JPS6144090B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an inorganic highly filled polyolefin resin composition. Polyolefin resins are known to have excellent properties and are used in large quantities for a wide variety of applications. In recent years, various attempts have been made to fill polyolefin resins with various inorganic compounds for the purpose of making them pollution-free, flame retardant, and resource-saving. Taking aluminum hydroxide as an example of an inorganic compound, when a polyolefin resin is filled with a hydrate of aluminum hydroxide, the water of crystallization of the hydrate separates under high temperatures such as when exposed to flame. As a result, it exhibits extremely high flame retardancy and self-extinguishing properties, and is known as an excellent flame retardant composition. This flame-retardant composition made of aluminum hydroxide is less expensive than flame-retardant compositions containing other halogen-based flame retardants, has less deterioration in various electrical properties, and is especially effective when burned. It has excellent features such as no generation of harmful gases caused by halogens and less damage to humans and various equipment due to corrosion. Even in the case of flame retardant compositions, as a result of the tendency to require extremely high levels of flame retardancy, inorganic compounds such as aluminum hydroxide are added to polyolefin resins, etc. There is an urgent need to develop a so-called inorganic-rich polyolefin resin composition that is filled with a large amount of inorganic material. However, in general, it is not always easy to knead a certain amount or more of an inorganic compound into a polyolefin resin because there is a certain limit to the dispersibility or compatibility of the inorganic compound in the resin. Currently, it is possible to fill 100 parts by weight or more of an inorganic compound to 100 parts by weight of resin using methods such as using special kneading equipment; In many cases, various physical properties are significantly decreased, as typified by a significant decrease in tensile elongation at break, and the reality is that it is extremely difficult to obtain a composition with practically satisfactory properties. As a method to overcome this drawback, it has been proposed to use a so-called coupling agent to modify the surface of the inorganic compound to be filled, and typical coupling agents include silane coupling agents and titanate coupling agents. Are known. However, although this silane-based coupling agent is effective for modifying silicate-based inorganic compounds, it cannot be applied to other materials due to lack of reactivity, and the inventors' study results show that this silane-based coupling agent It has been found that although the use of the agent increases the rigidity of the composition, the desired effect of improving tensile elongation at break is hardly observed. Furthermore, when a titanate coupling agent is used, it may show an effect of improving the tensile elongation at break of the composition, but since the titanate coupling agent is very expensive, the serious drawback of high cost cannot be avoided. do not have. An example of a method using such a coupling agent is shown in JP-A-51-101049, but in this case, the impact strength of the composition is improved, but the above-mentioned improvement in the tensile elongation at break is hardly improved. I can't wait. In recent years, for example, a very high level of flame retardancy has been required for insulated wires from a safety standpoint, and it is necessary to maintain and improve the tensile properties, especially tensile elongation at break, of such flame-retardant insulated wires. Therefore, there is a strong demand for a composition that has a large amount of inorganic compound filled and has improved tensile properties compared to the above-mentioned inorganic-rich polyolefin resin composition. As a result of intensive studies in order to meet such demands, the inventors have discovered that blending an appropriate amount of maleated polybutadiene into such inorganic-highly filled polyolefin resin compositions exhibits surprising effects. He completed this invention. That is, the present invention provides a polyolefin resin composition comprising 50 to 300 parts by weight of a finely powdered inorganic compound and a desired amount of various additives as necessary, based on 100 parts by weight of a polyolefin resin. This is an inorganic-highly filled polyolefin resin composition characterized in that it contains 1 to 50 parts by weight of maleated polybutadiene based on 100 parts by weight of the compound. Although it has not necessarily been clear what mechanism of action produces the effects of this invention, it is believed that the succinic acid group of the maleated polybutadiene present in the composition reacts with the hydroxyl group present on the surface of the inorganic compound. It is presumed that this is because the maleated polybutadiene coats the surface of the inorganic compound through chemical bonds, and as a result, the compatibility between the polyolefin resin, which is the matrix phase, and the inorganic compound is significantly improved. The polyolefin resins used in this invention include low-density, medium-density, and high-density polyethylene, polypropylene, homopolymers of olefins such as polybutene-1, ethylene vinyl acetate copolymers, ethylene ethyl acrylate copolymers, and ethylene propylene copolymers. Ethylene-α- including polymers
These include ethylene copolymers such as olefin copolymers, propylene copolymers, olefin elastomers such as ethylene propylene rubber, and ethylene propylene diene compound rubber. It also collectively refers to mixtures of two or more of these resins or elastomers, and mixtures in which these resins or elastomers are mixed with other resins or elastomers. In this invention, the polyolefin resin used as the base polymer is particularly preferably polyethylene having a density of 0.910 to 0.945 g/cm ³ and a melt index of 0.01 to 2.0 g/10 min. Among the ethylene-based copolymers, ethylene-vinyl acetate copolymers having a vinyl acetate content of 10 to 75% by weight are particularly preferred. According to the results of various studies by the present inventors, the above-mentioned polyethylene
10-75 parts by weight and 90-90 parts of ethylene vinyl acetate copolymer
The blended polymer obtained by blending 25 parts by weight was the best. Next, there are many types of inorganic compounds in this invention depending on the purpose of use, such as aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, tin oxide hydrate, zirconium oxide hydrate, etc. Various hydrates, carbonates such as calcium carbonate and magnesium carbonate, talc,
It refers to silicates such as clay, bentonite, and attapulgite, sulfates and sulfites such as gypsum, or mixtures of two or more thereof, as well as potassium metaphosphate and melamine phosphate. Among these inorganic compounds, in order to impart the above-mentioned flame retardancy, hydrates containing a large amount of crystallization water and whose decomposition start temperature is in the range of 150 to 450°C, such as aluminum hydroxide and boric acid, are recommended. Particularly preferred are zinc, magnesium hydroxide, calcium hydroxide, and the like. These inorganic compounds are preferably used in the form of fine powder with an average particle size of 0.01 to 30μ, particularly preferably 0.05 to 10μ, and the amount added is 50 to 300 parts by weight, especially 100 parts by weight of the polyolefin resin. Preferred is 80 to 250 parts by weight. Next, it is preferable that the maleated polybutadiene used in the present invention has a relatively small molecular weight and melts and softens at 100 DEG C. or lower, and specifically, one having an average molecular weight of 1,000 to 5,000 is preferable. The number of succinic acid groups contained in one molecule is preferably 0.2 to 1.0 per molecule; if the number is less than this range, the effect of this invention cannot be obtained, and if the number is more than this, the dehydration reaction between succinic acid groups occurs. etc., which is undesirable. The amount of maleated polybutadiene added is 1 to 50 parts by weight, preferably 3 to 30 parts by weight, per 100 parts by weight of the inorganic compound mixed with the polyolefin.If this lower limit is not reached, the effects of the present invention will not be apparent. On the other hand, if the upper limit is exceeded, the volume effect of the maleated polybutadiene appears and the tensile properties of the composition deteriorate, which is not preferable. Additives used for various purposes are added to the composition of the present invention in amounts depending on the purpose. For example, crosslinking agents such as dicumyl peroxide, crosslinking aids such as divinylbenzene, blowing agents such as azodicarbonamide, other flame retardants such as decabromodiphenyl oxide, flame retardant aids such as antimony trioxide, and stearin. Lubricant such as zinc acid, 4,4'-
Examples include anti-aging agents such as thiobis(6-t-butyl-methylphere), metal anti-aging agents such as 3-(N-salicyloyl)amino-1,2,4-triazole, carbon black, colorants and the like. Further, according to the present invention, the composition can be subjected to electron beam,
It is also possible to crosslink by irradiating with gamma rays, ultraviolet rays, etc. The composition of the present invention can generally be kneaded or molded using conventional resin kneading or molding equipment such as a two-roll mill, Banbury mixer, extruder, or injection molding machine. The above-mentioned maleated polybutadiene is usually preferably added in the above-mentioned kneading step, but a pretreatment method of blending and stirring with an inorganic compound may also be adopted. The composition of the present invention can be used not only as a covering material for highly flame-retardant electric wires as exemplified above, but also in a wide range of applications such as various molded articles such as pipes and foams. As is clear from the above description and the examples below, this invention can significantly improve the tensile properties of an inorganic-highly filled polyolefin resin composition by simply adding maleated polybutadiene. Its industrial value is extremely high. The present invention will be specifically explained below with reference to Examples. Example 1, Comparative Examples 1 to 2 Aluminum hydroxide (Hygilite H-42M, Showa Denko Co., Ltd., Average particle size
1.0 μ) 150 parts by weight, maleated polybutadiene (Nippon Petrochemicals, M-2000-20, molecular weight 2000,
(acid value: 20mgKOH/g) and 0.5 parts by weight in a small experimental mixer, formed into a 1mm thick sheet using a hot press to obtain a No. 3 dumbbell piece in accordance with JISC-3005, and tested for tensile properties using a Tensilon tester. The results are shown in Table 1. For comparison, epoxidized polybutadiene (Nippon Petrochemical Co., Ltd., LPE-
The results are shown in the same table except that the same amount of unmodified polybutadiene (Nippon Petrochemical Co., Ltd., B-3000) was used as Comparative Example 2.

[Table] According to the results in the table above, the examples showed a tensile elongation at break of over 400%, while the comparative examples showed a tensile elongation of over 50%.
% or even lower. Example 2 Same polymer as used in Example 1
To 100 parts by weight, 150 parts by weight of commercially available aluminum hydroxide powder (Showa Denko Co., Ltd., trade name Hygilite H-32, average particle size 3.8μ) was added, and further commercially available aluminum hydroxide powder was added at various ratios shown in Table 2. Maleated polybutadiene (Nippon Petrochemical Co., Ltd., M-3000-20) was added and kneaded in a small laboratory mixer, and evaluated in the same manner as in Example 1. The results are also listed in Table 2. There is a preferable range for the amount of the maleated polybutadiene added, and it is found that 2.5 to 35 parts by weight is preferable in order to achieve suitable elongation behavior.

[Table] Example 3 This example shows the results when maleated polybutadienes having different molecular weights and degrees of maleation were used. The polymer and inorganic filler used were the same as in Example 2. All maleated polybutadienes were manufactured by Nippon Petrochemicals, and the amount added was 15 parts by weight based on 100 parts by weight of the polymer.

[Table] Table 3 summarizes the results of the tensile test. both
Although the elongation is over 100%, there is considerable dependence on the degree of maleation as indicated by the acid value. Example 4 Ethylene-vinyl acetate copolymer (Mitsui Polychemical Co., Ltd., EV-360, vinyl acetate content 25%, density 0.95
To 100 parts by weight of MI2), 150 parts by weight of magnesium hydroxide (manufactured by Kamishima Chemical Co., Ltd., average particle size 0.1μ) was added, and further maleated polybutadiene (trade name: NISSO-BN resin; BN-1000) from Nippon Soda Co., Ltd. 10 parts by weight (average molecular weight: about 1000, acid value: 110) were added, kneaded in the same manner as in Examples 1 and 2, and evaluated in the same manner as in Example 1. The result of the tensile test is tensile elongation 4.52% tensile strength 62
It was Kg/ ^cm2 . Example 5 Ethylene-vinyl acetate copolymer (Mitsui Polychemical Co., Ltd., EV-360, vinyl acetate content 25% by weight, density
0.95 g/cc, MI: 2) 80 parts by weight, high-density polyethylene (Showa Yuka Co., Ltd., Showa Rex 4002B,
MI; 0.2, density: 0.940) 20 parts by weight, fine aluminum hydroxide powder (Showa Denko, Higilite H-
42M) 150 parts by weight, zinc stearate (Reagent 1
A mixture consisting of 1.5 parts by weight of an antiaging agent (Ouchi Shinkosha Co., Ltd., Nokura Tsuku 300) was mixed in a small experimental mixer, and maleated polybutadiene (Nippon Petrochemical Co., Ltd.) was mixed with this mixture. M
-3000-20) was added in a proportion of 7.5 parts by weight, thoroughly kneaded, and then subjected to a tensile test in the same manner as in Example 1. The results showed a tensile elongation at break of 505% and a tensile strength of 82 Kg/cm ² . For comparison, the above composition to which no maleated polybutadiene was added had tensile elongation at break,
108%, and the tensile strength was only 65 Kg/cm ² .

Claims (1)

[Claims] 1. In a polyolefin resin composition prepared by blending 50 to 300 parts by weight of a finely powdered inorganic compound and desired amounts of various additives as necessary with respect to 100 parts by weight of the polyolefin resin, the inorganic compound
1. A highly inorganic-filled polyolefin resin composition containing 1 to 50 parts by weight of maleated polybutadiene based on 100 parts by weight.