JPH0222317A - Modification of open cell foam of polyolefin - Google Patents

Abstract

PURPOSE:To obtain the title foam having eternal fire-resistance, suitable as materials in aeroplanes, floor covering materials, cushioning materials of wall material, absorbing materials, etc., by impregnating polyolefin open cell foam with a vinyl phosphonate compound, then irradiating the foam with electron rays and polymerizing. CONSTITUTION:(A) polyethylene, ethylene-vinyl acetate copolymer, etc., is expanded to give a polyolefin open cell foam. On the other hand, (B) a vinyl phosphate compound [e.g., compound shown by the formula (x and y are >=1)] is dissolved in a solvent such as acetone, impregnated into the component A and the solvent is evaporated. Then the foam is irradiated with electron rays having1-10Mrad at 1.0-1.0X10<7>rad/second dose rate preferably at 10-50 deg.C to give the aimed foam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for modifying open-cell polyolefin foam. More particularly, the present invention relates to a method of permanently imparting flame retardancy to polyolefin open cell foams.

[Prior Art] In recent years, polyolefin open cell foams have been made inexpensive and have excellent physical properties such as cushioning properties and sound absorption properties, and are widely used in various applications such as cushioning materials, backing materials, filters, coating materials, and sound absorption materials.

However, polyolefin resins such as polyethylene and polypropylene are extremely flammable and have a high heat of combustion, so polyolefin open cell foams have not been able to be used in applications such as flooring materials, wall materials, and materials in aircraft interiors.

Conventional methods for producing flame-retardant foams include heating and foaming a polyolefin resin with an inorganic filler added (see Japanese Patent Publication No. 60-26500), or using phosphorus-based or halogen-based foams. A method of heating and foaming a material to which a flame retardant such as
587, Japanese Patent Publication No. 48-29857, Japanese Patent Publication No. 5g-5930).

[Problems to be Solved by the Invention] However, the former method of adding an inorganic filler or flame retardant relates to closed cell bodies, and is difficult to apply to open cell bodies.

This is because open-cell foams require strict foaming conditions, and if a large number of inorganic fillers or flame retardants are added, satisfactory foams cannot be obtained.

An object of the present invention is to provide a novel modification method that solves the above-mentioned problems and imparts flame retardancy to open-cell polyolefin cells.

[Means for Solving the Problems] The method for modifying open-cell polyolefin foam of the present invention involves impregnating the open-cell polyolefin foam with a vinylphosphonate compound, and then irradiating the polyolefin open-cell foam with an electron beam to transform the inside and surface of the foam. It is characterized by producing a polymer that is insoluble in.

Examples of the material for the open-cell polyolefin foam to be used in the present invention include polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polytetrafluoroethylene, ethylene-propylene copolymer, poly-4-methyl-
Examples include 1-pentene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, and tetrafluoroethylene/ethylene copolymer.
Ethylene-vinyl acetate copolymer is particularly preferred in terms of physical properties such as recovery properties and cushioning properties.

The open cell ratio of the polyolefin open cell material is preferably 80% or more, particularly preferably 90% or more.

When the open cell ratio is 80% or less, it is difficult to impregnate the vinyl phosphonate compound.

The vinyl phosphonate compound to be impregnated next is preferably a compound represented by the general formula (wherein, X and y>1). In the compound of the above formula, P is a flame retardant element and is contained in an amount of about 22.5% by weight.

In the present invention, the method for impregnating a polyolefin open cell with a vinyl phosphonate compound is to first add the vinyl phosphonate compound to a solvent described below at a concentration of 10 to 100 volume %, preferably 25 to 75 volume %. Let it dissolve. In this case, if it is less than 25%, a self-extinguishing foam cannot be obtained, and if it exceeds 75%, the viscosity of the solution is high and impregnation efficiency is poor.

The polyolefin open cell foam is then impregnated with the solution.

Next, the foam impregnated with the solution is taken out, excess solution is squeezed out, and the foam is sufficiently air-dried or dried under reduced pressure to evaporate the solvent. The impregnation rate can be adjusted by the concentration of the solution and the squeezing method after impregnation.

Examples of the solvent used here include acetone, ethanol, methyl ethyl ketone, ethyl acetate, benzene, and tetrahydrofuran.

After drying, the foam is irradiated with ionizing radiation under an inert gas atmosphere or under vacuum. Co as ionizing radiation
80 gamma rays and electron beams from an accelerator are conveniently used. For example, the foam preferably has a temperature of 1.0 at 10 to 50°C.
~1. 1-10 Mra at a dose rate of Ox107 rad/sec
The irradiation with a dose of d produces an insoluble polymer inside and on the surface of the foam. As a result, durable flame retardance can be achieved.

[Example] Next, the present invention will be explained based on examples.

Example 1 Open-cell foam made of ethylene-vinyl acetate copolymer [manufactured by Sanwa Kako Co., Ltd., Opcel LC-300 #3 cell diameter 2+]
am, open cell rate 100%, apparent density 0.027g/
cJ], a 200 x 100 x 5 mm sheet was impregnated with a 25% methanol solution of a vinyl phosphonate compound (Fyrol 76, manufactured by Stauffer Chemical, USA), and then the methanol was removed by air drying. The thoroughly dried foam was placed in a polyethylene bag, nitrogen was passed through it for 10 minutes, and the bag was sealed. This was placed on a conveyor, and a 1.5 MeV, 50
tlA.

9.2 XLO 5 Mrad of electron beam was irradiated at 4 rad/sec.

After irradiation, the foam was washed with water and then immersed in warm water at 50°C to remove unreacted substances and water-soluble polymers. After drying, the weight gain of the foam was 51.6% based on the weight of the cool foam. UL for treated foam
As a result of the combustion test of 94HF-1, drip
) and met all my requirements.

Example 2 The treatment was carried out in exactly the same manner as in Example 1 under the same conditions as in Example 1 except that the concentration of the methanol solution of the vinylphosphonate compound in Example 1 was changed to 50% by volume. The weight increase rate of the foam after treatment was 65.3%, and U L
It was compatible with 94HF~1.

Implementation f! I 3 The size of the open cell in Example 1 was set to 200 x 100
The treatment was carried out in exactly the same manner as in Example 1, except that the methanol solution of the vinylphosphonate compound was changed in concentration to 75% by volume. The weight increase rate of the foam after treatment was 97.3%, and as a result of the combustion test, there was no drip and the U of the vertical test was 97.3%.
It was compatible with L 94V O.

[Effects of the Invention] As is clear from the following explanation, flame retardancy can be imparted to polyolefin open-cell foams by applying the method of the present invention. Therefore, the polyolefin open-cell foam modified by the method of the present invention is useful as a material for cushioning materials, adsorbents, air filters, etc. in the fields of aircraft interior materials, flooring materials, wall materials, etc.

Claims (1)

[Claims] 1. Modification of open-cell polyolefin foam, which is characterized by impregnating the open-cell polyolefin foam with a vinylphosphonate compound and then irradiating it with an electron beam to produce an insoluble polymer inside and on the surface of the foam. Method.