JPH09111034A - Preliminarily foamed polypropylene resin granule, polypropylene resin foamed and molded product and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the foamed and molded product good in secondary foamability without imparting a pressure and without compression-charging a foaming agent, etc., by using a foaming agent little in environmental disruptions such as ozonsphere disruption. SOLUTION: The granules of a substrate resin comprising a polypropylene resin is impregnated with a foaming agent consisting mainly of a 2-6C hydrocarbon substituted with at least two fluorine atoms and subsequently preliminarily foamed to produce the objective preliminarily foamed polypropylene resin granules having a bulk density of 0.15-0.03g/cm<3> . The preliminarily foamed granules are foamed into the sizes of 1.8-3.0 times as such in a desired mold.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to polypropylene-based pre-expanded resin particles, polypropylene-based resin foam-molded articles, and methods for producing them. More specifically, the present invention uses a specific foaming agent with less environmental damage such as ozone layer destruction, and the like, polypropylene-based pre-expanded resin particles capable of providing an excellent foamed molded product without applying internal pressure and compression filling. The present invention relates to a polypropylene resin foam molded article obtained from them and a method for producing the same.

The polypropylene resin foam molded article of the present invention is particularly preferably used as a form of a cushioning packaging material for various OA equipments, audio equipments, home electric appliances and the like.

[0003]

2. Description of the Related Art Generally, polypropylene resin foam moldings are known to have excellent impact resistance. Various methods have been reported as a method for producing the polypropylene resin foam-molded article, and one of them has been an in-mold foam-molding method. According to the in-mold foam molding method, the expandable polypropylene-based resin particles containing a foaming agent are heated to form pre-expanded resin particles, which are put in a molding die and heated again so that the foamed resin particles melt each other. It is possible to obtain a polypropylene-based resin foam-molded article that is attached.

Conventionally, as a foaming agent for producing a polypropylene resin foam molded article, hydrocarbons such as butane and pentane, 1,1-dichloro-1-fluoroethane (F-14) have been used.
1b), 1-chloro-1,1-difluoroethane (F-
142b) and other chlorinated fluorohydrocarbons (see, for example, JP-B-6-62800).

However, in the case of producing a polypropylene-based resin foamed molded article, these foaming agents have a drawback in that although the amount of impregnation in the polypropylene-based resin is relatively large, the rate of dissipation is high. Therefore, even with the expandable polypropylene-based resin particles produced under the same production conditions, the properties of the pre-expanded resin particles to be obtained differ depending on the time after impregnation, in order to obtain a product having a certain property. It was necessary to adjust the foaming conditions according to the passage of time.

On the other hand, in the case of producing a polypropylene-based resin foamed molded article, since the speed at which the foaming agent dissipates is high,
When the foam molding was performed in the mold as it was, the foaming was not performed only by filling the gaps between the pre-foamed resin particles, and the resulting polypropylene resin foam molding had defects such as dents and cracks. Therefore, in a state where the pre-expanded resin particles are compressed in the mold, the pre-expanded resin particles are filled in a mold that can be closed but not closed and then foam-molded as it is (compression filling foaming method), or the blowing agent in the pre-expanded resin particles is carbonated. Apply internal pressure with gas, nitrogen, air, etc.,
In addition, it was necessary to quickly perform molding (internal pressure imparting foaming method) before the internal pressure was reduced. For such molding, special auxiliary equipment for producing a polypropylene resin foam molded article was required. As the internal pressure imparting foaming method, the method described in Japanese Patent Publication No. 6-45721 is known.

Further, chlorinated fluorinated hydrocarbons are excellent in that the impregnated amount is larger than that of hydrocarbons, but if the chlorofluorocarbon is released into the atmosphere as it is, the environment is destroyed due to the destruction of the ozone layer and the like. There was a drawback that In view of the above problems, the inventors of the present invention have earnestly studied and, as a result, found that if a specific foaming agent is used, an excellent foamed molded product can be obtained without being foamed by applying internal pressure and compression filling. Came to.

[0008]

Thus, according to the present invention, the base resin particles are polypropylene resin and the foaming agent has 2 to more carbon atoms substituted with at least two fluorine atoms.
6 hydrocarbons, the pre-expanded resin particles after pre-expansion are 0.
Provided is a polypropylene-based pre-expanded resin particle having a bulk density of 15 to 0.03 g / cm ³ .

Further, according to the present invention, the base resin particle is a polypropylene resin, and the foaming agent is a hydrocarbon having 2 to 6 carbon atoms substituted with at least two fluorine atoms.
Provided is a polypropylene-based resin foam molded article obtained by expanding pre-expanded resin particles having a bulk density of 15 to 0.03 g / cm ³ 1.8 to 3.0 times. Further, according to the present invention, base resin particles made of polypropylene resin are impregnated with a foaming agent containing a hydrocarbon having 2 to 6 carbon atoms substituted with at least two fluorine atoms as a main component, 0.15 to 0.03 g by pre-foaming
After obtaining pre-expanded resin particles having a bulk density of / cm ³ ,
Next, there is provided a method for producing a polypropylene-based resin foam-molded article, which comprises subjecting the pre-foamed resin particles as they are to foam-molding 1.8 to 3.0 times in a desired molding die.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Base resin particles made of polypropylene resin are used in the present invention. Here, as the polypropylene resin, propylene homopolymer, ethylene-propylene random copolymer (ethylene components 1 to 20
% By weight), ethylene-propylene block copolymer, 1
Examples of the resin include a butene-propylene copolymer and a propylene-ethylene-butene terpolymer. These resins may be used alone or as a mixture of two or more kinds. In addition, a branched structure or a crosslinked structure may be used using the above polypropylene resin.

The shape of the base resin particles is not particularly limited, and examples thereof include spherical, cylindrical and pellet shapes. Here, the base resin particles have a volume of 1 to 10 mm ^3.
It is preferred to use a degree of particles. Further, the base resin particles used in the present invention, various additives, if necessary,
For example, fillers (eg silica, alumina, titanium oxide, talc, clay, calcium carbonate, etc.), antioxidants, lubricants (eg liquid paraffin, fatty acid esters, metal soaps, etc.), flame retardants, flame retardant aids, antistatic Agents and the like can be added.

One of the features of the present invention is to use a foaming agent composed of a hydrocarbon having 2 to 6 carbon atoms (hereinafter referred to as fluorohydrocarbon) substituted with at least two fluorine atoms. Examples of the above-mentioned fluorohydrocarbon include difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, and hexfluoroethane, in which the hydrogen atom of ethane is replaced by 2 to 6 with a fluorine atom; difluoropropane, trifluoropropane ,
Compounds of tetrafluoropropane, pentafluoropropane, hexfluoropropane, heptafluoropropane, octafluoropropane in which the hydrogen atoms of propane are substituted by 2 to 8 with fluorine atoms; difluorobutane, trifluorobutane, tetrafluorobutane, pentafluoro A compound in which the hydrogen atom of butane is replaced by 2 to 10 with a fluorine atom consisting of butane, hexfluorobutane, heptafluorobutane, octafluorobutane, nonafluorobutane, and decafluorobutane; difluoropentane, trifluoropentane, tetrafluoropentane, Pentafluoropentane, Hexfluoropentane, Heptafluoropentane, Octafluoropentane, Nonafluoropentane, Decafluoropentane, Dodecafluoropentane, Undecaf A compound in which hydrogen atoms of pentane are substituted with 2 to 12 by a fluorine atom consisting of oropentane; difluorohexane, trifluorohexane, tetrafluorohexane, pentafluorohexane, hexfluorohexane, heptafluorohexane, octafluorohexane, nonafluorohexane, Decafluorohexane,
Dodecafluorohexane, undecafluorohexane,
Fluorine atoms consisting of tridecafluorohexane and tetradecafluorohexane, with hydrogen atoms of hexane ranging from 2 to 14
Included are substituted compounds.

Of the above fluorocarbons, 1,1-difluoroethane (F-152a), 1,1,1-trifluoroethane (F-143a), 1,1,1,2-tetrafluoroethane (F -134a), 1,1,1,2,2-
Pentafluoroethane (F-125), 1,2-difluorobutane (F-245fa), 1,1-difluorobutane (F-245eb), 1,1,2-trifluorobutane (F-236ea), 1, 1,2,2,3-pentafluorobutane (F-245ca), 1,1,1,3
3-pentafluoropentane (F-338mcf),
1,1,2,2,3,3,4,4-octafluoropentane (F-338pcc) and 1,1,1-trifluoropentane (F-356mff) are preferable.

Particularly preferred fluorohydrocarbons are 1,1,
1,2-tetrafluoroethane (F-134a), 1,
1,1,2,2-pentafluoroethane (F-12
5), 1,2-difluorobutane (F-245fa),
1,1-difluorobutane (F-245eb) or 1,
It is 1,2-trifluorobutane (F-236ea). The above-mentioned fluorohydrocarbons may be used alone or in combination of two or more.

The expandable polypropylene resin particles for providing the polypropylene pre-expanded resin particles of the present invention preferably contain a foaming agent in an amount of 1 to 8% by weight, preferably 2 to 5% by weight. The impregnated amount of this foaming agent is smaller than the impregnated amount of hydrocarbon and chlorinated fluorohydrocarbon (the initial impregnated amount of hydrocarbon and chlorinated fluorohydrocarbon is
About 10 wt% and about 15 wt% respectively). However, when the change in the impregnated amount with time is measured, hydrocarbons and chlorinated fluorohydrocarbons rapidly dissipate, whereas the fluorohydrocarbon used in the present invention has an extremely slow dissipation rate. Therefore, in the conventional foaming agent composed of hydrocarbon and chlorinated fluorohydrocarbon, foaming is performed immediately after impregnation. In the present invention, since the foaming agent remains sufficiently in the polypropylene resin particles, it is not necessary to immediately perform foaming as in the conventional case.

The impregnation of the base resin particles with the foaming agent can be carried out by a method of press-fitting the foaming agent into the base resin particles in a pressure-resistant airtight container. The impregnation with the foaming agent is 60 to 150.
C., preferably 80 to 120.degree. C. 6
If the temperature is lower than 0 ° C, the impregnation time becomes long, which is not preferable. Further, the impregnation time varies depending on the size of the base resin particles, but in the case of particles of about 2 mm ³ , it is 3 hours or longer, preferably 6 hours or longer. When the impregnation time is less than 3 hours, an unimpregnated portion is formed in the central portion of the base resin particles, and when the pre-expanded resin particles are used,
Since the foamed portion and the unfoamed portion are mixed in one pre-expanded resin particle, the polypropylene resin foam molded article obtained from the pre-expanded resin particle does not have desired physical properties, which is not preferable.

In the above aqueous medium, various additives usually used for forming expandable polypropylene resin particles, for example, dispersants, surfactants, foaming aids (solvents, plasticizers), suspensions. Agents, lubricants and the like can be added. Here, examples of the dispersant include magnesium pyrophosphate and the like. Examples of the surfactant include sodium dodecylbenzene sulfonate and the like.

Examples of the foaming aid include toluene, ethylbenzene, cyclohexane, isoparaffin and the like. The expandable polypropylene resin particles obtained by the above method can be directly used as a commercial product. In the present invention, the expandable polypropylene resin particles are pre-expanded to obtain 0.15 to 0.03 g / cm ³ ,
Preferably, polypropylene-based pre-expanded resin particles having a bulk density of 0.15 to 0.06 g / cm ³ can be obtained. Here, when the bulk density is less than 0.03 g / cm ^{3, the} secondary foaming power is lowered, which is not preferable. Pre-foaming is
For example, in the pre-foaming device, the water vapor pressure is 1.5 to 5.0.
It is obtained by heating for 15 to 60 seconds in Kg / cm ² G. The polypropylene pre-expanded resin particles of the present invention,
Since the rate of escape of the foaming agent is extremely slow, the decrease in foaming power over time is small and the life of the particles is extended.

The polypropylene pre-expanded resin particles obtained by the above method can be directly used as a commercial product. Furthermore, in the present invention, the polypropylene-based pre-expanded resin particles are molded in a mold having a desired shape and capable of closing but not closing the polypropylene-based pre-expanded resin particles.
There is also provided a polypropylene-based resin foamed molded product obtained by foaming 8 to 3.0 times. Here, if it is less than 1.8 times, it is not preferable because the spaces between the polypropylene pre-expanded resin particles cannot be filled and defects such as dents and cracks occur in the foamed molded product. However, even if the expansion is 1.8 times or less without applying the internal pressure and compression filling, the expansion can be 1.8 times or more if the expansion is performed by applying the internal pressure and compression filling. It is preferable that the polypropylene pre-expanded resin particles be aged at room temperature for about 24 hours before being foam-molded and then foam-molded. Also, foam molding has a vapor pressure of 2.5 to 6.0K.
It can be carried out by heating g / cm ² G for 15 to 60 seconds. The obtained polypropylene resin foam-molded product is taken out of the mold after cooling.

Here, a more preferable polypropylene-based resin foam-molded article is obtained by foaming polypropylene-based pre-expanded resin particles having a foaming bulk ratio of 10 times or less during pre-expansion. When polypropylene-based pre-expanded resin particles larger than 10 times are used, it is preferable that internal pressure is applied and compression filling is performed during foam molding.

[0021]

EXAMPLES Examples and comparative examples will be described below. (1) Examples and Comparative Examples (impregnation amount and escape rate) 2000 g of water in a 5 liter autoclave, pellet-shaped (diameter 0.15 cm, length 0.2 cm) polypropylene resin particles (Sumitomo Chemical Co., Ltd., ethylene- Propylene Random Copolymer, Nobrene S-131, Density 0.89
g / cm ³ ) 1000 g, 0.5% by weight of inorganic dispersant /
Water and a surfactant of 0.02% by weight / water were charged and sealed, then, the mixture was stirred, and 1,1,1,2-tetrafluoroethane (F-134a) as a foaming agent was injected at 15% by weight / resin pressure. . Then, the temperature was raised to 95 ° C. and maintained for 10 hours for impregnation.

After the impregnation, it was cooled to 20 ° C. and degassed to take out the expandable polypropylene resin particles from the autoclave. After drying the resin particles, 20 ° C
It was placed in a constant temperature chamber of No. 2 and the rate of escape over time was measured. The results are shown in FIG. As a foaming agent, butane, isopentane,
1-chloro-1,1-difluoroethane (F-142
b), 1,1-dichloro-1-fluoroethane (F-1
41b), 2,2-dichloro-1,1,1-trifluoroethane (F-123), 1,2-difluorobutane (F-245fa), 1,1,2-trifluorobutane (F-236ea). In the same manner as above except that the above was used, the impregnation treatment was performed, and the escape rate with time was measured. The results are shown in FIG.

The amount of impregnation immediately after taking out is shown in Table 1.

[0024]

[Table 1]

Immediately after taking out from Table 1 above, a very large amount of hydrocarbons and chlorinated fluorohydrocarbons are impregnated, but only 3 to 4% by weight of fluorohydrocarbons is impregnated. Next, it can be seen from FIG. 1 that the fluorinated hydrocarbon has a significantly slower rate of escape as compared with the hydrocarbon and the chlorinated fluorinated hydrocarbon. This indicates that the fluorohydrocarbon does not have a great influence on the foaming property at the time of prefoaming with the passage of time.

Further, the impregnated amount of F-134a, F-245fa and F-236ea after standing for 24 hours was measured. The impregnated amounts were 1.9% by weight, 2.8% by weight and 3.4% by weight, respectively, and did not decrease significantly.

(2) Examples and Comparative Examples (Foamability of polypropylene pre-expanded resin particles over time) As a foaming agent, butane, F-142b, F-134a,
Expandable polypropylene resin particles were produced using F-236ea and F-245fa in the same manner as in Example (1). Immediately after taking out the obtained expandable polypropylene resin particles, the amount of impregnation was 10.0% by weight and 13.0%, respectively.
The content was 3.2% by weight, 4.2% by weight, 3.6% by weight.

After the expandable polypropylene resin particles are stored for a certain period of time, they are pre-expanded and stored for each foaming agent (butane and F-142b immediately after 5 hours, 1 hour).
After 3 days and 6 days, F-134a, F-236ea
And for F-245fa, immediately after 1 day, 3 days and 6
2 to 6 show the relationship between the foaming bulk ratio and the steam pressure in (after the day was measured).

Referring to FIGS. 2 and 3 of the comparative example, butane (FIG. 2) and F-142b (FIG. 3) have a narrow range of steam pressure capable of foaming over time, and the maximum foaming bulk ratio also decreases. . On the other hand, looking at FIGS.
-134a (Fig. 4), F-236ea (Fig. 5), F-2
The fluorinated hydrocarbon of 45fa (FIG. 6) was not significantly different in foaming property from the expandable polypropylene resin particles immediately after being taken out even after 6 days from the lapse of time.

(3) Examples and Comparative Examples (Escape Rate after Prefoaming) As the foaming agent, butane, F-142b, F-236e.
Using a, F-245fa and F-134a, expandable polypropylene resin particles were produced in the same manner as in the above-mentioned Example (1).

Then, the pre-expansion bulk ratio is 7 for butane.
F-142b is 7.6 times, F-134a is 6.0 times,
F-236ea was subjected to predetermined foaming conditions such that it was 6.0 times and F-245fa was 6.0 times. The time-dependent change in the impregnated amount of the blowing agent in the obtained polypropylene pre-expanded resin particles is shown in FIG. The storage temperature of the polypropylene pre-expanded resin particles was 20 ° C.

From FIG. 7, it was found that the fluorinated hydrocarbon had a slower escape rate in the polypropylene pre-expanded resin particles as compared with the hydrocarbon and the chlorinated fluorinated hydrocarbon.
This indicates that a foam-molded article can be stably obtained during foam molding.

(4) Examples and Comparative Examples (Secondary Foamability of Polypropylene Pre-Expanded Resin Particles) As a foaming agent, butane, F-142b, F-236e.
a, F-245fa, F-134a, and Example 1
Expandable polypropylene resin particles were produced in the same manner as in.

Next, the expandable polypropylene resin particles are added to 2
After leaving it for 4 hours, it was placed in a pressure foaming tank and foamed to obtain polypropylene pre-expanded resin particles having a predetermined bulk ratio. The polypropylene pre-expanded resin particles were aged at a predetermined temperature for 24 hours, placed in a pressure foaming tank, and heated at a predetermined steam pressure for 30 seconds to carry out secondary foaming. After cooling, the secondary expanded particles were taken out from the pressure foaming tank, and the expansion bulk ratio was measured.

Table 2 shows the pre-expansion bulk ratio, aging temperature, steam pressure, secondary expansion bulk ratio, and foamability ratio (bulk ratio of secondary expanded particles ÷ bulk ratio of pre-expanded resin particles) of each foaming agent.
showed that.

[0036]

[Table 2]

Here, in order to carry out foam molding without compression filling or application of internal pressure, the foamability ratio is 1.8 times or more. From this viewpoint, looking at Table 2, it is impossible to foam-mold the butane, which is a hydrocarbon, and F-142b, which is a chlorinated fluorohydrocarbon, as they are (Comparative Example). On the other hand, the fluorohydrocarbon used in the present invention exhibits a foaming ratio of at least twice, and can be foam-molded without compression filling or application of internal pressure.

Further, since the aging temperature of the polypropylene pre-expanded resin particles does not change at -1 ° C. or 20 ° C., it can be seen that a special device for maintaining the temperature is not required.

(5) Example In a 5-liter autoclave, 2000 g of water, 1000 g of pelletized polypropylene resin particles (Nobrene S-131 manufactured by Sumitomo Chemical Co., Ltd.), 0.5% by weight of inorganic dispersant /
Water and a surfactant of 0.02% by weight / water were charged and sealed, then, the mixture was stirred, and 1,1,1,2-tetrafluoroethane (F-134a) was injected at 15% by weight / resin pressure.
Then, the temperature was raised to 95 ° C. and maintained for 10 hours for impregnation.

After impregnation, the mixture was cooled to 20 ° C., degassed, and expandable polypropylene resin particles were taken out from the autoclave. The amount of the foaming agent impregnated immediately after taking out was measured and found to be 3.2% by weight. The expandable polypropylene resin particles were allowed to stand for 24 hours, placed in a pressure foaming tank, and foamed under the conditions of a steam pressure of 2.1 Kg / cm ² and a time of 30 seconds,
Polypropylene pre-expanded resin particles having an expanded bulk ratio of 6 were obtained.

Two parts of the polypropylene pre-expanded resin particles were
After leaving it at 0 ° C. for 24 hours, it was filled in a 300 mm × 400 mm mold and heated under the conditions of a steam pressure of 3.0 Kg / cm ² and a time of 30 seconds for foam molding. The polypropylene resin foam-molded product taken out after cooling had a bulk density of 0.16 g / cm ³ in which particles were sufficiently fused.

[0042]

Further, in the polypropylene pre-expanded resin particles of the present invention, the base resin particles are polypropylene resin and the blowing agent is a hydrocarbon having 2 to 6 carbon atoms substituted with at least two fluorine atoms. The pre-expanded resin particles after the pre-expansion have a bulk density of 0.15 to 0.03 g / cm ³ .

Therefore, pre-expanded resin particles having an extremely slow escape rate of the foaming agent can be obtained, so that it is not necessary to subject the pre-expanded resin particles to foam molding immediately after the pre-expansion, and the foamability of the pre-expanded resin particles can be improved. it can. Further, the foaming agent used in the present invention has no fear of environmental damage such as ozone layer destruction. Further, the blowing agent is 1,1,1,2-tetrafluoroethane (F-134a), 1,1,1,2,2-pentafluoroethane (F-125), 1,2-difluorobutane (F -245fa), 1,1-difluorobutane (F-245eb) and 1,1,2-trifluorobutane (F-236ea), and a polypropylene system having a slower escape rate by containing one or more of them. Pre-expanded resin particles can be obtained.

Further, in the polypropylene resin foam-molded product of the present invention, the base resin particles are made of polypropylene resin, and the foaming agent is mainly a hydrocarbon having 2 to 6 carbon atoms substituted with at least two fluorine atoms. Contained as an ingredient, and 0.
It is characterized by being obtained by expanding pre-expanded resin particles having a bulk density of 15 to 0.03 g / cm ³ 1.8 to 3.0 times.

Therefore, it is possible to obtain a polypropylene resin foam-molded article having no dents or cracks. Furthermore, in the method for producing a polypropylene-based resin foam-molded article of the present invention, the base resin particles made of a polypropylene-based resin are mainly composed of a hydrocarbon having 2 to 6 carbon atoms and substituted with at least two fluorine atoms. After impregnating with a foaming agent and pre-foaming it to obtain pre-expanded resin particles having a bulk density of 0.15 to 0.03 g / cm ³ , the pre-expanded resin particles are then used as they are in a desired molding die. It is characterized in that foam molding is performed 1.8 to 3.0 times.

Therefore, it is possible to obtain a polypropylene resin foam-molded article having no dents or cracks. Further, since the foam molding is carried out without applying the internal pressure and compressing and filling, a device for applying the internal pressure and compressing and filling is not required, so that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the escape rate with time of expandable polypropylene resin particles of Examples and Comparative Examples.

FIG. 2 is a graph showing the relationship between foaming bulk ratio and water vapor pressure over time for a foaming agent (butane) of a comparative example.

FIG. 3 is a graph showing the relationship between foaming bulk ratio and water vapor pressure over time for a foaming agent (F-142b) of a comparative example.

FIG. 4 is a graph showing the relationship between foaming bulk ratio and water vapor pressure over time for the foaming agent (F-134a) of the example.

FIG. 5 is a graph showing the relationship between foaming bulk ratio and water vapor pressure over time for the foaming agent (F-236ea) of the example.

FIG. 6 is a graph showing the relationship between foaming bulk ratio and water vapor pressure over time for the foaming agent (F-245fa) of the example.

FIG. 7 is a graph showing changes over time in the impregnated amount of a foaming agent in pre-expanded resin particles of Examples and Comparative Examples.

Claims (5)

[Claims] 1. A base resin particle is a polypropylene resin, a foaming agent is a hydrocarbon having 2 to 6 carbon atoms substituted with at least two fluorine atoms, and pre-expanded resin particles after pre-expansion are 0.15. Polypropylene pre-expanded resin particles having a bulk density of about 0.03 g / cm ³ . 2. The blowing agent is 1,1,1,2-tetrafluoroethane, 1,1,1,2,2-pentafluoroethane, 1,2-difluorobutane, 1,1-difluorobutane and 1 , 1,2-trifluorobutane, or 2
The resin particles according to claim 1, which are one or more kinds. 3. A base resin particle is a polypropylene resin, and a foaming agent is a hydrocarbon having 2 to 6 carbon atoms substituted with at least 2 or more fluorine atoms, and 0.15 to 0.03 g /
A polypropylene-based resin foam molded article obtained by expanding pre-expanded resin particles having a bulk density of cm ³ to 1.8 to 3.0 times. 4. A base resin particle made of a polypropylene resin is impregnated with a foaming agent whose main component is a hydrocarbon having 2 to 6 carbon atoms substituted with at least two fluorine atoms, and pre-foamed. Let 0.15-0.03g / cm
After obtaining the pre-expanded resin particles having a bulk density of ^3, the pre-expanded resin particles are then used as they are in a desired mold for 1.8.
A method for producing a polypropylene-based resin foam-molded article, which comprises foam-molding to 3.0 times. 5. The manufacturing method according to claim 5, wherein the foam molding is performed without applying internal pressure and compression filling.