JPH0457842A - Flame-retardant resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. having excellent flame-retardant properties and mechanical characteristics and generating a small amt. of smoke during burning by compounding a polyolefin resin with a flame retardant component contg. an inorg. flame retardant and a specified amt. of an active zinc oxide. CONSTITUTION:In preparing a flame-retardant resin compsn. by compounding a polyolefin resin (e.g. PE) with an inorg. flame retardant [e.g. Al(OH)3], an active zinc oxide is added in an amt. of 5-35 wt.% (based on the retardant) to the retardant.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a flame-retardant resin composition, and more specifically, it has excellent mechanical properties and low smoke generation when burned, so it can be used as the outer sheath of electric wires and cables. The present invention relates to a flame-retardant resin composition that is effective when used as an insulator.

(Prior Art) Thermoplastic resins such as polyolefin resins, which have excellent extrusion processability and electrical insulation properties, have been used for the jackets and insulators of electric wires and cables. In recent years, there has been an increasing demand for these materials to be flame retardant.

As a flame retardant method, a method is usually adopted in which a compound containing a halogen such as chlorine or bromine is mixed with these thermoplastic resins.

By the way, materials for insulating and sheathing electric wires and cables for vehicles and nuclear power plants, for example, comply with UL standard 75.
A high degree of flame retardancy is required, passing the VW-1 flammability test of 8, the vertical flammability test of ICEA 561-402, and the vertical tray flammability test of IEEE std, 383. Moreover, regarding the tensile properties, the JIS standard for polyethylene is that the tensile strength is 1.0 kg/+nm2 or more, and the elongation is 350%.
In addition to the above requirements, the amount of hydrochloric acid gas generated is also standardized, and in particular, in cables for nuclear power plants, the amount of halogen gas generated during combustion is required to be less than 100 μ/g.

Resin compositions containing the above-mentioned halogen-containing compounds exhibit good flame retardancy and mechanical properties, but
When burned, it generates a large amount of black smoke and gases that are toxic to the human body or corrosive to metals.

In order to avoid such problems, hydrated metal oxides such as aluminum hydroxide and magnesium hydroxide, which have extremely low smoke generation, toxicity and metal corrosive properties, and various carbonates are used as flame retardants. A method of mixing it with a plastic resin is known.

(Problem to be solved by the invention) However, for example, the vw-
In order to pass the 1m flame test, it is necessary to blend a large amount of the above-mentioned inorganic flame retardant into the thermoplastic resin, but by blending a large amount of these inorganic substances, the mechanical properties of the resulting resin composition are improved. Moreover, since these inorganic substances themselves are hygroscopic, there is a problem that the electrical properties of the composition are reduced. Furthermore, although phosphorus-based compounds, which are often added to these resin compositions to improve flame retardancy, do have the effect of improving flame retardancy, they have the problem of easily emitting smoke when burned. .

The present invention solves the above-mentioned problems and provides a novel flame retardant material that has a high degree of flame retardancy that passes the VW-1 combustion test, maintains high mechanical strength characteristics, and emits less smoke when burned. The purpose of the present invention is to provide a synthetic resin composition.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a flame retardant resin composition comprising a polyolefin resin and an inorganic flame retardant. 5 to 3
A flame-retardant resin composition is provided, characterized in that it contains 5% by weight of activated zinc white.

Here, the polyolefin resin is not particularly limited, but includes, for example, high, medium, low, and ultra-low density polyethylene, ethylene-vinyl acetate copolymer, ethylene ethyl acrylate copolymer, and other polyethylene and polar Known resins such as copolymers with group-containing monomers may be used alone or in mixtures thereof. Among these,
Ethylene-vinyl acetate copolymer is preferred from the viewpoint of flame retardancy, and ethylene ethyl acrylate copolymer is preferred from the viewpoint of smoke-emitting property.

Inorganic flame retardants in the present invention are not particularly limited, but include hydrated metal oxides such as magnesium hydroxide and aluminum hydroxide; carbonates such as calcium carbonate, basic magnesium carbonate, dolomite, and huntite; Other commonly used substances include halates and red phosphorus. For flame retardancy, magnesium hydroxide is particularly preferably used here.

The blending ratio of these flame retardants is 1 part polyolefin resin
It is preferable to set the content to 30 to 300 parts by weight relative to 00 parts by weight. If the blending ratio of the flame retardant is less than 30 parts by weight, the flame retardancy of the resulting resin composition will not be sufficiently improved, and if it exceeds 300 parts by weight, the properties will be significantly degraded. A more preferable blending amount of the flame retardant is 50 to 200 parts by weight per 100 parts by weight of the thermoplastic resin.

The present invention is characterized in that 5 to 35% by weight of the above flame retardant is activated zinc white. This activated zinc white is produced by reacting zinc chloride and sodium carbonate in a solution and firing the resulting zinc carbonate to form zinc oxide. In contrast, ordinary zinc oxide is obtained by oxidizing metallic zinc or zinc ore.

This activated zinc white has a finer particle size than zinc white produced by a normal dry method, and therefore has higher activity. As such active zinc white, for example, Z manufactured by Sakai Chemical Industry ■
One example is IMCI-20.

By blending this active zinc white, the flame retardance and smoke emitting properties of the resulting resin composition are significantly improved. In particular, in a combustion test using an electric wire, the effect of shortening the afterflame after the combustion source flame was removed was found.

The reason for this is not yet clear, but it is thought that the active zinc white acts at some point in the reaction process during combustion to make it possible to extinguish the flame.

Note that the above-mentioned effects were not exhibited by ordinary zinc white, but only by active zinc white.

The blending ratio of this active zinc white is set at 5 to 35% by weight of the total inorganic flame retardant blended into the polyolefin resin. When the blending ratio is less than 5 parts by weight, the effect of improving the flame retardancy of the resulting resin composition is not recognized, and even when it exceeds 35 wt%, the effect reaches saturation and the flame retardance is reduced instead. It's for a reason.

The preferred blending ratio is 10 to 30% by weight of the inorganic flame retardant.
It is.

The flame-retardant resin composition of the present invention is prepared, for example, by mixing the above-mentioned components in a Banbury mixer or the like. When preparing the resin composition of the present invention, if necessary, other thermoplastic resins, other flame retardants, synthetic rubber, natural rubber, or organic/inorganic fillers, antioxidants, lubricants, and various organic/inorganic additives may be added. Pigments, UV inhibitors, thermo-light stabilizers, radiation protection agents, dispersants, copper damage inhibitors, neutralizing agents, foaming agents, plasticizers, antifoaming agents, crosslinking agents, extenders, flow improvers, weld strength Additives such as improvers and nucleating agents may also be added within the range that does not significantly impair the effects of the present invention.

(Example) Examples 1 to 4. Comparative Examples 1 to 4 Each component shown in Table 1 was sufficiently kneaded at 150° C. using an 8-inch twin-screw roll, and then a sheet of a predetermined thickness was formed using a pressure press to prepare a sample.

Further, each of these sheets was pelletized and extruded and coated onto an annealed copper stranded wire conductor having a cross-sectional area of 2rnrn2 using a 30mmφ extruder so that the outer diameter was 3.4mm to produce an electric wire.

Necessary characteristics of each sample thus prepared were measured based on the specifications below.

Tensile properties: A sample sheet with a thickness of 1+nm was left in a constant temperature room at 20°C for one day, then punched out using a JIS No.
Tensile strength (kg/mm) and elongation rate (%) were measured at a speed of mm/min.

Oxygen index: 3m+++ thick sample sheet with a width of 6.5m,
It was punched out to a length of 150 mm and measured in accordance with the oxygen index test method specified in JISk 720I.

VW-1 combustion test: Electric wire samples were tested for 15 seconds x 5 in accordance with the VW-1 vertical combustion test specified in UL standard 758.
It was determined that the test piece passed if the damage to the indicator group was within 25% after 3 times of flame contact, the absorbent cotton did not catch fire, and the afterflame time after each flame contact was within 60 seconds.

Smoke generation: 76 mm vertically from a sample sheet with a thickness of 0.5 mff+
I made a specimen with a width of 76+nm and passed ASTM E-6.
The smoke amount (D m) was measured by the non-flaming method using an NBS smoke chamber in accordance with 62.

The above results are summarized in Table 1.

(Blank below) (Effects of the Invention) As is clear from the above explanation, the flame-retardant resin composition of the present invention has a high degree of flame retardancy that passes the VW-1 combustion test, and It has excellent properties and smoke-emitting properties, and its industrial value is extremely high as an outer covering and insulator for electric wires and cables.

Claims (1)

[Claims] In a flame retardant resin composition formed by blending an inorganic flame retardant with a polyolefin resin, the inorganic flame retardant has a content of 5 to 50%.
A flame-retardant resin composition containing 35% by weight of activated zinc white.