JP4741945B2 - Low dusting conductive fiber sheet - Google Patents

Description

  The present invention relates to a method for producing a fiber sheet coated with a conductive polymer such as polypyrrole for antistatic, and more particularly to a method for producing a sheet that generates less dust from the antistatic sheet in its use. Such a sheet is useful, for example, as a wiping cloth used in a clean room handling precision electronic components.

  For example, in a clean room that handles precision electronic components, it is necessary to remove dust adhered to a workstation or an article to be carried in using a wiping cloth in order to prevent dust from adhering to the component. Such wiping cloths are generally made of synthetic fibers, such as polyester, which are poor electrical conductors, and accumulate charge due to friction. Accumulated electrostatic discharges can damage the device even with slight discharges caused by static electricity in highly integrated parts such as LSIs and VLSIs. Several attempts have been reported to complex with molecules, typically polypyrrole.

JP-A-3-234871 JP-A-3-249272 JP-A-3-294579 JP-A-4-45929 JP-A-4-65577 JP-A-8-74193 JP-A-9-168497

  Conductivity imparting to the fiber sheet by compositing the conductive polymer is generally performed by polymerizing a monomer on the fiber sheet and covering the fiber at least partially with the conductive polymer. In the case of polypyrrole, the fiber sheet is immersed in the pyrrole monomer solution and held in that state, and then immersed in the oxidant and dopant solution, or the fiber sheet is immersed in a solution containing the oxidant and dopant, The liquid phase method in which the state is maintained and then immersed in the monomer solution to perform polymerization, and the fibrous sheet is impregnated with the oxidizer and dopant solution in advance, and the pyrrole monomer in the gas phase is brought into contact therewith to polymerize the monomer. One of the gas phase methods is employed. The vapor phase method has an advantage that conductive polymer particles grown to a nano-level size can be attached to the fibers constituting the sheet.

  Regardless of whether it is a liquid phase method or a gas phase method, the fiber sheet treated by the above method is likely to drop out of the conductive polymer as particles due to mechanical impact, and as such may itself become a dust source. all right. Therefore, an effective measure for reducing the dust generation of a fiber sheet coated with a conductive polymer, such as a wiping cloth, to a practically acceptable level is desired.

The present invention provides a fiber sheet coated with a conductive polymer that exhibits low dust generation. According to the present invention, a base sheet is pre-treated with a pyrrole monomer solution, and this is treated with an oxidant solution containing a dopant, thereby coating the base with a polypyrrole conductive polymer containing a dopant, or a dopant. The substrate is coated with a polypyrrole conductive polymer containing a dopant by pre-treatment with an oxidant solution containing and contacting it with a pyrrole monomer solution or vapor phase pyrrole monomer, and then the conductivity of the coating is increased. In order to prevent the molecules from falling off, a conductive polymer-coated fiber sheet with low dust generation is produced by treatment with a binder resin that enhances adhesion of the conductive polymer to the substrate. The fiber sheet treated in this way is coated with a conductive polymer at least partially coated thereon and a binder resin that reinforces the adhesion of the conductive polymer to the substrate. Desirably, one of the conductive polymer and the binder resin is a matrix, and the other is formed in a structure surrounded by the matrix so that the substrate is coated with both, and the treated substrate is 10 ¹¹ Ω / □. It is desirable to have a resistivity below the order. Low dust generation is obtained by appropriately controlling the pickup rate of the binder resin for the conductive polymer that is polymerized in the pyrrole monomer solution, but the conductive fiber sheet has lower dust generation. In order to achieve this, it is important to adopt a polymerization reaction of pyrrole monomer in the gas phase, to control the generated conductive polymer to be nano-sized, and to properly control the binder resin pickup rate It is.

  According to the present invention, the polymerization reaction is preferably controlled by adjusting the pH of the oxidant solution containing the dopant to a range of 4 to 9, or copolymerizing a pyrrole derivative having a polymerization reaction rate lower than that of pyrrole, or both. The control of the pickup rate can be achieved by adjusting the solid content of the binder resin used in solvent-type normally dry paints or emulsion-type or dispersion-type water-based paints. can do.

  Here, some terms used in the present application are defined.

  “Fiber sheet” refers to a sheet-like web composed of natural fibers, synthetic or semi-synthetic chemical fibers, and mixtures thereof. The structure or shape of the sheet is, for example, a woven fabric, a fabric such as a knit, a non-woven fabric, or a paper. In particular, the material intended for use in a wiping cloth that can be used in a class 100 ultra-clean room is preferably a fabric made from ultrafine fibers, typically ultrafine polyester fibers.

  “Polypyrrole” is not only a homopolymer of pyrrole but also a small proportion of pyrrole homologues or derivatives copolymerizable with pyrrole, such as N-methylpyrrole, 3-methylpyrrole, 3,5-dimethylpyrrole, 2,2 '-Refers to a copolymer with bipyrrole.

  “Oxidizing agent” refers to a chemical oxidizing agent capable of providing conductive polypyrrole by oxidative polymerization of pyrrole monomers. Specific examples of oxidizing agents that can be used are described in US Pat. Nos. It is described in a number of documents including 4,604,427, 4,521,450 and 4,617,228, ammonium persulfate, iron (III) chloride, iron (III) sulfate, hydrogen peroxide, perboric acid Including ammonium and copper (II) chloride. A sulfonic acid used as a dopant, for example, a ferric salt of paratoluenesulfone, can also be used as an oxidizing agent.

  "Dopant" refers to an anion that improves the conductivity of polypyrrole, examples of which are also described in numerous patent documents, including the aforementioned US patents. Preferred are sulfonic acids such as paratoluenesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, dodecylbenzenesulfonic acid, and sulfonated polystyrene.

  “Binder resin” refers to a resin component used as a film-forming resin in a normally dry water-based paint in the form of a solvent-type normally dry paint or emulsion or dispersion. Specific examples include vinyl resins including homo- or copolymers such as vinyl chloride, vinyl acetate, and vinylidene chloride, acrylic resins, polyester resins, epoxy resins, polyamide resins, fluororesins, and modified resins thereof. In consideration of the affinity, it is preferable to employ a polyester binder resin for a binder resin similar to the fiber constituting the substrate, for example, a polyester fiber. Polyurethane emulsions or dispersions have good adhesion to various types of fiber sheet substrates.

  Since the characterizing portion of the present invention does not exist in the material or structure of the fiber sheet serving as the substrate, it can be appropriately selected from the previously defined fiber sheets according to the purpose of use. Although the following description is mainly directed to the wiping cloth, those skilled in the art can easily determine the substrate to be used, the treatment agent, and the treatment conditions depending on the specific use purpose of the fiber sheet to which conductivity is imparted. It will be possible.

As described above, one of the important aspects of the present invention is that a fiber sheet coated with a conductive polymer produced in liquid and gas phase polymerization with a binder and imparted with conductivity having low dust generation property. There is in getting. More preferably, 90% or more of the primary particles are covered with a polypyrrole having a size of 100 nm or less by using gas phase polymerization. The polymerization reaction rate of the pyrrole monomer depends on the pH of the oxidant solution containing the dopant, and is usually controlled on the acidic side, particularly in the range of pH 1 to 3. According to a more preferred embodiment, the pH of this solution is controlled in the range of 3-11, more preferably pH 4-9. Among the oxidizers mentioned above, there are those in which the aqueous solution originally exhibits acidity, such as ferric chloride and ferric sulfate, and Fe ³⁺ ions cannot be stably present in the solution by neutralization. There is. In view of this, in this case, it is necessary to select an oxidizing agent that is stable at a pH of 4 to 9, such as ammonium persulfate and ammonium perborate. Another method for controlling the polymerization reaction rate is a method in which a comonomer having a slower reaction rate than pyrrole itself is copolymerized. For example, N-methylpyrrole is known to have a slower reaction rate than pyrrole. Therefore, a small proportion, for example, pyrrole containing 10 mol% or less of N-methylpyrrole is used for the polymerization reaction.

  The substrate is impregnated with an oxidant solution containing a dopant, and the impregnation can be performed by dipping, spraying, coating, or the like. It is desirable to squeeze the excess solution with mangle roll or the like. The concentrations of dopant and oxidant are not critical and are preferably 0.1 to 10%, preferably 0.5 to 5%, especially about 1%.

  Thus, the base material impregnated with the oxidizing agent solution containing a dopant is brought into contact with a pyrrole monomer in a gas phase in order to obtain a fiber sheet having lower dust generation properties, for example. The monomer contacts the substrate wetted with an oxidant solution containing a dopant, and forms a polypyrrole conductive polymer coating thereon. In this gas phase polymerization reaction, a base material impregnated with an oxidizing agent containing a dopant is put into a partitioned reaction chamber, into which monomer is introduced in a gas phase, and the state is maintained until the monomer no longer reacts. It can be implemented by leaving it to stand. In some cases, including the impregnation step, the gas phase polymerization reaction may be carried out continuously.

  Although the boiling point of pyrrole at atmospheric pressure is 130 ° C., it vaporizes in air until reaching the saturated vapor pressure even at a temperature lower than that. Therefore, an evaporator of liquid pyrrole is installed in the reaction chamber, vaporized pyrrole and liquid pyrrole are maintained in an equilibrium state, and a base material impregnated with an aqueous oxidizing agent solution containing a dopant is held in the atmosphere in this state. Alternatively, an evaporator containing liquid pyrrole can be installed outside the room, bubbled with an inert carrier gas such as nitrogen, and vaporized pyrrole can be supplied into the room together with the carrier gas. Regardless of where the evaporator is installed, the temperature of the liquid pyrrole may be in the range of 5 ° C to 100 ° C, preferably 20 ° C to 50 ° C, particularly preferably room temperature. Unlike the liquid phase method, the gas phase method has a limited amount of oxidant required for the reaction, and therefore it is not necessary to strictly control the reaction time.

The oxidative polymerization of pyrrole reaches equilibrium as the oxidant contained in the impregnated substrate is consumed and stops spontaneously. By such treatment, the surface resistivity of the fiber sheet can be reduced to the order of 10 ¹¹ Ω / □ or less. If the resistivity does not reach this value, the impregnation and gas phase polymerization steps described above can be repeated until the desired resistivity is reached. The treated substrate is washed to remove the remaining dopant and used in the next step.

  The adhesion rate of the conductive polymer, that is, the weight% of the conductive polymer with respect to the substrate before treatment varies greatly depending on the properties of the substrate, particularly the specific surface of the substrate, but is generally 0.1 to 5%. I will.

  Thus, the conductive polypyrrole adhering to the base material falls off from the base material due to mechanical impact, and can itself become a source of dust. The present invention therefore uses a binder resin to enhance the adhesion of the conductive polymer to the substrate. As described above, it is important to appropriately control the pickup rate of the binder resin in this case, that is, the weight percentage of the binder resin in terms of solid content with respect to the base material. This pickup rate is also related to the adhesion rate of the conductive polymer previously deposited. In other words, it should not be so large that the resistivity of the substrate coated with the conductive polymer in the previous step is increased to a resistivity higher than the desired level, and on the contrary, the adhesion of the conductive polymer to the substrate is significantly increased. The amount should not be insufficient to strengthen. This pickup rate varies greatly depending on the material and structure of the specific base material to be used, the affinity of the specific binder resin for the base material, etc., but generally 0.01 to 2.0 relative to the base material as a solid content. Within the weight percent range, the ratio of binder resin to conductive polymer will be within the range of 0.01 to 3.00, preferably 0.1 to 1.0.

  Such control of the pickup rate of the binder resin can be easily achieved by using an emulsion or dispersion of the binder resin. In this case, the solid content concentration of the emulsion or dispersion is diluted to 5% or less, for example, 1% with water, and the substrate obtained in the previous step is immersed in this, and optionally the excess liquid is squeezed out and then dried. Shipped as a final product. If the pick-up rate is insufficient, dipping and drying may be repeated again. Although it is a suboptimal method, the adhesion of the conductive polymer to the substrate can be strengthened by spraying an organic solvent solution of a binder resin such as a solvent-type ordinary dry paint. The pickup rate in this case can be controlled by adjusting the resin solid content concentration of the solution and / or the spray amount per unit area.

  The following examples and comparative examples are not intended to be limiting, and “parts” and “%” are by weight unless otherwise specified.

  The surface resistivity was measured using a surface resistance meter HIRESTA-UP MCP-Hi450 manufactured by Mitsubishi Chemical Corporation.

  The number of departicles was measured using a particle counter KM-33 manufactured by Rion. The measurement conditions were based on the standard tumbler method of US IES-RP-CC-003, measured on five 24 × 24 cm samples, and the average value of five points was obtained as the number of generated particles per sheet.

  The observation of the polypyrrole particle diameter on the fiber sheet substrate was performed using a scanning probe microscope NANO-R stage manufactured by Pacific Nanotechnology.

Example 1
A polyester nonwoven fabric having a width of 24 cm, a length of 120 cm, a thickness of 0.7 mm, and a basis weight of 100 g / m ² excluding the margin is dipped in an aqueous solution (pH 1.40) of 1% ammonium persulfate and 1% paratoluenesulfonic acid to make mangles. Excess solution was removed. Thereafter, the wet nonwoven fabric was flattened and placed in the reaction chamber. The vapor of pyrrole was filled into the chamber from an evaporator installed in the chamber, and left for 1 hour for vapor phase polymerization of pyrrole. After completion of the reaction, the nonwoven fabric was taken out from the reaction chamber, washed 3 times with 10 L of distilled water, drained, immersed in a 1% polyester aqueous dispersion for 1 minute, drained, and dried at 105 ° C. for 1 hour. From the weight difference before and after the treatment, the polypyrrole adhesion rate and the binder polyester resin pickup rate were calculated to be 1.0% and 0.2%, respectively.

The obtained non-woven fabric was cut into 5 sheets of 24 × 24 cm size with a margin, and the average surface resistivity of 5 sheets and the average number of departicles of 5 sheets were measured and found to be 2 × 10 ⁶ Ω / □ and 78, respectively. It was a piece / sheet. The non-conductive non-woven fabric and the average number of departicles measured by the same measurement were 75 / sheet.
Moreover, when the primary particle diameter of the polypyrrole of the location where the binder is not adhered was observed, 90% or more was 10-50 nm in size.

Example 2
The operation of Example 1 was repeated except that the base material was changed to a polyester woven fabric having a basis weight of 100 g / m ² . The average surface resistivity and average departicle number of the obtained polyester were 1 × 10 ⁵ Ω / □ and 40 / sheet, respectively. The conductive untreated woven fabric and the average number of departicles measured by the same measurement were 37 / sheet.
The adhesion rate of polypyrrole and the pickup rate of binder polyester resin were calculated as 0.8% and 0.2%, respectively.
Moreover, when the primary particle diameter of the polypyrrole of the location where the binder is not adhered was observed, 90% or more was 10-50 nm in size.

Example 3
The procedure of Example 1 was repeated except that the polymerization method was changed from gas phase polymerization to in-solution polymerization in which the polymer was immersed in a 20% ethanol solution of pyrrole monomer for 10 minutes.
The average surface resistivity and average departicle number of the obtained polyester were 3 × 10 ⁵ Ω / □ and 95 / sheet, respectively.
The adhesion rate of polypyrrole and the pickup rate of binder polyester resin were calculated as 1.7% and 0.3%, respectively. Moreover, when the primary particle diameter of the polypyrrole of the location where the binder has not adhered is observed, 90% or more was 10-80 nm in size.

Example 4
The procedure of Example 2 was repeated except that the oxidant-impregnated solution containing the dopant was changed to an aqueous solution adjusted to pH 9.0 with 1% ammonium persulfate, 1% paratoluenesulfonic acid, and ammonia. The obtained polyester woven fabric had an average surface resistivity and an average number of departicles of 7 × 10 ⁵ Ω / □ and 33 / sheet, respectively.
The adhesion rate of polypyrrole and the pickup rate of binder polyester resin were calculated as 0.8% and 0.2%, respectively.
Moreover, when the primary particle diameter of the polypyrrole of the location where the binder has not adhered is observed, 90% or more was 10-40 nm in size.

Comparative Example 1
The base material is changed to a polyester woven fabric with a basis weight of 50 g / m ² , the impregnation solution is changed to an aqueous solution adjusted to pH 0.3 with 1% ammonium persulfate, 1% paratoluenesulfonic acid and sulfuric acid, and immersed in an aqueous polyester dispersion. The procedure of Example 1 was repeated except that there was not. The obtained polyester woven fabric had an average surface resistivity and an average number of departicles of 1 × 10 ⁷ Ω / □ and 234 pieces / sheet, respectively.

Comparative Example 2
The procedure of Example 1 was repeated except that the binder resin dispersion was changed to a 7% polyester dispersion. The average surface resistivity and average departicle number of the obtained polyester nonwoven fabric were 3 × 10 ¹² Ω / □ and 24 / sheet, respectively.
The adhesion rate of polypyrrole and the pickup rate of binder polyester resin were calculated to be 1.0% and 3.5%, respectively.

Claims (4)

The fiber sheet base material is coated with a conductive polymer composed of polypyrrole containing at least a dopant, and the pickup ratio of the binder resin is in the range of 0.01 to 2.0% by weight with respect to the base material as a solid content. The binder resin contained inside strengthens the adhesion of the conductive polymer to the substrate, and the surface resistivity of the sheet substrate is less than the order of 10 ¹¹ Ω / □. Fiber sheet.
The fiber sheet according to claim 1, wherein the surface resistivity is not more than the order of 10 ⁹ Ω / □.   The fiber sheet according to claim 1 or 2, wherein the coating with the conductive polymer is performed by gas phase polymerization of a pyrrole monomer on a substrate impregnated with an oxidizing agent solution containing a dopant.   The fiber sheet according to any one of claims 1 to 3, which is a wiping cloth.