JPH01294744A - Production of expandable polyolefin bead which forms antistatic foam - Google Patents

Abstract

PURPOSE:To obtain the title beads which can give a foam having sustained antistatic property by treating beads obtained by polymerizing an epoxy group- containing vinyl compound with polyolefin beads with ammonia or a sulfite. CONSTITUTION:1-20 pts.wt. epoxy group-containing vinyl compound (B) (e.g., glycidyl methacrylate) is polymerized with 100 pts.wt. polyolefin beads (A) of a mean particle diameter of 0.1-5.0mm at 40-120 deg.C for 0.5-10 hr in an aqueous medium in the presence of 0.01-1.5 pts.wt., per 100 pts.wt. component B, oil- soluble polymerization initiator (C) of a 10 hr half-life temperature of 40-120 deg.C (e.g., di-2-ethylhexylperoxycarbonate) and 0.001-1.0 pt.wt., per 100 pts.wt. compo nent A, dispersant (D) (e.g., methylcellulose). These beads are treated with 1-10 mol, per mol of component B, of ammonia or a sulfite (e.g., NaHSO3) at 40-120 deg.C for 0.5-10 hr and impregnated with a blowing agent (e.g., propane) at 40-130 deg.C for 1-10 hr.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing expandable polyolefin beads, and more specifically, a method for producing expandable polyolefin beads that provides a foamed molded article with excellent non-static properties. It is related to.

[Conventional technology and problems]

Polyolefin foams are used in large quantities in the packaging field and the like. Recently, its use in packaging materials for electronic material parts, such as ICs, has been considered, but in this field, static electricity can impair the functionality of electronic material parts, and static electricity can cause dust to adhere to the foam. This has become a very big problem. To solve this problem, there is a method of applying a surfactant to polyolefin foam.
The major drawback is that the surfactant easily flows off when washed with water, so that non-static properties do not last.

Furthermore, it requires a surfactant coating process and a drying process, which increases equipment costs and energy costs, so it has little industrial value.

[Means for solving problems]

In view of these circumstances, the present invention provides a method for producing expandable polyolefin beads that improves the above-mentioned drawbacks and provides a durable, non-static foamed molded product.

That is, the present invention provides a method for producing expandable polyolefin beads, which comprises polymerizing polyolefin beads with an epoxy group-containing vinyl compound in an aqueous medium, and then treating the resulting beads with ammonia or sulfite. The content shall be as follows.

Examples of the polyolefin resin used in the present invention include known olefin resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid ester copolymer. In addition, the beads in the present invention have an average particle diameter of 0.1 to 5.
0 am particles are suitable.

Examples of the epoxy group-containing vinyl compound used in the present invention include glycidyl methacrylate, glycidyl acrylate, and 2,3-epoxypropoxymethylstyrene, which may be used alone or in combination of two or more. Among these, glycidyl methacrylate is preferred from the viewpoint of cost. The amount used is 1 to 20 parts by weight per 100 parts by weight of the polyolefin beads. ! If it is less than part by weight, the antistatic property of the polyolefin foam will be low;
If the amount exceeds 20 parts by weight, the non-static property will increase, but for practical purposes, the non-static property is sufficient if the amount used is 20 parts by weight or less.
Using a larger amount is economically disadvantageous.

In the present invention, the method for polymerizing the epoxy group-containing vinyl compound is not particularly limited and any known method may be used, but from an economical standpoint, a thermal suspension polymerization method using an oil-soluble polymerization initiator and a dispersant is preferred. .

The oil-soluble polymerization initiator used in the present invention preferably has a 10-hour half-life temperature of 40 to 120°C, such as di-2-ethylhexylhexyl oxydicarbonate, benzoyl peroxide, Japanese Patent Application No. 60-25927, Known materials disclosed in Japanese Patent Publication No. 56-22447 and the like can be used alone or in combination of two or more. The amount used is 0.01 parts by weight per 100 parts by weight of the epoxy group-containing vinyl compound.
The amount is preferably 1.5 parts by weight, and the oil-soluble polymerization initiator used in the present invention is preferably used after being dissolved in the epoxy group-containing vinyl compound in advance.

Dispersants used in the present invention include known ones such as partially saponified polyvinyl acetate, methylcellulose, tricalcium phosphate, and sodium dodecylbenzenesulfonate. Kosho 56
-22447, the dispersant used alone or in combination is used in an amount of 10% of polyolefin beads.
0.001 to 1.0 parts by weight is suitable for 0 parts by weight.

Further, the weight ratio of aqueous medium/polyolefin beads during polymerization is suitably 0.5/1 to 2/1.

In the present invention, the polymerization temperature is suitably 40 to 120°C, and the polymerization time is suitably 0.5 to 10 hours. These conditions are:
It is appropriately determined depending on the type and amount of the oil-soluble polymerization initiator used and the type and amount of the epoxy group-containing vinyl compound used.

The ammonia treatment in the present invention involves charging ammonia gas or aqueous ammonia to the polymerization system in the reaction vessel,
This is done by performing heat treatment.

The appropriate amount of ammonia to be used is 1 to 10 times the molar amount of the epoxy group-containing vinyl compound used. If the amount is less than 1 times the molar amount, the effect of its use will be small, and if it exceeds 10 times the molar amount, no further effect will be observed, which is economically disadvantageous. The heat treatment temperature was 40 to 120°C, and the heat treatment time was 0.
5 to 10 hours is appropriate.

The sulfite treatment in the present invention is performed by charging sulfite instead of the ammonia gas or ammonia water and performing heat treatment. The amount of sulfite used is 1 to 10 times the molar amount of the epoxy group-containing vinyl compound used. If the amount is less than 1 times the molar amount, the effect of using it will be small, and if it exceeds 10 times the molar amount, no further effect will be observed, which is economically disadvantageous. In addition, the heat treatment temperature is 40-120℃,
A suitable heat treatment time is 0.5 to 10 hours. Examples of the sulfite include sulfites such as sodium and potassium, and these may be used alone or in combination.

Impregnation with a foaming agent that imparts foamability to beads may be carried out at the stage of raw polyolefin beads, after polymerization of the epoxy group-containing vinyl compound, or after treatment with ammonia or sulfite. Good zero blowing agents include the known blowing agents used in conventional polyolefin beads, such as propane, butane, pentane, freon, nitrogen, air, and the like. Impregnation conditions are 40-13
The appropriate time is 1 to 10 hours at 0°C, and the appropriate amount of impregnation is 1 to 10% by weight based on the expandable polyolefin beads after impregnation.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but these are not intended to limit the present invention in any way.

In addition, the non-static evaluation of the foamed molded article was performed by the following method.

Evaluation of non-static properties: After drying the foamed molded product, it was left standing in a constant temperature room at a temperature of 23°C and a relative humidity of 50% for one week, and then tested using a static honest meter (TYPE S-5109, manufactured by Shishido Seidenki). The non-static properties were evaluated by measuring the half-life time of the voltage.The measurement conditions were: applied voltage 10V, application time 60V.
seconds, temperature 23° C., and relative humidity 50%. The shorter the half-life time, the better the non-static property.

In addition, in order to evaluate the sustainability of the non-static property, the foamed molded product was washed with running water at 15°C for 3 minutes, and after drying, it was kept in the constant temperature room for one week. After ffi, the half-life time of the charging voltage was measured by the same method as above.

Examples 1 to 8, Comparative Examples 1 to 4 5 kg of aqueous medium was placed in a polymerization vessel with an internal volume of 101 equipped with a stirrer.
, 3 kg of cross-linked polyethylene beads with an average particle size of 1.2 (cross-linked polyethylene beads with a melt index of 2, and 50% by weight of insoluble bone in the solvent xylene), di-2-ethylhexyl peroxy 0.3 parts by weight of dicarbonate (based on 100 parts by weight of glycidyl methacrylate), the specified amount of glycidyl methacrylate shown in Table 1, and partially saponified polyvinyl acetate (Gosenol GH-20 manufactured by Nippon Gohsei Chemical Co., Ltd.) Ig were prepared and heated at 55°C. Polymerization was carried out for 6 hours. Thereafter, ammonia or sodium hydrogen sulfite in a predetermined molar amount shown in Table 1 of glycidyl methacrylate was charged, followed by heat treatment at 70°C for 3 hours.Next, 210g of liquefied butane was charged and impregnated with a blowing agent at 120°C for 4 hours.

After the obtained beads are cooled, dehydrated, and dried, they are pre-foamed by contacting them with steam at 120°C for 30 seconds, and the obtained pre-foamed particles are immediately heated to an inner volume of 10wXIQcmX2c+.
The mixture was filled into a mold of No. m, and heated for 30 seconds in cool water at 120° C. to obtain a foamed molded product. After drying this foamed molded article, the antistatic property was evaluated. The results are shown in Table 1.

From Table 1, it can be seen that even if glycidyl methacrylate is polymerized, there is no effect without ammonia treatment, and even if ammonia treatment or sodium sulfite treatment is performed without using glycidyl methacrylate, there is no effect, and the non-static property is low. . On the other hand, it can be seen that the material according to the present invention has high non-static properties and maintains high non-static properties even after washing with water.

Comparative Examples 5 to 7 3 kg of crosslinked polyethylene beads with an average particle diameter of 1.2 m used in Example 1, 5 kir of aqueous medium, 21 liters of liquefied butane
0 g was charged into the polymerization vessel and impregnated with butane at 120°C for 4 hours.

The obtained beads were pre-foamed in the same manner as in the previous example, and then a foamed molded article was obtained.

Oleic acid monoglyceride, a surfactant, was applied to the surface of this foam molding at a concentration of 0.05 mg/ci.
, product name: Excel 300), or sorbitan monolaurate [Masei ■, product name: Rheodol Super 5P-
LIO) was applied and the non-static property was evaluated. The results are shown in Table 2.

Table 2 *A Nioleic acid monoglyceride B: Sorbitan monolaurate From Table 2, it is seen that the foamed molded articles whose surfaces are coated with these surfactants lose their non-static properties when washed with water.

[Action/Effect]

The expandable polyolefin beads according to the present invention can be easily produced, and the foamed molded products obtained using the beads have a long-lasting non-static property, and are particularly suitable for use in the field of packaging electronic parts etc. can be done.

Patent applicant Kanebuchi Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. Production of expandable polyolefin beads characterized by polymerizing polyolefin beads with an epoxy group-containing vinyl compound in an aqueous medium and then treating the resulting beads with ammonia or sulfite. Law. 2. The manufacturing method according to claim 1, wherein the epoxy group-containing vinyl compound is glycidyl methacrylate.