JPH10147660A - Antistatic olefinic resin pre-foaming particle and foamed molded material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pre-foaming particle or a molded material capable of improving such a defect that a usual polyolefinic pre-foaming particle or its molded material does not sustain an antistatic effect or the antistatic property is extremely lowered when the foamed molded material is broken or chipped. SOLUTION: This antistatic olefinic resin pre-foaming particle is obtained by foaming an olefinic resin particle containing 1-30wt.% of a polymer or copolymer of polyethylene glycol (meth)acrylate expressed by the formula R is hydrogen or methyl group; (n) is an integer of 2-8} and 0.01-3wt.% of a surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-expanded olefin resin particle from which a foam having excellent antistatic properties can be obtained, and to a foam molded article obtained by subjecting the pre-foamed particles to foam molding by heating.

[0002]

2. Description of the Related Art Expanded molded articles of olefin-based resin pre-expanded particles are used as a passage box for machine parts such as automobile parts and a cushioning packaging material for electric products because of their excellent cushioning property, abrasion resistance and oil resistance. I have. However, since olefin resins are also excellent in electrical insulation, they are easily charged by friction, and not only impair the appearance of the foamed molded article due to adhesion of dust and the like, but also cause contamination and electrostatic breakdown due to dust collection on the contents. However, there is a problem in using it as a packaging material for electronic parts such as liquid crystal. In order to solve this problem, the antistatic agent, which is a conventional low-molecular surfactant, is applied to the surface of the pre-expanded particles for molding and the foamed molded product, or kneaded into the olefin resin to lower the surface resistivity. Let me respond.

[0003] However, in the former method, the antistatic agent on the surface is peeled off while the foamed molded article is used, and the antistatic effect is not maintained, or the antistatic agent is easily removed by washing the surface with water. The antistatic performance is significantly reduced. In addition, since there is no antistatic agent inside the foamed molded article, when the foamed molded article is cracked or chipped, the inside without antistatic property is exposed, and problems such as contamination due to dust collection occur. Remaining. On the other hand, in the latter method, the antistatic agent is present inside the resin, so that the antistatic effect is excellent in persistence, but the internal surface resistivity is insufficient immediately after the foam molded body is cut, such as cracked or chipped. so,
It takes as long as one to two weeks to obtain good antistatic properties (see JP-A-3-28239), or after the antistatic agent is removed by washing the surface with water, the antistatic agent inside the resin is removed. It takes several weeks of curing to bleed and restore antistatic properties.

[0004]

SUMMARY OF THE INVENTION The present inventors have conducted various studies to solve these problems, and as a result, modified an olefin resin with a specific hydrophilic monomer, and further modified a surfactant. By containing it, it has been found that a foam molded article having excellent antistatic properties, and also having an antistatic effect immediately obtained by cracking or washing with water can be obtained, and the present invention has been achieved. An object of the present invention is to provide pre-expanded olefin-based resin particles from which foamable keita having excellent antistatic properties can be obtained.

[0005]

That is, the present invention provides a polyethylene glycol (meth) represented by the following general formula [1].
Acrylic ester polymer or copolymer 1 to 30
The antistatic olefin resin pre-expanded particles are obtained by foaming olefin resin particles containing 0.1 to 3% by weight of a surfactant and 0.01 to 3% by weight of a surfactant. It is a foam molded article.

[0006]

Embedded image (Where R is hydrogen or a methyl group; n is an integer of 2 to 8)

The olefin resin constituting the olefin resin particles in the present invention includes low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate Copolymers, polyethylene resins such as those obtained by crosslinking these polymers, propylene homopolymer, polypropylene-ethylene copolymer, polypropylene resins such as propylene-1 butene copolymer,
Further, polyethylene-based resins, polypropylene-based resins, and the like, which are polymerized and modified with vinyl monomers such as styrene and methyl methacrylate, can be used. Among these olefin resins, a polyethylene resin modified by polymerization with styrene (hereinafter referred to as a styrene-modified polyethylene resin) is particularly preferable.

[0008] Styrene-modified polyethylene resins are described, for example, in JP-B-51-46138 and JP-B-59-034.
No. 87, JP-B-63-28443, a polymer obtained by adding a styrene-based monomer to an aqueous medium in which particles of a polyethylene-based resin are dispersed and held and polymerizing the same. can do. Here, there is no particular limitation on the ratio between the polyethylene resin and the polymer of the vinyl monomer to be produced.

The olefin resin particles of the present invention contain a polymer or copolymer of polyethylene glycol (meth) acrylate and a surfactant.
Due to the synergistic effect of the two, a foam molded article that immediately exhibits an excellent antistatic effect even when cracked or washed with water can be obtained. As a method for obtaining olefin-based resin particles containing a polymer or copolymer of polyethylene glycol (meth) acrylate, for example, an olefin-based resin in the form of particles is suspended in an aqueous medium, and the suspension is then added thereto. Polyethylene glycol (meth) acrylate Further, if necessary, a method in which a monomer copolymerizable with polyethylene glycol (meth) acrylate is added and absorbed, and polymerization is performed using a radical polymerization initiator can be mentioned.

The polyethylene glycol (meth) acrylate is represented by the general formula [Chemical Formula 1]. The number of polyethylene oxide groups is preferably n = 2 to 8, particularly n = 2 to 8.
4 is preferred. If n is 1, sufficient antistatic performance cannot be obtained, and if n is 9 or more, the molecular weight is too large to make absorption into particles difficult. Polyethylene glycol (meth) acrylate may produce a small amount of diester as a by-product during the manufacturing process. In this case, the diester acts as a cross-linking agent, and the resulting polymer or copolymer becomes a cross-linked structure. However, the present application is not particularly limited by the presence or absence of a crosslinked structure. When another hydrophilic monomer (for example, polypropylene glycol (meth) acrylate or methoxypolyethylene glycol (meth) acrylate) is used instead of polyethylene glycol (meth) acrylate, the antistatic properties Is poor, and the desired effect cannot be obtained.

On the other hand, monomers copolymerizable with polyethylene glycol (meth) acrylate include styrene, α-methylstyrene, p-methylstyrene and p-methylstyrene.
Styrene-based monomers such as t-butylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
(Meth) acrylate monomers other than polyethylene glycol (meth) acrylate such as propyl acrylate and butyl (meth) acrylate, acrylic acid,
Methacrylic acid, organic acid monomers such as maleic anhydride, maleimide monomers such as maleimide, N-phenylmaleimide, N-cyclohexylmaleimide, conjugated diene monomers such as butadiene and isoprene, and the like. it can. These monomers can be used alone or in combination of two or more kinds in a range of less than 50 mol% with respect to the total amount of polyethylene glycol (meth) acrylate.

The amount of the (meth) acrylate polymer or copolymer contained in the olefin resin particles is preferably from 1 to 30% by weight, particularly preferably from 3 to 20% by weight. If the amount is less than 1% by weight, the lapse of the antistatic effect due to washing with water cannot be avoided. If the amount exceeds 30% by weight, a foamed article having good fusion-adhesive properties is obtained when pre-expanded particles are molded. Therefore, the mechanical strength is low, which is not preferable.

The radical polymerization initiator for polymerizing polyethylene glycol (meth) acrylate is as follows:
Benzoyl peroxide, t-butyl peroxy 2-
Ethyl hexanoate, 1,1-di (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butylperoxybenzoate dicumyl peroxide,
Organic peroxides such as 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4,4 −
Azo compounds such as trimethylpentane) and 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile.

The surfactant contained in the olefin resin particles of the present invention includes nonionic surfactants such as glycerin fatty acid ester, polyethylene glycol fatty acid ester, alkyldiethanolamide and alkyldiethanolamine, and alkyl sulfonate. , An alkyl benzene sulfonate, an anionic surfactant such as an alkyl phosphate, a tetraalkyl ammonium salt,
Examples include cationic surfactants such as trialkylbenzylammonium salts, and amphoteric surfactants such as alkyl betaines and alkyl imidazolium betaines. Among these, when a cationic surfactant is used, the synergistic effect with the polyethylene glycol (meth) acrylate polymer or copolymer is particularly large, and the foamed molded product is cracked or chipped, and the surface of the foamed molded product is damaged. Washing with water is particularly preferable because an excellent antistatic effect immediately appears.

The amount of these surfactants contained in the olefin resin particles is 0.01 to 3% by weight. 0.0
If the amount is less than 1% by weight, the surface resistivity of the surface of the foamed molded product becomes insufficient, which is not preferable. Desirable surface resistivity is 1 × 10 ¹² ohm / cm or less. On the other hand, if the content exceeds 3% by weight, the pre-expanded particles and the expanded molded article are in a sticky state, which makes it easier for dust to adhere. As a method of including a surfactant in the olefin-based resin particles, the resin is melt-kneaded in an extruder, extruded into strands, and then added with a surfactant when cut into resin particles by a cutter or the like. Or a method of adding a surfactant when impregnating the resin particles with a foaming agent.

As a method for expanding the olefin resin particles in the present invention, a conventionally known method can be applied. For example, in the case of polyethylene-based resin and polypropylene-based resin, a resin obtained by granulating the resin with an extruder in an aqueous medium is suspended, heated and added with polyethylene glycol (meth) acrylate to complete the polymerization. After that, a method of impregnating a foaming agent during or after polymerization, maintaining the composition under high temperature and high pressure, and then releasing the composition under low pressure to cause foaming may be used.

On the other hand, in the case of a styrene-modified polyethylene resin, a styrene monomer is added to an aqueous medium in which particles of the polyethylene resin are dispersed and held, and then polymerized. The resulting resin particles are polymerized by adding an acid ester, and the obtained resin particles are placed in a hermetically sealed pressure-resistant container such as a V-type, C-type, or DC-type rotary mixer, flowed to introduce a blowing agent, and impregnated for several hours. The foamed resin particles are taken out and foamed by using a conventional batch-type foaming machine for foamed polystyrene. In the present invention, as the blowing agent, those generally known in the art can be used, and propane, butane, isobutane, pentane, isopentane, cyclopentane, HCFC-142 are used.
b, HFC-134a, HCFC-123, carbon dioxide,
Nitrogen gas, air and the like can be mentioned, and one or more selected from these can be used in combination.

[0018]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 8 and Comparative Examples 1 to 7 (Preparation of polyethylene resin pellets) Ethylene-vinyl acetate copolymer having a melt flow rate of 0.3 g / 10 min and a vinyl acetate content of 5.5% by weight was 100% by weight. To this part, 0.3 parts by weight of calcium silicate and 0.1 part by weight of calcium stearate were added as foam control agents, and the mixture was uniformly kneaded with an extruder and then granulated to obtain pellets of a polyethylene resin. (Preparation of Styrene-Modified Polyethylene Resin Particles) In a pressure-resistant container with a stirrer having an internal volume of 100 liters, 40 parts by weight of the polyethylene resin pellets,
20 parts by weight, magnesium pyrophosphate 0.45 parts by weight,
0.02 parts by weight of sodium dodecylbenzenesulfonate was added, and the temperature was raised to 85 ° C. while stirring.

Separately, 0.3 parts by weight of benzoyl peroxide and 0.02 parts by weight of t-butylperoxybenzoate as a radical polymerization initiator and 0.8 parts by weight of dicumyl peroxide as a cross-linking agent are added to 60 parts by weight of styrene monomer. The resulting solution was dissolved in a monomer to form a solution, and the solution was added to the aqueous medium and maintained for 4 hours while being absorbed by polyethylene resin pellet particles to carry out polymerization. Thereafter, the temperature was raised to 140 ° C. and maintained for 3 hours, followed by cooling to take out the styrene-modified polyethylene resin [A]. (Polymerization of polyethylene glycol (meth) acrylate) Inner volume 50
100 parts by weight of the styrene-modified polyethylene resin [A], 100 parts by weight of water, 0.45 parts by weight of magnesium pyrophosphate, and 0.02 parts by weight of sodium dodecylbenzenesulfonate were added to a liter pressure-resistant container with a stirrer, The temperature was raised to 80 ° C. while stirring. Next, polyethylene glycol methacrylate having a different number of polyethylene oxide groups was added so that 0.05 parts by weight of dicumyl peroxide and the content of the polymer were as shown in Table 1, and then the temperature was raised to 140 ° C. and maintained for 2 hours. To take out resin particles [B].

[0020]

[Table 1]

(Impregnation of foaming agent and foam molding) Internal volume 5
100 parts by weight of the above resin particles [B] (Example) or styrene-modified polyethylene resin [A] (Comparative Example), 1.0 part by weight of ethylbenzene, and The surfactant shown in No. 1 was added so that the content was as shown in Table 1, and 14 parts by weight of butane was press-fitted while sealing and stirring. Then, after maintaining the inside of the vessel at 70 ° C. for 4 hours, the resin was cooled and foamable resin particles were taken out. The taken out expandable resin particles were immediately pre-expanded by a batch-type foaming machine to a volume multiple of 20 times, and then stored at room temperature for 24 hours. And, the pre-expanded particles are 400 × 300
The mold was filled in a mold of a × 100 mm molding machine, and steam at a gauge pressure of 0.8 kg / cm ² was injected for 60 seconds and heated. Then, after cooling for 5 minutes, the foam molded article was taken out. (Measurement of surface resistivity) After the obtained foamed molded product was dried at 50 ° C for 12 hours, it was left in a constant temperature and humidity room at a temperature of 23 ° C and a humidity of 50%, and the surface resistivity of the foamed molded product surface (a) was measured. Was measured. Further, when the foamed molded article is cut by a vertical cutter and left for 1 hour in a constant temperature and humidity chamber (b),
Further, the surface of the foamed molded article was washed with water, and after removing moisture adhering to the surface, the surface specific resistance in the case (c) of being left in a thermo-hygrostat for 1 hour was measured. Table 2 summarizes these measured values. The surface resistivity was measured using a super insulation meter SM-10E manufactured by Toa Denpa Kogyo with an applied voltage of 100
The measurement was performed at 0 V for 60 seconds.

[0022]

[Table 2]

From the comparison between Examples 2 and 3 and Comparative Examples 1 and 2, it was found that the styrene-modified polyethylene resin [A] containing no polymer of polyethylene glycol methacrylate alone had a cut 1 It can be seen that the antistatic property after the aging was poor, and that it had no antistatic property after washing with water. Also, from the comparison between Example 1 and Comparative Example 3, even if a polymer of polyethylene glycol methacrylate was contained, only a material having poor antistatic properties after cutting and washing with water was obtained unless a surfactant was contained. It turns out there is no.

Examples 9 to 11 and Comparative Example 8 (Preparation of polypropylene resin pellets) Propylene-ethylene random copolymer 100 having a melt flow rate of 7.5 g / 10 minutes and an ethylene content of 3.5% by weight
0.1 parts by weight of talc and 10 parts by weight of a surfactant shown in Table 3 were added to the parts by weight, and the mixture was uniformly kneaded with an extruder and granulated. C]. Further, in the same manner except that the surfactant was not added, pellets of the polypropylene resin [D]
I got

[0025]

[Table 3]

(Polymerization and foaming of polyethylene glycol (meth) acrylate) 100 parts by weight of the polypropylene resin pellets [C] or [D] and 100 parts by weight of water in a pressure-resistant container having an inner volume of 50 liters and equipped with a stirrer. And 0.2 parts by weight of polyvinyl alcohol, and the mixture was heated to 80 ° C. while stirring. Next, 0.05 parts by weight of dicumyl peroxide and the content of the polymer are shown in Table 3.
After adding polyethylene glycol methacrylate having 3 polyethylene oxide groups so that
The temperature was raised to 5 ° C. and maintained for 2 hours to carry out polymerization. Subsequently, 20 parts by weight of butane was gradually supplied into the pressure-resistant container and kept at the same temperature for 30 minutes. After that, the valve of the nozzle at the bottom of the pressure-resistant container was opened, and the butane-containing resin particles were discharged together with the dispersion into the container under atmospheric pressure to obtain pre-expanded particles 25 times in bulk. The obtained pre-expanded particles are placed in a pressure vessel, aged under a pressure of 2.5 kg / cm ^{2 under} compressed air, and then aged in a 400 × 300 × 50 mm molding machine using compressed air. Filled. And a gauge pressure of 3.
2 kg / cm ² of steam was introduced, heated for 40 seconds, and then cooled for 2 minutes, and then the foamed molded product was taken out. (Measurement of Surface Specific Resistance) The obtained foamed molded product was cured and dried at 60 ° C. for 24 hours, and then the surface specific resistance was measured in the same manner as in Example 1. Table 4 summarizes the measurement results.

[0027]

[Table 4]

Comparative Examples 9 and 10 The surface resistivity was measured in the same manner as in Examples 9 and 10 except that polyethylene glycol methacrylate was not added. Table 4 shows the results. From the comparison of Examples 9, 10, and 11 with Comparative Example 8, the antistatic property after cutting and washing with water was not observed in the polypropylene resin pellet [D] containing no surfactant and containing only a polymer of polyethylene glycol methacrylate. It can be seen that only inferior properties can be obtained. On the other hand, Example 9
From the comparison of Comparative Example 9 with Comparative Examples 9 and 10, when the polymer did not contain the polyethylene glycol methacrylate polymer and contained only the surfactant, the antistatic property was inferior after cutting and was completely charged after washing with water. It turns out that it does not have prevention property. One month after cutting or washing, the surface resistivity did not decrease, and the antistatic property did not recover.

[0029]

According to the present invention, 1 to 30% by weight of a polyethylene glycol (meth) acrylate polymer or copolymer represented by the general formula [Chemical Formula 1] of the present invention and a surfactant 0.0
An antistatic olefin resin pre-expanded particle obtained by expanding an olefin resin particle containing 1 to 3% by weight contains a polymer or copolymer of polyethylene glycol (meth) acrylate, a surfactant, The use of a combination of them can exert an excellent antistatic property due to the synergistic effect. In particular, when the olefin-based resin particles are styrene-modified polyethylene-based resin particles, and when the surfactant is a cationic surfactant, a remarkable antistatic effect can be exhibited. Therefore, a molded article foam-formed using the antistatic olefin resin pre-expanded particles of the present invention is cracked, and even when washed with water, an excellent antistatic effect can be immediately exhibited. Can protect the contents from contamination by dust collection and electrostatic destruction, and can be suitably used as a packaging buffer for electronic components.

Claims (4)

[Claims] 1 to 30% by weight of a polymer or copolymer of polyethylene glycol (meth) acrylate represented by the following general formula [Chem. 1] and 0.01 to 10% by weight of a surfactant.
Pre-expanded antistatic olefin resin particles obtained by expanding olefin resin particles containing 3% by weight. Embedded image (Where R is hydrogen or a methyl group; n is an integer of 2 to 8) 2. The antistatic olefin resin pre-expanded particles according to claim 1, wherein the olefin resin particles are styrene-modified polyethylene resin particles. 3. The pre-expanded antistatic olefin resin particles according to claim 1, wherein the surfactant is a cationic surfactant. 4. A foam molded article obtained by subjecting the pre-expanded antistatic olefin resin particles of claim 1 to foam molding by heating.