the flame retardant aid is less than 0.3 parts by mass, the flame retardancy of the foamed molded product may be lowered. On the other hand, when the content of the flame retardant auxiliary is more than 2.0 parts by mass, an amount more than necessary for imparting flame retardancy is included, and the production cost of the foamed molded product may increase.

  On the other hand, the composite resin particles are also preferably spherical to substantially spherical (egg-like) from the viewpoint of ensuring fluidity, and preferably 0.5 to 2.0 mm, more preferably 1.0 to 1.5 mm on average. It has a particle size.

(Production method of composite resin particles (seed polymerization step))
The composite resin particles of the present invention can be obtained by seed polymerization. In the present invention, seed polymerization means a polymerization method in which a plurality of resin components are combined by impregnating and absorbing propylene resin particles (seed particles) with a monomer component and then polymerizing the monomer component. . In the present invention, a known seed polymerization method can be used as long as a foamed molded article having desired physical properties can be obtained. Hereinafter, although an example is given and this invention is demonstrated, this invention is not limited by these.

  In the present invention, composite resin particles can be obtained by dispersing the micropellets in an aqueous medium in a polymerization vessel and polymerizing the micropellets while impregnating the monomer components. Examples of the aqueous medium include water, a mixed medium of water and a water-soluble solvent (for example, alcohol), and water is preferable from the environmental viewpoint.

  The polypropylene resin may be impregnated with the monomer component while polymerizing the monomer component, or may be performed before the polymerization is started. In the present invention, since the process time can be further shortened, it is preferable to carry out the impregnation while polymerizing. In this case, it is preferable to add the monomer component continuously or intermittently to the aqueous medium in the polymerization vessel.

  An oil-soluble radical polymerization initiator can be used for the polymerization of the monomer component. As the radical polymerization initiator, a radical polymerization initiator widely used for the polymerization of monomer components can be used. For example, benzoyl peroxide, lauroyl peroxide, t-butyl peroxy octoate, t-hexyl peroxy octoate, t-butyl peroxy benzoate, t-amyl peroxy benzoate, t-butyl peroxybivalate, t- Butyl peroxyisopropyl carbonate, t-hexyl peroxyisopropyl carbonate, t-butylperoxy-3,3,5-trimethylcyclohexanoate, di-t-butylperoxyhexahydroterephthalate, 2,2-di- Mention may be made of organic peroxide polymerization initiators such as t-butylperoxybutane, di-t-hexyl peroxide and dicumyl peroxide. The polymerization initiator is usually preferably added at a ratio of 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the monomer component. Further, other polymerization initiators may be included as long as the desired physical properties are not affected. Furthermore, a polymerization initiator may use only 1 type and may use it in combination of multiple types.

Moreover, since seed polymerization can be performed more stably, it is also preferable to add a dispersant to the aqueous medium. Examples of such a dispersant include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylate, polyvinyl pyrrolidone, carboxymethyl cellulose, and methyl cellulose;
Examples thereof include inorganic dispersants such as magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium phosphate, magnesium carbonate and magnesium oxide.

Further, from the same viewpoint, anionic surfactants such as sodium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, alkylnaphthalenesulfonate and alkylphosphate ester salts;
Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine and glycerin fatty acid ester;
Amphoteric surfactants such as lauryldimethylamine oxide; and cationic surfactants such as aliphatic quaternary ammonium salts can also be used.

  The shape and structure of the polymerization vessel are not particularly limited as long as they are conventionally used for suspension polymerization and seed polymerization. Further, the shape of the stirring blade is not particularly limited, and specifically, a paddle blade such as a V-shaped paddle blade, a fiddler blade, an inclined paddle blade, a flat paddle blade, a pull margin blade, a turbine blade, a fan turbine blade, etc. Mention may be made of propeller blades such as turbine blades and marine propeller blades. Of these stirring blades, paddle blades are preferred. The stirring blade may be a single-stage blade or a multi-stage blade. A baffle may be provided in the polymerization container.

  Moreover, the temperature, time, pressure, etc. at the time of the seed process step are also appropriately set according to the raw materials used and the production equipment. Furthermore, in the present invention, after the polymerization is completed, in order to obtain expandable composite resin particles, the suspension containing the composite resin particles may be used as it is, and the composite resin particles recovered from the suspension are used. Also good.

(Process for producing expandable composite resin particles and expandable composite resin particles)
The expandable composite resin particles of the present invention can be obtained by impregnating the composite resin particles with a foaming agent.

The production method of the expandable composite resin particles is not particularly limited, and any known method can be used.
For example, a rotary mixer such as a V-type, C-type, or DC-type, in which composite resin particles are put into a sealed pressure-resistant container and flowed, and then a foaming agent is introduced to impregnate the composite resin particles with the foaming agent. Examples thereof include a method, and a method in which composite resin particles are suspended in an aqueous medium in a sealed pressure-resistant vessel equipped with a stirrer, then a foaming agent is introduced, and the composite resin particles are impregnated with the foaming agent.

  The impregnation with the foaming agent is preferably performed at 50 to 80 ° C. for 1.0 to 4.0 hours. Further, the impregnation may be performed under pressure as long as a desired foamed molded article can be obtained.

  In the present invention, conventionally used blowing agents can be used as the blowing agent. Examples thereof include blowing agents such as saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane and hexane, and inert gases such as carbon dioxide and nitrogen.

  In the present invention, from the viewpoint of imparting high foamability to the foamable composite resin particles, a physical foaming agent is preferred, saturated aliphatic hydrocarbons are more preferred, and normal butane, isobutane, normal pentane and isopentane are particularly preferred. . A foaming agent may be used alone or two or more kinds may be used in combination as long as the foam molding process and desired physical properties are not affected.

  Moreover, since uniform impregnation property and foamability can be expected, a foaming agent may be used together with the impregnation aid. Specifically, examples of the impregnation aid include plasticizers such as toluene, xylene, cyclohexane, ethyl acetate, diisobutyl adipate, diacetylated monolaurate and coconut oil.

  Furthermore, since the foamable composite resin particles can be foamed to a desired high bulk multiple, the foaming agent is preferably 8 to 13 parts by weight, more preferably 9 to 100 parts by weight with respect to 100 parts by weight of the foamable composite resin particles. It is included at a ratio of 11 parts by mass.

  On the other hand, the expandable composite resin particles of the present invention are preferably spherical to substantially spherical (egg-like) from the viewpoint of ensuring fluidity. Similarly, the expandable composite resin particles of the present invention preferably have an average particle diameter of 0.5 to 2.0 mm, more preferably 1.0 to 1.5 mm.

(Pre-expanded particles and method for producing pre-expanded particles)
In the present invention, the pre-expanded particles mean resin particles obtained by heating and foaming expandable composite resin particles to a predetermined bulk factor.

  The pre-expanded particles of the present invention can be produced using a known foam molding method. For example, a foamed molded product can be obtained by charging foamable composite resin particles into a known prefoaming machine and heating to a predetermined bulk factor (prefoaming step). Steam is preferably used as the heating medium for heating. Moreover, the temperature, time, pressure, etc. at the time of preliminary foaming are appropriately set according to the raw materials used and the production equipment.

  On the other hand, if necessary, an antistatic agent such as polyoxyethylene alkylphenol ether and stearic acid monoglyceride may be added to the foamable composite resin particles during preliminary foaming.

  Moreover, since the pre-expanded particles of the present invention are obtained starting from the polypropylene resin particles as described above, the pre-expanded particles of the present invention are preferably 35 to 50 times, more preferably 35 to 45 times the bulk factor. Can have.

  On the other hand, the pre-expanded particles are also preferably spherical to substantially spherical (egg-like) from the viewpoint of ensuring fluidity, and preferably 1.3 to 6.2 mm, more preferably 2.7 to 4.6 mm on average. It has a particle size.

(Foamed molded product)
In the present invention, the foam molded article means a resin molded article obtained by foaming pre-expanded particles into a predetermined shape.

  The foamed molded product of the present invention can be produced using a known molding method. As an example of the molding method, a pre-foamed particle is filled in a mold of a known foam molding machine, heated again, and then pre-foamed particles are thermally fused to obtain a foam-molded product ( Foam molding process). Steam is preferably used as the heating medium for heating. Moreover, the temperature, time, pressure, and the like during the foam molding process are appropriately set according to the raw materials used and the production equipment.

  In addition, since the foam molded article of the present invention is obtained by starting from the polypropylene resin particles as described above, the foam molded article of the present invention preferably has a multiple of 35 to 50 times, more preferably 35 to 45 times. Can have. This has shown that the foaming molding of this invention has a high multiple.

  Furthermore, in the present invention, in order to form seed particles in which the carbon black dispersion structure is uniformly dispersed, the foam molded article of the present invention is preferably 28 or less when the foam molded article is measured using a color difference meter. More preferably, it can have an L value (lightness) of 27 or less. On the other hand, the standard deviation (σ) of the L value is preferably 1.0 or less, more preferably 0.8 or less. This indicates that the foamed molded article of the present invention is black and excellent in appearance without causing variations in appearance such as uneven color.

  In addition, since the foamed molded article of the present invention contains a flame retardant and a flame retardant aid at a suitable ratio, in the delayed flame retardancy test based on FMVSS302, the foamed molded article having a multiple of 40 times is preferably 80 mm / min or less, More preferably, it can have a burning rate of 70 mm / min or less. This indicates that the foamed molded article of the present invention has high retardability.

  Therefore, the foamed molded product of the present invention is a foamed molded product having no multiple color unevenness due to the uneven distribution of carbon black, having a high multiple, excellent appearance in black, and high retardance. For this reason, the foamed molded product of the present invention can be widely used as a cushioning material for packaging, a building member, etc., and particularly used as an indoor structural member in the automotive field such as a raising material, a tibia pad and a tool box. You can also.

  Hereinafter, although an example is given and explained further, the present invention is not limited by these examples. Various measurement methods and production conditions described in the examples will be described below.

<Photograph of carbon black through transmission electron microscope>
The measurement sample (polypropylene resin particles) is embedded and fixed using an epoxy resin, then dyed with ruthenium tetroxide (RuO ₄ ), and the measurement sample is thinned using an ultramicrotome. To do. Thereafter, using a transmission electron microscope (H-7600, manufactured by Hitachi, Ltd.), the structure of the surface layer of 10 μm × 10 μm on the surface of the polypropylene resin particles is observed. In order to distinguish between the polypropylene resin portion and the carbon black portion in the obtained photograph, the image is softened using image processing software (product name “Nano Hunter NS2K-Pro” manufactured by Nanosystem).

The area occupied by carbon black is measured by automatically calculating the area of the carbon black portion relative to the total area using the binarized diagram. Further, the number of dispersed structures (aggregates) of carbon is measured by measuring the number of dispersed structures (aggregates) having an average area of 500 nm ² or more using a binarized diagram. The obtained area is divided by the number of carbon dispersion structures (aggregates), and the average value of the obtained areas is defined as the average area.

The particle size of the carbon black dispersion structure present in the binarized figure is measured by measuring the distance between two points using the image processing software. Ten points are measured for each of the particle sizes, and the average value of each is taken as the average particle size of the dispersion structure. In addition, in the transmission electron microscope photographing of carbon black, a disperse structure that is cut off from the image and a disperse structure that has an average area smaller than 500 nm ² are excluded.

<Average molecular weight of resin component (Mn and Mw)>
The GPC apparatus used for the measurement was HLC-8121GPC / HT manufactured by Tosoh Corporation, TSKgel GMHhr-H (20) HT manufactured by Tosoh Corporation was used as the column, the column temperature was set to 140 ° C., and 1,2 as the eluent. , 4-trichlorobenzene is used. The measurement sample is adjusted to a concentration of 1.0 mg / mL, and the amount injected into the GPC device is 0.3 mL. The calibration curve for each molecular weight is calibrated using a polyethylene sample with a known molecular weight. The number average molecular weight (Mn) and the weight average molecular weight (Mw) are determined as linear polyethylene equivalent values.

<Melting point of polypropylene resin>
Measured by the method described in JIS K7122: 1987 “Method of measuring the transition heat of plastic”. That is, using a differential scanning calorimeter DSC220 type (manufactured by Seiko Denshi Kogyo Co., Ltd.), 7 mg of a sample was filled in a measurement container, and a nitrogen gas flow rate of 30 mL / min. The temperature rise, fall, and temperature rise are repeated at the speed of raising and lowering the temperature, and the melting peak temperature of the DSC curve at the second temperature rise is defined as the melting point. Further, when there are two or more melting peaks, the lower peak temperature is taken as the melting point.

<Average particle size of seed particles>
The average particle size of the sample is calculated by taking the average particle size of these particles. That is, the average particle diameter of the present invention means a volume average particle diameter. In addition, the average particle diameter of a sample can be measured using the measuring apparatus marketed as the product name "Coulter Multisizer II" from Beckman Coulter, Inc., for example.

<Foaming agent content of expandable composite resin particles>
5 to 20 mg of the foamable composite resin particles are accurately weighed and used as a measurement sample. This measurement sample is set in a pyrolysis furnace (manufactured by Shimadzu Corporation: PYR-1A) maintained at 180 to 200 ° C., and the measurement sample is sealed and heated for 120 seconds to release the foaming agent component. A chart of the blowing agent component is obtained under the following conditions using a gas chromatograph (manufactured by Shimadzu Corporation: GC-14B, detector: FID) for the released blowing agent component. Based on the calibration curve of the foaming agent component measured in advance, the foaming agent content (parts by mass) in the foamable composite resin particles is calculated from the obtained chart.

Gas chromatograph measurement conditions Column: “Shimalite 60/80 NAW” (φ3 mm × 3 m) manufactured by Shinwa Kako Co., Ltd. Column temperature: 70 ° C.
Detector temperature: 110 ° C
Inlet temperature: 110 ° C
Carrier gas: Nitrogen carrier gas Flow rate: 60 mL / min

<Bulk multiple of pre-expanded particles>
The weight (a) of about 5 g of pre-expanded particles is weighed at the second decimal place. Next, weighed pre-expanded particles in a 500 cm ³ graduated cylinder with a minimum memory unit of 5 cm ³ , and a round resin plate slightly smaller than the caliber of the graduated cylinder, about 1.5 cm wide at the center, The volume (b) of the pre-expanded particles was read by applying a pressing tool in which a rod having a length of about 30 cm was fixed upright, and the bulk density of the pre-expanded particles (g / cm ³ ) The bulk multiple is the reciprocal of the bulk density, that is, the formula (b) / (a).

<Evaluation of slow flammability of foam molded article>
The evaluation of slow-flammability (burning rate) of the foamed molded product is measured by a method in accordance with US automobile safety standard FMVSS 302. The test piece has a multiple of 40 times, 350 mm × 100 mm × 12 mm (thickness), and skins are present on at least two sides of 350 mm × 100 mm.

In the present invention,
(1) In the case of a foamed molded article having a multiple of 40 times, when the combustion rate is 80 mm / min or less.
(2) In the case of a foamed molded product having a multiple of 40 times, when the combustion rate is faster than 80 mm / min.
Is determined.

<Multiple of foam molding>
The weight (a) and volume (b) of a test piece (example 75 × 300 × 50 mm) cut out from a foamed molded product (after being molded and dried at 40 ° C. for 20 hours or more) are each three or more significant figures. Then, the density (g / cm ³ ) of the foamed molded product is obtained by the formula (a) / (b). The multiple is the reciprocal of the density, that is, the formula (b) / (a).

<Appearance of foamed molded product (evaluation of blackness of foamed molded product)>
As shown in FIG. 4, the molded product (400 × 300 × 50 mm) is made uniform by 100 mm as shown in the figure below, and the sample surface (Φ50 mm area) is measured with a color difference meter (KONICA MINOLTA model number: CR410) at each measurement point. Then, the average value was converted into a numerical value by the CIE color difference formula. The blackness was determined based on the L value. The standard deviation (σ) was determined for the degree of variation in blackness. If the standard deviation was 1.0 or less, it was judged that the variation was very small.

In the present invention,
(1) When L value is 28 or less and σ is 1.0 or less: Pass (O)
(2) When the L value is higher than 28 or σ is higher than 1.0: reject (x)
Is determined.

Example 1
Polypropylene resin particles containing 5% by mass of furnace black (carbon black) were prepared as follows. 26.7 kg of polypropylene resin (manufactured by Prime Polymer Co., Ltd., product name “F-744NP”, melting point: 140 ° C., propylene unit: 96 mass%), master batch containing 45 mass% of furnace black (manufactured by Dainichi Seika Kogyo Co., Ltd., 3. Product name “PP-RM10H381” and resin component LLDPE (linear low density polyethylene resin)) of 3.34 kg are mixed, and the mixture is supplied to an extruder and an extrusion speed per extrusion hole: 4. Melting and kneading at 7 kg / mm ² · hr, melt kneading temperature: 230 ° C., and granulating pellets by cutting in water to obtain carbon black-containing polypropylene resin particles.
The carbon black-containing polypropylene resin particles at this time were adjusted to 80 mg per 100 particles and an average particle diameter of about 1 mm. FIG. 1 is a transmission electron micrograph of a 10 μm × 10 μm portion of the seed polymerization polypropylene resin particle surface taken at a magnification of 2000 times.

Next, 16 kg of the carbon black-containing polypropylene resin particles are placed in a 100 L autoclave with a stirrer, 40 kg of pure water as an aqueous medium, 0.4 kg of magnesium pyrophosphate as a dispersant, and dodecylbenzenesulfone as a surfactant used in combination with a dispersant. 10 g of acid soda was added, stirred and suspended in an aqueous medium, held for 10 minutes, then heated to 60 ° C. to obtain an aqueous suspension.
To this suspension, 6.8 kg of a styrene monomer in which 14 g of dicumyl peroxide as a polymerization initiator was dissolved was dropped in 30 minutes. After dropping, the mixture was held for 30 minutes, and the styrene monomer was absorbed into the carbon black-containing polypropylene resin particles.
The temperature of the reaction system is raised to 135 ° C., which is 5 ° C. lower than the melting point of the carbon black-containing polypropylene resin particles, and maintained for 2 hours, and the styrene monomer is polymerized in the carbon black-containing polypropylene resin particles (first polymerization). Stage).

The reaction liquid in the first polymerization stage was set to 125 ° C., which is 15 ° C. lower than the melting point of the carbon black-containing polypropylene resin particles, and 60 g of sodium dodecylbenzenesulfonate as a surfactant was added to this suspension, and then polymerization was started. As the agent, 17.2 kg of styrene monomer in which 72 g of dicumyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd.) was dissolved was dropped over 4.25 hours, and polymerization was performed while absorbing the carbon black-containing polypropylene resin particles. And after completion | finish of this dripping, after hold | maintaining at 125 degreeC for 1 hour, it heated up at 140 degreeC and hold | maintained for 3 hours, and superposition | polymerization was completed (2nd polymerization stage), and the composite resin particle was obtained.
Thereafter, the temperature of the reaction system was set to 60 ° C., and 1.2 kg of tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant, and 2 as a flame retardant aid. , 3-dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo Co., Ltd.) 0.2 kg, and after the addition, the temperature of the reaction system was raised to 140 ° C. and stirring was continued for 3 hours. Composite resin particles were obtained.

Next, it was cooled to room temperature, and the flame retardant-containing composite resin particles were taken out from the 100 L autoclave. After taking out, 15 kg of the flame retardant-containing composite resin particles were put into a pressure-resistant rotary mixer having an internal volume of 50 L, rotated, and 2.4 kg of butane as a blowing agent was injected into the pressure-resistant rotary mixer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours.
Then, it cooled to normal temperature and took out from the 50L pressure | voltage resistant rotary mixer, and obtained the expandable composite resin particle.
Next, the obtained expandable composite resin particles were pre-expanded with 0.04 MPa vapor to obtain pre-expanded particles having a bulk multiple of 42 times.

Next, the obtained pre-expanded particles were allowed to stand at room temperature and normal pressure for 24 hours, and then filled into a cavity of a mold having a size of 400 mm × 300 mm × 50 mm, and with 0.25 MPa water vapor It was introduced for 40 seconds and heated, and cooled until the maximum surface pressure of the foamed molded product was reduced to a gauge pressure of 0.001 MPa to obtain a foamed molded product with a multiple of 40 times.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for all 10 samples.

Example 2
From Example 1, the melt kneading temperature was changed from 230 ° C. to 270 ° C., and the extrusion rate per extrusion hole was changed from 4.7 kg / mm ² · hr to 5.4 kg / mm ² · hr.
Otherwise, the same procedure as in Example 1 was performed.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for all 10 samples.

Example 3
From Example 1, the melt kneading temperature was changed from 230 ° C to 250 ° C.
Otherwise, the same procedure as in Example 1 was performed.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for all 10 samples.

Example 4
From Example 1, the melt kneading temperature was changed from 230 ° C. to 250 ° C., and the extrusion speed per extrusion hole was changed from 4.7 kg / mm ² · hr to 7.8 kg / mm ² · hr.
Otherwise, the same procedure as in Example 1 was performed.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for all 10 samples.

Example 5
Polypropylene resin particles containing 3% by mass of furnace black (carbon black) were prepared as follows. 28.0 kg of polypropylene resin (manufactured by Prime Polymer Co., Ltd., product name “F-744NP”, melting point: 140 ° C., propylene unit: 96 mass%), masterbatch containing 45 mass% of furnace black (manufactured by Dainichi Seika Kogyo Co., Ltd., Product name “PP-RM10H381”, resin component LLDPE) 2.0 kg is mixed, and this mixture is supplied to an extruder and the extrusion speed per extrusion hole: 4.7 kg / mm ² · hour, melt kneading temperature : Melted and kneaded at 230 ° C. and granulated into pellets by cutting in water to obtain carbon black-containing polypropylene resin particles.
Otherwise, the same procedure as in Example 1 was performed.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for all 10 samples.

Comparative Example 1
From Example 1, the melt kneading temperature was changed from 235 ° C. to 220 ° C.
Otherwise, the same procedure as in Example 1 was performed.
FIG. 2 is a transmission electron micrograph of a 10 × 10 μm portion of the seed polymerization polypropylene resin particle surface photographed at a magnification of 2000 times.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for 8 samples. The other samples had an average burning rate of 150 mm / min.

Comparative Example 2
From Example 1, the melt kneading temperature was changed from 235 ° C. to 290 ° C., and the extrusion rate per extrusion hole was changed from 4.7 kg / mm ² · hr to 7.8 kg / mm ² · hr.
Otherwise, the same procedure as in Example 1 was performed.
FIG. 3 is a transmission electron micrograph of a 10 μm × 10 μm portion of the surface of the seed polymerization polypropylene resin particles taken at a magnification of 2000 times.
The slow-flammability evaluation (burning rate) of the foamed molded product was 0 mm / min for the two samples. The average burning rate of the other samples was 143 mm / min.

  From Tables 1 and 2, the multiple, the blackness evaluation, and the slow-flammability evaluation for the examples showed good results, but the comparative examples sometimes did not show good results.

  Therefore, the foamed molded product of the present invention is a foamed molded product having a high multiple, black color, excellent appearance, and high retardability. Therefore, the foamed molded product of the present invention can be widely used as a cushioning material for packaging, a building member, an automobile member, etc., and particularly as an indoor structural member in the automotive field such as a raising material, a tibia pad and a tool box. It can also be used.

Claims (11)

Carbon resin is included in a proportion of 2 to 10 parts by mass in 100 parts by mass of resin particles containing a polypropylene resin as a resin component,
In the transmission electron micrograph obtained by photographing a 10 μm × 10 μm portion of the resin particle surface at a magnification of 2000, a dispersion structure of the carbon black having an average area of 1.0 × 10 ^{4 to} 9.9 × 10 ⁴ nm ² is obtained. Polypropylene resin particles for seed polymerization having
The seed-polymerized polypropylene resin particles have the dispersed structure with an average particle diameter of 110 to 350 nm in the transmission electron micrograph .   The polypropylene resin particles for seed polymerization according to claim 1, wherein the polypropylene resin particles for seed polymerization have 70 to 150 dispersed structures in the transmission electron micrograph. The polypropylene resin particles for seed polymerization according to claim 1 or 2 , wherein the polypropylene resin particles for seed polymerization have an average particle diameter of 0.5 to 1.4 mm. It is a manufacturing method of the polypropylene resin particle for seed polymerization as described in any one of Claims 1-3 , Comprising: The resin composition containing the said carbon black and the said polypropylene resin are supplied to an extruder, and it melt-kneads A method for producing seed polymerization polypropylene resin particles. Composite resin particles obtained by seed polymerizing polypropylene polymer particles for seed polymerization according to any one of claims 1 to 3 with a styrene monomer. The composite resin particle according to claim 5 , wherein the composite resin particle contains 100 to 400 parts by mass of a polystyrene resin with respect to 100 parts by mass of the polypropylene resin. The composite resin particle is a ratio of 1.5 to 5.0 parts by mass of the flame retardant and a ratio of 0.3 to 2.0 parts by mass of the flame retardant aid with respect to 100 parts by mass of the composite resin particles. The composite resin particle according to claim 5 or 6 , comprising Expandable composite resin particles obtained from the composite resin particles according to any one of claims 5 to 7 . Pre-expanded particles obtained from the expandable composite resin particles according to claim 8 . A foam-molded product obtained from the pre-expanded particles according to claim 9 . The foamed molded product according to claim 10 , wherein the foamed molded product has a multiple of 35 to 50 times.