CN118804837A - Composite sheet manufacturing method, laminate manufacturing method, composite sheet and laminate - Google Patents

Abstract

The method for producing a composite sheet of the present invention is a method for producing a composite sheet comprising performing an operation of disposing a dispersion containing polytetrafluoroethylene particles on the surface of a glass cloth and heating the dispersion two or more times, wherein when the operation is performed two times, the dispersion further containing a polymer containing a carbonyl group is used only in the first operation or only in the last operation, and when the operation is performed three or more times, the dispersion further containing a polymer containing a carbonyl group is used only in the first operation, only in the last operation, or only in the first and last operations.

Description

Composite sheet manufacturing method, laminate manufacturing method, composite sheet and laminate

Technical Field

The present disclosure relates to a method for producing a composite sheet, a method for producing a laminate, a composite sheet, and a laminate.

Background Art

Polytetrafluoroethylene (hereinafter referred to as "PTFE") is used in various industrial applications due to its excellent physical properties such as mold release, electrical properties, water and oil repellency, chemical resistance, weather resistance, and heat resistance. PTFE-glass cloth composite sheets (hereinafter referred to as "composite sheets") made by carrying PTFE on glass cloth and laminates of composite sheets and substrates are widely used as conveyor belts in food manufacturing, etc. In addition, laminates of composite sheets and metal substrates are used as substrates for printed circuit boards.

As one embodiment of a method for producing a composite sheet, there is known a method in which a dispersion of PTFE particles is impregnated into a glass cloth and then heated multiple times (see Japanese Unexamined Patent Application Publication No. 2020-513437 and International Publication No. 2020/004339).

However, since PTFE has low surface tension and low interaction with other materials, it tends to be difficult to firmly adhere to the surface of the substrate, and the composite sheet and the substrate in the laminate are likely to be peeled off due to the linear expansion of the composite sheet, and the PTFE is likely to be peeled off from the composite sheet. In particular, the composite sheet used in the conveyor belt during food manufacturing is repeatedly heated and cooled during food manufacturing, and the above peeling is likely to occur more significantly.

Summary of the invention

Technical problem to be solved by the invention

Therefore, the technical problem to be solved by the present invention is to provide a composite sheet with excellent heat resistance that can inhibit at least one of the peeling of the composite sheet and the substrate in the stack and the peeling of PTFE from the composite sheet, a stack having the composite sheet, a method for manufacturing the composite sheet that can manufacture the composite sheet, and a method for manufacturing a stack using the composite sheet.

Solutions to technical problems

The means for solving the above technical problems include the following methods.

<1> A method for producing a composite sheet, wherein the operation of disposing a dispersion of particles containing polytetrafluoroethylene on the surface of a glass cloth and heating is performed two or more times, and when the operation is performed twice, the dispersion containing at least one selected from the group consisting of a polymer containing a carbonyl group and a precursor thereof is used only in the first operation or only in the last operation, and when the operation is performed three or more times, the dispersion containing at least one selected from the group consisting of a polymer containing a carbonyl group and a precursor thereof is used only in the first operation, only in the last operation, or only in the first and last operations.

<2> The method for producing a composite sheet as described in <1> above, wherein the operation is performed three or more times, and the dispersion containing the polytetrafluoroethylene particles and at least one selected from the polymer having a carbonyl group and a precursor thereof is used only in the first and last operations.

<3> The method for producing a composite sheet according to <1> or <2>, wherein the polymer having a carbonyl group is a hot-melt tetrafluoroethylene polymer.

<4> The method for producing a composite sheet according to any one of <1> to <3> above, wherein the polymer having a carbonyl group is a hot-melt polymer having a melting temperature of 200° C. or higher.

<5> The method for producing a composite sheet as described in any one of <1> to <4> above, wherein the heating of the dispersion includes heating for calcining at least one of the polytetrafluoroethylene particles, the polymer having a carbonyl group and a precursor of the polymer having a carbonyl group.

<6> The method for producing a composite sheet according to any one of <1> to <5>, wherein the polymer having a carbonyl group is contained in the form of particles having an average particle size (D50) of 0.03 μm to 200 μm.

<7> A method for producing a laminate, comprising laminating a composite sheet produced by the method for producing a composite sheet according to any one of <1> to <6> above and a substrate.

<8> A composite sheet comprising glass cloth and polytetrafluoroethylene supported on the glass cloth, further comprising a polymer having a carbonyl group, wherein the polymer having the carbonyl group is concentrated on at least one of a surface of the glass cloth and a surface of the composite sheet.

<9> A laminate comprising the composite sheet according to <8> above and a substrate provided on a surface of the composite sheet.

<10> The laminate according to <9> above, wherein the composite sheet has a peel strength from the substrate of 10 N/cm or more.

Effects of the Invention

According to one embodiment of the present disclosure, there can be provided a composite sheet having excellent heat resistance and capable of suppressing at least one of peeling of a composite sheet and a substrate in a stack and peeling of PTFE from the composite sheet, a stack having the composite sheet, a method for manufacturing the composite sheet that can manufacture the composite sheet, and a method for manufacturing a stack using the composite sheet.

DETAILED DESCRIPTION

The specific embodiments of the present disclosure are described in detail below. However, the embodiments of the present disclosure are not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps, etc.) are not required except for the cases specifically indicated. The same is true for numerical values and their ranges, which do not limit the embodiments of the present disclosure.

In the present disclosure, a numerical range expressed by “to” includes a range in which the numerical values described before and after “to” are the minimum value and the maximum value, respectively.

In the present disclosure, each component may include a plurality of corresponding substances. When a plurality of substances corresponding to each component are present in the composition, the content rate or content of each component refers to the total content rate or content of the plurality of substances present in the composition, unless otherwise specified.

In the present disclosure, particles corresponding to each component may contain multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value of the mixture of the multiple types of particles present in the composition unless otherwise specified.

In the present disclosure, the term "stacked" means stacking layers, and two or more layers may be bonded together, or two or more layers may be detachable.

In the present disclosure, "average particle size (D50)" is the volume-based cumulative 50% diameter of particles obtained by laser diffraction and scattering. That is, the particle size distribution is measured by laser diffraction and scattering, and a cumulative curve is obtained with the total volume of the particle group as 100%, and the particle size at the point where the cumulative volume reaches 50% on the cumulative curve.

The D50 of the particles is determined by dispersing the powder in water and analyzing the powder by a laser diffraction/scattering method using a laser diffraction/scattering particle size distribution analyzer (LA-920 analyzer manufactured by Horiba, Ltd.).

In the present disclosure, the “melting temperature of a polymer” is a temperature corresponding to the maximum value of a melting peak of a polymer measured by differential scanning calorimetry (DSC).

In the present disclosure, the “melt flow rate” is the melt flow rate of a polymer specified in JIS K 7210-1:2014 (ISO 1133-1:2011).

In the present disclosure, the “glass transition temperature (Tg)” is a value measured by analyzing a polymer using a dynamic viscoelasticity measurement (DMA) method.

In the present disclosure, the "viscosity" is determined by measuring the dispersion using a Brookfield viscometer at 25° C. and a rotation speed of 30 rpm. The measurement was repeated three times, and the average of the three measured values was taken.

In the present disclosure, "thixotropic ratio" refers to a value calculated by dividing the viscosity _η1 measured at 25°C and 30 rpm by the viscosity _η2 measured at 60 rpm (η1/η2). Each viscosity was measured three times, and the average of the three measured values was taken.

In the present disclosure, a "polymer" is a compound obtained by polymerizing monomers. That is, a "polymer" has a plurality of units based on monomers.

In the present disclosure, the "unit" in a polymer refers to an atomic group based on a monomer formed by polymerization of the monomer. The unit may be a unit directly formed by a polymerization reaction, or a unit in which a part of the unit is converted into another structure by treating the polymer.

In the present disclosure, “(meth)acrylic acid” is a term used to conceptually include both acrylic acid and methacrylic acid.

The method for producing a composite sheet of the present invention is a method for producing a composite sheet in which a dispersion containing particles of polytetrafluoroethylene (hereinafter also referred to as "PTFE particles") is arranged on the surface of a glass cloth and heated twice or more. When the operation is performed twice, the dispersion containing at least one selected from the group consisting of polymers containing carbonyl groups and precursors thereof is used only in the first operation or only in the last operation. When the operation is performed three or more times, the dispersion containing at least one selected from the group consisting of polymers containing carbonyl groups and precursors thereof is used only in the first operation, only in the last operation, or only in the first and last operations.

According to the method for producing a composite sheet disclosed in the present invention, a composite sheet having excellent heat resistance can be produced which can suppress at least one of the peeling between the composite sheet and the substrate and the peeling of PTFE from the composite sheet in the laminate. The mechanism of action is not clear, but is roughly estimated as follows.

In the first operation, by using a dispersion containing PTFE particles and a polymer having a carbonyl group, a composite sheet in which the polymer having a carbonyl group is concentrated on the surface of the glass cloth can be manufactured, which can inhibit the peeling of PTFE from the composite sheet. It is speculated that this is because a dense matrix is formed by the carbonyl group possessed by the above-mentioned polymer, and the polymer chains of the polymer and PTFE are easily entangled with each other. In particular, if the polymer having a carbonyl group is a hot-melt tetrafluoroethylene polymer, the tetrafluoroethylene polymer melt-attached to the glass cloth is used as a starting point to promote the loading of PTFE, thereby making it easier to highly load PTFE.

In the last operation, by using a dispersion containing PTFE particles and a polymer having a carbonyl group, a composite sheet in which the polymer having a carbonyl group is concentrated on the surface of the composite sheet can be manufactured, which can inhibit the peeling of the laminated body formed by laminating the composite sheet and the substrate of the present disclosure. It is speculated that this is because a dense matrix is formed by the carbonyl group possessed by the above-mentioned polymer, and the adhesion is improved by interaction with other materials. In particular, if the polymer having a carbonyl group is a hot-melt tetrafluoroethylene polymer, it is easier to improve the adhesion to other substrates while highly loading PTFE.

In addition, compared with the case where the dispersion further containing at least one selected from the group consisting of the polymer having a carbonyl group and its precursor is used in all operations, the heat resistance of the composite sheet is improved by using the dispersion further containing at least one selected from the group consisting of the polymer having a carbonyl group and its precursor only in the first operation, only in the last operation, or only in the first and last operations. It is presumed that this is because the high heat resistance of PTFE is easily manifested due to the increase in the proportion of PTFE in the composite sheet.

First, the dispersion liquid used in the method for producing a composite sheet of the present disclosure will be described below.

The dispersion contains PTFE particles. The PTFE particles may be used alone or in combination of two or more.

PTFE can be a homopolymer of tetrafluoroethylene (hereinafter also referred to as "TFE"), or a copolymer of a very small amount of perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"), hexafluoropropylene (hereinafter also referred to as "HFP"), fluoroalkylethylene and other comonomers and TFE, i.e., so-called modified PTFE. The ratio of TFE units in PTFE is preferably 99.5 mol% or more, more preferably 99.9 mol% or more in all units.

The PTFE particles preferably contain PTFE as a main component and preferably contain 90% by mass or more of PTFE, more preferably 100% by mass of PTFE, relative to the total mass of the PTFE particles.

In addition, PTFE is preferably non-thermal fusible. Here, "non-thermal fusible" means that it cannot be melt-formed, that is, it does not exhibit melt fluidity. Specifically, the melt flow rate measured according to ASTM D3307 at a measurement temperature of 372°C and a load of 49N is less than 0.5g/10min.

In addition, in the present disclosure, PTFE does not include F polymer described later.

The PTFE is preferably PTFE having a number average molecular weight Mn of 200,000 or more as calculated based on the following formula (1).

Mn＝2.1×10 ¹⁰ ×ΔHc ^-5.16 …(1)

In formula (1), Mn represents the number average molecular weight of PTFE, and ΔHc represents the heat of crystallization (cal/g) of PTFE measured by differential scanning calorimetry.

The D50 of the PTFE particles is preferably 0.1 μm or more, more preferably 0.2 μm or more, and the D50 of the PTFE particles is preferably 3 μm or less, more preferably 0.5 μm or less.

The content of the PTFE particles relative to the total mass of the dispersion is preferably 5 to 70% by mass, more preferably 10 to 65% by mass, and even more preferably 20 to 60% by mass.

As the dispersion liquid containing PTFE particles, a commercially available dispersion liquid can be used, and as the aqueous dispersion liquid of PTFE particles, AD-915E manufactured by AGC Corporation or the like can be used.

In the manufacturing method of the composite sheet disclosed in the present invention, the operation of disposing the dispersion and heating is performed more than twice, and the dispersion containing at least one selected from the group consisting of a polymer having a carbonyl group and a precursor thereof is used in at least one of the first operation and the last operation. The polymer having a carbonyl group and its precursor may be used in one kind or in two or more kinds. In addition, the dispersion used in the above-mentioned operations other than the first operation and the last operation may be used without any particular limitation as long as it contains PTFE particles and does not contain at least one selected from the group consisting of a polymer having a carbonyl group and a precursor thereof.

The polymer having a carbonyl group is preferably one or more selected from a tetrafluoroethylene polymer having a carbonyl group (hereinafter also referred to as "F polymer"), a polyimide resin (hereinafter also referred to as "PI"), and a polyamide-imide resin (hereinafter also referred to as "PAI"). From the viewpoint of more effectively suppressing the peeling of the composite sheet and the substrate in the laminate and the peeling of PTFE from the composite sheet, the F polymer is more preferred.

The polymer having a carbonyl group may be in a particulate form or a non-particulate form, but is preferably in a particulate form from the viewpoint of dispersibility in a dispersion liquid.

In the present disclosure, the term "precursor" refers to a compound that becomes a polymer having a carbonyl group by reaction, and examples thereof include polyamic acids (polyamic acid, polyamic acid ester, etc.) that become PI, PAI, etc. by imidization.

The melting temperature of the polymer having a carbonyl group is preferably 200° C. or higher, and more preferably 260° C. or higher. The melting temperature of the polymer having a carbonyl group is preferably 325° C. or lower, and more preferably 320° C. or lower. By making the melting temperature of the polymer having a carbonyl group within the above range, the heat resistance, low linear expansion property, and processability of the composite sheet tend to be improved.

Furthermore, when a composite sheet manufactured by using a dispersion containing a polymer having a carbonyl group having a melting temperature of 200°C or more in the last operation described above is used as a conveyor belt for food manufacturing, the demolding durability of the food from the composite sheet can be improved. It is speculated that this is because the PTFE particles concentrated on the surface of the composite sheet generate stress concentration when the food is peeled off. In addition, the polymer having a carbonyl group having a melting temperature of 200°C or more does not melt under normal food manufacturing conditions, and it is speculated that it can play a better effect in improving the peeling durability than the effect of improving the adhesion of the composite sheet surface.

From the viewpoint of further improving the heat resistance of the composite sheet, the glass transition temperature of the polymer having a carbonyl group is preferably 50° C. or higher, more preferably 75° C. or higher. The upper limit of the glass transition temperature of the polymer having a carbonyl group is not particularly limited, but is preferably 150° C. or lower, more preferably 125° C. or lower.

The F polymer is a polymer containing units derived from TFE (hereinafter also referred to as "TFE units"). From the viewpoint of appropriately expressing the properties derived from the TFE units, the content of the TFE units in the F polymer is preferably 90 to 98 mol% relative to all units in the F polymer.

The F polymer preferably has thermal melting property. Thermal melting property refers to a property that the polymer has a temperature at which the melt flow rate is 1 to 1000 g/10 minutes under a load of 49 N.

The fluorine content of the F polymer is preferably 70 to 76% by mass in order to facilitate interaction with PTFE, further suppress detachment of PTFE from the composite sheet, and further improve the heat resistance of the composite sheet.

The carbonyl-containing group is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a urethane group (-OC(O) _NH2 ), an anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) and a carbonate group (-OC(O)O-), and an anhydride residue is more preferred.

The polymer may further have an oxygen-containing polar group other than the carbonyl-containing group. Examples of the oxygen-containing polar group include a hydroxyl-containing group and a phosphonyl-containing group.

The number of carbonyl-containing groups in the F polymer is preferably 10 to 5000 per 1×10 ⁶ main chain carbons, and more preferably 100 to 3000. The carbonyl-containing groups can be quantified based on the composition of the polymer or by the method described in International Publication No. 2020/145133.

The carbonyl-containing group may be contained in the monomer-based unit in the F polymer or in the terminal group of the F polymer main chain, and the former form is preferred. As the latter form, tetrafluoroethylene-based polymers having a carbonyl-containing group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and polymers obtained by subjecting tetrafluoroethylene-based polymers to plasma treatment or ionizing radiation treatment can be exemplified.

As the monomer having a carbonyl group, itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as NAH) are preferred. NAH is more preferred from the viewpoint of excellent adhesion to the glass cloth.

The F polymer is preferably polytetrafluoroethylene (PTFE), a polymer containing TFE units and ethylene-based units (ETFE), a polymer containing TFE units and propylene-based units, a polymer containing TFE units and perfluoro(alkyl vinyl ether) (PAVE)-based units (PAVE units) (PFA), or a polymer containing TFE units and hexafluoropropylene-based units (FEP), more preferably PFA or FEP containing a carbonyl group, and further preferably PFA containing a carbonyl group. These polymers may also contain units based on other comonomers.

The F polymer is preferably a polymer having a carbonyl group containing TFE units and PAVE units, more preferably a unit containing TFE units, PAVE units and units based on monomers having carbonyl groups, and further preferably a polymer containing TFE units, PAVE units and units based on monomers having carbonyl groups and containing 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol% of these units in order relative to all units. As a specific example of such a F polymer, the polymer described in International Publication No. 2018/16644 can be cited.

In the dispersion, the polymer having a carbonyl group is preferably contained in the form of particles having an average particle size (D50) of 0.03 μm to 200 μm, more preferably in the form of particles having 0.1 μm to 200 μm, and particularly preferably in the form of particles having 0.1 μm to 30 μm. Particles having the above D50 have excellent fluidity and are easily evenly distributed on the surface of the glass cloth. In addition, the heat resistance and electrical properties of the particles are easily exhibited.

When using F polymer particles (hereinafter also referred to as "F particles") as the carbonyl group-containing polymer, the F particles preferably contain the F polymer as a main component. The content of the F polymer in the F particles is preferably 80% by mass or more, more preferably 100% by mass.

In the case where the dispersion contains a polymer having a carbonyl group, from the viewpoint of more effectively suppressing the peeling of the composite sheet and the substrate in the laminate and the peeling of PTFE from the composite sheet, the content of the polymer having a carbonyl group relative to the total mass of the dispersion is preferably 1 to 30 mass %, more preferably 3 to 20 mass %, and further preferably 5 to 15 mass %.

When the dispersion contains a polymer having a carbonyl group, the ratio of the content of the polymer having a carbonyl group to the content of PTFE particles in the dispersion (content of the polymer having a carbonyl group/content of PTFE particles) is preferably 50/50 to 5/95, more preferably 40/60 to 10/90, and particularly preferably 30/70 to 15/85 on a mass basis.

In the case where the dispersion contains a polymer having a carbonyl group, from the viewpoint of more effectively suppressing the peeling of the composite sheet and the substrate in the laminate and the peeling of PTFE from the composite sheet, the ratio of the content of the polymer having a carbonyl group in the dispersion to the sum of the contents of PTFE particles and the polymer having a carbonyl group (the content of the polymer having a carbonyl group/the sum of the contents of PTFE particles and the polymer having a carbonyl group) is preferably 1/100 to /100 to /100 on a mass basis.

In addition, from the viewpoint of more effectively suppressing the peeling of the composite sheet and the substrate in the laminate and the peeling of PTFE from the composite sheet, the sum of the contents of PTFE particles and the polymer having a carbonyl group is preferably 10 to 65% by mass, more preferably 20 to 60% by mass, and further preferably 30 to 60% by mass relative to the total mass of the dispersion.

The dispersion may contain a surfactant, thereby improving the dispersibility and operability of the dispersion. The surfactant is preferably a nonionic surfactant. The hydrophilic part of the surfactant preferably has an oxyalkylene group or an alcoholic hydroxyl group. The hydrophobic part of the surfactant preferably has an acetylene group, a polysiloxane group or a fluorine-containing organic group (perfluoroalkyl group, etc.). In other words, the surfactant is preferably an acetylene surfactant, a silicone surfactant and a fluorine-containing surfactant, and more preferably a silicone surfactant. As silicone surfactants, "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", "BYK-3456" (manufactured by BYK Chemical Japan Co., Ltd.), "KF-6011", "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.) can be cited.

When the dispersion contains a surfactant, the content thereof is preferably 1 to 15% by mass relative to the total mass of the dispersion.

The dispersion contains a liquid dispersion medium. In other words, the dispersion is a dispersion in which PTFE particles are dispersed in a liquid dispersion medium, and a dispersion containing PTFE particles and F particles can also be regarded as a dispersion in which PTFE particles and F particles are dispersed in a liquid dispersion medium. In this dispersion, since the PTFE particles and F particles are highly and evenly dispersed in the liquid, the above-mentioned mechanism of action is easily apparent.

The boiling point of the liquid dispersion medium is preferably in the range of 50 to 240° C. The dispersion medium may be used alone or in combination of two or more. When two or more liquid dispersion media are used, the two or more liquid dispersion media are preferably compatible with each other.

Examples of the dispersion medium include water, N,N-dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, cyclopentanone, butyl acetate, methyl isopropyl ketone, methyl ethyl ketone, etc., among which water is preferred.

The content of the liquid dispersion medium relative to the total mass of the dispersion is preferably 30 to 95% by mass, more preferably 35 to 90% by mass.

The dispersion may further contain a polymer different from PTFE and the polymer having a carbonyl group (hereinafter also referred to as "different polymer"). The different polymer may be thermosetting or thermoplastic. One or more different polymers may be used.

The different polymers are not particularly limited as long as they are polymers other than PTFE and polymers containing carbonyl groups, and examples thereof include tetrafluoroethylene polymers, polyester resins (liquid crystal aromatic polyesters, etc.), polyimide resins, epoxy resins, maleimide resins, polyurethane resins, polyphenylene ether resins, polyphenylene ether resins, polyphenylene sulfide resins, and the like.

When the dispersion contains a different polymer, the content thereof is preferably 0.1 to 5% by mass relative to the total mass of the dispersion.

In addition to the above-mentioned components, the dispersion may also contain other components such as a thixotropy imparting agent, a pH adjuster, a pH buffer, a viscosity adjuster, a defoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a colorant, a conductive agent, a release agent, a surface treatment agent, a flame retardant, various inorganic fillers, various organic fillers, etc., within a range that does not impair the effect of the manufacturing method of the composite sheet of the present invention.

The viscosity of the dispersion is more preferably 75 to 10000 mPa·s. In this case, not only is the dispersibility excellent, but the workability and homogeneity of the dispersion on the glass cloth are also easily improved. In addition, the dispersion has excellent miscibility with different types of resin material varnishes.

The thixotropic ratio of the dispersion is preferably 1.0 to 2.2, more preferably 1.5 to 2.0. In this case, the dispersion has excellent dispersibility and good workability, and the homogeneity of the dispersion on the glass cloth can be easily improved. In addition, the dispersion has excellent miscibility with different types of resin material varnishes.

From the viewpoint of adjusting the viscosity or thixotropic ratio within the above range, the dispersion may contain a viscosity modifier or a thixotropic modifier, specifically, a vinyl alcohol-based polymer and a cellulose ether.

Specific examples of vinyl alcohol-based polymers include the "S-LEC (registered trademark) B" series, the "S-LEC (registered trademark) K (KS)" series, the "S-LEC (registered trademark) SV" series (all manufactured by Sekisui Chemical Co., Ltd.), and the "Mowital (registered trademark)" series (manufactured by Kuraray Co., Ltd.).

Specific examples of cellulose ether include “SUNROSE (registered trademark)” series (manufactured by Nippon Paper Industries, Ltd.), “METOLOSE (registered trademark)” series (manufactured by Shin-Etsu Chemical Co., Ltd.), and “HEC CF grade” (manufactured by Sumitomo Seika Chemicals, Ltd.).

When the dispersion contains a viscosity modifier or a thixotropy modifier, the content thereof is preferably 0.01 to 5% by mass relative to the total mass of the dispersion.

The dispersion can be prepared by mixing PTFE, a polymer having a carbonyl group, a liquid dispersion medium, etc. When the dispersion contains a liquid dispersion medium, the above-mentioned mixing can be performed by adding each component to the liquid dispersion medium at once or by adding each component in sequence. The above-mentioned mixing can be performed in batches or continuously.

As the apparatus that can be used for the above-mentioned mixing, there can be mentioned, for example, a stirring apparatus equipped with blades (Henschel mixer, pressure kneader, Banbury mixer, planetary mixer, etc.), a pulverizing apparatus equipped with a medium (ball mill, pulverizer, basket mill, sand mill, sand mill, DYNO mill, DISPERMAT disperser, SC mill, Spike mill or stirring mill, etc.), a dispersing apparatus equipped with other mechanisms (microfluidizer, nanometer, Ultimaizer disperser, ultrasonic homogenizer, dissolver (デゾルバー), disperser, high-speed impeller disperser, thin film gyratory high-speed mixer, etc.).

In the method for producing a composite sheet of the present disclosure, the operations of placing the dispersion on the glass cloth and heating are performed two or more times, and are preferably performed 3 to 10 times, more preferably 4 to 7 times, from the viewpoint of further improving heat resistance.

As a method for disposing the dispersion on the glass cloth, there are, for example, a roller sizing method in which a part of a roller is impregnated with the dispersion so that the dispersion adheres to the roller surface, and then the glass cloth is brought into contact with the roller to adhere the dispersion; a roller impregnation method in which the glass cloth is directly impregnated with the dispersion and then the dispersion is passed through a clamping roller as needed to control the amount of dispersion adhered; a spray method in which the dispersion is formed into a mist and blown onto the glass cloth, etc. Among the above methods, the roller impregnation method is preferred because it is easy to uniformly apply the dispersion. In addition, the roller impregnation method is also preferred because the amount of dispersion adhered to the glass cloth can be easily adjusted by using a clamping roller or the like.

The dispersion liquid may be arranged on the glass cloth in a batch process or in a continuous process. However, it is preferably arranged in a continuous process from the viewpoint of easily suppressing uneven arrangement of the dispersion liquid on the glass cloth and improving productivity.

From the viewpoint of suppressing the peeling of the composite sheet and the substrate in the laminate and the peeling of PTFE from the composite sheet and improving the heat resistance, it is preferred to perform the above operation three or more times and use the above dispersion containing the above-mentioned polytetrafluoroethylene particles and at least one selected from the group consisting of a polymer having a carbonyl group and a precursor thereof only in the first and last operations.

The amount of the dispersion attached to the glass cloth is preferably adjusted to 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, based on 100 parts by mass of the heat-treated glass cloth.

The heating of the dispersion disposed on the glass cloth preferably includes heating for calcining at least one of the PTFE particles, the polymer having a carbonyl group, and the precursor of the polymer having a carbonyl group. In addition, the heating of the dispersion disposed on the glass cloth preferably includes heating for evaporating the liquid dispersion medium contained in the dispersion.

The heat treatment for evaporating the liquid dispersion medium can be performed by keeping the glass cloth on which the dispersion liquid is arranged at a temperature higher than the volatilization temperature of the liquid dispersion medium so as to dry the liquid film arranged on the glass cloth. In the above-mentioned heat treatment, it is not necessary to completely evaporate the liquid dispersion medium. Specifically, the amount of the liquid dispersion medium to be evaporated is preferably 50% by mass or more of the liquid dispersion medium contained in the dispersion liquid.

The heat treatment for evaporating the liquid dispersion medium may be performed in one step at a constant temperature or in two or more steps at different temperatures. The heating temperature is preferably 50 to 280° C. The heating time is preferably 0.1 to 30 minutes.

The heat treatment for firing may be a method using an oven, a method using a ventilation drying furnace, a method of irradiating heat rays such as infrared rays, or a method combining infrared heating and hot air heating.

The calcination may be performed under normal pressure or reduced pressure. The calcination atmosphere may be an oxidizing gas atmosphere, a reducing gas atmosphere, or an inert gas atmosphere.

When the dispersion contains a polymer having a carbonyl group, the calcination temperature is preferably 300 to 350° C., more preferably 310 to 340° C. When the dispersion does not contain a polymer having a carbonyl group, the calcination temperature is preferably 340 to 390° C., more preferably 350 to 380° C. The calcination time is preferably 30 seconds to 30 minutes, more preferably 1 to 15 minutes. The calcination temperature generally refers to the temperature of the dry atmosphere.

The dispersion liquid can be placed on the glass cloth and heated using an apparatus having a dip coater and a firing furnace. As the firing furnace, a vertical firing furnace can be cited. In addition, as the apparatus, a glass cloth coating apparatus manufactured by Tabata Machinery Industry Co., Ltd. can be cited.

In order to improve the affinity with the polymer containing a carbonyl group, the glass cloth used in the manufacturing method of the composite sheet disclosed in the present invention is preferably a glass cloth treated with a silane coupling agent. As the material of the glass cloth, E glass, C glass, A glass, S glass, D glass, NE glass, L glass, low dielectric constant glass, etc. can be cited, but from the perspective of easy availability, E glass, S glass, and NE glass are preferred.

Glass cloth generally contains a sizing agent, so from the viewpoint of improving heat resistance, it is preferred to reduce the amount of the sizing agent by heating before applying the dispersion to the glass cloth. Examples of the sizing agent include starches such as starch, processed starch, dextrin, and amylose, synthetic polymers such as carboxymethyl cellulose, polyvinyl alcohol, and acrylamide-vinyl acetate copolymers, and silane coupling agents.

The composite sheet can be used as antenna parts, printed substrates, aircraft parts, automobile parts, sports equipment, food industry products, coatings, cosmetics, etc. Specifically, it can be used as wire coating materials (wires for aircraft, etc.), electrical insulating tapes, insulating tapes for oil drilling, printed substrate materials, separation membranes (precision filtration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode adhesives (for lithium secondary batteries, fuel cells, etc.), copy rollers, furniture, car dashboards, covers of home appliances, etc., sliding parts (load bearings, sliding shafts, valves, bearings, gears, cams, belt conveyors, food conveyor belts, etc.), tools (shovels, files, chisels, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, molds, toilets, container coating materials, etc.

The method for producing a laminated body disclosed herein includes laminating a composite sheet produced by the method for producing a composite sheet and a substrate. The laminated body may include a plurality of the composite sheets or a plurality of the substrates.

Examples of the material of the substrate include metal substrates (metal foils of copper, nickel, aluminum, titanium, alloys thereof, etc.), resin films (films of polyimide, polyarylate, polysulfone, polyallylsulfone, polyamide, polyetheramide, polyphenylene sulfide, polyallyletherketone, polyamideimide, liquid crystalline polyester, liquid crystalline polyesteramide, etc.), prepreg (precursor of fiber reinforced resin substrate), etc. Examples of the shape of the substrate include flat surface, curved surface, concave-convex surface, etc., and further, the substrate may be in any of foil, plate, film, and fiber shapes.

The lamination of the composite sheet and the substrate can be performed by thermocompression bonding them, or by using a conventionally known adhesive, etc., but is preferably performed by thermocompression bonding. The thermocompression bonding conditions are preferably appropriately changed according to the thickness of the laminate to be manufactured, for example, the temperature is 170 to 450°C, the pressure is 1.5 to 5 MPa, and the time is 60 to 150 minutes.

The composite sheet of the present invention is a composite sheet comprising glass cloth and polytetrafluoroethylene supported on the glass cloth, which further comprises a polymer having a carbonyl group, and the polymer having the carbonyl group is concentrated on at least one of the surface of the glass cloth and the surface of the composite sheet. The composite sheet disclosed in the present invention can be manufactured, for example, by the manufacturing method of the composite sheet. In the manufacturing method of the composite sheet, a dispersion liquid containing a polymer having a carbonyl group is used in the surface configuration and heating of the glass cloth in at least one of the first and last operations, so that the polymer having the carbonyl group is concentrated on at least one of the surface of the glass cloth and the surface of the composite sheet.

The details of the glass cloth, polytetrafluoroethylene, the polymer having a carbonyl group, etc. are as described above, and thus description thereof is omitted here.

The laminated body disclosed in the present invention comprises the composite sheet and a substrate disposed on the surface of the composite sheet. The laminated body disclosed in the present invention may comprise two or more composite sheets, and may comprise two or more substrates. The details of the composite sheet and the substrate are as described above, and thus are omitted here.

In the laminate of the present disclosure, the peel strength of the composite sheet from the substrate is preferably 5 N/cm or more, more preferably 10 N/cm or more.

The above peel strength is measured by the following method. First, the composite sheet and the copper foil with a thickness of 18 μm are overlapped, and the laminate is made by vacuum pressing and hot pressing at 380°C. The laminate is cut into a size of 100 mm long and 10 mm wide to make a test piece. The position 50 mm away from one end of the length direction of the test piece is fixed, and the composite sheet and the copper foil are peeled from the other end of the test piece under the conditions of a tensile speed of 50 mm/min and a peeling angle of 90°. The maximum load (N/cm) during peeling is measured and is taken as the peel strength.

In the manufacturing method of the composite sheet, when a dispersion liquid that does not contain a polymer having a carbonyl group is used in the last operation of disposing the dispersion liquid on the surface of the glass cloth and heating, the peel strength of the manufactured composite sheet from the substrate is about 1 to 5 N/cm. When the peel strength of the composite sheet from the substrate is 5 N/cm or more, it can be inferred that the polymer having a carbonyl group is at least concentrated on the surface of the composite sheet.

Example

The embodiments of the present disclosure are described in detail below by way of examples, but the embodiments of the present disclosure are not limited thereto.

＜F particles＞

F particles 1: particles composed of a polymer (melting temperature: 300°C) having 1000 carbonyl-containing groups per 1×10 ⁶ main chain carbon atoms and containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units in that order (D50: 2.1 μm)

F particles 2: particles composed of a polymer having no oxygen-containing polar group (melting temperature: 300° C.) containing 97.5 mol % and 2.5 mol % of TFE units and PPVE units (D50: 2.0 μm).

＜Dispersion liquid＞

Dispersion 1: Aqueous dispersion containing 60% by mass of non-thermofusible PTFE particles (D50: 0.3 μm) (manufactured by AGC Corporation, "Product No. AD-915E")

<Surfactant>

Surfactant 1: Silicone surfactant

＜Glass cloth＞

Glass cloth 1: Made by Nitto Bosho Co., Ltd., E glass IPC specification 1080

<Production of Dispersion Liquid>

F particles 1, surfactant 1 and water were mixed to obtain a dispersion (40 parts by mass of F particles, 2.5 parts by mass of surfactant, and 57.5 parts by mass of water). Dispersion 1 and the dispersion were mixed to obtain a dispersion A containing PTFE particles and F particles 1 at a ratio of 85:15 (mass basis, PTFE particles: F particles 1).

F particles 2, surfactant 1 and water were mixed to obtain a dispersion (40 parts by mass of F particles, 2.5 parts by mass of surfactant, 57.5 parts by mass of water). Dispersion 1 was mixed with the dispersion to obtain dispersion B containing PTFE particles and F particles 2 at a ratio of 85:15 (mass basis, PTFE particles: F particles 2).

<Example 1>

The glass cloth 1 was impregnated with the dispersion A, and passed through a drying furnace at 120° C. for 5 minutes to be heated and dried, and then fired in a far-infrared furnace at 340° C. for 10 minutes.

Next, the calcined glass cloth 1 was impregnated in the dispersion 1, and passed through a drying furnace at 120° C. for 5 minutes for heating and drying, and then calcined by heating at 380° C. for 10 minutes in a far-infrared furnace.

The impregnation in the dispersion 1 and the heating were repeated 5 times in total to prepare a composite sheet.

<Example 2>

The glass cloth 1 was impregnated with the dispersion 1, and passed through a drying furnace at 120° C. for 5 minutes to be heated and dried, and then fired by heating at 380° C. for 10 minutes in a far-infrared furnace.

The impregnation with the dispersion 1 and the heating were repeated 5 times in total.

Next, dispersion A was applied to the surface of glass cloth 1 coated with dispersion 1 and heated, and dried by passing through a drying furnace at 120° C. for 5 minutes. Thereafter, the mixture was heated in a far infrared oven at 380° C. for 10 minutes and fired to obtain a composite sheet.

<Example 3>

Dispersion A was applied to one surface of the glass cloth 1, and dried by heating in a drying oven at 120° C. for 5 minutes. Thereafter, the glass cloth was fired by heating in a far-infrared oven at 340° C. for 10 minutes.

Next, the fired glass cloth 1 was impregnated in the dispersion 1, and passed through a drying furnace at 120° C. for 5 minutes for heating and drying, and then fired by heating at 380° C. for 10 minutes in a far-infrared furnace.

The impregnation in the dispersion 1 and the heating were repeated 4 times in total.

Next, the fired glass cloth 1 was impregnated in the dispersion A, and passed through a drying furnace at 120° C. for 5 minutes for heating and drying, and then fired in a far-infrared oven at 380° C. for 10 minutes to prepare a composite sheet.

<Example 4>

The glass cloth 1 was impregnated with the dispersion 1, and passed through a drying furnace at 120° C. for 5 minutes to be heated and dried, and then fired in a far-infrared furnace at 380° C. for 10 minutes.

The impregnation in the above dispersion 1 and heating were repeated 6 times in total to prepare a composite sheet.

<Example 5>

The glass cloth 1 was impregnated with the dispersion A, and passed through a drying furnace at 120° C. for 5 minutes to be heated and dried, and then fired in a far-infrared furnace at 340° C. for 10 minutes.

The impregnation with the dispersion A and heating were repeated 6 times in total to prepare a composite sheet.

<Example 6>

A composite sheet was prepared in the same manner as in Example 3 except that the dispersion liquid A was changed to the dispersion liquid B.

＜Evaluation of PTFE's peeling inhibition＞＞

The composite sheets prepared in Examples 1 and 3 to 6 were placed in a furnace at 260° C. for 10 seconds, left to stand, and then taken out and cooled to 20° C. After the above heating and cooling were repeated 5 times, the surface of the composite sheet was polished, and the surface of the composite sheet was visually observed and evaluated according to the following evaluation criteria and summarized in Table 1.

(Evaluation Criteria)

A: No peeling of PTFE from the composite sheet was observed.

B: Peeling of PTFE from the composite sheet was observed.

＜Heat resistance evaluation＞

The composite sheets produced in Examples 1 to 6 were ground while being heated to 250° C. The surfaces of the composite sheets after grinding were visually observed and evaluated according to the following evaluation criteria and summarized in Table 1. In Table 1, “-” means that no evaluation was performed. The same applies to the following evaluations.

(Evaluation Criteria)

A: No or almost no scratches were observed on the surface of the composite sheet.

B: Scratches were observed on the surface of the composite sheet.

<Evaluation of substrate peeling inhibition>>

The composite sheets produced in Examples 2 to 6 were overlapped with a copper foil having a thickness of 18 μm, and the laminates were formed by thermocompression bonding by vacuum pressing at 380° C.

The laminate was cut into a test piece of 100 mm in length and 10 mm in width. The test piece was fixed at a position 50 mm apart from one end in the longitudinal direction, and the composite sheet and the copper foil were peeled off from the other end of the test piece at a tensile speed of 50 mm/min and a peeling angle of 90°. The maximum load (N/cm) during peeling was measured, evaluated according to the following evaluation criteria and summarized in Table 1. The maximum load is also summarized in Table 1.

(Evaluation Criteria)

A: The maximum load is above 10N/cm.

B: Maximum load is less than 10N/cm.

＜Peeling durability test＞

Sugar was placed on the surface of the composite sheets produced in Examples 2 to 6, heated to 180° C., and the heated sugar was peeled off. The heating and peeling of the sugar were repeated, and the number of times until the sugar could no longer be peeled off was calculated, and the evaluation was performed according to the following evaluation criteria and summarized in Table 1.

(Evaluation Criteria)

A: The heating and peeling of sugar can be repeated more than 10 times.

B: Heating and peeling of sugar cannot be repeated 10 times.

【Table 1】

The disclosure of Japanese Patent Application No. 2022-013144 filed on January 31, 2022 is incorporated herein by reference in its entirety. All documents, patent applications, and technical specifications described in this specification are incorporated herein by reference to the same extent as if the portions incorporated by reference in each document, patent application, and technical specification were specifically and separately described.

Claims (10)

1. A method for producing a composite sheet, wherein a dispersion of polytetrafluoroethylene-containing particles is disposed on the surface of a glass cloth and the heating is performed 2 times or more,

In the case of performing the operation 2 times, the dispersion further containing at least one selected from the group consisting of a polymer having a carbonyl group and a precursor thereof is used only in the 1 st operation or only in the last 1 operations,

In the case of performing the above-described operation 3 times or more, the dispersion further containing at least one selected from the group consisting of a polymer having a carbonyl group and a precursor thereof is used only in the 1 st-time described operation, only in the last 1-time described operation, or only in the 1 st-time and the last 1-time described operation.

2. The method for producing a composite sheet according to claim 1, wherein the operation is performed 3 times or more, and the dispersion liquid containing the polytetrafluoroethylene particles and at least one selected from the group consisting of the polymer having a carbonyl group and a precursor thereof is used only in the 1 st and last 1 th operations.

3. The method for producing a composite sheet according to claim 1 or claim 2, wherein the polymer having a carbonyl group is a heat-fusible tetrafluoroethylene polymer.

4. The method for producing a composite sheet according to claim 1 or claim 2, wherein the polymer having a carbonyl group is a hot-melt polymer having a melting temperature of 200 ℃ or higher.

5. The method for producing a composite sheet according to claim 1 or claim 2, wherein the heating of the dispersion liquid includes heating for firing at least one selected from the group consisting of particles of the polytetrafluoroethylene, the polymer having a carbonyl group, and a precursor of the polymer having a carbonyl group.

6. The method for producing a composite sheet according to claim 1 or claim 2, wherein the polymer having carbonyl groups is contained in a particle form having an average particle diameter D50 of 0.03 μm to 200 μm.

7. A method for producing a laminate, wherein the composite sheet produced by the method for producing a composite sheet according to claim 1 or claim 2 is laminated with a base material.

8. A composite sheet comprising a glass cloth and polytetrafluoroethylene supported on the glass cloth,

It further comprises a polymer having carbonyl group, and the polymer having carbonyl group is concentrated in at least one of the surface of the glass cloth and the surface of the composite sheet.

9. A laminate comprising the composite sheet of claim 8 and a substrate provided on a surface of the composite sheet.

10. The laminate according to claim 9, wherein the composite sheet has a peel strength of 10N/cm or more from the substrate.