JPH09124818A - Foam comprising modified polypropylene-based resin and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject low-density foam, having a high closed cell ratio, beautiful in appearance, excellent in heat resistance and useful as a cushioning material, etc., by melt kneading a polypropylene-based resin with a polyphenylene ethereal resin, etc., and then expanding the resultant kneaded mixture. SOLUTION: This foam is obtained by melt kneading a modified polypropylene-based resin prepared by melt kneading (A) a polypropylene-based resin with (B) a polyphenylene ethereal resin, (C) an aromatic vinyl monomer and (D) a radical polymerization initiator with preferably (E) a foaming agent, then extruding the kneaded mixture and thereby expanding the extruded mixture. The component (B) preferably comprises one or more selected from the group consisting of styrene, methylstyrene and divinylbenzene. The component (D) preferably comprises one or more selected from the group consisting of a peroxyketal, a dialkyl peroxide, a diacyl peroxide and a peroxy ester.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a foam made of a modified polypropylene resin and a method for producing the foam. More specifically, a polypropylene resin, a polyphenylene ether resin, a modified polypropylene resin obtained by melt-kneading an aromatic vinyl monomer and a radical polymerization initiator, which has excellent heat resistance and a high closed cell rate, The present invention relates to a foam having a low density and a beautiful appearance, and a method for producing the foam.

[0002]

2. Description of the Related Art A foam made of a thermoplastic resin is generally used for a heat insulating material, a cushioning material, a core material, a food container, etc. because it is lightweight and has a good heat insulating property and a good shock absorbing property against external stress. ing. Of these, foams made of polypropylene-based resin have good chemical resistance, impact resistance and heat resistance, and are therefore particularly suitable for use as cushioning materials.

[0003] However, polypropylene resins are
Since it is a crystalline resin, the viscosity and tension at the time of melting are low, and when the resin is foamed, the strength of the cell wall is not sufficiently maintained at the time of foaming. Further, since this resin has a low gas barrier property, when the resin is foamed, the gas generated from the foaming agent is easily dissipated to the outside from the bubbles. Therefore, by foaming the polypropylene resin,
It was difficult to obtain a foam having an excellent appearance and a high closed cell ratio and a low density.

As a method for improving the foamability of a polypropylene resin, for example, a method of adding a crosslinking aid to the polypropylene resin to crosslink its molecules (see, for example, JP-B-45-40420) and polypropylene resins. A method of blending polyethylene and foaming it (see, for example, Japanese Patent Publication No. 44-2574), a method of blending polystyrene with polypropylene resin and foaming it (for example, Japanese Patent Publication No. 43-1337).
5), a method of blending a polypropylene resin with polystyrene and polyphenylene ether, and foaming this (see JP-A-6-25655).
And so on.

However, even if these methods are used,
The effect of improving foamability is not sufficient.

[0006] Further, when it is intended to improve the foaming property of the polypropylene resin by blending a resin having a low heat distortion temperature, the high heat resistance, which is one of the characteristics of the polypropylene resin, may be impaired. is there.

In Japanese Patent Publication No. 48-4859,
Polyethylene, peroxide type radical polymerization initiator,
Knead the styrene monomer and blowing agent in the extruder,
A method for producing a foam by reacting and extruding is disclosed, but polypropylene is not disclosed at all.

As described above, the polypropylene resin is sufficiently improved in foamability, and the resin has a high expansion ratio,
At present, no method has been found for producing a foam having a high closed cell rate and a low density.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is that it is made of a modified polypropylene resin having an improved foaming property and has excellent heat resistance, a high expansion ratio, a high closed cell ratio, a low density, and an appearance. To provide a beautiful foam.

[0010]

The present invention relates to a foam made of a polypropylene resin, a polyphenylene ether resin, an aromatic vinyl monomer and a modified polypropylene resin obtained by melt-kneading a radical polymerization initiator. .

The aromatic vinyl monomer is preferably composed of one or more selected from the group consisting of styrene, methylstyrene and divinylbenzene.

It is preferable that the radical polymerization initiator comprises one or more selected from the group consisting of peroxyketal, dialkyl peroxide, diacyl peroxide and peroxy ester.

The present invention also relates to a method for producing a foamed body in which the modified polypropylene resin and the foaming agent are melt-kneaded and then extruded to foam.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that a polypropylene resin,
Obtained by kneading the polyphenylene ether resin, the aromatic vinyl monomer and the radical polymerization initiator at a temperature at which the polypropylene resin melts and at a temperature at which the radical polymerization initiator can decompose. The foamability of the modified polypropylene resin is remarkably improved with respect to that of the polypropylene resin before melt-kneading (hereinafter also referred to as "the polypropylene resin before modification"), and the heat resistance It was found that by foaming this modified polypropylene resin, it is possible to obtain a foam having excellent heat resistance, a high closed cell ratio, a low density, and a beautiful appearance, and completed the present invention. It was

In the present invention, the reason why the foamability of the modified polypropylene resin is remarkably improved is not clear, but among polypropylene resins, polyphenylene ether resins, aromatic vinyl monomers and radical polymerization initiators, In either case, the object of the present invention cannot be achieved.

The modified polypropylene resin of the present invention contains a polyphenylene ether resin and therefore has excellent heat resistance.

Of the above-mentioned polypropylene resins, polyphenylene ether resins, aromatic vinyl monomers and radical polymerization initiators, polyphenylene is used if aromatic vinyl monomers and / or radical polymerization initiators are not used. The resin component is not sufficiently compatible with the polypropylene resin component.

However, in the modified propylene resin produced by the production method of the present invention, the polyphenylene ether resin component is sufficiently compatible with the polypropylene resin component and has suitable heat resistance,
The kneading of the polyphenylene ether-based resin component does not lower the foamability and does not impair the mechanical properties.

The polypropylene resin thus obtained has a high cell wall strength during foaming, so the cell wall is not easily broken during foaming.

By foaming such a modified polypropylene resin, a foam having a high closed cell rate, a low density, an excellent appearance, suitable heat resistance, and suitable mechanical properties. You can get your body.

The polypropylene resin before modification which can be used in the present invention is a homopolymer of propylene, a block copolymer of propylene and other monomers, or a random copolymer of propylene and other monomers. A crystalline polymer such as a coalesced product is preferable, and the polypropylene homopolymer is preferable from the viewpoint of high rigidity and low cost, and the propylene and other monomers in terms of both high rigidity and high impact resistance. Block copolymers with the body are preferred. If the polypropylene resin before graft copolymerization is a block copolymer of propylene and other monomers or a random copolymer of propylene and other monomers, the high crystalline characteristic of polypropylene resin From the viewpoint of maintaining the properties, high rigidity and good chemical resistance, the propylene monomer component contained is preferably 75% by weight or more, and more preferably 90% by weight or more of the whole.

In the unmodified polypropylene resin, other monomers copolymerizable with propylene include:
One or more monomers selected from the group consisting of ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer. Also,
This monomer is preferably an ethylene, α-olefin or diene-based monomer because it is easily copolymerized with propylene and is inexpensive.

Examples of the above-mentioned α-olefin copolymerizable with propylene include butene-1, isobutene, pentene-1,3-methyl-butene-1, hexene-1,3-.
Methyl-pentene-1, 4-methyl-pentene-1,
Α-olefins having 4 to 12 carbon atoms, such as 3,4-dimethyl-butene-1, heptene-1, 3-methyl-hexene-1, octene-1, and decene-1. Examples of the cyclic olefin copolymerizable with propylene include cyclopentene, norbornene, 1,4.
5,8-Dimethano-1,2,3,4,4a, 8,8a-
6-octahydronaphthalene and the like. Also,
Examples of the diene-based monomer copolymerizable with propylene include 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7- Methyl-1,6-octadiene and the like can be mentioned. Further, examples of the vinyl monomer copolymerizable with the above-mentioned propylene include vinyl chloride,
Examples thereof include vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, maleic anhydride and the like.

Of these monomers, ethylene or butene-1 is more preferable because it is inexpensive.

The molecular weight (weight average molecular weight) of the polypropylene resin before graft copolymerization is preferably in the range of 50,000 to 2,000,000 from the viewpoint of easy availability, and 10 from the viewpoint of low cost. More preferably, it is in the range of 10,000 to 1,000,000.

Examples of the polyphenylene ether resin that can be used in the present invention include poly (2,6-dimethylphenylene-1,4-ether) and poly (2-methyl-6-).
Ethylphenylene-1,4-ether), poly (2,6)
-Diethylphenylene-1,4-ether), poly (2
-Methyl-6-n-propylphenylene-1,4-ether), poly (2-methyl-6-chlorophenylene-
1,4-ether), poly (2-methyl-6-bromophenylene-1,4-ether), poly (2-ethyl-6)
-Chlorphenylene-1,4-ether) and the like. A modified polyphenylene ether resin obtained by adding a polystyrene resin to a polyphenylene ether resin is also suitably used as the polyphenylene ether resin usable in the present invention.

The polymer molecular weight (weight average molecular weight) of the polyphenylene ether resin is preferably in the range of 10,000 to 200,000 from the viewpoint of easy availability.

The addition amount of the polyphenylene ether resin improves the foamability and heat resistance, and does not impair the original suitable properties of the polypropylene resin.
To 100 parts by weight of polypropylene resin before modification,
The amount is preferably 0.1 to 50 parts by weight, more preferably 1 to 30 parts by weight.

The polypropylene resin and polyphenylene ether resin before graft copolymerization may be in the form of particles or pellets, and the size and shape thereof are not particularly limited. .

Examples of the aromatic vinyl monomer that can be used in the present invention include styrene; o-methylstyrene and m.
-Methylstyrene such as methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, dimethylstyrene and trimethylstyrene; α-chlorostyrene, β-chlorostyrene, o-chlorostyrene, m-
Chlorostyrene such as chlorostyrene, p-chlorostyrene, dichlorostyrene and trichlorostyrene; bromostyrene such as o-bromostyrene, m-bromostyrene, p-bromostyrene, dibromostyrene and tribromostyrene; o-fluorostyrene, m -Fluorostyrene such as fluorostyrene, p-fluorostyrene, difluorostyrene and trifluorostyrene; nitrostyrene such as o-nitrostyrene, m-nitrostyrene, p-nitrostyrene, dinitrostyrene and trinitrostyrene; o-hydroxystyrene , Vinylphenol such as m-hydroxystyrene, p-hydroxystyrene, dihydroxystyrene and trihydroxystyrene; o-divinylbenzene, m-divinylbenzene, p
-Divinylbenzene such as divinylbenzene; one or more kinds of isopropenylstyrene such as o-diisopropenylbenzene, m-diisopropenylbenzene and p-diisopropenylbenzene. Of these, methylstyrene such as styrene, α-methylstyrene, and p-methylstyrene, divinylbenzene, or a mixture of divinylbenzene isomers are preferable because they are inexpensive.

The amount of the aromatic vinyl monomer added is 0.1% based on 100 parts by weight of the polypropylene resin.
It is preferably 1 to 50 parts by weight, particularly 0.1 to 30 parts by weight, in the modified polypropylene resin, because the compatibility between the polypropylene resin component and the polyphenylene ether resin component is suitably improved.

When the amount of the aromatic vinyl monomer added is less than the above range, the effect of improving the foamability tends to be insufficient, while when it is more than the above range, a large amount of radical polymerization is performed. It tends to be a cost disadvantage because of the need for an initiator.

The aromatic vinyl monomer may be used in combination with the aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer.

Other vinyl monomers copolymerizable with the aromatic vinyl monomer include, for example, vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile,
Acrylamide, methacrylamide, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride,
Acrylic acid esters such as metal acrylates, metal methacrylates, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, glycyl acrylate; methyl methacrylate, ethyl methacrylate, Butyl methacrylate,
Examples thereof include methacrylic acid esters such as 2-ethylhexyl methacrylate, stearyl methacrylate, and glycyl methacrylate.

When the aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer are used in combination, the aromatic vinyl monomer is added to 100 parts by weight of the aromatic vinyl monomer. It is preferable that another vinyl monomer copolymerizable with the aromatic vinyl monomer is used in an amount of less than 100 parts by weight.
It is more preferable to use together less than 75 parts by weight. If the amount of the other vinyl monomer copolymerizable with the aromatic vinyl monomer exceeds the above range, it tends to be impossible to obtain a foam having a suitable shape and appearance.

As the radical polymerization initiator, a peroxide or an azo compound is generally mentioned. In the present invention, a compound such as a radical polymerization initiator having a hydrogen abstraction ability with respect to the polymer molecule of the polypropylene resin. The existence of is necessary.

Examples of the radical polymerization initiator include peroxides and azo compounds. Specific examples thereof include ketone peroxides such as methyl ethyl ketone peroxide and methyl acetoacetate peroxide;
1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) Peroxy ketals such as valerate, 2,2-bis (t-butylperoxy) butane; permethane hydroperoxide, 1,1,
3,3-tetramethylbutyl hydroperoxide,
Hydroperoxides such as diisopropylbenzene hydroperoxide and cumene hydroperoxide; dicumyl peroxide, 2,5-dimethyl-2,
5-di (t-butylperoxy) hexane, α, α′-
Bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexyne-3 and other dialkyl peroxides; benzoyl peroxide and other diacyl peroxides; di (3-methyl-3-methoxybutyl) peroxydicarbonate, di-2-methoxybutylperoxydicarbonate, etc. Peroxydicarbonate; t-butylperoxyoctate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexanoate, t- Butyl peroxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butyl peroxyacetate, t-butyl peroxybenzoate, di-t-
Organic peroxides such as peroxyesters such as butyl peroxyisophthalate are exemplified. Of these,
Particularly, those having high hydrogen abstracting ability are preferable. For example, 1,1-bis (t-butylperoxy) -3,3,5-
Such as trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, and 2,2-bis (t-butylperoxy) butane; Peroxyketal; dicumyl peroxide, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexane, α, α
'-Bis (t-butylperoxy-m-isopropyl)
Benzene, t-butyl cumyl peroxide, di-t-
Dialkyl peroxides such as butyl peroxide and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; diacyl peroxides such as benzoyl peroxide; t-butylperoxy octate, t- Butyl peroxyisobutyrate, t-butyl peroxylaurate, t-butyl peroxy-3,
5,5-trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-
One or more kinds of peroxyesters such as 2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate. To be

The amount of the radical polymerization initiator added is based on 100 parts by weight of the polypropylene resin before modification because the melt viscosity of the modified polypropylene resin does not excessively decrease and it is economical. , Preferably 0.01 to 5 parts by weight, more preferably 0.1 to 0.5 parts by weight.

When the amount of the radical polymerization initiator added is less than the above range, the modifying effect tends not to be sufficiently obtained, while when it is more than the above range, it has a suitable shape and appearance. Foams tend not to be obtained.

If necessary, a resin or rubber other than the polyphenylene ether resin may be added to the polypropylene resin before modification as long as the effect of the present invention is not impaired. Examples of the resin or rubber other than the polyphenylene ether resin include polyethylene; polyα-olefins such as polybutene-1, polyisobutene, polypentene-1, and polymethylpentene-1; ethylene having a propylene content of less than 75% by weight; Ethylene or α-olefin / α-olefin copolymer such as propylene copolymer, ethylene / butene-1 copolymer, propylene / butene-1 copolymer having a propylene content of less than 75% by weight; Less than 75 wt% ethylene / propylene / 5-ethylidene-2-norbornene copolymer or other ethylene or α-olefin / α-olefin / diene monomer copolymer; ethylene / vinyl chloride copolymer, ethylene / Vinylidene chloride copolymer, ethylene / acrylonitrile copolymer Polymer, ethylene / methacrylonitrile copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylamide copolymer, ethylene / methacrylamide copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, Ethylene / maleic acid copolymer, ethylene / ethyl acrylate copolymer, ethylene / butyl acrylate copolymer, ethylene /
Methyl methacrylate copolymer, ethylene / maleic anhydride copolymer, ethylene / acrylic acid metal salt copolymer, ethylene / methacrylic acid metal salt copolymer, ethylene / styrene copolymer, ethylene / methylstyrene copolymer Ethylene or α-olefin / vinyl monomer copolymer such as ethylene / divinylbenzene copolymer; polydiene copolymer such as polyisobutene, polybutadiene, polyisoprene; vinyl monomer such as styrene / butadiene random copolymer Copolymer / diene-based monomer random copolymer; styrene / butadiene / styrene block copolymer and other vinyl monomers / diene-based monomer / vinyl monomer block copolymer; hydrogenation (styrene / butadiene random Hydrogenation of copolymers etc. (Vinyl monomer / diene monomer random copolymerization ); Hydrogenation (styrene / butadiene / styrene block copolymer) and the like (vinyl monomer / diene monomer / vinyl monomer block copolymer); acrylonitrile / butadiene / styrene copolymer, Vinyl monomer / diene monomer / vinyl monomer graft copolymer such as methyl methacrylate / butadiene / styrene copolymer; polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, polyacrylic acid Vinyl, such as ethyl, poly (butyl acrylate), poly (methyl methacrylate); vinyl chloride / acrylonitrile copolymer, vinyl chloride / vinyl acetate copolymer, acrylonitrile / styrene copolymer, methyl methacrylate / styrene copolymer, etc. And vinyl-based copolymers.

The amount of these other resins or rubbers to be added to the polypropylene resin before modification varies depending on the type of the resin or the type of the rubber and may be within the range not impairing the effects of the present invention as described above. , Usually 25% by weight
It is preferable that it is not more than about.

Further, if necessary, the polypropylene resin before modification may include an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, an optical brightener, and a metal. Stabilizer or cross-linking agent such as soap, antacid adsorbent,
Additives such as a chain transfer agent, a nucleating agent, a lubricant, a plasticizer, a filler, a reinforcing material, a pigment, a dye, a flame retardant and an antistatic agent may be added within a range that does not impair the effects of the present invention.

These unmodified polypropylene resins (which may contain various additive materials) may be in the form of particles or pellets, and their size and shape are not particularly limited. It is not something that will be done.

When the above-mentioned additive material (other resin, rubber, stabilizer and / or additive) is used, this additive material may be added in advance to the polypropylene resin before modification. It may be added when melting the polypropylene resin before modification, or may be added by an appropriate method after melt-kneading.

Mixing of the above-mentioned polypropylene resin (polypropylene resin before modification), polyphenylene ether resin, aromatic vinyl monomer, radical polymerization initiator and other additives added as necessary. The method and the melt-kneading method are not particularly limited, and for example, a polypropylene resin, a polyphenylene ether resin, an aromatic vinyl monomer, a radical polymerization initiator, and other additive materials added as necessary are mixed. After that, it may be melt-kneaded, or after melt-kneading the polypropylene-based resin and the polyphenylene ether-based resin, an aromatic vinyl monomer, a radical polymerization initiator, and other additives to be added as necessary are added thereto. Simultaneously or separately, batch or divided and mixed, melt-kneaded It may be.

The heating temperature at the time of melt kneading is 130 to 4
A temperature of 00 ° C. is preferable because the polypropylene resin is sufficiently melted and is less likely to be thermally decomposed. The time for melt-kneading (time after mixing the radical polymerization initiator and the aromatic vinyl monomer) is generally 1 to 60 minutes.

The melt kneading device is a roll,
Kneader, Banbury mixer, Brabender, kneading machine such as single-screw extruder or twin-screw extruder, horizontal agitator such as twin-screw surface renewing machine or twin-screw multi-disc device or vertical agitator such as double-helical ribbon stirrer An example is an apparatus capable of heating a molecular material to an appropriate temperature and kneading while applying an appropriate shear stress. Of these, an extruder is particularly preferable in terms of productivity. The melt-kneading may be repeated a plurality of times in order to mix the respective materials sufficiently uniformly.

The modified polypropylene resin of the present invention can be produced as described above.

By foaming such a modified polypropylene resin, the foam of the present invention is obtained.

As an example of the method for producing the foam of the present invention, (1)
A method in which a modified polypropylene resin and a foaming agent are melt-kneaded in a melt extruder and then extruded by a melt extruder to obtain a foam, (2) a foaming agent is added to the modified polypropylene resin in a molten state. Or after press fitting,
Examples thereof include a method of obtaining a foam by extruding with a melt extruder.

In the case of the above method (1), a thermal decomposition type foaming agent may be used as the foaming agent. Among them, preferable thermal decomposition type foaming agents include, for example, N, N'-dinitrosopentamethylenetetramine, N, N'-dimethyl-N, N '
-Nitroso-based foaming agents such as dinitrosoterephthalamide; azo-based foaming agents such as azodicarbonamide and barium azodicarboxylic acid; sulfohydrazide-based foaming agents such as p, p'-oxybisbenzenesulfonyl hydrazide and p-toluenesulfonyl semicarbazide 1 type (s) or 2 or more types, such as trihydrazino triazine.

The addition amount (kneading amount) of the above-mentioned foaming agent may be selected depending on the kind of the foaming agent and the target expansion ratio, but is 0.5 with respect to 100 parts by weight of the modified polypropylene resin.
It is preferably in the range of about 100 parts by weight.

In order to control the bubble diameter of the foam to an appropriate size, sodium bicarbonate may be added, if necessary.
A foam nucleating agent such as citric acid or talc may be used in combination. The foam nucleating agent, which is used as necessary, is usually 0.01% with respect to 100 parts by weight of the modified polypropylene resin.
It is used by adding 1 part by weight.

In the case of the method (1), the modified polypropylene resin and the pyrolytic foaming agent are both supplied to a melt extruder, and the foaming agent is pyrolyzed while melt-kneading at an appropriate temperature. A gas is generated by doing so, and the modified polypropylene resin in a molten state containing this gas is discharged from a die, whereby a foam can be molded. The melt-kneading temperature and the melt-kneading time in this method may be appropriately selected depending on the foaming agent and the kneading conditions to be used, and vary depending on the type of the resin. Is usually

In the case of the above method (2), examples of the foaming agent include volatile foaming agents. Among them, preferable volatile foaming agents include propane, butane, pentane, and the like.
Aliphatic hydrocarbons such as hexane and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane,
Dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, Halogenated hydrocarbons such as dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, chloropentafluoroethane, perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen, air; one or two such as water The above is mentioned.

The addition amount (kneading amount) of the foaming agent varies depending on the type of the foaming agent and the target expansion ratio, but is 0.5 to 100 with respect to 100 parts by weight of the modified polypropylene resin.
It is preferably within the range of parts by weight.

Also in this method, a foam nucleating agent such as sodium bicarbonate-citric acid or talc may be used together, if necessary, in order to control the bubble diameter of the foam to an appropriate size. The amount of the foam nucleating agent used, if necessary, is usually the modified polypropylene resin 10
It is preferably 0.01 to 1 part by weight with respect to 0 part by weight.

Further, in the case of the method (2), the modified polypropylene resin is melted in the extruder, the volatile foaming agent is press-fitted into the extruder, and the molten state is maintained while maintaining a high pressure. A kneaded product of the modified polypropylene resin and the volatile foaming agent, which has been kneaded with a high-quality polypropylene resin and sufficiently kneaded, is discharged from a die to form a foam. The melt-kneading temperature and the melt-kneading time in this method may be appropriately selected according to the foaming agent used and the kneading conditions, and the melt-kneading temperature is 130 to 300 ° C. and the melt-kneading time is 1 to 120 minutes, although it depends on the type of resin. It is usually

The foam according to the present invention has a density of 0.01 to 0.5 g / cm 3 from the viewpoint that it is suitable for its lightness, heat insulation, buffering against external stress and compressive strength.
³ is preferable and 0.015 to 0.2 g / cm ³
Is more preferable.

In addition, the foam of the present invention has a closed cell ratio of 50% or more from the viewpoint that it has suitable heat resistance, good cushioning against external force, and suitable compressive strength. It is preferably 70% or more, and more preferably 70% or more.

Further, in the method for producing a foam according to the present invention, the shape which can be produced is a plate shape such as a sheet shape or a board shape, a hollow shape such as a tube shape or a bag shape, a cylindrical shape, an elliptic cylinder shape or a prismatic shape. Various shapes such as a columnar shape such as a strand shape can be cited, and a plate-like shape has a wide range of uses. As the plate-shaped foam, for example, a sheet-shaped foam capable of secondary molding that can be used for vacuum molding or the like is preferable because of its high closed cell rate or small drawdown during secondary molding. It is used as a relatively thick board-like foam used as a cushioning material or a core material, and is preferably used because of its high closed cell ratio or low density.

Next, the present invention will be described in detail based on examples, but the present invention is not limited to such examples.

Example 1 100 parts by weight of propylene homopolymer (Sumitomo Chemical Co., Ltd., Nobrene D501, melt flow index 0.4 g / 10 minutes at 230 ° C.) and modified polyphenylene ether (Japan GE Plastics Co., Ltd.) Manufactured by Noryl MX-4740, polystyrene content about 40% by weight) 1
0 parts by weight and styrene (manufactured by Wako Pure Chemical Industries, Ltd., special grade) 5
Parts by weight and α, α′-bis (t
-Butylperoxy-m-isopropyl) benzene (Nippon Oil & Fats Co., Ltd., Perbutyl P, 1 minute half-life temperature 17
(5 ° C.) 0.5 part by weight is melt-kneaded using a twin-screw extruder (LABOTEX) manufactured by Japan Steel Works, Ltd., and melt-extruded to obtain a rod-shaped modified polypropylene resin having a diameter of 4 mm. A molded product was obtained. The rod-shaped modified polypropylene resin molded product was shredded to a thickness of 3 mm to obtain modified polypropylene resin pellets.

The twin-screw extruder was of the same-direction, twin-screw type, and had a cylinder hole diameter of 32 mmφ and a maximum screw effective length (L / D) of 25.5. The twin-screw extruder was heated at a set temperature of the cylinder section of 200 ° C. and at a set temperature of the feed section of 160 ° C., and the rotation speed of the screw was set to 100 rpm for each axis.

Using this modified polypropylene resin pellet, a round rod-shaped foam was produced by the following method.

Modified polypropylene resin pellets 10
0 parts by weight, blended oil (Koshigaya Chemical Co., Ltd., Super Ease) 0.05 parts by weight, and sodium bicarbonate-citric acid (Nagawa Kasei Co., Ltd., Cerbon SG / IC) as a foam nucleating agent. 1 part by weight was mixed for 15 minutes using a ribbon blender. This mixture was supplied to a tandem extruder (first-stage extruder cylinder diameter 40 mmφ, second-stage extruder cylinder diameter 50 mmφ), melted at 230 ° C. in the first-stage extruder, and then used as a foaming agent. 8 parts by weight of butane gas (isotan butane gas; normal butane / isobutane mixing ratio 15/85 by weight) was kneaded with 100 parts by weight of the modified polypropylene resin, and kneaded in the second stage extruder. The resin was cooled to a temperature of 150 ° C. and extruded from a circular die having an orifice of 6 mmφ × 25 mm to form a round rod-shaped foam.

The density, the expansion ratio and the closed cell ratio of the obtained rod-shaped foam were measured by the following methods, and the appearance was visually evaluated by the following evaluation criteria.

Density of foam: Calculated from the weight and the volume obtained by the submersion method.

Closed cell ratio: Using a multi-pycnometer (product name, Yuasa Ionics Co., Ltd.), ASTM D
-Measurement according to 856.

Evaluation Criteria for Appearance: Good: No unfoamed part, fluff, or wrinkle is observed. X: An unfoamed part, fluff, and wrinkles are seen.

As a result, the density was 0.082 g / cm ³ , the closed cell ratio was 78%, and the appearance was evaluated as ◯.

Examples 2 to 5 The types and amounts of polypropylene resin, polyphenylene ether resin, aromatic vinyl monomer, and radical polymerization initiator supplied to the twin-screw extruder were changed as shown in Table 1. Others were the same as in Example 1 to obtain modified polypropylene resin pellets.

Using this modified polypropylene resin pellet, a round rod-shaped foam was obtained in the same manner as in Example 1.

The density, closed cell ratio and appearance of this round rod-shaped foam were evaluated in the same manner as in Example 1. Table 2 shows the results
Shown in

Comparative Example 1 A propylene homopolymer (Nobrene D501, manufactured by Sumitomo Chemical Co., Ltd.) was not modified, but this propylene homopolymer was used instead of using the modified polypropylene resin pellets. A round rod-shaped foam was produced according to the method for producing a round rod-shaped foam of 1.

The density, closed cell rate and appearance of this round rod-shaped foam were evaluated in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 2 Styrene which is an aromatic vinyl monomer and α, α'-bis (di-t-butylperoxy-) which is a radical polymerization initiator.
A round rod-shaped foam was produced in the same manner as in Example 1 except that m-isopropyl) benzene was not added.

The density, closed cell ratio and appearance of this round rod-shaped foam were evaluated in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 3 A round rod-shaped foam was produced in the same manner as in Example 1 except that the modified polyphenylene ether which was a polyphenylene ether resin was not used.

The density, closed cell ratio and appearance of this round bar foam were evaluated in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 4 Melt kneading was carried out in the same manner as in Example 1 except that styrene which was an aromatic vinyl monomer was not added, but the resin had a low viscosity and could not be formed into a strand.

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[Table 1]

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[Table 2]

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[Table 3]

The foams produced by using the modified polypropylene resin in the examples have a low density, a high closed cell ratio and an excellent appearance, whereas the foams in the comparative examples have a high density and a closed cell. It turns out that the rate is low. Also,
A foam produced by using a resin obtained by melt-kneading a polyphenylene ether resin with a polypropylene resin before modification has a foam density and a foaming ratio similar to those of the modified polypropylene resin of the present invention. However, it can be seen that the closed cell ratio and the appearance are poor. Further, the polypropylene resin before modification, without adding the polyphenylene ether resin, only the aromatic vinyl monomer and the radical polymerization initiator was added and the foam produced using the resin kneaded It is understood that although the property (a resin having a low density, a high closed cell ratio and a good appearance and having a good foamability is a resin which can be molded into a good appearance) is improved, the effect is low.

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The polypropylene resin, the polyphenylene ether resin, the aromatic vinyl monomer and the radical polymerization initiator are melt-kneaded to form a modified polypropylene resin, which has a low density and a closed cell structure. A foam having a high rate, a beautiful appearance, and excellent heat resistance can be obtained.

Claims (4)

[Claims] 1. A foam made of a modified polypropylene resin obtained by melt-kneading a polypropylene resin, a polyphenylene ether resin, an aromatic vinyl monomer and a radical polymerization initiator. 2. The foam according to claim 1, wherein the aromatic vinyl monomer is one or more selected from the group consisting of styrene, methylstyrene and divinylbenzene. 3. The foam according to claim 1, wherein the radical polymerization initiator is one or more selected from the group consisting of peroxyketal, dialkyl peroxide, diacyl peroxide and peroxy ester. . 4. The method for producing a foam according to claim 1, wherein the modified polypropylene resin and the foaming agent are melt-kneaded and then extruded to foam.