JPH0629344B2 - Flame-retardant resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flame-retardant resin composition, and more particularly to a polyolefin resin composition which does not deteriorate mechanical strength and processability and does not cause a drip phenomenon during combustion. It is a thing.

Conventional technology and its problems It is widely known to add an inorganic flame retardant composed of each compound such as halogen, phosphorus, antimony, and boron in order to make a synthetic resin flame-retardant. In addition to causing corrosion and contamination of molds and the like by corrosive gas, it has a side effect that it has a large smoke emission because it mainly has a flame retardant action in the gas phase and generates a unique gas. There was a problem. Therefore, it has been attempted to add an inorganic filler to reduce the side effects due to the combined effect with the flame retardant, but adding a large amount of the filler causes a new problem of deterioration of processability and physical properties. To do. As a countermeasure, it has been proposed to use aluminum hydroxide as a filler (Plastics Vol.22 No.8). Aluminum hydroxide is inexpensive and non-toxic, has low smoke generation, and has a large heat absorbing effect by dehydration decomposition of crystal water, so that it can be used in combination with a flame retardant as a filler, and also has a flame retardant effect when added alone. It is expected that it is suitable for vinyl chloride resin, unsaturated polyester, epoxy resin, and phenol resin.

However, in addition to aluminum hydroxide, which has a flame retardant that doubles as such a filler, when a hydrated inorganic compound such as magnesium hydroxide, which is expected to have a flame retardant effect, is added to the polyolefin resin, it is significantly larger than the resin. The flame retardant effect cannot be expected unless it is added to, and generally the same weight% or more as the polyolefin resin is required. Therefore, the workability and the original performance of the resin deteriorate significantly,
It could not be used for molded products such as cable jackets and electrical equipment exteriors.

OBJECT OF THE INVENTION It is an object of the present invention to provide a polyolefin resin composition which does not impair the original performance and processability of the resin such as mechanical strength, and has an excellent flame retardant effect, especially the effect of preventing the drip phenomenon during combustion. I am trying.

Means for Solving the Problems In the present invention, 100 parts by weight of a polyolefin resin, a mixing range of a water-containing inorganic compound and antimony trioxide is from 20:80.
A means for solving the above problems was obtained by comprising 50: 300 parts by weight of a mixed system of 80: 20% by weight and 0.5-10 parts by weight of fine particles of calcium silicate.

Polyethylene resin and polypropylene resin are suitable as the polyolefin resin forming the flame-retardant resin composition having such a structure, and low as the polyethylene resin.
Homopolymers such as medium and high density polyethylene and ethylene-
Examples of the copolymer include vinyl acetate and ethylene-acrylic acid eruter, and as the polypropylene resin, a homopolymer, a copolymer with a monomer, and the like are also used. Further, a combination system of a thermoplastic resin having compatibility with these olefin resins or a rubber-like polymer substance, or a cross-linked product thereof is also used.

Next, a mixed system of a hydrous inorganic compound and antimony trioxide was used in the present invention in order to eliminate the flammability which is a drawback of the polyolefin resin and to impart a flame retardant effect. Examples of water-containing inorganic compounds include aluminum hydroxide, magnesium hydroxide, zinc borate, kaolin clay, calcium carbonate, etc. One or more of them are used, but those that do not dehydrate and decompose due to heat during molding are used. There is a need to. Antimony trioxide is one of the most well-known flame retardants, and its disadvantages of being expensive and having a large smoke emission are not only reduced by using it together with a hydrated inorganic compound, but this mixed system is synergistic. It is also known that due to the action, it has a high oxygen index and is expected to have an excellent flame retardant effect.

In the present invention, it is preferable to use magnesium hydroxide as the hydrated inorganic compound, and the mixed system with antimony trioxide has good compatibility with the polyolefin resin. The mixing ratio of these is arbitrary, and is selected in consideration of economical efficiency, smoke generation, etc., but in general, they are mixed within the range of 20:80 to 80:20 (% by weight). The mixed system is used in an amount of 50 to 300 parts by weight, preferably 75 to 200 parts by weight, per 100 parts by weight of the polyolefin resin. If the amount is larger than that of the part, the original performance and moldability of the resin are deteriorated, which is not preferable.

As described above, a mixed system of a hydrous inorganic compound and antimony trioxide 50 to 300 per 100 parts by weight of the polyolefin resin.
The one with added parts by weight gives excellent flame retardancy, but on the other hand, there is a problem that the composition melts during combustion to cause a drip phenomenon, and the one with a mixed system added at a high concentration has mechanical strength. And significantly deteriorates workability.

Then, the inventor of the present application, as a result of research on means for preventing the drip phenomenon and deterioration for workability, found that fine particles of calcium silicate are effective. As the fine particles of calcium silicate, petal-like particles having a length of 1 to 5 µ, scaly particles having a length of 3 to 50 µ, and fibrous particles having a length of 20 to 300 µ are suitable. 0.5 to 10 parts by weight per 100 parts by weight of the resin, especially 1
The petal-shaped one with an extremely large specific surface area of about 00 to 500 m ² / g is optimal.

Such calcium silicate microparticles have the function of preventing the drip phenomenon during combustion as well as deteriorating the mechanical strength and workability even if a mixed system of a hydrous inorganic compound and antimony trioxide is added at a high concentration. In addition, it is stable even after a long period of time, and has the effect of not cracking when a carbonized layer is formed by flame contact.

The fine particles of silicic acid anhydride have a similar function,
Not used because it has hygroscopicity and loses its effect over a long period of time.

Further, the resin composition of the present invention comprises a heat stabilizer, an ultraviolet absorber,
It does not prevent the addition of additives such as plasticizers, lubricants, pigments, antistatic agents and dispersants.

Effects of the Invention According to the present invention, it is possible to add a high concentration of a mixed system by adding fine particles of calcium silicate to a polyolefin resin using a mixed system of a water-containing inorganic compound and antimony trioxide as a flame retardant. , Polyolefin resin composition with excellent flame retardancy that not only can expect excellent flame retardant effect without deteriorating physical properties and processability of resin such as mechanical strength, but also can prevent drip phenomenon during combustion. Is provided.

Example 1 The presence or absence of the drip phenomenon was examined for the product of the present invention to which calcium silicate was added and the comparative product not added.

In this Example and Examples 2 to 4 described later, the numerical values of the substances used are parts by weight, and the antioxidant 1
A lubricant 0.4 was added, EVA of the polyolefin resin was manufactured by Toyo Soda Kogyo Co., Ltd., trade name Ultrasen UE-627, and fine particles of calcium silicate were manufactured by Tokuyama Soda Co., Ltd., trade name Florite R.

Then, magnesium hydroxide, aluminum hydroxide, and antimony trioxide are mixed with a mixer, and the other components are mixed with an 8-inch test roll at 110 to 120 ° C. for 7 minutes after winding the roll, and then the press temperature is 170 ° C. and preheating is performed. 4 minutes,
Each sample was prepared by press molding under the condition of pressing time (100 kg / cm ² ) for 3 minutes.

The method and conditions for measuring physical properties are as follows: Tensile test: JISK-6730
(However, 23 ° C, 200 mm / min), specific gravity is JIS K
-7112 (however, 23 ° C, water substitution method), melt flow rate is JIS K7210 (however, 190 ° C, 21
60 kg / cm ² load, 10 minutes), embrittlement temperature is JIS K
-6723, the oxygen index was according to JIS K-7201. The presence or absence of the drip was observed by forcibly burning the test piece for measuring the oxygen index vertically. The unit of breaking strength and elongation in the tensile test is kg / cm ² ,%.

Example 2 EVA 100, magnesium hydroxide 70, antimony trichloride 30, antioxidant 1 and lubricant 0.4 The effects on the physical properties of calcium silicate were investigated by changing the amount of calcium silicate added.

The method and conditions for sample preparation and physical property measurement are the same as in Example 1.

Example 3 The difference in effect depending on the type of polyolefin resin was examined. In addition to EVA, low density polyethylene and polypropylene were used as resins, and antioxidant 1 and lubricant 0.4 were added to each sample.

A sample using polypropylene was rolled with an 8-inch test roll at 175 to 180 ° C. and kneaded for 5 minutes,
Next, press molding was performed under the conditions of a press temperature of 190 ° C., a preheating time of 5 minutes, and a pressurizing time (100 kg / cm ² ) of 2 minutes. Other samples were prepared under the same conditions as in Example 1. The methods and conditions for measuring physical properties are the same as in Example 1.

Example 4 The difference in the effect of crosslinking the resin was examined. Antioxidant 1 and lubricant 0.2 were added to all the samples, and the 8-inch test roll was rolled at 120 to 125 ° C and kneaded for 5 minutes, then crosslinked at 170 ° C for 15 minutes and gel fraction was about 70%. And The methods and conditions for measuring physical properties are the same as in Example 1.

Example 5 Differences in physical properties when calcium silicate and anhydrous silicic acid were added were examined. All samples were prepared in the same manner as in Example 1 except that antioxidant 1 and lubricant 0.3 were added. In addition, the methods and conditions for measuring physical properties are the same, and the presence or absence of moisture absorption of the sample is 23 to 25.
The evaluation was carried out by leaving it in a constant temperature and humidity tank saturated at 0 ° C. for 2 days.

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Claims (2)

[Claims] 1. A mixture range of 100 parts by weight of a polyolefin resin, a hydrous inorganic compound and antimony trioxide 20: 8.
0 to 80: 20 wt% mixed system 50 to 300 parts by weight,
A flame-retardant resin composition comprising 0.5 to 10 parts by weight of calcium silicate fine particles. 2. The composition according to claim 1, wherein the hydrous inorganic compound is magnesium hydroxide.