WO2005042839A1

WO2005042839A1 - Composite papyraceous material

Info

Publication number: WO2005042839A1
Application number: PCT/JP2004/015841
Authority: WO
Inventors: Mikio Furukawa; Katsuyuki Toma; Yoshinao Yamada; Akira Ito; Norihiko Miki
Original assignee: Daikin Industries, Ltd.
Priority date: 2003-10-31
Filing date: 2004-10-26
Publication date: 2005-05-12
Also published as: JP2005133260A; US20070084575A1

Abstract

Disclosed is a composite papyraceous material composed of a fibrous polytetrafluoroethylene (in particular, a fibrous powder thereof) and a fibrous polyimide.

Description

Specification

Composite paper

Technical field

[0001] The present invention relates to a fibrous polyimide and fibrous polytetrafluoroethylene (PTFE) composite paper which also has a force.

Background art

[0002] Various paper-like materials containing fibers that also have the properties of high-performance engineering plastics have been proposed, and are expected to be used as members of electronic devices such as substrate materials and heat-resistant structural materials. I have. Among them, those containing a fiber made of fluororesin as a component are advantageous in terms of dielectric properties and friction properties, and various studies have been made.

[0003] For example, Patent Document 1 proposes a paper-like material including a fluororesin-based fiber and a heat-resistant engineering plastic fiber.

[0004] Patent Document 2 proposes a sheet-shaped insulator in which an impregnating agent is impregnated into a fiber base made of a hybrid of insulating fibers and fluororesin fibers.

[0005] Patent Document 3 proposes a low dielectric constant printed wiring board material in which a mixed nonwoven fabric made of a fluorine resin fiber and a heat-resistant engineering plastic fiber is combined with a cyanate ester resin.

[0006] Patent Document 4 proposes, as a sliding member, a fluorine-based resin composition in which a polyimide fiber is blended with polytetrafluoroethylene resin.

[0007] On the other hand, with regard to paper-like materials containing a fiber composed of polyimide as a constituent component, for example, Patent Document 5 proposes a substrate nonwoven fabric for a laminate in which polyimide fibers are bonded with a thermosetting binder.

[0008] However, the fluororesin fibers used in Patent Documents 13 to 13 are substantially in the form of chopped strands, and the fiber diameter is significantly larger than that of pulp-like material when compared under the same weight. If so, the problem remains in its homogeneity. Also, from the viewpoint of the production method of the fluorine resin fiber, the fluorine fiber to be applied is sufficiently baked, and its function as a binder for binding the fibers is insufficient. Sheet-like material obtained by wet papermaking If so, some sort of binder component must be added. In many cases, one component of the binder is a factor that impairs the properties of the resulting paper.

[0009] In Patent Document 4, although the form of polytetrafluoroethylene resin and the like are not specified or unknown, it is not possible to obtain a thin paper-like composite molded article by estimating the manufacturing method. It is assumed to be virtually impossible.

[0010] Further, in Patent Document 5, a thermosetting resin is employed as a binder for the polyimide fiber. As described above, such a thermosetting resin makes it possible to obtain only paper-like materials in which the inherent characteristics of polyimide fibers are impaired! /.

Patent Document 1: JP-A-10-212686

Patent Document 2: JP-A-11-144529

Patent Document 3: Japanese Patent No. 2762544

Patent Document 4: Japanese Patent No. 2983900

Patent Document 5: JP-A-11-200210

Disclosure of the invention

Problems to be solved by the invention

[0011] The present invention has been made in view of the background of the related art, and has excellent strength, thermal dimensional stability, chemical resistance, and abrasion resistance, and has an unprecedented small value in water absorption and dielectric properties. It is an object of the present invention to provide an engineering plastic fibrous paper having the following properties.

[0012] That is, the present invention relates to a composite paper-like material comprising both fibrous polyimide and polytetrafluoroethylene.

[0013] The fibrous polyimide is not particularly limited, but is a fiber obtained by cutting a thermoplastic polyimide resin into a fiber by a melt spinning method or the like and cutting it to a fixed length, preferably a short fiber, particularly a crystal. U, which is preferably a fiber having properties.

[0014] The thermoplastic polyimide preferably has a glass transition temperature of 230 ° C or higher and a melting point of 400 ° C or lower. If the glass transition point is lower than 230 ° C, the heat resistance becomes poor, which is not preferable. On the other hand, if the melting point exceeds 400 ° C., processing by heat becomes difficult, which is not preferable.

[0015] Fibrous polyimide is a short fiber in consideration of the uniformity of the obtained composite paper. The average fiber length is 1 to 15 mm, preferably 2 to 8 mm, and the average fiber diameter is 3 to 30 m, preferably 4 to 20 μm.

[0016] The orientation of the crystal part of a raw yarn obtained from a thermoplastic polyimide resin having crystallinity by a melt spinning method or the like can be increased by heating and drawing under appropriate conditions. Fibrous polyimide with highly oriented crystal parts contributes to the thermal dimensional stability of paper-like materials with small dimensional changes during heating and cooling, and has the characteristics of low water absorption. Therefore, dimensional changes and changes in electrical characteristics due to water absorption are extremely small. `` Fiber having crystallinity '' is represented by the crystallinity of the fibrous polyimide, the crystallinity measured by X-ray diffraction method is preferably 15% or more, more preferably 20% or more, particularly It preferably means 25% or more. If the crystallinity is less than 15%, the thermal dimensional change and water absorption tend to increase, which is not preferable.

[0017] The polyimide is preferably a polyimide having the chemical structure represented by the following general formula (1) as a repeating unit and capable of satisfying the above characteristics.

[Chemical 1]

(In the formula, R represents a tetravalent aromatic residue selected from a monocyclic aromatic, a condensed polycyclic aromatic, and a non-condensed polycyclic aromatic having an aromatic ring bonded directly or via a bridge member. X represents a divalent residue selected from a direct bond, a hydrocarbon group, a carboyl group, an ether group, a thio group or a sulfol group, and may be a Y atom, an alkyl group, an alkoxyl group.

1 Y is water

Four

Or a monovalent residue selected from halogen groups. )

Among these polyimides, in the above general formula (1), R is more preferably a short cyclic aromatic compound. X is more preferably a direct bond.

1- Y is a hydrogen atom

Four

preferable.

[0018] A particularly preferred specific example of such a polyimide is a polyimide having the following chemical structural formula (2) as a repeating unit. [Chemical 2]

(Wherein n is preferably 5-200)

Such a polyimide is available, for example, under the trade name Aurum (manufactured by Mitsui Iridakusha).

[0019] When the polyimide is made into a fiber, a polyimide having various chemical structures may be blended. In addition, as long as the properties required for the polyimide and the paper-like material used in the present invention are not impaired, polyester may be used. , Polyolefins, polyamides, polyphenylene sulfide, polyether imide, polyether ether ketone, and other polymers such as fluororesin, and titanium oxide, zinc oxide, and magnesium oxide. An inorganic filler such as alumina, silica, aluminum nitride, silicon nitride, boron nitride, silicon carbide, carbon black, graphite and mica may be blended.

[0020] The fibrous polytetrafluoroethylene used in the present invention is a fibrous powder. Polytetrafluoroethylene fibrous powder is, for example, one obtained by beating polytetrafluoroethylene powder, which has non-uniform beard-like branches which are preferable, while having a fiber form as a whole. And at the visual level show behavior as a powder. The fibrous powder preferably has an average fiber length of 5 to 2000 m and an average view factor of 5 or more! If the ratio is below this range, in the paper making process, the drainage is poor and the productivity is lowered, but the paper strength with low air permeability cannot be obtained. If it exceeds this, the surface condition of the paper deteriorates, and it is difficult to obtain thin and uniform paper. Further, the specific surface area force measured by a nitrogen adsorption method is preferably 4.0 m ² / g or more. If it is lower than this, the binding function is inferior, and the strength of the obtained paper-like material is reduced. The average form factor is obtained by dividing the fiber length by the fiber width.

[0021] The polytetrafluoroethylene may be a tetrafluoroethylene homopolymer, or a copolymer of tetrafluoroethylene and a trace monomer other than tetrafluoroethylene. It may be unified and non-melting (hereinafter, referred to as modified polytetrafluoroethylene).

Examples of the trace monomer include perfluoroolefin, perfluoro (alkyl vinyl ether), a cyclic fluorinated monomer, perfluoroalkylethylene, and the like.

Examples of the above perfluoroolefin include hexafluoropropylene and the like, and examples of monofluoro (alkylbutyl ether) include perfluoro (methylbiruether), perfluoro (propylbutylether) and the like. Examples of the cyclic fluorinated monomer include fluorodixole and the like, and examples of perfluoroalkylethylene include perfluoromethylethylene.

[0022] Fibrous polytetrafluoroethylene has a low-temperature-side peak area in a melting endothermic curve obtained by differential scanning calorimetry (DSC) analysis performed at a heating rate of 5 ° C per minute. It is preferred that the ratio is 88.5% or more of the total peak area and that the partially-baked one is used. When the paper is formed, a paper-like material having a smooth surface and excellent air permeability can be obtained. The upper limit is preferably 99.0%. If the ratio is below these ranges, it is difficult to obtain smooth paper. If the ratio is above these ranges, the unity of the paper is lost, and the operability is significantly impaired.

It can be said that the peak area indicated by the differential scanning calorimeter is directly proportional to the calorific value, and is proportional to the number of molecules in a generally accepted range. Therefore, the ratio of unraveled polytetrafluoroethylene molecules can be evaluated by the peak ratio between the area of the low-temperature side peak obtained from the differential scanning calorimeter and the total peak area. A double peak or a single peak with well-defined shoulders can be mathematically understood as a composite curve of three or more multiple normal distributions. Separation as a distribution curve is considered to be sufficiently valid, and reasonable results have been obtained in the study of the present invention. This means that even partially disentangled molecules are disassembled as small V, which is the calorific value required for disentanglement in evaluation, and are included in the normal distribution of molecules! / Just fine.

[0024] The complex absorption peak is usually approximated using a Gaussian-Lorentian type curve. Can be separated by The Gaussian type! / Has a feature that the degree of deviation is smaller than when using only the Lorentian type curve! /, And only the deviation is used.Therefore, this method can be applied to most calculation software attached to commercially available analytical instruments. Used. In this case, the two peaks apparent in the polytetrafluoroethylene powder used as the raw material are given as initial values, and approximation is performed without any restriction to obtain the basic peaks. The position was determined. For example, in the case of the fibrous polytetrafluoroethylene used in Example 1 of the present invention, the basic peak positions thus obtained are 339.14 ° C. and 343.01 ° C. By limiting the peak temperature to 0.6-0.7 ° C or less from the initial value, approximation was performed to separate the composite curve into two, and the peak area was determined. In the above study, the information on the raw material powder was used to shorten the time required for convergence of the values, but the melting curve force of the fibrous powder can also be obtained directly.

[0025] The composite paper-like material of the present invention is obtained by combining the above fibrous polyimide and polytetrafluoroethylene into a paper-like composite. The composite method is not particularly limited, but can be easily obtained with high productivity by mixing and applying a papermaking method. From the viewpoint of obtaining a thin and uniform formation of a composite paper-like material, it is particularly preferable to use a wet papermaking method among the papermaking methods.

[0026] The wet papermaking method includes at least a dispersion step of dispersing fibrous polytetrafluoroethylene in water, a mixing step of fibrous polyimide, a papermaking step, and a drying step.

[0027] In the dispersing step, fibrous polytetrafluoroethylene slurry is added to water and fibrillated using a parper or a refiner equipped with a stirrer to thereby disperse the fibrous polytetrafluoroethylene slurry. obtain. Usually, polytetrafluoroethylene has a large contact angle with water and is difficult to disperse uniformly in water. Therefore, a dispersing agent is added to fibers or fibrous powder in advance, or It is preferable to mix them. The dispersant to be applied is not particularly limited, but is preferred in that non-ionic polyoxyethylene alkyl ethers exhibit a dispersing effect when added in a small amount.

[0028] In the mixing step of mixing the fibrous polyimide, the fibrous polyimide is added to the slurry of the fibrous polytetrafluoroethylene obtained in the dispersing step, and the same treatment as in the dispersing step is performed to obtain a mixed slurry. Normally, fibrous polyimide is evenly applied to the above slurry without using a dispersant. It can be dispersed all over.

[0029] The mixing ratio of the fibrous polyimide and polytetrafluoroethylene may be appropriately adjusted according to the purpose of use, but the lower limit of the mixing ratio of the fibrous polyimide is 5% by mass, preferably 10% by mass. % Is desirable. The upper limit is preferably 90% by mass, more preferably 80% by mass. If the compounding power of the fibrous polyimide is less than ^% by mass, the thermal dimensional stability and strength may be insufficient. If it exceeds 90% by mass, the handling of the composite paper in the manufacturing process may become poor. The strength and dielectric properties may be insufficient.

[0030] Next, a known wet papermaking apparatus exemplified by a circular net wet paper machine, a short net wet paper machine, a short net inclined wet paper machine, or a long net inclined wet paper machine is used for the mixed slurry. The papermaking process is used to form a paper-like material (papermaking product), and the resulting papermaking product is combined by a drying process in which the papermaking machine is dried by a hot-air, contact, or radiation dryer attached to the papermaking machine. Obtain a paper. In this papermaking method, if a pressurizing step of pressing the papermaking material in the thickness direction with a pair of metal rolls is provided, the fibrous polytetrafluoroethylene is pressed against the fibrous polyimide, and the shape retention It is possible to obtain a composite paper-like material excellent in quality. Pressing may be performed at room temperature, and the pressing force may be generally about 110 kgf / cm. However, if possible, the pressure may be applied while heating. This pressing step may be performed between the paper making step and the drying step, or may be performed after the drying step.

[0031] paper had a basis weight of the paper-like material after drying, 50- 1500 g / m ^2, preferably carried out so that Do a 100- 1200g / m ^2. If the basis weight is smaller than that value, the operability in the papermaking method tends to decrease, and it tends to be difficult to manufacture stably. On the other hand, if the basis weight is too large, there is a tendency that production problems such as a decrease in drainage and insufficient drying in the papermaking process become remarkable.

[0032] Next, heating and pressurization is exemplified by a roll-shaped press device such as a calender roll composed of a pair of metal rolls or a double belt press device capable of performing a heat press between a pair of opposed metal-made belts. Using a device, the composite paper obtained above is heated and pressed in the thickness direction, so that the fibrous powder of polytetrafluoroethylene is fused to the fibrous polyimide to form the composite paper. The strength of the object is significantly increased. That is, in addition to the step of obtaining a composite paper-like material by the above-mentioned wet papermaking method, by performing a step of pressurizing the obtained paper-like material under heating, the fibrous powder of polytetrafluoroethylene power is converted into a fibrous polyimide. Fused to Obtained, ie, a densified composite paper. It is needless to say that the heating and pressurizing step may be performed continuously after the papermaking step, or may be performed on a separate line.

[0033] The heating temperature at the time of heating and pressing is preferably performed at a temperature equal to or higher than the melting point of polytetrafluoroethylene. If the final heating temperature is lower than the melting point, the effect of improving the mechanical strength characteristics tends to be hardly obtained. On the other hand, this indicates that the binding force can be maintained within a certain range even if a heat treatment below the melting point is performed until the final heating step. It is possible to get. The heating temperature is preferably lower than the temperature at which the polyimide forming the fibrous polyimide melts.If the polyimide is a crystalline polyimide, the heating temperature is lower than the melting point of the polyimide, and furthermore, the melting point. Preferably, the temperature is at least 10 ° C lower. If the heating temperature exceeds the melting point of the polyimide, the fibrous polyimide is extremely melted, and the compounding effect of the fibrous polyimide tends not to be exerted. Usually, a heating temperature of about 340-380 ° C may be used. The melting point referred to here is a value measured using a differential scanning calorimeter (Pykinl DSC, manufactured by Pakinkin Elma).

[0034] Further, the pressurizing pressure at the time of heating and pressurizing is not particularly limited, but the higher the pressurizing pressure, the lower the porosity of the obtained composite paper-like material tends to be. For example, a pressurized pressure of about 0.05-lOMPa can be adopted.

[0035] Further, in the above-described process, when the composite paper-like material of the present invention is laminated into two or more layers and pressed under caloric heat, the resulting composite paper-like material becomes an integrated and densified paper-like material having no interlayer. By changing the density, a densified paper having a desired thickness can be obtained. At this time, by applying the composite paper-like material of the present invention having a different composition ratio to each layer, a composite paper-like material in which the composition of polyimide and polytetrafluoroethylene changes in the thickness direction can be obtained.

[0036] The thickness of the paper-like material obtained in this manner is determined by the number of layers and the degree of densification when pressed under heating in the papermaking process and under heating. From the viewpoint of uniformity, those having a thickness of 20 to 2000 μm are more preferable, and more preferably 25 to 800 / zm. If the value is below the lower limit, the operability during the process tends to be low and the yield tends to decrease.If the value exceeds the upper limit, the dimensions tend to be non-uniform in the pressurizing step under heating and the force tends not to be obtained. is there. The apparent density is preferably 0.3-2.1 g / cm ^3. If it falls below this range, the strength tends not to be excellent, and if it exceeds this range, it tends to be practically impossible to produce.

[0037] Various additives can be added to the composite paper-like material of the present invention as long as the object of the present invention is not impaired. That is, it is exemplified by other organic or inorganic short fibers or pulp-like materials such as aramide, polyester, polyetherimide, polyetheretherketone, polysulfone, polyphenylenesulfide, polyketone, carbon, glass, and alumina. Staple fiber or pulp-like material, furthermore, titanium oxide, zinc oxide, magnesium oxide, alumina, silica, aluminum nitride, silicon nitride, boron nitride, silicon carbide, carbon black, graphite, my power, disulfide, etc. Various particulate matter (filaments) which also has a strong property such as molybdenum may be blended.

[0038] Further, for the purpose of imparting strength or the like, a thermoplastic resin such as a polyimide resin or a precursor thereof or a thermosetting resin such as an epoxy resin may be contained according to the purpose. . In this case, the polyimide resin or its precursor, epoxy resin, or the like is usually applied, sprayed, or impregnated in the form of an emulsion or a solution.

[0039] One or more of these additives may be blended as long as the object of the present invention is not impaired, but the total weight of the additives when dried is 30% by mass relative to the total mass of the composite paper of the present invention. % Is preferred from the viewpoint of maintaining various characteristics.

[0040] The composite paper-like material of the present invention can be in a form in which a fibrous powder having polytetrafluoroethylene force is fused to fibrous polyimide by the heating and pressurizing step as described above, The paper-like material thus densified has excellent strength. Further, even when the layers are laminated in the heating and pressing step, no phenomenon of destruction between the layers during use is observed, and the layer has substantially the same strength level as that of a single layer. The strength is determined by the compounding ratio of the fibrous powder and the fibrous polyimide and the degree of densification or the amount of the third component to be compounded, for example, specified in JIS-P8113. The average breaking length obtained by the measurement method used is usually in the range of 0.5 to 7 km.

[0041] The composite paper-like material of the present invention is excellent in dimensional stability under high-temperature use with little dimensional change due to heat. As the dimensional stability, the average coefficient of linear expansion at 20-230 ° C is 20-30 m / m '° C in both the production direction and the width direction of the composite paper. (Value measured according to JIS-K7197). If the above average linear expansion coefficient is out of the range of 20-30 m / m '° C, the dimensional change under high temperature use tends to be large, making it unsuitable for use.

[0042] In the present invention, by providing a paper-like material constituted by randomly dispersing the above-mentioned fibrous polyimide and polytetrafluoroethylene, the dimensional stability and the directional tolerance are excellent. Paper can be obtained.

[0043] It is preferable that the composite paper has a low water absorption. When the composite paper is left in an environment of 25 ° C and a relative humidity of 60% for 24 hours, the water absorption capacity is not more than the water absorption capacity calculated by the following formula. Is a preferred embodiment of the present invention.

[Equation 1] Water absorption = ^W ~ ^Wo X 100 (o / o) (Equation _υ

Wo

(In the formula, W represents the mass of the nonwoven fabric after moisture absorption, and W represents the mass of the nonwoven fabric at the time of absolute drying.)

0

[0045] In general, it is known that polyimide has a relatively high water absorbency due to its imide group's strong and polar properties. In the case of a molded product, a dimensional change and a change in electrical characteristics at the time of water absorption are known. Tended to be a problem. Conventional amorphous polyimide fiber strength The size of the water absorption has also been a problem in the paper-like material formed, but in the present invention, a crystalline polyimide fiber having a small water absorption is used. By using a fibrous powder that also has polytetrafluoroethylene power as the main constituent, it has become possible to obtain a high-performance composite paper with low water absorption unlike before. In particular, the polyimide represented by the above formula (1) or the chemical formula (2) has crystallinity and a small proportion of imide groups in the chemical structure. It is preferable to use a fibrous polyimide made of these properties.

The dielectric constant is low for both polyimide and polytetrafluoroethylene, and is excellent in insulation performance. Since the paper-like material of the present invention does not contain the third component serving as a binder, similar properties can be expected from the composite paper-like material. Its electrical characteristics are measured by a cylindrical dielectric constant evaluation device (a resonator manufactured by Kanto Electronics Co., Ltd.) and a network manufactured by Agilent Technologies, Inc. And an analyzer) at room temperature at 2.45 GHz. The composite paper of the present invention varies depending on the content ratio of the fibrous powder composed of fibrous polyimide and polytetrafluoroethylene and the apparent density of the composite paper, but usually the densified composite paper. In the case of a solid, the dielectric constant obtained by the above measurement method is in the range of 2.0-3.1. Further, the dielectric loss obtained by the same measurement 1 X 10- ⁵ - in the range of 3 X 10- ³

It is known that both polyimide and polytetrafluoroethylene are excellent in chemical resistance and oxidation resistance, and the composite paper of the present invention can be excellent in these properties. Chemical resistance can be evaluated by weight change, color, or shape change after immersing the composite paper in the drug to be tested and leaving it to stand at room temperature for one week. Shows a large change in weight and dimensional change, and a slight increase in weight when swelling Force Generally used alcohol solvents, ether solvents, ketone solvents, ester solvents, amide solvents, etc. It has been found that it has excellent properties with respect to many of the non-polar solvents such as polar solvents and hydrocarbon solvents, and various oils and fuels. Further, the oxidation resistance is determined by immersing the composite paper-like material in a so-called Fenton reagent in which a very small amount of an activator such as iron sulfate (ΠΙ) is mixed with hydrogen peroxide and the degree of deterioration due to the oxidation. Can be evaluated by observing, for example, almost no deterioration was observed even when immersed at 70 ° C. for 48 hours.

[0048] Since the composite paper-like material of the present invention has a form in which polyimide having excellent abrasion resistance and polytetrafluoroethylene having excellent lubricity are uniformly mixed, the composite paper-like material has excellent friction and wear characteristics. For example, a thrust friction and wear tester (Toyo Baldwin; EMFIII-E) can be used to evaluate at room temperature and without lubrication. It shows good wear resistance even when slid for 48 hours at a dynamic speed, and does not damage the mating material.

[0049] Since the composite paper-like material of the present invention has the above-mentioned properties, a seamless belt, a stamping mold, a guard tube, a flame-retardant paper material which is required to have strong strength, heat resistance and thermal dimensional stability. It is the best material for, valve seat, solder pattern and cushioning material. In addition, since it has excellent electrical characteristics, it can be applied to a circuit board. In addition, Since it has excellent chemical properties and abrasion resistance, it is also an excellent material for filters, abrasive paper materials, electrolyte membranes and seal materials.

Hereinafter, the present invention will be described with reference to examples.

(Example of Production of Fibrous Polyimide)

Aurum (trade name; manufactured by Mitsui Iridaku) was used as the polyimide resin. After the polyimide resin is melted at 415 ° C, a strand obtained by extruding from a 0.2 mm diameter die is drawn at a speed of 700 m / min, cooled and solidified, wound around a paper tube, and wound with a fiber diameter of about 23. m of fibrous polyimide was obtained. Next, the fibrous polyimide was stretched about three times in a heater at 350 ° C. to obtain a fibrous polyimide having a fiber diameter of about 12 m. The crystal orientation of the obtained fibrous polyimide was advanced by stretching. In this example, short fibers obtained by cutting this fibrous polyimide into a length of 5 mm were used. The short fiber had a crystallinity of 26% and a melting point of 389 ° C.

(Example of Producing Polytetrafluoroethylene Fibrous Powder)

A polymer obtained by emulsion polymerization of 100 mol% of tetrafluoroethylene was used as a raw material polytetrafluoroethylene powder (average particle size: 570 m). The obtained raw material polytetrafluoroethylene powder was fed into a hopper by a feeder. Next, the polytetrafluoroethylene powder was supplied to a stretching tank equipped with rotating blades (tank inner diameter: 160 mmφ) while being appropriately assisted by dry air, and stretched. At this time, the lower surface of the stretching tank was partly meshed, and only those smaller than a certain size were allowed to exit the stretching tank. This was treated with a standard classification sieve to remove powder having a size of 5 μm or less to obtain a raw material polytetrafluoroethylene fibrous powder.

[0053] The obtained polytetrafluoroethylene fibrous powder is

Average fiber length: 1.5 m

Average view factor: 40

Specific surface area: 6.38m ² / g

Low temperature side peak area ratio: 92.3%

Met.

(Example 1) 3.2 parts by mass of polytetrafluoroethylene fibrous powder is added to water in which 0.1 parts by mass of polyoxyethylene alkyl ether is added to 1000 parts by mass of water, and the mixture is stirred.

) And uniformly dispersed by stirring.

Next, 0.8 parts by mass of the polyimide short fiber cut into a length of 5 mm was added into the system and stirred to obtain a slurry in which each raw material was uniformly mixed and dispersed.

[0056] This slurry was further diluted with water to a slurry concentration of 0.02% by mass, and supplied to a short net inclined continuous paper machine to continuously obtain a paper product. The obtained paper has a moisture content of about

It was 30% by mass.

Next, a pressure treatment of a linear pressure of 0.1 N / mm was continuously performed at room temperature with a pair of stainless steel rolls, and a polytetrafluoroethylene fibrous powder and a polyimide short fiber were processed. Was crimped.

Further, the paper was supplied to a conveyor-type hot air dryer attached to a paper machine and dried to obtain a composite paper having a water content of almost 0% by mass.

[0059] The obtained composite paper-like material is obtained by compressing polytetrafluoroethylene fibrous powder to fibrous polyimide, exhibits strength, has good shape retention, and has fibrous polyimide. And polytetrafluoroethylene fibrous powder were uniformly dispersed and blended. The paper-like material obtained through this step is referred to as composite paper-like material A.

The composite paper A obtained by the wet papermaking method was preheated at 240 ° C. for 2 minutes under no pressure using a continuous belt press (manufactured by Sandvik), and then subjected to a pressure of 25 N / mm. The mixture was heated at 350 ° C. for 5 minutes under pressure, and then rapidly cooled to 50 ° C. while maintaining the pressure to obtain a densified composite paper continuously. In the obtained composite paper-like material, the polytetrafluoroethylene fibrous powder was melted and fused to the surface of the polyimide short fiber, and the surface was smooth and had a dense structure. The densified paper obtained through this step is referred to as composite paper B.

[0061] The obtained paper-like composite B had a basis weight of 256 g / m ² and a thickness of 154 µm. In addition, the average linear expansion coefficient, breaking length, water absorption, and dielectric constant were measured. Table 1 summarizes the above results.

[0062] The thickness was measured by the method of averaging the 50 value obtained by measuring at intervals of 100cm ² (10 X 10cm) Diary point at digital thickness meter. The breaking length was measured using a universal testing machine (manufactured by Intesco Corporation) in accordance with JIS-P8113. The average coefficient of linear expansion was measured according to JIS-K7197 using a TMA measuring device (manufactured by TA Instruments; TMA2940).

The water absorption was measured according to the above formula I.

The measurement of the dielectric constant was performed by a method using the above-mentioned cylindrical dielectric constant evaluation device. Note that the measurement sample was obtained by laminating the composite paper-like material A into a dense body with a thickness of 1.4 mm according to the procedure for preparing the composite paper-like material B, and cutting this into a 1.4 mm width. A 1.4 mm square rod was used as a sample.

(Example 2-5)

A composite paper B was obtained in the same manner as in Example 1 except that the compounding ratio of the fibrous polyimide and the polytetrafluoroethylene fibrous powder was set to Table 1. Table 1 summarizes the physical properties of the obtained composite paper.

(Comparative Example 1)

Paper-like material A having polyimide short fiber strength was produced in the same manner as in Example 1 except that 4 parts by mass of polyimide short fiber was added without blending the polytetrafluoroethylene fibrous powder.

[0065] The paper-like material of Comparative Example 1 was prepared by blending polytetrafluoroethylene fibrous powder, and the fibers were not pressed together and did not retain the paper-like form. Paper A could not be obtained.

(Comparative Example 2)

A paper B having a polytetrafluoroethylene fibrous powder strength was obtained in the same manner as in Example 1 except that 4 parts by mass of polytetrafluoroethylene fibrous powder was added without blending the polyimide short fiber. . Table 1 summarizes the physical properties of the obtained paper-like material B.

(Comparative Example 3)

A composite paper-like material A was prepared in the same manner as in Example 1 except that polytetrafluoroethylene short fibers (trade name: Toyofuron, manufactured by Toray Fine Chemical Co., Ltd.) were used instead of the polytetrafluoroethylene fibrous powder. Was made.

The polytetrafluoroethylene short fibers used in this comparative example are;

Average view factor: 250 Specific surface area: 0.1m ² / g

Low temperature side peak area ratio: 100%

Had.

[0068] In this comparative example, since the polytetrafluoroethylene short fibers did not function sufficiently as a binder, the force fibers were not pressed together and it was difficult to maintain a paper-like form. I could not get the power.

[Table 1]

1) Fibrous polyimide; 2) Polytetrafluoroethylene

(Evaluation of oxidation resistance)

(Example 6)

The composite paper-like material B obtained in Example 2 was cut into a length of 100 mm and a width of 10 mm and used as a sample. The sample was immersed in an oxidizing agent solution obtained by dissolving 20 ppm of iron sulfate (II) in a 30% by mass aqueous solution of hydrogen peroxide, and kept at 70 ° C. for 80 hours. After that, the sample was taken out, washed with water, dried, and the breaking length was measured.

[0071] A sample subjected to the same treatment, immersed in pure water instead of the oxidizing agent solution, was set to have a breaking length of 100%. It was used as an index of oxidation resistance. As a result, it showed high oxidation resistance of 95%. It is useful as a substrate for electrolyte membranes requiring high oxidation resistance, such as polymer fuel cells.

(Comparative Example 4)

A composite paper was prepared in the same manner as in Example 2 except that an aramide fiber (trade name: Twaron; manufactured by Nippon Aramide Co.) having a fiber diameter of about 15 m and an average fiber length of ¾ mm was used instead of the polyimide short fiber. Form B was obtained.

[0073] The obtained composite paper had a basis weight of 296 g / m ² , a thickness of 295 μm, and a breaking length of 1.9 km. The obtained composite paper-like substance B was evaluated for acid resistance in the same manner as in Example 6, and found to be 63%, which was inferior to the acid resistance.

(Evaluation of slidability)

(Example 7)

The composite paper-like material A of Example 1 was cut into 500 × 500 mm and two sheets were laminated, and one of the heating devices was used! Then, it was heated to 350 ° C. under a pressure of 3 MPa using a press having a press plate, and heated at 350 ° C. for 15 minutes to obtain a densified composite paper.

[0075] The density of the obtained composite paper was 1.60 g / m ² , and the thickness was 322 μm. A ring-shaped cross section of 25 mm in outer diameter and 20 mm in inner diameter was obtained by using a thrust friction and abrasion tester (manufactured by Toyo Boldwin Co., Ltd .; EMFIII-E) as a measurement sample. A sliding test was performed using a jig made of carbon steel S45C with the sliding surface as a mating material. The surface roughness of the sliding surface of the mating material was Ra 0.5a, and the measurement was performed without lubrication. The sample was rubbed at room temperature for 20 hours at a peripheral speed of 100 m / min and a caro pressure of 0.49 MPa, and the wear amount and friction coefficient of the sample were measured. The amount of wear was evaluated based on the weight change of the sample before and after the test. The coefficient of friction was calculated by reading the stress (torque) generated in the rotation direction with respect to the sample at the time of measurement using a load cell attached to the device. Table 2 shows the obtained results.

(Comparative Example 5)

A composite paper A was obtained in the same manner as in Example 1 except that an aramide fiber (trade name: Twaron; manufactured by Nippon Aramid) having a fiber diameter of about 15 m and an average fiber length of ¾ mm was used instead of the polyimide short fiber. . Further, two sheets were laminated in the same manner as in Example 7 to obtain a composite paper. The density of the obtained composite paper was 1.45 g / m ² , and the thickness was 353 m. The obtained composite paper was subjected to a sliding test in the same manner as in Example 7. Table 2 shows the obtained results.

[0077] [Table 2] Thickness

(pm) (mg) Coefficient of friction

Example 7 1.60 322 0.9 0.20

Comparative Example 5 1.45 353 3.1 0.23 Table 2 clearly shows that the composite paper of the present invention has excellent slidability and can be used under high sliding conditions.

_

Low wear and low coefficient of friction.

Claims

The scope of the claims

[1] A composite paper comprising both fibrous polytetrafluoroethylene and polyimide.

[2] The composite paper-like material according to claim 1, wherein the fibrous polyimide is a fiber having crystallinity.

[3] The composite paper-like material according to claim 1 or 2, wherein the polyimide is thermoplastic.

[4] The composite paper according to claim 1, wherein the polyimide is represented by the following chemical formula (1):

[Chemical 1]

(In the formula, R represents a tetravalent aromatic residue selected from a monocyclic aromatic, a condensed polycyclic aromatic, and a non-condensed polycyclic aromatic having an aromatic ring bonded directly or via a bridge member. X represents a divalent residue selected from a direct bond, a hydrocarbon group, a carboyl group, an ether group, a thio group or a sulfo group, and Y represents a hydrogen, an alkyl group, an alkoxyl group or

1 Y

Four

Indicates a monovalent residue selected from a halogen group. ) ₀

[5] The composite paper-like material according to claim 1, wherein the polyimide is represented by the following chemical formula (2):

[Formula 2]

6. The composite paper according to claim 5, wherein the fibrous polyimide force is a short fiber having an average fiber diameter of 3 to 30 m and an average fiber length S1 to 15 mm.

[7] Fibrous polytetrafluoroethylene is a fibrous powder having an average fiber length of 100 The composite paper-like material according to any one of claims 16 to 15, wherein the composite paper-like material has a size of 5000 ^ m and an average shape factor of 5 or more.

[8] Polytetrafluoroethylene has a peak area ratio force of 88.5% of the total peak area on the low-temperature side of the melting endotherm curve obtained by differential scanning calorimeter analysis at a heating rate of 5 ° C / min. The composite paper-like material according to any one of claims 17 to 17, wherein the content is at least 30%.

[9] The composite paper according to any one of claims 18 to 18, wherein the fibrous polytetrafluoroethylene is thermally fused to the fibrous polyimide.

[10] The method for producing a composite paper according to any one of claims 18 to 18, wherein fibrous polytetrafluoroethylene and polyimide are produced by a papermaking method.

[11] The method for producing a composite paper-like material according to claim 10, wherein the papermaking method is a wet papermaking method.

12. The papermaking method according to claim 11, wherein the method comprises a dispersion step of fibrous polytetrafluoroethylene, a mixing step of fibrous polyimide, a papermaking step, a pressing step and a drying step. A method for producing the composite paper-like material according to the above.

13. The method for producing a composite paper-like material according to claim 12, comprising a pressure treatment step under heating after the drying step.

[14] Any one selected from the group consisting of a seamless belt, a circuit board, a stamping mold, a filter, a guard tube, a flame-retardant paper material, a solder pattern paper, an abrasive paper material, an electrolyte membrane, a sliding member, a sealing member, and a cushioning material 10. The composite paper-like article according to claim 11, which is used for one.