JP4701870B2 - paper - Google Patents

Description

  The present invention relates to a polyphenylene sulfide oxide nanofiber, and a paper made of the same and having excellent heat resistance and chemical resistance having almost no coarse voids or pinholes in paper.

  Polyarylene sulfide fibers (PPS fibers) are widely known as fibers excellent in heat resistance and chemical resistance. Conventionally, it has been proposed to obtain polyarylene sulfide oxide fibers (PPSO fibers) by oxidizing PPS fibers (see Patent Documents 1 and 2). The PPSO fiber is a fiber having excellent heat resistance, chemical resistance, particularly acid resistance, and excellent heat resistance, as compared with the PPS fiber. However, in the above prior art, although there is a description regarding a sheet-like material using PPSO fibers, there is no indication as to being suitable for a paper application used for an electrical insulating material or the like.

  Further, the present invention relates to a paper having excellent heat resistance and chemical resistance made of polyphenylene sulfide nanofibers and having almost no coarse voids or pinholes in paper, and tow and short fiber bundles and pulp and liquid dispersions as raw materials thereof. The thing is also proposed conventionally (refer patent document 3). However, although it describes a non-woven fabric by a wet papermaking method, it does not show anything about the use of an electrical insulating material or the like, and further does not show any PPSO fiber having heat resistance exceeding that of polyphenylene sulfide fiber.

  As electrical insulating materials used in motors and transformers, many papers manufactured by wet papermaking, such as paper made of cellulose, are used. In particular, paper made of meta-aramid is often used for electrical insulating materials used at high temperatures. Since paper used at this high temperature is required to have heat resistance and chemical resistance, paper made of PPS fibers is a suitable material for basic performance. However, paper made of PPS fibers has not yet been used as an electrical insulating material used at high temperatures. This is because paper for electrical insulation requires a dense and small pore size paper structure to improve electrical insulation, and to prevent insulation degradation due to pinholes in high temperature environments. It was necessary to use a polymer having substantially no melting point. That is, there is a problem that even if a PPS fiber having a melting point and a nanofiber made of PPS are used, the high-performance electric insulation which is the object of the present invention is not exhibited. Furthermore, even if PPSO fiber is simply used, a large pore size is generated.

As described above, it has been difficult to obtain a fine paper having a small pore size by a conventionally known technique.
JP-A-53-182413 Japanese Patent Laid-Open No. 03-260177 JP 2004-162244 A

  An object of the present invention is to solve the above-mentioned problems of the prior art, and is a paper using PPSO nanofibers and heat resistance and chemical resistance thereof, and a paper that is dense and has a small pore size. It is to provide. Furthermore, it is providing the heat resistant paper suitable for the electrical insulating material using the heat resistance and chemical resistance of PPSO fiber paper.

In order to solve the above problems, the present invention has the following configuration. That is,
(1) Poly having a fiber diameter of 0.0001 μm or more and 0.3 μm or less, a fiber length of 10 mm or less, and a melting peak is substantially not observed in a differential scanning calorimeter (DSC) measurement. Containing polyarylene sulfide oxide fibers containing arylene sulfide oxide nanofibers, fiber length of 10 mm or less, fiber diameter of 10 μm or more and 30 μm or less , calendering under conditions of temperature of 100 ° C. or more and load of 1 kN / 25 cm or more carried out, the resulting feature a Rukoto and be Lupe supermarkets.
(2) The paper according to (1) , wherein the polyarylene sulfide oxide nanofiber is 30 to 70% by weight and the polyarylene sulfide oxide fiber is 70 to 30% by weight.
Consists of

  According to the present invention, not only polyarylene sulfide oxide nanofibers excellent in heat resistance and chemical resistance, and papers made thereof, but also high density papers and electrical insulating materials can be obtained.

  Hereinafter, the present invention will be further described in detail.

  In the present invention, points for achieving the above-described problems are as follows. That is, even if the PPS fiber is beaten, it is thermoplastic and has flexibility, so that the cross section of the fiber is deformed and crushed, and it does not become a pulp state having a branched structure or a fibril structure. Discovered that a PSO fiber can be used as a pulp substitute material by converting it into a nanofiber or a precursor thereof and then oxidizing it into a PPSO nanofiber having substantially no melting point.

In the present invention, PPSO means
The following general formula (1)

(R ″ represents hydrogen, halogen, an aliphatic substituent substituted with an arbitrary functional group within an allowable range of valence, or an aliphatic substituent substituted with an aromatic substituent. R ″ may be linked to each other to form a crosslinked structure. R ″ may be a polymer chain composed of PPSO. R ′ ″ represents a polymer chain composed of PPSO, and m is any of 0-3. X represents 0, 1, or 2), or the repeating unit as a main structural unit and 1 per mole of the repeating unit. 0.0 mol or less, preferably 0.3 mol or less of the general formulas (2) to (8)

(R ″ represents any one of hydrogen, halogen, an aliphatic substituent substituted with an arbitrary functional group within an allowable range of valence, and an aliphatic substituent substituted with an aromatic substituent; "Represents an aliphatic substituent substituted with an arbitrary functional group within an allowable range of valence, and R or R 'between molecules may be linked to each other to form a crosslinked structure. , R ″, R ″ ″ may be a polymer chain composed of PPSO. R ′ ″ represents a polymer chain composed of PPSO, m represents an integer of 0 to 3, and n represents any of 0 to 2 X represents an integer of 0, 1, or 2) and is a solid article made of a copolymer consisting of a repeating unit represented by general formula (1). Of which X is 0, 1, or 2 and X is 1 or The ratio of the structural unit of 2 is preferably 0.5 or more and 0.9 or less, more preferably 0.7 or more and 0.9 or less.

  In the present invention, the PPSO nanofiber is a nanofiber shaped article composed of the PPSO described above.

  It is important that the PPSO nanofiber of the present invention has a fiber diameter of 0.0001 μm or more and 0.3 μm or less. When the fiber diameter exceeds 0.3 μm, voids tend to increase when paper is used, and when the fiber diameter is less than 0.0001 μm, the handleability becomes very poor.

  In addition, it is important that the PPSO nanofiber of the present invention does not substantially have a melting peak in a differential scanning calorimeter (DSC) measurement. Specifically, the fact that the melting peak is not substantially observed means that PPSO having a heat of fusion of 15 J / g or less, preferably 10 J / g or less, more preferably 5 J / g or less, particularly preferably 1 J / g or less. In this range, it has particularly excellent characteristics regarding heat resistance and chemical resistance. This is an important factor not only for maintaining sufficient heat resistance as a heat-resistant paper but also for preventing the occurrence of pinholes due to melting.

  Here, the DSC measurement conditions were as follows: a nitrogen flow rate of 20 mL / min and a differential scanning calorimeter (DSC manufactured by PerkinElmer Co., Ltd.), a sample amount of 5 mg to 10 mg, and a temperature program of 30 ° C. to 500 ° C. This is the heat of fusion when measured at a temperature of 30 ° C. (temperature increased from 30 ° C. to 340 ° C. at a temperature increase of 10 ° C./min).

  The cross-sectional shape of the PPSO nanofiber is not particularly limited, and is not limited to a normal circular cross-section, but any irregular cross-section such as a Δ cross-section, a Y-shaped cross-section, a □ cross-section, a cross-section, a hollow cross-section, a C-shaped cross-section, Can also be adopted.

  Examples of the method for obtaining the PPSO nanofibers of the present invention include a method in which PPSO is dissolved in an appropriate good solvent and a conventionally known nanofiber manufacturing technique such as an electrospinning method is used, and a method in which PPS nanofibers are oxidized. However, it is preferably obtained by oxidizing nanofibers made of a PPS compound from the viewpoint of ease of production.

  For example, polyphenylene sulfide oxide nanofibers are melt blended with polyphenylene sulfide and other appropriately selected thermoplastic polymers, melt spun to produce nanofiber precursors, and then the other thermoplastic polymers are eluted and removed. Thus, polyphenylene sulfide nanofibers are obtained, and the nanofibers are oxidized to produce polyphenylene sulfide oxide nanofibers. At this time, it can also be produced by elution and removal of the other thermoplastic polymer after oxidation in the state of the nanofiber precursor.

  When the other thermoplastic polymer is melt-blended with PPS, the PPS in the fiber is finely dispersed in the form of streaks in the fiber axis direction from about 0.0001 μm to 0.3 μm, and can be made into fibers. Select that elution is possible. Specific examples include polyesters, polyamides, polystyrenes, polyvinyl alcohols, etc. Among them, the production of the precursor by forming a polyester, particularly polyethylene terephthalate having a viscosity ratio with PPS of 1/10 to 10 near the melt spinning temperature. This is preferable because of improved properties.

  Moreover, the PPS compound said here is general formula (9).

(R represents at least one of hydrogen, halogen, an aliphatic substituent substituted with an arbitrary functional group within an allowable range of valence, and an aliphatic substituent substituted with an aromatic substituent. ) Or a repeating unit represented by formula (10) to (16) having a repeating unit of 1.0 or less, preferably 0.3 or less, per mole of the repeating unit. )

(R represents hydrogen, halogen, an aliphatic substituent substituted with an arbitrary functional group within an allowable range of valence, or an aliphatic substituent substituted with an aromatic substituent, and R ′ represents Represents an aliphatic substituent substituted with an arbitrary functional group within an allowable range of the valence.)).

  Among them, the substituents R and R ′ are preferably hydrogen or an aliphatic substituent having 1 to 4 carbon atoms. Specific examples thereof are hydrogen, methyl group, ethyl group, n-propyl group, iso-propyl group, and n-butyl group. , Iso-butyl group, and tert-butyl group. Among them, a methyl group, an ethyl group, an iso-propyl group, and a tert-butyl group are preferable, and a methyl group is more preferable. Specific examples of the PPS compound include poly-p-phenylene sulfide, poly-p-tolylene sulfide, poly-p-chlorophenylene sulfide, poly-p-fluorophenylene sulfide and the like. P-phenylene sulfide and poly-p-tolylene sulfide are preferable, and poly-p-phenylene sulfide is more preferable.

  Further, the PPS compound nanofiber or the precursor thereof preferably has physical properties of a crystallinity of 20% to 70% and a weight average molecular weight of 30000 (Mw) to 80000, and the crystallinity is 40% to 70%. % Is more preferable, and the weight average molecular weight is more preferably 40000 (Mw) or more and 80000 or less. Here, the degree of crystallinity is a value calculated from the peak area ratio derived from the crystalline structure in the total diffraction peak area, which is observed in the wide-angle X-ray diffraction measurement. For example, it can be calculated from the peak area ratio derived from the crystalline structure when a fiber sample is measured with a Cu line source (λ = 1.5406 Å) using a wide-angle X-ray diffractometer (RINT2100: Rigaku). it can. The weight average molecular weight can be obtained by, for example, dissolving and measuring in 1-chloronaphthalene at 210 ° C. using a gel permeation chromatograph (GPC220). By setting the weight average molecular weight to 30000 or more, it is possible to obtain a nanofiber having a strength capable of maintaining the shape in the subsequent step, and by setting it to 80000 or less, the spinnability when obtaining the precursor fiber is improved. When the PPS compound nanofiber or precursor thereof in this range is used, the crystallinity and molecular weight of the PPS compound nanofiber are not greatly impaired even in the oxidation reaction treatment, and the physical properties of the resulting PPS nanofiber are good. PPS compound nanofibers having such crystallinity and weight average molecular weight can be obtained, for example, by the following method.

  That is, when polyphenylene sulfide having a weight average molecular weight of 30000 (Mw) or more and 80000 or less is obtained, sodium acetate is used as a polymerization aid used in polymerization using sodium hydrosulfide as a sulfur source and p-dichlorobenzene as an organic monomer. And the polymerization aid is polymerized for about 4 hours under the condition that the excess ratio of p-dichlorobenzene to sodium hydrosulfide is 2.0 mol% or more using 0.04 times mol or more of sodium hydrosulfide. Obtainable.

  In addition, when obtaining a PPS compound nanofiber having a crystallinity of 20% to 70%, or 40% to 70%, blend spinning with other finely dispersible thermoplastic polymer and drawing by a known method It is obtained by controlling the speed, draw ratio, or heat treatment conditions after drawing, and then eluting and removing other thermoplastic polymers.

  In the present invention, the liquid of the reaction solvent used for the oxidation reaction treatment can be arbitrarily used as long as it retains the form of the PPS compound nanofiber or its precursor, and an oxidizing agent used for the oxidation reaction treatment is used. It is preferable that it dissolves uniformly. Among them, a liquid containing an organic acid, an organic acid anhydride, or a mineral acid is preferable. The liquid may be either a single solvent or a mixed solvent, and may contain water or a liquid containing water alone. Specific examples of the liquid include water, acetone, methanol, ethanol, acetonitrile, tetrahydrofuran, chloroform, N-methylpyrrolidone, ethyl acetate, pyridine, organic acids and organic acid anhydrides described later. Specific examples of the organic acid include formic acid, acetic acid, trifluoroacetic acid, propionic acid, butyric acid, maleic acid and the like. As the organic acid anhydride, the following general formula (a)

(R ¹ and R ² each represent an aliphatic substituent having 1 to 5 carbon atoms, an aromatic substituent, or an aliphatic substituent substituted with an aromatic substituent, and R ¹ and R ² are And may be linked to form a cyclic structure.), And specific examples thereof include acetic anhydride, trifluoroacetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, and succinic anhydride. , Phthalic anhydride, benzoic anhydride, and anhydrous chlorobenzoic acid. Specific examples of the mineral acid include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and the like. Preferred oxidizing agents are water, acetic acid, trifluoroacetic acid, acetic anhydride, trifluoroacetic anhydride, sulfuric acid, and hydrochloric acid, and more preferred are water, acetic acid, trifluoroacetic acid, and sulfuric acid. Particularly preferred is a liquid in which water and acetic acid and sulfuric acid are mixed. More preferable composition ratios are: water: 5 to 20% by weight, acetic acid: 60 to 90% by weight, and sulfuric acid: 5 to 20% by weight. Good results are obtained at concentrations in this range.

  The oxidizing agent used in this reaction can be arbitrarily used as long as it dissolves uniformly in the liquid and gives PPSO nanofibers having the characteristics defined in the present invention. In particular, a combination of an oxidizing agent and a liquid that can be oxidized while maintaining the shape of the PPS nanofibers is preferable. The oxidizing agent is preferably at least one selected from inorganic salt peroxide and hydrogen peroxide solution, and one or more selected from inorganic salt peroxide and hydrogen peroxide solution, and organic acid and organic acid It may be a peroxide (including a peracid) formed from a mixture with one or more selected from anhydrides.

  Preferred examples of the inorganic salt peroxide used as the oxidizing agent include persulfates, perborates, and percarbonates. Here, examples of the salt include alkali metal salts, alkaline earth metal salts, ammonium salts, and the like, among which sodium salts, potassium salts, and ammonium salts are preferable. Specific examples thereof include sodium persulfate, potassium persulfate, ammonium persulfate as persulfates, sodium perborate, potassium perborate, ammonium perborate as perborate, and percarbonate as percarbonate. Examples thereof include sodium and potassium percarbonate. Specific examples of peracids formed from a mixture of hydrogen peroxide and an organic acid or organic acid anhydride include performic acid, peracetic acid, trifluoroperacetic acid, perpropionic acid, perbutyric acid, perbenzoic acid, m-chloroperbenzoic acid and the like can be mentioned, among which sodium persulfate, sodium perborate, performic acid, peracetic acid and trifluoroperacetic acid are more preferable, and sodium perborate and peracetic acid are more preferable. Trifluoroperacetic acid.

  The concentration of the oxidizing agent is important for safety management in the industrial production process, and a higher concentration is preferable from the viewpoint of processing efficiency. However, from the viewpoint of the form and apparent volume of the solid article made of PPS compound nanofibers, the solid article Can be sufficiently immersed in a liquid containing an oxidizing agent, and can be diluted with a liquid or reduced in terms of safety if the concentration is such that PPSO nanofibers in the range specified in the present invention can be obtained. Arbitrarily possible.

  The concentration of peracid in the present invention is preferably 20% by weight or less, more preferably 0.1% by weight to 10% by weight, and further preferably 3 to 8% by weight. A good reaction result can be obtained at a concentration within this range, and a highly safe process can be constructed. If it is higher than this, its stability and safety are very sensitive to temperature. In particular, a high concentration of peracid exceeding 20% by weight is not preferable because it is difficult to control its stability and process safety. .

  When inorganic salt peroxide is used as the oxidant, dilute with solvent from the PPS compound nanofiber or its precursor fiber form, apparent volume, etc. to a concentration that can be sufficiently immersed, or reduce the concentration for safety reasons. Is arbitrarily possible. Preferably they are 0.1 weight%-10 weight%, More preferably, they are 3 weight%-8 weight%.

  When a peracid or peroxide formed from a mixture of hydrogen peroxide and an organic acid is used, the concentration of the peracid or peroxide is preferably 10% by weight or less.

  When a peracid or peroxide formed from a mixture of hydrogen peroxide and an organic acid anhydride is used, the concentration of the peracid or peroxide is preferably 0.1% by weight to 20% by weight, more preferably Is 3 to 15% by weight, particularly preferably 3 to 8% by weight.

  It is possible to construct a process that gives good reaction results at a concentration in the above range and is highly safe. If it is higher than this, its stability and safety are very sensitive to temperature. In particular, a high concentration of peracid exceeding 20% by weight is not preferable because it is difficult to control its stability and process safety. .

  For example, using a differential scanning calorimeter (DSC manufactured by PerkinElmer Co., Ltd.), the sample amount is weighed within a range of 5 mg to 8 mg in an air atmosphere, and the temperature program is performed in a stainless steel 4.9 MPa (50 atm) pressure-resistant sealed container. The thermal behavior of the peracetic acid solution when measured at a temperature of 30 ° C to 200 ° C (from 30 ° C to 200 ° C with a temperature increase of 10 ° C / min) is the decomposition temperature in the case of a 40% peracetic acid solution. 110 ° C., calorific value 770 J / g, equilibrium peracetic acid prepared with equal weight of acetic acid and 34.5% hydrogen peroxide solution to a theoretical peracetic acid concentration of 40% is decomposition temperature 133 ° C., calorific value 704 J In contrast to a liquid mixture prepared by equimolar use of acetic anhydride and 34.5% hydrogen peroxide solution to a theoretical peracetic acid concentration of 40%, the decomposition temperature is 132 ° C. and 445 J / g, which is about 60%. The calorific value of , 9% of which decomposition temperature 110 ° C., a heat value of 1 of 230J / g and about 3 minutes, very small. Therefore, it is very important to ensure the safety of the oxidation reaction treatment process by reducing the oxidant concentration.

  The present oxidation reaction treatment is not particularly limited as long as PPSO nanofibers having the characteristics defined in the present invention are obtained, but it is preferably performed at a temperature below the boiling point of the liquid used. When the temperature is higher than the boiling point, the system is pressurized, the decomposition of the oxidant is often promoted and complicated equipment is required, and strict process management tends to be required in terms of safety. The specific oxidation reaction treatment temperature varies depending on the boiling point of the liquid to be used, but is within the range allowed by the boiling point of the liquid, preferably between 0 ° C. and 100 ° C., more preferably between about 30 ° C. and 80 ° C., particularly 40 ° C. ~ 70 ° C is preferred. For example, when the liquid is acetic acid, an oxidation reaction treatment temperature of 50 ° C. to 70 ° C. is preferable, and good reaction results are obtained at temperatures in this range.

  The oxidation reaction treatment time is not particularly limited as long as PPSO nanofibers having the characteristics defined in the present invention can be obtained, and the specific time depends on the reaction temperature and the concentration of the oxidizing agent, but cannot be said unconditionally. For example, when the liquid is acetic acid, it is about 2 hours at 60 ° C. and 10 wt% oxidizing agent concentration.

  Further, it is usually about 1 to 8 hours at an oxidizing agent concentration of 5% by weight under a condition of 60 ° C. Further, when a peracid formed from a mixture of an acid anhydride represented by the general formula (a) and hydrogen peroxide is used as an oxidizing agent, the oxidation reaction treatment is efficiently performed in a short time while ensuring safety. It is preferable. For example, in order to oxidize any of fiber bundles, fabrics, and felts using equilibrium peracetic acid prepared with equal weight of acetic acid and 34.5% hydrogen peroxide water to a theoretical peracetic acid concentration of 40% Is about 8 hours under a temperature condition of 60 ° C., whereas that of a mixed liquid prepared by using an equal weight of acetic anhydride and 34.5% aqueous hydrogen peroxide to a theoretical peracetic acid concentration of 40% is about 2 Time and very efficient.

  Although there is no restriction | limiting in particular in the processing system for performing this oxidation reaction process, A batch type, a continuous type, or what combined them can also be employ | adopted, and it can employ | adopt either a single stage process or a multistage process.

  Here, the batch type means that a PPS compound nanofiber and a liquid containing an oxidizing agent are put into an arbitrary reaction vessel, and after an oxidation reaction treatment at an arbitrary concentration, temperature, and time, the PPSO nanofiber or liquid is taken out. A continuous system means a system in which a nanofiber composed of a PPS compound or a liquid containing an oxidizing agent is allowed to flow through the reaction vessel with an arbitrary flow rate and is subjected to an oxidation reaction treatment. In the continuous type, a method of performing an oxidation reaction treatment by circulating or circulating a liquid containing an oxidant on a nanofiber made of a PPS compound immobilized in an arbitrary form, or an arbitrary liquid containing an oxidant Any of the methods in which the nanofibers made of PPS compound are continuously circulated or circulated therethrough to be subjected to an oxidation reaction treatment.

  Further, the multistage process means a process in which unit processes of oxidation reaction treatment adopting a batch type or a continuous type are constructed in a plurality or in stages. Specifically, the oxidation reaction treatment is divided into a plurality of times, and when each treatment is performed, a method of newly preparing a liquid containing an oxidant for performing the oxidation reaction treatment and performing the subsequent oxidation reaction treatment is exemplified. . Such a method is preferable in that the oxidation reaction can be promoted. Specifically, it is preferably used in that the oxidation reaction treatment time can be shortened and the reaction can be performed at a lower temperature. In particular, the oxidation reaction treatment time that can be generated by diluting with a liquid so that it is sufficiently immersed or reducing the concentration to ensure safety, due to the influence of the form and apparent volume of nanofibers composed of PPS compounds This multi-stage process is preferable in that it can suppress the extension of temperature and eliminate the need for excessive temperature rise. By adopting this process, safety is ensured without extending the oxidation reaction time and temperature rise. Process construction.

  Furthermore, in the oxidation reaction treatment, PPS can be present as a nanofiber precursor, nanofiber itself, or a mixture with other fibers, etc., and may be either short fibers or long fibers. Or a non-woven fabric such as felt or paper. Moreover, as a method of contacting with an oxidant during the oxidation treatment reaction, either a method of immersing these fibrous materials in an oxidant or a method of spraying or spraying a liquid containing the oxidant can be employed.

  As described above, PPSO nanofibers obtained by oxidizing nanofibers composed of PPS compounds will be described in more detail.

  The cross-linking generated in the oxidation reaction process in the present invention means that a crosslinked structure is formed between polymer molecules in the process of oxidizing the PPS compound, and carbon atoms and sulfur atoms contained in the structure of the repeating unit. This means that atoms selected from any one of oxygen atoms are combined to form a bridge structure. In addition, the degree of cross-linking can be partly understood by solid-state NMR analysis and differential thermogravimetric (TGA) measurement of the PPSO nanofibers. In particular, in TGA measurement, after thermogravimetric change evaluation in a nitrogen atmosphere, By measuring the amount of remaining carbide, it is possible to grasp the ratio of the crosslinked structure between carbon atoms in the crosslinked structure. For example, using differential thermal weight (DTG-50: Shimadzu Corporation), a sample amount of about 10 mg is precisely weighed in a nitrogen atmosphere, and a temperature program is set to 30 ° C. to 900 ° C. (from 30 ° C. to 10 ° C. on a platinum cell container). The amount of remaining carbide when measured with a temperature increase of 900 ° C./min. Is measured almost quantitatively by PPS fiber (Torucon (registered trademark), polyarylene sulfide fiber manufactured by Toray Industries, Inc.). In the example of PPSO fiber (polyarylene sulfide oxide fiber) obtained after the oxidation treatment, 13.2% by weight of carbide remains, and the crosslinked structure of carbon atoms is obtained by the oxidation treatment. Can be confirmed. The PPSO fiber preferably has substantially no residual carbide in this TGA measurement, more preferably has a residual carbide amount of substantially 1% by weight or more, and in particular, substantially 5% by weight or more. It is preferable to have a residual carbide content. Within this range, it has particularly excellent characteristics regarding heat resistance and chemical resistance. The term “substantially” as used herein means the weight% of the amount of residual carbide after measurement with respect to the weight of PPSO fiber before measurement in the differential thermal weight (TGA) measurement.

  Moreover, the PPSO nanofibers obtained by this oxidation treatment have crystallinity. That is, the crystallinity in the measurement of wide-angle X-ray diffraction is preferably 10% or more and 80% or less, more preferably 30% or more and 80% or less, and more preferably 50% or more and 70% or less. By setting the crystallinity within the above range, the fiber has a balance between tensile strength and brittleness.

  In the present invention, the crystallinity of PSO nanofibers is selected from PPS nanofibers having a relatively high molecular weight and molecular weight used for the oxidation reaction, and the oxidation conditions that do not excessively impair the crystallinity of the PPS nanofibers are selected. It is possible to increase it.

  The PPSO nanofibers thus obtained have the heat resistance and chemical resistance, particularly acid resistance, higher than that of PPS fibers, and have the characteristics that the melting point substantially disappears and does not melt by heat. Therefore, a good paper with improved performance can be obtained.

  In general paper, the gap between the fibers is large, and the gap has electrical insulation and heat resistance. Therefore, in the paper of the present invention, the fiber diameter is 0.0001 μm or more and 0.3 μm or less, and the differential It is important to contain PPSO nanofibers in which a melting peak is substantially not observed in a scanning calorimeter (DSC) measurement. By containing PPSO nanofibers, not only can the gap between fibers be filled to improve electrical insulation, but also the chemical resistance and heat resistance of the paper itself can be improved.

  At this time, in order to more closely fill the inter-fiber gap, the fiber length of the PPSO nanofiber is preferably 0.001 mm or more and 10 mm or less, more preferably 0.01 mm or more and 5 mm or less. If the fiber length is long, the nanofibers are easily entangled and cannot be finely dispersed, and the voids cannot be filled. If the fiber length is short, the fibers are easily dropped from the interfiber spaces. As a result, the electrical insulation cannot be improved.

  Furthermore, in order to further improve chemical resistance and heat resistance without lowering the tensile and tear strength of the paper, not only PPSO nanofibers but also PPSO having a fiber length of 0.001 mm to 10 mm and a fiber diameter of 10 μm to 30 μm. It is preferable to contain a fiber. Not only can a high-performance paper be obtained by a combination of a cut fiber responsible for maintaining the shape of the paper and a nanofiber that fills the gap and improves electrical insulation, but by using PPSO for the cut fiber and nanofiber, The feature of substantially not having a melting point, which is a feature, can be effectively used, and the heat resistance is greatly improved. The fiber diameter of the PPSO fiber at this time is in the range of 10 μm to 30 μm, more preferably 15 μm to 25 μm. When the fiber diameter of the PPSO fiber is less than 10 μm, the rigidity of the fiber becomes small and the shape retention tends to be reduced. When the fiber diameter exceeds 30 μm, the fiber diameter is large and the interfiber gap becomes large, and the nanofiber creates a void. It becomes difficult to fill.

  In addition, in order to obtain a paper having excellent electrical insulation, chemical resistance and heat resistance, the ratio of PPSO nanofiber to PPSO fiber is 30% by weight or more and 70% by weight or less for PPSO nanofiber. Is preferably 70% by weight or more and 30% by weight or less. If the PPSO nanofibers are less than 30% by weight, the gaps in the cut fiber cannot be sufficiently filled and the insulation resistance tends to decrease. If the PPSO nanofibers exceeds 70% by weight, the insulation resistance is good. However, the strength of the paper itself is insufficient and the handling tends to be difficult.

  The use of the paper made of the PPSO fiber thus obtained, which is excellent in electrical insulation, and further excellent in chemical resistance and heat resistance, can be used for insulating materials for electric motor coils, printed boards, etc. It is effectively used in fields where filters, especially chemical resistance and heat resistance are required.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each characteristic value in an Example was calculated | required with the following method.
A. Melting point, falling crystallization temperature The melting point was determined by measuring the temperature at which the main endothermic peak observed with a differential scanning calorimeter (DSC manufactured by Perkin Elmer Co.) was observed.
B. Viscosity Using a Capillograph 1B manufactured by Toyo Seiki Co., Ltd., the apparent viscosity at a shear rate of 1000 sec ⁻¹ was measured.
C. The weight per unit area was calculated from the area and weight of the obtained paper.
D. Tensile strength Tensile strength was measured according to JIS P8113 using Tensilon UCT-100 manufactured by Orientec Corporation.
E. Shape retention was judged by comprehensive sensory tests such as handling and softness of paper. As the sensory evaluation, the best product was judged as ◎, the following good as ○, normal Δ, and bad as ×.
F. Dielectric breakdown voltage Based on the test method of JIS-K-6911, measurement was performed in the atmosphere at a voltage increase rate of 0.25 kV / sec using an upper φ25 cylindrical electrode and a lower φ25 disc electrode as electrodes. .
G. Fiber diameter The fiber and the reference scale were magnified 10,000 times with a scanning electron microscope (Nikon ESEM-2700) and photographed, and the fiber diameter was read on the order of 1/100 μm from the photograph.

Example 1
As a polyphenylene sulfide resin, an autoclave equipped with a stirrer was charged with 25 mol of sodium sulfide 9-hydrate, 2.5 mol of sodium acetate and N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP), and gradually heated to 205 ° C. while passing through nitrogen. And distilled water. Next, the reaction vessel was cooled to 180 ° C., 25.3 mol of 1,4-dichlorobenzene and NMP were added, sealed under nitrogen, heated to 270 ° C., and reacted at 270 ° C. for 2.5 hours. After cooling, the reaction product was washed 5 times with warm water, then heated to 100 ° C. and poured into NMP, stirred for about 1 hour, filtered, and washed several times with hot water. This was put into 25 liters of an acetic acid aqueous solution of pH 4 heated to 90 ° C., and stirred for about 1 hour, filtered, washed with ion-exchanged water of about 90 ° C. until the pH of the filtrate reached 7, The polyphenylene sulfide resin was obtained by drying under reduced pressure at 80 ° C. for 24 hours. The polyphenylene sulfide resin had a melting point of 282 ° C., a crystallization temperature of 243 ° C., and a viscosity of 200 Pa · s at a temperature of 320 ° C. This polymer and polyethylene terephthalate having a melting point of 252 ° C. and a temperature of 320 ° C. and having a melt viscosity of 100 Pa · s were kneaded at a ratio of 30:70 with a biaxial kneader at 300 ° C. to obtain an alloy polymer. This alloy polymer was spun at a temperature of 320 ° C. using an existing single component spinning machine. At this time, the discharge rate was 35 g / min, the chimney was 25 ° C. in temperature, the wind speed was 25 m / min, a general oil agent was applied as a sizing agent, and the spinning speed was 1000 m / min. Got. This undrawn yarn had a strength of 1.15 cN / dtex and an elongation of 412%. Further, the undrawn yarn was drawn 3.5 times between rollers having a first hot roller temperature of 90 ° C. and a second hot roller temperature of 150 ° C. to obtain a polyphenylene sulfide alloy drawn yarn of 100 dtex 36 filaments. This drawn yarn had a strength of 4.0 cN / dtex and an elongation of 22%.

  The drawn yarn was cut to a length of 5 mm, and then immersed in an aqueous solution of sodium hydroxide having a temperature of 98 ° C. and a concentration of 10% for 3 hours to elute and remove the polyethylene terephthalate to obtain polyphenylene sulfide nanofibers.

  800 mL of acetic acid (manufactured by Kanto Chemical Co., Inc.) and 46.16 g of sodium perborate tetrahydrate (0.30 mol; manufactured by Mitsubishi Gas Chemical Co., Inc.) were charged into the reaction vessel, and the nanofiber was stirred and dissolved at 60 ° C. . Next, when 4 g of polyphenylene sulfide nanofibers were immersed in the reaction solution and subjected to an oxidation reaction treatment at 60 ° C. for 10 hours, the weight increased by 24.3%, and polyphenylene sulfide, which is an oxide of 5 g of polyphenylene sulfide nanofibers. Oxide nanofibers were obtained.

  Thus obtained polyphenylene sulfide oxide nanofiber was a fiber having substantially no melting point and good heat resistance. The diameter of 100 fibers was measured using an electron microscope. As shown in FIG. 1, the peak diameter was 0.09 μm, the maximum diameter was 0.15 μm, and the minimum diameter was 0.02 μm.

Example 2
After cutting 10 g of a polyphenylene sulfide alloy drawn yarn obtained in the same manner as in Example 1 to 5 mm, 800 mL of acetic acid (manufactured by Kanto Chemical Co., Inc.), sodium perborate tetrahydrate without eluting and removing polyethylene terephthalate 46 .16 g (0.30 mol; manufactured by Mitsubishi Gas Chemical Co., Inc.) was put into a reaction vessel, immersed in a reaction solution stirred and dissolved at 60 ° C., and subjected to an oxidation reaction treatment at 60 ° C. for 10 hours. 10.75 g of polyphenylene Sulfide alloy oxide fibers were obtained.

  This alloy oxide fiber was immersed in an aqueous solution of sodium hydroxide having a temperature of 98 ° C. and a concentration of 10% for 3 hours to elute and remove polyethylene terephthalate to obtain polyphenylene sulfide oxide nanofibers. This nanofiber exhibited the same characteristics as those obtained in Example 1.

Example 3
20 g of polyphenylene sulfide oxide nanofibers were produced in the same manner as in Example 1, and dispersion was attempted with 20 liters of water using a 50 liter Niagara beater. I was able to get things.

4 liters of this dispersion was put into a handmade paper machine manufactured by Kumagai Riki Kogyo Co., Ltd. having a size of 25 cm × 25 cm and a height of 40 cm, water was added, and a slight amount of polyvinyl alcohol paste was added. Stir. Water from the handmade paper machine was drained, the paper remaining on the wire mesh was transferred to a filter paper, and the filter paper was put into a Japau dryer at a temperature of 125 ° C. and a speed of 0.5 m / min for drying treatment. The dried paper was peeled from the filter paper and passed through a calendering machine consisting of an iron roll and a paper roll. The calendering conditions were a temperature of 100 ° C., a load of 1 kN / 25 cm and a roll peripheral speed of 2 m / min with respect to a 25 cm wide paper, and three passes. As described above, a paper of polyphenylene sulfide oxide nanofibers was obtained. The basis weight of the obtained paper is 64 g / m ² , the thickness is 0.22 mm, the tensile strength of the paper is 2.8 N / 15 mm, and a good paper is obtained except that the paper strength and the form stability are slightly weak. Obtained. The characteristics are shown in Table 1.

  The obtained paper was a dense paper with few voids, and the dielectric breakdown voltage was measured and found to be 56 kV / mm.

Examples 4-7
Polyphenylene sulfide oxide nanofibers obtained in Example 1 and polyphenylene sulfide were melt-spun at a spinning machine temperature of 320 ° C. under the same conditions as in Example 1 using a known spinning machine, and 80 dtex, 36 filament drawn yarn Then, it was cut into a length of 5 mm, oxidized to disperse the polyphenylene sulfide oxide fiber at an arbitrary ratio, and paper was made by the paper making method of Example 3 to obtain a paper. The characteristics are shown in Table 1. These papers were excellent in electrical insulation and excellent in heat resistance and chemical resistance.

Comparative Example 1
The polyphenylene sulfide oxide fiber obtained in Example 4 was dispersed in water and paper was made by the paper making method of Example 3 to obtain a paper consisting only of polyphenylene sulfide oxide fiber. This paper was excellent in chemical resistance and heat resistance, but had low electrical insulation.

Comparative Example 2
When dispersion of the polyphenylene sulfide nanofibers obtained in Example 1 before oxidation treatment was attempted using a 50 liter Niagara beater with a nanofiber / water ratio of 20 g / 20 liters, the nanofibers were dispersed in about 15 minutes. As a result, a pulp-like product was obtained. Paper made of polyphenylene sulfide nanofibers was obtained by papermaking 4 liters of this dispersion. Although this paper has excellent electrical insulation of 40 kV / mm, it melts when heated and has insufficient heat resistance.

  The PPSO nanofiber of the present invention can make a paper made of wet papermaking having heat resistance and chemical resistance into a dense paper. Moreover, the paper using the PPSO nanofiber of the present invention can be preferably used for an electrical insulating material used in a motor, a transformer or the like.

2 is a graph showing the distribution of diameter and frequency of polyphenylene sulfide oxide nanofibers in Example 1. FIG.

Claims (2)

Polyarylene sulfide oxidation characterized by having a fiber diameter of 0.0001 μm or more and 0.3 μm or less, a fiber length of 10 mm or less, and substantially no melting peak observed in a differential scanning calorimeter (DSC) measurement. It contains polyarylene sulfide oxide fibers with a fiber length of 10 mm or less and a fiber diameter of 10 μm or more and 30 μm or less, and calendering is performed under conditions of a temperature of 100 ° C. or more and a load of 1 kN / 25 cm or more. features and be Lupe supermarkets the Rukoto be. Polyarylene sulfide oxide nanofibers 30 to 70% by weight, the polyarylene sulfide oxide fibers according to claim 1, wherein comprising a 70 to 30% by weight paper.

Images