JPH11209501A - Antistatic polypropylene-based resin preexpanded particle, its production and expansion molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce both an expansion molded product capable of sustaining excellent antistatic effects for a long period and having excellent antistatic properties just after fracturing or washing with water thereof and a polypropylene-based resin preexpanded particle for producing the expansion molded product and to provide a method for producing the polypropylene-based resin preexpanded particle. SOLUTION: This polypropylene-based resin preexpanded particle is produced by mixing prescribed amounts of a polypropylene-based resin with a hydrophilic monomer represented by the following general formula [R<1> and R<2> denote each hydrogen or methyl group; (n) denotes an integer of 2-30], a radical polymerization initiator and a volatile foaming agent, melt kneading the resultant mixture, impregnating the prepared polypropylene-based resin particle with a volatile foaming agent and preexpanding the resultant impregnated resin particle. Furthermore, the preexpanded particle is obtained by dispersing the resin particle in an aqueous medium in a hermetically closed vessel, heating the resultant dispersion to the softening point or above of the resin particle and then releasing the heated dispersion into a low-pressure atmosphere. The expansion molded product is produced by carrying out the expansion molding of the preexpanded particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pre-expanded polypropylene resin particle having excellent antistatic properties, a method for producing the same, and a foamed molded article using the pre-expanded particle.

[0002]

2. Description of the Related Art Expanded molded articles of pre-expanded polypropylene resin particles are excellent in cushioning property, abrasion resistance and oil resistance, so that they are used as containers for passing mechanical parts such as automobile parts and buffer packaging materials for electric products. It's being used. However, the polypropylene-based resin also has excellent electrical insulation properties, and is easily charged by friction due to this. As a result, there is a problem that not only the dust easily adheres and the appearance of the foamed molded article is impaired, but also dust adheres to and contaminates mechanical parts and electric appliances stored or packaged in the foamed molded article.
In particular, adhesion of dust to electric products may cause electrostatic breakdown, and thus there is a problem in using a foamed product of a polypropylene resin as a packaging material for precision electronic components such as a liquid crystal display device.

In order to solve such a problem, conventionally,
(1) foam molding by applying an antistatic agent such as a low molecular surfactant to the surface of the pre-expanded particles or the foamed molded article, or (2) kneading the antistatic agent into a polypropylene resin. A method of reducing the resistivity of the body surface to prevent electrification has been adopted.

[0004]

SUMMARY OF THE INVENTION
In the method of (1), the antistatic agent on the surface is peeled off while using the foam molded article, and the antistatic effect is not maintained,
There is a problem that the antistatic agent is easily removed by washing the surface with water, and the antistatic performance is significantly reduced. Further, when the foam molded article is cracked or chipped, the problem that dust adheres cannot be solved because the antistatic property is not obtained or extremely low in the fracture surface immediately after the fracture.

On the other hand, in the method (2), since an antistatic agent is contained in the resin, a foam molded article having excellent durability of the antistatic effect can be obtained. However, when the foamed molded product is broken due to cracking or chipping, or when the antistatic agent on the surface is removed by washing with water or the like, the antistatic agent bleeds on the surface generated by the fracture or the surface from which the antistatic agent has been removed. Then, it takes several weeks for the surface to exhibit sufficient antistatic property again (Japanese Patent Laid-Open No. 3-2823).
No. 9).

Accordingly, an object of the present invention is to provide a foamed molded article having excellent antistatic properties, capable of maintaining the antistatic effect for a long period of time, and having good antistatic properties on the surface immediately after breaking or washing with water. An object of the present invention is to provide an antistatic polypropylene-based resin pre-expanded particle from which such an expanded molded article can be obtained, and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a polypropylene resin and a specific hydrophilic monomer represented by the following general formula (1) And, a predetermined amount of a radical polymerization initiator is blended and melt-kneaded, a volatile foaming agent is contained in the polypropylene resin particles thus obtained, and the pre-foamed particles obtained by pre-foaming the particles are excellent in chargeability. A new type of foam that exhibits antistatic properties over a long period of time and can produce a foam molded article that exhibits excellent antistatic properties even immediately after a fracture surface is generated by cracking or chipping or an antistatic agent is removed by washing with water. Having found the facts, they have completed the present invention.

That is, the antistatic polypropylene-based pre-expanded particles of the present invention comprise 100 parts by weight of a polypropylene-based resin and a general formula (1):

[0009]

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(Wherein, R ¹ and R ² are the same or different and each represent hydrogen or a methyl group, and n represents an integer of 2 to 30). 1-20 parts by weight of a monomer composed of an ester and 0.05-5 parts by weight of a radical polymerization initiator were melt-kneaded and polypropylene resin particles obtained were impregnated with a volatile blowing agent and prefoamed. Characterized in that:

The method for producing the pre-expanded particles of the antistatic polypropylene-based resin of the present invention is characterized in that 100 parts by weight of the polypropylene-based resin is mixed with polyethylene glycol and (meth) acrylic acid represented by the above general formula (1). Is melt-kneaded with 1 to 20 parts by weight of an ester monomer and 0.05 to 5 parts by weight of a radical polymerization initiator, and the obtained polypropylene-based resin particles are dispersed in a closed container with a volatile foaming agent and a dispersion stabilizer. After dispersing the resin particles in an aqueous medium and heating to a temperature above the temperature at which the polypropylene resin particles soften to impregnate the volatile foaming agent, one end of the closed container is opened and the resin particles are exposed to a low-pressure atmosphere outside the container. To perform prefoaming.

The pre-expanded antistatic polypropylene resin particles obtained by such a production method exhibit excellent antistatic properties over a long period of time as described above, and exhibit excellent antistatic properties even immediately after breaking or washing with water. A molded article can be manufactured. Further, the foamed molded article of the present invention is characterized in that the antistatic polypropylene resin pre-expanded particles are subjected to foam molding.

The foamed molded article of the present invention has excellent antistatic properties, maintains an antistatic effect for a long period of time, and exhibits excellent antistatic properties immediately after breaking due to cracking or chipping or even after washing with water. be able to.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the pre-expanded particles of the antistatic polypropylene resin of the present invention will be described in detail.
Examples of the polypropylene resin used in the antistatic polypropylene resin pre-expanded particles of the present invention (hereinafter, referred to as “pre-expanded particles”) include propylene homopolymer and copolymers of propylene and other monomers. can give. In particular, a random copolymer containing 90 to 99% by weight of propylene is preferable.

Specific examples of the other monomer include carbon numbers such as ethylene, butene-1, isobutene, pentene-1, hexene-1, 3-methyl-pentene-1, octene-1, and decene-1. Is an α-olefin having 2 or 4 to 12; a cyclic olefin such as cyclopentene and norbornene; a diene monomer such as 5-methylene-2-norbornene, 5-ethylidene-2-norbornene and 1,4-hexadiene; acrylic acid , Methacrylic acid, maleic acid,
Examples include vinyl monomers such as maleic anhydride, ethyl acrylate, methyl methacrylate, and glycyl methacrylate, and one or more of these are used. Among the above examples, ethylene or butene-1 is particularly preferable because it is inexpensive.

The hydrophilic monomer used for the pre-expanded particles of the present invention is a monomer composed of an ester having a hydrophilic group in the molecule, and is specifically represented by the general formula (1). As described above, a monomer composed of an ester of (meth) acrylic acid and polyethylene glycol (hereinafter, simply referred to as “hydrophilic monomer”) may be used. The hydrophilic monomer has a general formula (10):

[0017]

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And the general formula (11):

[0019]

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These are used singly or as a mixture. Suitably, the number of repeating units in the hydrophilic monomer represented by the general formula (1), that is, the number n of polyethylene oxide groups is 2 to 30. If n is less than the above range, a sufficient antistatic effect cannot be obtained. Conversely, if n exceeds the above range, the reactivity decreases, and the antistatic property of the foamed molded article decreases.

In the hydrophilic monomer represented by the general formula (10), the number n is preferably 2 to 14 even within the above range. On the other hand, in the hydrophilic monomer represented by the general formula (11), the number n is preferably 9 to 20 even in the above range. Incidentally, the ester of (meth) acrylic acid and polyethylene glycol sometimes contains a small amount of diester by-produced in the production process. This diester acts as a cross-linking agent, and the resulting polymer may have a cross-linked structure, but the present application is not particularly limited to the presence or absence of a cross-linked structure.

The amount of the hydrophilic monomer used is 1 to 20 parts by weight based on 100 parts by weight of the polypropylene resin.
Preferably it is 3 to 15 parts by weight. When the content of the hydrophilic monomer is less than 1 part by weight, the improvement of the antistatic effect becomes insufficient. On the other hand, even if the hydrophilic monomer is added in an amount exceeding 20 parts by weight, not only the antistatic effect is not further improved, but also a foam molded article having good fusion properties when pre-expanded particles are molded is obtained. And the mechanical strength is rather reduced.
Further, there is also a problem that the dimensional shrinkage ratio after molding becomes high and becomes unsuitable for practical use.

In the present invention, a vinyl monomer copolymerizable with the above hydrophilic monomer may be used in combination. Such vinyl monomers include, for example, styrene monomers such as styrene, α-methylstyrene, p-methylstyrene;
Methyl acrylate, butyl acrylate, acrylic acid-2
-Acrylates such as ethylhexyl and glycyl acrylate; methacrylates such as methyl methacrylate, propyl methacrylate and glycyl-2-ethylhexyl methacrylate; and organic acids such as acrylic acid, methacrylic acid and maleic anhydride. And maleimide monomers such as maleimide, maleimide, N-phenylmaleimide and N-cyclohexylmaleimide; and diene monomers such as butadiene and isoprene. These are 1
Species or two or more species can be selected and used in combination.

When the above-mentioned vinyl monomer is used in combination, the proportion of the vinyl monomer used is set within a range of less than 50 mol% based on the total amount of the above-mentioned hydrophilic monomer. Examples of the radical polymerization initiator used in the present invention include 1,1
-Di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, 2,2-bis (4,4-di-t-
Butylperoxycyclohexyl) propane, diethylene glycol bis (t-butylperoxycarbonate), t-butylperoxyisopropylcarbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,2-di ( t-butyl peroxy)
Butane, t-butylperoxybenzoate, di-t-
Butylperoxyisophthalate, tris (t-butylperoxy) triazine, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, dicumyl peroxide, 2,5-dimethyl-2,5- Di (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-
Organic peroxides such as 3,1'-azobis (1-cyclohexanecarbonitrile), 2,2'-azobis (2,
4,4-trimethylpentane), 2-phenylazo-
Examples include azo compounds such as 2,4-dimethyl-4-methoxyvaleronitrile, and these may be used alone or as a mixture of two or more.

The radical polymerization initiator exemplified above is particularly preferably one having a one-minute half-life temperature of 160 ° C. or more from the viewpoint of effectively generating radicals under the temperature conditions at which the polypropylene resin melts. The amount of the radical polymerization initiator used is 100
0.05 to 5 parts by weight, preferably 0.3 to 5 parts by weight
３3 parts by weight. When the content of the radical polymerization initiator is 0.
When the amount is less than 05 parts by weight, the effect as an initiator is not substantially exhibited. Conversely, if the content exceeds 5 parts by weight, a favorable foamed molded article tends to be unable to be obtained, for example, because the foamed molded article tends to shrink, which is not preferable.

The volatile blowing agent used in the present invention includes, for example, propane, butane, isobutane, pentane,
Hydrocarbons such as isopentane, cyclopentane, hexane and heptane; monochlorodifluoroethane (HCFC-
142b), dichlorotrifluoroethane (HCFC-
123), tetrafluoroethane (HFC-134
a), pentafluoropropane (HFC-245fa)
Carbon dioxide gas, nitrogen gas, air and the like, and these are used alone or in combination of two or more.

The amount of the foaming agent to be used is preferably set in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the polypropylene resin particles. It is appropriately set in consideration of the heating temperature (foaming temperature) of the product. For the purpose of preventing coalescence of the resin particles when producing the polypropylene-based resin particles, the resin particles of the present invention can contain a coalescence inhibitor. As the coalescing inhibitor, a poorly water-soluble inorganic compound is generally used, for example, tricalcium phosphate,
Examples include magnesium pyrophosphate, aluminum oxide, magnesium oxide, titanium oxide, aluminum hydroxide and the like. The use amount of the coalescing inhibitor is usually preferably 0.1 to 10 parts by weight based on 100 parts by weight of the polypropylene resin particles.

In addition to the above-mentioned inorganic compounds, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium α-olefin sulfonate may be used in combination. When an anionic surfactant is used in combination, the amount of the anionic surfactant used is 100
It is appropriate to set in the range of 0.001 to 0.5 parts by weight with respect to parts by weight.

Next, the method for producing the pre-expanded particles of the antistatic polypropylene resin of the present invention will be described in detail. The method for producing the pre-expanded particles of the antistatic polypropylene-based resin is as follows. First, a predetermined amount of a polypropylene-based resin, a hydrophilic monomer represented by the above general formula (1) and a radical polymerization initiator are mixed, and the mixture is melt-kneaded under the temperature conditions described below and molded into granules, thereby obtaining a hydrophilic polymer. To obtain polypropylene-based resin particles imparted with properties. Next, the resin particles are dispersed in an aqueous medium together with a volatile foaming agent in a closed container, and heated to a temperature not lower than a temperature at which the polypropylene-based resin particles soften to impregnate the volatile foaming agent. further,
One end of the closed container is opened, and the polypropylene-based resin particles are released into a low-pressure atmosphere outside the container to prefoam.

In the production method of the present invention, it is an important component that the polypropylene resin, the hydrophilic monomer and the radical polymerization initiator are melt-kneaded. For the melt kneading, it is preferable to use, for example, a single-screw or twin-screw extruder. The reason for using an extruder is that, after extruding the melt-kneaded product, it is cut and granulated into resin particles, so that productivity is high and economical.

By the melt-kneading, a hydrophilic monomer represented by the general formula (1) is polymerized on the polypropylene resin. Therefore, by performing granulation after melt-kneading, polypropylene-based resin particles having hydrophilicity can be obtained.
In the present invention, the temperature of the melt-kneading is 160 to 300 ° C,
Preferably it is 170-260 degreeC. If the melt-kneading temperature is lower than the above range, the radical polymerization initiator may not be completely decomposed, and the polypropylene-based resin may be insufficiently melted to make uniform reforming difficult (that is, the hydrophilicity is low). It is difficult to obtain a polypropylene resin in which the monomer is uniformly polymerized), which is not preferable. Conversely, if the temperature of the melt-kneading exceeds the above range, the decomposition reaction takes precedence and the physical properties may be deteriorated, which is not preferable.

The screw speed of the extruder is such that if the speed is too high, the degradation of the polypropylene resin due to the main chain breakage tends to increase more than the polymerization reaction. Is appropriately selected according to the conditions. In the melting process, a small amount of a nucleating agent such as talc or silica may be added. In the production method of the present invention, the particle size of the polypropylene resin particles is 0.5 to 3 mm.
Is preferably adjusted from the viewpoint of obtaining pre-expanded particles suitable for producing a foam molded article.

In the production method of the present invention, the temperature at which the polypropylene-based resin particles containing the volatile foaming agent and the aqueous medium are discharged into a low-pressure atmosphere outside the container and prefoamed (prefoaming temperature) is The temperature is set at a temperature equal to or higher than the softening temperature of the polypropylene resin particles. In particular, the temperature is preferably around the melting point (peak temperature T _{m of the} DSC curve) of the polypropylene resin before melt-kneading.

The preferable range of the pre-foaming temperature is the above-mentioned hydrophilic monomer.
Depending on the amount of body used and the type of volatile blowing agent,
Usually T_m-12 ° C to T_m+ 5 ° C, preferably T_m-1
0 ° C to T_mRange. Foaming temperature is T_mOver + 5 ° C
Then, the bubbles of the obtained pre-expanded particles become coarse and expand
Not only does the appearance of the compact deteriorate, but also the compressive strength decreases
I do. Conversely, when the foaming temperature is T_mIf it is below -12 ° C, it will be dense
The degree is 0.05g / cm ^ThreeGet pre-expanded particles that are less than
And the impact resistance of the molded foam is low.
It is not preferable because it may fall.

Next, the foam molded article of the present invention will be described in detail. The expanded molded article of the present invention is prepared by first aging the pre-expanded particles of the present invention under pressure as necessary to apply a predetermined internal pressure to the particles, and then pre-expanded particles in a mold of a molding machine. Fill. Then, the particles are fused by heating with pressurized steam to expand the particles, and the particles are cooled with water or the like and then taken out of the mold.

The density of the foamed article of the present invention is appropriately set according to the purpose of use and is not particularly limited. For example, when the article is used as a packaging material for electronic parts such as a liquid crystal display device, It is preferable to set so as to be in the range of 0.025 to 0.1 g / cm ³ .

[0037]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, a propylene-ethylene random copolymer was used as the polypropylene resin. This copolymer has an ethylene content of 4.
5% by weight, melt flow rate at 230 ° C. (MF
R) 1.1 g / 10 min, DSC curve peak temperature T _m
Was 137 ° C.

The hydrophilic monomers include polyethylene glycol monomethacrylate (of the general formula (11)
A compound in which R ¹ is hydrogen and n = 8) or methoxypolyethylene glycol monomethacrylate (the above-mentioned general formula)
Among (11), compounds wherein R ¹ is a methyl group and n = 9)
It was used. Radical polymerization initiators include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (1
A half-life temperature of 180 ° C. for one minute) or di-t-butyl peroxide (186 ° C. for one minute).

For the production of the polypropylene resin particles, a twin-screw extruder having a meshing type co-rotating twin screw was used. The extruder has an outer diameter of a screw of 37 mm,
The effective length (L / D) of the screw was 31.1. As the temperature when melt-kneading the polypropylene resin,
The temperature in the metering section of the extruder was adjusted to 210 ± 5 ° C. The screw rotation speed is 120
rpm.

Examples 1 to 5 and Comparative Examples 1 and 2 (Preparation of polypropylene resin particles) 0.1 part by weight of talc, polyethylene glycol monomethacrylate and 2,5 -Dimethyl-2,5-di (t-butylperoxy) hexane was blended in the ratio shown in Table 1 below, and was melt-kneaded by an extruder.

Next, the melt-kneaded product was extruded into strands and pelletized to obtain polypropylene resin particles having a weight per particle of 2 mg. (Production of Pre-expanded Polypropylene Resin Particles and Expanded Molded Product) 100 parts by weight of the polypropylene resin particles, 200 parts by weight of water, 1.5 parts by weight of magnesium pyrophosphate, dodecylbenzenesulfone 0.05 parts by weight of sodium acid and 20 parts by weight of butane were blended, and the temperature was raised to 135 ° C. while stirring.

After holding at 135 ° C. for 60 minutes, the valve of the nozzle at the bottom of the pressure-resistant container is opened, and the resin particles containing butane are discharged together with the dispersion into the container under atmospheric pressure. The particles were expanded to obtain pre-expanded particles. Next, the obtained pre-expanded particles are placed in a pressure vessel,
After pressure aging with compressed air of 2.5 kgf / cm ² ,
This was filled into a mold of a 400 × 300 × 50 mm molding machine using compressed air.

Further, 3.2 kgf / cm ² of steam was introduced, heated for 40 seconds, cooled for 2 minutes, and then taken out of the foamed molded product. The removed molded foam was dried at 80 ° C. for 12 hours. Table 1 shows the blending amounts (contents) of the hydrophilic monomer and the radical polymerization initiator in the above Examples and Comparative Examples.
Shown in

[0044]

[Table 1]

The properties of the foam molded article thus obtained include (a) density, (b) average cell diameter, (c) dimensional shrinkage,
(d) The surface resistivity was measured according to the following method. (a) Density The density was measured in accordance with JIS-K6767.5.1. "apparent density". (b) Average Cell Diameter A sample obtained by thinly slicing the foamed molded article was visually observed under a microscope, an average of about 50 cell diameters was obtained, and this was defined as an average cell diameter (μm).

(C) Dimensional Shrinkage Ratio The above-mentioned foamed molded product obtained by drying at 80 ° C. for 12 hours is further allowed to stand at room temperature for 24 hours to measure its size, and the shrinkage ratio to the mold size x (%). I asked. The dimensional shrinkage was evaluated according to the following criteria. ：: 0 ≦ x <3; dimensional shrinkage was low, and dimensional stability was good.

Δ: 3 ≦ x <7: Dimensional shrinkage was observed, which was insufficient for practical use. X: x ≧ 7; dimensional contraction was remarkably observed. (d) Surface resistivity The surface of the foamed molded article obtained by drying at 80 ° C. for 12 hours and then left in a constant temperature and humidity room at a temperature of 23 ° C. and a humidity of 50% for 6 hours. The resistivity (Ω) was measured.

Next, the foamed molded product is cut with a vertical cutter, and the surface resistivity of the cut surface after being left in the constant temperature and humidity chamber for one hour, and the surface of the foamed molded product is washed with water and adhered to the surface. The water content was removed, and the surface resistivity of the surface of the foamed molded body after being left in a thermo-hygrostat for 1 hour was measured. The surface resistivity was measured using a super insulation meter “SM-10E” manufactured by Toa Denpa Kogyo under the conditions of an applied voltage of 1000 V and a time of 60 seconds.

The lower the surface resistivity is, the more preferable it is. From the viewpoint of obtaining an excellent antistatic effect, it is required that the value be less than 1 × 10 ¹³ Ω. the above
Table 2 shows the results of (a) to (d).

[0050]

[Table 2]

As apparent from Table 2, polyethylene glycol monomethacrylate as a hydrophilic monomer,
2,5-dimethyl-2,5 as radical polymerization initiator
In Examples 1 to 5 in which the polypropylene resin was modified using a predetermined amount of -di (t-butylperoxy) hexane,
It can be seen that a foam molded article having excellent antistatic effects on both the surface and the cut surface can be obtained. Further, it can be seen that this antistatic effect is maintained even after washing with water.

On the other hand, in Comparative Example 1 in which the hydrophilic monomer and the radical polymerization initiator were not blended, the surface resistivity was high and charging could not be prevented. On the other hand, in Comparative Example 2 in which the amount of the hydrophilic monomer was too large, the dimensional shrinkage was large, which was not suitable for practical use. In Comparative Example 2, the measurement of the surface resistivity was impossible because the foamed molded article contracted and was greatly deformed.

Examples 6 and 7 The aforementioned methoxypolyethylene glycol monomethacrylate (n = 9) was used as a hydrophilic monomer. The above di-t-butyl peroxide was used as a radical polymerization initiator. Production of foamed molded articles and measurement of physical properties were performed in the same manner as in Examples 1 to 5, except that the blending amounts of the hydrophilic monomer and the radical polymerization initiator were set at the ratios shown in Table 3 below.

Comparative Example 3 A hydrophilic monomer and a radical polymerization initiator were not used, and an antistatic agent was used instead. That is, with respect to 100 parts by weight of the polypropylene-based resin, 0.1 part by weight of talc and 1.5 parts by weight of glycerin monostearate as an antistatic agent were used, and
In the same manner as in Example 5, the production of the foam molded article and the measurement of the physical properties were performed.

Table 3 shows the blending amounts (contents) of the hydrophilic monomer and the radical polymerization initiator in Examples 6 and 7 and Comparative Example 3, and Table 4 shows the measurement results of physical properties.

[0056]

[Table 3]

[0057]

[Table 4]

As is clear from Table 4, in Examples 6 and 7 using a predetermined amount of a hydrophilic monomer and a radical polymerization initiator, as in Examples 1 to 5, both the surface and the cut surface were excellent. The antistatic effect was obtained, and the effect was obtained continuously even after washing with water. On the other hand, in Comparative Example 3 in which a conventionally known antistatic agent was added instead of modifying the polypropylene resin, the antistatic effect after cutting or washing with water was insufficient.

[0059]

As described in detail above, according to the pre-expanded particles of the antistatic polypropylene resin of the present invention and the expanded molded article using the same, not only have excellent antistatic properties but also cracks and the like. Even when the cut surface is exposed or washed with water, the antistatic effect can be immediately exhibited, and the adhesion of dust and the like can be effectively prevented.

Accordingly, the present invention provides a container for passing mechanical parts,
It is suitably used for applications such as cushioning packaging materials for electric parts.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23/10 C08L 23/10

Claims (3)

[Claims] (1) 100 parts by weight of a polypropylene resin and a general formula (1): (Wherein R ¹ and R ² are the same or different and each represent hydrogen or a methyl group, and n represents an integer of 2 to 30), and an ester of polyethylene glycol and (meth) acrylic acid. 1 to 20 parts by weight of the resulting monomer and 0.05 to 5 parts by weight of a radical polymerization initiator are melt-kneaded and polypropylene resin particles obtained are impregnated with a volatile blowing agent and prefoamed. Pre-expanded particles of an antistatic polypropylene resin. 2. 100 parts by weight of a polypropylene resin, and 1 to 20 parts by weight of a monomer comprising an ester of polyethylene glycol and (meth) acrylic acid represented by the general formula (1) according to claim 1. , Radical polymerization initiator 0.05 to 5
Parts by weight and melt-kneaded, dispersing the resulting polypropylene resin particles in an aqueous medium together with a volatile foaming agent and a dispersion stabilizer in a closed container, and heating to a temperature above the temperature at which the polypropylene resin particles soften to volatilize. Pre-expanded antistatic polypropylene resin particles, characterized in that one end of the closed container is opened and the resin particles are released into a low-pressure atmosphere outside the container to perform pre-expansion after impregnating with a conductive foaming agent. Manufacturing method. 3. An expanded molded article obtained by subjecting the antistatic polypropylene resin pre-expanded particles according to claim 1 to foam molding.