JPH01149840A - Production of foamed resin article - Google Patents

Abstract

PURPOSE:To easily obtain a foamed article having high expansion ratio and suitable as a coating of electric wire, sheet, etc., by using a foaming assistant consisting of ultrafine particle of a titanium-based substance having a specific average particle diameter. CONSTITUTION:A thermally meltable and extrudable resin (e.g., low-density polyethylene) is introduced into an extruder together with a foaming agent (e.g., chemical foaming agent such as azodicarbonamide or an inert gas such as nitrogen gas) and a foaming assistant consisting of ultrafine particle of titanium-based substance (e.g., titanium oxide) having an average particle diameter of <=0.2mum, preferably <=0.05mum. After uniformly dispersing the foaming agent and the foaming assistant in the molten resin, the mixture is extruded to obtain a formed article having an expansion ratio of >=70%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a resin foam suitable for application to electric wire coatings, sheets, hoses, tubes, and the like.

[Prior art] Resin is used in a wide range of applications because foaming not only improves various properties such as electrical properties, flexibility, and thermal insulation, but also makes it lighter and cheaper. There is.

Conventionally, resin foams have been manufactured by introducing a hot-melt extrudable resin, a blowing agent, and a blowing aid into an extruder, uniformly dispersing these, and then extruding and foaming.
Boron nitride is commonly used as a foaming aid.

[Problems to be Solved by the Invention] In recent years, increasing the degree of foaming of resin foams to 70% or more has been studied in various fields. This is extremely difficult, especially for foams with a thickness of 1 mm or less.

The present invention has been made based on the above, and 70%
The object of the present invention is to provide a method for producing a resin foam that can easily produce the above-described highly foamed product.

[Means for Solving the Problems] The method for producing a resin foam according to the present invention is characterized by using ultrafine titanium particles having an average particle size of 0.2 μm or less as a foaming aid.

In the present invention, hot melt extrudable resins include low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, ethylene-α olefin copolymer, ethylene-vinyl acetate copolymer, and combinations of ethylene and acrylic monomers. Examples include copolymers and polybutane. In addition, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FE)
P), ethylene-tetrafluoroethylene copolymer (E
TFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride (PVd
Fluorine thread resins such as F) can also be mentioned.

Examples of blowing agents include chemical blowing agents such as azodicarbonamide and 4,4'-oxybisbenzenesulfonyl hydrazide, inert gases such as nitrogen, argon, and carbon dioxide, methane,
Examples include hydrocarbons such as propane, butane, and pentane, and halogenated fluorinated hydrocarbons such as dichlorodifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, monochloropentafluoroethane, trichloromonofluoromethane, and trichlorotrifluoromethane.

The method of adding the foaming agent is to impregnate the resin with the foaming agent in advance,
It may be dissolved or a blowing agent may be injected into an extruder.

The titanium-based ultrafine particles used as a foaming aid may be those containing titanium, such as titanium oxide, -titanium oxide,
Representative examples include lead zirconate titanate, lead titanate, and lanthanic acid/zirconate/lead titanate. The crystal shape may be anatase type, rutile type, or amorphous, but
By using particles with an average particle size of 0.2 μm or less, the degree of foaming can be significantly improved. In particular, 0
．． The thickness is preferably 0.05 μm or less.

Note that the resin foam may be either crosslinked or non-crosslinked. In the case of crosslinking, a method using irradiation with ionizing radiation such as electron beams and gamma rays is preferred.

[Embodiments of the Invention] A compound consisting of the components shown on each side of Table 1 was fed from the hopper of an extruder, and monochloropentafluoroethane was injected at a pressure of 4 to 6 kg/Cm''G in the middle of the extruder. After uniformly dispersing it in the molten resin, the outer diameter is 0.3 m.
A foamed insulating coating with a thickness of 0.3 mm was formed by extrusion coating on the outer periphery of the conductor.

The extrusion conditions for the foam were as follows: using a 30 mm extruder, L/D = 25, and compression ratio -2.5. The set temperature of the cylinder is 180°C for polyethylene and 290°C for fluororesin.

Table 1 shows the results of evaluating the degree of foaming of the foamed insulation coatings of Examples and Comparative Examples. Note that the degree of foaming was determined from the following formula.

Foaming degree-(1-(ρ/ρ.)] X100 [%1(
ρ: Specific gravity of the foam, ρ. : Specific gravity of non-foamed material) As is clear from Table 1, in Examples 1 to 5, highly foamed products of 70% or more were obtained, whereas in Comparative Examples 1 to 3, only about 60% of foaming was achieved. could not.

"Effects of the Invention" As explained above, according to the present invention, a resin foam with a high foaming rate exceeding 70% can be easily realized.

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Claims (1)

[Claims] (1) In a method of manufacturing a resin foam by introducing hot-melt extrudable resin, a blowing agent, and a blowing aid into an extruder, uniformly dispersing the blowing agent and blowing aid in the molten resin, and then extruding the resin. . A method for producing a resin foam, characterized in that ultrafine titanium particles having an average particle size of 0.2 μm or less are used as the foaming aid.