JPS5911340A - Production of fluororesin foam - Google Patents

Abstract

PURPOSE:To improve expandability and the mechanical properties of a foam, by using boron nitride having a surface area within a specified range as an expanding aid in the production of a fluororesin foam using Freon gas as a blowing agent. CONSTITUTION:Freon gas such as Freon 12 or Freon 22 as a blowing agent and 0.5-2wt% boron nitride having a surface area of 5-10m<2>/g as measured by the Brunauer-Emmett-Teller method as an expanding aid are added to a hot-melt extrudable fluororesin. The mixture is hot-melt-extruded to obtain the desired fluororesin foam. The resultant foam has a high extent of foaming and a small, uniform average cell size and is excellent in mechanical characteristics, insulation characteristics, etc. Examples of the melt-extrudable fluororesins are tetrafluoroethylene/hexafluoropropylene copolymer and vinyl fluoride resins.

Description

[Detailed Description of the Invention] Fluororesin has a wide range of uses as a material with excellent flame retardancy, heat resistance, and low smoke properties. Conventionally, electric wires with a solid insulation layer have been made by taking advantage of these characteristics. For hot-melt extrudable fluororesins, foaming during extrusion can improve the electrical insulation properties and reduce costs. The foaming method uses a gas, a liquid, a chemical foaming agent, etc. as a foaming agent, but the most common method is to use carbonized carbon (for example, freon [F] gas), which is a gaseous gas. As Freon gas, Freon-11,
There are 7 Leon-12, Freon-13, Freon-14, Freon-22, Freon-23, etc., but Freon-
12 and -22 are the most commonly used.

Even in this foaming method using Freon gas as a foaming agent, it is desirable to use a foaming aid that is generally used for foaming polyethylene resin. However, in the case of fluororesin, S i02,
Substances such as ZrO2, TiO2, and Aj1203 cannot be used because they react with these substances to produce reaction products. Therefore, boron nitride (hereinafter referred to as BN) was adopted as a chemically stable substance. Boron nitride has excellent electrical properties and also has excellent lubricity, so it has a cleaning effect in the die during extrusion, so it can improve extrusion properties (sustain stability).

In the present invention, in order to enhance the effect of BN as a foaming aid, various types of BN were investigated, and as a result, it was discovered that the foamability can be improved by adding an appropriate amount of N as follows. That is, the type of BN used is BN that has a BET surface area of 5 to 10 m2/g measured by the Brunauer-Emmett-Taylor method (BET method), and the amount added is based on the fluororesin finally obtained. The fluororesin composition is in a range of 0.05 to 2% by weight based on the fluororesin composition of the foam. The cell diameter of the foam obtained using the fluororesin composition of the present invention is fine and uniform, and the mechanical properties of the foam are
It also has excellent insulation properties. Examples of fluororesins that can be hot melt extruded include tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl hinyl ether copolymer, ethylene-chlorotrifluoroethylene copolymer, and ethylene-tetrafluoroethylene. These include copolymers, vinylidene butylene resins, chlorotrifluoroethylene resins, and vinylidene butylene resins.

This will be explained below with reference to examples. Table 1 compares the foaming properties when various levels of BET surface area were added to FEP resin (fluoroethylene propylene TEFLON FEP 100).

In this case, Freon-22 gas is used as the blowing agent, and the amount of impregnation is 0.3 bar tens by weight.

Table 1 (1st row/lower row: upper row foaming degree, lower row average cell diameter) From these results, the BET surface area is 5 to 10 m2/
g is the most effective (high degree of foaming, small average cell diameter), and the appropriate amount to add is 0.5 to 2% by weight; adding more than that will not be effective and will reduce the cost. This will only lead to an increase in

Claims (1)

[Claims] (1) In the production of fluororesin foam using Freon gas as a blowing agent, Brunauer gas is used as a blowing aid.
Surface area measured by Emmett-Taylor method is 5-10m2
A method for producing a fluororesin foam, characterized by adding 0.5 to 2 weight percent of boron nitride/g.