JP2004018596A - Thermoplastic cross-linked foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic resin cross-linked foam which has excellent flame retardancy, does not cause a dripping phenomenon, when burned, is not deformed before and after burned, has excellent dynamic physical properties, heat resistance, flexibility, impact absorptivity, heat insulating property, dimensional stability, and the like, and has a low linear expansion coefficient. <P>SOLUTION: This thermoplastic resin cross-linked foam is characterized by comprising a foamable thermoplastic resin composition comprising 100 pts. wt. of a thermoplastic resin, 10 to 70 pts. wt. of a philosilicate and a foaming agent and having a gel fraction of 15 to 70 wt. % and an apparent density of 0.03 to 0.1 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１１】
表１から明らかなように、本発明による実施例１の架橋発泡体は、難燃性試験のＵＬ９４ＨＢＦ法およびＵＬ９４ＨＢ法のいずれにも合格しており、優れた難燃性を発現した。また、本発明による実施例２〜実施例７の架橋発泡体は、いずれも難燃性試験のＵＬ９４ＨＢＦ法に合格しており、優れた難燃性を発現した。
【０１１２】
これに対し、熱可塑性樹脂（エチレン−酢酸ビニル共重合体）１００重量部に対する層状珪酸塩（膨潤性フッ素マイカ）の配合量が１０重量部未満（５重量部）であった比較例１の架橋発泡体は、難燃性試験のＵＬ９４ＨＢＦ法およびＵＬ９４ＨＢ法のいずれにも不合格であり、難燃性が悪かった。また、熱可塑性樹脂（エチレン−酢酸ビニル共重合体）１００重量部に対する層状珪酸塩（モンモリロナイト）の配合量が１０重量部未満（５重量部）であった比較例２の架橋発泡体、見掛け密度が０．１ｇ／ｃｍ^３を超えていた（０．１６７ｇ／ｃｍ^３）比較例３の架橋発泡体、見掛け密度が０．０３ｇ／ｃｍ^３未満（０．０２９ｇ／ｃｍ^３）であった比較例４の架橋発泡体および層状珪酸塩を配合しなかった比較例５の架橋発泡体は、いずれも難燃性試験のＵＬ９４ＨＢＦ法に不合格であり、難燃性が悪かった。さらに、熱可塑性樹脂（エチレン−酢酸ビニル共重合体）１００重量部に対する層状珪酸塩（膨潤性フッ素マイカ）の配合量が７０重量部を超えていた（８０重量部）発泡性組成物を用いた比較例６については、良好な架橋発泡体を得られなかったので、難燃性の評価ができなかった。
【０１１３】
【発明の効果】
以上述べたように、本発明の架橋発泡体は、難燃性に優れ、燃焼時におけるドリップ現象の発生や燃焼前後の形状変化が少なく、しかも力学的物性、耐熱性、柔軟性、衝撃吸収性、断熱性、寸法安定性等に優れ、線膨張率が低い等の優れた諸性能を兼備するものであり、例えば、天井、ドア、計器パネルなどの車両内装材や緩衝材あるいは断熱材等を始め、各種工業用途に好適に用いられる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crosslinked thermoplastic resin foam.
[0002]
[Prior art]
Normally, thermoplastic resin burns while melting and vaporizing during its combustion. During combustion, a phenomenon in which low-molecular-weight liquid hydrocarbons produced by the thermal decomposition of the thermoplastic resin drop (drip) Phenomenon) occurs.
[0003]
The drip phenomenon is caused by a molded article using a flame-retardant thermoplastic resin such as a halogen-containing thermoplastic resin or a nitrogen-containing thermoplastic resin as a main raw material, a halogen-based flame retardant, a phosphorus-based flame retardant, and a metal hydroxide-based flame retardant. The same applies to molded products using flame-retardant thermoplastics with flame retardants such as flame retardants added as main raw materials, and it is difficult for molded products made from thermoplastics to maintain the shape before combustion. It is.
[0004]
The drip phenomenon also occurs in a foam using a thermoplastic resin as a main raw material, and the change in shape before and after combustion is more remarkable in a foam than in a non-foamed molded body.
[0005]
Many of the currently mainstream thermoplastic resin foams have an apparent density of 0.025 to 0.2 g / cm. ³ Because the amount of thermoplastic resin per unit volume is very small, once ignited, the thermoplastic resin rapidly pyrolyzes and burns, destroying the foam structure required to maintain the shape of the foam before burning Will be done.
[0006]
In general, thermoplastic resin foams are excellent in flexibility, shock absorption, heat insulation, and the like, and are therefore widely used as, for example, vehicle interior materials such as ceilings, doors, and instrument panels, and cushioning materials. Moreover, the polyolefin resin foam which is a closed cell has many uses as a heat insulating material. However, these thermoplastic resin foams have a problem that they are very weak against thermal deformation due to flames, and even foams with high flame retardancy and high self-extinguishing properties need to be self-extinguishing. There is a problem that thermal deformation is remarkable.
[0007]
On the other hand, in order to improve mechanical properties such as mechanical strength of the thermoplastic resin foam, shock absorption, heat insulation, dimensional stability, etc., and to reduce the coefficient of linear expansion, inorganic A filler is included. For example, Japanese Patent Application Laid-Open No. H8-143697 discloses a polypropylene foam containing a clay compound and / or diatomaceous earth to which a blowing agent and a silane coupling agent are adsorbed. A body composition is disclosed.
[0008]
The polypropylene foam composition disclosed in the above publication, by kneading a clay compound or diatomaceous earth with polypropylene, mechanical properties such as mechanical strength of the foam, shock absorption, heat insulation, dimensional stability and the like. It is said that it can be improved or the coefficient of linear expansion can be reduced.
[0009]
However, the polypropylene foam composition disclosed in the above publication does not consider dispersing the aggregate structure of the clay compound or diatomaceous earth to uniformly disperse the flaky crystals in the polypropylene. It is hard to say that the effect of including a compound or diatomaceous earth has been sufficiently brought out. That is, it cannot be said that the polypropylene foam composition disclosed in the above publication can sufficiently suppress the occurrence of a drip phenomenon at the time of combustion, a change in the shape of the foam before and after combustion, and the like.
[0010]
[Problems to be solved by the invention]
In view of the above problems, an object of the present invention is to provide excellent flame retardancy, less drip phenomenon during combustion and little change in shape before and after combustion, and furthermore, mechanical properties, heat resistance, flexibility, shock absorption, and heat insulation. An object of the present invention is to provide a thermoplastic resin crosslinked foam having excellent properties and dimensional stability and a low coefficient of linear expansion.
[0011]
[Means for Solving the Problems]
The crosslinked thermoplastic resin foam according to the invention (invention) according to claim 1 is a foamable thermoplastic resin obtained by mixing 10 to 70 parts by weight of a layered silicate and a blowing agent with respect to 100 parts by weight of a thermoplastic resin. The composition has a gel fraction of 15 to 70% by weight and an apparent density of 0.03 to 0.1 g / cm. ³ It is characterized by being.
[0012]
The heat used in the foamable thermoplastic resin composition (hereinafter, simply abbreviated as “foamable composition”) constituting the thermoplastic resin crosslinked foam (hereinafter, simply abbreviated as “crosslinked foam”) of the present invention. Examples of the plastic resin include, but are not particularly limited to, polyolefin resins, polystyrene resins, polyphenylene ether resins, polyoxymethylene resins, polyester resins, polyamide resins, and the like. A system resin is preferably used. These thermoplastic resins may be used alone or in combination of two or more.
[0013]
The above-mentioned polyolefin-based resin is not particularly limited. For example, a homopolymer of propylene, a copolymer of propylene and an α-olefin other than propylene, a random copolymer of propylene and ethylene, or a block copolymer of propylene and ethylene. A polymer, a homopolymer of ethylene, a copolymer of ethylene and an α-olefin other than ethylene, a copolymer of ethylene and (meth) acrylic acid, a copolymer of ethylene and (meth) acrylate, Copolymers of ethylene and vinyl acetate, copolymers of ethylene and styrene, homopolymers of butene, homopolymers or copolymers of conjugated dienes such as isoprene and butadiene, among which propylene Homopolymer, copolymer of propylene and α-olefin other than propylene, homopolymer of ethylene, ethylene Copolymers of other α- olefins styrene, a copolymer of ethylene and ethyl acrylate, a copolymer of ethylene and vinyl acetate is preferably used. These polyolefin resins may be used alone or in combination of two or more. In the present invention, for example, (meth) acryl means acryl or methacryl.
[0014]
The above-mentioned polyolefin-based resin is not particularly limited, but conforms to the method A of JIS K-7210 “Test method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of plastic-thermoplastic”. It is preferable that the melt mass flow rate (MFR) measured in the above is 0.2 to 10 g / 10 minutes. When the MFR of the polyolefin resin is less than 0.2 g / 10 min, the appearance of the surface of the obtained cross-linked foam may be deteriorated, and when the MFR of the polyolefin resin exceeds 10 g / 10 min, In addition, the heat resistance of the obtained crosslinked foam may be insufficient.
[0015]
In the present invention, when a crosslinked foam having excellent flexibility is desired, a copolymer of ethylene and (meth) acrylic acid or a copolymer of ethylene and (meth) acrylate is used as the thermoplastic resin. Alternatively, it is preferable to use a copolymer of ethylene and vinyl acetate. At this time, the content of (meth) acrylic acid, (meth) acrylic acid ester or vinyl acetate in the copolymer is not particularly limited, but is preferably 0.1 to 50% by weight, More preferably, it is 5 to 30% by weight. If the content of (meth) acrylic acid, (meth) acrylic acid ester or vinyl acetate in the copolymer is less than 0.1% by weight, the obtained crosslinked foam may have poor flexibility, When the content of (meth) acrylic acid, (meth) acrylate or vinyl acetate in the copolymer exceeds 50% by weight, the heat resistance of the resulting crosslinked foam may be insufficient.
[0016]
In the present invention, when a crosslinked foam excellent in balance between flexibility and mechanical properties is desired, it is preferable to use a copolymer of ethylene and an α-olefin other than ethylene as the thermoplastic resin. By increasing the copolymerization ratio of α-olefins other than ethylene, the copolymer becomes rich in flexibility, and conversely, by lowering the copolymerization ratio of α-olefins other than ethylene, the copolymer has mechanical properties. Will be high.
[0017]
Examples of the α-olefin other than ethylene include, but are not particularly limited to, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These α-olefins other than ethylene may be used alone or in combination of two or more.
[0018]
The content of the α-olefin other than ethylene in the copolymer is not particularly limited, but is preferably 0.1 to 50% by weight, more preferably 2 to 40% by weight. When the content of the α-olefin other than ethylene in the copolymer is less than 0.1% by weight, the flexibility of the obtained cross-linked foam may be poor, and conversely, other than ethylene in the copolymer. When the content of the α-olefin exceeds 50% by weight, the heat resistance of the obtained crosslinked foam may be insufficient.
The copolymer of ethylene and an α-olefin other than ethylene may be a copolymer obtained by polymerization using a homogeneous polymerization catalyst. Since this copolymer is generally polymerized using a metallocene-based compound as a homogeneous polymerization catalyst, it may be referred to as a metallocene polyethylene. In metallocene polyethylene, the copolymerization ratio of α-olefins other than ethylene can be easily increased, so that a copolymer having extremely excellent flexibility can be obtained. Further, metallocene polyethylene has a small crystal lamella thickness, so that the number of tie molecules connecting the crystals increases, and therefore, the metallocene polyethylene also has excellent mechanical properties. Therefore, in the present invention, when a crosslinked foam having an excellent balance between flexibility and mechanical properties in a high dimension is desired, it is preferable to use metallocene polyethylene as the thermoplastic resin.
[0020]
The metallocene-based compound which can be a homogeneous polymerization catalyst is not particularly limited, and examples thereof include complexes of transition metals of Group IV, X, and XI. These metallocene compounds may be used alone or in combination of two or more.
[0021]
The transition metal complex is a complex in which a ligand is bonded to a transition metal atom. Examples of the ligand include, but are not limited to, a hydrocarbon group, a substituted hydrocarbon group, and a hydrocarbon group. A cyclopentadiene ring substituted with a hydrogen-substituted metalloid group or the like; a cyclopentadienyl oligomer ring; an indenyl ring; an indenyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group, a hydrocarbon-substituted metalloid group, or the like; Monovalent anion ligands such as bromine and bromine; divalent anion chelate ligand; hydrocarbon group; alkoxide group; amide group; arylamide group; aryloxide group; phosphide group; arylphosphide group; silyl group; Is mentioned. These ligands may be used alone or in combination of two or more.
[0022]
In the present invention, when a crosslinked foam having excellent heat resistance is desired, it is preferable to use a high-density polyethylene resin or a polypropylene resin as the thermoplastic resin. The polypropylene-based resin is not particularly limited, and examples thereof include a homopolymer of propylene and a copolymer of propylene and an α-olefin other than propylene. Examples of the α-olefin other than propylene include, but are not particularly limited to, ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene. And the like. These α-olefins other than propylene may be used alone or in combination of two or more. The polypropylene resin may be used alone or in combination of two or more. Further, the high-density polyethylene resin and the polypropylene-based resin may be used alone or in combination.
[0023]
In the thermoplastic resin used in the present invention, if necessary, in order to modify the properties of the resin, as long as the object of the present invention is not hindered, thermoplastic elastomers and oligomers may be blended. good.
[0024]
The thermoplastic elastomer is not particularly limited, and examples thereof include a styrene-based elastomer, an olefin-based elastomer, a urethane-based elastomer, and a polyester-based elastomer. These thermoplastic elastomers may be used alone or in combination of two or more. The oligomers are not particularly limited, but examples include maleic anhydride-modified ethylene oligomers. These oligomers may be used alone or in combination of two or more. The thermoplastic elastomers and oligomers may be used alone or in combination.
[0025]
Further, the thermoplastic resin used in the present invention may have a nucleating agent that can be a crystal nucleus for refining a crystal as an auxiliary means for homogenizing physical properties, if necessary, as long as the object of the present invention is not hindered. And one or more of various additives such as antioxidants (antiaging agents), heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, flame retardants, antistatic agents, antifogging agents, etc. May be.
[0026]
The layered silicate used in the expandable composition constituting the crosslinked foam of the present invention means a silicate mineral having exchangeable metal cations between crystal layers.
[0027]
The layered silicate is not particularly limited, but includes, for example, smectite clay minerals such as montmorillonite, saponite, hectorite, beidellite, stevensite, nontronite, vermiculite, halloysite, and swelling mica. Among them, montmorillonite and swellable mica are preferably used. The layered silicate may be a natural product or a synthetic product. These layered silicates may be used alone or in combination of two or more.
[0028]
As the layered silicate, it is preferable to use a smectite-based clay mineral or swelling mica having a large shape anisotropy effect defined by the following relational expression (1). By using a layered silicate having a large shape anisotropy effect such as a smectite clay mineral or swelling mica, the obtained crosslinked foam has more excellent mechanical properties.
Shape anisotropy effect = Area of crystal surface (A) / Area of crystal surface (B) ‥‥ (1)
In the above formula, the crystal surface (A) means the layer surface, and the crystal surface (B) means the layer side surface.
[0029]
The shape of the layered silicate is not particularly limited, but the average length of the fine flaky crystal obtained by crushing the aggregated structure is 0.01 to 3 μm, the thickness is 0.001 to 1 μm, and the aspect ratio is 20. The average length is 0.05 to 2 μm, the thickness is 0.01 to 0.5 μm, and the aspect ratio is 50 to 200.
[0030]
The exchangeable metal cations existing between the crystal layers of the layered silicate are metal ions such as sodium and calcium present on the crystal surface of the layered silicate, and these metal ions are composed of a cationic substance and a cation. Since it has exchangeability, various cationic substances can be inserted or trapped between the crystal layers of the layered silicate.
[0031]
The cation exchange capacity of the layered silicate is not particularly limited, but is preferably 50 to 200 milliequivalents / 100 g. When the cation exchange capacity of the layered silicate is less than 50 milliequivalents / 100 g, the amount of the cationic substance trapped between the crystal layers of the layered silicate by cation exchange is reduced, and the crystal layers are sufficiently non-polar. When the cation exchange capacity of the layered silicate exceeds 200 milliequivalents / 100 g, the bonding force between the crystal layers of the layered silicate becomes too strong, and the crystal flakes are separated. May be difficult.
[0032]
In the present invention, when a low-polarity resin such as a polyolefin-based resin is used as the thermoplastic resin, it is preferable that the interlayer of the layered silicate is previously subjected to cation exchange with a cationic surfactant to make the layer hydrophobic. By preliminarily making the interlayer of the layered silicate hydrophobic, the affinity between the layered silicate and the low-polarity thermoplastic resin is increased, and the layered silicate can be finely dispersed more uniformly in the low-polarity thermoplastic resin. it can.
[0033]
The cationic surfactant is not particularly limited, and includes, for example, quaternary ammonium salts and quaternary phosphonium salts. Among them, the non-polarization (hydrophobicity) between the crystal layers of the layered silicate is sufficient. Therefore, a quaternary ammonium salt having an alkyl chain having 6 or more carbon atoms (an alkyl ammonium salt having 6 or more carbon atoms) is preferably used.
[0034]
Examples of the quaternary ammonium salt include, but are not particularly limited to, lauryl trimethyl ammonium salt, stearyl trimethyl ammonium salt, trioctyl ammonium salt, distearyl dimethyl ammonium salt, di-hardened tallow dimethyl ammonium salt, distearyl diammonium salt, and the like. Benzyl ammonium salt, N-polyoxyethylene-N-lauryl-N, N-dimethylammonium salt and the like can be mentioned. These quaternary ammonium salts may be used alone or in combination of two or more.
[0035]
Examples of the quaternary phosphonium salt include, but are not particularly limited to, for example, dodecyltriphenylphosphonium salt, methyltriphenylphosphonium salt, lauryltrimethylphosphonium salt, stearyltrimethylphosphonium salt, trioctylphosphonium salt, distearyl. Dimethylphosphonium salt, distearyldibenzylphosphonium salt and the like can be mentioned. These quaternary phosphonium salts may be used alone or in combination of two or more. Further, the quaternary ammonium salt and the quaternary phosphonium salt may be used alone or in combination.
[0036]
The layered silicate used in the present invention can be improved in dispersibility in a thermoplastic resin by a chemical treatment as described above.
[0037]
The chemical treatment is not limited to (1) a cation exchange method using a cationic surfactant (hereinafter, referred to as a “chemical modification (1) method”). Can be implemented. The layered silicate having improved dispersibility in a thermoplastic resin by the following various chemical treatment methods including the chemical modification (1) method is hereinafter referred to as “organized layered silicate”.
[0038]
(2) Chemical modification The hydroxyl group present on the crystal surface of the organically modified layered silicate chemically treated by the method (1) is converted into a functional group capable of chemically bonding to the hydroxyl group or a functional group having a high chemical affinity without chemical bonding. A method of performing chemical treatment with a compound having one or more groups at the molecular terminal (hereinafter, referred to as “chemical modification (2) method”).
[0039]
(3) Chemical modification A hydroxyl group present on the surface of the crystallized layered silicate chemically treated by the method (1) is converted into a functional group capable of chemically bonding to the hydroxyl group or a functional group having a high chemical affinity without chemical bonding. A method of performing chemical treatment with a compound having one or more groups and reactive functional groups at molecular terminals (hereinafter, referred to as “chemical modification (3) method”).
[0040]
(4) A method of chemically treating a crystal surface of an organically modified layered silicate chemically treated by the method (1) with a compound having anionic surface activity (hereinafter, referred to as a “chemical modification (4) method”). .
[0041]
(5) Chemical Modification In the method (4), a method of chemically treating a compound having one or more reactive functional groups other than the anion site in the molecular chain of the compound having anionic surface activity (hereinafter referred to as “chemical modification (5) ) Law)).
[0042]
(6) The organically modified layered silicate chemically treated by any one of the above-mentioned chemical modification methods (1) to (5) is further treated with a layered silicic acid such as a maleic anhydride-modified polyphenylene ether-based resin. A method using a composition to which a resin having a functional group capable of reacting with a salt is added (hereinafter, referred to as “chemical modification (6) method”).
[0043]
These chemical modification methods may be used alone or in combination of two or more.
[0044]
In the chemical modification (2) method, the functional group capable of chemically bonding to the hydroxyl group or the functional group having high chemical affinity without chemical bonding is not particularly limited. Examples thereof include an alkoxyl group and a glycidyl group. Functional groups such as a group, a carboxyl group (including a dibasic acid anhydride), a hydroxyl group, an isocyanate group, and an aldehyde group, and other functional groups having high chemical affinity with a hydroxyl group. These functional groups may be used alone or in combination of two or more.
[0045]
The compound having a functional group capable of chemically bonding to a hydroxyl group or a functional group having a high chemical affinity without chemical bonding is not particularly limited, for example, a silane compound having a functional group exemplified above, Examples include titanate compounds, glycidyl compounds, carboxylic acids, alcohols and the like. These compounds may be used alone or in combination of two or more.
[0046]
Although it does not specifically limit as said silane compound, For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris ((beta) -methoxyethoxy) silane, gamma-aminopropyltrimethoxysilane, gamma-aminopropylmethyldimethoxy Silane, γ-aminopropyldimethylmethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyldimethylethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, hexyltri Methoxysilane, hexyltriethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) γ-aminopropyltriethoxysilane, N-β- (A Noethyl) γ-aminopropylmethyldimethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ- Methacryloxypropyltriethoxysilane and the like can be mentioned. These silane compounds may be used alone or in combination of two or more.
[0047]
Further, in the chemical modification (4) method and the chemical modification (5) method, a compound having anionic surface activity and / or having one anionic surface activity and having one reactive functional group other than an anion site in a molecular chain. The compound having the above may be any compound as long as it can chemically treat the layered silicate by ionic interaction, and is not particularly limited. Examples thereof include sodium laurate, sodium stearate, and oleic acid. Sodium, higher alcohol sulfates, secondary higher alcohol sulfates, unsaturated alcohol sulfates, and the like. These compounds may be used alone or in combination of two or more.
[0048]
The layered silicate used in the present invention has an average interlayer distance of the (001) plane measured by a wide-angle X-ray diffraction measurement method of 3 nm or more, and a part or all of the layered silicate is dispersed in the thermoplastic resin into five layers or less. The layered silicate is preferably a layered silicate having an average interlayer distance of 6 nm or more, and a part or all of which is dispersed in a thermoplastic resin in five or less layers. is there. Incidentally, the average interlayer distance of the layered silicate referred to in the present invention means the average interlayer distance in the case of a layer of fine flaky crystals of the layered silicate, X-ray diffraction peak and transmission electron micrograph, that is, Can be calculated by a wide-angle X-ray diffraction measurement method.
[0049]
When the average interlayer distance of the layered silicate is 3 nm or more and part or all of the layered silicate is dispersed in 5 layers or less, the layered silicate is mixed and dispersed in the thermoplastic resin. The crosslinked foam made of the foamable composition obtained exhibits excellent flame retardancy, mechanical properties, heat resistance, dimensional stability and the like.
[0050]
The fact that the average interlayer distance of the layered silicate is 3 nm or more means that the interlayer of the layered silicate is cleaved to 3 nm or more, and that part of the layered silicate or part of the layered silicate in the thermoplastic resin. The fact that the entirety is dispersed in 5 layers or less means that a part or all of the layered silicate laminate is widely dispersed in the thermoplastic resin. Is weakened, whereby the above effect can be obtained.
[0051]
In particular, when the average interlayer distance of the layered silicate is 6 nm or more, a crosslinked foam made of an expandable composition obtained by blending and dispersing the layered silicate in a thermoplastic resin has remarkably excellent flame retardancy, It exhibits mechanical properties, heat resistance, dimensional stability and the like. Further, when the average interlayer distance of the layered silicate is 3 nm or more, preferably 6 nm or more, the fine flaky crystals of the layered silicate are separated from each other and the interaction of the layered silicate is weakened so as to be almost negligible. In addition, there is an advantage that the dispersion state of the fine flaky crystals constituting the layered silicate in the thermoplastic resin proceeds in the direction of stabilization of crushing.
[0052]
In addition, the fact that part or all of the layered silicate is dispersed in the thermoplastic resin in five or less layers means, specifically, that 10% or more of the layered silicate is dispersed in the five layers or less. And more preferably 20% or more of the layered silicate is dispersed in 5 layers or less.
[0053]
The number of layers of the layered silicate is preferably divided into 5 or less layers, whereby the above effect can be obtained. More preferably, the layered silicate is divided into 3 layers or less. Particularly preferably, it is sliced into a single layer.
[0054]
In the foamable composition constituting the crosslinked foam of the present invention, the average interlayer distance of the layered silicate is 3 nm or more, and part or all of the layered silicate is dispersed in the thermoplastic resin into five or less layers. In other words, if the layered silicate is highly dispersed in the thermoplastic resin, the interface area between the thermoplastic resin and the layered silicate increases, Average distance becomes smaller.
[0055]
When the interface area between the thermoplastic resin and the layered silicate increases, the degree of constraint of the thermoplastic resin on the surface of the layered silicate increases, and mechanical properties such as mechanical strength and elastic modulus are improved. Further, when the degree of restraint of the thermoplastic resin on the surface of the layered silicate increases, the melt viscosity increases, and the foamability and moldability also improve.
[0056]
On the other hand, when the average distance between the fine flaky crystals of the layered silicate is small, a sintered body is easily formed by the movement of the fine flaky crystals of the layered silicate during combustion. That is, a crosslinked foam made of a foamable composition in which fine flaky crystals of a layered silicate are dispersed such that the average interlayer distance is 3 nm or more facilitates formation of a sintered body that can be a flame-retardant film. Since this sintered body is formed at an early stage of combustion, not only can the supply of oxygen from the outside be shut off, but also the combustible gas generated by combustion can be shut off. Expresses flame retardancy.
[0057]
The foamable composition constituting the crosslinked foam of the present invention is such that 10 to 70 parts by weight of the above layered silicate (including the organically modified layered silicate) is mixed with 100 parts by weight of the thermoplastic resin. Is required, and preferably 15 to 50 parts by weight of the layered silicate based on 100 parts by weight of the thermoplastic resin.
[0058]
If the compounding amount of the layered silicate with respect to 100 parts by weight of the thermoplastic resin is less than 10 parts by weight, it becomes difficult to form a sintered body at the time of combustion, so that the flame retarding effect is small, and If the compounding amount of the layered silicate with respect to 100 parts by weight of the resin exceeds 70 parts by weight, it becomes difficult to sufficiently expand the foamable composition or the apparent density (apparent specific gravity) of the obtained crosslinked foam increases. Too much, making it less practical.
[0059]
The method for dispersing the layered silicate in the thermoplastic resin is not particularly limited. For example, a method using the organically modified layered silicate; a method in which the thermoplastic resin and the layered silicate are mixed by an ordinary method Thereafter, a method of foaming; a method using a dispersant, and the like. By using these dispersion methods, the layered silicate can be uniformly and finely dispersed in the thermoplastic resin.
[0060]
A method of mixing the thermoplastic resin and the layered silicate by a conventional method and then foaming the mixture will be described below. This method also serves as a method of foaming a thermoplastic resin using a foaming agent and converting the foaming energy to the dispersion energy of the layered silicate, and at the same time, a method of forming a foam.
[0061]
The foaming agent is not particularly limited, and examples thereof include a gaseous foaming agent, a volatile liquid foaming agent, and a heat decomposition type solid foaming agent. These foaming agents may be used alone or in combination of two or more.
[0062]
By foaming the thermoplastic resin in the presence of the layered silicate, a specific method of uniformly and finely dispersing the layered silicate in the thermoplastic resin and simultaneously forming a foam is specifically limited. However, for example, the following method can be mentioned.
[0063]
Method (A): A thermoplastic resin composition (hereinafter simply referred to as “composition”) consisting of 100 parts by weight of a thermoplastic resin and 10 to 70 parts by weight of a layered silicate is charged with a gaseous blowing agent (under normal temperature and normal pressure). Gaseous compound) or a volatile liquid foaming agent is impregnated under high pressure or normal pressure to prepare a foamable composition, and then the gaseous foaming agent or the volatile liquid foaming agent is added to the foamable composition. By dispersing the layered silicate in the thermoplastic resin and forming a foam at the same time.
[0064]
Method (B): A layered silicate is prepared by preparing an expandable composition using a layered silicate in which a thermally decomposable foaming agent is previously contained between crystal layers, and then decomposing the thermally decomposable foaming agent by heating. A foam is formed at the same time as dispersing in a thermoplastic resin.
[0065]
Method (C): A layered silicate and a thermally decomposable foaming agent are previously mixed and dispersed in a thermoplastic resin to prepare a foamable composition, and the thermally decomposable foaming agent is decomposed by heating to form a layered material. A method in which a silicate is dispersed in a thermoplastic resin and a foam is formed at the same time.
[0066]
The gaseous foaming agent and the volatile liquid foaming agent used in the above-mentioned method (A) are not particularly limited, but, for example, gases such as carbon dioxide (carbon dioxide), nitrogen, oxygen, argon, chlorofluorocarbon and the like. Foaming agents, low molecular weight hydrocarbons such as pentane, neopentane, butane, hexane, heptane, chlorinated hydrocarbons such as methyl chloride, methylene chloride, trichloroethylene, dichloroethane, CFC-11, CFC-12, CFC-113, Examples include fluorinated hydrocarbons such as CFC-141b, water, alcohol, benzene, toluene, xylene, mesitylene, and other easily volatile liquid foaming agents. Among them, gaseous foaming agents are preferably used. These gaseous foaming agents and volatile liquid foaming agents may be used alone or in combination of two or more. In addition, the gaseous foaming agent and the volatile liquid foaming agent may be used alone or in combination.
[0067]
Among the above gaseous foaming agents, carbon dioxide is more preferably used because gas collection is unnecessary and handling is safe. Carbon dioxide can be made supercritical at relatively low temperatures and relatively low pressures, and acts more effectively on dispersion of phyllosilicates during supercritical conditions. Here, the supercritical state refers to a state in which the temperature and pressure are higher than the critical point of the foaming agent to be impregnated, and there is no distinction between gas and liquid, having intermediate properties between gas and liquid, and heat. It has the properties of high conductivity, high diffusion speed, and low viscosity. Therefore, the supercritical state is advantageous for dispersing the layered silicate.
[0068]
The method of impregnating the gaseous foaming agent or the easily volatile liquid foaming agent into the composition comprising the thermoplastic resin and the layered silicate is not particularly limited, but, for example, the composition may be placed in a closed autoclave. Method and pressurizing the gaseous foaming agent and the volatile liquid foaming agent, and charging the above composition into an extruder, and using a vent type screw as a screw, a gaseous part is formed in the vent part from the middle of the cylinder. Examples include a method of injecting a foaming agent and a readily volatile liquid foaming agent. The former method is preferable in that the control of pressure and temperature is easy, and the latter method is a method in which the composition is in a molten state. By performing pressure sealing, the composition can be effectively impregnated with a gaseous foaming agent or a volatile liquid foaming agent, which is preferable in that a foam can be continuously produced. There.
[0069]
The temperature at which the composition is impregnated with the gaseous foaming agent or the volatile liquid foaming agent is not particularly limited as long as the composition does not deteriorate. However, the higher the impregnation temperature, the higher the amount of the gaseous foaming agent or the easily volatile liquid foaming agent dissolved in the composition, so that a foam having a high expansion ratio can be obtained. Therefore, the impregnation temperature is preferably higher within the temperature at which the composition does not deteriorate, and in order to obtain a good foaming state, when the thermoplastic resin is a crystalline resin, the melting point of the thermoplastic resin ± 20. ° C, and when the thermoplastic resin is an amorphous resin, the glass transition temperature of the thermoplastic resin is preferably ± 20 ° C.
[0070]
The thermal decomposition type foaming agent used in the methods (B) and (C) is not particularly limited. For example, azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl Hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide) and the like. These thermal decomposition type foaming agents may be used alone or in combination of two or more.
[0071]
The blending amount of the heat-decomposable blowing agent is not particularly limited, but is preferably 1 to 50 parts by weight based on 100 parts by weight of the thermoplastic resin. If the amount of the heat-decomposable foaming agent is less than 1 part by weight based on 100 parts by weight of the thermoplastic resin, the foaming property of the foamable composition may be insufficient. If the amount of the decomposable foaming agent exceeds 50 parts by weight, the mechanical properties of the resulting crosslinked foam may be reduced.
[0072]
In the above-mentioned method (B), the method of causing the thermally decomposable foaming agent to be contained between the crystal layers of the layered silicate is not particularly limited, and examples thereof include the following methods.
[0073]
Method (a): The terminal amino group of the heat-decomposable blowing agent is treated with hydrochloric acid to form a quaternary aminate, and the exchangeable metal cation present between the crystal layers of the layered silicate and the quaternary amine are cation-exchanged in water. A thermal decomposition type foaming agent is contained between the crystal layers of the layered silicate.
[0074]
Method (b): A method in which a heat-decomposable foaming agent is solvated in water with an exchangeable metal cation present between the crystal layers of the layered silicate, so that the heat-decomposable foaming agent is contained between the crystal layers of the layered silicate.
[0075]
Generally, general-purpose thermal decomposition type foaming agents often have an amino group at the terminal, so the above-mentioned method (a) is practical. In general, general-purpose thermal decomposition type foaming agents are nitrogen and carbon-carbon double. The method (b) is also practical because many of the compounds have a site forming a coordination bond with a metal such as a bond.
[0076]
The temperature at which the thermally decomposable blowing agent is contained between the crystal layers of the layered silicate is not particularly limited as long as the composition comprising the thermoplastic resin and the layered silicate does not deteriorate and the temperature does not decompose the thermally decomposable blowing agent. It is not done.
[0077]
Regarding the dispersion of the layered silicate in the thermoplastic resin, the more the layered silicate is separated and the finer flaky crystals are dispersed in the thermoplastic resin, the smaller the average distance between the fine flaky crystals becomes, In this case, a sintered body is easily formed by the movement of the fine flaky crystal of the layered silicate. Further, the finer the flaky crystals of the layered silicate are dispersed in the thermoplastic resin, the better the mechanical properties and dimensional stability of the obtained crosslinked foam.
[0078]
Both of the above phenomena are based on the fact that the interface area between the thermoplastic resin and the layered silicate increases with an increase in the dispersion ratio of the fine flaky crystals of the layered silicate. That is, at the interface between the thermoplastic resin and the layered silicate, the mechanical properties of the thermoplastic resin are increased by restricting the molecular motion of the thermoplastic resin, so that the dispersion ratio of the fine flaky crystals of the layered silicate is increased. The effect of increasing the mechanical properties of the obtained cross-linked foam increases as the value of.
[0079]
The foamable composition constituting the crosslinked foam of the present invention, in addition to the essential components of the thermoplastic resin, the layered silicate and the blowing agent, if necessary as long as the object of the present invention is not hampered, for example, Acid-modified polyolefin resin for further improving the affinity between the thermoplastic resin and the layered silicate, flame retardant for further improving the flame retardancy, foaming aid for further improving the foaming property, cross-linkability Cross-linking aids, fillers, softeners, plasticizers, lubricants, antistatic agents, anti-fogging agents, coloring agents, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, ultraviolet absorption to further improve One or two or more of various additives such as an agent may be blended.
[0080]
Examples of the acid-modified polyolefin resin include, but are not particularly limited to, acid-modified polyethylene resins such as maleic anhydride-modified ethylene oligomer and ethylene- (meth) acrylic acid copolymer, and maleic anhydride-modified propylene. Examples thereof include an oligomer and an acid-modified polypropylene resin such as a propylene-acrylic acid copolymer. These acid-modified polyolefin resins may be used alone or in combination of two or more.
[0081]
The amount of the acid-modified polyolefin resin is not particularly limited, but is preferably 1 to 50 parts by weight of the acid-modified polyolefin resin per 100 parts by weight of the thermoplastic resin. If the amount of the acid-modified polyolefin-based resin is less than 1 part by weight based on 100 parts by weight of the thermoplastic resin, the affinity between the thermoplastic resin and the layered silicate may not be sufficiently improved. If the amount of the acid-modified polyolefin-based resin is more than 50 parts by weight per part by weight, it may not be possible to obtain a proper melt viscosity or a proper cohesive force required to obtain a homogeneous crosslinked foam.
[0082]
Examples of the flame retardant include, but are not particularly limited to, metal hydroxides such as aluminum hydroxide and magnesium hydroxide; metal oxides; phosphorus compounds such as red phosphorus and ammonium polyphosphate; melamine; Examples thereof include melamine derivatives such as melamine cyanurate, melamine isocyanurate, melamine phosphate, and surface-treated products thereof. Among them, metal hydroxides and melamine derivatives are preferably used. These flame retardants may be used alone or in combination of two or more.
[0083]
The compounding amount of the metal hydroxide is not particularly limited, but is preferably 0.1 to 200 parts by weight of the metal hydroxide with respect to 100 parts by weight of the thermoplastic resin, and more preferably thermoplastic. The metal hydroxide is 5 to 100 parts by weight based on 100 parts by weight of the resin. If the compounding amount of the metal hydroxide is less than 0.1 part by weight with respect to 100 parts by weight of the thermoplastic resin, the effect of improving the flame retardancy due to the compounding of the metal hydroxide may not be sufficiently obtained. If the blending amount of the metal hydroxide with respect to 100 parts by weight of the thermoplastic resin exceeds 200 parts by weight, it becomes difficult to sufficiently expand the expandable composition, or the apparent density (apparent specific gravity) of the obtained crosslinked foamed body ) May be too high and the utility may be poor.
[0084]
Further, the amount of the melamine derivative is not particularly limited, but is preferably 0.1 to 50 parts by weight, more preferably 100 parts by weight of the melamine derivative per 100 parts by weight of the thermoplastic resin. The melamine derivative is used in an amount of 1 to 40 parts by weight based on parts by weight. If the amount of the melamine derivative is less than 0.1 part by weight based on 100 parts by weight of the thermoplastic resin, the effect of improving the flame retardancy due to the incorporation of the melamine derivative may not be sufficiently obtained. If the amount of the melamine derivative per 100 parts by weight exceeds 50 parts by weight, it may be difficult to sufficiently foam the foamable composition.
[0085]
Further, the foaming aid is not particularly limited, and examples thereof include zinc stearate, calcium stearate, and active zinc oxide. These foaming aids may be used alone or in combination of two or more.
[0086]
The amount of the foaming aid is not particularly limited, but is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the thermoplastic resin. If the compounding amount of the foaming aid is less than 0.1 part by weight with respect to 100 parts by weight of the thermoplastic resin, the effect of improving the foamability by adding the foaming aid may not be sufficiently obtained. If the blending amount of the foaming aid with respect to 100 parts by weight of the resin exceeds 10 parts by weight, the obtained crosslinked foam may be broken.
[0087]
Further, the crosslinking assistant is not particularly limited. For example, a radical generator such as benzoyl peroxide, divinylbenzene, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) ) Polyfunctional monomers such as acrylate, 1,9-nonanediol di (meth) acrylate, and 1,2,4-benzenetricarboxylic acid triallyl ester. These crosslinking aids may be used alone or in combination of two or more.
[0088]
The amount of the crosslinking aid is not particularly limited, but is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the thermoplastic resin. If the amount of the crosslinking aid is less than 0.1 part by weight based on 100 parts by weight of the thermoplastic resin, the crosslinking of the thermoplastic resin becomes insufficient, and a uniform crosslinked foam may not be obtained. If the blending amount of the crosslinking aid with respect to 100 parts by weight of the thermoplastic resin exceeds 10 parts by weight, the crosslinking density of the thermoplastic resin becomes too high, and the foaming property of the foamable composition may be impaired.
[0089]
The method for producing the expandable composition constituting the crosslinked foam of the present invention is not particularly limited. For example, each of a predetermined amount of a thermoplastic resin, a layered silicate and, for example, a pyrolytic foaming agent, A method of directly blending and kneading one kind or two or more kinds of each kind of various additives to be blended according to the conditions at room temperature or under heating (direct kneading method), or a method of preparing a predetermined amount of a thermoplastic resin in advance. A master batch is prepared by mixing and kneading a predetermined amount of a layered silicate into a part of the master batch, and the master batch and a predetermined amount of the remainder (remaining amount) of the thermoplastic resin, for example, a pyrolysis type foaming agent and A method (master batch method) of kneading one or more predetermined amounts of various additives to be blended at room temperature or under heating (master batch method) and the like may be used, and any method may be adopted. When the foaming agent to be blended is a heat-decomposable foaming agent, the kneading temperature is preferably lower than the decomposition temperature of the heat-decomposable foaming agent.
[0090]
The concentration of the layered silicate in the masterbatch is not particularly limited, but is preferably 15 to 100 parts by weight, more preferably 20 to 70 parts by weight, based on 100 parts by weight of the thermoplastic resin. Department. In the above masterbatch, if the concentration of the layered silicate with respect to 100 parts by weight of the thermoplastic resin is less than 15 parts by weight, the convenience as a masterbatch that can be diluted to an arbitrary concentration may be lost. If the concentration of the layered silicate with respect to 100 parts by weight exceeds 100 parts by weight, the dispersibility of the masterbatch itself deteriorates, or the layered silicate is adjusted to a predetermined blending amount by a predetermined amount (remaining amount) of the thermoplastic resin. In some cases, the dispersibility of the layered silicate during dilution may be poor.
[0091]
Specific methods for producing the foamable composition by the direct kneading method or the masterbatch method are not particularly limited, for example, using an extruder, a two-roll, kneading machine such as a Banbury mixer, A predetermined amount of each of the thermoplastic resin, the layered silicate, and, for example, the pyrolytic blowing agent constituting the expandable composition, and one or more predetermined amounts of one or more kinds of various additives to be blended as necessary, at room temperature. Under or under heating, a method of melt-kneading, a thermoplastic resin, a layered silicate and, for example, a pyrolytic foaming agent, and one or more of various additives blended as necessary, After kneading in a solvent that can be dissolved or dispersed, a method of removing the solvent and the like are mentioned, and any method may be adopted.
[0092]
Further, for example, using a layered silicate containing a polymerization catalyst (polymerization initiator) such as a transition metal complex between crystal layers, kneading predetermined amounts of a monomer constituting the thermoplastic resin and the above-mentioned layered silicate, After the monomer is polymerized to produce a thermoplastic resin, for example, a method in which a heat-decomposable foaming agent and one or two or more predetermined amounts of various additives to be blended as required are blended and kneaded. May be taken. In any of the above methods, when the compounding foaming agent is a thermal decomposition type foaming agent, the kneading temperature is preferably lower than the decomposition temperature of the thermal decomposition type foaming agent.
[0093]
The crosslinked foam of the present invention is obtained by first crosslinking the above-mentioned foamable composition and then foaming the composition.
[0094]
The method for molding the crosslinked foam of the present invention is not particularly limited, and examples thereof include the methods (A), (B) and (C), and any of the molding methods is employed. However, among them, the method (C) is preferred because a homogeneous crosslinked foam can be molded with excellent productivity. In addition, these molding methods may be employed alone or in combination of two or more.
[0095]
The molding method by the method (C) is not particularly limited. For example, predetermined amounts of a thermoplastic resin, a layered silicate, and a pyrolytic foaming agent constituting the foamable composition and, for example, a crosslinking aid One or more predetermined amounts of various additives, such as foaming aids and foaming aids, are supplied to an extruder, melt-kneaded and extruded, and a foamable sheet comprising a foamable composition After producing the (foamable raw material), the foamable sheet is irradiated with a predetermined amount of, for example, an electron beam to crosslink, and the obtained foamable crosslinked sheet is introduced into a foaming furnace and continuously heated and foamed. For example, a method of irradiating the foamable composition with a predetermined amount of an electron beam to crosslink, supplying the obtained foamable crosslinked composition to a mold and heating and foaming in a batch manner, and the like. May be taken, but above all, raw Because of excellent sex, it is preferable to adopt the former method.
[0096]
The thus obtained crosslinked foam of the present invention has a gel fraction of 15 to 70% by weight and an apparent density of 0.03 to 0.1 g / cm. ³ It is necessary to be. In addition, the gel fraction referred to in the present invention means a gel fraction measured by the following method, and the apparent density referred to in the present invention is JIS K-6767 "foamed plastic-polyethylene-test method". Means the apparent density measured in accordance with
(Method for measuring gel fraction)
After weighing (Ag) a certain amount of the crosslinked foam and immersing it in xylene at 120 ° C. for 24 hours, the insoluble matter was filtered through a 200-mesh wire gauze, and the filtration residue on the wire gauze was vacuum-dried. The weight (Bg) at that time is measured, and the gel fraction (% by weight) is calculated by the following equation.
Gel fraction (% by weight) = 100 × B / A
[0097]
If the gel fraction of the crosslinked foam is out of the range of 15 to 70% by weight, it is not possible to obtain a proper melt viscosity or a proper cohesive force required to obtain a homogeneous crosslinked foam, Will lack homogeneity.
[0098]
The apparent density of the crosslinked foam is 0.03 g / cm. ³ If it is less than 3, the combustion residue (ash) after combustion becomes brittle, making it difficult to maintain the shape, and conversely, the apparent density of the crosslinked foam becomes 0.1 g / cm. ³ When it exceeds, the crosslinked foam expands at the time of combustion, and it becomes difficult to maintain the shape.
[0099]
[Action]
Since the crosslinked foam of the present invention is composed of a foamable composition in which a specific amount of a layered silicate and a blowing agent are blended with a thermoplastic resin, a sintered body of the layered silicate is formed during combustion, and It has little drip phenomenon during combustion and changes in shape before and after combustion, and exhibits excellent flame retardancy, does not cause shape collapse of combustion residues even after combustion, and can effectively prevent fire spread. .
[0100]
In addition, the crosslinked foam of the present invention is a crosslinked foam excellent in homogeneity because the gel fraction is in a specific range, the melt viscosity and the cohesive force during foaming are appropriate, and the apparent Since the density is in a specific range, the shape change before and after the combustion is smaller.
[0101]
BEST MODE FOR CARRYING OUT THE INVENTION
EXAMPLES The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
[0102]
In this example, the following raw materials were used.
1. Thermoplastic resin
(1) Ethylene-vinyl acetate copolymer: EVA (trade name “Evaflex EV460”, vinyl acetate content: 19% by weight, manufactured by Du Pont-Mitsui Polychemicals)
(2) Low density polyethylene resin: LDPE (trade name "LE520H", manufactured by Nippon Polychem Co., Ltd.)
2. Layered silicate
(1) Swellable fluorinated mica which has been treated with distearyl dimethyl ammonium chloride (trade name “Somasif MAE-100”, average length: 0.2 μm, thickness: 0.002 μm, aspect ratio: 100, corp. Chemical company)
(2) Montmorillonite treated with distearyl dimethyl ammonium chloride (trade name "Clayton HY", manufactured by Southern Clay Products)
3. Thermal decomposition type foaming agent
Azodicarbonamide (trade name "Uniform AZ SO-40", manufactured by Otsuka Chemical Co., Ltd.)
4. Foaming aid
・ Zinc stearate (trade name “SZ-2000”, manufactured by Sakai Chemical Co., Ltd.)
[0103]
(Example 1)
100 parts by weight of an ethylene-vinyl acetate copolymer "Evaflex EV460" as a thermoplastic resin, and 15 parts by weight of a swellable fluorine mica "Somasif MAE-100" which has been treated with distearyldimethylammonium chloride as a layered silicate. Then, 15 parts by weight of azodicarbonamide “Uniform AZ SO-40” as a thermal decomposition type foaming agent and 2 parts by weight of zinc stearate “SZ-2000” as a foaming aid are supplied to Labo Plastomill and melted at 110 ° C. for 15 minutes. By kneading, a foamable composition was prepared.
[0104]
Next, using a hand press, the foamable composition obtained above was pressed at 110 ° C. to form a foamable sheet (foamable raw material) having a thickness of 1 mm, and then the foamable sheet was subjected to 100 mA, 800 KV. Was irradiated with 2 Mrad to crosslink the foamable sheet. Thereafter, the foamable crosslinked sheet was left in a gear oven at 240 ° C. for 100 seconds to foam, thereby producing a crosslinked foam.
[0105]
(Examples 2 to 7) and (Comparative Examples 1 to 6)
A crosslinked foam was produced in the same manner as in Example 1 except that the composition of the foamable composition was changed to the composition shown in Table 1.
[0106]
The thickness and expansion ratio of the twelve types of crosslinked foams obtained in Examples 1 to 7 and Comparative Examples 1 to 5 were measured. Further, the gel fraction and apparent density of the above 12 kinds of crosslinked foams were measured by the above method. The results were as shown in Table 1. In addition, since the favorable crosslinked foam was not obtained about the comparative example 6, the said measurement and the following evaluation of the flame retardancy were not performed.
[0107]
Next, the flame retardancy of the crosslinked foams obtained in Example 1 and Comparative Example 1 was evaluated by the following UL94HBF method and UL94HB method. Further, the flame retardancy of the crosslinked foams obtained in Examples 2 to 7 and Comparative Examples 2 to 5 was evaluated by the following UL94HBF method. The results were as shown in Table 1.
[0108]
1. Flame retardancy test-UL94HBF method
According to the flame retardant standard UL94HBF of Underwriters Laboratory (USA), a 2 inch wide by 6 inch long burning test piece cut from a cross-linked foam is placed on a wire mesh, and the flame is applied to the entire width of the burning test piece. After burning a gas burner from 1 inch to 5 inches from the end in the longitudinal direction of the combustion test piece, measure the dimensions of the combustion test piece in the width direction and the length direction, and determine according to the following criteria. The flame retardancy was evaluated.
(Judgment criteria)
○ ‥‥ No change was observed in the shape of the combustion test piece before and after combustion.
× ‥‥ A dripping phenomenon was observed in the burning test piece during burning. Also, the fuel after combustion
Shrinkage and expansion were observed in the fired test piece.
[0109]
2. Flame retardancy test-UL94HB method
In accordance with UL94HBF, a flame-retardant standard of Underwriters Laboratory (USA), the combustion test piece is cut horizontally from a 2 inch wide by 6 inch long cut piece from a cross-linked foam so as to be horizontal. , And a gas burner is brought into contact with the other end in the length direction of the combustion test piece, and the flame is burned from 1 inch to 4 inches from the other end in the length direction of the combustion test piece. And the dimension in the length direction was measured, and the flame retardancy was evaluated according to the same criteria as in the case of the UL94HBF method.
[0110]
[Table 1]

[0111]
As is clear from Table 1, the crosslinked foam of Example 1 according to the present invention passed both the UL94HBF method and the UL94HB method of the flame retardancy test, and exhibited excellent flame retardancy. In addition, all of the crosslinked foams of Examples 2 to 7 according to the present invention passed the UL94HBF method of the flame retardancy test, and exhibited excellent flame retardancy.
[0112]
On the other hand, the crosslinking amount of Comparative Example 1 in which the amount of the layered silicate (swellable fluorine mica) was less than 10 parts by weight (5 parts by weight) per 100 parts by weight of the thermoplastic resin (ethylene-vinyl acetate copolymer). The foam failed both the UL94HBF method and the UL94HB method of the flame retardancy test, and had poor flame retardancy. The crosslinked foam of Comparative Example 2 in which the blending amount of the layered silicate (montmorillonite) was less than 10 parts by weight (5 parts by weight) with respect to 100 parts by weight of the thermoplastic resin (ethylene-vinyl acetate copolymer), apparent density Is 0.1 g / cm ³ (0.167 g / cm ³ ) Crosslinked foam of Comparative Example 3, apparent density 0.03 g / cm ³ Less than (0.029 g / cm ³ Both of the crosslinked foam of Comparative Example 4 and the crosslinked foam of Comparative Example 5, which did not contain the layered silicate, failed the UL94HBF method of the flame retardancy test and had poor flame retardancy. . Further, a foamable composition in which the blending amount of the layered silicate (swellable fluoromica) with respect to 100 parts by weight of the thermoplastic resin (ethylene-vinyl acetate copolymer) exceeded 70 parts by weight (80 parts by weight) was used. As for Comparative Example 6, good flame-retardant properties could not be evaluated because a good crosslinked foam was not obtained.
[0113]
【The invention's effect】
As described above, the crosslinked foam of the present invention is excellent in flame retardancy, generates little drip phenomenon during combustion and changes in shape before and after combustion, and further has mechanical properties, heat resistance, flexibility, and shock absorption. It has excellent performance such as excellent heat insulation, dimensional stability, and low coefficient of linear expansion.For example, ceiling materials, doors, vehicle interior materials such as instrument panels, cushioning materials, heat insulating materials, etc. Initially, it is suitably used for various industrial uses.

Claims (1)

It consists of a foamable thermoplastic resin composition containing 10 to 70 parts by weight of a layered silicate and a foaming agent with respect to 100 parts by weight of a thermoplastic resin, and has a gel fraction of 15 to 70% by weight. thermoplastic resins crosslinked foam density is characterized by a 0.03~0.1g / cm ^3.