JPH10306173A - Propylene resin particle for foam molding, foamable propylene resin particle, prefoamed propylene resin particle, and molded propylene resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain prefoamed particles which gives a molded foam having a low density and improved heat resistance and rigidity without causing the problems with the uniformity and reproducibility of the foam by specifying the m.p., the ratio of Z average mol.wt. to wt. average mol.wt., and the melt index. SOLUTION: The propylene resin particles for foam molding have an m.p. of 155-165 deg.C, a ratio (Mz/Mw) of Z average mol.wt. (Mz) to wt. average mol.wt. (Mw) of 3-6, and a melt index of 10-150 g/10 min. The foamable propylene resin particles are prepd. by incorporating a blowing agent into the foregoing particles and give, when prefoamed, the prefoamed propylene resin particles having a bulk density of 0.2-0.025 g/cm<3> and an open cell content of 0-30%. The prefoamed particles are foamed and molded to give the molded propylene resin foam having a density of 0.3-0.03 g/cm<3> . The propylene resin particles for foam molding are spherical particles, etc., having an average diameter of 0.5-8.0 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed propylene resin article having cushioning properties, heat resistance and excellent rigidity, and to resin particles, foamable particles and pre-expanded particles for obtaining the foamed article. In particular, the present invention relates to propylene-based resin particles, expandable particles, pre-expanded particles, and expanded molded articles that can be easily expanded and molded to a low density.

[0002]

2. Description of the Related Art Hitherto, foamed molded articles obtained by molding propylene-based resin foamed particles have been widely used as foams having excellent lightness, cushioning properties, chemical resistance and the like. As a method for obtaining such a propylene-based resin foam molded article,
For example, Japanese Patent Application Laid-Open No. Hei 8-259724 discloses that as a foamed polypropylene resin particle, a foaming agent is used in a resin in which a specific amount of ethylene and butene-1 are contained as a comonomer component in a polypropylene resin, and the foamed particles are sealed in a closed container. The resin is dispersed in an aqueous medium containing the resin and the dispersant, and while the pressure in the container is maintained at or above the vapor pressure of the foaming agent, the resin is heated to the softening temperature or higher, and then the pressure in the container is increased. It is described that pre-expanded particles could be produced by a so-called docan method of producing pre-expanded particles by discharging the particles into a low-pressure atmosphere without depressurizing to produce pre-expanded particles.

Further, Japanese Patent Application Laid-Open No. 8-277340 discloses that a special polypropylene homopolymer having a specific tensile modulus and a high temperature peak having a peak calorie of 30 to 60 J / g in a DSC curve is used. Moreover, it describes that pre-expanded particles can be produced by using the same docan method as described above, and that an expanded molded article is produced by using the pre-expanded particles.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. Hei 8-2
No. 59724, a foamed molded article using a propylene copolymer containing an olefin such as ethylene or 1-butene has a heat resistance and a molded article because the base resin is the copolymer as described above. However, in terms of the rigidity of the steel, it was still insufficient. In addition, since it is necessary to use the docan method to obtain the pre-expanded particles, special equipment is required, and the pressure inside the pressure-tight container is instantaneously released to the low-pressure region without reducing the pressure inside the container. It is necessary to pay close attention to the safety of work because it is foamed, and it is necessary to control this because the temperature of the resin at the time of foaming and the pressure in the container at the beginning and end of the discharge change easily. If such conditions are not strictly controlled, pre-expanded particles having a uniform bulk density cannot be obtained.

[0005] Further, as disclosed in JP-A-8-277340, a foam molded article using a polypropylene homopolymer can be made to have excellent heat resistance and rigidity. It was necessary to use a special polypropylene homopolymer having a specific tensile modulus and a high temperature peak having a peak calorie of 30 to 60 J / g in a DSC curve by a special polymerization method. Furthermore, since the same docan method as described above had to be used, special equipment was required.In addition, without releasing the pressure inside the container from the pressure-resistant sealed container, it was instantaneously released to the low pressure region and foamed. It is necessary to pay close attention to the safety of work, and it is difficult to control this because the temperature of the resin at the time of foaming and the pressure in the container at the beginning and end of the release change easily and this is difficult. The problem that the pre-expanded particles having a uniform bulk density cannot be obtained unless the conditions are strictly controlled has not been solved yet.

According to the present invention, the peak heat quantity on the specific tensile modulus and the DSC curve, which are the above problems, is 30 to 60 J /.
g without using a special polypropylene homopolymer having a high-temperature peak, and without requiring special equipment for the production of pre-expanded particles, and furthermore, a docan method having problems in uniformity and reproducibility. It is an object of the present invention to obtain a foamed molded article having a small foaming density easily and having excellent heat resistance and rigidity without using a conventional method such as a bead foaming method. Things. As used herein, the bead foaming method means that a propylene-based resin is dispersed in an aqueous medium having a dispersant in a closed container, and then the foaming agent is supplied, and the foaming agent is impregnated in the resin under the vapor pressure of the foaming agent. After cooling and depressurizing, the foamed resin particles are separated from the aqueous medium to produce foamable resin particles.Then, the foamable resin particles are heated to a temperature higher than the softening temperature of the resin with a heat medium such as steam to foam the prefoamed particles. It is a method of manufacturing.

[0007]

The present invention has a melting point of 155.
Foam molding, characterized in that Mz / Mw, which is the ratio between the weight average molecular weight (Mw) and the Z average molecular weight (Mz), is 3 to 6 and the melt index is 10 to 150 g / 10 min. Propylene-based resin particles for use, expandable propylene-based resin particles characterized by containing a foaming agent in the resin particles, and a bulk density obtained by pre-expanding the expandable propylene-based resin particles is 0.2 to 0.025.
g / cm < ³ > and an open cell ratio of 0 to 30%, and a propylene-based resin pre-expanded particle having a density of 0.3 to 0. It is a propylene-based resin foam molded article of 03 g / cm ³ .

The propylene resin particles for foam molding of the present invention have a melting point of 155 to 165 ° C. and a weight average molecular weight (Mw).
And Mz / Mw, which is the ratio of Z and M average molecular weight (Mz), is 3 to
6, and the melt index (hereinafter referred to as MI) needs to be 10 to 150 g / 10 min. If the MI is less than 10, it is difficult to obtain low-density pre-expanded particles, and if it is 150 or more, the shape of the propylene particles for foaming tends to be unstable, which is not preferable. More preferred MI
Ranges from 20 to 150 g / 10 min. Also, M
When z / Mw is less than 3, expandable propylene-based resin particles using this as a base resin are foamed, and a molded article obtained only has poor fusion and surface elongation of the molded article.
When Mw exceeds 6, it is difficult to obtain low density pre-expanded particles, which is not preferable. The melting point is 155 ° C
If the temperature is lower, the heat resistance of the obtained foamed molded article becomes insufficient. If the melting point is higher than 165 ° C, the steam pressure at the time of heating needs to be extremely high when foaming is performed, and the production equipment becomes expensive. However, it is difficult to obtain low density pre-expanded particles, which is not preferable.

The size of the propylene-based resin particles for foaming is not particularly limited, but the average diameter of the particles is about 0.1.
A spherical shape, an elliptical spherical shape, a pellet shape, or the like having a size of 5 to 8.0 mm can be used. As a method for obtaining the resin particles of the present invention, for example, a commercially available resin having a melting point of 155 to 165 ° C. and a ratio Mz / Mw of 3 to 6 which is a ratio of a weight average molecular weight (Mw) to a Z average molecular weight (Mz) is generally used. Can be obtained by subjecting the propylene-based resin to a heat treatment so that the MI is 10 to 150 g / 10 min. Such a heat treatment is specifically, for example, a method of heat-treating a propylene-based resin and a radical generator in an aqueous medium having a dispersant, or a method of extruding a propylene-based resin and a radical generator using an extruder. A method of extruding by heating, melting, mixing, and the like can be given. However, it is not limited to these. Among these methods, a method of extruding using an extruder is preferable because resin particles having an arbitrary size can be processed simultaneously with the heat treatment. The radical generator is prepared by mixing a propylene-based resin and an organic peroxide in advance with a mixer such as a V blender, a Nauta mixer or a spar mixer, and then putting the mixture into an extruder, or a method in which the propylene resin and the organic peroxide are mixed. And the like can be appropriately employed. When the propylene resin and the organic peroxide are mixed by a mixer, it is preferable to use a small amount of a spreading agent such as butene 1.

The propylene resin usable in the present invention includes:
Melting point 155-165 ° C, weight average molecular weight (Mw) and Z
The ratio is not particularly limited as long as Mz / Mw, which is the ratio to the average molecular weight (Mz), is 3 to 6, but a propylene homopolymer is preferable. In addition, a block copolymer with one or more olefins such as ethylene, 1-butene, or another α-olefin, ethylene, 1-butene, or another α-olefin, particularly, in a range where the melting point does not exceed 155 to 165 ° C. A propylene random copolymer containing a small amount of one or two or more olefins can also be used.

The radical generator to be added in order to obtain the resin particles of the present invention is preferably an organic peroxide which generates free radicals by heat. Among them, a decomposition temperature when the decomposition half-life is 1 minute is preferable. Is preferably 120 ° C. or higher, more preferably 150 ° C. or higher.
Specific examples include methyl ethyl ketone peroxide, t-butyl peroxyisopropyl carbonate, dicumyl peroxide, cumene hydrohardoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2 , 5-di (t-butylperoxy) hexyne-3, di-t-butylperoxyphthalate, and the like. These can be used alone or in combination of two or more. The amount of the organic peroxide to be added is not particularly limited. However, it is necessary to add the organic peroxide in such an amount that the MI of the polypropylene particles can be controlled in the range of 10 to 150 g / 10 min. The method of adding to the extruder is adjusted depending on the type of the peroxide and the extrusion conditions.
It is preferably used in an amount of from 0.01 to 1.0% by weight, more preferably from 0.025 to 0.2% by weight.

The propylene resin particles for foaming of the present invention may contain various additives, if necessary, such as fillers (silica, alumina, titanium oxide, talc, clay, calcium carbonate, etc.), lubricants (liquid paraffin, Fatty acid esters,
Metal soaps) Flame retardants, flame retardant auxiliaries, antistatic agents and the like can also be added.

The expandable propylene resin particles of the present invention include:
By dispersing the propylene-based resin particles for foam molding in an aqueous medium having a dispersant in a closed pressure-resistant container, by impregnating the foaming agent and contacting it at 60 to 150 ° C., the resin particles are impregnated with the foaming agent, After cooling and depressurizing, it can be obtained separately from the aqueous medium. At this time, various additives, dispersing aids, foaming aids, lubricants and the like can be added.

Examples of the foaming agent that can be used in the present invention include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane and hexane; cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane; Halogenated hydrocarbons such as methylene chloride and ethyl chloride, halogenated fluorocarbons such as trichlorofluoromethane, dichlorodifluoromethane and dichlorotetrafluoromethane, 1.1.1.2-tetrafluoromethane (F-134a) , 1.1.1.2.2.2-pentafluoroethane (F-125), 1.2 difluorobutane (F-245fa), 1.1 difluorobutane (f-2)
45eb), 1.1.2 trifluorobutane (F-23)
Carbon number 2 substituted by two or more fluorine atoms, such as 6fa)
To 6 fluorine-based hydrocarbons, nitrogen, carbon dioxide, inorganic gases such as air, and mixtures thereof. Among them 2
Since the fluorinated hydrocarbon having 2 to 6 carbon atoms substituted by the above-mentioned fluorine atom has a very low rate of escape from the propylene-based resin particles, the expandable propylene-based resin particles containing the blowing agent may contain other blowing agents. Unlike the expandable resin particles containing, it is not necessary to foam immediately after the impregnation to form pre-expanded particles. Further, since the pre-expanded particles are excellent in secondary foaming power, they can be particularly preferably used because treatment such as applying an internal pressure to the pre-expanded particles with air or the like is not required before foam molding. However, the present invention does not deny processing such as applying an internal pressure to the pre-expanded particles with air or the like before foam molding. The content of the blowing agent in the expandable propylene resin particles is appropriately adjusted depending on the type of the blowing agent.
It is preferably 5% by weight, more preferably about 3 to 10% by weight.

As the dispersing agent, inorganic fine powders which are hardly soluble in water, such as metathesis-processed magnesium pyrophosphate, magnesium oxide and tribasic calcium phosphate, can be used. Further, an anionic surfactant such as sodium dodecylbenzenesulfonate can be used in combination as a dispersing aid. Examples of the foaming aid include toluene, ethylbenzene, cyclohexane, and isoparaffin. Examples of the lubricant include fatty acid esters and metal soaps.

The pre-expanded propylene resin particles of the present invention can be obtained by heating the expandable propylene resin particles obtained as described above to a temperature above the softening temperature of the resin with a heat medium such as steam to expand the particles. . The propylene-based resin pre-expanded particles of the present invention have a bulk density of 0.2 to 0.025 g / c.
m ³ and the open cell ratio must be 0 to 30%.
If the bulk density is more than 0.2 g / cm ^3, it is difficult to obtain pre-expanded particles having a uniform density, which is not preferable.
If it is less than 0.025 g / cm ³ , the open cell rate is undesirably high. On the other hand, if the open cell ratio is larger than 30%, the surface elongation of the molded article obtained by foaming is reduced.
It must be in the range of ~ 30%. The propylene-based resin pre-expanded particles of the present invention can be prepared, for example, in a pre-expansion tank having a pressure resistance of about 3.0 to 5.0 kg / cm ² gauge pressure (about 14 kg / cm ^2).
3 to 158 ° C), and heating time is about 10 to 10 minutes.
It can be obtained by setting it to 60 seconds.

The foamed propylene-based resin article of the present invention comprises:
It can be obtained by subjecting the above-mentioned propylene-based resin pre-expanded particles to foam molding. The pre-expanded particles are heated and foamed about 1.8 to 3.0 times in a mold that can be closed but cannot be closed, so that a propylene foam molded article having a density of 0.3 to 0.03 g / cm ³ is obtained. Can be manufactured. Specifically, about 3.0 to 6.0 kg is placed in a mold for foam molding.
A foamed molded article can be obtained by heating the steam at a pressure of about 10 to 60 seconds at a pressure of / cm ² · gauge pressure. When the density of the propylene-based foam molded article of the present invention is more than 0.3 g / cm ^3, it is difficult to obtain a molded article having a uniform density, which is not preferable. When the density is less than 0.03 g / cm ^3. It is not preferable because only a molded article having poor fusion and poor surface elongation is difficult to obtain.

[0018]

Embodiment

(Examples) Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Embodiment 1 FIG. Melting point: 160 ° C., weight average molecular weight (Mw): 740,000, Mz / Mw: 5.0, MI: 3 g / 10 min
Polypropylene (Himont PF-814) and
2,5-dimethyl 2,5 di (t-butylperoxy) hexane as a radical generator
0.1% by weight based on 0 part by weight, melt-kneaded using a twin screw extruder having a diameter of 30φ, extruded into a strand from a strand mold provided at the tip of the extruder, and then in water. After quenching, it was cut to obtain propylene resin particles for foam molding. At the time of extrusion, the cylinder temperature and the mold temperature of the extruder were set at 200 ° C. The obtained propylene-based resin particles for foam molding had a pellet shape with a diameter of 1.5 mm and a length of 2.0 mm. Table 1 shows the results of measuring the properties of the resin particles.

[0019]

[Table 1]

Next, in a 5-liter autoclave equipped with a stirrer, a dispersion comprising 1 kg of the above-mentioned pellet-shaped foam-forming propylene resin particles, 2 kg of water, 5 g of metathetically decomposed magnesium pyrophosphate, and 0.5 g of sodium dodecylbenzenesulfonate. And put in. Then, after sealing, 200 g of 1,1,1,2-tetrafluoroethane (F-134a) was injected as a foaming agent under stirring.
Subsequently, the temperature in the autoclave was set to about 95 ° C., and
After maintaining for a time, the temperature in the container was cooled to about 20 ° C., the pressure was reduced to normal pressure, and then the dispersion was separated to obtain expandable propylene resin particles containing a blowing agent.

Next, the obtained expandable polypropylene resin particles were subjected to a pressure of 4.0 and 4.6 kg / cm ² · g.
1, 155 ° C.) for about 30 seconds. Next, the pressure of the expandable polypropylene resin particles was adjusted to 4.4 kg / cm ² ··
Heating was performed for about 30 seconds with steam at a gauge pressure (about 154 ° C.) to obtain pre-expanded propylene resin particles having a bulk density of 0.040 g / cm 3. Table 1 shows the properties of the pre-expanded particles. The cell diameter of the pre-expanded particles was 30 to 100 μm.

After leaving the obtained pre-expanded particles at a temperature of about 10 ° C. for about 24 hours, a mold having a size of 300 × 400 ×
Fill into a foaming mold of 30mm, pressure 5.6kg
The foam was molded by heating for about 15 seconds with steam at a pressure of / cm ² · gauge pressure and then cooled, and then taken out of the mold to obtain a foam molded article. The density of the obtained foamed molded article is 0.045.
g / cm ³ . Table 1 shows the physical properties of the foam molded article.

The methods for measuring and evaluating the properties of the propylene resin particles for foam molding and the physical properties of the foam molded article are as follows.
The following method was used. (Method of Measuring Melting Point) The endothermic peak temperature of the DSC curve obtained by differential scanning calorimetry was defined as the melting point. Specifically, 2 to 4 mg of resin particles were used as a sample, and 10
The temperature was raised from room temperature to 220 ° C. at a rate of ° C./min to obtain a DSC curve. The temperature of the endothermic peak observed on this curve was defined as the melting point of the polymer.

(Method of Measuring Weight Average Molecular Weight (Mw) and Z Average Molecular Weight (Mz)) The weight average molecular weight (Mw) and the Z average molecular weight (Mz) were determined by Luper-Mation Chromatography. The specific conditions are as follows. Measurement device: Waters, GPC 150-C type Measurement condition: Column KF-80M 2 pieces (SHO
DEX) Column temperature: 145 ° C. Inject. Temperature: 145 ° C Pump temperature: 60 ° C Sensitivity: 32 Solvent used: O-dichlorobenzene (1.0 ml)
/ Min) Run time: 50 minutes Inject. Volume: 400 μl Mw / Mz was calculated based on Mw and Mz obtained here.

(Method of Measuring MI) Test condition No. JIS K7210 14 was carried out.

(Measurement method of open cell ratio) Using an air comparison type specific gravity meter 1000 (manufactured by Tokyo Science), it was calculated from the following equation. Open cell ratio (%) = (apparent volume-measured value) 体積 apparent volume × 100 Apparent volume: Volume value calculated by measuring thickness, length and width of the sample with calipers Measured value: 1-1 / 2-1 Volume value measured with air comparison hydrometer by barometric method

(Method of Measuring Heating Dimensions) A test piece obtained by cutting the obtained molded body into 150 mm in length, 150 mm in width and 25 mm in thickness was used, except that the measurement temperature was 120 ± 1 ° C. The heating dimensional change was measured in accordance with JIS K6767.

(Method of Evaluating Degree of Fusion) The obtained molded body was broken in the thickness direction, and the ratio of material fracture to the fractured surface was visually judged. When the ratio was 50% or more, it was evaluated as ○, and when it was less than 50%, it was evaluated as ×.

(Evaluation method of surface elongation) The surface condition of the obtained molded article was visually observed and evaluated according to the following criteria. When there is almost no unevenness between the foamed particles ... ○ When there is partial unevenness between the foamed particles ... 場合 When there is unevenness between all the foamed particles ...

(Method of Measuring 50% Compressive Strength) Using a test piece obtained by cutting the obtained foam to a length of 50 mm and a width of 50 mm and the thickness to the original size, the compressive stress was measured in accordance with JIS K6767, and the base of the sample was measured. The stress when compressed 50% of the thickness of the sample was defined as 50% compressive strength.

Embodiment 2 and Embodiment 3. Using the same expandable propylene resin particles as those obtained in Example 1, pre-expanded particles having a bulk density of 0.1 and 0.06 g / cm ³ were produced, and were foamed and foamed in the same manner. Foamed molded articles having densities of 0.11 and 0.062 g / cm ³ were obtained. Table 1 shows the results.

Embodiments 4-7. 2, a radical generator,
5-Dimethyl 2,5 di (t-butylperoxy) hexane was added to polypropylene at 0.025 and 0.
Propylene resin particles for foam molding were obtained in the same manner as in Example 1 except that the propylene-based resin particles were used in the same manner as in Example 1 except that the propylene resin particles were used in an amount of 0.05, 0.15, and 0.20% by weight.
This was made into expandable propylene-based resin particles in the same manner as in Example 1, and propylene-based resin pre-expanded particles and expanded molded articles were obtained in the same manner. Table 1 shows these characteristics and performance.

Embodiment 8 FIG. Example 1 Expandable propylene resin particles were obtained in the same manner as in Example 1 except that butane was used as a blowing agent in the obtained propylene resin particles for foam molding. Then, it was heated for 30 seconds with steam (approximately 156 ° C.) at a pressure of 4.7 kg / cm ² gauge to obtain a bulk density of 0.04 g.
/ Cm ³ of pre-expanded particles. The pre-expanded particles were pressurized with air in a closed container at a pressure of 4 kg / cm ² · gauge for 24 hours to apply an internal pressure to the polypropylene pre-expanded particles. The pre-expanded particles are subjected to a steam pressure of 5.5 kg /
A foam molded article was obtained in the same manner as in Example 1 except that the pressure was changed to cm ² · gauge pressure. Table 1 shows these characteristics and performance.
The cell diameter of the pre-expanded particles was 100 to 300 μm.

Comparative Example 1 Expandable propylene resin particles, pre-expanded particles, and expanded molded articles were obtained in the same manner as in Example 1, except that propylene-based resin particles for expansion molding were prepared without adding a radical generator. Table 1 shows these characteristics and performance.

Comparative Example 2 As a propylene resin, the melting point is 168 ° C., the weight average molecular weight (Mw) is 280,000, and Mz / M
w is 3.9 and MI is 50 g / 10 min. ethylene-propylene blockum copolymer resin (Sumitomo Chemical: AX9
Propylene resin particles for foam molding were obtained in the same manner as in Example 1 except that 61) was used. The obtained resin particles were heated with steam of 5.0 kg / cm ² · gauge pressure for 30 seconds to obtain pre-expanded particles of 0.1 g / cm ³ , and similarly, the steam pressure was reduced to 5.6 kg / cm ² · gauge pressure of 15 g / cm ^2. The foam was molded in the same manner by heating for 2 seconds, but it could not be taken out of the mold as a molded body, and the shape collapsed and a satisfactory molded body could not be obtained. Table 1 shows these characteristics and performance.

Comparative Example 3 As a propylene-based resin, the melting point is 163 ° C., the weight average molecular weight (Mw) is 42,000, and Mz is
/ Mw was 2.95, MI was 3 g / 10 min, using polypropylene (manufactured by Mitsui Petrochemical: J-400) in the same manner as in Example 1 except that no radical generator was added.
Propylene resin particles for foam molding were obtained. The resin particles were heated with steam at a pressure of 4.7 kg / cm ² · g for 30 seconds to obtain pre-expanded particles having a bulk specific gravity of 0.10 g / cm ^3. A foam molded article was obtained in the same manner as in Example 1. Table 1 shows these characteristics and performance.

Comparative Example 4 As a propylene-based resin, the melting point is 137 ° C., the weight average molecular weight (Mw) is 420,000, and Mz / M
w is 2.7 and MI is 1.2 g / 10 min. ethylene-propylene ramdam copolymer resin (ethylene content is 6
% By weight) and propylene resin particles for foam molding were obtained in the same manner as in Example 1 except that no radical generator was added. The obtained resin particles are heated with steam of 2.5 kg / cm ² · gauge pressure for 30 seconds to have a bulk specific gravity of 0.1 g / c.
m ³ pre-expanded particles, and the water vapor pressure is also 3.0 kg.
Similarly, a foamed molded product was obtained by heating at a pressure of / cm ² · gauge for 15 seconds. Table 1 shows these characteristics and performance.

Comparative Example 5 As a propylene-based resin, the melting point is 150 ° C, the weight average molecular weight (Mw) is 330,000, and Mz / M
An ethylene-propylene ramdam copolymer resin having an w of 2.6 and an MI of 7.5 g / 10 min (ethylene content of 2.
7% by weight) and propylene resin particles for foam molding were obtained in the same manner as in Example 1 except that no radical generator was added. The obtained resin particles are heated with 3.2 kg / cm ² · gauge pressure steam (about 145 ° C.) for 30 seconds to obtain pre-expanded particles having a bulk specific gravity of 0.088 g / cm ³ and a steam pressure of 4.0 kg / cm ^3. Heating was performed for 15 seconds at a pressure of cm ² · gauge to obtain a foamed molded product. Table 1 shows these characteristics and performance.

[0039]

According to the present invention, a specific tensile modulus and DSC
The use of a special polypropylene homopolymer having a high-temperature peak having a peak calorific value of 30 to 60 J / g in the curve without using a special equipment for producing the pre-expanded particles, Pre-expanded particles having a low expansion density can be easily and safely obtained by using a conventionally known bead expansion method or the like without using a docan method having problems in reproducibility and reproducibility. Further, the propylene-based resin foam molded article of the present invention is lightweight, cushioning,
The foam can have excellent heat resistance and rigidity as well as being excellent in chemical resistance and the like.

Claims (4)

[Claims] 1. A melting point of 155 to 165 ° C. and Mz / Mz which is a ratio of a weight average molecular weight (Mw) to a Z average molecular weight (Mz).
Mw is 3-6 and melt index is 10
A propylene-based resin particle for foam molding, which is 150 g / 10 min. 2. Mz / melting point of 155 to 165 ° C. and a ratio of weight average molecular weight (Mw) to Z average molecular weight (Mz).
Mw is 3-6 and melt index is 10
Foamable propylene-based resin particles characterized in that a blowing agent is added to propylene-based resin particles of 150 g / 10 min. 3. The pre-expanded bulk density of the expandable propylene resin particles according to claim 2 is 0.2 to 0.025 g /
Pre-expanded propylene-based resin particles having a cm ³ and an open cell ratio of 0 to 30%. 4. A foamed propylene-based resin having a density of 0.3 to 0.03 g / cm ³ obtained by foaming and molding the pre-expanded particles according to claim 3.