JPH10298333A - Modified polypropylene-based resin foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin foam having a beautiful appearance, high closed cell fraction, low density, high cross section magnification rate, and esp. excellent dimensional stability with low shrinkage just after expanded, and to provide a method for producing the foam by extrusion expansion. SOLUTION: This modified resin foam is obtained by extrusion expansion of a mixture of (D) a higher fatty acid ester of polyhydric alcohol with a modified polypropylene-based resin composition which is produced by kneading (A) a polypropylene-based resin, (B) at least one kind of polymerizable monomer selected from aromatic vinyl monomers, isoprene and 1,3-butadiene and (C) a radical polymerization initiator under molten state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a modified polypropylene resin foam and a method for producing the same. More specifically, the present invention relates to a modified polypropylene-based resin foam which can be suitably used as a structural material such as a wall of a building or a partition, a cushioning material such as a packaging material of a high-load precision instrument, and a method for producing the same.

[0002]

2. Description of the Related Art In general, a foam made of a thermoplastic resin is lightweight, has good heat insulating properties and good buffering properties against external stress, and is therefore widely used as a heat insulating material, a cushioning material, a core material, a food container and the like. It's being used. Above all, foams made of polypropylene resin are inexpensive and have good chemical resistance, impact resistance and heat resistance, so they are widely used in various fields, and in particular, are suitably used as cushioning materials. ing.

[0003] However, polypropylene resins are
Since it is a crystalline resin, the melt viscosity and tensile strength are sharply reduced during melting, and when the polypropylene resin is foamed, the strength of the cell wall is not sufficiently maintained during foaming.
Further, since the polypropylene-based resin has a low gas barrier property, the gas generated from the foaming agent is more easily scattered to the outside than the bubbles when foaming the resin.

[0004] As described above, by foaming a polypropylene resin, a foam having a beautiful appearance, a high closed cell ratio, a low density, and a small dimensional stability with little shrinkage immediately after foaming can be obtained. It was difficult.

[0005] Therefore, as a method of improving the foaming property of the polypropylene resin, for example, a method of adding a crosslinking aid to the polypropylene resin to crosslink its molecules (Japanese Patent Publication No. 45-4020), a method of improving the polyolefin resin, and the like. A method using a partial ester of a fatty acid and a polyol having 3 to 6 hydroxyl groups (Japanese Patent Publication No. 46-43997) can be used as a foam control agent. Cannot be said to be sufficiently improved.

As described above, a foam having improved foamability of a polypropylene-based resin, a beautiful appearance, a high closed cell ratio, a low density, and a small dimensional stability with little shrinkage immediately after foaming is produced. At present, no method has been found yet.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and is made of a modified polypropylene resin having improved foaming properties, has a beautiful appearance, has a high closed cell ratio, and has a low It is an object of the present invention to provide a foam having a high density, a large cross-sectional enlargement ratio, and a small dimensional stability in which shrinkage immediately after foaming is small, and a method for producing the same.

[0008]

The present invention provides a polypropylene resin (A), an aromatic vinyl monomer,
A modified polypropylene resin composition obtained by melt-kneading at least one polymerizable monomer (B) selected from isoprene and 1,3-butadiene and a radical polymerization initiator (C); A modified polypropylene resin foam obtained by extrusion-foaming a mixture with a higher fatty acid ester (D); a polypropylene resin (A); an aromatic vinyl monomer;
A modified polypropylene resin composition obtained by melt-kneading at least one polymerizable monomer (B) selected from isoprene and 1,3-butadiene and a radical polymerization initiator (C); The present invention relates to a method for producing a modified polypropylene resin foam, characterized in that a foaming agent-impregnated resin composition obtained by impregnating a mixture with a higher fatty acid ester (D) with a foaming agent is extruded and foamed in a low pressure region in a molten state.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the modified polypropylene resin foam of the present invention comprises a polypropylene resin (A), an aromatic vinyl monomer, isoprene and 1,3
A temperature at which at least one polymerizable monomer (B) selected from butadiene and a radical polymerization initiator (C) are melted, for example, with a polypropylene resin (A);
A mixture of the modified polypropylene resin composition obtained by melt-kneading at a temperature at which the radical polymerization initiator (C) can be decomposed and a higher fatty acid ester of a polyhydric alcohol (D) is extruded in a molten state into a low pressure region. It is obtained by foaming, and since the foamability in the cross-sectional direction perpendicular to the extrusion direction has been significantly improved, the closed cell rate is high, the density is low, the cross-sectional expansion rate is large, especially immediately after foaming It is a foam having excellent dimensional stability with small shrinkage.

The polypropylene resin (A) may be any of a propylene homopolymer, a block copolymer and a random copolymer. Of these, propylene copolymers and propylene homopolymers containing 85% by weight or more of propylene are particularly preferred.

The monomers copolymerizable with propylene in the propylene-based copolymer include, in addition to ethylene, for example, butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexene-1,3-hexene. Methyl-pentene-1,4-methyl-pentene-1,3,4-dimethyl-
Butene-1, heptene-1,3-methyl-hexene-
1, octene-1, decene-1, etc., having 4 to 12 carbon atoms
Α-olefins; cyclic olefins such as cyclopentene and norbornene.

Melt flow index (MI) of the polypropylene resin (A) (measured at 230 ° C. under a load of 2.16 kg according to the method described in JIS K 7210)
Is preferably 0.2 g / 10 min or more, more preferably 0.3 g / 10 min or more, from the viewpoint of processability, and the viscosity of the modified polypropylene resin composition is adjusted to a level suitable for foaming during melting. From the viewpoint of maintenance, it is preferably 20 g / 10 minutes or less, especially preferably 10 g / 10 minutes or less.

In the present invention, a part of the polypropylene resin (A) may be replaced with another resin or rubber, if necessary, as long as the effects of the present invention are not impaired.

The other resins and rubbers include, for example, polyethylene; polyα such as polybutene-1, polyisobutene, polypentene-1 and polymethylpentene-1.
-Olefin; ethylene or α such as ethylene / propylene copolymer, ethylene / butene-1 copolymer having a propylene content of less than 85% by weight, and propylene / butene-1 copolymer having a propylene content of less than 85% by weight. Ethylene or α, such as ethylene / propylene / 5-ethylidene-2-norbornene copolymer having a propylene content of less than 85% by weight;
-Olefin / α-olefin / diene monomer copolymer.

The amount of the other resin or rubber relative to the polypropylene resin (A) varies depending on the type of the other resin or rubber, and may be within a range that does not impair the effects of the present invention as described above. % Is preferable.

The other resin or rubber may be blended together with the polypropylene resin (A), or may be blended in the resulting modified polypropylene resin composition.

The polymerizable monomer (B) exhibits a modifying effect by inhibiting the main chain of the polypropylene resin (A) from being cut by the radical polymerization initiator (C). Or at least one selected from isoprene and 1,3-butadiene.

Examples of the aromatic vinyl monomer include styrene; methyl styrene such as o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, β-methyl styrene, dimethyl styrene, trimethyl styrene, etc. One or more kinds of divinylbenzene such as o-divinylbenzene, m-divinylbenzene, p-divinylbenzene and the like;

The aromatic vinyl monomer, isoprene and 1,3-butadiene may be used alone or in combination of two or more. There is no particular limitation.

The amount of the polymerizable monomer (B) sufficiently exerts an effect of suppressing cleavage of the main chain of the polypropylene resin (A) by using the polymerizable monomer (B). For the above, the polypropylene resin (A)
0.1 parts or more for 100 parts (parts by weight, the same applies hereinafter),
In particular, it is preferably at least 1 part, and in order not to impair the inherent heat resistance and impact resistance of the polypropylene resin (A), it is preferably at most 50 parts, especially at most 30 parts. preferable. In particular, considering the compatibility of the resins, the polymerizable monomer (B)
Is preferably 0.1 to 30 parts with respect to 100 parts of the polypropylene resin (A).

The radical polymerization initiator (C) is a radical polymerization initiator having a hydrogen abstracting ability with respect to the polymer molecules of the polypropylene resin (A).

Examples of the radical polymerization initiator (C) include peroxides and azo compounds. Specific examples thereof include ketone peroxides such as methyl ethyl ketone peroxide and methyl acetoacetate peroxide; Bis (t-butylperoxy)-
3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate,
Peroxy ketals such as 2,2-bis (t-butylperoxy) butane; permethane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide Hydrocumoxides such as dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, dialkyl peroxides such as t-butylcumyl peroxide, di-t-butyl peroxide and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; diacyl peroxides such as benzoyl peroxide Di (3-methyl-
3-methoxybutyl) peroxydicarbonate, di-
Peroxydicarbonates such as 2-methoxybutylperoxydicarbonate; t-butylperoxyoctate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,
5,5-trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-
One kind of organic peroxides such as peroxyesters such as 2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate and di-t-butylperoxyisophthalate Alternatively, two or more kinds can be used.

Among these, those having a particularly high hydrogen abstracting ability are preferable. As such a radical polymerization initiator, 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-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3
Diacyl peroxides such as benzoyl peroxide; t-butyl peroxy octate, t-butyl peroxyisobutyrate, t-butyl peroxy laurate, t-butyl peroxy-3,3. 5-trimethylhexanoate, t-
Butyl peroxyisopropyl carbonate, 2,5-
One or two of peroxyesters such as dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate;
More than seeds.

The amount of the radical polymerization initiator (C) is preferably 0 to 100 parts of the polypropylene resin (A) in order to sufficiently optimize the melt viscosity of the obtained modified polypropylene resin composition. It is preferably at least 0.05 part, more preferably at least 0.1 part, and in consideration of economy, it is preferably at most 10 parts, especially at most 5 parts.

Further, the modified polypropylene resin composition used in the present invention may optionally contain, for example, a cell nucleating agent (nucleating agent), an antioxidant, a metal deactivator, and a phosphorus-based processing stabilizer. , UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, antacid adsorbents, crosslinkers, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, flame retardants, antistatic agents An additive such as an anti-shrinkage agent may be added as long as the effects of the present invention are not impaired.

For example, the cell nucleating agent may be any one which is commonly used, and specific examples thereof include inorganic powders such as talc and silica; zinc stearate;
Organic fine powders such as calcium stearate; and fine powders that generate gas by heating a mixture of citric acid and sodium bicarbonate.

When the above-mentioned additive is used, the additive may be added to the polypropylene resin (A) in advance, or may be added when the polypropylene resin (A) is melt-kneaded. . After the modified polypropylene resin composition is manufactured, it may be added to the modified polypropylene resin composition by an appropriate method.

The modified polypropylene resin composition used in the present invention comprises a polypropylene resin (A), a polymerizable monomer (B) and a radical polymerization initiator (C), and optionally other resins and rubbers. And additives are melt-kneaded.

The mixing method and the melt kneading method of the polypropylene resin (A), the polymerizable monomer (B) and the radical polymerization initiator (C), and if necessary, other resins, rubbers and additives. There is no particular limitation. For example, after mixing a polypropylene resin (A), a polymerizable monomer (B), a radical polymerization initiator (C), and other resins and rubbers and additives which are added as required, melt kneading is performed. Alternatively, after the polypropylene resin (A) is melt-kneaded, a polymerizable monomer (B), a radical polymerization initiator (C), and other resins and rubbers added as necessary, The agents may be mixed simultaneously or separately, collectively or separately and melt-kneaded.

The apparatus used for the melt-kneading includes:
For example, kneaders such as rolls, co-kneaders, Banbury mixers, Brabenders, single-screw extruders, twin-screw extruders, twin-screw surface renewers, horizontal-screw stirrers such as twin-screw multi-disc devices, or double-helical ribbon stirrers Such as a vertical stirrer,
There is an apparatus capable of heating a polymer material to an appropriate temperature and kneading while appropriately applying a shearing stress. Among these, a single-screw or twin-screw extruder is particularly preferred in terms of productivity. Further, in order to mix each material sufficiently uniformly, the above-mentioned melt-kneading may be repeated a plurality of times.

The temperature of the melt-kneading is, for example, 2
Any temperature may be used as long as it is a temperature at which the polypropylene-based resin (A) melts, such as about 00 to 300 ° C., and the radical polymerization initiator (C) can be decomposed.

Next, the modified polypropylene resin composition thus obtained is mixed with a higher fatty acid ester (D) of a polyhydric alcohol (hereinafter, also referred to as an ester (D)) to prepare a mixture.

The ester (D) is a component that suppresses shrinkage of the foam immediately after foaming and improves dimensional stability.

Examples of the polyhydric alcohol constituting the ester (D) include glycerin, pentaerythritol,
Sorbit, Sorbitan, Mannit, Mannitan, Diglycerin, Dipentaerythritol and the like.

The higher fatty acids constituting the ester (D) include, for example, those having 10 to 30 carbon atoms such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, palmitoleic acid, oleic acid and linoleic acid. Examples thereof include monovalent or unsaturated higher fatty acids, bovine fatty acids and coconut oil fatty acids in which these higher fatty acids are mixed.

For example, typical examples of the ester (D) comprising the above-mentioned polyhydric alcohol and higher fatty acid include, for example, lauric acid monoglyceride, palmitic acid monoglyceride, stearic acid monoglyceride, pentaerythritol monocaprate, pentaerythritol monooleate, and pentarhate One or two of erythrit monolaurate, dipentaerythrit distearate, sorbitan monolaurate, sorbitan monostearate, mannitan monooleate, mannitan monolaurate, etc.
More than seeds.

In order to sufficiently improve the dimensional stability of the obtained foam, the amount of the ester (D) to be added is preferably 0.05 to 100 parts of the modified polypropylene resin composition.
And more preferably 0.1 part or more, and in order to sufficiently maintain the stability of the blowing agent-impregnated resin composition during extrusion foaming, 10 parts or less and preferably 5 parts or less.
Parts or less.

The method for obtaining the mixture is not particularly limited. For example, a polypropylene resin (A), a polymerizable monomer (B), and a radical polymerization initiator (C) constituting the modified polypropylene resin composition May be mixed with the ester (D) and melt-kneaded, or the polypropylene-based resin (A) may be melt-kneaded and then mixed with the polymerizable monomer (B) and the radical polymerization initiator (C). The esters (D) may be mixed simultaneously or separately, collectively or separately, and then melt-kneaded.

By extruding and foaming the mixture thus obtained, the foam of the present invention can be produced.

In the present invention, as the blowing agent impregnated in the mixture, for example, aliphatic hydrocarbons such as propane, butane, pentane, 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, dichlorotetrafluoroethane, trichlorotrifluoroethane Tetrachloro-difluoroethane, chloropentafluoroethane, halogenated hydrocarbons such as perfluorocyclobutane; carbon dioxide, nitrogen, inorganic gases such as air; one, such as water or two or more thereof.

The amount of the foaming agent to be added is not particularly limited, and varies depending on the type of the foaming agent and the target expansion ratio of the foam, but is in the range of about 5 to 50 parts per 100 parts of the modified polypropylene resin composition. Is preferably within the range.

In order to impregnate the mixture with a foaming agent and extrude and foam the obtained foaming agent-impregnated resin composition in a molten state in a low-pressure region, for example, a modified polypropylene resin composition is melt-kneaded using an apparatus used for the melt-kneading. After melt-kneading a mixture of the resin and the ester (D), the blowing agent-impregnated resin composition obtained by impregnating the mixture with a blowing agent may be discharged out of the apparatus and foamed, or the molten state may be modified. The mixture of the porous polypropylene resin composition and the ester (D) may be impregnated with a foaming agent in a device such as a tandem-type extruder and discharged outside the device to cause foaming.

When the foaming agent-impregnated resin composition is extruded and foamed in a low pressure region in a molten state, it is preferable to adjust the temperature to a temperature suitable for foaming. The temperature suitable for such foaming is determined by modifying the modified polypropylene resin composition with the ester (D).
May be appropriately adjusted depending on the composition of the mixture with, for example, about 120 to 200 ° C., particularly 130 to 160 ° C.
It is preferred that it is about.

The low-pressure region is usually under atmospheric pressure, but may be in a reduced-pressure atmosphere lower than atmospheric pressure if necessary.

The modified polypropylene resin foam of the present invention is a foam which is lightweight, has a beautiful appearance, has a high closed cell ratio and a low density, and has excellent dimensional stability. It is very useful in thermal insulation and other applications.

[0046]

Next, the modified polypropylene resin foam of the present invention and the method for producing the same will be described in more detail with reference to Examples. However, the present invention is not limited to only these Examples.

Example 1 Ethylene random polypropylene (Hypol B230 manufactured by Grand Polymer Co., Ltd., polypropylene content =
97% by weight, MI = 0.5 g / 10 min), 100 parts,
α, α'-bis (t-butylperoxy-m-isopropyl) benzene (Perbutyl P, 1 manufactured by NOF CORPORATION)
0.5 part per minute (half-life temperature = 175 ° C.), 0.2 part of stabilizer (Irganox B225 manufactured by Ciba-Geigy) and blend oil (SuperEase manufactured by Koshigaya Chemical Co., Ltd.)
The mixture consisting of 0.05 parts was stirred and mixed with a super floater. The mixture is reduced to 30 k using a quantitative feeder.
g / hr twin screw extruder (L
/ D = 38), and 3 kg of styrene
/ Hr (diaphragm manufactured by Nikkiso Co., Ltd., model C22X-08F-14D1D,
Using a discharge pressure of 50 kgf / cm ² ), 10 parts of styrene was injected from the middle of the extruder cylinder. The temperature before the injection of styrene was set at 180 ° C., the temperature after the injection was set at 200 ° C., and the melt-kneaded product was extruded at a rotation speed of 100 rpm to produce pellets of the modified polypropylene resin composition.

Next, with respect to 100 parts of the modified polypropylene resin composition, 0.05 part of blend oil and 0.1 parts of sodium hydrogencarbonate-citric acid as a cell nucleating agent.
And 1 part of stearic acid monoglyceride (Exel T-95 manufactured by Kao Corporation) were added and mixed with a super floater. Then, this was supplied to a 40 mmφ-50 mmφ tandem type extruder and melted at 200 ° C. in a first stage extruder (40 mmφ), and then isorich butane (n-butane / i-butane (weight) was used as a foaming agent. Ratio) = 15 /
85), and press-fit and mix 10 parts with respect to 100 parts of the modified polypropylene-based resin composition to obtain a second-stage extruder (50 mmφ).
Cool to resin temperature 150 ° C with cylindrical die (6mmφ ×
From 25 mm) under atmospheric pressure to obtain a round rod-shaped foam.

The physical properties of the obtained foam include (a) closed cell ratio, (b) foam density, (c) cross-sectional enlargement ratio, and (d)
The cross-sectional shrinkage and (e) appearance were examined according to the following methods. Table 2 shows the results.

(A) Closed cell rate According to the method described in ASTM D-2856, the closed cell rate (%) was measured by an air pycnometer (MODEL 930 manufactured by Beckman).

(B) Foam density The foam density (kg / m ³ ) was measured according to the method described in JIS-K6767.

(C) Cross-sectional enlargement ratio The cross-sectional areas of the foam immediately after foaming and the foam cured at room temperature for 24 hours after foaming were measured, and the following formula was obtained from these and the cross-sectional area of the foamed extrusion die. , The cross-sectional magnification (times) of each foam was calculated.

Cross sectional magnification (times) = (cross sectional area of foam) /
(D) Cross-sectional area of extrusion die (d) Cross-sectional shrinkage The diameter of the foam after 5 minutes from the foaming and the diameter of the foam after 24 hours from the foaming were measured, and the diameter of the foam and the foam immediately after the foaming were measured. The sectional shrinkage rate (%) of each foam was calculated based on the following formula.

Cross-sectional shrinkage (%) = {1− (diameter of foam after elapse of a certain time after foaming) / (diameter of foam immediately after foaming)} × 100 (e) Appearance The appearance of the foam is visually observed. And evaluated based on the following evaluation criteria.

A: Shrinkage and swelling of the foam surface are less than 7% of the whole. ：: Shrinkage and swelling of the foam surface are 7% or more and less than 12% with respect to the whole. Δ: Shrinkage and swelling of the foam surface are 12% or more and less than 20% with respect to the whole. ×: Shrinkage and swelling of the foam surface are 20% or more of the whole.

Examples 2 to 4 and Comparative Examples 1 to 3 Modified polypropylene was obtained in the same manner as in Example 1 except that the composition of the modified polypropylene resin composition was changed as shown in Table 1. A pellet of the resin composition was prepared, and a round bar-shaped foam was obtained from the pellet. The physical properties of the obtained foam were examined in the same manner as in Example 1. Table 2 shows the results.

The abbreviations in Table 1 are as shown below.

PP: ethylene random polypropylene (Hypol B230 manufactured by Grand Polymer Co., Ltd.) EPR: ethylene propylene rubber (Mitsui Petrochemical Industries, Ltd.)
Stuff: Styrene IP: Isoprene BD: 1,3-Butadiene BPO: α, α'-bis (t-butylperoxy-m-)
Isopropyl) benzene SG: Monoglyceride stearate (Exel T-95 manufactured by Kao Corporation) The physical properties in Table 2 are as shown below.

Cross-sectional enlargement ratio (1): Cross-sectional enlargement ratio of foam immediately after foaming Cross-sectional enlargement ratio (2): Cross-sectional enlargement ratio of foam cured at room temperature for 24 hours after foaming Cross-sectional shrinkage ratio (1): After foaming Cross-sectional shrinkage of foam after 5 minutes Cross-sectional shrinkage (2): Cross-sectional shrinkage of foam after 24 hours after foaming

[0060]

[Table 1]

[0061]

[Table 2]

From the results shown in Table 2, the foams of the present invention obtained in Examples 1 to 4 are all excellent in appearance, have a high closed cell ratio and a low density, and are in a state immediately after foaming. Even after curing for 24 hours, the cross-sectional expansion rate is large, and even after 5 minutes of foaming or after 24 hours, the cross-sectional shrinkage is small and the dimensional stability is excellent. You can see that there is.

On the other hand, the foams of Comparative Examples 1 and 2 in which the ester (D) was not used had a small cross-sectional enlargement rate, were inferior in appearance, had a large cross-sectional shrinkage rate, and had poor dimensional stability. The foam of Comparative Example 3, which is inferior and does not use the polymerizable monomer (B) and the radical polymerization initiator (C), has a closed cell ratio, a density, a cross-sectional expansion ratio, a cross-sectional shrinkage ratio, and an appearance. It can be seen that these are inferior to any of the physical properties.

[0064]

The modified polypropylene resin foam of the present invention has a beautiful appearance, a high closed cell ratio and a low density,
Moreover, the cross-sectional enlargement ratio is large, and the shrinkage immediately after foaming is small, and the dimensional stability is excellent.

Therefore, the modified polypropylene-based resin foam of the present invention has a high cushioning property that cannot be achieved by conventional foams, and exhibits excellent performance as a packaging material, a cushioning material, a heat insulating material, and the like. There is expected.

Claims (2)

[Claims] 1. A polymerizable monomer (B) selected from a polypropylene resin (A), an aromatic vinyl monomer, isoprene and 1,3-butadiene, and a radical polymerization initiator (C). A modified polypropylene resin foam obtained by extrusion-foaming a mixture of a modified polypropylene resin composition obtained by melt-kneading and a higher fatty acid ester (D) of a polyhydric alcohol. 2. A polymerizable monomer (B) selected from a polypropylene resin (A), an aromatic vinyl monomer, isoprene and 1,3-butadiene, and a radical polymerization initiator (C). A foaming agent impregnated resin composition obtained by impregnating a foaming agent with a mixture of a modified polypropylene resin composition obtained by melt-kneading and a higher fatty acid ester of a polyhydric alcohol (D) is extruded in a molten state into a low pressure region. A method for producing a modified polypropylene resin foam, characterized by foaming.