JPH10168214A - Preparation of modified polypropylene resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polypropylene resin foam having good properties and appearance by using a blowing agent less deleterious to the environment. SOLUTION: The preparation process comprises mixing a modified polypropylene resin obtained by reacting a mixture comprising a polypropylene resin, at least one monomer selected from the group consisting of aromatic vinyl monomers, isoprene monomers and 1,3butadiene monomers and a radical polymerization initiator with a blowing agent comprising 1,1,1,2-tetrafluoroethane and/or 1,1difluoroethane and a hydrocarbon and/or a chlorohydrocarbon each of which has a critical temperature of 130 deg.C or above in an extruder and discharging the mixture from the extruder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foam having good physical properties and appearance, comprising a modified polypropylene resin produced by using a foaming agent having little adverse effect on the environment.

[0002]

2. Description of the Related Art A foam made of a thermoplastic resin is lightweight and has good heat insulating properties and cushioning properties. Therefore, it is widely used in heat insulating materials, cushioning materials, core materials, food containers and the like. It's being used. Among them, a polypropylene (PP) -based resin foam has high chemical resistance, impact resistance, and heat resistance, and is particularly useful as a cushioning material.

[0003] There are various methods for producing a foam made of a PP-based resin. Among these methods, a PP-based resin is melted by an extruder, and then a low-boiling liquid or gas as a foaming agent is pressed into the foamed resin. The so-called extrusion foaming method, in which the material is cooled to a temperature suitable for foaming and then extruded into a low-pressure region and foamed, is an economically advantageous method.

[0004] However, since the PP resin has low viscosity and low tension when melted, it is generally difficult to produce a good foam by this method.

As a method for improving the foaming property of a PP resin, for example, a method of adding a crosslinking agent to a PP resin to crosslink PP resin molecules (for example, Japanese Patent Publication No. 45-4020)
And a method of foaming a blend of PP resin with polyethylene (for example, Japanese Patent Publication No. 44-25 / 1972)
No. 74), a method of foaming a blend of polystyrene and PP resin (for example, Japanese Patent Publication No. 43-1).
No. 3375).

[0006] However, even when these techniques are used, a foam having a high closed cell ratio and a low density is inferior.

As the low-boiling liquid or gas used as a foaming agent, chlorofluorocarbons (CFC 114, CFC 12, and CFC 142b) have been used because of their relatively good foamability.

However, in general, chlorofluorocarbons, especially saturated chlorohydrocarbons, are stable compounds. When released into the air, they are not decomposed in the troposphere surrounding the earth's surface and are directly converted into the stratosphere. And is said to destroy the ozone layer. It is said that when the ozone layer is destroyed, cosmic rays such as ultraviolet rays are no longer absorbed by the ozone layer and directly irradiate living organisms directly, thereby increasing, for example, the possibility of causing cancer or the like on the human body. Therefore, the use of chlorofluorocarbons must be avoided.

In order to solve such a problem of the prior art, for example, Japanese Patent Publication No. 3-29101 discloses a method of mixing a mixture of polyethylene and stearamide with 1,1-difluoroethane and an aliphatic or halogenated hydrocarbon. A method of foaming with a mixture is described in Japanese Patent Publication No. 6-49793.
In the publication, a method for producing a foam using a mixture of polyethylene and a fatty acid amide as a main blowing agent is disclosed, but neither discloses a PP resin at all.

Furthermore, Japanese Patent Publication No. 7-119314 discloses a method of foaming a thermoplastic resin with a foaming agent containing 1,1,1,2-tetrafluoroethane. Only, there is no evidence of the effect on the PP resin.

As described above, at present, no method has been found for producing a foam having a high closed cell ratio and a low apparent density by foaming a PP resin using an environmentally friendly foaming agent.

An object of the present invention is to provide a foam having a high closed cell ratio, a low apparent density and a beautiful appearance by using a modified PP resin composition having improved foamability and an environmentally friendly foaming agent. With the goal.

[0013]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, melt-kneaded a modified PP resin obtained by a specific method and a specific foaming agent in an extruder. After extruding, the present inventors have found that a foam having a high closed cell ratio, a low apparent density and a beautiful appearance can be produced at a low cost with little adverse effect on the environment, and the present invention has been completed.

That is, the present invention relates to a polypropylene resin (A) and at least one monomer selected from the group consisting of aromatic vinyl monomers, isoprene monomers and 1,3-butadiene monomers. A modified polypropylene-based resin (I) obtained by kneading or stirring a mixture of the polymer (B) and the radical polymerization initiator (C) at a temperature at which the polypropylene-based resin (A) melts and reacting the mixture.
And 1,1,1,2-tetrafluoroethane and / or 1,1-difluoroethane (II) as a foaming agent, and hydrocarbons and / or chlorohydrocarbons (III) having a critical temperature of 130 ° C. or higher. After mixing in an extruder, and then discharging the mixture to the outside of the extruder.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first, at least one selected from the group consisting of a PP resin (A) and an aromatic vinyl monomer, an isoprene monomer and a 1,3-butadiene monomer. A mixture comprising one kind of monomer (B) and a radical polymerization initiator (C) is kneaded or stirred at a temperature at which the PP-based resin (A) melts, and reacted to obtain a modified PP-based resin ( I) is manufactured.

Examples of the PP resin (A) include crystalline polymers such as a propylene homopolymer, a block copolymer of propylene and another monomer, or a random copolymer. When the PP resin (A) is a copolymer, PP
From the viewpoint of maintaining high rigidity and good chemical resistance, which are the characteristics of the base resin, the propylene component contained is
% (% By weight, hereinafter the same).
% Is more preferable.

Other monomers copolymerizable with propylene include ethylene; butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexane-1, 4-
Methylpentene-1,3,4-dimethyl-butene-1,
Α- having 4 to 12 carbon atoms such as octene-1 and decene-1
Olefins; cyclic olefins such as cyclopentene and norbornene; 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene,
Methyl-1,4-hexadiene, 7-methyl-1,6-
Diene monomers such as octadiene; vinyl monomers such as vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, and maleic anhydride And body. These may be used alone or in combination of two or more.
Among these monomers, ethylene, α-olefins having 4 to 12 carbon atoms, or diene monomers are preferable, and ethylene and butene-1 are more preferable in terms of low cost.

The melt index (MI) (molecular weight (weight average molecular weight)) at 230 ° C. of the PP resin (A) is preferably 0.01 to 100 g / 10 min from the viewpoint that it is easily available, and is inexpensive. From that point, 0.1-20 g
/ 10 minutes is more preferable.

If necessary, other resins or rubbers may be added to the PP resin (A) as long as the effects of the present invention are not impaired. Also, if necessary, stabilizers such as antioxidants, metal deactivators, phosphorus-based processing stabilizers, ultraviolet absorbers,
Even if additives such as a crosslinking agent, 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 are added as long as the effects of the present invention are not impaired. Good.

The above additive materials (other resins, rubbers, stabilizers,
When the (additive) is used, the additive material may be added to the PP resin (A) in advance, or may be added when the PP resin (A) is melted. After the modified PP resin (I) is produced, it may be added to the modified PP resin (I) by an appropriate method.

The PP-based resin (A) (which may contain various additive materials) may be in the form of granules or pellets, and its size and shape are not particularly limited.

At least one monomer (B) selected from the group consisting of the aromatic vinyl monomer, isoprene monomer and 1,3-butadiene monomer is a PP resin (A). It is a component used to modify the PP resin (A) by kneading or stirring at a temperature at which it melts and reacting. It should be noted that the components that can be used to modify the PP-based resin (A) are the above-mentioned components.
The PP resin (A) is modified by using it together with a radical polymerization initiator (Japanese Patent Application Nos. 7-189614 and 8-2).
599, Japanese Patent Application No. 8-2600, Japanese Patent Application No. 8-95329, and Japanese Patent Application No. 8-95330).

Examples of the aromatic vinyl monomer include styrene; methylstyrene such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene and p-methylstyrene; o-chlorostyrene; chlorostyrene such as m-chlorostyrene and p-chlorostyrene; bromostyrene such as o-bromostyrene, m-bromostyrene and p-bromostyrene; and fluoro such as o-fluorostyrene, m-fluorostyrene and p-fluorostyrene. Styrene; nitrostyrene such as o-nitrostyrene, m-nitrostyrene, p-nitrostyrene; hydroxystyrene such as o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene; o-divinylbenzene, m-divinylbenzene; p-divinylbenze And divinylbenzene. These may be used alone or in combination of two or more. Of these, styrene,
Methylstyrene and divinylbenzene are preferred because of their low cost.

When two or more of aromatic vinyl monomer, isoprene monomer and 1,3-butadiene monomer are used in combination, the ratio of use is arbitrary.

The amount of the monomer (B) used is 0.1 to 100 parts (parts by weight, hereinafter the same) of the PP resin (A).
The amount is preferably 1 to 50 parts, more preferably 1 to 30 parts, since the effect of improving the foamability of the obtained modified PP resin becomes remarkable.

The radical polymerization initiator (C) used in the present invention extracts hydrogen from the polymer molecules of the PP resin (A), reacts it with the monomer (B), and reacts with the monomer (B). Is a component for polymerizing

Examples of the radical polymerization initiator (C) include peroxides and azo compounds. Specific examples thereof include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides and peroxy peroxides. Organic peroxides such as oxydicarbonate and peroxyester are exemplified. Among them, those having particularly high hydrogen extraction ability, for example, 1,1
-Bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t
-Butylperoxy) valerate, 2,2-bis (t-
Peroxyketals such as butylperoxy) butane,
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-
Dialkyl peroxide such as butylperoxy) hexyne-3, diacyl peroxide such as benzoyl peroxide, t-butylperoxyoctate, t
-Butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,5,5-
Trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate,
Peroxyesters such as di-t-butylperoxyisophthalate are preferred. These may be used alone or in combination of two or more.

The amount of the radical polymerization initiator (C) used is based on 100 parts of the PP resin (A) from the viewpoint that the melt viscosity of the modified PP resin does not excessively decrease and is economical. It is preferably 0.01 to 5.0 parts, and 0.1 to 5.0 parts.
More preferably, it is 1.5 parts. When the amount of the radical polymerization initiator (C) is less than the above range, the modifying effect tends to be insufficient, while when the amount is more than the above range, a suitable shape and appearance are not obtained. There is a tendency that a foam having the same cannot be obtained.

There are no particular restrictions on the method of mixing the PP resin (A), the monomer (B), the radical polymerization initiator (C) and the components added as required, and the method of melting, kneading or stirring. For example, after mixing the PP resin (A), the monomer (B), the radical polymerization initiator (C) and the components added as required, the mixture may be melted and kneaded or stirred, or the PP resin After (A) is melted and kneaded or stirred, the monomer (B) or the radical polymerization initiator (C) and the components to be added as required are added simultaneously or separately, collectively or separately. May be mixed and melted, and kneaded or stirred.

The kneading or stirring is not particularly limited.
The melting temperature of the PP resin (A) is 130 to 4
The temperature of 00 ° C. means that the PP resin (A) is sufficiently melted,
Hardly thermally decomposes and has a radical polymerization initiator (C)
Is preferred because it is higher than the decomposition temperature of
50-250 ° C is preferred. Further, the time for melting and kneading or stirring is generally 1 to 60 minutes. Further, the kneading or stirring may be repeated plural times for uniform kneading or stirring.

As the apparatus used for melting and kneading or stirring, kneading machines such as rolls, co-kneaders, Banbury mixers, Brabenders, single-screw extruders, twin-screw extruders, twin-screw surface renewing machines, twin-screw Examples of such a device include a horizontal stirrer such as a multi-disc device, and a vertical stirrer such as a double helical ribbon stirrer, which can heat a polymer material to an appropriate temperature and knead while applying an appropriate shear stress. Among these, a single-screw or twin-screw extruder is particularly preferred in terms of productivity.

The modified PP resin (I) thus obtained has such a characteristic that when measured in a molten state, the elongational viscosity sharply increases as the amount of strain increases.

The modified PP resin (I) and 1,1,1,2-tetrafluoroethane and / or 1,1-difluoroethane (II) as a foaming agent (hereinafter also referred to as a foaming agent (II)) ) And a hydrocarbon having a critical temperature of 130 ° C. or higher and / or a chlorohydrocarbon (III) (hereinafter also referred to as a foaming agent (III)) are mixed in an extruder, and then discharged outside the extruder. By foaming, the modified PP resin (I) foam is produced.

The above-mentioned 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane are gases having no ability to destroy the ozone layer in the stratosphere. It was a gas that could not produce a suitable foam. Further, the hydrocarbons and chlorohydrocarbons having a critical temperature of 130 ° C. or more are intended to improve the drawback that a foaming agent (II) having preferable properties from the viewpoint of environment and safety cannot be used as a foaming agent alone. It is a gas used for 1,
1,1,2-tetrafluoroethane and / or
1,1-difluoroethane (II) and critical temperature 13
When hydrocarbons and / or chlorohydrocarbons (III) at 0 ° C. or higher are used as a foaming agent, the modified PP resin (I) can be foamed, which has not been known before. The effect is.

The hydrocarbons and / or
If the critical temperature of the chlorohydrocarbons is lower than 130 ° C., a stable extruded foam cannot be obtained.

Specific examples of the hydrocarbons include butane, pentane, hexane, heptane and the like, and specific examples of the chlorohydrocarbons include chloromethane, chloroethane, chloropropane and the like.

Further, a foaming agent (II) and a foaming agent (III)
As a usage ratio of the foaming agent (II) / the foaming agent (III), the weight ratio is 80/20 to 30/70, and more preferably 70/30
４０40/60, particularly preferably 65/35 to 45/55. When the ratio exceeds 80/20, a foaming agent (II)
The solubility and dispersibility of (1,1,1,2-tetrafluoroethane and / or 1,1-difluoroethane) are poor, and it is difficult to obtain a good foam. Shrinkage tends to increase.

A part of the foaming agent (I) used in the present invention comprising the foaming agent (II) and the foaming agent (III) is a small amount of other volatile foaming agent, gas-type foaming agent, decomposition-type foaming agent and the like. It may be replaced.

Examples of the other volatile blowing agents include aliphatic hydrocarbons such as propane; cyclobutane;
Alicyclic hydrocarbons such as cyclopentane and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichlorodifluoromethane, dichloromethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, Halogenated hydrocarbons such as tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, chloropentafluoroethane and perfluorocyclobutane; water and the like; Examples of the agent include, for example, inorganic gases such as carbon dioxide, nitrogen, and air. Examples of the decomposition-type blowing agent include nitroso-based blowing agents such as N, N'-dinitrosopentamethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide; azodicarbonamide And azo-based blowing agents such as barium azodicarboxylate; sulfohydrazide-based blowing agents such as p, p'-oxybisbenzenesulfonylhydrazide and p-toluenesulfonylsemicarbazide. These may be used alone or in combination of two or more.

The amount of the foaming agent (I) used (kneading amount) varies depending on the type of the foaming agent and the target expansion ratio, but is usually 0.5 to 40 parts with respect to 100 parts of the modified PP resin. Is preferable, and 5-35 parts is more preferable.

The modified PP resin (I) and the blowing agent (I)
Is mixed in an extruder, for example, a method in which a modified PP resin (I) is first melted in an extruder, a foaming agent (I) is press-fitted into the melt, and kneaded while maintaining the pressure at a high pressure. can give. Thereafter, the kneaded material is discharged from a die to obtain a foam.

In producing the above kneaded product, a foam nucleating agent (such as sodium bicarbonate-citric acid, talc) for controlling the cell diameter of the foam, if necessary, for preventing shrinkage of the foam. You may use together a shrinkage inhibitor (partial ester of fatty acid and polyol, fatty acid amide, etc.).
The amount of the foam nucleating agent used is usually 100
The amount is preferably 0.1 to 1.0 part per part, and the amount of the shrinkage inhibitor used is preferably 0.1 to 5 parts per 100 parts of the modified PP resin.

The temperature and time for kneading or stirring the modified PP resin (I) and the foaming agent (I) depend on the modified PP resin (I), the foaming agent (I) and the mixing conditions used. Since it is different, it may be appropriately selected, but the temperature is 130 to
Usually, the temperature is 400 ° C. and the time is 1 to 120 minutes.

The foam of the present invention thus produced has an apparent density of 10 to 500 kg / m ³ from the viewpoint that the foam is suitable for light weight, heat insulation, cushioning against external stress or compressive strength. And preferably 15 to 3
More preferably, it is 00 kg / m ³ . In addition, the closed cell rate is preferably 50% or more from the viewpoint that properties such as heat insulation, cushioning, and compressive strength are suitable.
More preferably, it is 0% or more.

The foam of the present invention may be in various shapes such as 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 column shape such as a column shape, an elliptic column shape, and a prism shape. Is raised.

[0046]

EXAMPLES Next, the present invention will be described based on examples.
The present invention is not limited to such an embodiment.

Examples 1-4 PP homopolymer (Noblen D, manufactured by Sumitomo Chemical Co., Ltd.)
501, MI 0.4 g / 10 min at 230 ° C) 100
Parts, styrene monomer 10 parts and α, α'-bis (di-t-butylperoxy-m-isopropyl) benzene (Nippon Oil & Fats Co., Ltd., Perbutyl P, 1 minute half-life temperature 175 ° C.) 1.0 part Was set to 200 ° C. (but 160 ° C. only below the mouth of the hopper) with a 32 mm twin-screw extruder (L / D
= 25.5) and the screw rotation speed is 100 rpm
To obtain a 4 mm rod-shaped modified PP resin. The obtained rod-shaped modified PP resin was cut into a length of 3 mm to obtain a modified PP resin pellet 1 (hereinafter, referred to as modified PP-1).

A mixture obtained by mixing 100 parts of the obtained modified PP-1 and 0.1 part of sodium bicarbonate-citric acid as a foaming nucleating agent using a ribbon blender was mixed with a tandem type extruder (a first-stage extruder cylinder). 40 mmφ, second-stage extruder cylinder 50 mmφ), press-fit the foaming agent shown in Table 1 into the mixture, cool in a second-stage extruder (50 mm) so that the resin temperature becomes 145 ° C., and use a circular die ( 6mmφ ×
25 mm) to obtain a round rod-shaped foam.

After a lapse of 24 hours from the extrusion foaming, the apparent density and the closed cell rate of the obtained round rod-shaped foam were measured by the following methods, and the appearance was evaluated by visual observation.
Table 1 shows the results.

The HFC134a shown in Table 1 is 1,
1,1,2-tetrafluoroethane, critical temperature 101
° C, HFC152a is 1,1-difluoroethane, critical temperature 113 ° C, isopentane critical temperature 188 ° C, ethyl chloride critical temperature 187 ° C, propane critical temperature 97 ° C.

(Apparent density) Calculated from the weight and the volume determined by the submerged method, and evaluated according to the following criteria. ：: Foam density is 40 kg / m ³ or less △: Foam density exceeds 40 kg / m ³ and 200 kg / m ³
m ³ or less ×: Foam density exceeds 200 kg / m ³

(Independent Bubble Ratio) ASTM D-285 using a multi-pycnometer (manufactured by Yuasa Ionics Co., Ltd.)
6 was measured. ：: The closed cell rate of the foam is 70% or more Δ: The closed cell rate of the foam is 50% or more and less than 70% ×: The closed cell rate of the foam is less than 50%

(Appearance) Visual observation was made and evaluated according to the following criteria. ：: No unfoamed part, lint, and wrinkles are observed. Δ: No unfoamed part is seen, but lint and wrinkles are seen. X: Unfoamed part, lint, and wrinkles are seen.

Comparative Examples 1 to 6 Using the modified PP-1 obtained in the same manner as in Example 1,
A round bar-shaped foam was obtained and evaluated in the same manner as in Example 1 except that the foaming agent was changed as shown in Table 1. Table 1 shows the results.

Examples 5 to 8 An ethylene-propylene random copolymer (ethylene unit content 3%, MI 0.5
g / 10 minutes), and a modified PP resin pellet-2 (hereinafter referred to as modified PP-2) was obtained in the same manner as in Example 1 except that the monomer was changed to isoprene.

A round rod-shaped foam was obtained in the same manner as in Example 1 except that the obtained modified PP-2 was used and the blowing agent was changed as shown in Table 1 (the resin temperature was set at 135 ° C.). ,evaluated. Table 1 shows the results.

Comparative Examples 7 to 12 Using the modified PP-2 obtained in the same manner as in Example 2,
A round rod-shaped foam was obtained and evaluated in the same manner as in Example 2 except that the foaming agent was changed as shown in Table 1. Table 1 shows the results.

Comparative Examples 13 to 16 Same as Example 1 except that the PP homopolymer used in Example 1 was used without modification by styrene melt grafting and the blowing agent was changed as shown in Table 1. Then, extrusion foaming was performed to obtain a round rod-shaped foam, which was evaluated. Table 1 shows the results.

Comparative Examples 17 to 20 Example 5 was repeated except that the ethylene-propylene random polymer used in Example 5 was used as it was without modification by isoprene melt grafting and the blowing agent was changed as shown in Table 1. Extrusion foaming was performed in the same manner as described above to obtain a round rod-shaped foam, which was evaluated. Table 1 shows the results.

[0060]

[Table 1]

From Table 1, it can be seen that the foam produced by using the foaming agent used in the present invention with the modified PP resin has a low apparent density, a high closed cell ratio, and excellent appearance.

On the other hand, Comparative Examples 1 to 6 and 7 to 12 using foaming agents other than the foaming agent used in the present invention, and Comparative Examples 13 to 16 using an unmodified PP resin and Comparative Examples 17 to 20 foams have apparent density, closed cell rate,
It can be seen that only a foam having an inferior appearance can be obtained.

[0063]

Industrial Applicability The PP resin (A) and at least one monomer (B) selected from the group consisting of aromatic vinyl monomers, isoprene monomers and 1,3-butadiene monomers
And a radical polymerization initiator (C) are melted, kneaded or stirred to obtain a modified PP resin, which is converted into 1,1,1,2-tetrafluoroethane and / or 1,1-difluoroethane (II) And hydrocarbons and / or chlorocarbons having a critical temperature of 130 ° C. or higher (II
By foaming using a foaming agent consisting of I),
A foam having a low apparent density, a high closed cell ratio and a beautiful appearance can be produced by a method which has little adverse effect on the environment.

Claims (1)

[Claims] 1. A polypropylene resin (A) and at least one monomer (B) selected from the group consisting of an aromatic vinyl monomer, an isoprene monomer and a 1,3-butadiene monomer. And a radical polymerization initiator (C) are kneaded or stirred at a temperature at which the polypropylene-based resin (A) melts, and the resulting mixture is reacted with a modified polypropylene-based resin (I). 1,1,
1,2-tetrafluoroethane and / or 1,1
A modified polypropylene, characterized in that difluoroethane (II) and hydrocarbons having a critical temperature of 130 ° C. or higher and / or chlorohydrocarbons (III) are mixed in an extruder and then discharged out of the extruder. Manufacturing method of resin foam.