JPH0534380B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention relates to polypropylene molded articles.
More specifically, the present invention relates to a polypropylene molded product that has excellent mechanical properties such as rigidity, temperature properties such as heat resistance, and high hardness. [Prior Art and Problems Therewith] In general, polypropylene has a light specific gravity and is excellent in rigidity, chemical resistance, moldability, etc., and is therefore widely used in the fields of containers, packaging materials, etc. However, it has the disadvantage of poor impact resistance at low temperatures. In order to improve this drawback, an improved method of copolymerizing with ethylene to introduce an ethylene component into the molecular chain, and an improved method of blending a rubber such as EPR with polypropylene are adopted. Propylene polymers and propylene polymer compositions obtained by such improved methods are widely used in the field of industrial materials such as automobile parts such as bumpers and home appliances. However, depending on the application, other properties may be important along with stiffness, chemical resistance, formability, and impact resistance at low temperatures, or these properties may be less important but other properties may be important. There are some things that must happen. For example, when excellent heat resistance and high hardness are required, propylene polymers or propylene polymer compositions are inferior to polystyrene and ABS resins. Therefore, propylene polymers or propylene polymer compositions cannot be used as materials for producing molded articles that require excellent heat resistance and high hardness. If a propylene polymer or a propylene polymer composition is to be used, it must be made into a thick molded article in order to satisfy the various properties mentioned above. This prevents the molded product from becoming thinner and increases the cost of the molded product. In other words, it is not possible to expand the uses of propylene polymers or propylene polymer compositions. If a propylene polymer or propylene polymer composition has excellent stiffness, chemical resistance, moldability, impact resistance at low temperatures, heat resistance, hardness, etc., such a propylene polymer or Propylene polymer compositions can be used as an alternative to polystyrene and ABS resins to expand their applications. In addition, since it is possible to finish a thin molded product, resource saving and cost reduction can be expected. [Object of the Invention] An object of the present invention is to provide a novel polypropylene molded product that has excellent mechanical properties such as rigidity and temperature properties such as heat resistance, and has high hardness. [Means for achieving the above object] The outline of this invention for achieving the above object is as follows:
(a) α- other than propylene as a monomer unit
Propylene homopolymer and/or propylene copolymer containing 2% by weight or less of olefin and having an intrinsic viscosity [η] of 0.9 to 4.0 dl/g 55 to
95% by weight, and (b) from 45 to 5% by weight of a propylene copolymer containing 15 to 80% by weight of α-olefin other than propylene as a monomer unit and having an intrinsic viscosity [η] of 2 to 10 dl/g. It is a molded product obtained by heat treating a molded product of a precursor composition, and is characterized by having a density of 0.902 g/cm ³ or more and a spin lattice relaxation time [T ₁ ] of 750 milliseconds or more. It is a polypropylene molded product. Briefly, this invention is a novel polypropylene molding having a specific density, a specific spin lattice relaxation time, a specific composition, etc. This precursor composition contains at least the components (a) and (b). The method for producing this precursor composition includes a method of kneading component (a) and component (b) that were produced separately;
Known methods include multi-stage polymerization methods such as two-stage polymerization methods and multi-stage polymerization methods. Among these, a two-stage polymerization method using a stereoregular catalyst is preferred. This two-stage polymerization method is carried out as follows. The stereoregular catalyst used for polymerization is a catalyst commonly used for stereoregular polymerization reactions of ethylene, propylene, etc., and is usually a catalyst prepared from at least a transition metal halide and an organoaluminum compound. . Here, the transition metal halide is preferably a titanium halide, such as titanium tetrachloride or titanium trichloride. Titanium trichloride is particularly suitable. As titanium trichloride,
titanium tetrachloride reduced by various methods; activated by further treatments such _as ball milling and/or solvent washing;
1/3 AlCl ₃ ) further co-pulverized with amines, ethers, esters, sulfur, halogen derivatives, organic or inorganic nitrogen compounds or phosphorus compounds; titanium trichloride liquefied in the presence of ether compounds. Those obtained by precipitation: Those obtained by the method described in Japanese Patent Publication No. 53-3356. Furthermore, a material in which a titanium halide is supported on a magnesium compound can also be used. The organoaluminum compound has the following formula:
_{AlR n} Compounds represented by are preferred. Specifically, for example, triethylaluminum, triisobutylaluminum, tri-n-propylaluminum, diethylaluminium monochloride, diethylaluminum monobromide, diethylaluminium monoiodide, diethylaluminum monoethoxide, diisobutylaluminum monoisobutoxide , diisobutylaluminum monohalide, diisobutylaluminum monohydride, ethylaluminum sesquichloride, ethylaluminum dichloride, etc. One or two of these
More than one species can be used. These catalyst components can usually be used in a mixed ratio of 1 to 100 moles of the organoaluminum compound to 1 mole of the transition metal halide. Alternatively, various electron-donating compounds may be used as the third component to improve catalyst performance. Such stereoregular catalysts can be used in commonly used amounts and combinations of components.
Used at each stage of the polymerization reaction. Known methods can be used as the polymerization method, such as slurry polymerization, solution polymerization, gas phase polymerization, and liquid phase polymerization using an α-olefin such as propylene or ethylene as a medium. When producing the precursor composition in which ethylene is selected as an α-olefin other than propylene by a two-stage polymerization method, in the first stage, a propylene homopolymer is produced in which the content of ethylene units in the polymer is 2% by weight or less. and/or propylene-ethylene copolymer at 55 to 95% by weight of the total polymer;
It is preferably managed to produce 60 to 92% by weight. If a propylene-ethylene copolymer containing more than 2% by weight of ethylene units is used in this first stage, the stiffness of the resulting composition will be significantly reduced, which is unsuitable. In the second stage, ethylene or ethylene and propylene are newly supplied into the reactor in which the propylene homopolymer and/or propylene-ethylene copolymer obtained in the first stage polymerization reaction is present, By setting the inside of the reactor to predetermined polymerization conditions, the second stage polymerization reaction is caused, and the content of ethylene units is 15 to 80% by weight, preferably 20% by weight.
Propylene-ethylene copolymer, which is 70% by weight, is controlled to form 5 to 45%, preferably 8 to 40% by weight of the total polymer. As a result, a precursor composition according to the present invention is obtained. In this invention, as α-olefins other than propylene, in addition to the above-mentioned ethylene, linear monoolefins such as butene-1, hexene-1, octene-1, etc., branched monoolefins such as 4-methyl-pentene-1, butadiene Dienes such as ethylene can also be used in the same manner as ethylene. In order to obtain a precursor composition with preferable physical properties,
Other olefins include ethylene, butene-1
is preferred. What is important in this invention is that the content of α-olefin other than propylene as a monomer unit in the component (a) is 2% by weight or less,
The intrinsic viscosity [η] is 0.9 to 4.0 dl/g, preferably 1.0 to 3.5 dl/g, and the blending ratio in the precursor composition is 55 to 95% by weight, preferably 60 to 92% by weight.
In addition, in the component (b), the content of α-olefin other than propylene as a monomer unit is 15 to 80% by weight, preferably
20 to 70% by weight, and the intrinsic viscosity [η] is 2 to 10
dl/g, preferably 2.5 to 8 dl/g,
The blending ratio in the precursor composition is 45 to 5% by weight, preferably 40 to 8% by weight. Here, when the content of the α-olefin in the component (a) is more than 2% by weight, rigidity, heat resistance, hardness, etc. are reduced. The intrinsic viscosity [η] of the component (a) is 0.9 dl/
If it is smaller than g, the impact resistance of the polypropylene molded product will decrease, and the intrinsic viscosity [η] will be 4.0 dl/g.
If it is larger than , its rigidity and heat resistance will decrease. Furthermore, if the proportion of the component (a) in the precursor composition is less than 55% by weight, when the precursor composition is made into a molded article, the rigidity and heat resistance of the molded article may be reduced. If the proportion of component (a) is more than 95% by weight, the impact resistance of the polypropylene molded product will decrease. If the content of α-olefin other than propylene as a monomer unit in the component (b) is outside the above range, the impact resistance of the polypropylene molded product will decrease. In addition, the intrinsic viscosity [η] of the component (b) is 2
If it is smaller than dl/g, the impact resistance of the polypropylene molded product will decrease, and the intrinsic viscosity [η] will be 10 dl/g.
If it is larger than g, its rigidity and heat resistance will be insufficient. Here, the limiting viscosity [η] can be expressed as a value measured in tetralin heated to 135°C. Note that this precursor composition may contain an inorganic filler within a range that does not impede the object of the present invention. Examples of the inorganic filler include carbonates such as calcium carbonate, magnesium carbonate, and dolomite; sulfates such as calcium sulfate and magnesium sulfate; sulfites such as calcium sulfite; talc;
Clay, mica, asbestos, glass fiber, glass beads, silicates such as calcium silicate, montmorillonite, and bentonite, metal powders such as iron, zinc, and aluminum, ceramics such as silicon carbide, silicon titanide, and their whiskers and carbon. Examples include black, graphite, carbon fiber, etc., and these inorganic fillers may be used alone or in combination with two
It is possible to use a mixture of more than one kind of the above-mentioned inorganic fillers. Among the various inorganic fillers, carbonates, sulfates, silicates, and metal powders are preferred, and calcium carbonate, barium sulfate, talc, mica, and zinc powder are particularly preferred. The calcium carbonate and barium sulfate improve the surface smoothness and gloss of the molded product, and can also improve the heat resistance and abrasion resistance of the molded product. The inorganic filler may be in the form of particles, plates, or fibers, but the particle size is 0.2 to
Preferably it will be in the range of 20 μm. Furthermore, within a range that does not impede the object of the present invention, the precursor composition may include an antistatic agent, a coloring agent,
Various additives such as flame retardants, antioxidants, ultraviolet absorbers, plasticizers, and heat stabilizers may be added. Next, other important matters in this invention are that this polypropylene molded product has the same properties as the precursor composition [the content of α-olefin other than propylene,
In addition, it has a density of 0.902 g/cm ³ or more, preferably 0.905 to 0.922 g/cm ³ , and a spin-lattice relaxation time [T ₁ ] is 750 milliseconds or more, preferably
It must be at least 770 milliseconds. When the density is less than 0.902 g/cm ³ , the polypropylene molding causes a decrease in the stiffness, heat resistance and hardness of the molding, and when the spin lattice relaxation time [T ₁ ] is less than 750 milliseconds, Decrease the rigidity, heat resistance and hardness of polypropylene moldings. Here, the density is determined using an Izotsu impact measurement piece (injection molded product) specified in JIS K7110,
It can be measured in accordance with the underwater displacement method in JIS K7112. The spin-lattice relaxation time [T ₁ ] is determined from pulsed nuclear magnetic resonance spectroscopy for the crystalline components of a polymer, and is an index of the molecular mobility of _the crystalline components of the polymer. is rated as high. The method for measuring this spin-lattice relaxation time [T ₁ ] is as follows:
Written by Abragam (translated by Kazuhisa Tomita and Motoyuki Tanaka), “Nuclear Magnetism (Part 1)” (published by Yoshioka Shoten on July 15, 1967)
It complies with the following. The measurement conditions for this spin-lattice relaxation time [T ₁ ] are: ¹ H: 90.13 MHz, temperature: 30° C., pulse: 180°−τ−90°, repetition time: 7 seconds, cumulative time: 100 times or more. Incidentally, [T ₁ ] of a propylene homopolymer with [η] of about 1.6 to 1.7 dl/g is 720 to 725 milliseconds. A polypropylene molded product having such limiting conditions for density and spin lattice relaxation time [T ₁ ] is a molded product of the precursor composition, preferably having a melting point of 160 to 165°C and a density of 0.880 to 0.902.
g/cm ³ and the spin lattice relaxation time [T ₁ ] is 690
The molded product of the precursor composition having a molecular weight of 155 to 740
It can be easily produced by heat treatment at 170°C, particularly 158 to 168°C, and further within a temperature range of ±4°C of the melting point of the molded product of the precursor composition. If the heating temperature is outside the above range, a polypropylene molded product having the desired density [d] and spin lattice relaxation time [T ₁ ] cannot be obtained. In that sense, the heating temperature range can be truly said to be a critical condition. The heat treatment may be carried out under an atmosphere that does not substantially promote the deterioration or decomposition of the precursor composition, the molded product of the precursor composition, the polypropylene molded product, or the constituent components thereof. There is no limitation, and various methods can be adopted. Examples of heat treatment methods include, for example, heating in a mold held at the above temperature range, contacting the roll surface or hot plate surface held at the above temperature range, and heating with nitrogen, argon, or air in the above temperature range. Examples include a method in which the precursor composition or a molded product thereof is placed or immersed in a gas such as, silicone oil, or an inert liquid such as water. As a method for heating these, electric heaters, hot soot oil, steam, etc. are generally used, but the method is not limited thereto. , silicon nitride, metal oxides, organic substances having reactive functional groups such as carboxylic acid groups, hydroxyl groups, amino groups, oligomers, etc. are added to the precursor composition, and the precursor composition or molded product thereof is prepared. A method of high frequency heating can be adopted. This high-frequency heating treatment is excellent in that it can significantly shorten the heat treatment time. A heat treatment time of 1 second or more is sufficient, but if a molded article of the precursor composition is heat treated, a time of up to 60 minutes is usually sufficient in consideration of thermal deterioration. The precursor composition may be molded by injection molding,
Any method such as a film molding method, a blow molding method, an extrusion molding method, or a compression molding method may be used. By this heat treatment, the intrinsic viscosity of the polymer constituting the precursor composition does not change, but the melting point, density, and spin lattice relaxation time [T ₁ ] of the precursor composition change, and the present invention Such a polypropylene molded article is obtained. Increases in these parameters are indicative of improved crystallinity of the polymeric components in the precursor composition. This is supported by the experimental results described below, which show that rigidity, heat resistance, hardness, impact resistance, etc. are improved as a result of improved crystallinity. [Effects of the Invention] According to the present invention, due to improved crystallinity, it has excellent rigidity and heat resistance, and has high hardness.
It is possible to provide a novel polypropylene molded product that has excellent mechanical properties such as impact resistance, creep properties, fatigue properties, and wear resistance, and temperature properties such as dimensional stability at high temperatures. [Example] (Comparative Examples 2, 4, 6, 8) Test results of molded products of precursor compositions (melting point 161 to 162°C) having predetermined physical property values manufactured by a two-stage polymerization method are shown in Table 1. show. The physical properties were measured in accordance with the following JIS standards. Flexural modulus: JIS K7203 Izot impact strength: JIS K7110, temperature 23°C Heat distortion temperature: JIS K7207 Load 4.6 Kg/cm ² Rockwell hardness: JIS K7202 (Examples 1 to 4, Comparative Examples 1, 3, 5, 7) ) Molded products of the precursor compositions of Comparative Examples 2, 4, 6, and 8 (melting point 161 to 162°C) were immersed in silicone oil,
Table 1 shows the results of heat treatment under predetermined conditions.

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Claims (1)

[Claims] 1 (a) A propylene homopolymer and/or propylene copolymer containing 2% by weight or less of α-olefin other than propylene as a monomer unit and having an intrinsic viscosity [η] of 0.9 to 4.0 dl/g.
55 to 95% by weight, and (b) contains 15 to 80% by weight of α-olefin other than propylene as a monomer unit, and has an intrinsic viscosity [η] of 2 to 10 dl/
obtained by heat treating a molded product of a precursor composition consisting of 45 to 5% by weight of a propylene copolymer, which has a density of 0.902 g/cm ² or more and a spin lattice relaxation time [T ₁ ] of 750 A polypropylene molded product characterized by a millisecond or more.