JP5779893B2 - Laminate made of nonwoven fabric and film - Google Patents

Description

  The present invention relates to a laminate in which a wet nonwoven fabric made of polyphenylene sulfide fiber and a synthetic resin film are joined.

  In recent years, with the miniaturization, weight reduction, high functionality, high performance, and large capacity of electric devices, the improvement of the reliability of the insulation system is expected. Therefore, an insulating material having various characteristics such as heat resistance, electrical characteristics, mechanical characteristics, chemical resistance, and workability is required.

  It has been conventionally known that a synthetic resin film such as polyethylene terephthalate (hereinafter also referred to as PET) or polyphenylene sulfide (hereinafter also referred to as PPS) can be used as an insulating material. However, PET film has poor heat resistance and hydrolysis resistance, and the range of use is limited. On the other hand, the PPS film is excellent in heat resistance and hydrolysis resistance, but lacks impact resistance. For example, the PPS film tends to be pierced, torn, or delaminated during molding.

  Accordingly, a laminate of a film and a fiber sheet has been proposed for the purpose of improving the weaknesses of these films. For example, Patent Documents 1, 2, and 3 propose a laminate of a PPS film and a fiber sheet for the purpose of improving the impact resistance of the PPS film. However, these laminates have a problem that the interface between the film layer and the fiber sheet layer may be peeled off at the time of molding, and the use requiring particularly complicated and advanced molding is remarkably restricted. In addition, when an insulating material having such a fiber sheet is used for high-voltage power transmission, there is a problem that local dielectric breakdown is likely to occur.

JP-A 63-237949 JP-A-8-197689 JP-A-8-197690

  In view of the prior art, the present invention is a laminate of a fiber sheet and a synthetic resin film, excellent in heat resistance and impact resistance, suitable for molding with little peeling, and further with local insulation at a high voltage. The present invention relates to providing a laminate excellent in destruction and a method for producing the laminate.

  As a result of intensive studies to solve this problem, the configuration of the present invention employs the following means. That is, a laminate in which a wet nonwoven fabric composed of polyphenylene sulfide fibers and a synthetic resin film are joined together, wherein at least a part of the polyphenylene sulfide fibers are unstretched polyphenylene sulfide fibers, and unstretched polyphenylene on the surface of the wet nonwoven fabric The sulfide fiber is fused with the surrounding polyphenylene sulfide fiber in a flat film shape.

  In addition, a method for producing such a laminate includes forming a polyphenylene sulfide fiber, at least a part of which is an unstretched polyphenylene sulfide fiber, into a sheet by a wet papermaking method, and then converting the unstretched polyphenylene sulfide fiber to the surrounding polyphenylene by heating and pressure treatment. It is characterized in that it is fused with a sulfide fiber in a flat film shape to form a wet nonwoven fabric, and then laminated and bonded to a synthetic resin film.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated body excellent in the adhesive force which joined the wet nonwoven fabric and synthetic resin film which consist of a polyphenylene sulfide fiber can be provided, Furthermore, heat resistance, insulation important as an electrical insulation use To provide a laminate having a smooth surface with excellent breaking strength, varnish impregnation property, impact resistance, and few surface fluff that causes local dielectric breakdown when used in high-voltage power transmission. it can.

  Furthermore, according to the present invention, it is possible to provide a laminate suitable for a heat-resistant sheet, a heat-resistant tube, a heat-resistant cushioning material and the like for electric equipment having a high tear strength. In electrical equipment, in particular, a heat-resistant sheet may be torn by contact with other members in an assembly process, and a heat-resistant sheet having high tear strength has been desired.

It is a surface photograph (300 times) of the wet nonwoven fabric of Example 1. It is a surface photograph (300 times) of the wet nonwoven fabric of Example 2. It is a surface photograph (300 times) of the wet nonwoven fabric of Example 3. It is a surface photograph (300 times) of the wet nonwoven fabric of Example 4. It is a surface photograph (300 times) of the wet nonwoven fabric of the comparative example 1.

  The inventors of the present invention believe that the peeling of the interface between the film layer and the fiber sheet layer that occurs when the laminate of the film and the fiber sheet is molded is due to insufficient adhesion between the film layer and the fiber sheet layer. It can be improved by improving the adhesion of the layer, and the local dielectric breakdown at high voltage is partly due to the fluff on the surface of the fiber sheet, and can be improved by improving the surface smoothness of the fiber sheet. The present invention has been found. That is, the present invention is a laminate in which a wet nonwoven fabric composed of polyphenylene sulfide fibers and a synthetic resin film are joined together, wherein at least a part of the polyphenylene sulfide fibers are unstretched polyphenylene sulfide fibers, and Unstretched polyphenylene sulfide fiber is fused with the surrounding polyphenylene sulfide fiber in a flat film shape.

  As described above, the laminate of the present invention is integrated and improved by improving the adhesion between the film layer and the fiber sheet layer only by fusing the surface of the wet nonwoven fabric made of polyphenylene sulfide fibers into a flat film. It exhibits tear strength.

  The PPS fiber constituting the wet nonwoven fabric of the present invention is obtained by melt-spinning a PPS resin excellent in hydrolysis resistance and moisture absorption dimensional stability, and the obtained wet nonwoven fabric has the same features. Can do.

  Here, the PPS resin is a polymer containing phenylene sulfide units such as p-phenylene sulfide units and m-phenylene sulfide units as repeating units. The PPS in the present invention may be a homopolymer of any one of these units or a copolymer having both units. Further, it may be a copolymer with another aromatic sulfide, but preferably 70 mol% or more of the repeating units are composed of p-phenylene sulfide.

  Moreover, as a weight average molecular weight of PPS resin used for a PPS fiber, 40000-60000 are preferable. By setting it to 40,000 or more, good mechanical properties as PPS fibers can be obtained. Further, the viscosity of 60000 or less is preferable because the viscosity of the melt spinning solution can be suppressed and a special high pressure resistant spinning equipment is not required.

  It is important that the wet nonwoven fabric of the present invention contains unstretched PPS fibers in at least a part of the PPS fibers constituting the wet nonwoven fabric. Since the unstretched PPS fiber has a low flow start temperature, it can be used as a binder. When the unstretched PPS fiber is melted, it is fused with the surrounding PPS fiber constituting the wet nonwoven fabric in a flat film shape. It is possible to obtain a fiber sheet having a smooth surface with less surface roughness.

  As used herein, the term “flat membrane” means that unstretched PPS fibers present on the surface of a wet nonwoven fabric are heated and pressed by calendering or hot pressing to melt and deform, filling gaps with surrounding fibers, It is in the form of a film formed by fusing to fibers. By fusing the unstretched PPS fibers on the surface into a flat film, it is possible to suppress the floating of the single fibers that cause fluff, and at the joint surface between the wet nonwoven fabric and the synthetic resin film, the wet nonwoven fabric is synthesized. Since the contact area with the resin film is increased, the anchor effect can be made extremely high, and a laminate having high adhesion between both layers can be obtained. Note that not only the surface of the wet nonwoven fabric but also unstretched PPS fibers existing inside may be fused.

  Further, the unstretched PPS fiber on the surface was fused into a flat film shape, which was suitable for molding as an insulator. That is, by adopting the configuration of the present invention, it is more difficult to break at the time of molding than a conventional laminate of PPS nonwoven fabric and film, specifically, a laminate having improved end tear resistance value, that is, tear strength. I was able to do it.

It is preferable that 20 mass%-100 mass% of all the PPS fibers which comprise the said wet nonwoven fabric are unstretched PPS fibers, More preferably, they are 25 mass%-100 mass%. Depending on the purpose, fibers other than PPS fibers can be included as long as the effects of the present invention are not impaired. For example, fibers such as cellulose, polyethylene terephthalate (PET), aramid, polyimide, wholly aromatic polyester, polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) can be included. The amount of other fibers is 45% by mass or less.
The unstretched PPS fiber used in the present invention refers to a PPS fiber obtained after melt spinning through a die with an extruder-type spinning machine or the like, or without stretching at all.

  The single fiber fineness of the PPS fiber in the wet nonwoven fabric of the present invention is preferably 0.05 dtex or more and 10 dtex or less. If it is thinner than 0.05 dtex, the fibers are easily entangled and it is difficult to uniformly disperse them. If it is thicker than 10 dtex, the fiber becomes thick and hard, and the entanglement force between the fibers becomes weak, so that sufficient paper strength cannot be obtained and the wet nonwoven fabric is easily broken. It is preferable that all the PPS fibers have a single fiber fineness of 0.05 dtex or more and 10 dtex or less, but fibers outside the above range may be included to such an extent that the above effects are not impaired.

  Moreover, as a fiber length of the PPS fiber in the wet nonwoven fabric of this invention, the inside of the range of 1-20 mm is preferable. By setting it to 1 mm or more, the strength of the wet nonwoven fabric can be increased by entanglement of the fibers. Moreover, by setting it as 20 mm or less, it is possible to prevent the wet non-woven fabric from being uneven due to fibers becoming lumpy. Although it is preferable that all PPS fibers are within the fiber length range of 1 to 20 mm, fibers outside this range may be included to the extent that the above effects are not impaired. In the case of a dry nonwoven fabric, it is difficult to shorten the fiber length as in the above range due to restrictions on the production method, and if a dry nonwoven fabric having a general fiber length of about 50 mm is used, the amount of fluff is increased. Local breakdown is more likely to occur at higher voltages.

The wet nonwoven fabric used in the present invention is a paper-like material obtained by a general papermaking method, preferably having a basis weight of 5 to 200 g / m ² and a thickness of 5 to 500 μm, more preferably 10 to 120 g / m ² . Those having a basis weight of 10 to 300 μm can be suitably used as the insulating material.

  The laminate of the present invention is obtained by joining a wet nonwoven fabric and a synthetic resin film. By joining and laminating the wet nonwoven fabric with a synthetic resin film, the dielectric breakdown strength can be drastically improved and the rigidity (strength strength) can be further increased as compared with the wet nonwoven fabric alone. In addition, the synthetic resin film is bonded and laminated to the wet nonwoven fabric, so that the impact resistance (easy to break) can be dramatically improved as compared with the synthetic resin film alone.

  In particular, the resistance to end tearing, that is, the tearability can be greatly improved, and the laminate of the present invention has a high tearing performance that could not be achieved by a film alone.

  The synthetic resin film in the present invention is a sheet formed by melt-molding a synthetic resin, and may be stretched or unstretched after being formed into a sheet. A stretched synthetic resin film is preferable in terms of high mechanical strength, and an unstretched synthetic resin film is preferable in terms of excellent moldability. The synthetic resin film having a thickness of 2 to 500 μm can be suitably used as the insulating material.

  In the present invention, synthetic resin films in general can be used, but polyethylene terephthalate films or polyphenylene sulfide films are particularly preferable. PET film has excellent dielectric breakdown strength and is suitable for insulating material because it is inexpensive. On the other hand, PPS film is superior to PET film in various properties such as heat resistance, chemical resistance, and hydrolysis resistance, and is harsh. Since it can withstand various use environments, it can be more suitably used as an insulating material.

  The PET resin is a polymer containing ethylene terephthalate units such as p-ethylene terephthalate units and m-ethylene terephthalate units as repeating units. The PET resin in the present invention may be a homopolymer of any of these units or a copolymer having both units.

  A PET film that can be suitably used in the present invention is obtained by melt-molding the above-mentioned PET resin into a sheet shape. After forming into a sheet shape, the PET film may be stretched or unstretched, and the thickness may be What is 2-500 micrometers can be used suitably as an insulating material. The PPS film that can be suitably used in the present invention is a sheet formed by melt-molding the PPS resin. After forming into a sheet, the PPS film may be stretched or unstretched, and may have a thickness. Those having a thickness of 2 to 500 μm can be suitably used as an insulating material.

  Next, a method for producing (making paper) a wet nonwoven fabric used in the present invention will be described.

  As described above, the wet nonwoven fabric used in the present invention is made of PPS fibers, and a part of the PPS fibers is composed of unstretched PPS fibers. The unstretched PPS fiber can be obtained by melt-spinning the above-described PPS resin with an extruder-type spinning machine or the like and processing it without or substantially stretching. On the other hand, other PPS fibers other than unstretched PPS fibers are stretched PPS fibers, and the stretched PPS fibers are melt-spun PPS resin with an extruder-type spinning machine or the like, similarly to the unstretched PPS fibers, It can be obtained by stretching in a range of 3.0 times or more, preferably 5.5 times or less, more preferably 3.5 to 5.0 times. This stretching may be performed in one stage, but may be performed in two or more stages. In the case of using two-stage stretching, the first stage of stretching is preferably 70% or more of the total magnification, preferably 75 to 85%, and the rest is preferably performed by the second stage of stretching. The obtained unstretched PPS fiber and stretched PPS fiber may be cut without being crimped, or may be cut with crimp. As for the presence or absence of crimp in the PPS fiber, there are advantages to those having and not having crimps. PPS fibers having crimps are suitable for obtaining a wet nonwoven fabric having improved strength due to improved entanglement between fibers. On the other hand, PPS fibers that do not have crimps are suitable for obtaining a uniform wet nonwoven fabric with little unevenness because the dispersibility of the fibers in water is good.

  An example of a method for obtaining a wet nonwoven fabric composed of PPS fibers as described above will be shown. First, PPS fibers (stretched PPS fibers and unstretched PPS fibers) are dispersed in water to make a papermaking slurry.

  The total amount of PPS fibers with respect to the entire papermaking slurry is preferably 0.005 to 5 mass%. By making the total amount 0.005% by mass or more, water can be efficiently used in the paper making process. Moreover, by making it 5 mass% or less, the dispersion state of a fiber improves and a uniform wet nonwoven fabric can be obtained.

  The papermaking slurry may be prepared by separately preparing a stretched PPS fiber slurry and an unstretched PPS fiber slurry in advance, and then mixing them with a paper machine, or a slurry containing both directly. It is preferable to make the slurry of each fiber separately and then mix the two in terms of being able to control the stirring time according to the shape and characteristics of each fiber separately. It is preferable in terms of simplicity.

  In order to improve the dispersion state, the papermaking slurry may be added with a dispersant or an oil agent composed of a cationic, anionic or nonionic surfactant, or an antifoaming agent that suppresses the generation of bubbles. Good.

  The papermaking slurry prepared as described above is paper-made using a round-mesh type, long-mesh type, inclined net-type paper machine or hand-made paper machine, which is dried with a Yankee dryer, a rotary dryer, etc. can do.

  It is preferable that 20 mass%-100 mass% of all the PPS fibers which comprise the said wet nonwoven fabric are unstretched PPS fibers, More preferably, they are 25 mass%-100 mass%, More preferably, they are 25 mass%-75 mass%. %. By setting the unstretched PPS fiber to 20% by mass or more of the total PPS fiber constituting the wet nonwoven fabric, the fibers can be fused to each other in a flat film shape, and the wet nonwoven fabric having a smooth surface with few fluffs Moreover, on the joint surface between the wet nonwoven fabric and the synthetic resin film, a laminate having a large adhesion area and a strong adhesion can be obtained. In addition, when the unstretched PPS fiber is 25% by mass or more of the total PPS fiber constituting the wet nonwoven fabric, the area to be fused in a flat film is increased, the amount of fluff on the wet nonwoven fabric surface is reduced, and the adhesion is Since it becomes stronger, it is more preferable. Furthermore, when the unstretched PPS fiber is 25% by mass to 75% by mass of the total PPS fiber constituting the wet nonwoven fabric, the wet nonwoven fabric is excellent in tear strength, and even when a laminate of the wet nonwoven fabric and the synthetic resin film is used. In view of excellent tear strength, it is more preferable from the viewpoints of both adhesion and tear strength.

  In the production method of the laminate of the present invention, the PPS fiber is formed into a sheet by a wet papermaking method, and then the unstretched PPS fiber is fused with the surrounding PPS fiber into a flat film by heating / pressurizing treatment. It is important to use a non-woven fabric and then join the synthetic resin film.

  In the present invention, any means may be used as a means for heating and pressurizing to form a wet nonwoven fabric. For example, a hot press using a flat plate, a calendar, or the like can be employed. Among these, a calendar that can be processed continuously is preferable. As the calendar roll, a metal-metal roll, a metal-paper roll, a metal-rubber roll, or the like can be used. The temperature condition of the heating / pressurizing treatment may be a temperature not lower than the glass transition point of the unstretched PPS fiber and not higher than the melting point, preferably 88 to 250 ° C, more preferably 88 to 220 ° C.

  If the treatment temperature is lower than 88 ° C., the fibers present on the surface portion cannot be fused together into a flat film, and a wet nonwoven fabric with a smooth surface cannot be obtained. On the other hand, when the temperature exceeds 250 ° C., the unstretched PPS fiber is too soft and sticks to a heating / pressurizing device such as a calendar roll or a hot press plate, so that stable mass production cannot be performed. Moreover, the thing with the rough surface will be made also as a wet nonwoven fabric. The pressure when calendering is employed as the heating / pressurizing treatment is preferably 10 to 720 kgf / cm. By setting it to 10 kgf / cm or more, fibers can be fused in a flat film shape. On the other hand, by setting it to 720 kgf / cm or less, it is possible to prevent the wet nonwoven fabric from being broken in the heating / pressurizing treatment and to stably perform the treatment. The process speed of the calendar is preferably 1 to 30 m / min, more preferably 2 to 20 m / min. Good working efficiency can be obtained by setting it as 1 m / min or more. On the other hand, by setting it to 30 m / min or less, heat can also be conducted to the fibers inside the wet nonwoven fabric, and the fibers can be reliably fused.

  Next, the lamination | stacking method of the PPS humidity type nonwoven fabric and synthetic resin film which were obtained by the said method is demonstrated.

  The laminate of the present invention comprises at least the PPS wet nonwoven fabric layer and the synthetic resin film layer, and can be obtained by bonding each layer directly or via an adhesive.

  In the method of joining laminates via an adhesive, the adhesive can be solvent-free or solvent-based. However, in view of the heat resistance of the adhesive and the workability of laminating the adhesive, a curable solvent-based adhesive is used. Agents are preferred. Examples of the curable adhesive include urethane, epoxy, acrylic, silicone, and polyester.

  The method of joining with the above adhesive is to apply the adhesive on one side of a synthetic resin film (or PPS wet nonwoven fabric), dry it, and then apply the PPS wet nonwoven fabric (or synthetic resin film) with a heating roll or a hot press. Match. In the case of further laminating and joining, the above-mentioned synthetic resin film and PPS wet nonwoven fabric two-layer PPS wet nonwoven fabric or synthetic resin film (or another synthetic resin film to be joined or another PPS) It is also possible to apply a similar adhesive to a wet nonwoven fabric), dry it, and then apply another synthetic resin film or PPS wet nonwoven fabric with a heating roll or press to form a laminate with a three-layer structure. It is. Similarly, a laminate of four or more layers can be formed.

  Examples of the method for applying the adhesive include a gravure roll method and a reverse roll coater method. The drying of the solvent after coating varies depending on the type of solvent used, and usually a condition is selected in which the residual solvent is completely eliminated at a temperature near the boiling point of the solvent. The bonding conditions are preferably a temperature of 50 ° C. to 250 ° C. and a linear pressure of 1 to 50 kgf / cm.

  Also, the adhesive is cured as necessary. Although it varies depending on the type, composition and thickness of the adhesive, it is preferably within the range of 0.5 to 100 hours at room temperature to 200 ° C.

  In addition, a method of directly forming a laminate without using an adhesive is, for example, performing surface treatment such as corona treatment or plasma treatment on a synthetic resin film surface and a PPS wet nonwoven fabric surface to be laminated, and -CO, -C on the surface. By introducing appropriate functional groups such as = O and -COOH, the synthetic resin film and the PPS wet nonwoven fabric can be joined by heat treatment. The plasma treatment is more preferable than the corona treatment because the kind and amount of functional groups introduced onto the polymer surface can be controlled by selecting the treatment gas. Examples of the gas that can be selected by the plasma treatment include oxygen gas, oxygen compound gas, argon gas, ammonia gas, nitro compound gas, and a mixed gas thereof, which can be appropriately selected and used.

  As the heat treatment (heating roll or heating press), heat fusion is performed in the range of a temperature of 120 ° C. to 250 ° C. and a linear pressure of 1 to 1200 kgf / cm, and bonding is performed. At this time, if it is a high pressure, it can be bonded at a low temperature, and if it is a high temperature, it can be bonded at a low pressure.

  In addition, in the case of bonding by plasma treatment, as a PPS wet nonwoven fabric used for bonding, in a heating process for manufacturing a PPS wet nonwoven fabric such as a drying process or a calendar process, the crystallization temperature of PPS is 120 ° C. or higher. It is also preferable to use one that is not given heat. By setting the drying temperature and the calendar temperature to less than 120 ° C., it is possible to move to the joining process while maintaining a large amount of the amorphous component of the PPS fiber constituting the PPS wet nonwoven fabric. At the same time as joining the film, the adhesive surface of the PPS wet nonwoven fabric can be fused into a flat film. This method is preferable from the viewpoint that the fused flat film-like surface is more closely adhered to the surface of the synthetic resin film and the anchor effect can be further enhanced.

  Since this method does not provide an adhesive layer, it has the advantage that the thermal degradation of the adhesive does not affect properties such as heat resistance and mechanical strength of the laminate of the present invention. Lamination with a PPS film is preferable because a laminate can be formed without impairing various properties of PPS.

  Moreover, when bonding together by plasma processing, the adhesive force of a PPS wet nonwoven fabric and a synthetic resin film can be improved greatly by performing additional heat processing after performing heat processing. Specifically, the base material breaks such that the wet nonwoven fabric peeled off from the film breaks when the adhesive force is improved by an additional heat treatment for 1 to 30 minutes at a temperature of 160 ° C. to 200 ° C. and the adhesive interface is peeled off. Occurred. That is, the adhesive strength exceeded the mechanical strength of the wet nonwoven fabric, and the adhesive strength was high. In addition, it is known that the adhesion by general plasma treatment will decrease in the adhesion force immediately after processing, but by performing additional heat treatment, the adhesion force is maintained even after one year or more after processing. The base material was broken. The reason why the adhesion is improved by these additional heat treatments and is maintained without lowering the adhesion is not necessarily clarified, but as the water molecules contained in the fiber sheet are removed by additional heat treatment, It is considered that the functional group introduced by the plasma treatment is not affected by water molecules and can contribute to adhesion sufficiently.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

[Measurement and evaluation method]
(1) Basis weight According to JIS L 1906: 2000, one 25 cm × 25 cm test piece is collected, and each mass (g) in a standard state is measured, and the mass per 1 m ² (g / m ² ). expressed.

(2) Thickness According to JIS L 1906: 2000, which is applied mutatis mutandis according to JIS L 1906: 2000, thickness was measured under a pressure of 2 kPa with a 22 mm diameter pressurizer using a thickness measuring device at 10 different points of the sample. In order to calm the thickness, after waiting for 10 seconds, the thickness was measured, and an average value was calculated.

(3) Adhesion
It measured according to JIS K2111: 2002 (12.2 paragraphs: measurement of adhesive force). Take 5 specimens of 50mm x 200mm, tear the center of the layer 20mm in the length direction as much as possible over the whole width of the specimen, and pull it while holding the part that is not torn so that the tearing point is perpendicular Using a testing machine (AGS-J5kN, manufactured by Shimadzu Corporation), it was pulled at 300 m / min, and an average value of five test pieces of adhesive strength was calculated and converted to a width of 10 mm.

(4) Dielectric breakdown strength Measured according to JIS K 6911: 1995. Test specimens of about 10 cm × 10 cm are collected from five different specimens, and the specimens are sandwiched between disc-shaped electrodes with a diameter of 25 mm and a mass of 250 g, air is used as the test medium, and a voltage is applied at 0.25 kV / second. While increasing, an AC voltage having a frequency of 60 Hz was applied, and the voltage when dielectric breakdown was measured. A dielectric breakdown voltage tester (manufactured by Yasuda Seiki Seisakusho) was used for the measurement. The obtained dielectric breakdown voltage was divided by the thickness of the central portion measured in advance, and the dielectric breakdown strength was calculated.

(5) Presence / absence of fluff One 100 mm × 20 mm test piece is taken, the 100 mm long cut surface of the test piece is facing forward, and is visually observed perpendicular to the cut surface, and is seen on one side of the test piece surface The number of fluffs having a length of 0.5 mm or more was counted. If the number was 0, “no”, 1 to less than 5 were “slightly present”, and 5 or more were “present”.

(6) Presence / absence of fusion When the specimen is observed at a magnification of 300 using a scanning electron microscope S-3500N manufactured by Hitachi High-Technologies Corporation, it corresponds to the area of the specimen that can be displayed on one screen. Of the fibers present within 14 mm ² , “Yes” was given if there were three or more unclear portions where the boundary line with adjacent fibers disappeared, and “No” if less than three. Note that the test piece was a non-woven fabric before being bonded, and what was observed was the bonded surface side.
(7) Tear strength (end tear resistance)
Measured according to the end-claw resistance B method of JIS C 2151: 2006. The longitudinal direction of the synthetic resin film used for the measurement sample is the longitudinal direction of the test piece, and five test pieces having a width of 20 mm and a length of 200 mm are collected, and a tensile tester (AGS-J5kN manufactured by Shimadzu Corporation) is used. The first peak of the obtained stress curve was read in Newton units and used as a measured value. The average value of the measured values of the five test pieces was calculated and used as the end tear resistance value.

[Examples 1 to 4, Comparative Example 1]
(1) Production of wet nonwoven fabric (stretched PPS fiber)
As the stretched PPS fiber, a single fiber fineness of 1.0 dtex and a cut length of 6 mm, “Torcon” manufactured by Toray Industries, Inc., product number S301 was used.

(Dispersion of stretched PPS fiber)
The stretched PPS fiber was prepared based on the configuration shown in Table 1 so that the finish was 100 g / m ^2, and 1 L of water was added to 1 g of the stretched PPS fiber together with a household juicer mixer. Stirring was repeated to obtain a dispersion. The stirring time was 10 seconds in order to prevent the fibers from getting tangled.

(Unstretched PPS fiber)
As the unstretched PPS fiber, “Torucon” manufactured by Toray with a single fiber fineness of 3.0 dtex and a cut length of 6 mm, product number S111 was used.

(Unstretched PPS fiber dispersion)
Each of the unstretched PPS fibers is roughly divided into the numbers obtained by rounding up the first decimal place of the mass shown in Table 1, and each aliquot is taken into a household juicer mixer with 1 L of water and stirred. This was repeated to obtain a dispersion. The stirring time was 10 seconds in order to prevent the fibers from getting tangled.

(Paper making)
The fiber dispersion used in each Example / Comparative Example is finished on 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 with a 140-mesh handmade paper net installed on the bottom. The mixture was added to 100 g / m ² , water was further added to make the total amount of the papermaking dispersion 20 L, and the mixture was sufficiently stirred with a stirrer. Next, the water from the handsheet machine was drained, and the wet paper remaining on the papermaking net was transferred to filter paper.

(Dry)
The wet paper is put into a rotary dryer together with the filter paper, and the process of drying at a temperature of 140 ° C., a process passing speed of 0.5 m / min, and a process length of 1.25 m (processing time of 2.5 min) is repeated twice. A dry-processed wet nonwoven fabric was obtained.

(Heating / pressurizing treatment)
The wet nonwoven fabric subjected to the drying treatment was peeled off from the filter paper and passed through a calendar processing machine (manufactured by Yuri Roll Co., Ltd.) consisting of a metal roll and a paper roll. The calendar conditions were a temperature of 160 ° C., a pressure of 344 kgf / cm, and a roll rotation speed of 5 m / min. As a result of judging the presence or absence of fusion of the obtained wet nonwoven fabric according to the above criteria, Examples 1 to 4 had fusion and were fused in a flat film shape on the surface.

(2) Synthetic resin film As the PPS film, Tolera, product number # 60-3A30 manufactured by Toray Industries, Inc., having a thickness of 60 μm and a single-sided corona treatment was used.

(3) Joining of wet nonwoven fabric and synthetic resin film After the adhesive was uniformly applied to one side of the PPS film so as to be 15 g / m ² , 10 seconds were allowed, and the prepared wet nonwoven fabric was stacked. .Pressed at 3 Pa for 6 hours and bonded together. As the adhesive, “Spray paste 55” manufactured by Sumitomo 3M Co., which is composed of 10% acrylic rubber, 54% organic solvent, and 36% isohexane gas was used.
[Example 5]
(Drawn PPS fiber)
As the stretched PPS fiber, a single fiber fineness of 1.0 dtex and a cut length of 6 mm, “Torcon” manufactured by Toray Industries, Inc., product number S301 was used.

(Dispersion of stretched PPS fiber)
The stretched PPS fiber was prepared based on the configuration shown in Table 2 so that the finish was 40 g / m ^2, and 1 L of water was added to 1 g of the stretched PPS fiber together with a household juicer mixer. Stirring was repeated to obtain a dispersion. The stirring time was 10 seconds in order to prevent the fibers from getting tangled.

(Unstretched PPS fiber)
As the unstretched PPS fiber, “Torucon” manufactured by Toray with a single fiber fineness of 3.0 dtex and a cut length of 6 mm, product number S111 was used.

(Unstretched PPS fiber dispersion)
Each of the unstretched PPS fibers is roughly divided into the numbers obtained by rounding up the first decimal place of the mass shown in Table 2, and each aliquot is taken into a household juicer mixer with 1 L of water and stirred. This was repeated to obtain a dispersion. The stirring time was 10 seconds in order to prevent the fibers from getting tangled.

(Paper making)
The fiber dispersion used in each Example / Comparative Example is finished on 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 with a 140-mesh handmade paper net installed on the bottom. The mixture was added to 40 g / m ² , and water was further added to make the total amount of the papermaking dispersion 20 L, and the mixture was sufficiently stirred with a stirrer. Next, the water from the handsheet machine was drained, and the wet paper remaining on the papermaking net was transferred to filter paper.

(Dry)
The wet paper is put into a rotary dryer together with the filter paper, and the process of drying at a temperature of 140 ° C., a process passing speed of 0.5 m / min, and a process length of 1.25 m (processing time of 2.5 min) is repeated twice. A dry-processed wet nonwoven fabric was obtained.

(Heating / pressurizing treatment)
The wet nonwoven fabric subjected to the drying treatment was peeled off from the filter paper and passed through a calendar processing machine (manufactured by Yuri Roll Co., Ltd.) consisting of a metal roll and a paper roll. The calendar conditions were a temperature of 160 ° C., a pressure of 344 kgf / cm, and a roll rotation speed of 5 m / min. As a result of judging the presence or absence of fusion of the obtained wet nonwoven fabric according to the above criteria, Examples 1 to 4 had fusion and were fused in a flat film shape on the surface.

(2) Synthetic resin film As the PPS film, Tolera, product number # 60-3A30 manufactured by Toray Industries, Inc., having a thickness of 60 μm and a single-sided corona treatment was used.

(3) Bonding of wet nonwoven fabric and synthetic resin film Plasma treatment is performed on one side of the PPS film and one side of the wet nonwoven fabric at a plasma treatment strength of 650 W · min / m ² , and then the respective treated surfaces and the treated surfaces are in close contact with each other. In this way, the nonwoven fabrics were stacked and passed through a calendar processing machine (manufactured by Yuri Roll Co., Ltd.) consisting of a metal roll and a paper roll, and the PPS film and the wet nonwoven fabric were bonded together to obtain a laminate. The calendar conditions were a temperature of 210 ° C., a pressure of 344 kgf / cm, and a roll rotation speed of 5 m / min.
[Example 6]
The laminate obtained by the same method as in Example 5 was allowed to stand for 1 minute in a drier having a bath temperature of 200 ° C., and then taken out from the drier.

  As is clear from Table 1, for Examples 1 to 3, there is no fluff, and the larger the proportion of unstretched PPS fibers, the larger the area fused to a flat film and the higher the adhesion. Excellent results. In Example 4, although some fluff was confirmed, the adhesive strength was relatively high. On the other hand, Comparative Example 1 had extremely low adhesion because there were many fuzz and no fusion.

  As described above, in Examples 1 to 4, it was possible to obtain a laminate that was strong in adhesion and dielectric breakdown strength and had less surface fluff. Moreover, when the fiber sheet surface of the test piece was observed at a magnification of 300 using a scanning electron microscope, it was confirmed that Examples 1 to 4 had fusion due to unstretched PPS short fibers.

  Furthermore, Examples 1 to 4 are excellent in adhesion, and because the wet nonwoven fabric portion has high mechanical strength, it is excellent in end tear resistance as a composite, that is, tear strength. In particular, Examples 2 to 4 were excellent in both adhesion and tear strength.

  As shown in Table 2, the substrate was destroyed by performing additional heat treatment, such that the adhesive strength was greatly improved, and the wet nonwoven fabric peeled off from the film was broken during the measurement of adhesion. In this case, the adhesive strength exceeded the mechanical strength of the wet nonwoven fabric, and the adhesive strength was high.

  The laminate of the present invention can be used as an electrical insulating paper used for motors, capacitors, transformers, cables, high voltage transmission transformers and the like.

  Furthermore, the laminate of the present invention can be used as a laminate used for heat-resistant sheets and heat-resistant tubes for electrical equipment.

Claims (5)

A laminate in which a wet nonwoven fabric made of polyphenylene sulfide fiber and a synthetic resin film are joined, wherein at least a part of the polyphenylene sulfide fiber is unstretched polyphenylene sulfide fiber, and unstretched polyphenylene sulfide fiber on the surface of the wet nonwoven fabric Is a laminate characterized in that it is fused to the surrounding polyphenylene sulfide fiber in a flat film form. The laminate according to claim 1, wherein 20 wt% to 100 wt% of the polyphenylene sulfide fibers constituting the wet nonwoven fabric are unstretched polyphenylene sulfide fibers. The laminate according to claim 1 or 2, wherein the synthetic resin film is a polyphenylene sulfide film or a polyethylene terephthalate film. Polyphenylene sulfide fiber, which is at least partly unstretched polyphenylene sulfide fiber, is formed into a sheet by wet papermaking, and then the unstretched polyphenylene sulfide fiber is fused with the surrounding polyphenylene sulfide fiber into a flat film by heat and pressure treatment. The method for producing a laminate according to claim 1, wherein the wet nonwoven fabric is formed, and then laminated and bonded to a synthetic resin film. The method for producing a laminate according to claim 4, wherein an adhesive is applied to a surface of the wet nonwoven fabric or the synthetic resin film, and then the wet nonwoven fabric and the synthetic resin film are bonded together.