JPS5971346A - Flame-retardant, low-smoking polyolefin resin composition - Google Patents

Abstract

PURPOSE:To provide the titled composition having low smoking tendency and free from emission of corrosive gas, and suitable for the wiring in a building, by compounding a polyolefin resin with a filler composed of a hydrated metallic oxide and zinc borate at a specific ratio. CONSTITUTION:The objective composition is prepared by compounding 100pts.wt. of a polyolefin resin with >=50pts.wt. of a filler composed of a hydrated metallic oxide (e.g. aluminum hydroxide) and zinc borate. The weight ratio of the hydrated metallic oxide in the filler is 0.25-0.75. The maximum amount of the filler added to the polyolefin resin is about 300pts.wt. when the resin is amorphous ethylene/alpha-olefin copolymer and about 150pts.wt. when it is crystalline polyethylene.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame-retardant, low-smoke polyolefin resin composition that is flame-retardant, generates little smoke, and does not generate corrosive gases.

[Background of the invention]

In recent years, the requirements for flame retardancy for building wiring and equipment internal wiring have become increasingly strict.It goes without saying that it is flame retardant, but also has low smoke generation, and is free from harmful gases that have a negative impact on the human body and equipment. It is expected that this will not occur.

To meet these requirements, resins containing halogen in their molecular structure, such as polyvinyl chloride resin, cannot be used because they generate corrosive and harmful gases when burned. In addition, for resins that do not contain halogens such as polyolefin resins, flame retardants made of halogen compounds are generally added to make them flame retardant.
In this case, halogen gas is also generated during combustion. Therefore, a method of imparting flame retardance by adding so-called hydrated metal oxides that do not use halogens has become effective, and it is well known that aluminum hydroxide, magnesium hydroxide, etc. are used as water-use metal oxides. .

Currently, one of the evaluation methods for flame retardancy is the oxygen index method (JIS
-7201) to measure the oxygen index of polyolefin resin filled with hydrated metal oxide, and calculate the amount of hydrated metal oxide added to make it flame retardant (oxygen index becomes 22 or more). As shown in FIG. 1, it is found that 50 parts by weight or more is required. Next, the amount of smoke produced was measured using an MBS smoke density chamber.
In polyolefin resin with addition of 50 parts by weight of metal hydrate,
Its maximum smoke density (Dm) was 187. On the other hand, for the polyolefin resin alone, Dm was 165 and the oxygen index was 19.0. From this, it was found that although flame retardance can be achieved by adding hydrated metal oxides, the smoke generation properties are rather worsened. When aluminum hydroxide, magnesium hydroxide, calcium hydroxide, etc. were investigated as hydrated metal oxides, polyolefin resins to which these fillers were added produced more smoke than those to which none were added. Furthermore, as a result of examining magnesium carbonate, calcium carbonate, aluminum silicate, magnesium silicate, etc., although it was possible to improve the oxygen index, the amount of smoke generated increased compared to when no additive was added.

Therefore, as a result of intensive studies to develop a polyolefin resin that is flame retardant and has low smoke generation properties, the present invention was achieved.

[Summary of the Invention] The present invention has discovered that by adding zinc borate to the above-mentioned hydrated metal oxide, it is possible to simultaneously achieve low smoke and flame retardancy, and based on this knowledge, improvements have been made. The gist of this is that a hydrated metal oxide and zinc borate are added as a filler to a polyolefin resin in a total of 50 parts by weight, and the ratio of the hydrated metal oxide in the filler is [Detailed Description of the Invention] In the present invention, polyolefin resins include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-α-olefin copolymer, and ethylene-propylene copolymer. It means union.

Examples of hydrated metal oxides include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and the like.

The reason why the combined amount of hydrated metal oxide and zinc borate is 50 parts by weight or more is because if 50 parts by weight or more is not added, the oxygen index of the resin composition will not exceed 21 and it will be flammable. It is. The maximum blending amount varies greatly depending on the type of polyolefin resin and cannot be uniformly determined.

For example, polyolefin resin is mixed with amorphous ethylene and α
- In the case of an olefin copolymer, it can be blended up to about 300 parts by weight, but in the case of polyethylene, which is a crystalline polyolefin resin, the maximum blending amount is about 150 parts by weight.

In the present invention, when the weight ratio of the hydrated metal oxide in the filler is 0.25 to 0.75, excellent low smoke generation properties and flame retardance are exhibited. That is, when the weight ratio is less than 0.25, the oxygen index becomes 21 or less, and when it exceeds 0.75, the amount of smoke generated increases compared to a polyolefin resin composition without additives.

The present invention will be explained below using specific examples.

Prepare a sample of a predetermined size using the formulation shown in Table 1, and
The smoke amount and oxygen index were measured using a BS smoke chamber.

The results are shown in FIGS. 2 and 3. As is clear from FIG. 2, as zinc borate is added, the amount of smoke generation decreases, and when all the filler is placed in zinc borate, the flame retardance shown in FIG. 3 is not satisfied. From Figures 2 and 3,
Hydrated metal oxide/zinc borate ratio is 0.25-0.7
It can be seen that 5 is optimal. Thus, the combination of hydrated metal oxide and zinc borate according to the present invention resulted in a polyolefin composition that is low smoke, flame retardant, and does not generate corrosive gases. Results of similar tests conducted on resins other than ethylene-vinyl acetate copolymer (polyethylene, ethylene, ethyl acrylate copolymer, ethylene propylene copolymer, ethylene-α=niolefin polymer) as polyolefin resins are also shown in Sections 1 to 1. It was the same as Figure 8. The results for the ethylene-ethyl acrylate copolymer and ethylene-propylene copolymer compositions are shown in Tables 2 and 3, respectively. Similar results were obtained when magnesium hydroxide and calcium hydroxide were used as the hydrated metal oxides. Table 4 shows the results for ethylene vinyl acetate copolymer compositions containing magnesium hydroxide.

Table 1]) Ethylene-vinyl acetate copolymer (vinyl acetate amount 25
%) 2) Aluminum hydroxide Table 2 EEA (ethylene-ethyl acrylate copolymer)
100 parts by weight / I = (a) Parts of aluminum hydroxide * (b) Parts of zinc borate Table 3 EP rubber (ethylene-propylene copolymer) 100
Parts by weight Table 4 EVA (ethylene-vinyl acetate copolymer) 100 parts by weight*(
b) Zinc borate (C) Magnesium hydroxide

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between hydrated metal oxides and oxygen index. FIG. 2 is a graph showing the relationship between a hydrated metal oxide, a zinc borate mixture, and the amount of smoke generated. FIG. 8 is a graph showing the relationship between hydrated metal oxide, zinc borate mixture, and oxygen index. Figure 11

Claims (1)

[Claims] (1) The polyolefin resin contains a total of 50 parts by weight or more of a water-use metal oxide and zinc borate as a filler, and (2) the hydrated metal oxide in the filler is aluminum hydroxide, 1'hymagnesium hydroxide,
The flame-retardant, low-smoke polyolefin resin composition according to claim (1), which is selected from the group consisting of calcium hydroxide.