JPS6154049B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has excellent mechanical strength, rigidity, and heat resistance,
The present invention also relates to thermoplastic resin compositions having highly flame retardant properties. Many methods of making thermoplastic resins flame retardant are known. For example, a resin composition in which an organic halogen compound and an antimony compound are blended with a thermoplastic resin is known. However, although this resin composition has a high degree of flame retardancy, it generates a large amount of smoke and toxic gas when burned. Additionally, there were other problems such as corrosion of the inside of the molding machine during molding and low mechanical strength of the molded product. Another method is to add a hydrous inorganic compound such as magnesium hydroxide, aluminum hydroxide, or hydrotalcite to the resin to make it flame retardant. The resin composition made flame retardant by this method has great features such as low smoke emission, non-toxic generated gas, and no molten drippings. requires a high concentration of water-containing inorganic compounds. For this reason, the mechanical strength of this resin composition was low, and the fluidity represented by the melt flow index was extremely reduced, so that it could not be put to practical use. The inventor of the present invention invented the thermoplastic resin composition of the present invention as a result of intensive research on thermoplastic resin compositions that have excellent mechanical strength, rigidity, heat resistance, and fluidity, and have a high degree of flame retardancy. That is, the present invention comprises (a) 30 to 60 weight percent of olefinic resin and (b)
Add (c) 0.001 to 5 parts by weight of a free radical generator to 100 parts by weight of a composition consisting of 70 to 40 weight percent of magnesium hydroxide surface-treated with 0.1 to 5 parts by weight of an organosilane compound to 100 parts by weight of magnesium hydroxide. It is a thermoplastic resin composition with excellent flame retardancy, which is characterized by being blended and heated and kneaded at a temperature higher than the melting point of the olefin resin. The present invention will be explained in detail below. The polyolefin resin used in the present invention is polyethylene, polypropylene, ethylene, or a copolymer of a propylene monomer and other monomers, preferably a polypropylene resin, and more preferably a crystalline ethylene-propylene copolymer. It is.
In other words, polypropylene resin has high mechanical strength,
It has rigidity, heat resistance, and an optimal balance of physical properties for making molded objects. This is because the crystalline ethylene-propylene copolymer has higher impact strength compared to homopolypropylene resin in the same melt flow index product, and maintains high impact strength even after being composited with magnesium hydroxide. In addition, homopolypropylene resin is mixed with a free radical generator,
When kneaded above the melting point, polymer chain scission takes priority and the physical properties do not improve much. However, in the case of crystalline ethylene-propylene copolymers, polymer chain scission and cross-linking reactions between polymer chains occur at a moderate rate. This provides a polyolefin-magnesium hydroxide composite with a high balance of mechanical strength and fluidity. Next, any type of magnesium hydroxide can be used in the present invention, but preferably 0.05
It is a fine powder with a size of μ to 10μ, and its shape is granular or plate-like. If the average particle diameter is smaller than 0.05μ, secondary aggregates are formed and remain as secondary aggregates when blended with the olefin resin, resulting in a significant decrease in the impact strength of the composition. Furthermore, since the concentration of magnesium hydroxide in the olefin resin becomes non-uniform, good results are not achieved in terms of flame retardancy. If the average particle size of magnesium hydroxide exceeds 10μ, the flame retardant effect will decrease when blended with polyolefin resin, impact strength will also decrease, surface gloss of the molded product will deteriorate, and the product image will deteriorate. Of course, other fillers, such as calcium carbonate, talc, silica, mica, glass fiber, etc., can also be blended into the polyolefin resin as long as flame retardancy, mechanical strength, etc. are not excessively reduced. Generally, organosilane compounds do not react with basic inorganic substances, and therefore, it is said that even if an organosilane compound-treated basic inorganic substance is blended with an olefin resin, no reinforcing effect is exhibited. However, as a result of intensive research by the present inventors, we found that magnesium hydroxide and organosilane compounds can form a strong bond, and when compounded with a free radical generator and combined with an olefin resin, the mechanical strength is greatly increased. found that it improved. The organosilane compound used in the present invention is preferably an organosilane compound having an ethylenically unsaturated group, and has the general formula shown by the following formula (1). (Xi) − _o Si(−Rj) _4-o (1) where n is an integer satisfying 1≦n≦3, and Xi is a hydration group such as a chloro group, ethoxy group, methoxy group, acetoxy group, and/or methoxyethoxy group. It is a group that can form a silanol group by decomposition, and Rj is a group having an ethylenically unsaturated bond such as a vinyl group or a gamma methacryloxypropyl group. The amount of organosilane compound required for surface treatment of magnesium hydroxide is 0.1 to 5 parts by weight per 100 parts by weight of magnesium hydroxide, and more preferably the amount is approximately expressed by the following formula (2). W=a×b×c×ρ(g) (2) where W is the amount of organosilane compound required
(g), a is the specific surface area of magnesium hydroxide (cm ² /g), b is the amount of magnesium hydroxide (g), and c is the organosilane compound that coated the magnesium hydroxide with a single layer. ρ is the density of the organosilane compound (g/cm ² ).
It is. In other words, the amount of organosilane compound is
When the amount is less than 0.1 part by weight, the surface of magnesium hydroxide is not uniformly coated, so the bonding strength with the olefin resin that becomes the matrix is weak, and mechanical strength, particularly tensile strength and impact strength, decrease. When the amount of the organosilane compound is more than 5 parts by weight, the bond with the olefin resin that becomes the matrix is weakened by the excess organosilane compound that is more than the amount reacted in a single layer, resulting in a decrease in mechanical strength, especially tensile strength and impact strength. . Furthermore, organosilane compounds are expensive, and their use in large quantities is disadvantageous in terms of cost. Various methods can be used to treat the surface of magnesium hydroxide with an organosilane compound, but any method that can form a single layer of an organosilane compound on the surface of magnesium hydroxide may be used. For example, there is a method of dissolving an organosilane compound in a solvent, adding magnesium hydroxide to the solution, treating the surface, and then evaporating the solvent to obtain surface-treated magnesium hydroxide. This method involves gradually dropping an organosilane compound while stirring at high speed in a mixing device to treat the surface. In addition, olefin resin, magnesium hydroxide, and organosilane compound are mixed simultaneously,
A method of heating and kneading at a temperature equal to or higher than the melting point of the olefin resin and surface treating it may also be used. Organosilane coupling agents suitable for the present invention include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(betamethoxyethoxy)silane, gammamethacryloxypropyltrimethoxysilane, gammamethacryloxypropyltris(betamethoxyethoxy)silane,
Examples include vinyltolylacetoxysilane. Free radical generators are added for two purposes. The first purpose is to ring-open the ethylenically unsaturated bond used in the surface treatment of magnesium hydroxide and chemically bond it to the olefinic resin, thereby improving mechanical properties, particularly tensile strength and impact strength. The second point is to improve fluidity by decomposing the olefin resin of the matrix and reducing its molecular weight. Among olefin resins, polypropylene resins are particularly susceptible to decomposition when attacked by free radicals, and are therefore suitable resins for the purpose of the present invention. Polypropylene resin is divided into various grades depending on the fluidity indicated by the melt flow index (MI). Looking at the relationship between melt flow index and impact strength for these series of grades, as the melt flow index increases, the impact strength decreases. However, when the above relationship was investigated for polypropylene resins decomposed using a free radical generator, it was surprisingly found that the impact strength was significantly higher than that of undecomposed polypropylene resins having the same MI. When polypropylene resin, which has a high original melt flow index, is used, the cutting shear stress during heating and kneading is low.
Moreover, since the impact strength of polypropylene resin is also low, the obtained composite has only a very low impact strength. The amount of free radical generator added varies depending on the amount of the organosilane compound, the type of olefin resin, the stabilizer treatment method, etc., but it is 0.001 parts by weight per 100 parts by weight of the olefin resin-magnesium hydroxide composition. ~5 parts by weight is preferred. If the amount of free radical generator is less than 0.001 part by weight, no chemical reaction occurs between the organosilane compound and the olefin resin, the mechanical properties of the composite, especially the tensile strength and impact strength, are low, and the decomposition of the olefin resin does not progress. , it is unsuitable because the fluidity cannot be improved. If the amount of the free radical generator is more than 5 parts by weight, the olefin resin will be significantly decomposed, and not only will the overall mechanical properties deteriorate, but also the thermal stability will deteriorate, making it impossible to put it to practical use. The 1-minute half-life temperature of the free radical generator is preferably within the range of 120 to 200°C. Generally, there is a relationship expressed by equation (3) between time (t) and the amount of decomposition (P percent) of the free radical generator. P=[1-(1/2) ^t/t0 ] _T=T0 ×100 (3) However, _t0 : Half-life time at temperature _T0 ℃ Therefore, the free radical generator is held for 3 minutes at the half-life temperature of 1 minute. 87.5% if held for 5 minutes, 97% if held for 5 minutes
The free radical generator decomposes. If the 1-minute half-life temperature of the free radical generator is lower than 120°C, most of the free radical generator will decompose before the olefin resin melts when heating and kneading the olefin resin and organosilane-treated magnesium hydroxide. reaction,
No decomposition occurs, mechanical strength and MI are both low.
It cannot be put to practical use. If the 1-minute half-life temperature is higher than 200°C, the number of free radicals generated is small under general kneading processing conditions, and the free radicals generated are stable, so the reaction and decomposition effects are small, and it cannot be put to practical use. Preferably, the free radical generator is an organic peroxide and contains an aromatic acyl group and/or an aromatic alkyl group. Aliphatic free radicals generally have weak hydrogen abstraction ability, and therefore reactions and decomposition are less likely to occur than organic peroxides containing aromatic acyl groups and/or aromatic alkyl groups, and they have poor mechanical properties and fluidity. Only low complexes are obtained. Free radical generators suitable for the present invention include 2,4-dichlorobenzoyl peroxide, m-toluoyl peroxide, benzoyl peroxide, α-
α'-bis-(t-butylperoxyisopropyl)benzene, dicumyl peroxide, t-butylcumyl peroxide, t-butylperoxybenzoate, di-t-butyldiperoxyisophthalate, 2.5- Dimethyl-2,5-di(benzoylperoxy)hexane and the like. A commonly used kneading device can be used to heat and knead a thermoplastic resin composition comprising an olefin resin, surface organosilane-treated magnesium hydroxide, and a free radical generator at a temperature equal to or higher than the melting point of the olefin resin. Examples of these heating kneading devices include a single screw extruder, a multi-screw extruder having two or more screws, a Banbury mixer, a roll kneader, an intensive mixer, a co-kneader, and a kneader-ruder. The heating kneading temperature may be at least the melting point of the olefin resin, but is determined by factors such as the decomposition temperature of the free radical generator and the melt viscosity of the olefin resin. Generally, it is within the range from the melting temperature of the olefin resin to the melting temperature +100°C. The composition ratio of magnesium hydroxide in the thermoplastic resin composition of the present invention is 40 to 70% by weight based on the olefin resin. When the magnesium hydroxide concentration is lower than this range, the flame retardant effect is low and the object of the present invention cannot be achieved. If the magnesium hydroxide concentration is higher than this range, the magnesium hydroxide cannot be uniformly dispersed and remains as a secondary aggregate, which deteriorates the mechanical properties of the composite and significantly lowers its fluidity, making it unusable for practical use. I don't get it. The thermoplastic resin composition of the present invention may contain stabilizers, plasticizers, lubricants, dispersants, crosslinking agents, dyes,
Pigments, antistatic agents and other additives can be added. The thermoplastic resin composition of the present invention can be processed by various molding methods such as extrusion molding, injection molding, compression molding, rolling molding, and rotational molding depending on the intended use and product shape. EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the scope of the present invention is not limited by the following Examples. Example 1 and Reference Example 1 γ-methacryloxypropyltrimethoxysilane (Nippon Unicar Co., Ltd., product name A-174) was dissolved in water adjusted to pH 3.5 to 4.0 to prepare a 0.5 weight percent solution. did. Magnesium hydroxide having an average particle diameter of 0.3 μm was weighed so that the silane coupling agent was 1% by weight based on the magnesium hydroxide, and was uniformly mixed with the silane coupling agent aqueous solution at room temperature. This mixture was dried for 5 hours in a constant temperature dryer kept at 130°C, and then pulverized in a hammer mill to obtain magnesium hydroxide whose surface was treated with a silane coupling agent. Add 0.2 parts by weight of t-butyl peroxybenzoate to 100 parts by weight of a mixture of 45% by weight of polypropylene shown in Table 1 and 55% by weight of magnesium hydroxide treated with a surface silane coupling agent, and stir for 10 minutes with a universal stirrer. After that, the capacity
200℃ 120 rotations using a 0.2 tabletop kneader
The mixture was kneaded for 10 minutes to obtain a resin composition. This resin composition was compression molded (conditions: temperature 210℃, pressure 25Kg/
cm ² , preheating time: 5 minutes, pressurization time: 5 minutes), prepare a sheet, cut out a test piece from this sheet,
Fluidity, mechanical properties and flammability were measured. For reference, we used magnesium hydroxide whose surface was not treated with a silane coupling agent, and
Example 1 for the case where no free radical generator is added
The physical properties of a resin composition manufactured under the same conditions as above were also measured. These results are summarized in Table 1. 1st
As can be seen from the table, the Examples have significantly improved fluidity, impact strength, and bending strength while maintaining combustibility compared to the Reference Examples. The physical properties were measured according to the method described below (note). (Note) Physical property measurement conditions Flammability: UL standard Subject94 Test piece thickness 3.18mm Melt flow index (MI): ASTM D-
1238 230℃ load 2160g Unit g/10mm Izot impact strength: ASTM D-256 No notch Unit Kg/cm/cm ² Bending property: ASTM D-790 Unit Kg/cm ²

[Table] Example 2 and Reference Example 2 Polypropylene MI=3, ethylene component content
A resin composition was obtained using the same composition and method as in Example 1, except that a 4.8% ethylene-propylene block copolymer was used and the substances shown in Table 2 were used as the organosilane compound, and the physical properties were measured. . The results are shown in Table 2. As can be seen from Table 2, when an organosilane compound that does not have an ethylenically unsaturated group in its molecule is used, both impact strength and bending strength are low and it cannot be put to practical use.

[Table] Example 3 and Reference Example 3 A resin composition was obtained using the same composition and method as in Example 1, except that the type and amount of the free radical generator were changed as shown in Table 3. The results of physical property measurements are shown in Table 3.
Those with a half-life temperature of 120 DEG C. to 200 DEG C. showed good physical properties, but aliphatic peroxides and those with a half-life temperature of 1 minute exceeding the above range showed only low physical property values. The amount of free radical generator added is the same as in Example 1.
The amount of active oxygen was set to be the same as the amount of active oxygen contained in the free radical generator.

【table】

Claims (1)

[Claims] 1. 70 to 40 parts by weight of magnesium hydroxide surface-treated with 0.1 to 5 parts by weight of an organosilane compound based on (a) 30 to 60 parts by weight of an olefinic resin and (b) 100 parts by weight of magnesium hydroxide. 0.001 to 5 parts by weight of (c) a free radical generator is added to 100 parts by weight of a composition consisting of 100 parts by weight of a composition with excellent flame retardancy, which is characterized in that it is heated and kneaded at a temperature equal to or higher than the melting point of the olefin resin. thermoplastic resin composition. 2. The thermoplastic resin composition according to claim 1, wherein the olefin resin is a polypropylene resin. 3. The thermoplastic resin composition according to claim 1, wherein the olefin resin is a crystalline ethylene-propylene copolymer and has an ethylene content of 0.5 to 30 percent by weight. 4. The thermoplastic resin composition according to claim 1, wherein the organosilane compound has an ethylenically unsaturated group. 5. The thermoplastic resin composition according to claim 1, wherein the free radical generator is an organic peroxide. 6 The 1-minute half-life temperature of the free radical generator is 120℃ or higher200
The thermoplastic resin composition according to claim 1, which has a temperature of 0.degree. C. or less. 7 Claim 1 in which the free radical generator contains an aromatic acyl group and/or an aromatic alkyl group
The thermoplastic resin composition described in .