JP2020105340A - Flame-retardant foamable composite resin particle, production method therefor and foam molded body - Google Patents

Abstract

To provide a flame-retardant foamable composite resin particle capable of producing a foam molded body having a desired flame retardancy.SOLUTION: A flame-retardant foamable composite resin particle is composed at least of a substrate resin including polyolefin-based and polystyrene-based resins and a flame retardant. The flame retardant does not include a halogen-based flame retardant, but includes a non-halogen-based one containing phosphorus and having 3 or more of phenyl groups. The non-halogen-based flame retardant of 2 to 15 pts.mass based on 100 pts.mass of the substrate resin is included in the flame retardant foamable composite resin particle so that (i) an absorbance ratio (D960/D1600) of the surface layer of the composite resin particle indicates 0.9 or more and (ii) that ratio (D960/D1600) of the central part of the above particle indicates 0.7 or less (here, the absorbance ratio is a ratio of the absorbance (D960) of 960 cm-1 and that (D1600) of 1600 cm-1 obtained from an infrared absorption spectrum measured by ATR method infrared spectroscopic analysis; D960 indicates the peak absorbance of a functional group including phosphorus; and D1600 indicates the peak absorbance of polystyrene).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to flame-retardant expanded composite resin particles, a method for producing the same, and an expanded molded article. More specifically, the present invention relates to a flame-retardant expanded composite resin particle containing no halogen-based flame retardant, a method for producing the same, and a foamed molded product.

It is known that a foam molded article made of a polystyrene resin is excellent in rigidity, heat insulation, lightness, water resistance and foam molding. On the other hand, it is known that a foamed molded article made of a polyolefin resin has excellent chemical resistance and impact resistance. As a foam-molded article having excellent properties of both resins, a foam-molded article obtained from composite resin particles of polystyrene-based resin and polyolefin-based resin has been proposed.

By the way, the foamed molded product has a problem that it is easily burned. Therefore, a technique for imparting flame retardancy to the foamed molded product obtained from the composite resin particles has been reported in, for example, Japanese Patent Application Laid-Open No. 2017-2236 (Patent Document 1). In Patent Document 1, a brominated flame retardant, which is a type of halogen-based flame retardant, is used to impart flame retardancy to a foam molded article obtained from composite resin particles.
Further, the present invention relates to a foamed molded product made of polystyrene resin instead of composite resin particles, but JP-A-2014-145068 (Patent Document 2) reports a technique of imparting flame retardancy to the foamed molded product. ..

JP, 2017-2236, A JP, 2014-145068, A

Halogen-based flame retardants are preferably used because the flame retardancy can be easily imparted by adding a small amount of them. However, halogen-based flame retardants have a problem that they generate corrosive or toxic gas when they are processed or burned as waste. Therefore, in recent years, with increasing concern about environmental problems, it has been desired to provide a foamed molded product that exhibits desired flame retardancy without containing a halogen-based flame retardant.

Patent Document 2 proposes a non-halogen flame retardant for a foam molded article made of a polystyrene resin. However, in a composite of a polyolefin-based resin and a polystyrene-based resin, when the halogen-based flame retardant is not contained, a suitable location of the non-halogen-based flame retardant has not been proposed.

In view of the above problems, the inventors of the present invention, in a composite of a polyolefin-based resin and a polystyrene-based resin, if a non-halogen flame retardant is present at a specific position, without containing a halogen flame retardant. The present invention has been accomplished by unexpectedly finding that desired flame retardancy can be obtained.

Thus, according to the present invention, a base resin containing a polyolefin-based resin and a polystyrene-based resin, and a flame-retardant foamed composite resin particle composed at least of a flame retardant,
The flame retardant contains no halogen-based flame retardant, contains phosphorus, and contains a non-halogen flame retardant having 3 or more phenyl groups,
The non-halogen flame retardant is contained in 2 to 15 parts by mass with respect to 100 parts by mass of the base resin,
The non-halogen flame retardant, the surface layer and the central portion of the flame-retardant foamed composite resin particles, the absorbance ratio in the following range:
(I) The absorbance ratio (D960/D1600) of the surface layer is 0.9 or more,
(Ii) Absorbance ratio (D960/D1600) of the central portion is 0.7 or less (the above-mentioned absorbance ratio is 960 cm ⁻¹ absorbance (D960) and 1600 cm obtained from the infrared absorption spectrum measured by ATR infrared spectroscopy). It is a ratio with respect to the absorbance (D1600) of ^-1 , where the D960 indicates the absorbance of the peak of the functional group containing phosphorus, and the D1600 indicates the absorbance of the polystyrene peak.)
The flame-retardant foamed composite resin particles are contained in the flame-retardant foamed composite resin particles.

Further, according to the present invention, there is provided a foamed molded product obtained by foaming and molding the foamed particles.
Furthermore, according to the present invention, there is provided a method for producing the flame-retardant expanded composite resin particles,
Composite resin particles containing a polyolefin resin and a polystyrene resin,
-In the presence of a non-halogen flame retardant, a foaming agent is impregnated to obtain expandable composite resin particles and then expanded, or-A foaming agent is impregnated to obtain expandable composite resin particles and then expanded. Then, a non-halogen flame retardant is spread on the flame-retardant expanded composite resin particles to provide a flame-retarded expanded composite resin particles.

ADVANTAGE OF THE INVENTION According to this invention, the flame-retardant foaming composite resin particle which can manufacture the foaming molding which has desired flame retardancy can be provided, even if it does not contain a halogen-type flame retardant.
In any of the following cases, it is possible to provide flame-retardant foamed composite resin particles capable of producing a foamed molded article having improved flame retardancy without containing a halogen-based flame retardant.
(A) The polyolefin resin and the polystyrene resin are contained in an amount of 5 to 50 parts by mass and 95 to 50 parts by mass, respectively, based on 100 parts by mass of both resins.
The non-halogen flame retardant (B) has the following general formula (I):

(In the formula, X is a phenyl group which may have a substituent, R ¹ and R ² are the same or different and are a hydrogen atom, an alkyl group, an alkoxyl group or a phenyl group, and m 1 and m 2 Is an integer of 1 to 5)
It is a phosphate ester flame retardant represented by.
The non-halogen flame retardant (C) has the following structural formulas (1) to (3):

Is selected from the following.

(Flame-retardant expanded composite resin particles)
The flame-retardant expanded composite resin particles are composed of at least a base resin containing a polyolefin resin and a polystyrene resin, and a flame retardant.

(I) Polyolefin-based resin The polyolefin-based resin is not particularly limited, and known resins can be used. Further, the polyolefin resin may be crosslinked. For example, branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, polyethylene-based resins such as cross-linked products of these polymers. , Polypropylene homopolymers, ethylene-propylene random copolymers, propylene-1-butene copolymers, ethylene-propylene-butene random copolymers and the like. In addition, the said polyolefin resin may be used individually and may be used in combination of 2 or more type. In the above example, low density is preferably 0.91~0.94g / cm ^3, more preferably 0.91~0.93g / cm ^3. High density is preferably 0.95~0.97g / cm ^3, more preferably 0.95~0.96g / cm ^3. Medium density is an intermediate density between these low density and high density.

The polyolefin resin preferably has a melting point of 95 to 150°C. When the melting point is lower than 95°C, heat resistance may be deteriorated. When the temperature is higher than 150°C, foaming becomes nonuniform and it may be difficult to obtain uniform expanded particles. A more preferable melting point is 100 to 145°C, and a still more preferable melting point is 105 to 145°C. The melting point is obtained, for example, by the DSC method.

The polyolefin resin preferably has an MFR of 0.3 to 15 g/10 minutes. When the MFR is less than 0.3 g/10 minutes, foaming variation may occur during foaming. If it is higher than 15 g/10 minutes, the heat resistance may decrease and the foamed molded product may shrink. A more preferable MFR is 0.5 to 10 g/10 minutes, and even more preferably 0.5 to 5 g/10 minutes. The MFR is obtained, for example, according to JIS K 7210:1999.

(Ii) Polystyrene Resin As the polystyrene resin, polystyrene, a polymer of substituted styrene (substituents include lower alkyl, halogen atom (especially chlorine atom), etc.), styrene as a main component, and styrene Examples thereof include copolymers with other polymerizable monomers. The main component means that styrene accounts for 70% by mass or more of all monomers. Examples of the substituted styrene include chlorostyrenes, vinyltoluenes such as p-methylstyrene, and α-methylstyrene. As the other monomer, in addition to substituted styrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylic acid alkyl ester, methacrylic acid alkyl ester, maleic acid mono- or dialkyl, divinylbenzene, ethylene glycol mono or Examples include di(meth)acrylic acid ester, polyethylene glycol dimethacrylate, maleic anhydride, N-phenyl maleide and the like. In the examples, alkyl means alkyl having 1 to 8 carbon atoms.

(Iii) Content ratio of polyolefin-based resin and polystyrene-based resin As the base resin, 5 to 50 parts by mass and 95 to 50 parts by mass of the polyolefin-based resin and the polystyrene-based resin are added to 100 parts by mass of both resins, respectively. It is preferable to include a part. When the content of the polystyrene-based resin is more than 95 parts by mass, the crack resistance of the foamed molded product may decrease. On the other hand, if it is less than 50 parts by mass, the crack resistance is significantly improved, but the rigidity may be lowered. The content of the polystyrene resin is preferably 85 to 50 parts by mass.

(Iv) Other resin The base resin may contain a resin other than the polyolefin resin and the polystyrene resin. Examples of other resins include acrylic resins derived from acrylic monomers such as acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, alkyl acrylates, and alkyl methacrylates.

(V) Flame Retardant The flame retardant contains a non-halogen flame retardant containing phosphorus and having 3 or more phenyl groups. The flame retardant contains no halogen-based flame retardant.
(V-1) Non-halogen flame retardant containing phosphorus and having 3 or more phenyl groups A non-halogen flame retardant containing phosphorus and having 3 or more phenyl groups (hereinafter, also simply referred to as non-halogen flame retardant) is There is no particular limitation as long as the desired flame retardancy can be obtained without containing a halogen-based flame retardant. From the viewpoint of obtaining desired flame retardancy, the non-halogen flame retardant is preferably a flame retardant containing a phosphorus atom in its molecular structure, and more preferably a phosphate ester flame retardant. As the phosphate ester flame retardant, the following general formula (I):

(In the formula, X is a phenyl group which may have a substituent, R ¹ and R ² are the same or different and are a hydrogen atom, an alkyl group, an alkoxy group or a phenyl group, and m 1 and m 2 Is an integer of 1 to 5)
The flame retardant represented by
Examples of the substituent include a lower alkyl group, a lower alkoxyl group, a phenyl group and a phosphoryl group (herein, lower means, for example, 1 to 4 carbon atoms).

In R ¹ and R ² , the alkyl group is preferably a group having 1 to 4 carbon atoms. Specific examples include methyl, ethyl, propyl, butyl and the like (including possible structural isomers).
In R ¹ and R ² , the alkoxy group is preferably a group having 1 to 4 carbon atoms. Specific examples include methoxy, ethoxy, propoxy, butoxy and the like (including possible structural isomers).
Specific non-halogen flame retardants include the following structural formulas (1) to (3):

Agent.

(V-2) Content of non-halogen flame retardant The non-halogen flame retardant is contained in 2 to 15 parts by mass with respect to 100 parts by mass of the base resin.
When the content of the non-halogen flame retardant is less than 2 parts by mass, sufficient flame retardancy may not be obtained. If the amount is more than 15 parts by mass, the thermal characteristics may be deteriorated or the fusion during molding may be defective. The content is preferably 2 to 13 parts by mass, more preferably 2 to 10 parts by mass.

(V-3) Location of non-halogen flame retardant The non-halogen flame retardant has an absorbance ratio in the following range in the surface layer and the central portion of the flame-retardant expanded composite resin particles:
(I) The absorbance ratio (D960/D1600) of the surface layer is 0.9 or more,
(Ii) It is contained in the flame-retardant foamed composite resin particles so that the absorbance ratio (D960/D1600) of the central part is 0.7 or less. Incidentally, the absorbance ratio is the ratio of the ATR method infrared spectroscopy absorbance of 960 cm ^-1 derived from the measured infrared absorption spectrum by (D960) and 1600cm absorbance ^-1 (D1600). Further, D960 shows the absorbance of the peak of the functional group containing phosphorus, and D1600 shows the absorbance of the peak of polystyrene. Therefore, the relationship of the absorbance ratio between the surface layer and the central portion means that the surface layer of the particles contains more halogen-free flame retardant than the central portion.
If the absorbance ratio of the surface layer is less than 0.9, the desired flame retardancy may not be obtained. The absorbance ratio of the surface layer is preferably 0.9 to 4.0, more preferably 0.9 to 3.5.
When the absorbance ratio of the central portion is larger than 0.7, mechanical properties and heat resistance may be deteriorated. The absorbance ratio of the central portion is preferably 0 to 0.7, and more preferably 0 to 0.6.
The absorbance ratio of the surface layer is preferably 1.2 or more and more preferably 3 or more than the absorbance ratio of the central portion.

(Vi) Other Additives The flame-retardant expanded composite resin particles have a flame-retardant aid, a plasticizer, a lubricant, an anti-bonding agent, a fusion-promoting agent, an antistatic agent, and a spreading agent as long as the physical properties are not impaired. Additives such as agents, bubble control agents, cross-linking agents, fillers, and coloring agents may be included.

Examples of the flame retardant aid include organic peroxides such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide and cumene hydroperoxide. Can be mentioned.
Examples of the plasticizer include phthalic acid esters, glycerin diacetomonolaurate, glycerin tristearate, glycerin fatty acid esters such as diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.
Examples of lubricants include paraffin wax.

Examples of the binding inhibitor include calcium carbonate, silica, aluminum hydroxide, ethylene bisstearic acid amide, tricalcium phosphate, dimethyl silicon and the like.
Examples of the fusion promoter include stearic acid, zinc stearate, stearic acid triglyceride, hydroxystearic acid triglyceride, stearic acid sorbitan ester, and polyethylene wax.
Examples of the spreading agent include polybutene, polyethylene glycol, silicone oil and the like.
Examples of the cell regulator include methacrylic acid ester-based copolymers, ethylenebisstearic acid amide, polyethylene wax, and ethylene-vinyl acetate copolymers.

(Vii) Shape The shape of the flame-retardant expanded composite resin particles is not particularly limited. For example, a spherical shape, a cylindrical shape, etc. may be mentioned. Of these, the spherical shape is preferable. The average particle diameter of the flame-retardant expanded composite resin particles can be appropriately selected according to the application, and for example, those having an average particle diameter of 1 to 5 mm can be used. Further, in consideration of the filling property into the molding die during the production of the foamed molded product, the average particle diameter is more preferably 1 to 2 mm, further preferably 1 to 1.4 mm.

(Method for producing flame-retardant expanded composite resin particles)
Flame-retardant foamed composite resin particles, for example, composite resin particles containing a polyolefin-based resin and polystyrene-based resin,
-In the presence of a non-halogen flame retardant, a foaming agent is impregnated to obtain expandable composite resin particles and then expanded, or-A foaming agent is impregnated to obtain expandable composite resin particles and then expanded. Then, it can be obtained by spreading a non-halogen flame retardant.

(1) Composite Resin Particles Resin particles containing a base resin obtained by simply mixing a polyolefin resin and a polystyrene resin can be used as the composite resin particles, but polyolefin-modified styrene resin particles described below are preferable. ..
Polyolefin-modified styrenic resin particles (also referred to as modified resin particles) are obtained by adding a styrene-based monomer to an aqueous medium in which polyolefin-based resin particles (seed particles) are dispersed and held to form styrene-based resin particles. It is obtained by impregnating and polymerizing a monomer. The method for producing the modified resin particles will be described below.

The polyolefin resin particles for producing the modified resin particles can be obtained by a known method. For example, the polyolefin-based resin particles can be produced by melt-extruding the polyolefin-based resin using an extruder and then granulating by underwater cutting, strand cutting, or the like. The polyolefin-based resin particles may have, for example, a spherical shape, an elliptic spherical shape (egg shape), a cylindrical shape, a prismatic shape, a pellet shape, a granular shape, or the like. Hereinafter, the polyolefin resin particles are also referred to as micropellets.

The polyolefin resin particles may contain a radical scavenger. The radical scavenger may be added to the polyolefin resin in advance, or may be added simultaneously with the melt extrusion. As the radical scavenger, a compound having an action of trapping a radical such as a polymerization inhibitor (including a polymerization inhibitor), a chain transfer agent, an antioxidant, a hindered amine light stabilizer, which is difficult to dissolve in water is preferable. ..

Examples of the polymerization inhibitor include t-butylhydroquinone, paramethoxyphenol, 2,4-dinitrophenol, t-butylcatechol, sec-propylcatechol, N-methyl-N-nitrosoaniline, N-nitrosophenylhydroxylamine, triphenyl. Phosphite, tris(nonylphenylphosphite), triethylphosphite, tris(2-ethylhexyl)phosphite, tridecylphosphite, tris(tridecyl)phosphite, diphenylmono(2-ethylhexyl)phosphite, diphenylmonodecylphosphite Phenol-based polymerization inhibitors such as fight, diphenylmono(tridecyl)phosphite, dilaurylhydrogenphosphite, tetraphenyldipropylene glycol diphosphite, tetraphenyltetra(tridecyl)pentaerythritol tetraphosphite, nitroso-based polymerization inhibitors, Examples include aromatic amine-based polymerization inhibitors, phosphite ester-based polymerization inhibitors, thioether-based polymerization inhibitors, and the like.

Examples of chain transfer agents include β-mercaptopropionic acid 2-ethylhexyl ester, dipentaerythritol hexakis(3-mercaptopropionate), tris[(3-mercaptopropionyloxy)-ethyl]isocyanurate, and the like. To be done.

Antioxidants include 2,6-di-t-butyl-4-methylphenol (BHT), n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, pentaeryth. Lytyl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate , 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 3,9-bis[2-{3-(3-t- Butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, distearyl pentaerythritol diphosphite, tris (2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-t-butylphenyl)4,4 '-Biphenylene diphosphonate, bis(2-t-butyl-4-methylphenyl)pentaerythritol diphosphite, 2,4,8,10-tetra-t-butyl-6-[3-(3-methyl -4-Hydroxy-5-t-butylphenyl)propoxy]dibenzo[d,f][1,3,2]dioxaphosphine, phenyl-1-naphthylamine, octylated diphenylamine, 4,4-bis(α) , Α-Dimethylbenzyl)diphenylamine, N,N′-di-2-naphthyl-p-phenylenediamine, and other phenolic antioxidants, phosphorus antioxidants, amine antioxidants, and the like.

Examples of the hindered amine light stabilizer include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and bis(1 , 2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate and the like.
The amount of the radical scavenger used is preferably 0.005 to 0.5 parts by mass with respect to 100 parts by mass of the polyolefin resin particles.

The polyolefin-based resin particles may contain, in addition, a foam nucleating agent such as talc, calcium silicate, calcium stearate, synthetically or naturally produced silicon dioxide, ethylenebisstearic acid amide, and a methacrylic acid ester-based copolymer. Good.
Next, the micropellets are dispersed in an aqueous medium in a polymerization container, and polymerization is performed while impregnating the styrene-based monomer in the micropellets.
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, alcohol).

A solvent (plasticizer) such as toluene, xylene, cyclohexane, ethyl acetate, dioctyl phthalate, or tetrachloroethylene may be added to the styrene-based monomer.
The amount of the styrene-based monomer used is 95 to 50 parts by mass based on 100 parts by mass of the total of the polyolefin-based resin particles and the styrene-based monomer. The amount used is preferably 85 to 50 parts by mass. This usage amount substantially corresponds to the contents of the polyolefin-based resin and the polystyrene-based resin forming the foamed molded product.
When the amount of the styrene-based monomer used exceeds 95 parts by mass, the particles of the polystyrene-based resin alone may be generated without being impregnated with the polyolefin-based resin particles. In addition, not only the crack resistance of the foamed molded article may be reduced, but also the chemical resistance may be reduced. On the other hand, if the amount is less than 50 parts by mass, the ability of the expandable composite resin particles to retain the foaming agent may decrease. If it decreases, it becomes difficult to achieve high foaming. In addition, the rigidity of the foamed molded product may decrease.

Impregnation of the styrene-based monomer into the polyolefin-based resin particles may be carried out during the polymerization, or may be carried out before starting the polymerization. Of these, it is preferable to carry out the polymerization. When the polymerization is performed after the impregnation, the styrene monomer is likely to be polymerized in the vicinity of the surface of the polyolefin resin particles, and the styrene monomer that is not impregnated in the polyolefin resin particles is used alone. In some cases, a large amount of fine particle polystyrene resin particles are produced by the polymerization.
When performing the impregnation while polymerizing, the polyolefin resin particles in the case of calculating the content is composed of a styrene monomer impregnated with a polyolefin resin, and a polystyrene resin further impregnated and already polymerized. Mean particles.
The styrene monomer can be added continuously or intermittently to the aqueous medium in the polymerization vessel. Particularly, it is preferable to gradually add the styrene-based monomer to the aqueous medium.

An oil-soluble radical polymerization initiator can be used for the polymerization of the styrene-based monomer. As this polymerization initiator, a polymerization initiator commonly used for the polymerization of styrene-based monomers can be used. For example, benzoyl peroxide, lauroyl peroxide, t-butyl peroxyoctoate, t-hexyl peroxyoctoate, t-butyl peroxybenzoate, t-amyl peroxybenzoate, t-butyl peroxy vivarate, t- Butyl peroxy isopropyl carbonate, t-hexyl peroxy isopropyl carbonate, t-butyl peroxy-3,3,5-trimethylcyclohexanoate, di-t-butyl peroxy hexahydroterephthalate, 2,2-di-t- Examples thereof include organic peroxides such as butylperoxybutane, di-t-hexyl peroxide, and dicumyl peroxide, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. In addition, these oil-soluble radical polymerization initiators may be used alone or in combination.

As a method of adding the polymerization initiator to the aqueous medium in the polymerization container, various methods can be mentioned. For example,
(A) A method in which a polymerization initiator is dissolved and contained in a styrene-based monomer in a container different from the polymerization container, and the styrene-based monomer is supplied into the polymerization container.
(B) A polymerization initiator is dissolved in a part of the styrene-based monomer, a solvent such as isoparaffin, or a plasticizer to prepare a solution. This solution, a method of simultaneously supplying a predetermined amount of styrene-based monomer into the polymerization vessel,
(C) A dispersion liquid in which a polymerization initiator is dispersed in an aqueous medium is prepared. Examples include a method of supplying this dispersion liquid and a styrene-based monomer into a polymerization container.

The proportion of the polymerization initiator used is preferably 0.02 to 2.0 mass% of the total amount of the styrene-based monomer used.
It is preferable to dissolve a water-soluble radical polymerization inhibitor in the aqueous medium. The water-soluble radical polymerization inhibitor not only suppresses the polymerization of the styrene-based monomer on the surface of the polyolefin-based resin particles, but also prevents the styrene-based monomer floating in the aqueous medium from polymerizing alone, Generation of fine particles of polystyrene resin can be reduced.

As the water-soluble radical polymerization inhibitor, a polymerization inhibitor soluble in 1 g or more in 100 g of water can be used, and examples thereof include thiocyanates such as ammonium thiocyanate, zinc thiocyanate, sodium thiocyanate, potassium thiocyanate and aluminum thiocyanate. Acid salt, sodium nitrite, potassium nitrite, ammonium nitrite, calcium nitrite, silver nitrite, strontium nitrite, cesium nitrite, barium nitrite, magnesium nitrite, lithium nitrite, nitrite such as dicyclohexylammonium nitrite, mercapto Water-soluble sulfur-containing organic compounds such as ethanol, monothiopropylene glycol, thioglycerol, thioglycolic acid, thiohydroacrylic acid, thiolactic acid, thiomalic acid, thioethanolamine, 1,2-dithioglycerol, 1,3-dithioglycerol Further, ascorbic acid, sodium ascorbate and the like can be mentioned. Among these, nitrite is particularly preferable.

The amount of the water-soluble radical polymerization inhibitor used is preferably 0.001 to 0.04 parts by mass with respect to 100 parts by mass of water in the aqueous medium.
In addition, it is preferable to add a dispersant to the aqueous medium. Examples of such a dispersant include partially saponified polyvinyl alcohol, polyacrylic acid salt, polyvinylpyrrolidone, carboxymethylcellulose, organic dispersants such as methylcellulose, magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium phosphate. Inorganic dispersants such as magnesium carbonate and magnesium oxide. Of these, inorganic dispersants are preferred.
When an inorganic dispersant is used, it is preferable to use a surfactant together. Examples of such a surfactant include sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate.

The shape and structure of the polymerization vessel are not particularly limited as long as they have been conventionally used for suspension polymerization of styrene-based monomers.
The shape of the stirring blade is also not particularly limited, and specifically, paddle blades such as V-type paddle blades, furdler blades, inclined paddle blades, flat paddle blades, and pull margin blades, turbine blades, fan turbine blades, etc. Examples thereof include turbine blades and propeller blades such as marine propeller blades. Among these stirring blades, the paddle blade is preferable. The stirring blade may be a single-stage blade or a multi-stage blade. A baffle may be provided in the polymerization container.

Further, the temperature of the aqueous medium when polymerizing the styrene-based monomer in the micropellets is not particularly limited, but within a range of −30 to +20° C. of the melting point (measured by the DSC method) of the polyolefin-based resin used. It is preferable to have. More specifically, 70 to 140°C is preferable, and 80 to 130°C is more preferable. Furthermore, the temperature of the aqueous medium may be a constant temperature from the start to the end of the polymerization of the styrene-based monomer, or may be increased stepwise. When increasing the temperature of the aqueous medium, it is preferable to increase the temperature at a temperature rising rate of 0.1 to 2° C./min.
Furthermore, when using particles made of a cross-linked polyolefin-based resin, the cross-linking may be performed in advance before impregnating the styrene-based monomer, or by impregnating the styrene-based monomer in the micropellets and polymerizing. It may be carried out during the heating, or may be carried out after impregnating and polymerizing the styrene monomer in the micropellets.

Examples of the crosslinking agent used for crosslinking the polyolefin resin include 2,2-di-t-butylperoxybutane, dicumyl peroxide, and 2,5-dimethyl-2,5-di-t-butylperoxy. An organic peroxide such as hexane may be used. The crosslinking agents may be used alone or in combination of two or more. The amount of the crosslinking agent used is usually preferably 0.05 to 1.0 parts by mass with respect to 100 parts by mass of the polyolefin resin particles (micropellets).

Examples of the method for adding the cross-linking agent include, for example, a method of directly adding to the polyolefin resin particles, a method of dissolving the cross-linking agent in a solvent, a plasticizer or a styrene-based monomer, and a method of adding the cross-linking agent to water. The method of adding after making it etc. is mentioned. Among these, a method in which the crosslinking agent is dissolved in the styrene-based monomer and then added is preferred.
Modified resin particles are obtained by the above method.

(2) Foaming Agent Impregnation Step The foaming agent is not particularly limited, and any known foaming agent can be used. In particular, a compound having a boiling point not higher than the softening point of the styrene resin and being gaseous or liquid at normal pressure is suitable. For example, hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane and petroleum ether, ketones such as acetone and methyl ethyl ketone, methanol, ethanol, isopropyl alcohol and the like. Low boiling point ether compounds such as alcohols, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane, inorganic gases such as carbon dioxide, nitrogen and ammonia. Can be mentioned. These foaming agents may be used alone or in combination of two or more. Among these, it is preferable to use hydrocarbons from the viewpoint of preventing the ozone layer from being destroyed and quickly replacing it with air to suppress the change over time of the foamed molded product. Among the hydrocarbons, propane, n-butane, isobutane, n-pentane, isopentane and the like are more preferable.

The foaming agent may be impregnated into the composite resin particles after the polymerization or the particles of the styrene monomer during the polymerization. The impregnation during the polymerization can be performed by a method of impregnating in an aqueous medium (wet impregnation method). The impregnation after the polymerization can be performed by a wet impregnation method or a method of impregnation in the absence of a medium (dry impregnation method). Further, it is preferable that the impregnation during the polymerization is usually performed in the latter stage of the polymerization.

The amount of the foaming agent used is preferably 5 to 18 parts by mass, and more preferably 5 to 13 parts by mass with respect to 100 parts by mass of the composite resin particles.
The non-halogen flame retardant may be used as it is at the time of impregnation of the foaming agent and at the time of its spreading, or may be used by being dispersed or dissolved in an appropriate solvent.

During the production of expandable composite resin particles, flame retardant aids, plasticizers, lubricants, anti-bonding agents, fusion promoters, antistatic agents, spreading agents, bubble control agents, cross-linking agents, fillers, colorants, etc. Additives may be used at any suitable stage.

Foaming can be performed using a heat medium (for example, pressurized steam or the like).
The non-halogen flame retardant may be used as it is at the time of spreading, or may be used by dispersing or dissolving it in a suitable solvent.
The bulk density of the flame-retardant expanded composite resin particles is preferably in the range of 0.01 to 0.20 g/cm ³ . When the bulk density of the flame-retardant foamed composite resin particles is smaller than 0.01 g/cm ³ , the foamed molded product obtained next may shrink and the appearance may be deteriorated. In addition, the heat insulation performance and the mechanical strength of the foamed molded product may decrease. On the other hand, when the bulk density is larger than 0.20 g/cm ³ , the lightness of the foamed molded product may decrease.
Prior to foaming, powdery soaps such as zinc stearate, hydroxystearic acid triglyceride, medium-chain saturated fatty acid triglyceride, and hardened tallow amide are preferably applied to the surface of the expandable composite resin particles. By coating, the bonding between the expanded particles can be reduced in the step of expanding the expandable composite resin particles.

(Foam molding)
The foamed molded product can be used as a cushioning material or a packaging material. Specifically, it is used as a cushioning material (cushioning material) for home appliances, electronic parts, various industrial materials, applications such as food containers, shock absorbers such as vehicle bumper core materials, door interior cushioning materials, etc. It can be suitably used for the purpose.

The density of the foamed molded product is preferably in the range of 0.01 to 0.20 g/cm ³ . When the density of the foamed molded product is less than 0.01 g/cm ³ , shrinkage may occur in the foamed molded product and the appearance may deteriorate. In addition, the heat insulation performance and the mechanical strength of the foamed molded product may decrease. On the other hand, when the density is higher than 0.20 g/cm ³ , the lightness of the foamed molded product may decrease.

The foamed molded article is obtained by filling the flame-retardant foamed composite resin particles in a closed mold having a large number of small holes, heat-foaming with a heat medium (for example, pressurized steam, etc.), and It can be manufactured by filling voids and integrating the flame-retardant expanded composite resin particles by fusing them together. At that time, the density of the foamed molded article can be adjusted, for example, by adjusting the filling amount of the flame-retardant expanded composite resin particles in the mold.
The heat-foaming is preferably performed, for example, by heating with a heat medium at 80 to 150° C. for 5 to 50 seconds. The forming vapor pressure (gauge pressure) of the heat medium is preferably in the range of 0.04 to 0.30 MPa.
The foamed molded product derived from the flame-retardant expanded composite resin particles of the present invention can pass the horizontal combustion test described in the section of the following examples while maintaining the buffer performance even if it does not contain a halogen-based flame retardant.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
The methods for measuring various physical properties in the following examples are described below.

<Absorbance ratio of center and surface layer>
The absorbance ratio (D960/D1600) was measured in the following manner.
That is, infrared absorption spectra of the central portion and the surface layer of each of 10 randomly selected flame-retardant expanded composite resin particles were obtained by ATR infrared spectroscopy.
Here, in the measurement of the central portion, each particle is divided into two equal parts (for example, a particle having a particle diameter of 5 mm is cut into 2.5±0.5 mm), and the center of the cut surface (at least from the center of the circle) The measurement was carried out by closely contacting the ATR prism to the inner side of 1/4).
Further, in the measurement of the surface layer, an ATR prism was brought into close contact with the surface of each particle for measurement.
The absorbance ratio (D960/D1600) was calculated from each infrared absorption spectrum, and the minimum absorbance ratio and the maximum absorbance ratio were excluded. Then, the arithmetic average of the remaining eight absorbance ratios was taken as the absorbance ratio (D960/D1600). The absorbance ratio (D960/D1600) was measured using, for example, a measuring device sold under the trade name "Fourier transform infrared spectrophotometer MAGNA 560" by Nicolet (current name: Thermofisher).

High refractive index crystal seed: Ge (germanium)
Incident angle: 45°±1°
Measurement area: 4000 cm ^{−1 to} 675 cm ⁻¹
Fractional dependence of measurement depth: Not corrected Number of reflections: 1 Detector: DTGS KBr
Resolution: 4 cm ^-1
Number of times of integration: 32 times Others: A process that does not participate in the measurement spectrum is performed using the infrared absorption spectrum measured without contact with the sample as the background. In the examples, the resolution is specified as 4 cm ⁻¹ and the peak separation is not performed. I asked. Then, a baseline a line connecting the wave number of minimum absorbance at the range of the minimum absorbance and 800 cm ^-1 ± 30 cm ^-1 in the range of 1400 cm ^-1 ± 30 cm ^-1, the maximum absorbance in the range of 960 cm ^-1 ± 10 cm ^-1 The wave number at which was taken was the peak position. The peak height from the baseline was D960.
Similarly, a straight line connecting the wave number with the smallest absorbance at wave number range of the 1525 cm ^-1 ± 15cm ^-1 to the minimum absorbance definitive range of 1660 cm ^-1 ± 30 cm ^-1 and a baseline, 1600 cm ^-1 ± 10 cm ^-1 The wave number at which the maximum absorbance was within the range was defined as the peak position. The peak height from the baseline was D1600.

<Bulk multiple of expanded composite resin particles>
The mass (a) of about 5 g of expanded composite resin particles was weighed to the second decimal place. Next, weighed foamed composite resin particles were put into a 500 cm ³ graduated cylinder whose minimum memory unit is 5 cm ³ , and a circular resin plate having a diameter slightly smaller than the caliber of the graduated cylinder was put into this and the width was about 1.5 cm. , The volume (b) of the expanded composite resin particles is read by applying a pressing tool on which a rod-shaped resin plate having a length of about 30 cm is upright and fixed, and the volume of the expanded composite resin particles is calculated by the formula (a)/(b). The density (g/cm ³ ) was determined. The bulk factor is the reciprocal of the bulk density, that is, the formula (b)/(a).

<Multiple of foam molded product>
Effective numbers of the mass (a:g) and volume (b:cm ³ ) of the test piece (Example 75 mm×300 mm×35 mm) cut out from the foamed molded product (which has been dried at 50° C. for 4 hours or more after molding). The measurement was carried out so that it would be 3 digits or more, and the multiple (times) of the foamed molded product was obtained by the formula (b)/(a). The density is the reciprocal of a multiple, that is, the formula (a)/(b).

<Shrinkage of foam molding>
The case where a clear shrinkage was observed in the shape of the foamed molded product immediately after molding was × (poor), the case where wrinkles were generated on the surface of the foamed molded product was ○, and the case where no shrinkage or wrinkle was observed was evaluated as ◎.

<Stickiness of foam molding>
The stickiness on the surface of the foamed molded product was confirmed by touching it with a finger. When there was no stickiness, it was evaluated as ◯ (good), and when there was stickiness, it was evaluated as x (bad).

<Combustion test>
The burning velocity in the horizontal direction was measured according to FMVSS 302. In addition, the test piece was set to have a multiple of 30 times, 350 mm×100 mm×12 mm (thickness), and at least 350 mm×100 mm had a skin on one side.
When the burning speed was 70 mm/min or less, the result was ◯ (good), and when it was greater than 70 mm/min, the result was x (bad).

<Comprehensive evaluation>
In the above shrinkage, stickiness and combustion test, if there is at least one x (poor), the combustion test and stickiness are evaluated as ○, but if the shrinkage is ○ (good), the combustion test and stickiness are evaluated as ○. When the shrinkage was ◎, it was marked as ⊚ (excellent).

(Example 1)
<Preparation of seed particles>
Ethylene-vinyl acetate copolymer (hereinafter referred to as EVA) particles (manufactured by Nippon Polyethylene Co., Ltd., trade name "LV-115A", melting point: 108°C) are heated and mixed by an extruder, and the mixture is granulated by strand cutting. Seed particles were obtained by pelletizing. The mass of the seed particles was adjusted to 38 mg per 100 particles. The average particle size of the seed particles was about 1 mm.

<Preparation of composite resin particles>
14 kg of seed particles were placed in a 100 L autoclave equipped with a stirrer. To this autoclave, 46 kg of pure water, 400 g of magnesium pyrophosphate, and 3 g of sodium dodecylbenzenesulfonate were added as an aqueous medium, and the mixture was stirred to suspend the seed particles in the aqueous medium and held for 10 minutes, after which the temperature was raised to 70°C. A suspension was obtained. 8 kg of styrene in which 9 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to this suspension over 60 minutes. After the dropping, the temperature was raised to 130° C., and stirring was continued at this temperature for 2 hours.
Then, the temperature was lowered to 90° C., 16 g of sodium dodecylbenzenesulfonate was added to this suspension and held for 10 minutes, and then 14 kg of styrene in which 50 g of benzoyl peroxide was dissolved as a polymerization initiator was added dropwise over 5 hours. After completion of this dropping, the mixture was held at 90° C. for 1 hour and 30 minutes and then heated to 144° C. and kept for 3 hours to complete the polymerization to obtain composite resin particles. The mass ratio (%) of polyolefin (EVA) and polystyrene in the composite resin particles was 40:60.

<Preparation of expandable composite resin particles>
7400 g of the composite resin particles and 74 g of water were put into a pressure resistant V-type rotary mixer having an internal volume of 16 dm ³ . After closing the lid, 1.97 g of butane (n-butane:i-butane=7:3) as a volatile foaming agent was press-fitted into the mixer at room temperature (about 25° C.). Thereafter, the temperature was raised to 70° C., the temperature was maintained for 2 hours, and then the temperature was cooled to 25° C. to obtain expandable composite resin particles.

<Preparation of expanded composite resin particles>
1000 g of the resulting expandable composite resin particles was put into a pre-expanding machine (manufactured by Kasahara Kogyo Co., Ltd., model: PSX40) having a can volume of 40 liters. Expanded composite resin particles were obtained by introducing steam having a gauge pressure of 0.01 MPa into the machine and heating it to foam it to a bulk multiple of about 32 times.
<Fire retardant spread>
500 g of the foamed composite resin particles and 25 g (5% by mass) of the phosphorus-based flame retardant Y (ADEKA STAB PFR manufactured by ADEKA) were put into a rotary mixer and mixed at room temperature for 20 minutes. After that, the contents were taken out and allowed to stand in an oven at 70° C. for 1 hour to obtain flame-retardant expanded composite resin particles having a phosphorus-based flame retardant spread on the surface.

<Foam molding production>
The flame-retardant foamed composite resin particles obtained were allowed to stand at 25° C. for 1 day, and then filled in the cavity of a molding die having an inner cavity of 400 mm length×300 mm width×30 mm thickness. The cracking was 3 mm, which is 10% of the thickness. Next, 0.09 MPa of steam is introduced into the mold for 50 seconds to heat it, and then cooled until the maximum surface pressure of the foamed molded product is reduced to 0.001 MPa to obtain a foamed molded product in a multiple of about 30 times. Obtained.

(Example 2)
In the flame retardant spreading step, the composite resin particles, the expandable composite resin particles, and the flame retardant were prepared in the same manner as in Example 1 except that 500 g of the foamed particles and 50 g (10% by mass) of the phosphorus-based flame retardant Y were added to the rotary mixer. Foamed composite resin particles (bulk multiple of about 32 times) and foamed molded products (multiple of about 28 times) were obtained.

(Example 3)
In the flame retardant spreading step, the composite resin particles, the expandable composite resin particles were prepared in the same manner as in Example 1 except that 500 g of the expanded composite resin particles and 75 g (15% by mass) of the phosphorus-based flame retardant Y were added to the rotary mixer. Flame-retardant foamed composite resin particles (bulk multiple of about 32 times) and foamed molded products (multiple of about 27 times) were obtained.

(Example 4)
A pressure resistant V-type rotary mixer having an internal volume of 16 dm ³ was charged with 7400 g of the composite resin particles, 74 g of water, and 370 g of a phosphorus-based flame retardant Y (ADEKA STAB PFR manufactured by ADEKA). After closing the lid, 1.97 g of butane (n-butane:i-butane=7:3) as a volatile foaming agent was press-fitted into the mixer at room temperature (about 25° C.). Thereafter, the flame-retardant expandable composite resin particles (in the same manner as in Example 1) were obtained except that the flame-retardant expandable composite resin particles were obtained by heating to 70° C., holding for 2 hours, and then cooling to 25° C. A bulk multiple of about 32 times) and a foamed molded product (multiple of about 30 times) were obtained.

(Example 5)
Composite resin particles, expandable composite resin particles, flame-retardant expanded composite resin particles in the same manner as in Example 1 except that the ADEKA ADEKA STAB PFR was changed to the ADEKA ADEKA STAB PF-600 (phosphorus flame retardant X). (Bulk factor about 32 times) and foamed molded product (factor about 30 times) were obtained.

(Comparative Example 1)
In the same manner as in Example 1 except that the non-halogen flame retardant was not used, the composite resin particles, the expandable composite resin particles, the flame-retardant expanded composite resin particles (bulk multiple of about 32 times), and the foam molded product (multiple) About 30 times).

(Comparative example 2)
In the flame retardant spreading step, the composite resin particles, the expandable composite resin particles, and the flame retardant were prepared in the same manner as in Example 1 except that 500 g of the expanded particles and 5 g (1% by mass) of the phosphorus-based flame retardant Y were added to the rotary mixer. Foamed composite resin particles (bulk multiple: about 32 times) and foamed molded products (multiple about 30 times) were obtained.

(Comparative example 3)
In the flame retardant spreading step, the composite resin particles, the expandable composite resin particles and the flame retardant were prepared in the same manner as in Example 1 except that 500 g of the expanded particles and 100 g (20% by mass) of the phosphorus-based flame retardant Y were added to the rotary mixer. Foamed composite resin particles (bulk multiple of about 32 times) and foamed molded products (multiple of about 24 times) were obtained.

(Comparative Example 4)
Composite resin particles, expandable composite resin particles, flame retardant were obtained in the same manner as in Example 1 except that the phosphorus flame retardant Y was changed to 40 g (8% by mass) of phosphorus flame retardant U (Disfamol DPO manufactured by Lanxess). Foamed composite resin particles (bulk multiple: about 32 times) and foamed molded products (multiple about 22 times) were obtained.

リン酸系難燃剤Ｘ：上記構造式（２）を主成分として９９質量％以上含む。
リン酸系難燃剤Ｙ：上記構造式（１）を主成分として９５〜９９質量％含み、リン酸トリフェニルを１〜５質量％含む。
得られた結果を表１にまとめて示す。表１中、Ａは発泡粒展着、Ｂはガス含浸時を意味する。 The components of the phosphorus-based flame retardants U, X and Y used in the above Examples and Comparative Examples are described below.
Phosphoric acid flame retardant U: Includes 88 to 93% by mass of the following structural formula as a main component, contains 5.5% by mass of phenyldi(2-ethylhexyl) phosphate and 1.5% by mass of triphenyl phosphate.

Phosphoric acid flame retardant X: Contains 99% by mass or more of the above structural formula (2) as a main component.
Phosphoric acid-based flame retardant Y: 95 to 99% by mass of the above structural formula (1) as a main component and 1 to 5% by mass of triphenyl phosphate.
The obtained results are summarized in Table 1. In Table 1, A means expanded particle spreading and B means gas impregnation.

From Table 1, a foamed molded product having a desired flame retardancy without containing a halogen-based flame retardant, due to the flame-retardant foamed composite resin particles containing a specific amount of the non-halogen-based flame retardant and having the non-halogen-based flame retardant unevenly distributed. You can see that

Claims (7)

A base resin containing a polyolefin-based resin and a polystyrene-based resin, and a flame-retardant foamed composite resin particle composed at least of a flame retardant,
The flame retardant contains no halogen-based flame retardant, contains phosphorus, and contains a non-halogen flame retardant having 3 or more phenyl groups,
The non-halogen flame retardant is contained in an amount of 2 to 15 parts by mass with respect to 100 parts by mass of the base resin,
The non-halogen flame retardant, the surface layer and the central portion of the flame-retardant foamed composite resin particles, the absorbance ratio in the following range:
(I) The absorbance ratio (D960/D1600) of the surface layer is 0.9 or more,
(Ii) Absorbance ratio (D960/D1600) of the central portion is 0.7 or less (the above-mentioned absorbance ratio is 960 cm ⁻¹ absorbance (D960) and 1600 cm obtained from the infrared absorption spectrum measured by ATR infrared spectroscopy). It is a ratio with respect to the absorbance (D1600) of ^-1 , where the D960 indicates the absorbance of the peak of the functional group containing phosphorus, and the D1600 indicates the absorbance of the polystyrene peak.)
The flame-retardant foamed composite resin particles are contained in the flame-retardant foamed composite resin particles. The flame-retardant expanded composite resin particles according to claim 1, wherein the polyolefin-based resin and the polystyrene-based resin are contained in an amount of 5 to 50 parts by mass and 95 to 50 parts by mass, respectively, with respect to a total of 100 parts by mass of both resins. The non-halogen flame retardant has the following general formula (I):

(In the formula, X is a phenyl group which may have a substituent, R ¹ and R ² are the same or different and are a hydrogen atom, an alkyl group, an alkoxy group or a phenyl group, and m 1 and m 2 Is an integer of 1 to 5)
The flame-retardant expanded composite resin particles according to claim 1 or 2, which is a phosphoric acid ester-based flame retardant represented by. The non-halogen flame retardant has the following structural formulas (1) to (3):

The flame-retardant expanded composite resin particle according to any one of claims 1 to 3, which is selected from the group consisting of: A foamed molded product obtained by foaming the flame-retardant foamed composite resin particles according to any one of claims 1 to 4. The foamed molded product according to claim 5, wherein the foamed molded product is a cushioning material or a packing material. A method for producing flame-retardant expanded composite resin particles according to any one of claims 1 to 4,
Composite resin particles containing a polyolefin resin and a polystyrene resin,
-In the presence of a non-halogen flame retardant, a foaming agent is impregnated to obtain expandable composite resin particles and then expanded, or-A foaming agent is impregnated to obtain expandable composite resin particles and then expanded. Then, a flame-retardant foamed composite resin particle is obtained by spreading a non-halogen flame retardant, and a method for producing the flame-retardant foamed composite resin particle.