JPH10219014A - Foam composed of modified polypropylene-based resin composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-density foam high in closed cell ratio, beautiful in appearance and excellent in adhesiveness and coating performances. SOLUTION: This foam composed of a modified polypropylene-based resin composition is obtained by compounding a polypropylene-based resin with at least one monomer selected from among an aromatic vinyl monomer, an isoprene monomer and 1,3-butadiene-based monomer, an unsaturated carboxylic acid monomer, a radical polymerization initiator and optionally a metal compound in a molten state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a foam comprising a modified polypropylene resin composition and a method for producing the foam. More specifically, with a polypropylene resin,
Aromatic vinyl monomer, isoprene monomer and 1,3-
Modified polypropylene resin composition obtained by melting and kneading at least one monomer selected from butadiene monomers, an unsaturated carboxylic acid monomer, and a radical polymerization initiator, or the modified polypropylene resin composition The resin composition is made of a modified polypropylene resin composition obtained by further adding at least one metal compound selected from a metal salt and a metal oxide, and has a high closed cell ratio, a low density, and a beautiful appearance. Yes, foam with excellent adhesion and paintability,
And a method for producing the foam.

[0002]

2. Description of the Related Art A foam made of a thermoplastic resin is generally used widely as a heat insulating material, a cushioning material, a core material, a food container, etc. because of its light weight and good heat insulating property and buffering property of external stress. ing. Above all, a foam made of a polypropylene-based resin is preferably used as a cushioning material because of its good chemical resistance, impact resistance and heat resistance.

[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 more easily scattered to the outside than the air bubbles. Furthermore, since this resin does not have a polar group, the obtained foam lacks paintability and adhesiveness. Therefore, it has been difficult to obtain a low-density foam having excellent appearance, excellent adhesiveness and coatability, high closed cell ratio and high density by foaming a polypropylene resin.

As a method of improving the foaming property of a polypropylene resin, for example, a method of adding a crosslinking aid to a polypropylene resin to crosslink its molecules (for example, see Japanese Patent Publication No. 45-4020), a method of improving the polypropylene resin, (See, for example, Japanese Patent Publication No. 44-2574) and a method in which polystyrene is blended with a polypropylene resin and foamed (for example, Japanese Patent Publication No. 43-13375).
Reference).

However, even if these methods are used,
The effect of improving the 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 radical polymerization initiator,
Kneading styrene monomer and foaming agent in an extruder,
A method of producing a foam by extruding while reacting is disclosed, but nothing is disclosed about polypropylene.

As described above, the foaming property of the polypropylene resin is sufficiently improved, and the foaming ratio is high by using the resin.
At present, no method has been found for producing a foam having a high closed cell ratio, a low density, and excellent adhesiveness and coatability.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a modified polypropylene resin composition having improved foaming properties, which has a high expansion ratio, a high closed cell ratio, a low density,
An object of the present invention is to provide a foam having a beautiful appearance and excellent adhesiveness and paintability.

[0010]

The present invention provides a polypropylene resin, at least one monomer selected from an aromatic vinyl monomer, an isoprene monomer and a 1,3-butadiene monomer. The present invention relates to a foam comprising a modified polypropylene resin composition obtained by melt-kneading an unsaturated carboxylic acid monomer and a radical polymerization initiator.

[0011] The present invention also relates to a foaming method comprising a modified polypropylene resin composition obtained by adding at least one metal compound selected from metal salts and metal oxides to the modified polypropylene resin composition. About the body.

[0012] The present invention also relates to a method for producing a foam which is obtained by melt-kneading the above-mentioned modified polypropylene resin composition and a foaming agent and then extruding and foaming.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a polypropylene resin, an aromatic vinyl monomer, an isoprene monomer and 1,
At least one monomer selected from a 3-butadiene monomer, an unsaturated carboxylic acid monomer, and a radical polymerization initiator at a temperature at which the polypropylene-based resin melts;
And under a temperature at which the radical polymerization initiator can decompose,
The foaming property of the modified polypropylene resin composition obtained by kneading is significantly improved with respect to the foaming property of the polypropylene resin before melt-kneading (hereinafter sometimes referred to as “raw polypropylene resin”). By foaming this modified polypropylene resin composition,
The present inventors have found that a foam having a high closed cell ratio, a low density, a beautiful appearance, and excellent paintability and adhesiveness can be obtained, thereby completing the present invention.

Aromatic vinyl monomers and isoprene monomers,
By melting and kneading the 1,3-butadiene monomer with the radical polymerization initiator and reacting them, it is possible to improve the foaming property of the raw material polypropylene-based resin, but the adhesiveness and coatability are not improved. However, when reacting, by mixing an unsaturated carboxylic acid monomer together with an aromatic vinyl monomer, an isoprene monomer, and a 1,3-butadiene monomer, adhesiveness and coatability are improved. Not only that, the effect of improving foamability is further enhanced.

The modified polypropylene resin composition thus obtained has a high cell wall strength at the time of foaming.
The foam walls do not collapse easily when foamed.

By foaming such a modified polypropylene resin composition, the closed cell ratio is high, the density is low, the appearance is excellent, the adhesiveness and coating property are good, A foam having mechanical properties can be obtained.

Examples of the starting polypropylene resin usable in the present invention include propylene homopolymers, block copolymers of propylene and other polymers, and random copolymers of propylene and other monomers. Polymers are preferred, and the rigidity is high, and the polypropylene homopolymer is preferable in that it is inexpensive, and the rigidity and impact resistance are particularly high, and the block of the propylene and other monomers is preferable. Copolymers are preferred. In addition, a random copolymer of propylene and another monomer is preferable in that the foamability can be improved with a small amount of a radical polymerization initiator. When the raw polypropylene resin is a block copolymer of propylene and other monomers or a random copolymer of propylene and other monomers, the high crystallinity and high rigidity characteristic of polypropylene resins From the viewpoint of maintaining good chemical resistance, the content of the propylene monomer component is preferably at least 75% by weight, more preferably at least 90% by weight.

In the raw material polypropylene resin,
As other monomers copolymerizable with propylene, one or more selected from the group consisting of ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer Monomers.

Examples of the α-olefin copolymerizable with propylene include butene-1, isobutene, pentene-1,3-methyl-butene-1, hexene-1,3-hexene.
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 can be mentioned. Examples of the diene monomer copolymerizable with propylene include 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, and methyl-
Examples thereof include 1,4-hexadiene and 7-methyl-1,6-octadiene. Examples of the vinyl monomer copolymerizable with the propylene include vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate And maleic anhydride.

Of these, ethylene, α-olefin or diene monomers are preferred because they are easily copolymerized with propylene and are inexpensive.
1 is more preferable in that it is inexpensive.

The molecular weight (weight average molecular weight) of the raw material polypropylene resin is preferably in the range of 50,000 to 2,000,000 from the viewpoint of easy availability, and from 100,000 to 1,000,000 from the viewpoint of low cost. More preferably, it is within the range.

In the present invention, the aromatic vinyl monomer melt-kneaded with the raw material polypropylene resin includes, for example, styrene; o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methyl Methylstyrene such as styrene, dimethylstyrene and trimethylstyrene; chlorostyrene such as α-chlorostyrene, β-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, dichlorostyrene and trichlorostyrene; o-bromo Bromostyrene such as styrene, m-bromostyrene, p-bromostyrene, dibromostyrene, tribromostyrene; o-fluorostyrene, m-fluorostyrene, p
-Fluorostyrene such as fluorostyrene, difluorostyrene and trifluorostyrene; nitrostyrene such as o-nitrostyrene, m-nitrostyrene, p-nitrostyrene, dinitrostyrene and trinitrostyrene; o-hydroxystyrene, m-hydroxystyrene , P-hydroxystyrene, dihydroxystyrene,
Vinylphenol such as trihydroxystyrene; o-
Divinylbenzene such as divinylbenzene, m-divinylbenzene and p-divinylbenzene; one or more kinds such as isopropenylstyrene such as o-diisopropenylbenzene, m-diisopropenylbenzene and p-diisopropenylbenzene Is raised. Of these, methylstyrene such as styrene, α-methylstyrene and p-methylstyrene, divinylbenzene monomer or a mixture of divinylbenzene isomers are preferred in that they are inexpensive.

The aromatic vinyl monomer, isoprene monomer and 1,3-butadiene monomer may be used alone or in combination. When combined, the use ratio is arbitrary. The amount of the monomer (or monomer mixture) is 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the raw material polypropylene resin. The system resin composition is preferable because the effect of improving foamability is remarkable and economical.

The unsaturated carboxylic acid monomer to be melt-kneaded in the present invention includes, for example, acrylic acid, cis-crotonic acid, trans-crotonic acid, cis-ethylacrylic acid, trans-ethylacrylic acid, cis-cinnamon Acid, trans-cinnamic acid, methacrylic acid, fumaric acid,
One or more of maleic acid, maleic anhydride, itaconic acid, itaconic anhydride and the like can be mentioned. Of these, acrylic acid, methacrylic acid and maleic anhydride are preferred in that they are inexpensive.

The amount of the unsaturated carboxylic acid monomer is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the starting polypropylene resin.

The amount of the unsaturated carboxylic acid monomer added is
When the amount is less than the above range, in the modified polypropylene resin composition, the foaming property, the adhesive property, and the coatability tend to be not sufficiently improved, while when the amount is more than the above range, the composition has a suitable shape and appearance. There is a tendency that foam cannot be obtained.

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

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-butyl peroxide, 2,5-dimethyl-2,5-di (t
Dialkyl peroxides such as -butylperoxy) hexine-3; diacyl peroxides such as benzoyl peroxide; di (3-methyl-3-methoxybutyl) peroxydicarbonate, di-2-methoxybutylperoxydicarbonate and the like T-butyl peroxy octate, t-butyl peroxy isobutyrate, t-butyl peroxy laurate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy octanoate Butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, 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-butylcumyl peroxide, di-
t-butyl peroxide, 2,5-dimethyl-2,5
Dialkyl peroxides such as di- (t-butylperoxy) hexine-3; diacyl peroxides such as benzoyl peroxide; t-butylperoxyoctate, t-butylperoxyisobutyrate, and t-butylperoxylau. Rate, t-butylperoxy-
3,5,5-trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-
One or more of peroxyesters such as butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate are exemplified.

The amount of the radical polymerization initiator to be added is 100 parts by weight based on 100 parts by weight of the starting polypropylene resin, since the melt viscosity of the modified polypropylene resin composition is not excessively reduced and is economical. It is preferably in the range of 0.01 to 5 parts by weight, more preferably in the range of 0.01 to 1 part by weight.

When the amount of the radical polymerization initiator is smaller than the above range, the modifying effect tends to be insufficient, while when the amount is larger than the above range, a suitable shape and appearance are obtained. There is a tendency that foam cannot be obtained.

In the present invention, a polypropylene resin, an aromatic vinyl monomer, an isoprene monomer and 1,
A modified polypropylene resin composition obtained by melt-kneading at least one monomer selected from 3-butadiene monomers, an unsaturated carboxylic acid monomer, and a radical polymerization initiator, and further adding a metal salt And the addition of a metal compound selected from the group consisting of metal oxides further improves the foaming effect.

As the metal in the metal compound, for example, sodium, potassium, lithium, silver, mercury,
Copper, magnesium, calcium, strontium, barium, cadmium, tin, lead, iron, cobalt, nickel, zinc, aluminum, etc .; metal salts such as acetates, carbonates, stearate, and oxidation of these metals; One or two or more of the products are mentioned. Of these, oxides or acetates of zinc, magnesium, sodium and aluminum are preferred in that they are inexpensive.

When compounded with this metal compound, the compounding amount is preferably not more than 50 parts by weight, particularly preferably not more than 10 parts by weight, based on 100 parts by weight of the starting polypropylene resin. The lower limit is not particularly limited.
It is preferably at least 1 part by weight.

When the amount of the metal compound is larger than the above range, the foam of the obtained foam may be finely divided,
Crystals are deposited and deposited in the vicinity of the die lip, and there is a tendency that a foam having a suitable shape and appearance cannot be obtained.

If necessary, another resin or rubber may be added to the raw material polypropylene-based resin within a range that does not impair the effects of the present invention. Examples of the other resin or rubber include polyethylene; poly-α-olefins such as polybutene-1, polyisobutene, polypentene-1 and polymethylpentene-1;
Less than 5% by weight of ethylene or α-olefin / α-olefin copolymer such as ethylene / propylene copolymer, ethylene / butene-1 copolymer and propylene content of less than 75% by weight of propylene / butene-1 copolymer. Polymer; ethylene or α-olefin / α-olefin / diene monomer copolymer such as ethylene / propylene / 5-ethylidene-2-norbornene copolymer having a propylene content of less than 75% by weight; ethylene / chloride Vinyl copolymer,
Ethylene / vinylidene chloride copolymer, ethylene / acrylonitrile copolymer, ethylene / methacrylonitrile copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylamide copolymer, ethylene / methacrylamide copolymer, ethylene / acryl 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 / acrylate metal salt copolymer, ethylene / methacrylic acid Ethylene or α-olefin such as metal salt copolymer, ethylene / styrene copolymer, ethylene / methylstyrene copolymer, ethylene / divinylbenzene copolymer;
Vinyl monomer copolymer; polydiene copolymer such as polyisobutene, polybutadiene, polyisoprene; vinyl monomer / diene monomer random copolymer such as styrene / butadiene random copolymer; styrene / butadiene / Vinyl monomers such as styrene block copolymers /
Diene monomer / vinyl monomer block copolymer; hydrogenation (vinyl monomer / diene monomer random copolymer) such as hydrogenation (styrene / butadiene random copolymer); hydrogenation ( Hydrogenation (vinyl monomer / diene-based monomer / vinyl monomer block copolymer) such as styrene / butadiene / styrene block copolymer; acrylonitrile / butadiene / styrene copolymer, methyl methacrylate / butadiene / Vinyl monomers such as styrene copolymers / diene monomers / vinyl monomer graft copolymers;
Vinyl polymers such as polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, polyethyl acrylate, polybutyl acrylate, and polymethyl methacrylate; vinyl chloride / acrylonitrile copolymer, vinyl chloride / vinyl acetate copolymer And vinyl copolymers such as acrylonitrile / styrene copolymer and methyl methacrylate / styrene copolymer.

The amount of the other resin or rubber to be added to the starting polypropylene resin depends on the type of the resin or the type of rubber, and may be within the range not impairing the effects of the present invention as described above. It is preferable that the content is not more than about weight%.

Further, if necessary, an antioxidant, a metal deactivator, a phosphorus-based processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent brightener, a metal soap, an antacid Additives such as stabilizers or cross-linking agents such as adsorbents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, and antistatic agents do not impair the effects of the present invention. You may add in the range.

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

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

Further, the raw material polypropylene-based resin,
Mixing of aromatic vinyl monomer, isoprene monomer, 1,3-butadiene monomer, unsaturated carboxylic acid monomer, radical polymerization initiator, metal compound added as required, and other additive materials The method and the melt-kneading method are not particularly limited, and they may be mixed simultaneously or separately, collectively or separately, and then melt-kneaded.

The heating temperature during the melt-kneading is from 130 to 4
The temperature of 00 ° C. is preferred in that the raw material polypropylene resin is sufficiently melted and hardly thermally decomposed. The time for melt-kneading is generally 1 to 60 minutes.

The melt kneading apparatus includes a roll,
Kneaders such as co-kneaders, Banbury mixers, Brabenders, single-screw extruders or twin-screw extruders, horizontal stirrers such as twin-screw surface renewers or twin-screw multi-disc units, or vertical stirrers such as Budal helical ribbon stirrers An apparatus such as a stirrer capable of heating a polymer material to an appropriate temperature and mixing while giving an appropriate shear stress is exemplified. Of these, extruders are particularly preferred from the viewpoint of productivity. Further, the melt-kneading may be repeated a plurality of times in order to sufficiently uniformly mix the respective materials.

Thus, the modified polypropylene resin composition of the present invention can be produced, and the foam of the present invention can be obtained by foaming the modified polypropylene resin composition.

As an example of the method for producing the foam of the present invention, (1)
A method in which a modified polypropylene resin composition and a foaming agent are melt-kneaded in a melt extruder and then extruded by a melt extruder to obtain a foam. (2) A method in which a molten modified polypropylene resin composition is obtained. After adding or press-fitting a foaming agent, a method of extruding with a melt extruder to obtain a foam may be used.

In the case of the above-mentioned method (1), as the foaming agent, a pyrolytic foaming agent and the like can be mentioned, and among these, preferable examples of the pyrolytic foaming agent are N, N'-dinitrosopentamethylenetetramine, N, N N'-dimethyl-N, N '
A nitroso foaming agent such as dinitrosoterephthalamide; an azo foaming agent such as azodicarbonamide and barium azodicarboxylate; a sulfohydrazide foaming agent such as p, p'-oxybisbenzenesulfonylhydrazide and p-toluenesulfonylsemicarbazide. One or more of trihydrazinotriazine and the like;

The addition amount (kneading amount) of the foaming agent may be selected depending on the type of the foaming agent and the target expansion ratio, and is based on 100 parts by weight of the modified polypropylene resin composition.
It is preferably in the range of 0.5 to 100 parts by weight.

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

In the case of the above method (1), the modified polypropylene resin composition and the pyrolytic foaming agent are both supplied to a melt extruder, and the foaming agent is melted and kneaded at an appropriate temperature. A gas can be generated by thermal decomposition, and the modified polypropylene resin composition in a molten state containing the gas can be discharged from a die to form a foam. The melt-kneading temperature and the melt-kneading time in this method may be appropriately selected depending on the foaming agent used and the kneading conditions, and vary depending on the type of the resin.
It is usually 0 minutes.

In the case of the above-mentioned method (2), volatile foaming agents and the like can be mentioned as foaming agents. Among them, preferred volatile foaming agents are, for example, 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 and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen and air; one or two kinds of water and the like 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 parts by weight of the modified polypropylene resin composition.
Preferably it is in the range of 100 parts by weight.

Also in this method, a foam nucleating agent such as sodium bicarbonate-citric acid or talc may be used in combination, if necessary, in order to control the cell diameter of the foam to an appropriate size. Usually, the addition amount of the foaming nucleating agent used as needed is preferably 0.01 to 1 part by weight based on 100 parts by weight of the modified polypropylene resin composition.

In the case of the above method (2), the modified polypropylene resin composition is melted in an extruder, the volatile foaming agent is press-fitted into the extruder, and the molten foaming agent is maintained at a high pressure. The modified polypropylene resin composition is kneaded, and a kneaded mixture of the sufficiently kneaded modified polypropylene resin composition and a volatile foaming agent 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 depending on the foaming agent used and the kneading conditions, and vary depending on the type of the resin, but the melt-kneading temperature is 130 to 300 ° C., and the melt-kneading time is 1 to 120 minutes. Is usually

The density of the foam of the present invention is preferably from 10 to 500 kg / m ³ , from the viewpoint that the foam is suitable for light weight, heat insulation, buffering of external stress or compressive strength. More preferably, it is で 300 kg / m ³ .

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

In the method for producing a foam according to the present invention, the shapes that can be produced include a plate shape such as a sheet shape and a board shape, a hollow shape such as a tube shape and a bag shape, a columnar shape, an elliptical columnar shape, a prismatic shape, and the like. There are various shapes such as a column shape such as a strand shape, and a plate shape has a wide range of uses. As the plate-like foam, for example, as a sheet-like foam that can be formed into a secondary form that can be used for vacuum forming or the like, the closed cell rate is high, and the drawdown at the time of the secondary molding is small, and it is preferable. Used. In addition, a relatively thick board-shaped foam used as a cushioning material or a core material is suitably used because it has a high closed-cell rate and a low density.

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 100 parts by weight of a propylene homopolymer (melt flow index at 230 ° C .: 0.4 g / 10 minutes), 10 parts by weight of styrene monomer, 1.0 part by weight of acrylic acid monomer,
0.5 parts by weight of α, α′-bis (t-butylperoxy-m-isopropyl) benzene (1 minute half-life temperature: 175 ° C.) as a radical polymerization initiator was manufactured by Nippon Steel Works, Ltd. The mixture was melt-kneaded using an extruder (LABOTEX) and melt-extruded to obtain a molded product of a rod-shaped modified polypropylene resin composition having a diameter of 4 mm.
The molded product of the rod-shaped modified polypropylene resin composition was chopped to a thickness of 3 mm to obtain pellets of the modified polypropylene resin composition.

The twin-screw extruder was of the same-direction twin-screw type, had a cylinder hole diameter of 32 mmφ, and had a maximum effective screw 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 the pellets of the modified polypropylene resin composition, a round rod-shaped foam was produced by the following method.

100 parts by weight of the pellets of the modified polypropylene resin composition, 0.05 parts by weight of the blended oil, and 0.1 parts by weight of talc as a foam nucleating agent were mixed for 15 minutes using a ribbon blender. This mixture is supplied to a tandem-type extruder (the first-stage extruder cylinder diameter is 40 mmφ, the second-stage extruder cylinder diameter is 50 mmφ), and is melted at 230 ° C. in the first-stage extruder. 8 parts by weight of butane gas (iso-rich butane gas; the mixture ratio of normal butane / isobutane is 15/85 by weight) is press-mixed with 100 parts by weight of the modified polypropylene resin composition and kneaded. In the machine, the temperature of the resin composition was cooled to 150 ° C, and the orifice was 6 mmφ.
It was extruded from a × 25 mm circular die to form a round rod-shaped foam.

The density, expansion ratio and closed cell rate of the obtained round rod-shaped foam were measured by the following methods, and the appearance and adhesion were evaluated according to the following evaluation criteria.

[0062] Density of foam: Calculated from weight and volume obtained by submersion method. Closed cell rate: Measured according to ASTM D-2856 using a multi bikinometer (product name, manufactured by Yuasa Ionics Co., Ltd.). Evaluation of appearance: The surface of the foam is visually observed. ：: No unfoamed portion, fluff and wrinkles were observed. ×: Unfoamed portions, fluff and wrinkles are seen. Evaluation of adhesiveness: A 1 cm square adhesive tape (Mending Tape manufactured by Sumitomo 3M Limited) was attached to the foam,
When the foam skin adheres to the tape-adhered surface when peeled off, it is evaluated as ○, and when it does not adhere, as ×.

As a result, the density was 37 kg / m ³ ,
The closed cell ratio was 76%, and the evaluation of the appearance and the adhesiveness was ○.

Example 2 The amounts of the styrene monomer, acrylic acid monomer and radical polymerization initiator in Example 1 were changed to 20 parts by weight, 3.0 parts by weight and 1.0 part by weight, respectively. A modified polypropylene resin composition was obtained in the same manner as in Example 1, and a round bar-shaped foam was obtained according to the same example.

Example 3 The same procedure as in Example 1 was repeated except that the polypropylene homopolymer was changed to an ethylene propylene random copolymer (melt flow index at 230 ° C., 0.5 g / 10 min). A resin composition was obtained, and a round bar-shaped foam was obtained according to the same example.

Example 4 3 parts by weight of zinc acetate dihydrate was blended with the modified polypropylene resin composition of Example 2 and a twin screw extruder (LABOTE) was used.
The modified polypropylene resin composition was obtained by melt-kneading using X), and a round rod-shaped foam was obtained according to Example 1.

Example 5 A modified polypropylene resin composition was obtained in the same manner as in Example 1 except that the styrene monomer was changed to the isoprene monomer in Example 1, and a round rod-shaped foam was obtained according to the same example.

Example 6 A modified polypropylene resin composition was obtained in the same manner as in Example 1 except that the styrene monomer was changed to 1,3-butadiene monomer in Example 1, and a round rod-shaped foam was produced according to the same example. I got it.

Comparative Example 1 Instead of using the pellets of the modified polypropylene resin composition, a propylene homopolymer (melt flow index at 230 ° C .: 0.4 / 10 minutes) was used, and the round rod-shaped foam of Example 1 was used. A round rod-shaped foam was obtained according to the method described in the above.

Comparative Example 2 A pellet of the modified polypropylene resin composition was obtained in the same manner as in Example 1 except that the acrylic acid monomer was not added, and a round rod-like foam was obtained according to the same example.

Comparative Example 3 Melting and kneading were performed in the same manner as in Example 1 except that the styrene monomer was not added.
Could not be a strand.

Table 1 shows the mixing ratio of each component in Examples 1 to 3, 5, and 6 and Comparative Examples 1 to 3.
Table 2 shows the results of density, closed cell ratio, appearance, and adhesiveness of the foams of Comparative Example 6 and Comparative Examples 1 to 3.

[0073]

[Table 1]

[0074]

[Table 2]

The foam produced by using the modified polypropylene resin composition in the examples has a low density, a high closed cell ratio, and excellent appearance and adhesiveness.
It can be seen that the unmodified polypropylene homopolymer foam shown in (1) has a high density and a low closed cell rate. Also,
It can be seen that when zinc acetate dihydrate is added to the modified polypropylene resin of Example 3 (Example 4), the closed cell ratio further increases.

A foam produced from a resin composition obtained by melt-kneading a raw polypropylene resin by adding only a styrene monomer and a radical polymerization initiator without adding acrylic acid has a foaming property (low density). The resin composition having a high closed cell rate and a good appearance is a resin composition having good foamability), but the effect is not sufficient, and the adhesiveness is poor. I understand. Also, a resin composition obtained by melt-kneading an acrylic acid monomer and a radical polymerization initiator in a raw material polypropylene resin,
It can be seen that the viscosity was reduced and pellets could not be formed.

[0077]

The polypropylene resin, at least one monomer selected from an aromatic vinyl monomer, an isoprene monomer and a 1,3-butadiene monomer, and an unsaturated carboxylic acid monomer By foaming a modified polypropylene resin composition obtained by melt-kneading a radical polymerization initiator and, if necessary, a metal compound, the closed cell rate is high, the density is low, the appearance is beautiful, and the adhesion is high. A foam having excellent paintability and paintability can be obtained.

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Claims (3)

[Claims] 1. A polypropylene resin, at least one monomer selected from an aromatic vinyl monomer, an isoprene monomer and a 1,3-butadiene monomer, and an unsaturated carboxylic acid monomer. And a foam comprising a modified polypropylene resin composition obtained by melt-kneading a radical polymerization initiator. 2. A foam comprising a modified polypropylene resin composition obtained by adding at least one metal compound selected from a metal salt and a metal oxide to the modified polypropylene resin composition according to claim 1. body. 3. The method for producing a foam according to claim 1, wherein the modified polypropylene resin composition and a foaming agent are melt-kneaded and then extruded to foam.