JP2008075076A - Styrene-modified polypropylene resin particles and expandable resin particles thereof, methods for producing them, pre-expanded particles, and expanded molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a styrene-modified polypropylene resin foam-molded article having excellent flame retardancy, while retaining rigidity, impact resistance and chemical resistance. <P>SOLUTION: The polystyrene-modified polypropylene resin particle contains 100-400 pts.mass polystyrenic resin, on the basis of 100 pts.mass polypropylene resin. The resin particle is characterized by containing 1.5-8.0 pts.mass of a flame retardant mainly constituted of tris(2,3-dibromopropyl)isocyanurate, based on 100 pts.mass of the resin particle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to styrene-modified polypropylene-based resin particles, expandable resin particles thereof, a production method thereof, pre-expanded particles, and an expanded molded body. More specifically, the present invention relates to a styrene-modified polypropylene resin particle having excellent retardability and its expandable resin particles, a production method thereof, pre-expanded particles and a foamed molded product. The foamed molded article of the present invention is useful as a core material for automobile bumpers, an energy absorbing material at the time of a vehicle collision such as a cushioning material mounted inside the automobile, and a structural member in the automobile interior.

  In general, a foamed molded article of polyolefin resin is used as a packaging material because it has high elasticity and is excellent in oil resistance and impact resistance. However, it has the disadvantages of low rigidity and low compressive strength. On the other hand, a polystyrene resin foam is excellent in rigidity but has a disadvantage of being brittle.

  As a method for improving such a defect, for example, in Patent Documents 1 to 4, a polyethylene resin is impregnated with a styrene monomer to perform polymerization, and then subjected to a foaming agent impregnation and foaming step, followed by styrene modification. A method for obtaining polyethylene resin expanded particles is disclosed.

  Patent Documents 5 and 6 disclose a method of obtaining a styrene-modified polypropylene resin particle or pre-expanded particle by impregnating a polypropylene resin with a styrene monomer and performing polymerization.

  In addition, the foamed molded product may be desired to be colored black depending on the application. In particular, it is strongly desired that a member in an automobile interior is colored in black. Carbon is known as a black colorant (see, for example, Patent Documents 7 and 8).

Furthermore, when used as a member in an automobile compartment, slow-flammability is indispensable, but this foamed molded article has a drawback that it easily burns. Many attempts have been made so far to solve this problem (see, for example, Patent Documents 9 to 12).
Japanese Patent Publication No.51-46138 Japanese Patent Publication No.52-10150 Japanese Patent Publication No.58-53003 JP-A-62-59642 JP 61-9432 A JP-A-9-194623 Japanese Patent Publication No. 5-54854 JP 2006-111862 A JP-A-6-57027 Japanese Patent Laid-Open No. 7-179646 Japanese Patent Laid-Open No. 7-179647 JP 2004-211042 A

  However, even when the conventional techniques described in Patent Documents 1 to 12, particularly the means disclosed in Patent Documents 9 to 12, are attempted, the slow-flammability of the carbon-containing foamed molded article is not sufficient, and the delay of automobile interior members and the like is slow. Further improvements are desired for use in applications that require flammability.

  An object of the present invention is to obtain a styrene-modified polypropylene-based resin foam molded article having excellent retardance while maintaining good rigidity, impact resistance and chemical resistance.

  In order to achieve the above object, the present invention provides polystyrene-modified polypropylene resin particles containing 100 to 400 parts by mass of a polystyrene resin with respect to 100 parts by mass of a polypropylene resin. A styrene-modified polypropylene resin particle characterized in that a flame retardant containing (2,3-dibromopropyl) isocyanurate as a main component is contained in an amount of 1.5 to 8.0 parts by mass with respect to 100 parts by mass of the resin particles. I will provide a.

  In the styrene-modified polypropylene resin particles of the present invention, the resin particles preferably contain 0.5 to 8.0% by mass of carbon particles.

  In the styrene-modified polypropylene resin particles of the present invention, 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, cumene hydroper It is preferable that 0.1-3.0 mass parts of 1 type, or 2 or more types of flame retardant adjuvants selected from the group of oxide are contained with respect to 100 mass parts of resin particles.

  The present invention also provides styrene-modified polypropylene-based expandable resin particles, wherein the above-described styrene-modified polypropylene-based resin particles according to the present invention contain a foaming agent.

  The present invention also provides styrene-modified polypropylene resin pre-expanded particles obtained by pre-expanding the styrene-modified polypropylene-based expandable resin particles according to the present invention.

  The present invention also provides a styrene-modified polypropylene resin foam molded article obtained by in-mold foam molding of the above-described styrene-modified polypropylene resin foam particles according to the present invention.

In the styrene-modified polypropylene resin foam molded article of the present invention, the shrinkage rate under the conditions of 80 ° C. in accordance with JIS K 6767 is that the burning rate in accordance with US automobile safety standard FMVSS 302 is 80 mm / min or less. It is 1.0% or less, and it is preferable that it is the range of 20 to 40 times the bulk ratio and 0.025 to 0.05 g / cm ³ of the bulk density.

  In the present invention, polypropylene resin particles are dispersed in an aqueous suspension containing a dispersant, and then 100 to 400 parts by mass of styrene is added to 100 parts by mass of the polypropylene resin particles in the obtained dispersion. A step of supplying a monomer and a polymerization initiator and subjecting the styrene monomer to suspension polymerization, and the resin particles during or after the polymerization are hardly composed mainly of tris (2,3-dibromopropyl) isocyanurate There is provided a method for producing styrene-modified polypropylene resin particles comprising a step of impregnating with a flame retardant.

  In the method for producing styrene-modified polypropylene resin particles of the present invention, it is preferable that carbon particles are contained in an amount of 0.5 to 8.0% by mass in the resin particles.

  In the method for producing styrene-modified polypropylene resin particles of the present invention, the resin particles include 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, It is preferable that 0.1-3.0 mass parts of 1 type, or 2 or more types of flame retardant adjuvants selected from the group of cumene hydroperoxide are contained with respect to 100 mass parts of resin particles.

  Further, the present invention provides a styrene-modified polypropylene-based expandable resin particle by impregnating a foaming agent in any step of the production method according to the present invention described above or impregnating the obtained styrene-modified polypropylene-based resin particle. A method for producing styrene-modified polypropylene-based expandable resin particles is provided.

  According to the present invention, a styrene-modified polypropylene-based resin particle capable of giving a foamed molded article having excellent rigidity, impact resistance and chemical resistance and excellent in slow flame retardancy, the foamable resin particle and the preliminary Expanded particles can be provided.

The inventors of the present invention have made additional trials for retarding flame retarding means (flame retardant species, flame retardant amount, flame retardant impregnation conditions, etc.) disclosed in Patent Documents 9 to 12 in the same manner except that carbon is present. Further, it was found that when carbon is present in the styrene-modified polyolefin resin foamed molded article, the slow flame retardancy is extremely lowered. For example, when a horizontal combustion test in accordance with US automobile safety standard FMVSS 302 is performed on a foamed molded article having a bulk multiple of 30 times (density 0.033 g / cm ³ ), it cannot be reduced to 80 mm / min or less. It was.

  In addition, it has been found that even if the amount of the flame retardant generally used in expanded polystyrene is increased, the retarding flame effect reaches its peak.

  Therefore, as a result of intensive studies on the types of flame retardants and polyolefin resins, the present inventors have adopted polypropylene resins as polyolefin resins, and tris (2,3-dibromopropyl) isocyanurate as a flame retardant. Surprisingly, it was found that by using a flame retardant, which is a main component, sufficient retarded flame retardancy can be imparted even in the case of a styrene-modified polyolefin resin foam molded article in which carbon is present, and the present invention has been completed. .

  In the present invention, “sufficiently slow flammability” means that the foaming rate is 20 to 30 times the bulk molding rate in the US automobile safety standard FMVSS 302 horizontal burning test and the burning rate is 80 mm / min or less.

(Styrene modified polypropylene resin particles)
The styrene modified polypropylene resin particles (hereinafter also referred to as modified resin particles) of the present invention are particles in which a polystyrene resin is contained in a polypropylene resin.

(Carbon-containing styrene modified polypropylene resin particles)
The carbon-containing styrene-modified polypropylene resin particles (hereinafter also referred to as carbon-containing modified resin particles) of the present invention are particles in which a polystyrene resin is contained in a carbon-containing polypropylene resin.

  Examples of the carbon in the carbon-containing polypropylene resin include furnace black, ketjen black, channel black, thermal black, acetylene black, graphite, and carbon fiber. The carbon (raw material carbon) before being contained in the polypropylene resin is preferably in the form of particles, and the particle size of the raw material carbon is usually preferably 5 to 100 nm, and more preferably 10 to 80 nm. In addition, the particle diameter of raw material carbon means an average particle diameter, and an average particle diameter is an arithmetic average by an electron microscope.

  Carbon is preferably contained in the carbon-containing modified resin particles in an amount of 0.5 to 8.0% by mass. If the blending amount of carbon in the carbon-containing modified resin particles is less than 0.5% by mass, the resulting foamed molded product may not exhibit a sufficient black color, which is not preferable. Moreover, when it exceeds 8.0 mass%, since not only the slow-flammability of the foaming molding obtained from a carbon containing modified resin particle falls, but mechanical strength may fall, it is unpreferable.

  Although it does not specifically limit as a polypropylene resin in this invention, The melting | fusing point of a polypropylene resin is 120-140 degreeC. When the melting point of the polypropylene resin is lower than 120 ° C., the heat resistance is poor, and the heat resistance of the foamed molded article obtained from the modified resin particles or the carbon-containing modified resin particles is lowered. In addition, if the melting point is higher than 140 ° C., the production conditions for modified resin particles or carbon-containing modified resin particles that require a high polymerization temperature become severe, which requires modification of conventional equipment, which is disadvantageous in terms of cost. It is. Moreover, the thing whose melt flow rate of a polypropylene resin is 0.1-10 g / 10min is preferable. When the melt flow rate of the polypropylene resin is lower than 0.1 g / 10 min, it becomes difficult to granulate the polypropylene resin into a desired particle diameter. On the other hand, if the melt flow rate is higher than 10 g / 10 min, it becomes difficult to granulate the polypropylene-based resin, and it becomes difficult to pre-form the modified resin particles containing the foaming agent. In a preferred embodiment of the present invention, as the polypropylene resin, a propylene-ethylene copolymer having a melting point in the range of 120 to 140 ° C. and a melt flow rate in the range of 0.1 to 10 g / 10 minutes is used. Used. This propylene-ethylene copolymer is mainly composed of a copolymer of ethylene and propylene, but may contain ethylene or another monomer that can be copolymerized with propylene in the molecule. good. Examples of such a monomer include one or more selected from α-olefins, cyclic olefins, and diene monomers. The ethylene-propylene copolymer has a melting point of 120 to 140 ° C. and a melt flow rate of 0.1 to 10 g / 10 minutes, and may be any of random, block, and terpolymerization. . If there are a plurality of melting points, the lowest temperature is taken as the melting point.

  In addition to carbon particles, other additives may be blended in the polypropylene resin particles of the present invention. Specific examples include nucleating agents such as zinc stearate, aluminum stearate, and ethylene bis-stearic acid amide, antioxidants, ultraviolet absorbers, flame retardants, and the like that are commonly used for polypropylene resins. Among these, the flame retardant is a flame retardant mainly composed of tris (2,3-dibromopropyl) isocyanurate.

  Examples of the polystyrene resin include resins derived from styrene monomers such as styrene and side chain substituted styrene (substituents are lower alkyl, halogen atoms (particularly chlorine atoms) and the like). In the case of a resin derived from a mixed monomer of styrene and side chain substituted styrene, the amount of the resin derived from styrene is preferably large. Further, it may be a resin derived from a mixture of styrene and other copolymerizable small amounts of other non-styrene monomers. Examples of other monomers include acrylonitrile, methacrylic acid alkyl ester (alkyl partial carbon number of about 1 to 8), maleic acid mono to dialkyl (alkyl partial carbon number of about 1 to 4), divinylbenzene, ethylene glycol mono to diacrylic acid. Or methacrylic acid ester, maleic anhydride, N-phenylmaleide and the like. The content of the other monomer is preferably 30 parts by mass or less with respect to 100 parts by mass of the styrene monomer. Of these, resins derived only from styrene are preferred.

  The polystyrene resin is contained in an amount of 100 to 400 parts by mass with respect to 100 parts by mass of the polypropylene resin particles or the carbon-containing polypropylene resin particles. When the amount of the polystyrene resin is less than 100 parts by mass, the modified resin particles or the styrene-modified polypropylene-based expandable resin particles obtained by impregnating the carbon-containing modified resin particles with a foaming agent or the carbon-containing styrene modified The foamability and moldability of polypropylene-based expandable resin particles (hereinafter also referred to as expandable resin particles) are deteriorated. On the other hand, when the amount exceeds 400 parts by mass, a styrene-modified polypropylene resin foam molded article obtained from modified resin particles or carbon-containing modified resin particles, or a carbon-containing styrene modified polypropylene resin foam molded article (hereinafter referred to as foam). The strength of the molded body) also deteriorates. The amount of the polystyrene resin is more preferably in the range of 120 to 250 parts by mass with respect to 100 parts by mass of the polypropylene resin particles or the carbon-containing polypropylene resin particles.

  The flame retardant used in the present invention is a flame retardant mainly composed of tris (2,3-dibromopropyl) isocyanurate.

  The amount of the flame retardant used is 1.5 to 8.0 parts by mass, preferably 2 to 5 parts by mass with respect to 100 parts by mass of the modified resin particles or the carbon-containing modified resin particles. When the amount of the flame retardant is less than 1.5 parts by mass, the slow flame retardancy of the foamed molded article produced using the modified resin particles or the carbon-containing modified resin particles is not preferable. In addition, if the amount of the flame retardant is more than 8.0 parts by mass, not only an effect commensurate with a large amount of use cannot be obtained, but also the foamed molded product produced from the modified resin particles or the carbon-containing resin particles becomes brittle. It is not preferable.

  The modified resin particles or the carbon-containing modified resin particles of the present invention include 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, diethylene, together with the flame retardant. It is preferable that 0.1 to 3.0 parts by mass of one or more flame retardant aids selected from the group of mill peroxide and cumene hydroperoxide are added to 100 parts by mass of the resin particles.

  By adding the flame retardant aid in the range of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the resin particles, the flame retardance of the obtained resin can be further increased. When the addition amount of the flame retardant aid is less than the above range, the effect of adding the flame retardant aid is not sufficiently obtained, and when the addition amount of the flame retardant aid exceeds the above range, the addition effect of the flame retardant aid However, this is not preferable because it increases the cost and causes an increase in cost.

  There is no particular limitation on the size of the modified resin particles or the carbon-containing modified resin particles of the present invention, but the L / D value is 0 when the particle length is L and the average particle diameter is D. A cylindrical shape in the range of 6 to 1.6, or a substantially spherical or spherical shape is preferable. Moreover, what is a range whose average particle diameter is 0.3-3.0 mm is preferable. For those with a large flatness such that the L / D value is less than 0.6 or exceeds 1.6, pre-expanded particles derived from modified resin particles or carbon-containing modified resin particles are filled in a mold. When producing a foamed molded article, the filling property of the pre-expanded particles into the mold may be unfavorable. Also, if the average particle diameter is less than 0.3 mm, the particle diameter of the pre-expanded particles derived from the modified resin particles or the carbon-containing modified resin particles is also small, so the retention of the foaming agent is lowered and the density is reduced. Is not preferable because it may become difficult. When the average particle diameter exceeds 3.0 mm, the particle diameter of the expandable resin particles obtained from the modified resin particles or the carbon-containing modified resin particles is increased, and not only the filling property is deteriorated, but also It is not preferable because thinning becomes difficult. In addition, the measuring method of the average particle diameter of a modified resin particle or a carbon containing modified resin particle is explained in full detail in the Example mentioned later.

(Method for producing modified resin particles or carbon-containing modified resin particles)
To produce modified resin particles or carbon-containing modified resin particles by the production method of the present invention, first, polypropylene resin particles or carbon-containing polypropylene resin particles are prepared, and an aqueous suspension containing a dispersant Inside, polypropylene resin particles or carbon-containing polypropylene resin particles are dispersed.

  There is no particular restriction on the size of the polypropylene resin particles used in this production method. However, considering that the particle diameter of the modified resin particles or carbon-containing modified resin particles to be produced is limited by this, it is usually 10 A size of about ~ 500 mg / 100 is preferable. In addition, it is preferable that the particle length is L and the average diameter is D, and the L / D value is in the range of 0.6 to 1.6. Moreover, what is a range whose average particle diameter is 0.2-1.5 mm is preferable. For those with a large flatness such that the L / D value is less than 0.6 or exceeds 1.6, pre-expanded particles derived from modified resin particles or carbon-containing modified resin particles are filled in a mold. When obtaining a foam-molded article, it is not preferable because the filling ability of the mold becomes worse. In addition, when the average particle size is less than 0.2 mm, the particle size of the expandable resin particles derived from the modified resin particles or the carbon-containing modified resin particles is also small, so that the retention of the foaming agent is lowered and the density is low. This is not preferred because it may be difficult to achieve. When the average particle diameter exceeds 1.5 mm, the particle diameter of the modified resin particles or the expandable resin particles derived from the carbon-containing modified resin particles is increased, and not only the filling property is deteriorated but also the foamed molded product is thinned. Is also not preferable because it becomes difficult. In addition, the measuring method of the average particle diameter of a polypropylene resin particle is explained in full detail in the Example mentioned later.

  Polypropylene resin particles are, for example, blended with polypropylene resin with a predetermined amount of carbon particles and, if necessary, additives as appropriate (other additives described in the column of resin particles), and sufficiently in an extruder. It is obtained by heating and mixing and granulating pellets by strand cutting, underwater cutting, hot cutting or the like so as to obtain a desired particle size. As the carbon, it is preferable to use particulate carbon having good dispersibility in a polypropylene resin.

  It is preferable that 1-40 mass% is contained in a polypropylene resin, and, as for carbon, it is more preferable that 3-20 mass% is contained. This amount is determined corresponding to an amount in the range of 0.5 to 8.0% by mass of carbon content with respect to the resin particles finally produced.

  In the production method of the present invention, the polymerization reaction of the styrenic monomer is carried out in an aqueous medium. A dispersant (dispersion stabilizer) is added to the aqueous medium. Examples of suitable dispersants in the production method of the present invention include aqueous polymer dispersants such as polyvinyl alcohol and polyvinyl pyrrolidone, and poorly water-soluble inorganic dispersants such as tricalcium phosphate, magnesium pyrophosphate, and calcium carbonate. Here, when the inorganic dispersant is added, it is desirable to use a surfactant such as sodium dodecylbenzenesulfonate. The amount of the dispersant used is preferably 0.1% by mass or more based on the aqueous medium. However, use of a larger amount than 4% by mass is not inconvenient, but since an effect commensurate with the use of a large amount cannot be expected, it is not preferable because it is disadvantageous economically.

  Examples of the aqueous medium include water, a mixed medium of water and an organic solvent soluble in water (for example, lower alcohol), and the like.

  Next, 100 to 400 parts by mass of a styrene monomer and a polymerization initiator are supplied to 100 parts by mass of the polypropylene resin particles, and the styrene monomer is subjected to suspension polymerization. By this suspension polymerization, modified resin particles or carbon-containing modified resin particles are obtained.

  The addition amount of the styrene monomer is in the range of 100 to 400 parts by mass, more preferably 120 to 250 parts by mass with respect to 100 parts by mass of the polypropylene resin particles or the carbon-containing polypropylene resin particles. When the addition amount of the styrene monomer is less than 100 parts by mass, the foamability and moldability of the modified resin particles or the expandable resin particles derived from the carbon-containing modified resin particles are not preferable. On the other hand, if it exceeds 400 parts by mass, the strength of the foamed molded product derived from the modified resin particles or the carbon-containing modified resin particles is unfavorable.

  Styrene monomers include plasticizers such as toluene, xylene, cyclohexane, ethyl acetate, dioctyl phthalate, and tetrachloroethylene, small amounts of oil-soluble polymerization inhibitors, water-soluble polymerization inhibitors, bubble regulators, mercaptans, α -A chain transfer agent such as a methylstyrene monomer, a flame retardant, a flame retardant aid and the like may be added as necessary.

  Although it does not specifically limit as a polymerization initiator, What generate | occur | produces a tertiary alkoxy radical can be used. For example, t-butylperoxy-2-ethylhexanoate, t-amylperoxyl-2-ethylhexanoate, t-butylperoxyisobutyrate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate, 2,2-bis (t-butylperoxy) butane, t-butylperoxybenzoate, 2,2-di-t-butylper And oxybutane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, and the like. These polymerization initiators can be used alone or in admixture of two or more.

  The polymerization initiator may be added to the dispersion before addition of the styrenic monomer or may be dissolved in the styrene monomer and added to the dispersion, but after the temperature has been raised to a predetermined polymerization temperature. It is desirable to drop the styrene monomer in which the polymerization initiator is dissolved over a predetermined time.

  The used amount (total amount) of the polymerization initiator is preferably about 0.1 to 5% by mass, more preferably 0.3 to 3% by mass with respect to 100% by mass of the styrene monomer. When the amount of the polymerization initiator used is less than 0.1% by mass, the polymerization is difficult to complete and the amount of unreacted styrenic monomer may increase, which is not preferable. Further, it is not preferable to complete the polymerization because the polymerization time needs to be greatly extended, which is economically disadvantageous. On the other hand, if it is more than 5% by mass, the foamed molded article derived from the modified resin particles or the carbon-containing modified resin particles becomes unfavorable. It is also economically disadvantageous.

  The styrene monomer and the polymerization initiator are absorbed in the polypropylene resin particles by being added to the dispersion. Absorption of the styrene monomer and the polymerization initiator into the polypropylene resin particles may be performed before the polymerization or may be performed simultaneously with the polymerization.

  The polymerization temperature is preferably in the range of 70 to 140 ° C, more preferably in the range of 90 to 130 ° C. It is preferable to raise the temperature to the polymerization temperature by gradually raising the temperature constant or stepwise. In this case, the temperature rising rate is preferably 0.1 to 2 ° C./min.

  Next, the polypropylene resin particles in suspension polymerization, the carbon-containing polypropylene resin particles, the modified resin particles after the polymerization, or the carbon-containing modified resin particles are added to the modified resin particles or the carbon-containing modified resin particles. Modification with slow flame retardancy by impregnating a flame retardant mainly composed of tris (2,3-dibromopropyl) isocyanurate so as to be contained in an amount of 1.5 to 8.0 parts by mass with respect to 100 parts by mass Resin particles or carbon-containing modified resin particles can be produced.

  The flame retardant may be dissolved in the styrene monomer and added to the dispersion, or after the polymerization of the styrene monomer is completed, the flame retardant may be added, or added to the dispersion before or after polymerization. Also good. When the flame retardant causes a chain transfer reaction to the styrenic monomer and is inconvenient, it is preferably added to an aqueous medium containing a dispersant after polymerization of the styrenic monomer.

  When the flame retardant is added after polymerization, the impregnation temperature of the flame retardant to the modified resin particles or the carbon-containing modified resin particles is preferably 60 to 150 ° C, more preferably in the range of 80 to 140 ° C. is there.

  In addition, in the manufacturing method of this invention, you may bridge | crosslink a polypropylene resin as needed. Typical examples of the crosslinking agent include 2,2-di-t-butylperoxybutane, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl- An organic peroxide such as 2,5-di-t-butylperoxyhexane may be mentioned. These crosslinking agents can be used alone or in admixture of two or more. Usually, it is preferable that the usage-amount of a crosslinking agent is 0.05-1.5 mass parts with respect to 100 mass parts of polypropylene resin particles or carbon-containing polypropylene resin particles.

  This crosslinking reaction is preferably performed at 120 to 160 ° C, more preferably 130 to 150 ° C. In addition, the timing of crosslinking may be the case where the polypropylene resin particles or the carbon-containing polypropylene resin particles are crosslinked in advance before the styrene monomer is polymerized, or may be crosslinked after the polymerization is completed. The crosslinking agent may be added to the polymerization system alone, but in consideration of safety, it may be added to the polymerization system after being dissolved in a solvent, a plasticizer or a styrene monomer in advance or dispersed in water. preferable. Moreover, you may add a bubble regulator, a flame retardant, a flame retardant adjuvant, etc. in a reaction system in the case of the said crosslinking reaction as needed.

(Expandable resin particles)
The expandable resin particles of the present invention are obtained by adding a foaming agent to the above-described modified resin particles or carbon-containing modified resin particles.

  The foaming agent is not particularly limited, and any known foaming agent can be used. Particularly, those having a boiling point lower than the softening point of polystyrene resin, for example, volatile organic foaming agents such as hexane, normal pentane, isopentane, neopentane, normal butane, isobutane, propane, trichloromonofluoromethane, dichlorodifluoromethane, etc. Single or mixtures can be used. The impregnation amount of the foaming agent is preferably 5 to 25 parts by mass with respect to 100 parts by mass of the modified resin particles or the carbon-containing modified resin particles.

(Method for producing expandable resin particles)
The method for producing the expandable resin particles is the same as the method for producing the modified resin particles or the carbon-containing modified resin particles described above, except that the impregnation step of the foaming agent is further applied.

  The impregnation method of the foaming agent is not particularly limited, and any known method can be used. When the modified resin particles or the carbon-containing modified resin particles are made into expandable resin particles, regardless of before or after the polymerization of the styrene monomer to be added, a foaming agent is added according to a conventional technique, Alternatively, the carbon-containing modified resin particles can be impregnated with a volatile organic foaming agent.

  The foaming agent which can be used can use the foaming agent described in the column of the said foamable resin particle. When the foaming agent is a volatile organic foaming agent, the impregnation temperature is preferably 50 to 140 ° C.

  Moreover, you may add a foaming auxiliary agent with the impregnation of a foaming agent. Examples of the foaming aid include solvents such as toluene, xylene, ethylbenzene, cyclohexane, and plasticizers (high-boiling solvents) such as diisobutyl adipate, diacetylated monolaurate, and palm oil. The addition amount of the foaming aid is preferably 0.2 to 2.5 parts by mass with respect to 100 parts by mass of the modified resin particles or the carbon-containing modified resin particles.

  Furthermore, if necessary, a surface treatment agent (for example, a binding inhibitor, a fusion accelerator, an antistatic agent, a spreading agent, etc.) may be added to the impregnation system when impregnating the foaming agent.

  The anti-bonding agent plays a role of preventing bonding of the expandable particles due to heating during the production of pre-expanded particles described below. Examples of the binding inhibitor include talc, calcium carbonate, zinc stearate, aluminum hydroxide, ethylene bis stearamide, tricalcium phosphate, dimethylsiloxane and the like.

  The fusion accelerator plays a role of promoting fusion of the pre-expanded particles at the time of in-mold molding. Examples of the fusion accelerator include stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride, and stearic acid sorbitan ester.

  Examples of the antistatic agent include polyoxyethylene alkylphenol ether and sorbitan stearate.

  Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.

  The addition amount (total amount) of these surface treatment agents is preferably 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the modified resin particles or carbon-containing modified resin particles.

  When the foaming agent is added during the polymerization step, it is desirable to add and impregnate after 70% by mass of the styrenic monomer has been polymerized. Further, it may be added when the polymerization progresses 99% or more, and the impregnation with the foaming agent may be continued. Furthermore, the obtained modified resin particles or carbon-containing modified resin particles may be newly dispersed in an aqueous medium, and a foaming agent may be added thereto and impregnated.

  Expandable resin particles are produced from the modified resin particles or the carbon-containing modified resin particles by the above method.

(Pre-expanded particles)
The pre-expanded particles of the present invention can be obtained by bringing water vapor into contact with the expandable resin particles and expanding the particles to a predetermined bulk factor (bulk density). The pre-foaming heating conditions and the apparatus used for the pre-foaming can be the same as in the case of production of conventional polystyrene resin pre-foamed particles. For example, it can be obtained by heating the expandable resin particles in an atmosphere having a water vapor pressure of about 0.05 to 0.4 MPa in a preliminary foaming apparatus. The heating time is generally about 20 to 90 seconds. A preferable bulk expansion ratio of the pre-expanded particles is about 20 to 40 times in consideration of use for a structural member in an automobile interior. The pre-expanded particles are preferably stored and aged usually for about 24 hours.

The pre-expanded particles usually have a bulk density of 0.0166 to 0.2 g / cm ³ (bulk multiple of 5 to 60 times). Preferably, the bulk density is 0.02 to 0.1 g / cm ³ (bulk multiple of 10 to 50 times). More preferably, the bulk density is 0.025 to 0.05 g / cm ³ (bulk multiple 20 to 40 times). If the bulk density is less than 0.0166 g / cm ³ , the strength of the foamed molded product obtained by foaming the pre-foamed particles is unfavorable. On the other hand, if it is larger than 0.2 g / cm ³ , the mass of the foamed molded product obtained by foaming the pre-expanded particles is not preferable.

(Foamed molded product)
In the foamed molded product of the present invention, the pre-expanded particles are filled into a mold, pressurized water vapor is introduced into the mold, the foamed particles are heated, foamed and fused together, and then the mold is molded. It can be obtained after cooling. The molding die, molding conditions, etc. used here are not particularly limited, and known molding dies and molding conditions can be adopted. For example, it can be performed by introducing water vapor having a vapor pressure of about 0.05 to 0.5 MPa into the mold.

  The foamed molded article of the present invention is useful as a core material for automobile bumpers, an energy absorbing material at the time of a vehicle collision such as a buffering agent mounted inside the automobile, and a structural member in the automobile interior. In addition to the automobile field, it can also be used in applications such as housing materials, transport containers for electronic parts, and various industrial materials.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
First, measurement methods and evaluation criteria for various tests performed in this example will be described.

<Average particle diameter of polypropylene resin particles, carbon-containing polypropylene resin particles, modified resin particles, and carbon-containing modified resin particles>
About 50 g of a sample was sieved using a low-tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.) 3.35 mm, 2.80 mm, 2.36 mm, 2.00 mm, 1.70 mm, 1.40 mm, 1.18 mm , 1.00mm, 0.85mm, 0.71mm, 0.60mm, 0.50mm, 0.425mm, 0.355mm, 0.300mm, 0.250mm, 0.212mm, 0.180mm JIS standard sieve 5 Classification is performed for a minute, and the sample mass on the sieve mesh is measured. Based on the cumulative mass distribution curve obtained from the result, the particle diameter (median diameter) at which the cumulative mass is 50% is determined as the average particle diameter.

<Melting point of polypropylene resin>
Measured by the method described in JIS K7122: 1987 “Method for 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, cooling, and temperature rise were repeated according to the temperature rise and cooling rate, and the melting peak temperature of the DSC curve at the second temperature rise was taken as the melting point. When there were two or more melting peaks, the lower peak temperature was taken as the melting point.
<Melt flow rate of polypropylene resin>
JIS K 7210: 1999 “Plastics—Test Methods for Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) of Thermoplastic Plastics” Method B was used for measurement. The measuring method is as follows: 3-8 g of a sample is filled in a cylinder of a measuring device (semi-auto melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd.)), and the material is compressed using a filling rod at a test temperature of 230 ° C. (PP). At 190 ° C (PE), the test load is based on the specified load (21.18N (PP, PE)) Preheating time is 4 minutes.

<Bulk density and bulk multiple of pre-expanded particles>
The mass (a) of about 5 g of pre-expanded particles is weighed in 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 this is a round resin plate slightly smaller than the diameter of the graduated cylinder, about 1.5 cm wide at the center, The volume (b) of the pre-expanded particles is read by applying a pressing tool in which a rod-shaped resin plate having a length of about 30 cm is fixed upright, and the bulk density (g) of the pre-expanded particles is calculated according to the formula (a) / (b). / Cm ³ ). The bulk multiple was the inverse of the bulk density, that is, the formula (b) / (a).

<Fusion rate of foam molding>
A 300 mm long and 5 mm deep score line is placed on the surface of a rectangular parallelepiped foam molded body having a length of 400 mm × width of 300 mm × height of 50 mm with a cutter, and the foam molded body is divided into two along the score line. . Then, on the divided surface of the foam molded body, the number of expanded particles (a) broken in the expanded particles and the number of expanded particles (b) broken at the interface between the expanded particles were measured, and based on the following formula: The fusing rate was calculated.
Fusing rate (%) = 100 × (a) / [(a) + (b)]

<Burning rate of foamed molded product>
Combustion rate was measured according to FMVSS 302 (American Automobile Safety Standard). The test piece had a bulk multiple of 30 times, 350 mm × 100 mm × 12 mm (thickness), and at least 350 mm × 100 mm of two surfaces had skins.
A foamed molded article having a bulk ratio of 30 times can be favorably used as a structural member in an automobile compartment if the burning rate is 80 mm / min or less. Therefore, the following standards were established.
Evaluation criteria: When the burning rate is 80 mm / min or less, it is good, and when the burning rate is higher than 80 mm / min, it is bad and x.

<Heat dimensional change rate of foamed molded product>
Measured by the method B described in JIS K 6767: 1999K “Foamed Plastics-Polyethylene Test Method”. In addition, the test piece has a bulk multiple of 30 times, 150 mm × 150 mm × 30 mm (thickness), and three straight lines are written in the center part in parallel to each other in the vertical and horizontal directions at intervals of 50 mm. After leaving in a hot air circulation dryer for 168 hours, the product was taken out and left in a standard state for 1 hour, and the vertical and horizontal line dimensions were measured by the following formulas.
S = (L1-L0) / L0 × 100
In the formula, S represents a heating dimensional change rate (%), L1 represents an average dimension (mm) after heating, and L0 represents an initial average dimension (mm).
If the ratio of heating dimensional change is 1.0% or less in a foamed molded article having a bulk multiple of 30 times, it can be used favorably as a structural member in an automobile interior. Therefore, the following standards were established.
Evaluation criteria: When the heating dimensional change rate is 1.0% or less, it is good, and when the heating dimensional change rate is larger than 1.0%, it is poor and is marked as x.

<Evaluation of chemical resistance of foamed molded products>
The test piece has a bulk multiple of 30 times, 100 mm × 100 mm × 50 mm (thickness), and is allowed to stand for 24 hours under conditions of 23 ° C. and 50% humidity. The test piece is cut out from the foam molded body so that the entire upper and lower surfaces of the test piece are formed from the surface of the foam molded body.
Next, 1 g of gasoline as a chemical is uniformly applied and left for 60 minutes under the conditions of 23 ° C. and humidity 50%. Thereafter, the chemical is wiped off from the upper surface of the test piece, and the upper surface of the test piece is visually observed. If there is no change on the surface of the test piece, it can be used favorably as a structural member for automobiles. Therefore, the following standards were established.
Evaluation criteria: A case where there was no change on the surface of the test piece was evaluated as ◯, a case where the surface of the test piece was softened was evaluated as Δ, and a case where the surface of the test piece was depressed or contracted was evaluated as x.

[Example 1]
Polypropylene resin (hereinafter referred to as PP) particles were prepared by heating and mixing 20 kg of PP particles (manufactured by Sun Allomer, PC540R) in an extruder and granulating them by strand cutting. The PP particles were adjusted to 80 mg per 100 particles, and the average particle size was about 1 mm.

  12 kg of the PP particles are placed in a 100 L autoclave equipped with a stirrer, 40 kg of pure water, 400 g of magnesium pyrophosphate, and 4 g of sodium dodecylbenzenesulfonate are added as an aqueous medium, and stirred to suspend the PP particles in the aqueous medium for 10 minutes. The temperature was maintained, and then the temperature was raised to 60 ° C.

  Subsequently, 6 kg of styrene monomer in which 12 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

  Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 22 kg of styrene monomer in which 84 g of dicumyl peroxide was dissolved as a polymerization initiator was added for 5 hours 30 minutes. It was dripped over. After the completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.

  Thereafter, the temperature is lowered to 60 ° C. as a flame retardant impregnation step, 800 g of tris (2,3-dibromopropyl) isocyanurate is added as a flame retardant, the temperature is raised to 140 ° C., and stirring is continued at this temperature for 3.5 hours. It was.

  Then, it cooled to normal temperature and took out. After taking out, 2 kg of the styrene-modified polypropylene resin particles and 2 L of water were charged into a 5 L autoclave with a pressure stirrer, and 300 g of butane as a blowing agent was injected into the 5 L autoclave with a pressure stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 3 hours.

  Thereafter, the mixture was cooled to room temperature, taken out, dehydrated and dried, and styrene-modified polypropylene-based expandable resin particles were obtained.

  Thereafter, the styrene-modified polypropylene-based expandable resin particles were pre-expanded to a bulk multiple of 30 times to obtain styrene-modified polypropylene-based resin expanded particles.

  The obtained styrene-modified polypropylene resin expanded particles were left at room temperature for 1 day, then placed in a 400 × 300 × 50 mm size mold, heated by introducing 0.2 MPa of water vapor for 50 seconds, and then The foam molded body was taken out by cooling until the maximum surface pressure of the foam molded body decreased to 0.001 MPa. Under these molding conditions, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foam molded product with a bulk ratio of 30 times is 3.5 mm / min, the heating dimensional change rate at 80 ° C. and 168 hours of the foam molded product with a bulk ratio of 30 times is 0.3%, and the chemical resistance evaluation is ○ Met.

[Example 2]
Using 20 kg of the same PP particles as in Example 1, the PP particles were placed in a 100 L autoclave with a stirrer, and 40 kg of pure water, 400 g of magnesium pyrophosphate, and 4 g of sodium dodecylbenzenesulfonate were added as an aqueous medium, and the mixture was stirred and mixed in an aqueous medium. Suspended for 10 minutes and then heated to 60 ° C.

  Subsequently, 10 kg of styrene monomer in which 20 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

  Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 10 kg of styrene monomer in which 60 g of dicumyl peroxide was dissolved as a polymerization initiator was added for 2 hours and 30 minutes. It was dripped over. After the completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.

  Thereafter, the temperature is lowered to 60 ° C. as a flame retardant impregnation step, 800 g of tris (2,3-dibromopropyl) isocyanurate is added as a flame retardant, the temperature is raised to 140 ° C., and stirring is continued at this temperature for 3.5 hours. It was.

  Subsequent steps were performed in the same manner as in Example 1. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk multiple of 30 times is 63.1 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk multiple of 30 times is 0.5%, and the chemical resistance evaluation is ○ Met.

[Example 3]
As for PP particles containing 6% by mass of furnace black, 18.8 kg of PP particles (manufactured by Sun Allomer Co., Ltd., PC540R) and 1200 g of furnace black (manufactured by Mitsubishi Chemical Co., Ltd., # 650B) are mixed, and this is heated and mixed in an extruder to form a strand. It was made by granulating pellets by cutting. The PP particles containing 6% by mass of furnace black were adjusted to 80 mg per 100 particles, and the average particle size was about 1 mm.

  12 kg of this furnace black 6 mass% containing PP particles are put into a 100-liter autoclave with a stirrer, and 40 kg of pure water, 400 g of magnesium pyrophosphate and 4 g of sodium dodecylbenzenesulfonate are added as an aqueous medium, and the furnace black 6 is stirred into the aqueous medium. The PP particles containing mass% were suspended and held for 10 minutes, and then heated to 60 ° C.

  Subsequently, 6 kg of styrene monomer in which 12 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

  Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 22 kg of styrene monomer in which 84 g of dicumyl peroxide was dissolved as a polymerization initiator was added for 5 hours 30 minutes. It was dripped over. After the completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.

  Thereafter, the temperature is lowered to 60 ° C. as a flame retardant impregnation step, 800 g of tris (2,3-dibromopropyl) isocyanurate is added as a flame retardant, the temperature is raised to 140 ° C., and stirring is continued at this temperature for 3.5 hours. It was.

  Then, it cooled to normal temperature and took out. 2 kg of carbon-containing styrene-modified polypropylene resin particles and 2 L of water after taking out were charged into a 5 L autoclave with a pressure stirrer, and 300 g of butane as a blowing agent was injected into the 5 L autoclave with a pressure stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 3 hours.

  Then, after cooling to room temperature and taking out, dehydrating and drying, carbon-containing styrene-modified polypropylene-based expandable resin particles were obtained.

  Thereafter, the carbon-containing styrene-modified polypropylene-based expandable resin particles were pre-expanded to a bulk multiple of 30 times to obtain carbon-containing styrene-modified polypropylene-based resin expanded particles.

  The obtained carbon-containing styrene-modified polypropylene resin foamed particles are allowed to stand at room temperature for 1 day, and then placed in a 400 × 300 × 50 mm mold, and 0.2 MPa of water vapor is introduced for 50 seconds and heated. Thereafter, the foam molded body was cooled until the maximum surface pressure of the foam molded body decreased to 0.001 MPa, and the foam molded body was taken out. Under these molding conditions, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk multiple of 30 times is 8.1 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk multiple of 30 times is 0.5%, and the chemical resistance evaluation is ○ Met.

[Example 4]
The PP particles containing 3% by mass of furnace black were mixed with 19.4 kg of PP particles (manufactured by Prime Polymer, F-794NV) and 600 g of furnace black (manufactured by Mitsubishi Chemical, # 650B), and this was mixed by heating in an extruder. Then, it was made by granulating pellets by strand cutting. The PP particles containing 3% by mass of furnace black were adjusted to 80 mg per 100 particles, and the average particle size was about 1 mm.

  16 kg of this 3% by mass furnace black PP particle was placed in a 100 L autoclave equipped with a stirrer, and 40 kg of pure water, 400 g of magnesium pyrophosphate, and 4 g of sodium dodecylbenzenesulfonate were added as an aqueous medium, and stirred to add the furnace black 3 to the aqueous medium. The PP particles containing mass% were suspended and held for 10 minutes, and then heated to 60 ° C.

  Subsequently, 8 kg of styrene monomer in which 16 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

  Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 16 kg of styrene monomer in which 72 g of dicumyl peroxide was dissolved as a polymerization initiator was dropped over 4 hours. did. After the completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.

  Subsequent steps were performed in the same manner as in Example 3. As a result, a foamed molded article having good appearance and fusion was obtained.

.
The burning rate of the foamed molded product having a bulk ratio of 30 times is 40.2 mm / min. The heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product having a bulk ratio of 30 times is 0.4%, and the chemical resistance evaluation is ○ Met.

[Example 5]
Furnace black 3 mass% -containing polypropylene resin particles were produced in the same manner as in Example 4 except that PP was changed to PC540R manufactured by Sun Allomer.

  20 kg of PP particles containing 3% by mass of furnace black are placed in a 100 L autoclave with a stirrer, and 40 kg of pure water, 400 g of magnesium pyrophosphate and 4 g of sodium dodecylbenzenesulfonate are added as an aqueous medium, and the mixture is stirred and suspended in the aqueous medium. It was kept for 10 minutes and then heated to 60 ° C.

  Subsequently, 10 kg of styrene monomer in which 20 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

  Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 10 kg of styrene monomer in which 60 g of dicumyl peroxide was dissolved as a polymerization initiator was added for 2 hours and 30 minutes. It was dripped over. After completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.

  Thereafter, the temperature is lowered to 60 ° C. as a flame retardant impregnation step, 1200 g of tris (2,3-dibromopropyl) isocyanurate is added as a flame retardant, the temperature is raised to 140 ° C., and stirring is continued at this temperature for 3.5 hours. It was.

  Subsequent steps were performed in the same manner as in Example 3 to produce a foamed molded article. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foam molded product with a bulk ratio of 30 times is 69.7 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foam molded product with a bulk ratio of 30 times is 0.5%, and the chemical resistance evaluation is ○ Met.

[Example 6]
A foam molded article was produced in the same manner as in Example 4 except that the furnace black of Example 4 was changed to graphite.
PP particles containing 3% by mass of graphite are mixed with 19.4 kg of PP particles (manufactured by Prime Polymer Co., Ltd., F-794NV) and 600 g of graphite (manufactured by Nippon Graphite Industry Co., Ltd., earth graphite powder), and heated with an extruder. It was prepared by mixing and granulating pellets by strand cutting. PP particles containing 3% by mass of graphite were adjusted to 80 mg per 100 particles, and the average particle size was about 1 mm. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk ratio of 30 times is 38.4 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk ratio of 30 times is 0.4%, and the chemical resistance evaluation is ○ Met.

[Example 7]
A foam molded article was produced in the same manner as in Example 3, except that the furnace black content of the PP particles was 10% by mass and that 2000 g of tris (2,3-dibromopropyl) isocyanurate was used as the flame retardant.

  As for PP particles containing 10% by mass of furnace black, 18 kg of PP particles and 2.0 kg of furnace black (Mitsubishi Chemical Corporation, # 650B) are mixed, heated and mixed in an extruder, and granulated into pellets by strand cutting. Produced. The PP particles containing 10% by mass of furnace black were adjusted to 80 mg per 100 particles, and the average particle size was about 1 mm. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk ratio of 30 times is 79.7 mm / min, the heating dimensional change rate of the foamed molded product with a bulk ratio of 30 times at 80 ° C. and 168 hr is 0.8%, and the chemical resistance evaluation is ○ Met.

[Comparative Example 1]
A foamed molded article was produced in the same manner as in Example 1 except that no flame retardant was added. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product having a bulk magnification of 30 times is 135.8 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product having a bulk magnification of 30 times is 0.1%, and the chemical resistance evaluation is ○ Met. Since the tris (2,3-dibromopropyl) isocyanurate, which is a flame retardant, was not added, the burning rate of the foamed molded article having a bulk ratio of 30 times did not become 80 mm / min or less.

[Comparative Example 2]
24 kg of the same PP particles used in Example 1 were placed in a 100 L autoclave with a stirrer, and 40 kg of pure water, 400 g of magnesium pyrophosphate and 4 g of sodium dodecylbenzenesulfonate were added as an aqueous medium, and the mixture was stirred and suspended in the aqueous medium. The mixture was made turbid, held for 10 minutes, and then heated to 60 ° C.

  Subsequently, 12 kg of styrene monomer in which 24 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 4 kg of styrene monomer in which 48 g of dicumyl peroxide was dissolved as a polymerization initiator was dropped over 1 hour. did. After completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.
Subsequent steps were performed in the same manner as in Example 1 to produce a foamed molded article.

  Due to the small amount of polystyrene component in the modified resin particles, the modified foamable resin particles did not foam up to 30 times the bulk.

[Comparative Example 3]
4 kg of the same PP particles used in Example 1 are put into a 100 L autoclave with a stirrer, 40 kg of pure water, 400 g of magnesium pyrophosphate, and 4 g of sodium dodecylbenzenesulfonate are added as an aqueous medium, and the mixture is stirred and suspended in the aqueous medium. The mixture was made turbid, held for 10 minutes, and then heated to 60 ° C.

  Subsequently, 2 kg of styrene monomer in which 4 g of dicumyl peroxide was dissolved in this suspension was dropped for 30 minutes. After dropping, the temperature was maintained for 30 minutes, the temperature was raised to 140 ° C., and stirring was continued at this temperature for 2 hours.

Thereafter, the temperature was lowered to 125 ° C., 160 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and 34 kg of styrene monomer in which 108 g of dicumyl peroxide was dissolved as a polymerization initiator was added for 8 hours 30 minutes. It was dripped over. After completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization.
Subsequent steps were performed in the same manner as in Example 1 to produce a foamed molded article. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product having a bulk ratio of 30 times is 43.0 mm / min, the heating dimensional change rate of the foamed molded product having a bulk ratio of 30 times at 80 ° C. and 168 hours is 1.2%, and the chemical resistance evaluation is × Met. The heating dimensional change rate of the foamed molded article having a bulk multiple of 30 times did not become 1% or less. In the chemical resistance evaluation, the surface of the test piece was slightly depressed.

[Comparative Example 4]
In Example 4, a foamed molded article was produced in the same manner as in Example 4 except that no flame retardant was added. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foam molded product with a bulk ratio of 30 times is 154.5 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foam molded product with a bulk ratio of 30 times is 0.1%, and the chemical resistance evaluation is ○ Met. Since the tris (2,3-dibromopropyl) isocyanurate, which is a flame retardant, was not added, the burning rate of the foamed molded article having a bulk ratio of 30 times did not become 80 mm / min or less.

[Comparative Example 5]
In Example 4, a foamed molded article was produced in the same manner as in Example 4 except that tris (2,3-dibromopropyl) isocyanurate, which is a flame retardant, was changed to tetrabromocyclooctane. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk ratio of 30 times is 77.3 mm / min, the heating dimensional change rate at 80 ° C. and 168 hours of the foamed molded product with a bulk ratio of 30 times is 1.2%, and the chemical resistance evaluation is ○ Met. The heating dimensional change rate of the foamed molded article having a bulk multiple of 30 times did not become 1% or less.

[Comparative Example 6]
Example 4 is the same as Example 4 except that 800 g of tris (2,3-dibromopropyl) isocyanurate as a flame retardant was changed to 2000 g of tetrabromobisphenol-A-bis (2,3-dibromopropyl ether). A foamed molded product was produced in the same manner. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product having a bulk magnification of 30 times is 90.1 mm / min, the heating dimensional change rate of the foamed molded product having a bulk magnification of 30 times at 80 ° C. and 168 hr is 0.5%, and the chemical resistance evaluation is ○ Met. Since the flame retardant is tetrabromobisphenol-A-bis (2,3-dibromopropyl ether), the bulk multiple is 30 times despite using as much as 5% by mass with respect to the carbon-containing modified resin particles. The burning rate of the foamed molded product did not fall below 80 mm / min.

[Comparative Example 7]
A foamed molded article was produced in the same manner as in Comparative Example 3 except that the PP particles in Comparative Example 3 were changed to PP particles containing 10% by mass of furnace black used in Example 7. Since this product has a large amount of polystyrene component, the polystyrene component was present near or on the outermost surface of the polypropylene resin without any polymerization of the styrene monomer inside the polypropylene resin. For this reason, with respect to the appearance, color unevenness occurred and the blackness decreased, resulting in a foamed molded article having a poor appearance.

  The burning rate of the foamed molded product having a bulk multiple of 30 times is 62.7 mm / min, the rate of change in the heating dimension of the foamed molded product having a bulk multiple of 30 times at 80 ° C. and 168 hr is 1.2%, and the chemical resistance evaluation is × Met. The heating dimensional change rate of the foamed molded article having a bulk multiple of 30 times did not become 1% or less. In the chemical resistance evaluation, a slight depression occurred on the test surface.

[Comparative Example 8]
A foam molded article was produced in the same manner as in Comparative Example 2 except that the PP particles in Comparative Example 2 were changed to PP particles containing 3% by mass of furnace black used in Example 5. Since this product has a small amount of polystyrene component in the carbon-containing modified resin particles, the carbon-containing modified foamable resin particles did not foam up to 30 times the bulk.

[Comparative Example 9]
A foamed molded article was produced in the same manner as in Example 4 except that PP particles containing 3% by mass of furnace black in Example 4 were changed to polyethylene resin particles containing 3% by mass of furnace black. As the polyethylene resin particles, linear low density polyethylene (manufactured by Nippon Unicar Co., Ltd., TUF-2032) was used.

  The obtained carbon-containing styrene-modified polyethylene resin foamed particles are allowed to stand at room temperature for 1 day, then placed in a 400 × 300 × 50 mm mold, and 0.1 MPa water vapor is introduced for 50 seconds and heated. Thereafter, the foam molded body was cooled until the maximum surface pressure of the foam molded body decreased to 0.001 MPa, and the foam molded body was taken out. Under these molding conditions, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foam molded product with a bulk ratio of 30 times is 126.1 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foam molded product with a bulk ratio of 30 times is 0.9%, and the chemical resistance evaluation is ○ Met. Since this product uses linear low-density polyethylene, the burning rate of the foamed molded product having a bulk multiple of 30 times did not fall below 80 mm / min.

[Comparative Example 10]
A foamed molded article was produced in the same manner as in Example 4 except that PP particles containing 3% by mass of furnace black in Example 4 were changed to polyethylene resin particles containing 3% by mass of furnace black. As the polyethylene resin particles, ethylene-vinyl acetate copolymer (manufactured by Nippon Polyethylene Co., Ltd., LV-12 1) was used.

  The obtained carbon-containing styrene-modified polyethylene resin expanded particles are allowed to stand at room temperature for 1 day, and then placed in a 400 × 300 × 50 mm mold, and 0.06 MPa water vapor is introduced for 50 seconds and heated. Thereafter, the foam molded body was cooled until the maximum surface pressure of the foam molded body decreased to 0.001 MPa, and the foam molded body was taken out. Under these molding conditions, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk magnification of 30 times is 90.5 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk magnification of 30 times is 1.6%, and the chemical resistance evaluation is ○ Met. Since this product uses an ethylene-vinyl acetate copolymer, the burning rate of the foamed molded product having a bulk multiple of 30 times was slower than that of the linear low density polyethylene of Comparative Example 9, but 80 mm / It was not less than min. Further, the heating dimensional change rate did not become 1% or less.

[Comparative Example 11]
In Comparative Example 9, a foamed molded article was produced in the same manner as Comparative Example 9, except that 800 g of tris (2,3-dibromopropyl) isocyanurate, which is a flame retardant, was changed to 2000 g. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk multiple of 30 times is 119.8 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk multiple of 30 times is 2.4%, and the chemical resistance evaluation is ○ Met. Since this product uses linear low-density polyethylene, a foamed molded product with a bulk multiple of 30 times is used despite the use of a large amount of 5% by mass of a flame retardant for the carbon-containing modified resin particles. The burning rate did not fall below 80 mm / min. Further, the heating dimensional change rate did not become 1% or less.

[Comparative Example 12]
In Comparative Example 10, a foamed molded article was produced in the same manner as Comparative Example 10, except that 800 g of tris (2,3-dibromopropyl) isocyanurate, which is a flame retardant, was changed to 2000 g. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product with a bulk multiple of 30 times is 85.3 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk multiple of 30 times is 3.5%, and the chemical resistance evaluation is ○ Met. Since this product uses an ethylene-vinyl acetate copolymer, the foamed molded product has a bulk multiple of 30 times despite the use of a large amount of 5% by mass of flame retardant for the carbon-containing modified resin particles. The burning rate of was not less than 80 mm / min. Further, the heating dimensional change rate did not become 1% or less.

[Comparative Example 13]
In Comparative Example 9, a foamed molded article was produced in the same manner as Comparative Example 9, except that furnace black was not added to the polyethylene resin. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product having a bulk magnification of 30 times is 95.3 mm / min, the heating dimensional change rate of the foamed molded product having a bulk magnification of 30 times at 80 ° C. and 168 hr is 0.9%, and the chemical resistance evaluation is ○ Met. Since this product uses linear low-density polyethylene, the burning rate of the foamed molded product having a bulk multiple of 30 times did not fall below 80 mm / min.

[Comparative Example 14]
In Comparative Example 10, a foamed molded article was produced in the same manner as Comparative Example 10 except that furnace black was not added to the polyethylene resin. As a result, a foamed molded article having good appearance and fusion was obtained.

  The burning rate of the foamed molded product having a bulk ratio of 30 times is 60.3 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product having a bulk ratio of 30 times is 1.6%, and the chemical resistance evaluation is ○ Met. Since this product uses an ethylene-vinyl acetate copolymer, the heating dimensional change rate did not become 1% or less.

[Comparative Example 15]
A reactor having an internal volume of 100 liters equipped with a stirrer was charged with 36 liters of deionized water, 75 g of magnesium pyrophosphate and 6 g of sodium dodecylbenzenesulfonate, and then 120 g of benzoyl peroxide and t-butylperoxy as a polymerization initiator. 46 kg of styrene in which 29 g of benzoate was dissolved was placed in a reactor and stirred. After the temperature was raised to 90 ° C. and held for 6 hours, the temperature was raised to 125 ° C. and held for 3 hours for polymerization. The polymerization conversion rate at the end of the polymerization was 99.98%. Thereafter, the contents were taken out by cooling, washed and dehydrated and dried, and then passed through a sieve to obtain polystyrene resin particles having a particle size of 0.9 to 1.2 mm. The polystyrene resin particles had a weight average molecular weight of 280000.

  In a pressure vessel equipped with a stirrer with an internal volume of 5 liters, a suspension obtained by suspending 0.5 g of sodium dodecylbenzenesulfonate, 6 g of magnesium pyrophosphate and 20 g of toluene in 2 liters of water is added, and the polystyrene is stirred. 2 kg of resin particles and 60 g of tris (2,3-dibromopropyl) isocyanurate as a flame retardant were put in a container, and after the temperature was raised to 100 ° C. with stirring, 98 g of normal butane at an impregnation temperature of 100 ° C. 42 g of isobutane was injected and held for 3 hours. Next, after cooling to 25 ° C. and taking out the resin particles from the pressure vessel, the resin particles were washed and dehydrated and dried to obtain expandable polystyrene resin particles.

  After holding the expandable resin particles in a thermostatic chamber at 20 ° C. for 5 days, the expanded resin particles were pre-expanded to a bulk ratio of 30 times to obtain expanded polystyrene resin particles. The obtained polystyrene resin expanded particles are allowed to stand at room temperature for 1 day, then placed in a mold of 400 × 300 × 50 mm size, introduced with water vapor and heated, and then the expanded molded product is cooled and expanded. The molded body was taken out.

  The burning rate of the foamed molded product with a bulk magnification of 30 times is 31.8 mm / min, the heating dimensional change rate at 80 ° C. and 168 hr of the foamed molded product with a bulk magnification of 30 times is 1.5%, and the chemical resistance evaluation is × Met. Since this product uses polystyrene resin, the heating dimensional change rate did not become 1% or less. Also in the chemical resistance evaluation, since a polystyrene resin was used, the surface of the test piece melted immediately after applying gasoline, and a large amount of depression was generated on the surface of the test piece after 60 minutes.

  The results of Examples 1 to 7 and Comparative Examples 1 to 15 are summarized in Table 1.

The meanings of the abbreviations described in Table 1 are as follows.
PP (A): Polypropylene resin (manufactured by Sun Allomer, trade name PC540R),
PP (B): Polypropylene resin (manufactured by Prime Polymer, trade name F-794NV),
LLDPE: linear low density polyethylene resin (manufactured by Nihon Unicar Co., Ltd., trade name TUF-2032),
EVA: ethylene-vinyl acetate copolymer resin (manufactured by Nippon Polyethylene Co., Ltd., trade name LV-121),
Polymer: Modified resin particles, or carbon-containing modified resin particles,
QP: PP particles, PP particles containing carbon, LLDPE particles, LLDPE particles containing carbon, EVA particles, or EVA particles containing carbon,
SM: styrene monomer,
Flame retardant (A): Tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd., trade name TAIC-6B),
Flame retardant (B): Tetrabromocyclooctane (Daiichi Kogyo Seiyaku Co., Ltd., trade name FR-200),
Flame retardant (C): Tetrabromobisphenol-A-bis (2,3-dibromopropyl ether) (Daiichi Kogyo Seiyaku Co., Ltd., trade name SR-720).

  Next, Examples 8 to 12 in which a flame retardant aid is further added will be described. As the flame retardant aid, 2,3-dimethyl-2,3-diphenylbutane (D) or dicumyl peroxide (E) was used.

[Example 8]
In the flame retardant impregnation step of Example 1, 400 g of 2,3-dimethyl-2,3-diphenylbutane (D) was added together with the flame retardant, and the other processes were performed in the same manner as in Example 1.

[Example 9]
In the flame retardant impregnation step of Example 4, 400 g of 2,3-dimethyl-2,3-diphenylbutane (D) was added together with the flame retardant, and the other processes were performed in the same manner as in Example 4.

[Example 10]
In the flame retardant impregnation step of Example 4, 120 g of 2,3-dimethyl-2,3-diphenylbutane (D) was added together with the flame retardant, and the other processes were performed in the same manner as in Example 4.

[Example 11]
In the flame retardant impregnation step of Example 4, 800 g of 2,3-dimethyl-2,3-diphenylbutane (D) was added together with the flame retardant, and the other processes were performed in the same manner as in Example 4.

[Example 12]
400 g of dicumyl peroxide (E) was added in place of the flame retardant aid 2,3-dimethyl-2,3-diphenylbutane (D) added in Example 9, and the same procedure as in Example 9 was performed except that. It was.

  About the Examples 8-12 mentioned above, the test similar to the case of Examples 1-7 mentioned above was done. The results are summarized in Table 2.

  As a result of the test, flame retardance better than that of the corresponding examples was obtained by further adding a flame retardant aid.

Claims (11)

A polystyrene-modified polypropylene resin particle containing 100 to 400 parts by mass of a polystyrene resin with respect to 100 parts by mass of a polypropylene resin,
The resin particle contains a flame retardant containing tris (2,3-dibromopropyl) isocyanurate as a main component in an amount of 1.5 to 8.0 parts by mass with respect to 100 parts by mass of the resin particles. Quality polypropylene resin particles.   The styrene-modified polypropylene resin particles according to claim 1, wherein carbon particles are contained in the resin particles in an amount of 0.5 to 8.0 mass%.   One or two selected from the group consisting of 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, cumene hydroperoxide The styrene-modified polypropylene resin particles according to claim 1 or 2, wherein the flame retardant aid is contained in an amount of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the resin particles.   A styrene-modified polypropylene-based expandable resin particle, wherein the styrene-modified polypropylene-based resin particle according to claim 1 contains a foaming agent.   A styrene-modified polypropylene resin pre-expanded particle obtained by pre-expanding the styrene-modified polypropylene-based expandable resin particle according to claim 4.   A styrene-modified polypropylene resin foam molded article obtained by in-mold foam molding of the styrene-modified polypropylene resin foam particles according to claim 5. Combustion rate in accordance with US automobile safety standard FMVSS 302 is 80 mm / min or less, shrinkage rate under conditions of 80 ° C. in accordance with JIS K 6767 is 1.0% or less, and bulk ratio is 20 to 40 times. And a bulk density of 0.025 to 0.05 g / cm ^3. 7. The styrene-modified polypropylene resin foam molded article according to claim 6.   Polypropylene resin particles are dispersed in an aqueous suspension containing a dispersant, and then polymerization is started with 100 to 400 parts by mass of a styrene monomer with respect to 100 parts by mass of the polypropylene resin particles. And a step of suspension polymerization of the styrene monomer, and a step of impregnating the resin particles during or after the polymerization with a flame retardant mainly composed of tris (2,3-dibromopropyl) isocyanurate A method for producing styrene-modified polypropylene resin particles comprising:   The method for producing styrene-modified polypropylene resin particles according to claim 8, wherein the resin particles contain 0.5 to 8.0% by mass of carbon particles.   One or two selected from the group consisting of 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, cumene hydroperoxide The method for producing styrene-modified polypropylene resin particles according to claim 8 or 9, wherein the flame retardant aid is contained in an amount of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the resin particles.   A styrene-modified polypropylene-based expandable resin particle is obtained by impregnating the obtained styrene-modified polypropylene-based resin particles with a foaming agent in any step of the production method according to claim 8. A process for producing a styrene-modified polypropylene-based expandable resin particle.