JPS642615B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention combines carbon black with a specific ratio composition of propylene polymer, high-density ethylene polymer, and inorganic filler, which has excellent molding processability, molded product appearance, and mechanical properties, and dramatically improves electrical conductivity. Enhanced resin composition. 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 polypropylene containing carbon black has poor moldability (kneadability) and appearance of molded products, and those containing a high proportion of carbon black and those containing carbon black with a large specific surface area are particularly poor. However, there were some drawbacks, and there was a major problem in that the scope of application was extremely limited. In order to alleviate this problem, various methods have been investigated from various angles. First, several known techniques were applied to a polypropylene composition containing carbon black, and their effects were confirmed. First, it was proposed to improve the molding processability of thermoplastic resin compositions containing carbon black. The method of dispersion in a plastic resin (Japanese Unexamined Patent Publication No. 52-47843) was applied to polypropylene for detailed study. As a result, it was found that although there was certainly some improvement in moldability compared to simply blending carbon black with polypropylene, the degree of improvement was not very large, and it was found that the conductivity tended to deteriorate. Ivy. Second, in order to further improve the electrical conductivity of thermoplastic resin compositions containing carbon black, the main material is two or more materials that are difficult to be compatible with each other, and the interface between the main materials is carbon black. The method of making black exist (Japanese Patent Publication No. 49-14532) was applied to polypropylene and studied in detail.
As a result, although a certain degree of improvement in electrical conductivity was observed compared to a product in which carbon black was simply blended with polypropylene, the desired improvement in moldability was not observed. Based on this situation, as a result of various considerations,
Surprisingly, by blending a predetermined amount of ethylene polymer with a density of 0.945 g/cm ³ or more into propylene polymer, carbon black has excellent moldability and appearance, and has dramatically improved conductivity. It was discovered that a blended propylene polymer composition could be obtained, and it was proposed (Japanese Patent Application No. 1986-43867).
issue). As a result of further studies, the present inventors found that by blending a predetermined amount of inorganic filler in addition to a propylene polymer and an ethylene polymer with a density of 0.945 g/cm ³ or more, the moldability and appearance of the molded product could be improved. Be excellent,
Furthermore, the inventors have completed the present invention by discovering that a carbon black-containing propylene polymer composition with dramatically improved conductivity can be obtained. That is, the present invention is a resin composition characterized by consisting of the following (a) to (b), in which (a) is replaced by (a) + (b) + (c).
80~25% by weight based on the standard, (b) 5~5% based on (a) + (b) + (c)
55% by weight, (c) 15 to 70% by weight based on (a) + (b) + (c), and (d) 2 to 100 parts by weight of (a) + (b) + (c). This is a conductive resin composition containing 100 parts by weight. (a) Crystalline propylene polymer selected from propylene homopolymer and propylene-ethylene block copolymer (b) Ethylene polymer having a density of 0.945 g/cm ³ or more (c) The following with an average particle size of 20 μ or less (d) Fine inorganic filler other than ingredients (d) Super conductive furnace (S.
CF), Conductive Furness (CF)
and Extra Conductive Furnace (XCF).The content of the present invention will be described in detail below. The propylene polymer used in the present invention is a crystalline propylene polymer selected from propylene homopolymers (polypropylene) and propylene-ethylene block copolymers. These may contain up to 15% by weight of unsaturated organic acids (acrylic acid, maleic anhydride, etc.) or their derivatives, or vinyl monomers such as aromatic unsaturated monomers (styrene, etc.) unless the effects of the present invention are significantly impaired. It may also be a graft. In addition, propylene-ethylene block copolymer
Although it contains 50% by weight or more, it may contain 20% by weight or less of α-olefin having 4 or more carbon atoms as long as the effects of the present invention are not significantly impaired. These propylene polymers improve the moldability of the composition,
An appropriate grade index can be selected depending on required performance such as mechanical properties. Generally, the melt flow rate (MFR) is 0.01~
30g/10 minutes is preferably selected. When a propylene-ethylene block copolymer is used, the effect of improving conductivity by blending a predetermined amount of polyethylene of a specific density is significant. These propylene polymers include 2,6-di-t-
Butyl-4-methylphenol, 1,1,3-tri-(2-methyl-4-hydroxy-5-t-butylphenyl)butane, tetrakis[methylene(3,5-t-butyl-4-hydroxyhydrocinmine) (acid esters)] Phenol antioxidants such as methane, sulfur antioxidants such as dilauryl-thio-dipropionate, distearyl-thio-dipropionate, and the like may be blended as necessary. In addition, resins other than the above-mentioned propylene polymers and propylene polymers may be used as long as the effects of the present invention are not significantly impaired.
Ethylene copolymer rubber, propylene-ethylene-
Other components such as diene monomer terpolymer rubber can also be blended to improve the physical properties of the composition. Next, the ethylene polymer used in the present invention is an ethylene polymer having a density of 0.945 g/cm ³ or more,
Only this can exhibit the specific effects of the present invention. Such ethylene polymers can be obtained by the conventional so-called low-pressure process, that is, the polymerization of ethylene carried out in the presence of various catalysts at 100 atmospheres, preferably below 35 atmospheres. At that time, propylene, 1-
Other α such as butene, 1-pentene, 1-hexene, etc.
- It may be a high-density ethylene polymer copolymerized by feeding a small amount of olefin and copolymerizing the total polymer amount at 5% by weight or less, preferably 3% by weight or less. Among ethylene polymers having a density of 0.945 g/cm ³ or more, high-density ethylene polymers having a density of 0.960 g/cm ³ or more are particularly preferred. The molecular weight can be selected from a weight average molecular weight of several thousand to several hundreds of thousands. As inorganic fillers, those from groups of the periodic table ~
Group metal atoms (e.g. Na, K, Ca, Mg,
Ba, Zn, Al, Fe, Ti, etc.) and silicon oxides, hydroxides, sulfides, carbonates, sulfates, silicates or some of these compounds are present in various clay minerals. A solid substance can be used. Specifically, for example, iron oxide, zinc oxide, titanium oxide, alumina, silica, calcium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium carbonate (heavy, light, colloid), barium sulfate, Calcium sulfate, calcium silicate, talc, wollastonite, clay, glass beads,
Examples include glass powder, silica sand, quartz powder, shirasu, diatomaceous earth, and the like. Two or more of these can also be used in combination. The average particle size of these inorganic fillers is 20μ
They are as follows, and anything larger than this is unfavorable in terms of moldability and appearance of the molded product. Furthermore, the carbon black used in the present invention is
SCF (Super Conductive) with a large specific surface area
Furnace), CF (Conductive Furnace) and
It is at least one kind selected from XCF (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'', CF is also ``Vulcan C'', and XCF is represented by AKZO's ``Ketschenblak'', as well as Cabot's ``Vulcan XC-72'' and ``CSX-99''. It is true. 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. 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 conductive furnace black is selectively used. Therefore, when crystalline propylene polymer is blended with high-density polyethylene, delamination occurs due to lack of compatibility, but this special graphite structure on the surface of carbon black They exhibit a specific affinity with the crystal structure and are extremely compatible with each other.
It was surprising that the propylene polymer had a unique compatible structure that does not cause delamination and exhibits high conductivity, thereby achieving the effects of the present invention. 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 comprises (a) a propylene polymer, (b) a high-density ethylene polymer, (c) an inorganic filler, and (d)
Carbon black is used, and the blending ratio of (a) to (a) + (b) + (c) is 80 to 25% by weight, preferably 60 to 30% by weight, (b) (a) + (b) + (c)
5 to 55% by weight, preferably 10 to 30% by weight,
15 to 70% by weight of (c) based on (a) + (b) + (c), preferably
A range of 20 to 40% by weight and 2 to 100 parts by weight of (d) per 100 parts by weight of (a)+(b)+(c) is suitable. If the amount of the high-density ethylene polymer is less than the above range, the molding processability, appearance of the molded product, and electrical conductivity may deteriorate, and if it exceeds the above range, the electrical conductivity may deteriorate. If the amount of inorganic filler is less than the above range, there will be no effect of improving conductivity, and if the amount exceeds the above range, mechanical properties may deteriorate. If the amount of carbon black 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. Carbon black with a large specific surface area provides a high degree of conductivity at a relatively low concentration in the above blending range. Of these, the specific surface area is 850m ² /
Ketchen black of more than 900 m ² /g, especially more than 900 m 2 /g, provides a high degree of conductivity in areas of very low concentration. The composition of the present invention can be easily obtained using a continuous extruder such as a single-screw extruder or a twin-screw extruder in addition to a batch-type kneader such as a Banbury mixer, a roll, or a Brabender plastogram. The order of blending is not particularly limited,
In addition to the method of mixing and kneading the formulation all at once,
It is also possible to first knead a specific high-density ethylene polymer and carbon black in a batch-type or continuous-type extruder, and then knead the kneaded product with the propylene polymer and the inorganic filler. It is also possible to first knead the high-density ethylene polymer, inorganic filler, and carbon black, and then knead the kneaded product with the propylene polymer. Furthermore, it is also possible to dry blend a kneaded product of a specific high-density ethylene polymer, an inorganic filler, and carbon black with a propylene polymer, and then subject the mixture to a molding process such as injection molding. The present invention is based on the above-mentioned proposal discovered prior to the present invention, namely, a propylene polymer and a material having a density of 0.945.
By adding a predetermined amount of an inorganic filler to a composition consisting of an ethylene polymer of g/cm ³ or more and carbon black, the density can be increased.
The special effect of the inorganic filler is added to the specific interaction between the ethylene polymer of 0.945 g/cm ³ or more and the carbon black particles. As a result, in addition to the effects of the proposals prior to the present invention mentioned above, (1) processability during compound production, (2) various moldability (injection molding, extrusion molding, etc.), and (3) improvement in the appearance, etc. of various molded products. In addition to the effects, we were also able to achieve a dramatic improvement in conductivity. The effect of dramatically improving conductivity due to the addition of an inorganic filler far exceeds the effect of improving conductivity due to an increase in the blending ratio of carbon black to the polymer due to a decrease in the volume of the polymer portion due to the addition of an inorganic filler. Such an unexpectedly significant effect of improving conductivity was discovered for the first time through detailed experiments conducted by the present inventors. The mechanism that exerts this effect is not clearly elucidated, but the amount of inorganic filler added is 15%.
Since this effect only appears when the amount exceeds % by weight, it is considered that the major cause is that the addition of the inorganic filler changes the dispersion form of carbon black in a direction that is advantageous for improving conductivity. Therefore, it is considered that this effect is not due to a simple effect of increasing the amount of the inorganic filler, but is due to a complex cause such as the special dispersion form of carbon black. As a result of the composition of the present invention having such high conductivity, it has extremely good electromagnetic wave shielding properties, and together with improved rigidity and dimensional accuracy due to the inorganic filler formulation, it can be used in electronic devices that need to avoid electromagnetic interference, It is extremely suitable for use in the field of housing for office equipment, etc., packaging containers for ICs, etc., and is also suitable for a wide range of fields such as containers for hazardous materials such as gasoline, thin-film batteries, and surface heating elements. Example 1 Polypropylene (MFR4.5g/10min), density
0.965g/ ^cm3 high density polyethylene (MFR5.5g/
10 minutes), 6 parts by weight of talc (specific surface area 1000 m ² /g) and 0.2 parts by weight of 2,6 to 100 parts by weight of the total amount of talc with an average particle size of 3 μm. -di-t-butyl-4-
Methyl phenol was blended and mixed using a super mixer, and kneaded using a PCM30 twin screw extruder manufactured by Ikegu Iron Works Co., Ltd. to form pellets. A sheet having a thickness of 2 mm was obtained by compression molding the pellets. The volume resistivity of this sheet was measured by the Wheatstone bridge method according to SRIS standard 2301-1969. The results are shown in Table 1. As is clear from Table 1, the volume resistivity, which is a measure of electrical conductivity, of the examples was extremely low and good compared to that of the comparative examples.

[Table] Example 2 The same experiment as in Example 1 was conducted using 15 parts by weight of furnace black ("CSX-99" manufactured by Cabot) instead of 6 parts by weight of Ketchen black. The results are shown in Table 2. As is clear from Table 2, the volume resistivity of the examples was very low and good compared to that of the comparative examples.

[Table] Example 3 Propylene-ethylene block copolymer with ethylene content of 8% by weight (MFR4.0g/10min), density
0.960g/ ^cm3 high density polyethylene (MFR5.0g/
10 minutes), 6 parts by weight of calcium carbonate (specific surface area 1000
m ² /g) and 0.2 parts by weight of 1,1,3-tri-
The mixture was kneaded with (2-methyl-4-hydroxy-5-t-butylphenyl)butane in a Brabender plastogram at a temperature of 230°C for 5 minutes. Table 3 shows the volume resistivity of a 2 mm thick sheet obtained by compression molding this kneaded product. As is clear from Table 3, the volume resistivity of the examples was much lower and better than that of the comparative examples.

[Table] Example 4 48 parts by weight of propylene-ethylene block copolymer with an ethylene content of 8% by weight (MFR4.0g/10min), high density polyethylene with a density of 0.960g/ ^cm3 (MFR5.0g/10min)32 parts by weight, 20 parts by weight of talc with an average particle size of 5μ, 15 parts by weight of ketschen black and 0.2 parts by weight of 2,6-di-t-butyl-4-methylphenol based on 100 parts by weight of the total amount. and propylene content as an impact strength modifier.
15 parts by weight of 28% ethylene-propylene copolymer rubber having a Mooney viscosity of 75 was added and mixed in a super mixer, followed by continuous kneading and pelletization in a PCM30 twin-screw extruder manufactured by Ikegai Tekko Co., Ltd. These pellets were molded into test pieces at a temperature of 230°C using a screw-in-line injection molding machine manufactured by Kakki Seisakusho, and various physical properties of the test pieces were measured. It was Also,
When a computer housing was injection molded using this pellet, an extremely good product was obtained, which had good electromagnetic shielding properties, excellent appearance, mechanical properties, dimensional accuracy, and heat resistance. Example 5 42 parts by weight of polypropylene (MFR 1.0 g/10 min), 28 parts by weight of high-density polyethylene (MFR 5.5 g/10 min) with a density of 0.960 g/cm ³ , 30 parts by weight of talc with an average particle size of 3 μm, these 4.0 parts by weight of Ketchen black (specific surface area) per 100 parts by weight of the total amount
1000 m ² /g) and 0.2 parts by weight of 2,6-t-butyl-4-methylphenol were mixed in a super mixer and kneaded in a PCM30 twin screw extruder manufactured by Ikegai Tekko Co., Ltd. to form pellets. For comparison, 60 parts by weight of the same polypropylene, 40 parts by weight of the same high-density polyethylene, their total amount
Based on 100 parts by weight, 5.8 parts by weight of Ketchen Black and 0.2 parts by weight of the same antioxidant were mixed and kneaded in the same manner and pelletized. These pellets were injection molded in the same manner as in Example 1 to prepare test pieces, and the volume resistivity of the test piece sheets was measured. The results are shown in Table 4. As is clear from Table 4, the conductivity of the example containing an inorganic filler was higher than that of the comparative example, which did not use an inorganic filler and had the amount of KETCHEN BLACK mixed in the polymer component at the same level as the example. It is clear that this is not due to a simple increase in volume due to the addition of the inorganic filler.

[Table] Example 6 Volume resistivity was evaluated in the same manner as in Example 1, except that the blending ratios of polypropylene, high-density polyethylene, and talc were as shown in Table 5. The results are shown in Table 5 and FIG. As is clear from Table 5 and FIG. 1, compositions containing only polypropylene blended with a specific carbon black or compositions containing only a specific carbon black blended with high-density polyethylene have extremely low conductivity. In addition, conductivity is slightly improved in compositions in which specific carbon black is blended with a blend resin of polypropylene and high-density polyethylene, and in compositions in which specific carbon black and talc are blended together in a single resin of polypropylene or high-density polyethylene. It's not enough. In contrast, the composition of the present invention has dramatically improved conductivity.

【table】

[Table] Example 7 In Example 1, Vulcan SC and Vulcan C (both
A similar experiment was conducted using 20 parts by weight of Furness Black (trade name) manufactured by Cabot. The results are shown in Table 6.

【table】 [Brief explanation of the drawing]

FIG. 1 is a drawing showing the correlation between the high-density polyethylene blending ratio and the volume resistivity, which is the evaluation result of Example 6. Curve A is a combination system of talc and specific carbon black, and curve B is a combination system of specific carbon black.

Claims (1)

[Scope of Claims] 1. A resin composition comprising the following (a) to (d), wherein (a) is 80 to 25% by weight based on (a) + (b) + (c). %, (b) to (a) + (b) + (c) 5 to 55% by weight, (c) to (a)
15 to 70% by weight based on +(b)+(c) and (d) as (a)+(b)
+(c) A conductive resin composition containing 2 to 100 parts by weight based on 100 parts by weight. (a) Crystalline propylene polymer selected from propylene homopolymer and propylene-ethylene block copolymer (b) Ethylene polymer having a density of 0.945 g/cm ³ or more (c) The following with an average particle size of 20 μ or less (d) Fine inorganic filler other than ingredients (d) Super conductive furnace (S.
CF), Conductive Furness (CF)
and at least one carbon black selected from Extra Conductive Furnace (XCF).