JP2005075444A - Sealing member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing member used for, for example, an electronic component transfer case, which is excellent in retention of an antistatic function, is free of adverse effect on electronic components, etc., and is excellent in rubber elasticity which has freedom in coloring. <P>SOLUTION: The sealing member comprises a thermoplastic resin composition including (a) thermoplastic elastomer consisting of carbon atoms and hydrogen atoms and (b) a block polymer having a structure in which polyolefine blocks and hydrophilic group polymer blocks are bonded alternately. In the thermoplastic resin composition, the weight ratio (a):(b)=100:(2 to 100), JIS K6253 type A durometer hardness is 90 or less, and a volume resistivity value is 1×10<SP>12</SP>or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sealing member particularly useful as a plug for a packaging case of electronic components.

Currently, a plurality of chip-like electronic components and electronic substrates are housed in a resin case or the like for the purpose of transferring electronic components and electronic substrates or automatically loading them into an assembly apparatus by a cassette method. Many of these cases have a cylindrical shape, and sealing members such as soft resin and rubber material are inserted into the openings at both ends of the cylinder to prevent leakage of electronic components stored during transfer. . When installing in an assembly apparatus by a cassette system, these sealing members are removed and installed. For such a sealing member, a rubber stopper has been conventionally used, but a thermoplastic elastomer that can be recycled has come to be used due to recent environmental considerations. Among them, there are many examples of olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers.
However, many of the thermoplastic elastomers used for these sealing members are often charged with static electricity, causing troubles to adsorb dust, and often have adverse effects on electronic components. Therefore, an antistatic agent such as a surfactant or conductive carbon has been added to prevent dust adhesion. However, the surfactant antistatic agent is easy to fall off due to friction, etc. Adjustment is difficult. If the amount is too small, the antistatic effect is insufficient. If the amount is too large, the electronic components housed in the case are adversely affected. In addition, the conductive carbon loses transparency and the color of the molded product is limited to black. In addition, the surface of the molded product deteriorates and the conductive carbon powder is peeled off, which has an adverse effect on electronic components.

  The object of the present invention is to provide a highly durable antistatic function without impairing the high rubber elasticity and small compression set of a thermoplastic elastomer, in view of the situation of the prior art, and to electronic parts and the like. It is an object of the present invention to provide a sealing member that has very little adverse effect and is excellent in rubber elasticity with a degree of freedom in coloring.

The object is (a) a thermoplastic elastomer composed of carbon atoms and hydrogen atoms, (b) a block polymer having a structure in which polyolefin blocks and hydrophilic group polymer blocks are alternately bonded, and the weight ratio is (a ): (B) = 100: from a thermoplastic resin composition having JIS K6253 type A durometer hardness of 90 degrees or less and a volume resistivity of 1 × 10 ¹² Ω · cm or less. This is achieved by providing a sealing member.

  As a sealing member for an electronic component transfer case, it is possible to provide a sealing member that is excellent in sustainability of an antistatic function, has no adverse effect on electronic components, and has excellent rubber elasticity with a degree of freedom in coloring.

  In the present invention, as the component (a), a thermoplastic elastomer (A) mainly composed of a hydrogenated block copolymer and an olefin elastomer (B) are useful. Of these, the thermoplastic elastomer (A) mainly composed of a hydrogenated block copolymer is useful because of its excellent rubber elasticity and small compression set.

The hydrogenated block copolymer of the thermoplastic elastomer (a) mainly composed of the hydrogenated block copolymer used in the present invention has two or more polymer blocks A composed of vinyl aromatic compounds in the molecule. And a hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least one polymer block B composed of a conjugated diene compound. For example, (AB) _m (m is 2 to 10). ), (AB) _n -A (n represents an integer of 1 to 10), (AB) _m -X (X represents a coupling agent residue, m represents 2 to 10 And a hydrogenated block copolymer obtained by hydrogenating a vinyl aromatic compound-conjugated diene compound block copolymer having a structure such as In the hydrogenated block copolymer, the content of the vinyl aromatic compound is preferably 5 to 75% by weight, and more preferably 10 to 65% by weight. If it is 5% by weight or less, compression set becomes large, and if it is 75% by weight or more, flexibility and rubber elasticity are lowered.

Examples of the vinyl aromatic compound constituting the block copolymer before hydrogenation include styrene, α-methylstyrene, o, m or p-methylstyrene, vinylnaphthalene, vinylanthracene and the like. Among these, styrene and α-methylstyrene are preferable. A vinyl aromatic compound may be used independently and may use 2 or more types together.
Examples of the conjugated diene compound constituting the block copolymer before hydrogenation include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3- Examples include hexadiene. Among these, isoprene, 1,3-butadiene or a mixture thereof is preferable. A conjugated diene compound may be used independently and may use 2 or more types together.

The microstructure of the polymer block B in the block copolymer before hydrogenation is not particularly limited. For example, when the polymer block B is a block made of polyisoprene, the amount of 1,4 bonds is preferably 80% or more. When the polymer block B is a block made of polybutadiene, the 1,4 bond amount is desirably 40 to 80%.
The bonding mode of the polymer block A and the polymer block B in the hydrogenated block copolymer may be linear or branched, or any combination thereof.

  When producing a hydrogenated block copolymer, from the viewpoint of heat resistance and weather resistance, 70% or more of unsaturated double bonds derived from the conjugated diene compound in the block copolymer before hydrogenation may be hydrogenated. preferable. The amount of unsaturated double bonds in the polymer block B in the hydrogenated block copolymer is determined by iodination measurement, infrared spectrophotometer, nuclear magnetic resonance apparatus or the like.

  Further, the hydrogenated block copolymer contains a functional group such as a carboxyl group, a hydroxyl group, an acid anhydride, an amino group, and an epoxy group in the molecular chain or at the molecular end unless the purpose of the present invention is impaired. May be.

  The above hydrogenated block copolymer includes an olefin resin such as polypropylene and polyethylene, a non-aromatic mineral oil, a non-aromatic liquid or a rubber which is a low molecular weight synthetic softener for the purpose of adjusting the hardness. Paraffinic and naphthenic process oils are preferably used. In the case of using the above-mentioned hydrogenated block copolymer blended with such an additive, these compositions are referred to as thermoplastic elastomers mainly composed of the hydrogenated block copolymer in the present invention. Examples of such a styrene-based elastomer composition include “Septon Compound” manufactured by Kuraray Plastics Co., Ltd., “Reostomer” manufactured by Riken Technos Co., Ltd., and “Lavalon” manufactured by Mitsubishi Chemical Co., Ltd. (all are trade names).

  The olefin elastomer (b) used in the present invention is preferably a composition comprising olefin rubber (i) and propylene polymer (ii) as main components. Examples of such olefin elastomers include “Thermo Run” (trade name) manufactured by Mitsubishi Chemical Corporation, “Miralastomer” (trade name) manufactured by Mitsui Petrochemical Co., Ltd., “Sumitomo TPE” manufactured by Sumitomo Chemical Co., Ltd., “ There are commercial products such as “Santoprene” (trade name).

  Examples of the olefin rubber (i) which is the main component of the olefin elastomer (b) include ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber (EPDM), ethylene-1- Examples thereof include elastic copolymers containing olefin as a main component, such as butene-nonconjugated diene copolymer rubber and propylene-1-butene-nonconjugated diene copolymer rubber. Of these, EPDM is preferred.

  Examples of the non-conjugated diene include dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, and ethylidene norbornene, and ethylidene norbornene is particularly preferable. A more preferred specific example of the olefin rubber (i) is EPDM having an ethylene content of 55 to 75% by weight and a non-conjugated diene content of 1 to 10% by weight. When the ethylene content is less than 55% by weight, the extrusion moldability is lowered, and when it is more than 75% by weight, the flexibility tends to be lost.

  On the other hand, the propylene copolymer (ii) which is another component of the olefin elastomer (b) is not particularly limited, but a copolymer of polypropylene or propylene and an α-olefin having 2 or more carbon atoms is preferable. . Specific examples of the α-olefin having 2 or more carbon atoms include ethylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-decene, 3-methyl-1-pentene, 4- Examples thereof include methyl-1-pentene and 1-octene.

  In the olefin elastomer (b), the content ratio of the olefin rubber (i) and the propylene polymer (ii) is as follows. That is, the olefin rubber (i) is usually 20 to 80% by weight, preferably 30 to 70% by weight, and the propylene polymer (ii) is 80 to 20% by weight, preferably 70 to 70% by weight based on the total amount of both. 30% by weight.

  As the olefin elastomer (b), for the purpose of improving rubber elasticity and compression set, a mixture of the olefin rubber (i) and the propylene polymer (ii) in the above proportion is dynamically added in the presence of a crosslinking agent. The heat-treated thing is preferable. Examples of the crosslinking agent include organic peroxides, phenol resins, and sulfur. Of these, organic peroxides are preferred.

  The olefin elastomers include non-aromatic mineral oils, non-aromatic liquids, or paraffinic and naphthenic process oils for rubber softeners that are low molecular weight synthetic softeners for the purpose of adjusting hardness. It is suitably used as a plasticizer.

  By using a thermoplastic elastomer having carbon atoms and hydrogen atoms as main constituents as described above, a thermoplastic composition which is flexible and has excellent rubber elasticity and a small compression set can be obtained. In the present invention, the thermoplastic elastomer mainly composed of carbon atoms and hydrogen atoms is preferably composed of only carbon atoms and hydrogen atoms, but may contain some other atoms. .

  Next, examples of the block polymer of the component (b) used in the present invention include polymers described in JP-A No. 2001-278985. Examples of the block polymer include those having a structure in which an olefin block and a hydrophilic polymer block are repeatedly and alternately bonded through an ester bond, an amide bond, an ether bond, a urethane bond, and an imide bond. The polyolefin block constituting the block polymer includes a polyolefin having carbonyl groups (preferably carboxyl groups, the same shall apply hereinafter) at both ends of the polymer, a polyolefin having hydroxyl groups at both ends of the polymer, and amino groups at both ends of the polymer. The polyolefin having is preferable. Furthermore, a polyolefin having a carbonyl group at one end of the polymer, a polyolefin having a hydroxyl group at one end of the polymer, and a polyolefin having an amino group at one end of the polymer can also be used. Among these, a polyolefin having a carbonyl group is preferable because of easy modification.

  Moreover, as a hydrophilic polymer which comprises the block polymer of (b) component, a polyether, a polyether containing hydrophilic polymer, a cationic polymer, and an anionic polymer can be used. More specifically, polyether diol, polyether diamine, and modified products thereof, polyether ester amide having a polyether diol segment as a polyether segment forming component, polyether amide imide having the same segment, and the same segment Polyetherester, polyetheramide having the same segment, and polyetherurethane having the same segment, having 2 to 80, preferably 3 to 60, cationic groups separated by a nonionic molecular chain in the molecule Examples include a cationic polymer, an anionic polymer having a dicarboxylic acid having a sulfonyl group and a diol or polyether as essential constituent units and having 2 to 80, preferably 3 to 60 sulfonyl groups in the molecule. .

  Specifically, a block polymer obtained by esterifying a modified polypropylene obtained by reacting polypropylene with maleic anhydride and polyalkylene glycol (polyethylene glycol, polypropylene glycol, etc.) in the presence of a catalyst is suitable. As mentioned. Examples of such a block polymer include “Pelestat 300”, a trade name marketed by Sanyo Chemical Industries.

  It is important that the amount of the component (b) block polymer added is 2 to 100 parts by weight per 100 parts by weight of the thermoplastic elastomer (a) composed of carbon atoms and hydrogen atoms. If it is less than 2 parts by weight, the necessary antistatic function does not appear. If it exceeds 100 parts by weight, it becomes hard and the rubber elasticity also decreases. It is preferable to add 3 to 20 parts by weight.

As described above, by using the block polymer of component (b), the volume resistivity of 1 × 10 ¹² Ω · cm or less is maintained while maintaining the rubber elasticity and excellent compression set characteristics of the thermoplastic elastomer of component (a). The antistatic function is obtained by the conductivity.

  The thermoplastic resin composition used in the present invention is an inorganic filler such as calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, magnesium carbonate for the purpose of improving heat resistance, weather resistance or increasing the amount. Can be mixed. Furthermore, mixing of inorganic or organic fibrous materials such as glass fibers and carbon fibers can be performed depending on the purpose. In addition, a heat stabilizer, an antioxidant, a light stabilizer, a flame retardant, a tackifier, a lubricant, a foaming agent, a colorant, and the like can be added.

  It is important that the thermoplastic resin composition used in the present invention has a hardness of 90 degrees or less (JIS K6253 type duro motor). When it exceeds 90 degrees, it lacks flexibility. A range of 30 to 85 degrees is particularly suitable. Such hardness can be obtained by appropriately selecting a blending ratio of (a) and (b) or a softener or olefin resin which is a component in (a).

It is important that the thermoplastic resin composition used in the present invention has a volume resistivity of 1 × 10 ¹² Ω · cm or less. If it exceeds 1 × 10 ¹² Ω · cm, the necessary antistatic function cannot be obtained. Such volume resistivity can be obtained by appropriately selecting the blending ratio of (b).

  As a method for producing the thermoplastic resin composition used in the present invention, a conventionally known method can be used without any particular limitation. For example, it can be obtained by kneading various components in a heated and melted state using a kneader or mixer such as a single screw extruder, twin screw extruder, Banbury mixer, Brabender, Henschel mixer, open roll, kneader.

  In the present invention, the component (b) can be easily dispersed in the thermoplastic elastomer of the block polymer (a) by using the above-mentioned various mixers, and a dispersion aid is not particularly required. Has the advantage. Therefore, the deterioration of the antistatic function with time can be prevented without impairing the properties of the thermoplastic elastomer of component (a). Moreover, since the component (b) is a pellet-shaped solid, it does not scatter like powder in the mixing or kneading step, and there is little fear of contaminating the work environment.

  The thermoplastic resin composition can be formed into an arbitrary shape by various conventionally known methods such as hot pressing, injection molding, extrusion molding, and blow molding. In this case, since no solvent is used in the manufacturing process, work environment and air pollution are not caused.

  The sealing member of the present invention is semipermanently antistatic because the conductive resin is kneaded and dispersed in the base material unlike the conventional surfactant or conductive carbon added antistatic agent. In addition to its long-lasting function, the antistatic function does not deteriorate due to friction, and it does not peel off.

  Moreover, in this invention, transparency and various coloring can be provided by selecting suitably the kind and compounding quantity of (a) component and (b) component, and the packaging member with a wide freedom degree of coloring. Can be obtained. For example, when a formulation that provides transparency is selected, it is possible to check the package contents not only from the packing case surface but also from the sealing member side. Moreover, it is also possible to make a mark by color-coding according to the kind of electronic component. Transparency is suitably imparted, for example, by using a thermoplastic elastomer (A) mainly composed of a hydrogenated block copolymer as the component (a).

  Therefore, the sealing member of the present invention is particularly preferably used as a plug for a resin packaging case used for the purpose of, for example, transferring an electronic component or an electronic substrate, or for automatic insertion by a cassette method into an assembly apparatus. The

  Here, examples of the sealing member include a quadrangular prism-shaped molded product having a side of 1 to 50 mm, and an extruded molded product having a fishbone-like cross-sectional shape in which folds of the same dimensions are overlapped. Such a molded product is suitably used as a plug for a packing case, particularly as a plug for a packing case for electronic components. Moreover, as a sealing member, various packing members, gasket members, etc. are mentioned as a suitable example besides the various stoppers of a packing case.

Examples In order to describe the present invention more specifically and in detail, examples are shown below, but the present invention is not limited to these examples.
In addition, the performance evaluation of the thermoplastic resin composition and sealing member obtained by this invention was performed by the method shown below. The thermoplastic resin composition is evaluated for hardness and electrical conductivity (volume resistivity), and an extruded product produced using this thermoplastic resin composition is mounted as a sealing member (plug) on a polycarbonate case. Then, the state of dust adhesion was observed and evaluated. The results are shown in Table 1.

<Evaluation of thermoplastic resin composition>
Using a twin screw extruder (caliber 46 mm, L / D = 46), each component was melt-kneaded at 200 ° C. according to the formulation shown in Table 1 and Table 2 to obtain a pellet-shaped thermoplastic elastomer composition. It was.

In Examples 1 to 3 and Comparative Examples 1 to 6 in Table 1, as the component (a), a hydrogenated block copolymer (i), an olefin elastomer (b), a mineral oil softener, an olefin resin ( As the component b), the following compounds were used as the compounding agents for the block polymer and the conductive pigment.
(A) Thermoplastic elastomer mainly composed of component hydrogenated block copolymer (A)
Hydrogenated block copolymer (styrene-ethylene / propylene-styrene triblock copolymer having a styrene content of 30% by weight, a number average molecular weight of 200,000 and a hydrogenation rate of 97%)
Mineral oil softener "Diana Process Oil PW-90" (trade name, manufactured by Idemitsu Kosan Co., Ltd.)
Paraffin-based process oil olefin-based resin “NOBATEC Polypropylene EA9” (trade name, manufactured by Nippon Polychem)
MFR: 0.5 g / 10 min Olefin-based thermoplastic elastomer (b)
"Santoprene 101-55" (trade name, manufactured by AES Japan)
(B) Component block polymer “Pelestat 300” (trade name, manufactured by Sanyo Kasei Kogyo Co., Ltd.) Block polymer obtained by esterification of

I) Hardness Using the thermoplastic resin composition shown in Table 1, an extruder tape (200 ° C.) was used to produce an extruded tape of 25 mm width × 2 mm thickness, and the type A durometer hardness was measured by a method in accordance with JIS K6253. . The extruder used was 40φ and L / D = 32.

II) Conductivity (volume resistivity)
Using the thermoplastic resin composition shown in Table 1, an extruded tape having a width of 25 mm and a thickness of 2 mm was produced with an extruder (200 ° C.), and the volume resistivity value of the obtained extruded tape was measured.

<Evaluation of sealing member>
III) Using a pellet-shaped thermoplastic elastomer composition obtained in the above <Evaluation of thermoplastic resin composition>, a single screw extruder equipped with an extrusion die for trapezoidal rods having an upper side of 3 mm and a lower side of 5 mm A rectangular cylinder having a length of 10 mm of a thermoplastic elastomer was produced at an extruder cylinder temperature of 200 ° C. to obtain a sealing member (plug). This sealing member is inserted into both ends of a 4 mm square cylinder made of polycarbonate containing electronic components, passed through the electronic component transfer line, and observed for dust adhesion on the surface of the sealing member after passing the process. did. At this time, workability when the sealing member was mounted was also evaluated. We also collected statistics on the number of malfunctions in electronic equipment incorporating electronic parts that were transferred in cases.

Examples 1 and 2
Each component was melt-kneaded at 200 ° C. according to the formulation shown in Table 1 using a twin-screw extruder (caliber 46 mm, L / D = 46) with the formulation shown in Table 1, and a pellet-shaped thermoplastic resin A composition was prepared. The dispersibility of the component (b) in the component (a) was extremely good. Using the obtained pellet compound, a test piece was prepared and evaluated according to the evaluation methods I), II) and III). An extruded product (sealing member) having flexibility and rubber elasticity and good surface properties was obtained. Also, the mounting operation of the sealing member was good. No dust adhered to the sealing member surface after passing through the transfer line. The removal workability of the sealing member was also good. In addition, the number of malfunctions of the electronic equipment incorporating the electronic parts transferred in the case was not 100/100. Further, the extruded product obtained in Example 1 was extremely transparent.

Comparative Examples 1 and 3
Various physical properties were evaluated in the same manner as in Example 1 with the formulation shown in Table 1. The extruded product obtained in Comparative Example 1 was extremely transparent. However, when the block polymer of the component (b) was not added, conductivity was not obtained, dust was often attached to the sealing member, and malfunctions of the electronic equipment were frequently generated.

Comparative Examples 2 and 4
Various physical properties were evaluated in the same manner as in Example 1 with the formulations shown in Tables 1 and 2. The dispersibility of the component (b) in the component (a) was extremely good. Further, the surface property and conductivity were good, and there was no problem with respect to the state of dust adhesion and the influence on the electronic equipment. However, the formulation in which the component (b) is added excessively lacks flexibility, and the workability at the time of mounting on the case as a sealing member and when removing it after transfer is very poor. Further, the extruded product obtained in Comparative Example 2 was inferior in transparency as compared with Example 1.

It is useful as a sealing member (plug, packing member, gasket member, etc.) that is excellent in sustainability of antistatic function, has very little adverse effect on electronic parts, etc., and has excellent rubber elasticity with a degree of freedom of coloring. In particular, it is useful as a plug for packaging cases of electronic components.

Claims (4)

(A) a thermoplastic elastomer composed of carbon atoms and hydrogen atoms, (b) a block polymer having a structure in which polyolefin blocks and hydrophilic polymer blocks are alternately bonded, and the weight ratio is (a) :( b ) = 100: Sealing made of a thermoplastic resin composition having a JIS K6253 type A durometer hardness of 90 degrees or less and a volume resistivity of 1 × 10 ¹² Ω · cm or less. Element. Hydrogenation obtained by hydrogenating a block copolymer in which the component (a) has a polymer block A composed of a vinyl aromatic compound in the molecule and a polymer block B composed of a conjugated diene compound The sealing member according to claim 1, which is a thermoplastic elastomer (A) mainly composed of a block copolymer. The sealing member according to claim 1, wherein the component (a) is an olefin-based elastomer (B). The sealing member according to any one of claims 1 to 3, wherein the sealing member is a plug of a packaging case for electronic components.