JP2013136685A - Heat resistance porous sheet and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistance porous sheet excellent in sheet processing, heat resistance and electric insulating properties, and to provide a method for manufacturing the heat resistance porous sheet using a solvent-casting technique.SOLUTION: The heat resistance porous sheet includes a polymer that has a repeating structural unit shown by formula (1), wherein the storage modulus at 23°C is 110-200 MPa. In the formula, Rincludes at least one functional group selected from the group consisting of an aromatic hydrocarbon group, a condensed polycyclic hydrocarbon group, a heterocyclic group, a condensed heterocyclic group, an aromatic ketone, an aromatic sulfoxide, an aromatic sulphone, an aromatic ether, an aromatic thioether, a benzoic acid aromatic ester, a sulfuric acid aromatic diester, an aromatic sulfonic acid ester, a phosphate aromatic triester, a phosphorous acid aromatic diester, and a hypophosphorous acid aromatic ester; and R-Reach independently are hydrogen, a methyl group or a phenyl group.

Description

  The present invention relates to a heat-resistant porous sheet used as an electrical insulating member provided in electrical equipment, electronic equipment, electronic components, and the like, and a method for producing the same.

  The electrical insulating member is an indispensable member in power transmission and electrical signal transmission. Since the dielectric becomes an electrical conductor and has low insulation, a low dielectric is required to obtain electrical insulation. Conventionally, a resin such as polyethylene has been used as an insulating material, but there is a limit to reducing the dielectric with these resins alone.

  Since the lowest dielectric material is air, by providing an air phase in the resin, it is possible to realize insulation, that is, low dielectric property, which is difficult to obtain with the resin alone. Usually, as a method of providing an air phase in the resin, a method of making the resin porous is adopted.

  For example, in Patent Document 1, a component constituting the discontinuous phase is selected from evaporation and decomposition from a polymer composition having a microphase separation structure in which a discontinuous phase having an average diameter of less than 10 μm is dispersed in the continuous phase of the polymer. There has been proposed a method for producing a porous body, which is removed by at least one kind of operation and an extraction operation to make it porous.

  Conventionally, electrical insulation has been mainly used for power transmission, but recently it has also been applied to the field of information transmission and information processing. In addition to conventional electrical insulation, low dielectric materials are used for the purpose of improving the efficiency of electrical signal transmission. Yes.

  Ceramics are the mainstream low dielectric material used in the field of information transmission and information processing, but ceramics have poor toughness, are easy to break, have low impact resistance against dropping, etc. There are disadvantages such as inability to reduce weight and poor workability.

  As a material for overcoming the drawbacks of these ceramics, a porous body using a resin as a matrix has attracted attention. Resins are tougher and harder to break than ceramics. Moreover, since the resin can be easily thinned by a process such as casting, it can contribute to the weight reduction of the entire module. Furthermore, promoting porosity for lowering the dielectric (generally, the content of the air phase in the resin is referred to as porosity or porosity. Promoting porosity increases porosity or porosity. This is equivalent to an increase.) Since flexibility can be imparted to the porous body, impact resistance is also improved.

  The inside of a terminal used in the field of information transmission and information processing becomes hot during use, and the terminal may operate continuously for a long time. The low dielectric material is used as a module member inside these terminals. Therefore, low dielectric materials are required to have high heat resistance, particularly heat distortion resistance, a low weight loss rate, and a high continuous use temperature.

  The heat resistance of the resin material is lower than that of ceramics. Generally, in order to improve the heat resistance of the resin, the glass transition temperature of the resin is increased, or a crosslinking treatment is performed. In order to use a resin material as a low dielectric member, it is necessary to process it into a sheet shape. As a sheet processing method, a heat melting method or a solvent casting method is generally used. However, an increase in the glass transition temperature of the resin is disadvantageous in the heat melting method, and the crosslinking treatment has a lower solubility in the solvent. It will be disadvantageous. Thus, the resin material having heat resistance has a problem that it is difficult to process into a sheet.

JP 2001-81225 A

  An object of the present invention is to provide a heat-resistant porous sheet excellent in sheet processability, heat resistance, and electrical insulation and a method for producing a heat-resistant porous sheet using a solvent casting method.

（式中、Ｒ_１は芳香族炭化水素基、縮合多環式炭化水素基、複素環基、縮合複素環基、芳香族ケトン、芳香族スルホキシド、芳香族スルホン、芳香族エーテル、芳香族チオエーテル、安息香酸芳香族エステル、硫酸芳香族ジエステル、芳香族スルホン酸エステル、リン酸芳香族トリエステル、亜リン酸芳香族ジエステル、及び次亜リン酸芳香族エステルからなる群より選択される少なくとも１種の官能基を含み、Ｒ_２〜Ｒ_５はそれぞれ独立に水素、メチル基、又はフェニル基である。） That is, this invention relates to the heat resistant porous sheet which contains the polymer which has a repeating structural unit represented by following formula (1), and whose storage elastic modulus in 23 degreeC is 110-200 Mpa.

(Wherein R ₁ represents an aromatic hydrocarbon group, a condensed polycyclic hydrocarbon group, a heterocyclic group, a condensed heterocyclic group, an aromatic ketone, an aromatic sulfoxide, an aromatic sulfone, an aromatic ether, an aromatic thioether, At least one selected from the group consisting of benzoic acid aromatic esters, sulfuric acid aromatic diesters, aromatic sulfonic acid esters, phosphoric acid aromatic triesters, phosphorous acid aromatic diesters, and hypophosphorous acid aromatic esters Including a functional group, R _{2 to} R ₅ are each independently hydrogen, a methyl group, or a phenyl group.)

  The present inventors have found that a polymer having a repeating structural unit represented by the formula (1) (hereinafter referred to as polyaryl ether resin) is soluble in a specific organic solvent, and can be formed into a sheet by a solvent casting method. It was found that a heat-resistant porous sheet having excellent heat resistance and electrical insulation can be obtained by using the polyaryl ether resin. The polyaryl ether-based resin can achieve both improvement in heat resistance and improvement in sheet processability, both of which have been difficult to achieve together.

  The heat-resistant porous sheet of the present invention has a storage elastic modulus at 23 ° C. of 110 to 200 MPa. When the storage elastic modulus is less than 110 MPa, when removing the phase separation agent from the polymer sheet, the template shape of the holes formed by the removal of the phase separation agent cannot be maintained, and fine pores are not formed. It becomes difficult to form. When fine holes are not formed, the sheet strength is lowered, or pinholes are easily generated when the layer is thinned, resulting in poor electrical insulation. On the other hand, when it exceeds 200 MPa, the flexibility of the sheet is lowered.

（式中、Ｒ_６〜Ｒ_８はそれぞれ独立に水素、メチル基、又はフェニル基である。） R ₁ is a direct combination of a functional group in which two adjacent carbon atoms among the carbon atoms constituting the aromatic ring of the condensed polycyclic hydrocarbon group are substituted with nitrogen, and an aromatic ketone and / or aromatic sulfoxide. A segment having a chain-like structure is preferable, and any one of the following formulas (2) to (4) is more preferable.

(In formula, R < ₆ > -R < ₈ > is hydrogen, a methyl group, or a phenyl group each independently.)

When the functional group constituting R ₁ is only a monocyclic ring or a monocyclic multimer, it rotates on a linear bond axis, so that the molecular chain has a degree of freedom and is easy to move. As a result, polyarylether There is a tendency for the glass transition temperature of the resin to be low. On the other hand, when R ₁ contains a condensed polycyclic hydrocarbon group or a condensed heterocyclic group, although it has a bond that can rotate on the bond axis, the movement of the molecular chain is likely to be restricted due to overlapping of aromatic rings, etc. As a result, the glass transition temperature of the polyaryl ether resin tends to be high. Furthermore, in the condensed polycyclic hydrocarbon group or the condensed heterocyclic group, since the condensed ring shares a carbon atom or a hetero atom, the rotation is restricted, and as a result, the glass transition temperature is improved. Moreover, the solubility to a solvent improves by introduce | transducing the heterocyclic group or condensed heterocyclic group containing a hetero atom in a molecule | numerator. Therefore, R ₁ preferably contains a condensed polycyclic hydrocarbon group and / or a condensed heterocyclic group, and particularly preferably any one represented by formulas (2) to (4).

  The heat-resistant porous sheet of the present invention preferably has a dielectric loss tangent of 0.02 or less. When the dielectric loss tangent exceeds 0.02, the dielectric loss increases and the signal is easily attenuated in the device.

  The heat resistant porous sheet of the present invention preferably has a glass transition temperature of 225 ° C or higher. When the glass transition temperature is less than 225 ° C., the sheet is likely to soften or shrink when it is placed in a high temperature environment. As a result, the shape of the hole changes (for example, “collapse”) or the sheet is peeled off from the substrate, so that the low dielectric property or electrical insulation tends to deteriorate.

  The heat-resistant porous sheet of the present invention preferably has an average pore size of 0.1 to 10 μm. When the average pore diameter is less than 0.1 μm, the flexibility of the sheet tends to be lowered or low dielectric properties tend not to be obtained. On the other hand, if the thickness exceeds 10 μm, the sheet strength tends to decrease, or pinholes tend to occur when the layer is thinned, and the electrical insulation tends to deteriorate.

In the heat-resistant porous sheet of the present invention, it is preferable that the shrinkage rate in the MD direction calculated by the following formula is 3% or less and the shrinkage rate in the TD direction is 2.5% or less.
Shrinkage rate (%) = {(A−B) / A} × 100
A: Sheet size (mm) before heating (25 ° C.)
B: Dimensions of sheet after heating at 260 ° C. for 30 seconds and cooling to 25 ° C. (mm)

  Here, the MD direction represents a direction in which the web is conveyed, and the TD direction represents a direction intersecting at right angles to the MD direction. When the shrinkage rate in the MD direction and TD direction exceeds the above values, the shape of the hole changes (for example, “collapse”) or the sheet peels off from the substrate, so the low dielectric property or electrical insulation tends to deteriorate. is there.

The heat-resistant porous sheet of the present invention preferably has a weight reduction rate calculated by the following formula of 3% or less.
Weight reduction rate (%) = {(XY) / X} × 100
X: Weight of sheet before heating (g)
Y: Weight of sheet after heating at 260 ° C. for 24 hours and cooling to 25 ° C. (g)

  It is considered that the weight reduction is caused by decomposition of the resin or the like. When the weight reduction rate exceeds 3%, there is a tendency for problems such as strength reduction or outgas generation due to decomposition.

  The method for producing a heat-resistant porous sheet of the present invention comprises applying a polymer composition comprising a polyaryl ether resin, a phase separation agent for phase separation from the polyaryl ether resin, and an organic solvent on a substrate, A step of producing a polymer sheet having a microphase separation structure by curing, and a step of removing the phase separation agent from the polymer sheet.

  In the present invention, a solvent extraction method is preferably employed as a method for removing the phase separation agent from the polymer sheet, and liquefied carbon dioxide or supercritical carbon dioxide is preferably used as the solvent.

  The polyaryl ether resin of the present invention is soluble in an organic solvent, and can be formed into a sheet by a solvent casting method. By using the polyaryl ether resin as a matrix, a heat resistant porous sheet excellent in heat resistance and electrical insulation can be obtained. The heat resistant porous sheet is useful as an insulating material in a high temperature environment.

（式中、Ｒ_１は芳香族炭化水素基、縮合多環式炭化水素基、複素環基、縮合複素環基、芳香族ケトン、芳香族スルホキシド、芳香族スルホン、芳香族エーテル、芳香族チオエーテル、安息香酸芳香族エステル、硫酸芳香族ジエステル、芳香族スルホン酸エステル、リン酸芳香族トリエステル、亜リン酸芳香族ジエステル、及び次亜リン酸芳香族エステルからなる群より選択される少なくとも１種の官能基を含み、Ｒ_２〜Ｒ_５はそれぞれ独立に水素、メチル基、又はフェニル基である。） Embodiments of the present invention will be described below. The heat-resistant porous sheet of the present invention contains a polyaryl ether resin represented by the following formula (1) as a matrix.

(Wherein R ₁ represents an aromatic hydrocarbon group, a condensed polycyclic hydrocarbon group, a heterocyclic group, a condensed heterocyclic group, an aromatic ketone, an aromatic sulfoxide, an aromatic sulfone, an aromatic ether, an aromatic thioether, At least one selected from the group consisting of benzoic acid aromatic esters, sulfuric acid aromatic diesters, aromatic sulfonic acid esters, phosphoric acid aromatic triesters, phosphorous acid aromatic diesters, and hypophosphorous acid aromatic esters Including a functional group, R _{2 to} R ₅ are each independently hydrogen, a methyl group, or a phenyl group.)

  Examples of the aromatic hydrocarbon group include a phenylene group, an alkyl-substituted phenylene group, and multimers thereof (bicyclic ring assembly, polycyclic ring assembly).

  Examples of the condensed polycyclic hydrocarbon group include a functional group having a basic skeleton of naphthalene, fluorene, phenanthrene, anthracene, biphenylene, naphthacene, pyrene, triphenylene, chrysene, picene, perylene, and pentacene (these functional groups are alkyl-substituted). And may be modified with ketone.).

  Examples of the heterocyclic group include a functional group having a basic skeleton of furan, thiophene, pyrrole, oxazole, thiazole, imidazole, pyrazole, pyran, pyridine, pyridazine, pyrimidine, and pyrazine (even if these functional groups are alkyl-substituted). And may be ketone-modified.).

  Examples of the condensed heterocyclic group include indole, isoindole, benzofuran, benzothiophene, chromene, quinoline, isoquinoline, quinolidine, purine, indazole, quinazoline, cinnoline, quinoxaline, phthalazine, carbazole, acridine, phenanthridine, phenazine, and Examples thereof include functional groups having phenothiazine as a basic skeleton (these functional groups may be alkyl-substituted or ketone-modified).

R ₁ is a direct combination of a functional group in which two adjacent carbon atoms among the carbon atoms constituting the aromatic ring of the condensed polycyclic hydrocarbon group are substituted with nitrogen, and an aromatic ketone and / or aromatic sulfoxide. A segment having a chain-like structure is preferred. Specifically, it is a segment represented by the following formulas (2) to (4).

R _{6 to} R ₈ are each independently hydrogen, a methyl group, or a phenyl group.

The polyaryl ether resin may be a homopolymer, a block copolymer, or a random copolymer. In the case of a block copolymer or a random copolymer, R ₁ may contain two or more types of segments represented by the above formulas (2) to (4).

  The heat-resistant porous sheet of the present invention is obtained by, for example, applying a polymer composition containing a polyaryl ether resin, a phase separation agent for phase separation from the polyaryl ether resin, and an organic solvent on a substrate, and then curing. To produce a polymer sheet having a microphase separation structure and removing the phase separation agent from the polymer sheet.

  As the phase separation agent, one that is completely incompatible with the resin or one that is hardly compatible with the resin is selected. Examples of such a phase separation agent include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; one end or both ends alkyl blockage of polyalkylene glycol; one end or both ends of polyalkylene glycol (Meth) acrylate blockages; triglycerol ethers of polyalkylene glycols; higher alcohols (long-chain alkyl alcohols) such as hexyl alcohol, dodecyl alcohol and stearyl alcohol; liquid alkanes such as liquid paraffin; higher fatty acids and their glycerols Esters (oils and fats); lipids such as phospholipids and glycolipids. These may be used alone or in combination of two or more. Among these, polyethylene glycol monoalkyl ether, polyethylene glycol dialkyl ether, polyethylene glycol fatty acid monoester, polyethylene glycol fatty acid diester, polypropylene glycol monoalkyl ether, polypropylene glycol dialkyl ether, polypropylene glycol fatty acid monoester, or polypropylene glycol fatty acid diester are used. It is preferable.

  The average pore size, porosity, pore size distribution, etc. of the heat-resistant porous sheet indicate the type of resin used, the phase separation agent and other raw materials, the mixing ratio, and the reaction such as the heating temperature and heating time during reaction-induced phase separation. Since it varies depending on the conditions, it is preferable to create the phase diagram of the system and select the optimum conditions in order to obtain the target average pore size, porosity, and pore size distribution.

  The phase separation agent is usually used in an amount of 20 to 300 parts by weight, preferably 50 to 250 parts by weight, more preferably 100 to 200 parts by weight, based on 100 parts by weight of the polyaryl ether resin. When the amount of the phase separation agent added is less than 20 parts by weight, the desired porosity for exhibiting low dielectric properties cannot be obtained. On the other hand, when the amount exceeds 300 parts by weight, phase transition between the resin and the phase separation agent occurs, the phase separation agent becomes a matrix, and the resin undergoes phase separation and aggregates. At this time, since the phase separation agent does not function as a template for the pores, no pores are formed.

  For example, in order to produce a heat-resistant porous sheet having an average pore size of 0.1 to 10 μm, it is preferable to use 50 to 200 parts by weight of a phase separation agent with respect to 100 parts by weight of a polyaryl ether resin, More preferably, it is 50-150 weight part.

  The organic solvent is not particularly limited as long as it dissolves the polyaryl ether resin and the phase separation agent, but an amide solvent or an amine solvent is preferably used, and in particular, N-methyl-2-pyrrolidone (NMP ), Dimethylformamide (DMF), and amide solvents such as dimethylsulfoxide (DMSO) are preferably used. The addition amount of the organic solvent is not particularly limited, but is preferably added so that the solid content concentration (total weight% of the polyaryl ether resin and the phase separation agent) is 50% by weight or less, and more preferably 20 to Add to 40% by weight. When the solid content concentration exceeds 50% by weight, the viscosity of the solution is extremely increased, the leveling property of the solution on the base material is lowered during casting, and the resulting heat-resistant porous sheet tends to have defects in appearance. It is in. When such a defect exists, when the heat-resistant porous sheet is incorporated into a device, problems such as poor adhesion to a substrate or electrical characteristics such as poor electrical insulation occur.

  Additives such as pigments and anti-aging agents may be added to the polymer composition as necessary, as long as electrical properties and phase separation are not hindered.

  Hereinafter, the manufacturing method of the heat resistant porous sheet of this invention is demonstrated in detail.

  First, a polymer composition containing the resin, a phase separation agent, and an organic solvent is applied on a substrate.

  The substrate is not particularly limited as long as it has a smooth surface, and examples thereof include plastic films such as PET, PE, and PP; glass plates; metal foils such as stainless steel, copper, and aluminum. In order to continuously produce the polymer sheet, a belt-like substrate may be used.

  The method for applying the polymer composition onto the substrate is not particularly limited, and examples of the method for continuous application include wire bar, kiss coat, and gravure. Examples of the method for applying in batch include, for example, Applicators, wire bars, knife coaters and the like can be mentioned.

  Next, the polymer composition coated on the substrate is heated to remove the organic solvent and cure to prepare a polymer sheet in which the phase separation agent is microphase-separated. The microphase separation structure usually has a sea-island structure in which the polyarylether resin is the sea and the phase separation agent is the island. When the organic solvent is removed by a treatment such as heating after casting, the polyaryl ether resin and the phase separating agent are incompatible with each other or are incompatible with each other, and phase separation occurs between them. This porous technology is called “drying-induced phase separation method”.

  The temperature at which the organic solvent is volatilized (dried) is not particularly limited, and may be appropriately adjusted depending on the type of the solvent used.

  Next, the microseparated phase separation agent is removed from the polymer sheet to produce a heat resistant porous sheet. In addition, you may peel the polymer sheet from a base material before removing a phase-separation agent.

  The method for removing the phase separation agent from the polymer sheet is not particularly limited, but a method of extracting with a solvent is preferable. It is necessary to use a solvent that is a good solvent for the phase separation agent and does not dissolve the polyaryl ether resin, such as organic solvents such as toluene, ethanol, ethyl acetate, and heptane, liquefied carbon dioxide. And supercritical carbon dioxide. Since liquefied carbon dioxide and supercritical carbon dioxide easily penetrate into the polymer sheet, the phase separation agent can be efficiently removed.

  When liquefied carbon dioxide or supercritical carbon dioxide is used as a solvent, a pressure vessel is usually used. As the pressure vessel, for example, a batch type pressure vessel, a pressure vessel having a pressure-resistant sheet feeding and winding device, or the like can be used. The pressure vessel is usually provided with carbon dioxide supply means composed of a pump, piping, valves and the like.

  The temperature and pressure when extracting the phase separation agent with liquefied carbon dioxide or supercritical carbon dioxide may be any temperature and pressure at which carbon dioxide becomes a liquid or supercritical fluid, but usually 30 to 100 ° C., 7 It is -35MPa, Preferably it is 35-90 degreeC and 10-30MPa.

  Extraction may be performed by continuously supplying and discharging liquefied carbon dioxide or supercritical carbon dioxide into a pressure vessel containing a polymer sheet, and the pressure vessel is closed (the charged polymer sheet, liquefied carbon dioxide or The supercritical carbon dioxide may not be moved out of the container. When supercritical carbon dioxide is used, swelling of the polymer sheet is promoted, and the phase separation agent is efficiently removed from the polymer sheet by improving the diffusion coefficient of the insolubilized phase separation agent. When liquefied carbon dioxide is used, the diffusion coefficient is lowered, but the permeability into the polymer sheet is improved, so that the phase separation agent is efficiently removed from the polymer sheet.

  The extraction time is appropriately adjusted depending on the temperature and pressure during extraction, the blending amount of the phase separation agent, the thickness of the polymer sheet, and the like.

  On the other hand, when extracting with an organic solvent as the solvent, the phase separation agent can be removed under atmospheric pressure, so the heat-resistant porous sheet is deformed compared to when extracting with liquefied carbon dioxide or supercritical carbon dioxide. Can be suppressed. Moreover, the extraction process of a phase-separation agent can be continuously performed by passing a polymer sheet sequentially in an organic solvent.

  Examples of the extraction method using an organic solvent include a method of immersing a polymer sheet in an organic solvent, a method of spraying an organic solvent on the polymer sheet, and the like. The immersion method is preferable from the viewpoint of the removal efficiency of the phase separation agent. Further, the phase separation agent can be efficiently removed by exchanging the organic solvent several times or performing extraction while stirring.

  After removing the phase separation agent, the heat-resistant porous sheet may be dried.

  One side or both sides of the heat-resistant porous sheet may be subjected to adhesion processing or adhesion processing. The pressure-sensitive adhesive used for the pressure-sensitive adhesive processing is not particularly limited, and acrylic pressure-sensitive adhesive (solution polymerization system, emulsion polymerization system, UV polymerization system, extrusion system, etc.), rubber pressure-sensitive adhesive (solution coating type, latex type, hot melt) Mold, extrusion mold, etc.). Adhesives used for adhesive processing are not particularly limited, and epoxy resin adhesives, acrylic resin adhesives (emulsion systems, solvent systems, etc.), polyurethane adhesives, synthetic / natural rubber adhesives, vinyl acetate resin systems Examples thereof include an adhesive and an ethylene-vinyl acetate copolymer adhesive.

  The heat-resistant porous sheet is required to have a storage elastic modulus at 23 ° C. of 110 to 200 MPa, and preferably 125 to 190 MPa.

  The heat-resistant porous sheet preferably has a dielectric loss tangent (tan δ) of 0.02 or less, more preferably 0.01 or less, and particularly preferably 0.005 or less.

  The heat-resistant porous sheet preferably has a glass transition temperature obtained from the peak value of the loss modulus G ″ of 225 ° C. or higher, more preferably 250 ° C. or higher.

  The average pore diameter of the heat-resistant porous sheet is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm.

The heat-resistant porous sheet preferably has an MD shrinkage of 3% or less calculated by the following formula and a TD shrinkage of 2.5% or less, more preferably an MD shrinkage. Is 2% or less, and the shrinkage in the TD direction is 1.5% or less, particularly preferably, the shrinkage in the MD direction is 1.5% or less and the shrinkage in the TD direction is 1% or less.
Shrinkage rate (%) = {(A−B) / A} × 100
A: Sheet size (mm) before heating (25 ° C.)
B: Dimensions of sheet after heating at 260 ° C. for 30 seconds and cooling to 25 ° C. (mm)

The heat-resistant porous sheet preferably has a weight reduction rate calculated by the following formula of 3% or less, more preferably 1% or less, and particularly preferably 0.1% or less.
Weight reduction rate (%) = {(XY) / X} × 100
X: Weight of sheet before heating (g)
Y: Weight of sheet after heating at 260 ° C. for 24 hours and cooling to 25 ° C. (g)

  Although the thickness of a heat resistant porous sheet changes with uses, it is 1-250 micrometers normally, Preferably it is 5-150 micrometers, More preferably, it is 20-120 micrometers.

  The heat-resistant porous sheet of the present invention is excellent in heat resistance, has low dielectric properties and high insulating properties, and exhibits good electrical characteristics. Since it has such performance, the heat-resistant porous sheet of the present invention is suitably used as an electrical insulating member for devices, modules, substrates and the like in the field of information transmission or information processing.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Measurement and evaluation method]
(Measurement of dielectric loss tangent tan δ)
The produced heat-resistant porous sheet was cut into a size of 2 mm width × 80 mm length to obtain a sample. Using a cavity resonator (manufactured by Kanto Electronics Application Development Co., Ltd.) and a detector connected to a computer installed with analysis software (Agilent Technology, Vector Network Analyzer 8722A), the sample was placed in the cavity resonator and sampled at 1 GHz. The dielectric loss tangent tan δ of was measured.

(Measurement of glass transition temperature)
The dynamic viscoelasticity of the produced heat-resistant porous sheet was measured using a rheometer (manufactured by TA Instruments, ARES), and the peak value of the loss elastic modulus G ″ was defined as the glass transition temperature.

(Measurement of average pore diameter)
The produced heat-resistant porous sheet was cut into a size of 4 mm square to obtain a sample. The diameter of the pores of the sample was measured using a scanning electron microscope (manufactured by Hitachi High-Technology, low vacuum scanning electron microscope S-3400N), and the pore diameter was calculated from the ratio to the scale. The pore diameter of 30 pores was calculated, and the average value was taken as the average pore diameter.

(Measurement of storage modulus)
The storage elastic modulus at 23 ° C. (constant temperature) of the produced heat-resistant porous sheet was measured using a rheometer (manufactured by TA Instruments, ARES).

(Measurement of shrinkage rate)
The produced heat-resistant porous sheet was cut into a size of about 50 mm × 50 mm to obtain a sample. The dimension in the MD direction and the TD direction of the sample adjusted to 25 ° C. with a caliper was accurately measured. The values are each A (mm). This sample was immersed in a silicone oil bath adjusted to 260 ° C. for 30 seconds, taken out, and then cooled to 25 ° C. And the dimension of MD direction and TD direction of the sample was measured correctly similarly to the above. The values are each B (mm). The shrinkage rate (%) in the MD direction and the TD direction was calculated by the following formulas.
Shrinkage rate (%) = {(A−B) / A} × 100
A: Sample dimensions (mm) before heating (25 ° C.)
B: Sample dimensions (mm) after heating at 260 ° C. for 30 seconds and cooling to 25 ° C.

(Measurement of weight loss rate)
The produced heat-resistant porous sheet was cut into a size of 50 mm × 50 mm to obtain a sample. The sample was accurately weighed. Let that value be X (g). Thereafter, the sample was put into an oven adjusted to 260 ° C. for 24 hours, taken out, and then cooled to 25 ° C. And the weight of the sample was measured accurately. Let that value be Y (g). The weight reduction rate was calculated by the following formula.
Weight reduction rate (%) = {(XY) / X} × 100
X: Weight of sample before heating (g)
Y: Weight of sample after heating at 260 ° C. for 24 hours and cooling to 25 ° C. (g)

Example 1
27 parts by weight of a polyaryl ether resin (trade name: PPES, manufactured by Dalian Polymer New Material Co.), which is a segment represented by the above formula (1) and R ₁ is represented by the above formula (3), is added to N-methyl- It was dissolved in 73 parts by weight of 2-pyrrolidone (NMP) to obtain a polymer solution having a solid content of 27% by weight. To this polymer solution, 27 parts by weight of polyethylene glycol monoallyl ether having a weight average molecular weight of 200 as a phase separation agent was added and mixed until uniform to prepare a polymer composition (solid content concentration 42.5% by weight). . This polymer composition was coated on a PET film (thickness 38 μm) so that the film thickness after drying was 50 μm, and then dried for 10 minutes in a constant temperature dryer at 85 ° C. to volatilize and remove NMP to form a polymer sheet. Was made.

  After peeling the polymer sheet from the PET film, placing the polymer sheet in a pressure-resistant container and pressurizing to 25 MPa at room temperature (25 ° C.), circulating a total amount of 5000 L of carbon dioxide while maintaining the pressure, polyethylene glycol Monoallyl ether was extracted to prepare a heat resistant porous sheet.

Example 2
33 parts by weight of a polyarylether resin (trade name: PPESK, manufactured by Dalian Polymer New Material), which is a segment represented by the above formula (1) and R ₁ is represented by the above formula (4), is added to N-methyl- It was dissolved in 67 parts by weight of 2-pyrrolidone (NMP) to obtain a polymer solution having a solid content concentration of 33% by weight. To this polymer solution, 33 parts by weight of polyethylene glycol monomethyl ether having a weight average molecular weight of 400 as a phase separation agent was added and mixed until uniform to prepare a polymer composition (solid content concentration 49.6% by weight). Thereafter, a heat-resistant porous sheet was produced in the same manner as in Example 1.

Example 3
23 parts by weight of a polyarylether resin (trade name: PPEK, manufactured by Dalian Polymer New Material Co.), which is a segment represented by the above formula (1) and R ₁ is represented by the above formula (2), is added to N-methyl- It was dissolved in 77 parts by weight of 2-pyrrolidone (NMP) to obtain a polymer solution having a solid concentration of 23% by weight. To this polymer solution, 23 parts by weight of polyethylene glycol monoallyl ether having a weight average molecular weight of 200 as a phase separation agent was added and mixed until uniform to prepare a polymer composition (solid content concentration 37.4% by weight). . Thereafter, a heat-resistant porous sheet was produced in the same manner as in Example 1.

Comparative Example 1
25 parts by weight of polyetherimide was dissolved in 75 parts by weight of N-methyl-2-pyrrolidone (NMP) to obtain a polymer solution having a solid concentration of 25% by weight. To this polymer solution, 25 parts by weight of polyethylene glycol monoallyl ether having a number average molecular weight of 200 as a phase separation agent was added and mixed until uniform to prepare a polymer composition (solid content concentration 40% by weight). Thereafter, a heat-resistant porous sheet was produced in the same manner as in Example 1.

  As shown in Table 1, it can be seen that the heat-resistant porous sheets of Examples 1 to 3 have excellent heat resistance from the results of the glass transition temperature and the shrinkage rate. On the other hand, it can be seen that the heat-resistant porous sheet of Comparative Example 1 has a very large shrinkage rate and is inferior in heat resistance.

  The heat-resistant porous sheet of the present invention is excellent in sheet processability, heat resistance, and electrical insulation, and is suitably used as an electrical insulation member for devices, modules, substrates, etc. in the field of information transmission or information processing.

Claims (11)

A heat-resistant porous sheet comprising a polymer having a repeating structural unit represented by the following formula (1) and having a storage elastic modulus at 23 ° C. of 110 to 200 MPa.

(Wherein R ₁ represents an aromatic hydrocarbon group, a condensed polycyclic hydrocarbon group, a heterocyclic group, a condensed heterocyclic group, an aromatic ketone, an aromatic sulfoxide, an aromatic sulfone, an aromatic ether, an aromatic thioether, At least one selected from the group consisting of benzoic acid aromatic esters, sulfuric acid aromatic diesters, aromatic sulfonic acid esters, phosphoric acid aromatic triesters, phosphorous acid aromatic diesters, and hypophosphorous acid aromatic esters Including a functional group, R _{2 to} R ₅ are each independently hydrogen, a methyl group, or a phenyl group.) R ₁ is a direct combination of a functional group in which two adjacent carbon atoms among the carbon atoms constituting the aromatic ring of the condensed polycyclic hydrocarbon group are substituted with nitrogen, and an aromatic ketone and / or aromatic sulfoxide. The heat-resistant porous sheet according to claim 1, which has a chain-like structure. The heat resistant porous sheet according to claim 1, wherein R ₁ is any _one of the following formulas (2) to (4).

(In formula, R < ₆ > -R < ₈ > is hydrogen, a methyl group, or a phenyl group each independently.) The heat-resistant porous sheet according to any one of claims 1 to 3, wherein the dielectric loss tangent is 0.02 or less. The heat resistant porous sheet according to any one of claims 1 to 4, which has a glass transition temperature of 225 ° C or higher. The heat-resistant porous sheet according to any one of claims 1 to 5, having an average pore diameter of 0.1 to 10 µm. The heat-resistant porous sheet according to any one of claims 1 to 6, wherein the shrinkage in the MD direction calculated by the following formula is 3% or less and the shrinkage in the TD direction is 2.5% or less.
Shrinkage rate (%) = {(A−B) / A} × 100
A: Sheet size (mm) before heating (25 ° C.)
B: Dimensions of sheet after heating at 260 ° C. for 30 seconds and cooling to 25 ° C. (mm) The heat-resistant porous sheet according to any one of claims 1 to 7, wherein a weight reduction rate calculated by the following formula is 3% or less.
Weight reduction rate (%) = {(XY) / X} × 100
X: Weight of sheet before heating (g)
Y: Weight of sheet after heating at 260 ° C. for 24 hours and cooling to 25 ° C. (g) From the polymer sheet, a step of applying a polymer composition containing the polymer, a phase separation agent that phase-separates with the polymer, and an organic solvent on a substrate and curing the polymer composition, and a polymer sheet having a microphase separation structure The manufacturing method of the heat resistant porous sheet in any one of Claims 1-8 including the process of removing the said phase-separation agent. The method for producing a heat-resistant porous sheet according to claim 9, wherein the phase separation agent is removed by solvent extraction. The method for producing a heat-resistant porous sheet according to claim 10, wherein the solvent is liquefied carbon dioxide or supercritical carbon dioxide.