JPH0452291B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polypropylene compositions for injection molding. More specifically, the present invention relates to a polypropylene composition for injection molding that has excellent impact resistance, rigidity, and melt flowability, and has an excellent appearance even when colored with a pigment. Crystalline polypropylene has excellent properties in terms of rigidity, heat resistance, gloss, etc., but when used alone, it has the disadvantage of poor impact strength and paintability.
Therefore, at present, its use in fields where impact strength is required or where painting is required is extremely limited. Many methods have been proposed in the past for the purpose of improving these drawbacks by mixing crystalline polypropylene with rubber-like substances such as polyethylene, polyisobutylene, polybutadiene, and ethylene-propylene rubber. However, when high-molecular-weight rubbery substances are added to improve impact resistance, the melt viscosity of the composition increases and moldability, especially injection moldability, decreases. Just as it has been said that if a low molecular weight rubbery substance is added to prevent the impact resistance from increasing, the impact resistance of the composition will not be sufficiently improved. At present, it is difficult to obtain a polypropylene composition with a good balance between properties and moldability. Recently, attempts have been made to use crystalline polypropylene compositions to make large parts such as automobile bumpers, grills, and trims into resins, and there is an increasing trend toward colorization in these applications. For such large parts, moldability is particularly important, so efforts are made to lower the viscosity of the composition, that is, to increase the melt flow rate (MFR). When molding, especially when coloring is done using the master batch method, unexpectedly there are many cases in which streaks or the like appear on the surface of the molded product due to color separation, which may reduce the product value. In view of this situation, the present inventors have developed impact resistance,
As a result of various studies aimed at creating a polypropylene composition for injection molding that has excellent rigidity and melt flowability, and has an excellent appearance even when colored with pigments, etc., we have found that a polypropylene composition having a specific melt flowability index can achieve the above The inventors have discovered that the object can be achieved and have completed the present invention. That is, the present invention provides (A) polypropylene with an isotactic index of 89 or more and a melt flow rate of 20 to 150 g/10 min: 70 to 90% by weight, (B) ethylene/α-olefin with an ethylene content of 35 to 85 mol%. Random copolymer: 10-30
and (C) polyethylene with an intrinsic viscosity [η] of 2.0 to 6.8 dl/g: 3 to 20% by weight, and the melt flow rate of the composition is 3.
or 50g/10min and melt fluidity index N is 2.8
The present invention provides a polypropylene composition for injection molding that is well-balanced in impact resistance, rigidity, melt flowability, appearance, etc. and is characterized by the following characteristics: In the polypropylene composition for injection molding of the present invention, component A has an isotactic index of 89 or more and a melt flow rate (MFR: ASTM D
1238L) is 20 to 150g/10min, preferably 40
to 100g/10min of polypropylene. The isotactic index (ITP) in the present invention is A.
Macromolecules 6 , 925 by Zambelli et al.
(1973) is the isotactic fraction of methyl groups in triad units according to the ¹³ C-NMR method. Regarding polypropylene random copolymer, A.
It can be determined according to the method of Zambelli et al. The polypropylene is a propylene homopolymer or a copolymer of propylene containing 95 mol % or more of propylene and ethylene and/or other α-olefins. For those with ITP less than 89,
Only compositions with low rigidity can be obtained, and MFR is low.
If less than 20g/10min is used, the MFR of the composition described below will be low and the moldability will be poor;
If you use a material that exceeds 150g/10min, the N value will be 2.8.
The appearance of the molded product is poor. And component A is
70 to 90% by weight in the composition of the invention, preferably
It accounts for 70 to 80% by weight, more preferably 70 to 77% by weight. Component B has an ethylene content of 35 to 85 mol%;
It is preferably a 45 to 85 mol% ethylene/α-olefin random copolymer, and preferably has an intrinsic viscosity [η] of 2.0 in decalin solvent at 135°C.
or 9.0 dl/g, especially 2.5 or 5.0 dl/g
g. It is a low-crystalline or amorphous copolymer with a crystallinity of usually 10% or less, especially 5% or less when measured by X-rays. The α-olefin copolymerized with ethylene is usually an α-olefin having 3 to 10 carbon atoms, and specifically, for example, propylene, 1-
Examples include butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene. If the ethylene content is outside the above range, there is no impact resistance improvement effect. Also, [η] is 9.0dl/g
If it exceeds 2.8, the MFR of the composition may decrease or the N value may exceed 2.8, which may result in poor moldability or poor appearance. On the other hand, when [η] is less than 2.0 dl/g, the effect of improving impact resistance tends to be somewhat low. Note that those with a crystallinity of more than 10% tend to be somewhat inferior in impact resistance improvement effect. and component B is 10 to 30% by weight, preferably 10 to 30% by weight, more preferably 15% by weight in the composition of the present invention.
or 25% by weight. The amount of component B is 10% by weight
If it is less than 30% by weight, the effect of improving impact strength is small.
Anything exceeding this results in insufficient rigidity, especially in a high-temperature atmosphere, and poor surface hardness. Component C has an extreme clay [η] of 2.0 to 6.8 dl/
g, preferably in the range of 3.0 to 6.0 dl/g. [η] is a value measured in decalin solvent at 135°C. Furthermore, polyethylene as used in the present invention is not only an ethylene homopolymer, but also a highly crystalline copolymer of ethylene and other α-olefins with an ethylene content of 93 mol% or more, preferably 97 mol% or more. It is a chemical polymer. [η] is
If it is less than 2.0 dl/g, there is no impact resistance improvement effect, while if [η] is more than 6.8 dl/g,
Since the MFR of the composition described below decreases or the N value exceeds 2.8, the moldability decreases and the appearance becomes inferior. The amount of component (C) in the composition of the present invention is 3 to 20% by weight, preferably 5 to 15% by weight. Although a composition with sufficient impact resistance can be obtained without adding component (C), adding 3% by weight or more results in a good balance between impact resistance and rigidity.
On the other hand, if it exceeds 20% by weight, the heat-resistant rigidity is insufficient, although it is not as good as component (B). The amount of each component in the present invention is based on the total amount of (A), (B) and (C) as 100% by weight. The polypropylene composition for injection molding of the present invention consists of the above (A), (B) and (C), and the MFR of the composition is
is 3 to 50g/10min, preferably 7 to 50g/10min.
20g/10min and melt fluidity index N 2.8 or less,
Preferably it is in the range of 2.6 to 2.0. MFR
Compositions with a molding rate of less than 3 g/10 min have poor moldability, and the molding cycle will be significantly increased, especially when molding a large molded product. On the other hand, those exceeding 50g/10min have poor mechanical strength. Compositions with an N value of more than 2.8 have poor appearance of molded articles. There is no particular limitation as long as the N value is 2.8 or less, but if it is less than 2.0, the melt fluidity is greatly reduced, and flow marks may be formed on the surface of the molded product, resulting in poor appearance. The melt fluidity index N in the present invention refers to the shear rate: 10 ⁴ sec ^-1 and shear rate: of the flow curve expressed by shear rate (log ₁₀ D) and shear stress (log ₁₀ τ).
It is the slope between 10 ³ sec ^-1 and is expressed by the formula (). N=log ₁₀ 10 ⁴ −log ₁₀ 10 ³ /log ₁₀ τ(1)−log _1
0 τ(2)=1/log ₁₀ τ(1)−log ₁₀ τ(2)() The above N value was determined using a capillary rheometer manufactured by Shimadzu Corporation, nozzle: 1.0 mmφ, L/D:
30. This value was determined by measuring the melt flow curve at a measurement temperature of 230°C. The polypropylene composition for injection molding of the present invention is
A method of mechanically mixing each component that has been polymerized separately in advance, or a method of sequentially manufacturing each component by polymerizing olefins in the presence of a stereoregular catalyst in a single polymerization reaction system. or a combination of these methods. When preparing the composition of the present invention by mechanically mixing each component, it is necessary to take sufficient care to avoid poor dispersion of each component. Examples of the melt kneader used for mixing include a Banbury mixer, a kneader, a twin screw extruder, and a single screw extruder. Polymerizing olefins in one polymerization reaction system means that components A,
This means that a polymer mixture is produced by sequentially producing components A, B, and C, and the catalyst is usually not deactivated during the production of components A, B, and C. As the stereoregular catalyst used in the production of each component of the polypropylene composition for injection molding of the present invention, a catalyst normally used in the production of crystalline polypropylene is used. A typical example is a transition metal catalyst component such as a supported transition metal component in which titanium trichloride or a transition metal compound is supported on a carrier, and an alkyl aluminum compound or its halogen compound, hydride, or alkoxide. This is a two-component catalyst system, or a three-component catalyst system in which an organic compound containing nitrogen, phosphorus, sulfur, oxygen, silicon, boron, etc. is added to this catalyst system. Furthermore, as the ethylene/α-olefin random copolymer and polyethylene, which are components B and C in the present invention, those polymerized using a known Ziegler catalyst can also be used. When producing the polypropylene composition for injection molding of the present invention, antioxidants, ultraviolet absorbers, lubricants, nucleating agents, antistatic agents, flame retardants, pigments, dyes, inorganic or organic fillers are added at any stage of its preparation. Various additives such as additives can be blended within a range that does not impair the purpose of the present invention. Specific examples of the pigment include organic pigments such as cyanine blue, cyanine green, perylene, and quinacridone, and inorganic pigments such as titanium oxide and carbon black. Specific examples of the filler include calcium carbonate, talc, mica, clay, magnesium hydroxide, glass fiber, potassium titanate fiber, and carbon fiber. Furthermore, when coloring the polypropylene composition for injection molding of the present invention by the masterbatch method, the masterbatch usually has a color density of 10 to 10.
A range of 50 times is used, preferably a range of 25 to 35 times. The pigment used in the masterbatch is 1
The color is not limited to the species, and if necessary, two or more pigments may be used to adjust the color to a desired color. The resin serving as the base of the masterbatch is not particularly limited as long as it is an olefin resin, but polypropylene resins are preferred because they are excellently dispersed in the polypropylene composition for injection molding of the present invention. The polypropylene composition for injection molding of the present invention is
It has excellent moldability, and the molded products obtained also have excellent low-temperature impact resistance, rigidity, and surface hardness.In addition, the appearance, especially when colored with pigments, especially when colored by the master batch method, also shows no color separation phenomenon. Because it does not cause any problems and has an excellent appearance, it is particularly suitable for use not only in household goods and appliance parts, but also in large automobile parts such as bumpers, spoilers, instrument panels, grills, and trims. can. Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded. Example 1 ITP: 97 and MFR: 60 g/10 min, polypropylene component (hereinafter abbreviated as component A) 73% by weight, ethylene content: 50 mol%, [η]:
Ethylene-propylene random copolymer component (hereinafter referred to as
component B-) 20% by weight, and [η]:
A polyethylene component (hereinafter abbreviated as C-) of 5.2 dl/g and 7% by weight of a polyethylene component (hereinafter abbreviated as C-) was used to sequentially produce A, B and C components in a plurality of reactors to obtain a polymer. Next, a heat-resistant stabilizer, a weather-resistant stabilizer, and a rust preventive agent were mixed with the polymer, and the mixture was granulated using a twin-screw extruder to obtain a composition. The melt flow index N of the composition was 2.6. In addition, compositions, compositions, compositions, compositions, and compositions were obtained by changing only the polymerization conditions of component A--. Each melt fluidity index N
were 2.2, 2.4, 2.7, 2.9 and 3.2. Carbon black 10.5% by weight, titanium oxide 12.0%
Mix 30 parts by weight of the above composition to 1 part by weight of a master batch consisting of 4.5% by weight of iron oxide (), 62% by weight of polypropylene (MFR: 25g/10min), and 9.0% by weight of metal stearate. Then, the bumper was made by injection molding into Toshiba IS-
Molded with 1250N (Toshiba Machine Co., Ltd.). The conditions at that time were as follows. Resin temperature: 225℃ Injection pressure (primary): 100Kg/cm ² (secondary): 70Kg/cm ² Screw back pressure: 20Kg/cm ² Molding time: 85sec/cycle Screw shape: Slow compression full flight,
L/D=20 Product weight: 2300g The obtained molded product was examined for color separation. The results are shown in Table 1. The degree of color separation was determined by visually observing the appearance of the bumper surface and using the following criteria. ◎: No visible abnormalities such as streaks ○: Slight abnormalities such as streaks, but hardly noticeable △: Slight abnormalities such as streaks ×: No visible abnormalities such as streaks For the composition ~, a test piece was prepared using an injection molding machine (SJ45-C manufactured by Meiki Seisakusho Co., Ltd., mold clamping force 150 tons) at a resin temperature of 200℃, and the following physical properties were obtained. We conducted an evaluation. The results are shown in Table 1. MFR (g/10min): ASTM D1238L Flexural modulus (Kg/cm ² ): ASTM D790 Izot impact value, -30℃ (Kg・cm/cm):
ASTM D256

[Table] Example 2 ITP instead of component A- used in Example 1:
97 and MFR: 150g/10min polypropylene component (component A--) 79% by weight, ethylene content instead of component B-: 55 mol%, [η]:
A composition consisting of 12% by weight of an ethylene-propylene random copolymer (component B-) of 2.4 dl/g and 9% by weight of a polyethylene component (component C-) of 3.2 dl/g [η] instead of component C-. I got it. Further, compositions and compositions were obtained by changing the polymerization conditions of component A--. The respective melt fluidity indexes N were 2.6, 2.9 and 3.3. The above composition is based on 1 part by weight of a master batch consisting of 3.0% by weight of carbon black, 15.0% by weight of phthalocyanine blue, 3.0% by weight of iron oxide (), 15% by weight of metal stearate, and 64% by weight of polypropylene (MFR: 45 g/10 min). composition,
After mixing 30 parts by weight, a large trim was molded using an injection molding machine (Ube MAX1800). The conditions at that time were as follows. Resin temperature: 218℃ Injection pressure (primary): 110Kg/cm ² (secondary): 75Kg/cm ² Screw back pressure: 22Kg/cm ² Molding time: 93sec/cycle Screw shape: Slow compression Dalmage,
L/D=20 Product weight: 1560g Average wall thickness: 1.8mm The obtained molded product was examined for color separation. The criteria for determining color separation are the same as in Example 1. In addition, test pieces were prepared using the same procedure as in Example 1 for compositions ~, and physical properties were evaluated. The above results are shown in Table 2.

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Claims (1)

[Scope of Claims] 1 (A) Polypropylene with an isotactic index of 89 or more and a melt flow rate of 20 to 150 g/10 min: 70 to 90% by weight, (B) Ethylene α with an ethylene content of 35 to 85 mol% - Olefin random copolymer: 10 to 30% by weight, and (C) polyethylene having an intrinsic viscosity [η] of 2.0 to 6.8 dl/g: 3 to 20% by weight, and the melt flow rate of the composition is 3.
or 50g/10min and melt fluidity index N is 2.8
A polypropylene composition for injection molding, characterized in that: