JPS6047296B2 - Polyolefin resin composition containing inorganic filler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition in which a polyolefin resin is blended with an inorganic filler at a high concentration, which has excellent stability against heat and oxidation, and which prevents molded products from whitening over time. .

Recently, in order to improve the rigidity, heat resistance, etc. of polyolefins, and to impart flame retardancy, etc., relatively large amounts of inorganic fillers have been blended into polyolefins. Together with the improvement of compatibility with polyolefins through modification of inorganic fillers and the development of high-efficiency kneading machines, we have been able to blend a large amount of inorganic fillers and still have the flow characteristics and good appearance necessary for injection molding. Polyolefin compositions with mechanical properties have become available. By selecting the type of polyolefin and the type and amount of inorganic filler to be blended here, it is possible to increase the rigidity of the molded product, give it melt properties suitable for vacuum forming, and make it easier to incinerate used products. For example, it is possible to impart combustion characteristics such as a reduction in calorific value and suppression of melt dripping of the combustion body. Furthermore, when magnesium hydroxide is used as the inorganic filler, a composition with excellent flame retardancy can be obtained. Regarding these techniques, the inventor of the present application also published PLASTICSAGE June 1973.
Monthly issue, 1977 June issue and Japanese patent application 1986-7
536 (Japanese Unexamined Patent Publication No. 51-82334). As described above, polyolefin compositions containing a high concentration of inorganic fillers have been developed as new materials to meet new demands, but oxidative deterioration and photodegradation of the polyolefin itself, which is the matrix, remains a problem.

In general, polyolefin resins tend to deteriorate in the presence of oxygen, due to heat or light, and even in compositions containing a high concentration of inorganic fillers, practical performance deteriorates due to the same phenomenon, so stabilizers are usually added. is added to prevent deterioration.

Stabilizers include phenolic, organic phosphorus, and organic sulfur compounds in an amount of 0.01 parts by weight per 100 parts by weight of the composition.
~2.0 parts by weight is blended. Among them, organic sulfur compounds have a large stabilizing effect and are therefore commonly used. As organic sulfur compounds, thiodipropionic acid straight chain fatty acid esters such as distearylthiodipropionate and dilaurylthiodipropionate have been commonly used. However, compositions of polyolefins and high concentrations of inorganic fillers using these stabilizers are
Changes in appearance over time that were not observed in the case of no inorganic filler material occur, causing practical problems.

That is, during use of the molded product at room temperature, after about one month, whitening occurs in a cloudy appearance over a part or the entire surface of the molded product. When used in an atmosphere of elevated temperature, this phenomenon occurs even more quickly. This is a whitening phenomenon due to bleed-out of the stabilizer, and is thought to occur as a result of interaction with the highly concentrated inorganic filler. This phenomenon is more likely to occur as the amount of the inorganic filler is increased, but it is particularly noticeable when the inorganic filler is a metal hydroxide, particularly magnesium hydroxide. As a result of intensive research to solve this problem, the present inventors found that an organic sulfur compound with a specific chemical structure has a deterioration prevention effect that is greater than that of conventional organic sulfur stabilizers, and has a lower bleed-out property. It has been found that the present invention provides a stabilized composition with less whitening over time.

That is, the general formula (where R is an alkyl group having 8 to 30 carbon atoms, and n is 3
Or, by using the alkylthiopropylene acid ester of pentaerythritol represented by 4) as a stabilizer, a composition with excellent stability without whitening even in a polyolefin resin composition containing a high concentration of magnesium hydroxide. You can get it.

The polyolefins used in the present invention include poly-a-olefins such as low-temperature polyethylene, medium-high density polyethylene, polypropylene, and polybutene-1, poly-a-olefins such as propylene-ethylene random or block copolymers, and ethylene-butene-1 random polymers. - Olefin copolymers, copolymers of poly a-olefins and vinyl monomers such as maleic anhydride-modified polypropylene, and mixtures thereof are used.

Among these, polypropylene and a propylene-ethylene copolymer mainly composed of propylene are particularly preferred from the viewpoint of kneading properties with the inorganic filler and properties of the composite such as heat resistance and flexural modulus.

The particle size of the magnesium hydroxide used in the present invention varies depending on the design quality of the composition, but is usually about 0.005 to 50 p, preferably about 0.1 to 10 p. The phenomenon of whitening over time is generally thought to be caused by the interaction between an inorganic filler and an organic sulfur compound, and is particularly noticeable when the inorganic filler is a metal hydroxide, especially magnesium hydroxide. The effect is great.

On the other hand, the organic compound used in the present invention has the following general formula.

(Here, R is an alkyl group having 8 to 30 carbon atoms, and n is 3
or 4) As is clear from this general formula, this sulfur compound is a triester or tetraester of pentaerythritol and P-alkylthiopropionic acid.

In this case, the alkyl groups R may be the same or different in one compound. The general properties of these compounds as stabilizers were previously researched by the present applicant and published in Japanese Patent Publication No. 1973-1.
This is known as 4703. However, the fact that among the organic sulfur compounds represented by the above general formula, only triesters and tetraesters are effective in preventing whitening over time of polyolefin containing a high content of inorganic fillers, which is the problem of the present invention, This is the first time it has been discovered. Such compounds include β-octylthiopropionic acid, β-dodicylthiopropionic acid, and β-octylthiopropionic acid.
monotridecylthiopropionic acid, β-tetradecylthiopropionic acid, β-hexadecylthiopropionic acid, β
- There are tri- or tetra-esters of octadecylthiopropionic acid etc. and pentaerythritol. The composition of the present invention may further contain various additives in desired proportions depending on the performance required of the product.

For example, 1,1,3-tris(5-t-butyl-4-
Phenolic antioxidants such as hydroxy-2-methylphenyl)butane, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, tris(dinonylphenyl)phosphite , phosphorus-based antioxidants such as tris(dinonylphenyl) phosphite, and ultraviolet absorbers,
Antistatic agents and the like can also be added. Also, ethylene-
Impact modifiers such as propylene rubber, butadiene and isoprene, dispersants such as calcium stearate and magnesium stearate, and pigments such as carbon black and titanium white can also be added as necessary.

In producing the composition of the present invention, the above-mentioned components can be produced using a conventional kneading method, ie, a single screw extruder, a twin screw extruder, a roll, a Panbury mixer, etc.

At that time, it is possible to directly mix and knead all the components at the same time, but in advance, a masterbatch containing an inorganic filler masterbatch, an organic sulfur stabilizer masterbatch, or both can be prepared in advance. May be blended. Example 1 Polypropylene (MH4 manufactured by Mitsubishi Yuka), ethylene propylene copolymer (BC4 manufactured by Mitsubishi Yuka), and high-density polyethylene (JK-10 manufactured by Mitsubishi Yuka) were used as base resins, and magnesium hydroxide (average particle size 0 .2 μ) as an inorganic filler and an organic sulfur stabilizer as shown in Table 1 were mixed and kneaded using a roll (tetrakis [methylene-3-(3
, 5-di-t-butyl-4-hydroxyphenyl)propionate] methane was blended at 0.1% by weight in all samples).

The sheet obtained by compression molding was left for 21 days at a high temperature of 40'C and a humidity of 80%, and the whitening phenomenon over time was observed, and the rate of change in surface gloss (cross) was observed. It was measured.

The cross change rate was measured using a gloss meter UGV-3 manufactured by Suga Test Instruments Co., Ltd.
It was measured using a mold according to JIS-Z-8741 and calculated using the following formula. The cross change rate increases as the stabilizer bleeds out and a whitening phenomenon occurs over time. on the other hand,
A thickness of 0.5 mm obtained by compression molding the same blended mixture
The heat aging resistance was tested by heating a test piece in an open gear and measuring the time until cracks appeared on the sample surface.

The heating temperature is 110°C for samples with high-density polyethylene as the base resin, and 15°C for others.
It was 0°C. The results of this example are as shown in Table 1, and the composition of the present invention showed no whitening due to bleed-out of the stabilizer, and the gloss change rate by optical measurement was zero, compared to the control example. It can be seen that it shows a remarkable effect compared to . It can also be seen that the heat aging resistance of the product of the present invention is more than twice as effective as that of the control product.

Example 2 Ethylene-propylene copolymer (Mitsubishi Yuka?4) 50
Magnesium hydroxide 5 parts by weight and average particle size 0.2μ
Distearyl thiodipropionate was added as an organic sulfur stabilizer to 100 parts by weight of the composition consisting of 0 parts by weight.
3 parts by weight of (1) and 0 of tetrakis[methylene(3-octadecylthiopropanoate)]methane
．． (2) to which 3 parts by weight had been added were separately kneaded and granulated using a single-screw extruder.

Add carbon black to these two materials in composition 1.
The mixture was dry blended in an amount of 1.5 parts by weight per part by weight, and then injection molded to form a back cover for a television cabinet. This molded product was placed in a high-temperature, high-humidity room at a temperature of 40'C and a humidity of 80%.
When left for 0 days, the back cover of (1) containing distearyl thiodipropionate showed a phenomenon of whitening over time; )] The back cover containing methane showed no whitening phenomenon over time and had a good appearance.

Claims (1)

[Claims] 1.0.0% of an organic sulfur stabilizer having the following structure is added to 100 parts by weight of a total blend of 90 to 20 parts by weight of polyolefin resin and 10 to 80 parts by weight of magnesium hydroxide.
Inorganic filler-containing polyolefin resin composition characterized by containing 01 to 2.0 parts by weight ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ (Here, R is an alkyl group having 8 to 30 carbon atoms, and n is 3 or 4).