JPH031338B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical Field The present invention relates to a conductive resin composition, particularly a conductive resin composition having excellent bending resistance. (b) Prior Art Thermoplastic resins such as polyethylene, polypropylene, polyamide, polyester, etc. are used in many applications as fibers, films, and molded products. However, such thermoplastic resins generally have poor antistatic properties and are therefore easily charged.For example, clothing made of polyester (polyethylene terephthalate fiber) may cling to the body when worn, or even be charged. Therefore, it attracts dust floating in the air, causing many problems such as easy staining. As a method to solve this problem, methods have been proposed such as mixing an antistatic compound into the resin in advance or adding a conductive substance such as conductive carbon. However, for example, conductive fibers, conductive films, conductive sheets, etc. obtained from resins containing conductive carbon are significantly colored because the conductive carbon is black, and cannot be used in fields where aesthetics are required. It has the disadvantage that its uses are extremely limited. As a method to solve the disadvantages caused by such coloring,
Recently, methods have been proposed for obtaining conductive fibers, conductive films, etc. using colorless or light-colored conductive resin compositions containing colorless or light-colored conductive metal compounds, particularly conductive metal oxides. (c) Problems to be solved However, conductive fibers, conductive films, etc. manufactured based on these proposals lose their conductivity after being bent several dozen times, and it is difficult to expect that conductivity will be lost after a short period of time when worn. As a result of losing its antistatic effect, it causes clinging to clothes and adhesion of dust as described above. (d) Means for solving the problem As a result of intensive research on a method for proposing a conductive molded product free from such drawbacks, the present inventors found that the surface of the conductive metal oxide powder is hydrophilic and that it is compatible with the thermoplastic resin. We learned that this was due to low affinity.
It has been discovered that if the surface of a conductive metal oxide is made lipophilic in advance and then made into a molded product using an olefin polymer blended with this, a conductive molded product with bending durability can be obtained, and the present invention has been made. has been reached. (e) Structure of the Invention That is, the present invention relates to a conductive resin composition formed by blending a conductive metal oxide and a specific lipophilic agent into an olefin polymer. The olefin polymer used in this application includes:
Examples include polyethylene, polypropylene, etc., which may partially contain a copolymer component, or may be a mixture of two or more of these, if necessary. The conductive metal oxides used in the present invention are mainly stannic oxide and zinc oxide. Also included are conductive metal composites obtained by coating the surface of particles with stannic oxide containing a small amount of an antimony compound. Zinc oxide also includes conductive zinc oxide in which a small amount of aluminum oxide or lithium oxide is dissolved. These are usually treated as fine powders. As a lipophilic agent for such a conductive metal oxide,
The organic residue bonded to the carboxyl group or sulfonic acid group is an alkyl group, alkylene group, aryl group, alkylaryl group, or aralkyl group having 5 or more carbon atoms. Organic carboxylic acids or organic sulfonic acids are used. Specific examples of organic carboxylic acids used as lipophilic agents include n-caproic acid, n-heptanoic acid,
Examples include benzoic acid, n-caprylic acid, phenylacetic acid, toluic acid, n-nonanoic acid, n-caprylic acid, stearic acid, and the like. Further, specific examples of organic sulfonic acids include n-pentanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, and the like. These organic carboxylic acids and organic sulfonic acids used as lipophilic agents may be used alone or in appropriate combinations. When the number of carbon atoms of the organic group bonded to the carboxyl group or sulfonic acid group of the organic carboxylic acid or organic sulfonic acid used as a lipophilic agent is 4 or less,
It is clear from the lipophilicity determination described below that the conductive metal oxide after the lipophilic treatment moves to the water layer and is not lipophilic. The bending durability of the conductive molded product formed from the combination also does not improve. Methods for making conductive metal oxides lipophilic vary depending on the type of olefin polymer used and the type of lipophilizing agent, but methods include thermal treatment of organic carboxylic acids or organic sulfonic acids as lipophilic agents. Considering the characteristics, (1) a method of directly melt-mixing the olefin polymer, a conductive metal oxide, and a lipophilic agent, (2) a method of directly melt-mixing the conductive metal oxide with a lipophilic agent, and then adding the olefin polymer. It is preferable to appropriately select either the coalescence method or the melt-mixing method. For example, it is not preferable to try to obtain a conductive resin composition by directly melt-mixing an organic carboxylic acid with a low boiling point such as n-heptanoic acid as a lipophilic agent into a high melting point olefin polymer together with a conductive metal compound. . In such a case, it is preferable to treat the conductive metal oxide with n-heptanoic acid in advance and then melt-mix it with the olefin polymer. On the other hand, even if the same n-heptanoic acid is used as the lipophilic agent, if the olefin polymer used has a relatively low melting point such as polyethylene, the conductive metal oxide and n-heptanoic acid can be directly mixed into polyethylene. There is no problem in melting and mixing. As a method for preliminarily treating a conductive metal oxide to make it lipophilic, a desired conductive metal oxide powder was added and dispersed in a solution obtained by dissolving a lipophilic agent in an organic solvent, and the mixture was stirred for several hours. A very simple method is used in which the organic solvent and powder are then filtered off. The amount of the lipophilic agent used is preferably kept to a necessary and sufficient minimum amount, and is usually in the range of 0.1 to 3 parts by weight per 100 parts by weight of the conductive metal oxide powder. If the amount of the lipophilic agent is less than 0.1 part by weight, it may be difficult to make the surface of the conductive metal oxide sufficiently lipophilic by the treatment. In addition, if the amount exceeds 3 parts by weight, it becomes difficult to filter it from the dispersion of the organic solvent after treatment, and it becomes necessary to wash away the excess lipophilic agent after filtration, which is undesirable. . Further, when the lipophilic agent and the conductive metal acid oxide are directly melt-mixed with the thermoplastic resin, it is not preferable to add an excessive amount of the lipophilic agent because it impairs the physical properties of the olefin polymer. In the method of pre-treating a conductive metal oxide with a lipophilic agent, the conductive metal oxide can be made lipophilic by simply dispersing the conductive metal oxide in an organic solvent solution of the lipophilic agent and stirring at room temperature for several hours, as described above. However, heating is effective for processing in a shorter time.
The organic solvent used here is not particularly limited as long as it dissolves the organic carboxylic acid and/or organic sulfonic acid compound that is the lipophilic agent, but if heat treatment is required, a solvent with a low boiling point is not preferred. . If the conductive metal oxide is not lipophilic and therefore does not have sufficient affinity with the olefin polymer,
It is difficult to determine whether the conductive metal oxide has been sufficiently made lipophilic because fibers, films, etc. formed by molding the resulting resin composition suffer from loss of conductivity due to bending. , is extremely important in the present invention, and furthermore, this determination is
This is extremely important because it serves as a standard for determining the amount of lipophilizing agent used for lipophilization. In particular, when melt-mixing a conductive metal oxide directly into an olefin polymer together with a lipophilic agent, it is important to determine in advance the necessary and sufficient amount of the lipophilic agent. It is necessary to select an appropriate judgment method from the meaning point of view as well. In this determination method, a conductive metal oxide powder that has been heated and stirred in a solution in which a lipophilic agent is dissolved in an organic solvent to make it lipophilic is mixed with water and an organic solvent that is incompatible with water. It is extremely effective to make the conductive metal compound powder into a lipophilic layer by transferring the conductive metal compound powder to the organic layer when it is placed in a liquid consisting of layers, stirred, and then allowed to stand still. When melt-mixing a lipophilized conductive metal oxide with an olefin polymer, or adding the necessary amount of lipophilic agent and conductive metal oxide to the olefin polymer to make the conductive metal oxide lipophilic. When directly melt-mixing the composite, an appropriate viscosity modifier may be used, and if necessary, in order to perform the mixing effectively and to improve the moldability of the resulting conductive resin composition. There is no harm in using an antioxidant as needed. (f) Effects of the invention Fibers, films, sheets, etc. molded from a resin composition made of a mixture of a conductive metal oxide and an olefin polymer that have been made lipophilic according to the present invention have extremely high conductivity without losing their conductivity when bent. Performance can be maintained. (g) Examples The present invention will be specifically explained below using examples. Example 1 Titanium oxide fine particles whose surface was coated with conductive tin oxide, average particle size 0.2μ, specific resistance 10Ω・cm
3 toluene was added to 1 kg of the conductive powder and 20 g of n-heptanoic acid, and the mixture was heated under reflux for 5 hours with vigorous stirring. After the mixture was allowed to stand overnight, most of the toluene was removed by decantation, and the powder was filtered, thoroughly washed with toluene, and dried. When a small amount of this dry powder was poured into a liquid for determining lipophilicity consisting of two layers of 100 ml of water and 100 ml of benzene and shaken, the powder moved to the benzene layer and became lipophilic. It was determined that The untreated conductive powder was in the aqueous layer, and the conductive powder treated in the same manner as above except that n-heptanoic acid was not added was also transferred to the aqueous layer. 250 parts by weight of lipophilized powder, liquid paraffin
20 parts by weight and melt index 75 (JIS K6760
-1971) was placed in a kneader, heated to 175°C, and mixed for 5 hours. The specific resistance of the obtained conductive resin was 4×10 ² Ω·cm.
By melt spinning, a core-sheath type composite fiber (core-sheath ratio = 1/6) with this conductive resin as a core and polyethylene terephthalate as a sheath was made, and it was stretched 4 times to 100
A conductive multifilament with a denier and a single thread count of 12 was obtained. This conductive composite fiber was cut into a length of 1 cm, a conductive paint was applied to both ends, and the electrical resistance between the ends was measured and found to be 2×10 ⁷ Ω. Furthermore,
This conductive composite fiber was cut into a length of 20 cm, a weight of 100 g (1 g per denier) was hung on one end, and the other end was repeatedly bent by lifting and lowering the other end by hanging it on a freely rotating support rod of 1 mm in diameter. central part 1
The relationship between the number of bends and the electrical resistance was investigated by cutting out a cm piece, applying conductive paint to both ends, and measuring the electrical resistance between the two ends. As a result, the values shown in the left column of Table 1 were obtained. For comparison, the right column of Table 1 shows the results of conducting a bending test in the same manner on conductive composite fibers obtained in the same manner except for using conductive powder that was not subjected to lipophilization treatment with n-heptanoic acid. Ta.

[Table] Example 2 250 parts by weight of the final-treated conductive powder described in Example 1 and 80 parts by weight of polyethylene with a melt index of 75 were charged in a kneader and kneaded at 175°C for 30 minutes, followed by 20 parts by weight of liquid paraffin. 3 parts by weight of stearic acid was added as a lipophilic agent and kneaded for further 4 hours. The specific resistance of the obtained conductive resin was 2.8×10 ² Ω・
It was cm. A conductive composite fiber having this conductive resin as a core and polyethylene terephthalate as a sheath was obtained in the same manner as in Example 1. This fiber was subjected to a bending test in the same manner as in Example 1 to examine the relationship between the number of bends and the electrical resistance value, and the results shown in the left column of Table 2 were obtained. For comparison, similar tests were conducted on fibers with resin cores prepared with exactly the same loading amount except that stearic acid was not mixed, and the results are shown in the right column of the same table.

[Table] Examples 3 to 6 Conductive resins were prepared in the same manner as in Example 1, using various acids shown in Table 3 instead of the lipophilic agent n-heptanoic acid used in Example 1. However, in the same manner as in Example 1, a composite fiber having this resin as a core and polyethylene terephthalate as a sheath was prepared, and the change in electrical resistance due to bending was examined. As shown in Table 3, good results were obtained in all cases.

[Table] Comparative Examples 1 to 4 The conductive powder shown in Example 1 was treated using various acids shown in Table 4 instead of n-heptanoic acid used in Example 1. . The treated powder was placed in a test liquid consisting of two layers of water and liquid paraffin and shaken, but all of the conductive powder was in the water layer. Using this powder, a composite fiber having a polyethylene terephthalate sheath was made in the same manner as in Example 1, and the change in electrical resistance due to bending was examined. The results are shown in Table 4.

[Table] Example 7 250 parts by weight of conductive metal powder made of stannic oxide containing a small amount of antimony trioxide and 50 parts by weight of polypropylene with a melt flow index of 1.0 (ASTM D1238-65T) were charged in a kneader and heated to 200°C. at 30
After melt-mixing for minutes, 3 parts by weight of stearic acid, 50 parts by weight of liquid paraffin, 10100.5 parts of Irganox
Parts by weight were added and kneaded for an additional 4 hours. The specific resistance of the conductive resin thus obtained is 5.5×10 ²
It was Ω・cm. A core-sheath type composite fiber (core-sheath ratio = 1/5) with this conductive resin as a core and nylon-6 as a sheath was made by melt spinning, and then stretched 4 times.
A conductive multifilament of 100 denier and 12 yarns was obtained. Cut this conductive composite fiber into a length of 1 cm,
The electrical resistance was measured in the same manner as in Example 1 and found to be 3×10 ⁷ Ω. Furthermore, the changes in electrical resistance of this fiber depending on the number of bends were investigated in the same manner as in Example 1, and the results are shown in the left column of Table 5. For comparison, conjugate fibers obtained in the same manner except that stearic acid was not used were examined for changes in electrical resistance depending on the number of bends, and the results are shown in the right column of Table 5. When stearic acid was not added, conductivity was lost after 100 bends.

【table】

Claims (1)

[Scope of Claims] 1. A conductive resin composition comprising a polyolefin polymer, a conductive metal oxide, and at least one of the following lipophilic agents. Lipophilic agent Organic carboxylic acid or organic sulfonic acid 2 in which the organic residue bonded to the carboxyl group or sulfonic acid group is an alkyl group, alkylene group, aryl group, alkylaryl group, or aralkyl group having 5 or more carbon atoms. The conductive resin composition according to claim 1, wherein the conductive metal oxide is stannic oxide and/or zinc oxide.