JPS6131138B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a self-extinguishing resin composition containing a large amount of magnesium hydroxide. Specifically, the present invention relates to a self-extinguishing resin composition for injection molding, which is made by blending magnesium hydroxide with polyolefin. Conventionally, flame-retardant resins containing antimony oxide and halogen compounds have been known.
In this type of composition, antimony halides are produced by heating during combustion. This antimony halide is a heavy gas, which is thought to give it self-extinguishing properties. However, antimony oxide and many halogen compounds are harmful to the human body, and self-extinguishing compositions of this type pose the risk of harmful gases in the event of a fire. On the other hand, it is known that a flame-retardant plastic can be obtained by blending a large amount of fine powder such as aluminum hydroxide with polyolefin.
However, the blending of aluminum hydroxide is good when the melting point of the polyolefin is extremely low, but when the melting point is somewhat high, such as polypropylene or high-density polyethylene, the thermal decomposition of aluminum hydroxide occurs at 200°C, which is close to the melting point of the polyolefin. Since the process starts from a nearby point, dehydration and foaming phenomena occur during the kneading and molding process, which has the disadvantage that molded products with practical performance cannot be obtained. The present inventors previously investigated various hydroxides and hydrated compounds as inorganic compounds that thermally decompose and generate moisture during heating in place of aluminum hydroxide, and found that only magnesium hydroxide It has been found that it is possible to impart desired flame retardancy without causing foaming during molding. This means that most hydroxides and hydrates are
Moisture begins to be generated due to thermal decomposition at temperatures of 100 to 2550°C, and dehydration occurs during blend molding of polyolefin.
In contrast, magnesium hydroxide only generates moisture when it reaches a high temperature of about 300℃, and the generation of moisture is completed at 350℃, which is close to the decomposition temperature of polyolefin. It is presumed that this is because the generated moisture efficiently contributes to preventing combustion of the polyolefin. However, polyolefin compositions containing magnesium hydroxide have the disadvantage that silver streaks occur during injection molding, and the molded products do not have sufficiently high impact resistance and folding strength. In order to improve this point, the present inventors conducted research and added an ethylene-propylene random copolymer of a specific viscosity to a polyolefin composition containing magnesium hydroxide. Instead, the use of magnesium hydroxide with a limited specific surface area was found to be effective in improving the impact resistance of molded products and the appearance of molded products such as silver streaks (JP-A-52-21047 and JP-A No. 52-21047). 123442). However,
These composites still have problems with folding strength,
Therefore, its practical range was narrowed (particularly in an atmosphere with a relatively high temperature, the folding strength was extremely reduced, making it unusable). An object of the present invention is to provide a magnesium hydroxide-containing self-extinguishing resin composition that provides a molded article with good surface appearance, impact resistance, and folding strength after molding. The present invention aims to achieve the above-mentioned object, in particular, to improve the folding strength.
5% by weight and 35-75% by weight of magnesium hydroxide with a specific surface area of 25 m ² /g or less and 0.1-20% by weight of rubbery ethylene-propylene random copolymer with an ethylene (C ₂ ) content of 45-85% by weight. A self-extinguishing resin composition characterized in that the rubbery ethylene-propylene random copolymer is dispersed and blended so that the average dispersed particle size is 2μ or less. This is what we provide. Here, the average size of dispersed particles of 2μ or less means that 80% or less of the dispersed particles have a maximum size of 2μ or less, and the number of particles exceeding 2μ is less than 20%. It is something. The rubbery ethylene-propylene random copolymer used in the present invention has a C ₂ content (hereinafter referred to as weight percentage) in the range of 45 to 85%, and has a Mooney viscosity {hereinafter referred to as weight percentage). ML ₁₊₄ measured in accordance with JIS-K6300
(100°C)} is preferably in the range of 5 to 120. Those with a C ₂ content of less than 45% are extremely difficult to manufacture, and those with a C 2 content of more than 85% lack rubber performance. Furthermore, if the Mooney viscosity is less than 5, the flexibility will be excessive, and if it is greater than 120, the moldability of the composition will be reduced. The blending amount of the rubbery ethylene-propylene random copolymer is 0.1 to 20% by weight; if it is less than 0.1% by weight, the effect of improving folding strength will be small and the impact strength will not be sufficient, and if it is more than 20% by weight, the rigidity will be lowered. decreases. The rubbery ethylene-propylene random copolymer is made of ethylidenenorbornene, dicyclopentadiene, 1-4, which are commonly used as rubber crosslinking agents.
It may contain an appropriate amount of a component such as hexadiene or the like that is normally used. The α-olefin homopolymer or copolymer used in the present invention is an α-olefin such as ethylene or propylene.
Homopolymers of olefins or crystalline block or random copolymers of α-olefins and other α-olefins, such as ethylene-propylene random copolymers, crystalline propylene-ethylene block copolymers, ethylene-butene -1 random copolymer, propylene-butene-1 random copolymer, or a copolymer mainly composed of α-olefin with polar monomers such as vinyl acetate, maleic anhydride, and acrylic acid (including graft copolymers) ) and mixtures thereof. In particular, propylene with an ethylene content of less than 10%
Ethylene random copolymers are preferred, and it has been found that among them, the higher the randomness of ethylene, the better the results. It has been found that the following copolymers are particularly suitable as such copolymers with high randomness. That is, during production, propylene and some ethylene are simultaneously mixed into a polymerization tank to cause a polymerization reaction, and the infrared absorption spectrum has a peak intensity of around 733 cm ^-1 (peak absorbance)/(thickness of measurement sample). )...... is 0.2 to 11.5 mm ^-1 (0.1 as _C2 content)
~5%), and the peak intensity around 722 cm ^-1 derived from minute amounts of blocked ethylene caused by non-uniform polymerization is 0.06 mm ^-1 (0.3% in terms of _C2 content) or less. When a polymer is used, the rubbery ethylene-propylene random copolymer can be easily finely dispersed, and a molded article having a good quality balance can be obtained. In addition, various antioxidants, ultraviolet absorbers, antistatic agents, neutralizing agents, lubricants, pigments, etc. can be added as desired. Antioxidants are usually added to polyolefins. As the antioxidant, any of commonly used phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. may be used. The blending amount of the α-olefin homopolymer or copolymer is 5 to 64.9% by weight. If it is less than 5% by weight, it will be difficult to impart moldability, and if it is 65% by weight or more, it will be difficult to impart flame retardancy. . The magnesium hydroxide used in the present invention has a specific surface area of 25 m ² /g or less, preferably 4 m ² /g or more, and 20 m ² /g.
Use one with a weight of less than g. If the specific surface area is larger than 25 m ² /g, the fluidity, impact resistance, and appearance of the molded product remain at a low level. In addition, because the rubbery ethylene-propylene random copolymer is dispersed with an average particle size of 2μ or less, the specific surface area is 25
It is preferable to use magnesium hydroxide of m ² /g or less. The above magnesium hydroxide may be subjected to the following surface treatment. That is, surface treatment methods include monomers or polymers having polar groups, such as stearic acid, oleic acid, caprylic acid, lauric acid, acrylic acid, acrylic acid derivatives, metal salts thereof, polyacrylic acid, etc. The surface may be modified using polymers of acrylic acid derivatives and metal salts thereof. As the surface modification treatment method, a desired modification treatment such as a chemical reaction method, a surface polymerization method, a mechanochemical method, etc. is performed. The blending amount of magnesium hydroxide is 35 to 75% by weight. If it is less than 35% by weight, it cannot be put to practical use in terms of flame retardancy, and if it is more than 75% by weight, it will have poor flowability and impact resistance during molding. Therefore, it cannot be put to practical use. In addition, in order to adjust the flowability during molding, a fatty acid metal salt can be added in an amount of 1 to 6% by weight, preferably 2 to 3.5% by weight based on magnesium hydroxide. As the fatty acid metal salt, it is particularly preferable to include aluminum, zinc, magnesium or calcium metal salts of fatty acids having 8 to 20 carbon atoms. Furthermore, 0.1 to 5% by weight of an organic cellulose filler such as wood powder can be blended together with the fatty acid metal salt. Furthermore, other rubber components such as styrene-butadiene rubber and neoprene rubber, calcium carbonate, zeolite, clay, talc, silica, asbestos, glass fiber, mica, etc. may be added in appropriate amounts within a range that does not impair the quality of the molded product. Inorganic fillers other than magnesium hydroxide, pigments such as carbon black, other antifoaming agents, dispersants, etc. can also be blended. The above-mentioned inorganic filler can also be used after being subjected to surface modification similar to magnesium hydroxide. As a kneading method for obtaining the composition of the present invention, a usual melt kneading method using a roll, a Banbury mixer, a single screw extruder, a twin screw extruder, etc. is used. The kneading temperature is 300℃ above the melting point of polyolefin.
It is desirable to carry out the test in a temperature range below ℃. In order to facilitate rapid dispersion of the rubbery ethylene-propylene random copolymer, the rubbery ethylene-propylene random copolymer is prepared in advance into beads, pellets, crumbs, etc. with a maximum dimension of 10 mm or less. In addition to shaping the resin, it is preferable to use a strong kneading type extruder, and it is also desirable to extend the kneading time to a certain extent without deteriorating the quality of the resin. Another kneading method is to dissolve the rubbery ethylene-propylene random copolymer in advance in a solvent such as hexane, add magnesium hydroxide therein, and evaporate the solvent while stirring to remove the solvent from the surface of the magnesium hydroxide. It is also possible to use a method in which a rubbery ethylene-propylene random copolymer is adhered to the polymer and then melt-kneaded with the α-olefin homopolymer or copolymer. The rubbery ethylene-propylene random copolymer in the composition obtained by the above method is
The matrix polymer, α-olefin homopolymer or copolymer, is uniformly dispersed with an average particle size of 2 μm or less, centered on the relatively amorphous portion. Thus, the produced composition has significantly improved folding strength while retaining good impact strength and self-extinguishing properties. Hereinafter, aspects of the present invention will be explained with reference to Examples. Example 1 The various components shown in Table 1 were stirred for 5 minutes in a mixer, and then intensively kneaded and granulated using a twin screw extruder (temperature: 260°C). The resulting composition was molded into a rubber-like ethylene-propylene random copolymer using a non-vented screw-in-line injection molding machine (Model SJ-35 manufactured by Kakaki Seisakusho, molding temperature 220°C, injection pressure 1000 Kg/cm ² ). Test piece for measuring dispersion unit of coalescence, test piece for measuring folding strength, test piece for impact resistance evaluation, and 100 parts by weight of the composition
Flame retardant evaluation specimen blackened by adding 1.5 parts by weight of carbon black powder (for UL standard - length 127
mm, width 12.7mm, thickness 3.18mm and for BS standard - length
100mm, width 25mm, thickness 3.0mm) was molded and evaluated. The results are shown in Table 1. However, the measurement of the dispersion unit of the rubbery ethylene-propylene random copolymer is performed using a sample (length 50 mm,
The fractured surface (width 50mm, thickness 4mm) was fractured at -195℃, and the fractured surface was immersed in hydrochloric acid at room temperature for 30 minutes to perform etching treatment.The fractured surface was then observed with a scanning electron microscope. (4 or more locations) 8μ×
The maximum partial size of the particles dispersed in an area of 8μ was measured and judged based on the concept of average value defined in the text above. The bending strength was measured in an air atmosphere at 20°C and 50°C in accordance with the measurement method of JIS-K7203, and the specimen dimensions were 80 mm in length, 10 mm in width, 4 mm in thickness,
The test was conducted with a distance between fulcrums of 30 mm, a pressure wedge radius of 2 mm, a support base radius of 2 mm, and a pressure wedge descending speed of 500 mm/min, and the maximum stress at which the specimen was significantly deformed was measured. Impact strength is JIS-K7110 (notched isot) and flame retardancy is UL standard No.94 and BS standard.
Tested according to No.415. Furthermore, the surface treatment of magnesium hydroxide was carried out by the following method. That is, 3% by weight of magnesium stearate based on magnesium hydroxide was dissolved in benzene at 80°C, magnesium hydroxide was added thereto, the benzene was removed by evaporation, and the surface of the magnesium hydroxide was modified. The specific surface area of magnesium hydroxide was calculated using Equation 1. S=1.54×10 ⁻¹⁵ ×6.02×10 ²³ ×V _n
/2.24×10 ⁴ ×W...Formula 1 Here, S is the specific surface area (unit: cm ² /g). V _n is a value determined by an experiment to measure the amount of gas adsorbed on the surface of magnesium hydroxide, and is the standard state of gas required to cover the surface of magnesium hydroxide with a monomolecular adsorption layer (273°K, 1 atm). ) in ^cm3 .
W is the weight (unit: g) of constant weight dry magnesium hydroxide used as a sample in the experiment to find V _n
It is. V _n was measured using an adsorption isotherm obtained by the method described below (the horizontal axis is the pressure of the adsorbed gas (unit: mmHg) when adsorption equilibrium is reached, and the vertical axis is the adsorption gas pressure when adsorption equilibrium is reached). Volume under standard conditions (unit:
cm ³ )) and found the point of lowest pressure in the straight line section, and considered that the monomolecular adsorption layer was completed at this point (``Measurement of Powder'' published by Sangyo Tosho in 1971, 135).
(based on pages 23 to 26), and the vertical axis value at this point is V _n . The experimental method for obtaining the adsorption isotherm is to first place a constant weight of dried magnesium hydroxide (preferably about 1 to 3 g) into a sample container with a constant capacity attached to a commonly made and used low-temperature gas adsorption device.
After removing the adsorbed gas from the atmosphere by heating the air to a temperature above ℃ for 20 minutes, the temperature is brought to -195℃, and the dry nitrogen used as the adsorption gas is heated to a pressure of 20℃.
Inject about mmHg to achieve adsorption equilibrium (until the mercury scale moves). Since the change in pressure before and after adsorption is thought to be due to adsorption of dry nitrogen on the surface of magnesium hydroxide, the volume of adsorbed gas is determined from Boyle's law and converted to the volume under standard conditions. Points are plotted with the horizontal axis representing the gas pressure when adsorption equilibrium is reached and the vertical axis representing the adsorption capacity (standard state) at that time. Repeat the above operation by increasing the inflow amount of adsorbed gas little by little (within a range of 400 mmHg or less) each time, and plot the points to obtain an adsorption isotherm. This operation for obtaining the adsorption isotherm was repeated four or more times to obtain each V _n , and the average value thereof was taken as the V _n used in Equation 1. Comparative Example 1 The various components shown in Table 1 were stirred for 5 minutes in a mixer, and then intensively kneaded and granulated using a twin-screw extruder (temperature: 260°C). The obtained composition was molded into the same test pieces as in Example 1 in the same manner as in Example 1, and evaluated. The results are shown in Table 1 as a comparative example of Example 1. This result shows that the rubbery ethylene-propylene random copolymer has an average dispersed particle size of 2
It was recognized that those having a μ or less have high bending strength and impact strength. Example 2 The various components shown in Table 2 were stirred in a mixer for 5 minutes, and then mixed with Brabender Plastograph PL-3S.
(manufactured by BRABENDER OHG DUISBURG) was used for intense kneading and granulation (temperature 260°C). The obtained composition was molded into the same test pieces as in Example 1 in the same manner as in Example 1, and evaluated. The results are shown in Table 2. Comparative Example 2 The various components shown in Table 2 were stirred in a mixer for 5 minutes, and then kneaded and granulated using a Blunder Plastograph PL-3S (temperature: 260°C). The obtained composition was molded into the same sample as in Example 1 in the same manner as in Example 1, and evaluated. The results are shown in Table 2 as a comparative example of Example 2. From this result, the composition of the present invention had an excellent quality balance of folding strength and impact resistance compared to the comparative example.

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Claims (1)

[Claims] 1 Homopolymer or copolymer of α-olefin
64.9 to 5% by weight, 35 to 75% by weight of magnesium hydroxide with a specific surface area of 25 m ² /g or less, and 0.1 to 20% by weight of rubbery ethylene-propylene random copolymer with an ethylene content of 45 to 85% by weight. A self-extinguishing resin composition, characterized in that the rubbery ethylene-propylene random copolymer is dispersed and blended so that the dispersed particle size is 2 μm or less on average.