JP2010070644A - Polyolefin resin prefoamed particles and its in-mold foam molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide flame-retardant polyolefin resin prefoamed particles which have good in-mold foam moldability, exhibits excellent flame retardance even in a sample having a higher density and a larger thickness than the conventional ones without using a halogen based flame-retardant, and does not form a harmful gas on burning. <P>SOLUTION: The polyolefin resin prefoamed particles comprise a polyolefin resin composition containing a polyolefin resin, a sterically hindered amine ether based flame-retardant, and iron oxide particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flame-retardant polyolefin-based resin pre-expanded particle used in the manufacture of electrical and electronic product parts such as a heat insulating material, a shock-absorbing packaging material, a box, a car bumper core material, and an electrical and electronic product part, and the flame retardant The present invention relates to an in-mold foam molded article obtained by in-mold foam molding of pre-expanded polyolefin resin particles.

  The in-mold foam molded article has characteristics such as arbitrary shape, lightness, and heat insulation. In particular, in-mold foam molded products made of polyolefin resin pre-expanded particles have chemical resistance, heat resistance, and strain recovery after compression compared to in-mold foam molded products obtained using polystyrene resin pre-expanded particles. Due to these features, in-mold foam molded products obtained using polyolefin resin pre-expanded particles can be used in various applications such as automotive interior parts, automotive bumper core materials, thermal insulation materials, and cushioning packaging materials. It is used.

  However, in general, a foam-molded article made of a polyolefin-based resin has the above-described excellent characteristics, but has a drawback of being easily combusted. In particular, the foamed molded article has the disadvantage that it has high combustibility compared to the non-foamed molded article and easily burns.

  In recent years, automobile parts, building materials, and electrical / electronic product parts have been required to have flame retardancy and self-extinguishing properties. In order to meet these demands, research on obtaining foam molded products with flame retardancy has been widely conducted. It is done.

  Various methods for making flame retardant polyolefin resins that are inherently flammable have been studied, and a method of adding a flame retardant is common. Various flame retardants such as halogen-containing compounds, hydrated metal oxides, phosphate esters, and nitrogen-containing compounds are used as flame retardants for polyolefin resins. Examples of the use of brominated flame retardants in polyolefin resin pre-expanded particles include Patent Documents 1 and 2, but in recent years, halogen-based flame retardants such as brominated flame retardants have a presence of halogenated gas during combustion. As there is a problem of toxic gas generation, it has been highlighted as an environmental problem, and there is a movement to regulate its use. Examples of using non-halogen flame retardants in polyolefin resin foams include Patent Documents 3 to 4, but since a large amount of flame retardant is required, in-mold foam molding using pre-expanded particles Application is difficult in case of body.

In Patent Document 5, as a non-halogen type flame retardant, by adding a sterically hindered amine ether type flame retardant to polyolefin resin pre-expanded particles, horizontal expansion of UL94 foam without causing problems such as in-mold foam moldability degradation. In-mold foam molded bodies that conform to HF-1 in the test are described in the examples. Patent Document 6 also describes an in-mold foam-molded article that is self-extinguishing in a combustion test based on FMVSS302 using the same flame retardant. The UL94 test is more rigorous than the test based on FMVSS302 in Patent Document 6, and Patent Document 5 describes the density of the in-mold foam molded product, but describes the thickness of the test sample. It has not been. The polyolefin resin-in-mold foam-molded product to which a sterically hindered amine ether type flame retardant is added is more difficult to conform to HF-1 and HF-2 in the horizontal test of UL94 foam when the density is higher or the thickness is thicker. Become. Even when this sterically hindered amine ether type flame retardant is used, further improvement in flame retardant performance is desired.
JP 2002-128933 A JP-A-10-147661 JP 7-258447 A JP 11-322990 A WO2003 / 048239 JP 2004-263033 A

  The object of the present invention is to exhibit excellent flame retardancy even in samples having a higher density and thickness than before without using a halogen-based flame retardant, while having good in-mold foam moldability, and at the time of combustion An object of the present invention is to provide pre-expanded particles of flame retardant polyolefin resin that do not generate harmful gas.

  As a result of diligent research in view of the above problems, the present invention uses a polyolefin resin pre-foamed particle obtained by adding a sterically hindered amine ether flame retardant and iron oxide particles to a polyolefin resin, thereby achieving good in-mold foam molding. It has been found that the flame retardancy is superior to the conventional one, specifically, high-density in-mold foam moldings and thick in-mold foam moldings. It was.

  That is, the present invention relates to polyolefin resin pre-expanded particles comprising a polyolefin resin composition containing a polyolefin resin, a sterically hindered amine ether flame retardant, and iron oxide particles.

As a preferred embodiment,
[1] The sterically hindered amine ether flame retardant is represented by the general formula (1):
R ¹ NHCH ₂ CH ₂ CH ₂ NR ² CH ₂ CH ₂ NR ³ CH ₂ CH ₂ CH ₂ NHR ⁴ (1)

（式（１）中、Ｒ¹およびＲ²と、Ｒ³およびＲ⁴の一方は一般式（２）で表わされるｓ−トリアジン部分Ｔ、Ｒ³およびＲ⁴の他方は水素原子、式（２）中、Ｒ⁵は１〜１２個の炭素原子を有するアルキル基、Ｒ⁶はメチル基、シクロヘキシル基またはオクチル基）で表わされる化合物、酸化鉄が黒色の酸化鉄である、
〔２〕ポリオレフィン系樹脂１００重量部に対し、立体障害性アミンエーテル系難燃剤０．１重量部以上２０重量部以下および酸化鉄粒子１重量部以上１５重量部以下を含有するポリオレフィン系樹脂組成物からなる、
〔３〕前記ポリオレフィン系樹脂がポリプロピレン系樹脂である、
前記記載のポリオレフィン系樹脂予備発泡粒子に関する。

(In the formula (1), ^one of R ¹ and R ² and R ³ and R ⁴ is the s-triazine moiety T represented by the general formula (2), the other of R ³ and R ⁴ is a hydrogen atom, and the formula (2 ), Wherein R ⁵ is an alkyl group having 1 to 12 carbon atoms, R ⁶ is a methyl group, a cyclohexyl group or an octyl group), and the iron oxide is black iron oxide,
[2] A polyolefin resin composition containing 0.1 to 20 parts by weight of a sterically hindered amine ether flame retardant and 1 to 15 parts by weight of iron oxide particles with respect to 100 parts by weight of a polyolefin resin. Consist of,
[3] The polyolefin resin is a polypropylene resin.
It relates to the polyolefin resin pre-expanded particles described above.

  The second aspect of the present invention relates to an in-mold foam molded product obtained by in-mold foam molding of the polyolefin resin pre-expanded particles described above.

  With the polyolefin resin pre-expanded particles of the present invention, in-mold foaming has excellent in-mold foaming moldability, surface appearance, and excellent flame retardancy even in samples with higher density or thickness than conventional ones. A molded body can be obtained.

  The polyolefin resin used in the present invention is a polymer comprising 75% by weight or more and 100% by weight of an olefin monomer, and is a homopolymer or a copolymer. The olefin monomer is preferably 80% by weight or more and 100% by weight or less. Another monomer having copolymerizability with the olefin monomer may be contained in an amount of 25% by weight or less, preferably 0% by weight or more and 20% by weight or less.

  Specific examples of the olefin monomer include, for example, ethylene, propylene, butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexene-1, 4-methyl-pentene-1, 3,4. Examples thereof include α-olefins having 2 to 12 carbon atoms such as dimethyl-butene-1, heptene-1, 3-methyl-hexene-1, octene-1, and decene-1. These may be used alone or in combination of two or more.

  Specific examples of other monomers copolymerizable with the olefinic monomer include, for example, cyclopentene, norbornene, 1,4,5,8-dimethano-1,2,3,4,4a. , 8,8a, 6-octahydronaphthalene and the like, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1 , 6-octadiene and the like. These may be used alone or in combination of two or more.

  Specific examples of the olefin resin comprising the olefin monomer and other monomers copolymerizable with the olefin monomer as described above include, for example, high density polyethylene, medium density polyethylene, low density Polyethylene resin mainly composed of ethylene such as polyethylene and linear low density polyethylene; propylene homopolymer, for example, ethylene-propylene copolymer having ethylene content of 1 to 15% by weight, for example, butene content of 1 Polypropylene resins mainly composed of propylene such as propylene-butene copolymer, ethylene-propylene-butene copolymer, ethylene-propylene-diene copolymer of ˜15% by weight; polybutene, polypentene and the like. Among these, polyethylene resins such as low density polyethylene and linear low density polyethylene, ethylene-propylene random copolymers having an ethylene content of 1 to 15% by weight, and propylene having a butene content of 1 to 15% by weight A polypropylene resin such as a butene random copolymer and an ethylene-propylene-butene copolymer having a propylene content of 85 to 99% by weight can easily obtain pre-expanded particles having a uniform and independent cell structure. Preferably, a polypropylene resin is more preferable, in particular, an ethylene-propylene random copolymer having an ethylene content of 1 to 15% by weight, a propylene-butene random copolymer having a butene content of 1 to 15% by weight, Ethylene-propylene-butene copolymer with a propylene content of 85-99% by weight Coalescence is preferable. These polyolefin resins may be used alone or in combination of two or more.

  The polyolefin resin is preferably non-crosslinked from the viewpoints of cost, recycling, and simplification of the process, but may be crosslinked or degraded by peroxide or radiation.

  The polyolefin resin of the present invention preferably has a melt flow rate (hereinafter sometimes referred to as MFR) of 0.1 g / 10 min to 50 g / 10 min, and more preferably 0.3 g / 10 min to 40 g / 10 min. The following are preferred. If the MFR of the polyolefin resin is less than 0.1 g / 10 min, the fluidity at the time of foaming of the polyolefin resin tends to be unsatisfactory and foaming tends to be difficult. If it exceeds 50 g / 10 minutes, the polyolefin resin, on the other hand, exhibits an excessively high fluidity and becomes highly difficult to foam, and the polyolefin resin pre-expanded particles obtained tend to shrink easily after foaming.

  For the polyolefin resin, other thermoplastic resins that can be used by mixing with the polyolefin resin as necessary, for example, polystyrene, ionomer, etc. are used in combination as long as the properties of the polyolefin resin are not lost. May be.

Preferred examples of the sterically hindered amine ether flame retardant in the present invention include, for example, the general formula (1):
R ¹ NHCH ₂ CH ₂ CH ₂ NR ² CH ₂ CH ₂ NR ³ CH ₂ CH ₂ CH ₂ NHR ⁴ (1)
(In the formula (1), ^one of R ¹ and R ² and R ³ and R ⁴ is the s-triazine moiety T represented by the general formula (2), the other of R ³ and R ⁴ is a hydrogen atom, and the formula (2 R ⁵ is, for example, methyl group, ethyl group, propyl group, butyl group, n-pentyl group, n-hexyl group, n-heptyl group, nonyl group, decyl group, undecyl group, dodecyl group, isopropyl group, Isobutyl group, second butyl group, third butyl group, 2-ethylbutyl group, isopentyl group, 1-methylpentyl group, 1,3-dimethylbutyl group, 1-methylhexyl group, isoheptyl group, 1,1,3, An alkyl group having 1 to 12 carbon atoms such as 3-tetramethylpentyl group, 1-methylundecyl group, 1,1,3,3,5,5-hexamethylhexyl group, R ⁶ is a methyl group, Cyclohexyl or octyl Compounds represented by Le group). The sterically hindered amine ether flame retardant may be used alone or in combination of two or more.

前記一般式（２）で表わされるｓ−トリアジン部分Ｔの具体例としては、たとえば２，４−ビス［（１−メトキシ−２，２，６，６−テトラメチルピペリジン−４−イル）ｎ−ブチルアミノ］−ｓ−トリアジン、２，４−ビス［（１−シクロヘキシルオキシ−２，２，６，６−テトラメチルピペリジン−４−イル）ｎ−ブチルアミノ］−ｓ−トリアジン、２，４−ビス［（１−オクチルオキシ−２，２，６，６−テトラメチルピペリジン−４−イル）ｎ−ブチルアミノ］−ｓ−トリアジンなどがあげられる。

Specific examples of the s-triazine moiety T represented by the general formula (2) include 2,4-bis [(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl) n- Butylamino] -s-triazine, 2,4-bis [(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine, 2,4- And bis [(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine.

  Specific examples of the sterically hindered amine ether flame retardant represented by the general formula (1) include, for example, N, N ′, N ′ ″-tris {2,4-bis [(1-cyclohexyloxy-2, 2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazin-6-yl} -3,3′-ethylenediiminopropylamine; N, N ′, N ″ -tris {2,4-Bis [(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine-6yl} -3,3′-ethylenedi Iminodipropylamine; N, N ′, N ′ ″-tris {2,4-bis [(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -S-triazine-6yl} -3,3'-ethylene Diiminodipropylamine; N, N ′, N ″ -tris {2,4-bis [(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -S-triazin-6yl} -3,3'-ethylenediiminopropylamine; N, N ', N' ''-tris {2,4-bis [(1-methoxy-2,2,6,6 -Tetramethylpiperidin-4-yl) n-butylamino] -s-triazine-6yl} -3,3′-ethylenediiminopropylamine; N, N ′, N ″ -tris {2,4-bis [(1-Methoxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine-6yl} -3,3′-ethylenediiminopropylamine . These may be used alone or in combination of two or more.

  The blending ratio of the polyolefin resin and the sterically hindered amine ether flame retardant is preferably 0.1 parts by weight or more and 20 parts by weight with respect to 100 parts by weight of the polyolefin resin. Hereinafter, more preferably 1 part by weight or more and 10 parts by weight or less is used. When the blending ratio of the flame retardant is less than 0.1 parts by weight, it is difficult to obtain sufficient flame retardancy, and when it exceeds 20 parts by weight, the cell diameter tends to become finer and in-mold foam moldability, In particular, not only does the surface appearance tend to deteriorate, but the cost tends to be high, which tends to be economically disadvantageous.

  Even if the method of adding the sterically hindered amine ether flame retardant to the polyolefin resin is a direct addition method, the polyolefin comprising the sterically hindered amine ether flame retardant, for example, 5 wt% to 50 wt% A method of preparing a resin-based resin masterbatch and adding the polyolefin-based resin masterbatch to the polyolefin-based resin may be used, but the latter method is preferable from the viewpoint of ease of addition.

Examples of the iron oxide used in the present invention include α-FeOOH, α-Fe ₂ O ₃ , FeO, and Fe ₃ O ₄ , and more preferably black iron oxide such as FeO and Fe ₃ O ₄ . More preferably, it contains Fe ₃ O ₄ (x: y = 1: 1) represented by (FeO) _x (Fe ₂ O ₃ ) _y as a main component. The black iron oxide may contain other iron oxide components such as Fe ₂ O ₃ as long as the black color is not impaired, and a part of the iron may be other metals such as Mn, Zn, Mg. It may be replaced. Moreover, it may be naturally produced or synthesized, and as an example, a commercially available iron black with a common name can be used.

  The particle size of the iron oxide particles is preferably 0.05 μm or more and 1 μm or less, more preferably 0.1 μm or more and 0.8 μm or less.

  The addition amount of the iron oxide particles is preferably 1 part by weight or more and 15 parts by weight or less, and more preferably 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. In the case of less than 1 part by weight, there is a possibility that the flame retardant effect is not seen. When the amount exceeds 15 parts by weight, the specific gravity of iron oxide is heavy. Therefore, in the method in which polyolefin resin particles are dispersed in a dispersion medium in a closed container and foamed, the polyolefin resin usually floating in the dispersion medium is used. Particles may sink and manufacturing may be difficult.

  Even if the method of adding the iron oxide particles to the polyolefin resin is a direct addition method, a polyolefin resin master batch in which the iron oxide particles are 10 wt% or more and 80 wt% or less is prepared, and the polyolefin resin master A method of adding a batch to a polyolefin resin may be used, but the latter method is preferable from the viewpoint of dispersibility of iron oxide particles, ease of addition, and the like.

  In the present invention, if necessary, cell nucleating agents such as talc, antioxidants, metal deactivators, phosphorus processing stabilizers, UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, etc. A polyolefin resin composition by adding a stabilizer or a crosslinking agent, a chain transfer agent, a lubricant, a plasticizer, a filler, a reinforcing agent, a flame retardant, an antistatic agent, etc. to the polyolefin resin within a range not impairing the effects of the present invention. It is good also as a thing.

  The polyolefin-based resin composition is usually melted in advance using an extruder, kneader, Banbury mixer, roll or the like so as to be easily used for preliminary foaming, and has a cylindrical shape, an elliptical shape, a spherical shape, a cubic shape, a rectangular parallelepiped shape, etc. In such a desired particle shape, the resin is molded into polyolefin resin particles such that the average particle weight of the particles is preferably 0.5 mg to 3.0 mg, more preferably 0.5 mg to 2.0 mg. . Surfactant-type or polymer-type antistatic agents, flame retardant improvers, conductivity improvers, etc., which are added as necessary, such as surfactants, are usually added to the molten resin in the production process of polyolefin resin particles. preferable.

  The polyolefin resin particles can be made into flame-retardant polyolefin resin pre-expanded particles using a conventionally known method. For example, polyolefin resin particles are dispersed in a dispersion medium in a closed container, and after adding a foaming agent, the temperature is higher than the temperature at which the polyolefin resin particles are softened, preferably the melting point of the polyolefin resin particles is −25 ° C. or higher. The melting point of the resin + 25 ° C. or lower, more preferably the temperature of the polyolefin resin particles −15 ° C. or higher and the temperature of the polyolefin resin particles + 15 ° C. or lower is heated and pressurized to impregnate the polyolefin resin particles with the foaming agent. Thereafter, one end of the sealed container is opened, and the polyolefin resin particles are released into an atmosphere at a lower pressure than in the sealed container, whereby the flame-retardant polyolefin resin pre-expanded particles can be produced.

  There are no particular limitations on the sealed container in which the polyolefin resin particles are dispersed, and any container that can withstand the pressure in the container and the temperature in the container during the production of the pre-foamed particles may be used, and examples include an autoclave container.

  As the dispersion medium, methanol, ethanol, ethylene glycol, glycerin, water, and the like can be used, and it is preferable to use water among them.

  In order to prevent coalescence of the polyolefin resin particles in the dispersion medium, it is preferable to use a dispersant. Examples of the dispersant include inorganic dispersants such as tricalcium phosphate, magnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, and clay.

  As necessary, for example, sodium dodecylbenzenesulfonate, sodium n-paraffin sulfonate, sodium α-olefin sulfonate, magnesium sulfate, magnesium nitrate, magnesium chloride, aluminum sulfate, aluminum nitrate, aluminum chloride, iron sulfate, iron nitrate It is preferable to use a dispersion aid such as iron chloride in combination.

  Among these, combined use of tricalcium phosphate and sodium n-paraffin sulfonate is more preferable. The amount of the dispersant or dispersion aid used varies depending on the type and type and amount of polyolefin resin used, but usually 0.2 to 3 parts by weight of the dispersant is blended with 100 parts by weight of the dispersion medium. It is preferable to add 0.001 to 0.1 parts by weight of a dispersion aid. The polyolefin resin particles are usually preferably used in an amount of 20 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the dispersion medium in order to improve the dispersibility in the dispersion medium.

  In producing the flame-retardant polyolefin resin pre-expanded particles, the blowing agent is not particularly limited. For example, aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane; air, nitrogen, carbon dioxide, etc. Inorganic gas; water and the like and mixtures thereof can be used.

  When water is used as a foaming agent, it is preferable to add one or more compounds among the hydrophilic polymer and the compound having a triazine skeleton to the polyolefin resin in order to obtain polyolefin resin pre-expanded particles having a high expansion ratio. . Here, as the hydrophilic polymer, an ethylene-acrylic acid-maleic anhydride terpolymer, an ethylene- (meth) acrylic acid copolymer, and an ionomer obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with a metal ion. Examples thereof include carboxyl group-containing polymers such as resins, polyethylene glycol and the like. These may be used alone or in combination of two or more. In particular, an ethylene ionomer resin or polyethylene glycol obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with an alkali metal ion such as sodium ion or potassium ion is preferable because it provides a good water content and good foamability. . Furthermore, an ethylene ionomer resin obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with potassium ions and a polyethylene glycol having a molecular weight of 300 to 10,000 are preferable because they give a larger average cell diameter.

  The amount of the hydrophilic polymer used is not particularly limited depending on the kind of the hydrophilic polymer, but is usually 0.01 parts by weight or more and 20 parts by weight or less, preferably 0.1 parts by weight with respect to 100 parts by weight of the polyolefin resin. More preferred is 5 parts by weight or more. If the amount is less than 0.01 part by weight, the polyolefin resin pre-expanded particles having a high expansion ratio tend to be difficult to obtain, and if the amount exceeds 20 parts by weight, the heat resistance and the mechanical strength may decrease significantly.

  The compound having a triazine skeleton that can be used in the present invention preferably has a molecular weight per unit triazine skeleton of 300 or less. Here, the molecular weight per unit triazine skeleton is a value obtained by dividing the molecular weight by the number of triazine skeletons contained in one molecule. When the molecular weight per unit triazine skeleton exceeds 300, variation in foaming ratio and variation in cell diameter may be noticeable. Examples of the compound having a molecular weight per unit triazine skeleton of 300 or less include melamine (chemical name 1,3,5-triazine-2,4,6-triamine), ammelin (1,3,5-triazine-2- Hydroxy-4,6-diamine), ammelide (1,3,5-triazine-2,4-hydroxy-6-amine), cyanuric acid (1,3,5-triazine-2,4,6-triol) ), Tris (methyl) cyanurate, tris (ethyl) cyanurate, tris (butyl) cyanurate, tris (2-hydroxyethyl) cyanurate, melamine isocyanuric acid condensate and the like. These may be used alone or in combination of two or more. Among these, it is preferable to use melamine, isocyanuric acid, and melamine / isocyanuric acid condensate in order to obtain pre-expanded particles having a high expansion ratio with small variations in expansion ratio and cell diameter.

  The expansion ratio of the polyolefin resin pre-expanded particles obtained by the above production method is preferably 5 to 50 times, and more preferably 7 to 45 times.

  Moreover, once the pre-expanded particles of 5 times to 35 times are manufactured, the pressure in the pre-expanded particles is made higher than the normal pressure by pressurizing the pre-expanded particles in a sealed container and impregnating with nitrogen, air, etc. Then, the foamed particles may be heated by steam or the like to obtain two-stage foamed pre-foamed particles 50 times or more by a method such as a two-stage foaming method for further foaming.

The expansion ratio here refers to the weight w (g) and ethanol submerged volume v (cm ³ ) of the polyolefin resin pre-expanded particles, and the density d (g / cm ³ ) of the polyolefin resin particles before foaming It is obtained by the formula.
Foaming ratio = d × v / w

  The polyolefin resin pre-expanded particles of the present invention have two melting peaks as measured by the differential scanning calorimetry method, and are calculated from the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side among the melting peaks. The ratio Qh / (Ql + Qh) × 100 (hereinafter referred to as DSC ratio) of the melting peak on the high temperature side is preferably 10% or more and 50% or less, more preferably 16% or more and 40% or less. . When the DSC ratio is within the above range, an in-mold foam molded product having a high surface beauty is easily obtained.

  When the polyolefin resin pre-foamed particles of the present invention are used for in-mold foam molding, a) a method of using as it is, b) a method of previously injecting an inorganic gas such as air into the pre-foamed particles to impart foaming ability, C) A conventionally known method such as a method in which pre-expanded particles are filled in a mold in a compressed state and molded may be used.

  As a method of molding an in-mold foam molded body from the polyolefin resin pre-foamed particles of the present invention, for example, the pre-foamed particles are preliminarily air-pressed in a pressure-resistant container, and the foaming ability is increased by press-fitting air into the pre-foamed particles. A mold that can be closed but cannot be sealed, and is heated for about 3 to 30 seconds with a water vapor pressure of about 0.10 to 0.4 MPa (G) using water vapor or the like as a heating medium. Then, the polyolefin resin pre-expanded particles are fused together, and then the mold is cooled by water cooling to such an extent that the deformation of the in-mold foam molded article after taking out the in-mold foam molded article can be suppressed. Examples of the method include opening and obtaining an in-mold foam molded article.

The density of the in-mold foam molded article obtained using the polyolefin resin pre-expanded particles of the present invention is preferably 10 kg / m ³ or more and 300 kg / m ³ or less, more preferably 15 kg / m ³ or more and 250 kg / m. ³ or less.

  Next, the measuring method of MFR, melting | fusing point, and DSC ratio in this invention is demonstrated.

  MFR is measured using the MFR measuring instrument described in JIS-K7210 under the conditions of orifice 2.0959 ± 0.005 mmφ, orifice length 8.000 ± 0.025 mm, load 2160 g, 230 ± 0.2 ° C. Is the value of

  The melting point is 5 to 6 mg of the sample is heated from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter, and then the polyolefin resin particles are melted, and then at 10 ° C./min. From the DSC curve obtained when the temperature is increased from 40 ° C. to 220 ° C. at 10 ° C./min after crystallization by lowering the temperature from 220 ° C. to 40 ° C., the melting peak temperature at the second temperature increase This is the required value.

  The DSC ratio is a melting curve (shown in FIG. 1) obtained by heating 5 to 6 mg of polyolefin resin pre-expanded particles from 40 ° C. to 220 ° C. at a rate of 10 ° C./min using a differential scanning calorimeter. In the example), it has two peaks, and the ratio Qh / (Ql + Qh) × 100 of the melting peak on the high temperature side calculated from the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side among the melting peaks It is a parameter represented by

  Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited only to these examples. Evaluation was performed as follows.

(DSC ratio)
In a melting curve (illustrated in FIG. 1) obtained when a polyolefin resin pre-expanded particle 5-6 mg is heated from 40 ° C. to 220 ° C. at a temperature rising rate of 10 ° C./min using a differential scanning calorimeter, Two melting peaks were calculated from the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side of the melting peak by the following equation.
DSC ratio = Qh / (Ql + Qh) × 100

(Foaming ratio)
The weight w (g) and the ethanol submerged volume v (cm ³ ) of the polyolefin resin pre-expanded particles are obtained, and are obtained by the following formula from the density d (g / cm ³ ) of the polyolefin resin particles before foaming.
Foaming ratio = d × v / w

(Average cell diameter)
Thirty pre-expanded particles were arbitrarily taken out from the obtained polyolefin-based resin pre-expanded particles, the cell diameter was measured according to JIS K6402, and the average cell diameter was calculated.

(Closed cell rate)
Obtain the closed cell volume of the polyolefin resin pre-expanded particles obtained using an air comparison hydrometer (Model 930 manufactured by BECKMAN), and divide the closed cell volume by the apparent volume obtained separately by the ethanol immersion method. Was used to calculate the closed cell ratio.

(Surface appearance)
The surface of the in-mold foamed product is visually observed and evaluated according to the following criteria.
○: There are no irregularities on the surface and there are almost no gaps between the particles. ×: There are irregularities on the surface, and the gaps between the particles are extremely large.

(Fusion)
The in-mold foam molded body is broken, its cross section is observed, the ratio of the number of broken particles to the total number of particles in the cross section is determined, and evaluated according to the following criteria.
○: Breaking particle ratio is 60% or more ×: Breaking particle ratio is less than 60%

(Molded body density)
The obtained in-mold foam molded product was cut to a target value of 150 mm in length, 50 mm in width, and thickness as a sample for combustion test, and volume v (cm ³ ) from the length of weight w (g), length, width, and thickness. Is obtained by the following equation.
Molded body density = w / v (g / cm ³ )

(Flame retardance evaluation)
A test based on UL94HF is performed and evaluated according to the following criteria. One type of polyolefin resin pre-expanded particles were tested at thicknesses of 3.5, 7, and 13 mm.
Residual flame time: This is the time from when the flame of the gas burner disappears until the flame of the sample piece disappears, and the average value was calculated when five tests were performed. The shorter the time, the higher the flame retardant performance.

(Examples 1-6)
0.01 parts by weight of talc as a nucleating agent for 100 parts by weight of polyolefin resin (ethylene-propylene random copolymer, ethylene content 2.8%, MFR = 6.0 g / 10 min, melting point 145 ° C.) Iron oxide (iron black, 40% masterbatch) and chemical formula (3) in the ratio shown in 1:
RNHCH ₂ CH ₂ CH ₂ NRCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ NHR (3)

（式中、Ｒは化学式（４）で表されるｓ−トリアジン部分Ｔ）の化合物（商品名：ＦＬＡＭＥＳＴＡＢ ＮＯＲ１１６、チバ社製）を添加・混合し、５０ｍｍφ単軸押出機で混練したのち造粒し、ポリオレフィン系樹脂粒子（１．２ｍｇ／粒）を製造した。

(Wherein R is a s-triazine moiety T represented by the chemical formula (4)) (trade name: FLAMESTTAB NOR116, manufactured by Ciba), mixed, kneaded in a 50 mmφ single screw extruder and granulated Then, polyolefin resin particles (1.2 mg / grain) were produced.

  100 parts by weight of the resin particles and 10 parts by weight of isobutane together with a dispersion medium (300 parts by weight of water containing 1.6 parts by weight of powdery basic tribasic calcium phosphate and 0.03 parts by weight of sodium n-paraffin sulfonate) The container was charged and the inside of the container was heated to the foaming temperature shown in Table 1. Next, the pressure inside the container was adjusted to a predetermined foaming pressure (described in Table 1) by injecting isobutane. After that, while maintaining the internal pressure of the container with nitrogen, the valve at the bottom of the pressure-resistant container is opened, and the aqueous dispersion is discharged under atmospheric pressure through an orifice plate having an aperture diameter of 4.0 mmφ. Got. Said evaluation was performed about the obtained polyolefin resin pre-expanded particle. The results are shown in Table 2.

  Next, pre-expanded polyolefin-based resin particles that have been pressurized with air in a pressure-resistant container to give an internal pressure of 0.18 to 0.23 MPa are filled in a 400 mm × 300 mm × 22 mm mold, and the pre-expanded particles are 0.28 MPa in pressure. Heating and fusing for 10 seconds with the water vapor of (G), a polyolefin resin in-mold foam molded article was obtained. With respect to the obtained in-mold foamed molded product, the surface appearance, the fusion rate, the molded product magnification, and the combustion test were evaluated. The results are shown in Table 2.

(Comparative Examples 1-2)
Iron oxide (iron black, 40% masterbatch) and the compound of formula (3) were added at the ratios shown in Table 1, and polyolefin resin pre-foamed particles and in-mold foam molded bodies were produced in the same manner as in the examples. And evaluated.

It is an example of a melting curve obtained when a polyolefin resin pre-expanded particle according to the present invention is measured using a differential scanning calorimeter. The horizontal axis is the temperature, and the vertical axis is the endothermic amount. The shaded portion on the low temperature side is Ql, and the shaded portion on the high temperature side is Qh.

Claims (5)

  Polyolefin resin pre-expanded particles comprising a polyolefin resin composition comprising a polyolefin resin, a sterically hindered amine ether flame retardant and iron oxide particles. The sterically hindered amine ether flame retardant is represented by the general formula (1):
R ¹ NHCH ₂ CH ₂ CH ₂ NR ² CH ₂ CH ₂ NR ³ CH ₂ CH ₂ CH ₂ NHR ⁴ (1)

(In the formula (1), ^one of R ¹ and R ² and R ³ and R ⁴ is the s-triazine moiety T represented by the general formula (2), the other of R ³ and R ⁴ is a hydrogen atom, and the formula (2 2) R ⁵ is an alkyl group having 1 to 12 carbon atoms, R ⁶ is a methyl group, a cyclohexyl group or an octyl group), and the iron oxide is black iron oxide -Based resin pre-expanded particles.   A polyolefin resin composition comprising 0.1 to 20 parts by weight of a sterically hindered amine ether flame retardant and 1 to 15 parts by weight of iron oxide particles with respect to 100 parts by weight of a polyolefin resin. Item 3. The polyolefin resin pre-expanded particle according to Item 1 or 2.   The polyolefin resin pre-expanded particles according to any one of claims 1 to 3, wherein the polyolefin resin is a polypropylene resin.   An in-mold foam-molded article obtained by in-mold foam-molding the polyolefin resin pre-expanded particles according to any one of claims 1 to 4.

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