JPH0224860B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention consists of a specific propylene polymer resin, a composition in which a synthetic rubber is blended into this, and a resin composition in which a specific talc and a specific carbon black are blended.
This invention relates to an injection molded article that has heat resistance, mechanical properties, and dramatically improved electrical conductivity. It is known to obtain a conductive resin by blending carbon black with a thermoplastic resin, and conductive resin compositions containing carbon black have also been studied for polypropylene and have been put into practical use in some cases. However, conventional injection molded polypropylene products containing carbon black have the major disadvantage of extremely poor dimensional accuracy and the occurrence of sink marks and warpage. Since it is necessary to incorporate carbon black with a large specific surface area, there are drawbacks such as poor mechanical properties and moldability, which poses a major problem in that the range of application is extremely limited. In light of this problem, the inventors of the present invention have conducted intensive studies and found that a resin composition is prepared by blending talc with a specific particle size and a specific carbon black into a composition that includes a specific propylene polymer and, in some cases, synthetic rubber. By using these materials, the dimensional accuracy is extremely good, and the heat resistance, mechanical properties, and moldability are excellent.
The present invention was completed based on the discovery that an injection molded article with dramatically improved conductivity can be obtained. That is, the present invention is made by blending the following components (a) to (c), and the components (a) and (b) are each 25% on the basis of (a) + (b).
~90% by weight and 75~10% by weight, and (c) component (a)
A conductive injection molded article comprising a composition containing 2 to 100 parts by weight based on 100 parts by weight of +(b) and having a molding shrinkage rate of 0.6% or less. (a) A composition comprising a propylene polymer resin, optionally blended with synthetic rubber, (1) Extractable content in xylene at 23°C is 10 to 50% by weight
(2) The propylene content in the extracted soluble matter is 30% by weight or more; (b) The average particle size measured by the light transmission method of the liquid phase sedimentation method is
Talc (c) Super Conductive Furness (S.
CF), conductive furnace (CF), and extra conductive furnace (XCF).Thus, the molded article of the present invention has excellent dimensional accuracy,
It has a high degree of conductivity, and has excellent heat resistance, rigidity, impact resistance, moldability, etc., and as a result of having a high degree of conductivity, it has extremely good electromagnetic wave shielding properties. The molded article of the present invention having such characteristics is extremely suitable for the housing field of electronic equipment and office equipment that needs to avoid electromagnetic interference, the field of electrostatic protection materials for ICs, etc. It is suitable for a wide range of fields such as containers, thin film batteries, and surface heating elements. Component (a) used in the present invention is a composition comprising a propylene polymer resin polymerized using a Ziegler-Natsuta type catalyst, and optionally a synthetic rubber blended with this, and (1) 23℃ xylene polymerization. The soluble content is 10 to 50% by weight, and (2) the propylene content in the extracted soluble content is 30% by weight or more. Here, as the propylene polymer resin, a propylene homopolymer or a crystalline copolymer resin of propylene and an α-olefin other than propylene (including ethylene) is suitable. Preferably, the α-olefin has 2 to 12 carbon atoms other than propylene. If the xylene extractable content is less than 10% by weight, the molding shrinkage rate during injection molding will increase and dimensional accuracy will deteriorate, while if it exceeds 50% by weight, sink marks and warpage will be noticeable and dimensional accuracy will deteriorate. This is not preferable because the conductivity also decreases. Furthermore, if the propylene content in the xylene-extractable matter is less than 30% by weight, sink marks and warpage will become noticeable and dimensional accuracy will deteriorate. The majority of the constituent units of the crystalline propylene copolymer resin are propylene, and specifically, for example, crystalline propylene/ethylene block or random copolymer, crystalline propylene/butene block or random copolymer, crystalline propylene・
Hexene block or random copolymer, crystalline propylene/heptene block or random copolymer, crystalline propylene/ethylene/butene copolymer, etc., especially crystalline propylene/ethylene block copolymer with an ethylene content of 30% by weight or less. Combination is preferred. Such propylene polymer resins can be appropriately selected from commercially available ones. Furthermore, the synthetic rubber used in the present invention includes:
Examples include ethylene/propylene copolymer rubber (EPM, EPDM), styrene/butadiene copolymer rubber (SBR, SBS block copolymer), hydrogenated products thereof, isoprene rubber, isoprene/isoptylene rubber, etc. . Among these, ethylene/propylene copolymer rubber is preferred. As a combination composition, a composition consisting of a crystalline propylene/ethylene block copolymer and an ethylene/propylene copolymer rubber is particularly preferred from the viewpoint of quality balance. The xylene soluble content at 23°C is measured by placing 3 g of the sample in 1000 ml of boiling xylene, allowing it to cool to 23°C, filtering it, separating the soluble content, and measuring its weight. . In addition, the measurement of the propylene content in this extracted soluble matter is carried out after separating the xylene in the extracted soluble matter.
The extract is detected using an infrared spectrophotometer. Next, the talc which can be used in the present invention and is the component (b) has an average particle size of 0.5 to 20μ. If the average particle size of talc is less than 0.5 μm, the dispersion in the composition tends to be non-uniform, resulting in a decrease in impact resistance and rigidity, which is undesirable. On the other hand, if it exceeds 20 μm, impact resistance deteriorates, which is undesirable. Preferred talc has an average particle size of 0.5-5μ and 10μ
The content of the above coarse particles is 10% by weight or less, and the specific surface area is 15000 cm ² /g or more. The particle size distribution of talc mentioned here is measured by a light transmission method using a liquid phase sedimentation method. Measurement devices include the CP type manufactured by Shimadzu Corporation. The average particle size is the particle size at the 50% point on the particle size distribution integral curve. Further, the specific surface area is measured using a constant pressure aeration type specific surface area measuring device, such as powder specific surface area measuring device SS-100 manufactured by Shimadzu Corporation, based on the so-called air permeation method, which is a conventional method. This kind of talc is made by crushing naturally produced talc (hydrous magnesium silicate) into a fine powder, and in particular, it is made by grinding talc from China, which contains less than 0.9% by weight of iron and aluminum as impurities. The product obtained by pulverization and classification is good. The talc used in the present invention may be used without surface treatment, but it may also be surface treated with various surface treatment agents. Surface treatment agents include waxes such as low molecular weight polyethylene and low molecular weight polypropylene, saturated higher fatty acids such as stearic acid and palmitic acid, saturated higher fatty acid metal salts such as magnesium stearate, unsaturated higher fatty acids such as oleic acid, and oleic acid. Unsaturated higher fatty acid metal salts such as magnesium, titanate coupling agents such as isopropyl triisostearic titanate, silane coupling agents, various surfactants such as polyoxyethylene alkyl ether, etc. can be used. Furthermore, the carbon black used in the present invention is
SCF (Super Conductive) with a large specific surface area
Furnace), CF (Conductive Furnace) and X.
It is at least one kind selected from CF (Extra Conductive Furnace), and these are advantageous in that a high degree of conductivity can be obtained with a small amount of blending. These can be selected and used from commercially available products.
For example, the SCF is "Vulcan" manufactured by Cabot.
``SC'' and ``Vulcan P'' are the same as CF, and ``Vulcan C'' is representative, while AKZO's ``Ketschen Blak'' and Cobot's ``Vulcan XC-72'' and ``CSX-99'' are typical examples of XCF. It is. Among them, those with a specific surface area of 850 m ² /g or more, especially 900 m 2 /g or more.
Carbon black of m ² /g or more is particularly preferred since it can provide a high degree of conductivity with a very small amount. In particular, XCF's "Butt Emblem" is excellent. The carbon black used in the present invention is different from the carbon black used for coloring and filling, which has extremely poor conductivity due to its amorphous structure. A highly conductive furnace black is selectively used. Incidentally, a conductive composite carbon black obtained by blending other carbon blacks such as channel black and acetylene black with the specific furnace black in a specific weight ratio range can also be used as an embodiment of the present invention. The present invention uses the above-mentioned components (a), (b) and (c), and their blending ratios are (a)
25 to 90% by weight based on (a) + (b), and 75 to 90% by weight based on (b)
10% by weight, 2 to 100 parts by weight of (c) to 100 parts by weight of (a) + (b)
A range of parts by weight is preferred. If the amount of component (b) talc is less than the above range, there will be no improvement in dimensional accuracy or conductivity, and if it exceeds the above range, mechanical properties may deteriorate. If the amount of carbon black, which is component (c), is less than the above range, the electrical conductivity will be poor, and if it exceeds the above range, the mechanical properties will deteriorate, which may be undesirable. The composition used in the present invention may also contain additional components within a range that does not significantly impair the effects of the present invention. Additional components include phenolic, sulfur, and phosphorus antioxidants; higher fatty acid derivatives such as metal salts, amides, and esters; organic or inorganic pigments; ultraviolet absorbers; antistatic agents; copper damage inhibitors; Neutralizing agent; Antifoaming agent; Flame retardant; There are thermoplastic resins and fillers other than those used in the present invention, and these are used in the form of being blended in advance with the above-mentioned crystalline propylene copolymer or synthetic rubber. It's okay if it's hot. Among thermoplastic resins other than those used in the present invention,
In particular, when an ethylene polymer having a density of 0.945 g/cm ³ or more and having a specific interaction with the carbon black surface is used, the conductivity of the composition is further improved. As the filler other than talc, in addition to general-purpose fillers such as calcium carbonate, mica, and glass fiber, other conductive fillers such as graphite, carbon fiber, metal fiber, and metal powder can be used. The composition used in the present invention is produced using a conventional kneading machine such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll, or a Brabender plastograph. The injection molded article of the present invention is obtained by molding this composition by a conventional injection molding method. The conductive injection molded article of the present invention has significantly improved the extremely poor dimensional accuracy, which is a major drawback of conventional injection molded articles made of conductive polypropylene resin compositions, and has also improved the conductivity compared to conventional injection molded articles made of conductive polypropylene resin compositions. This is an epoch-making product that has been dramatically improved compared to the previous version. Particularly preferably, as component (a), (1) the soluble content extracted with xylene at 23°C is 15 to 50% by weight, and (2) the content of propylene in this extractable content is 35% by weight or more. 50 to 80% by weight of a crystalline copolymer resin of propylene and other α-olefins, or a resin composition blended with synthetic rubber, is used as component (b), and the average particle size is 0.5 to 20μ. 20 to 50% by weight of a certain talc and (c) component carbon black as (a) + (b)
Injection molded products using a composition containing 4 to 50 parts by weight per 100 parts by weight are revolutionary in that they have particularly good dimensional accuracy, extremely low mold shrinkage, and almost no molded product sink marks or warpage. It has the characteristics of Example 1 Copolymerization of propylene and ethylene using a Ziegler-Natsuta catalyst, resulting in an ethylene content of 13% by weight
Thus, a crystalline propylene/ethylene block copolymer (A) containing 21% by weight of xylene extractables at 23° C. and having a melt flow rate (MFR) of 15 g/10 minutes was obtained. The propylene content in the soluble matter extracted with xylene at 23° C. in (A) was 50% by weight. 65 parts by weight of this powder (A) and fine talc (with an average particle diameter of 2.8μ, a content of coarse particles of 10μ or more of 5% by weight, and a specific surface area of 27000cm ² /g) manufactured from talc produced in China. 35 parts by weight of iron and aluminum (containing a total of 0.1% by weight of iron and aluminum as impurities), 8 parts by weight of Ketchen Black (specific surface area 1000 m ² /g) and 0.2 parts of 2 , 6-di-t-butyl-4-methylphenol were mixed uniformly in a super mixer, and then kneaded in a 30 mm diameter twin screw extruder to form pellets. This pellet was molded into a test piece at 260°C using a screw-in light injection molding machine, and the test piece was evaluated. For comparison, the propylene/ethylene block copolymer (A), ethylene content 4% by weight, MFR 8g/10, polymerized in the same manner as this copolymer (A).
Propylene-ethylene block copolymer (B) with the properties shown in Table 1 in minutes, propylene-ethylene block copolymer (C) with an ethylene content of 18% by weight and an MFR of 8g/10 minutes, and an ethylene content of 38% by weight.
Various proportions of propylene-ethylene block copolymer (D) with MFR of 24 g/10 min or crystalline propylene homopolymer (E) with MFR of 15 g/10 min and talc, and 100 parts by weight of these 8 parts by weight of Ketchen Black was mixed therein, kneaded and injection molded in the same manner as before, and the test pieces were evaluated. These results are shown in Table 1. As can be seen from the results in this table, the dimensional accuracy of the examples was dramatically superior to that of the comparative examples, and the conductivity was also good.

[Table] * Comparative Example Example 2 Add 1 part by weight of ethylene-propylene copolymer rubber (EP07P) to 100 parts by weight of a crystalline propylene-ethylene block copolymer obtained by copolymerizing propylene and ethylene using a Ziegler-Natsuta catalyst. By mixing and kneading parts by weight, the ethylene content is 10% by weight and 23
A propylene/ethylene copolymer composition (F) containing 18% by weight of xylene extractable content was obtained. The propylene content in the xylene-extracted component at 23° C. of this composition was 45% by weight. This copolymer composition (F) has an average particle size of 1.3μ, a coarse particle content of 5μ or more and 4%, and a specific surface area of 28000.
cm ² /g of finely powdered talc manufactured from Chinese talcum in various proportions, and a total of 100
After mixing 8 parts by weight of Ketchen black (specific surface area: 1000 m ² /g), the mixture was kneaded and injection molded into test pieces in the same manner as in Example 1, and the physical properties were measured. For comparison, instead of the copolymer composition (F),
82 parts by weight of crystalline propylene homopolymer (E) and
Mix and knead 18 parts by weight of ethylene-propylene copolymer rubber (EP07P manufactured by Mitsubishi Yuka Co., Ltd.) to obtain 18% by weight of xylene extract at 23°C (propylene content 28% by weight).
Mix 75 parts by weight of the product (G) with 25 parts by weight of the same talc as above, and further mix and knead 8 parts by weight of the same talc as above for a total of 100 parts by weight. The specimens were injection molded and evaluated. As can be seen from the results summarized in Table 2, the compositions of Examples had extremely superior dimensional accuracy and conductivity, and had good heat resistance, rigidity, and impact resistance, compared to those of Comparative Examples.

[Table] * Comparative Example Example 3 In No. 3 of Example 1, 20 parts by weight each of Vulcan SC and Vulcan C (both trade names of Furness Black manufactured by Cabot) were added instead of 8 parts by weight of Ketchen Black. A similar experiment was conducted using The results are shown in Table 3.

[Table] Example 4 The same crystalline propylene used in Example 1.
60 parts by weight of ethylene block copolymer (A), 40 parts by weight of fine talc, 15 parts by weight of ketsty block copolymer (A) and 0.2 parts by weight per 100 parts by weight of these.
Parts by weight of 2,6-di-t-butyl-4-methylphenol were mixed and kneaded into pellets in the same manner as in Example 1, and the pellets were injection molded to form a computer housing. It had good electromagnetic shielding properties, extremely excellent dimensional accuracy, and good moldability, heat resistance, and mechanical properties. Example 5 A similar experiment was conducted in Example 3 using 40 parts by weight of CSX-99 (furnace black brand name manufactured by Cabot) in place of 15 parts by weight of Kettien Black. A computer housing with extremely excellent heat resistance was obtained.

Claims (1)

[Scope of Claims] 1. Comprising the following components (a) to (c), (a) and (b)
25 to 90% by weight of ingredients (a) + (b) and
Consisting of a composition containing 75 to 10% by weight, and 2 to 100 parts by weight of component (c) based on 100 parts by weight of (a) + (b),
A conductive injection molded article characterized by a molding shrinkage rate of 0.6% or less. (a) A composition comprising a propylene polymer resin, optionally blended with synthetic rubber, (1) Extractable content in xylene at 23°C is 10 to 50% by weight
(2) The propylene content in the extracted soluble matter is 30% by weight or more; (b) The average particle size measured by the light transmission method of the liquid phase sedimentation method is
Talc (c) Super Conductive Furness (S.
CF), conductive furnace (CF) and extra conductive furnace (XCF).