JP2023123043A - Heat-resistant process sheet for metalworking - Google Patents

Abstract

To provide a heat-resistant process sheet for metalworking that has flexibility, minimizes fiber dropout at high temperatures, and avoids scratching a metallic surface.SOLUTION: A heat-resistant process sheet for metalworking includes a substrate containing glass fibers having a flat cross section and fibrillated fibers and a surface layer containing a clay mineral and is characterized by satisfying the following formulas (1) and (2): 25≤surface layer content ratio≤80 (1) (in the formula (1), the surface layer content ratio [mass%] is calculated as the ratio of the coating amount of the surface layer [g/m2] to the basis weight of the substrate [g/m2], multiplied by 100); 0.5≤A/B (2) (in the formula (2), A[μm] denotes the difference in thickness between the heat-resistant process sheet and the substrate, and B[g/m2] denotes the coating amount of the surface layer).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a heat-resistant process sheet for metalworking, which is used as an underlay for products in the manufacturing process of steel, non-ferrous metals, etc., in order to prevent the products from being damaged in a high-temperature atmosphere. Hereinafter, in this specification, "heat-resistant process sheet for metalworking" may be abbreviated as "heat-resistant process sheet".

In the manufacturing process of iron and steel, non-ferrous metals, etc., when stacking high-temperature rolled sheet-like products, when products are annealed at high temperatures, etc., metal processing is used as an underlay for products to prevent scratches on products. A heat-resistant process sheet is used. The heat-resistant process sheet is required to have heat resistance, bending resistance, wear resistance, flexibility, surface smoothness, and the like.

As the heat-resistant process sheet, for example, in Patent Document 1, polybenzazole fiber and aromatic polyimide fiber, which are heat-resistant organic fibers, are entangled at a weight fraction ratio of 50%/50% to 90%/10%. A heat resistant felt is disclosed. However, the heat-resistant felt composed only of organic fibers is greatly deteriorated by heat and load, and when the treatment temperature exceeds 450° C., the strength is lowered and the durability is insufficient. In addition, there is a problem that the fibers dropped due to deterioration contaminate the product.

On the other hand, as a method using inorganic fibers, Patent Document 2 discloses a highly heat-resistant fiber cushioning material obtained by blending ceramic fibers and aramid fibers and then needle-punching them, and Patent Document 3 discloses basalt. A pad material made of heat-resistant needle felt is disclosed, which is mainly composed of fibers and mixed with one or more kinds of inorganic fibers, metal fibers, and heat-resistant organic fibers. Inorganic fibers are excellent in heat resistance, but on the other hand, they are rigid. Compared with staple fibers of organic fibers, entanglement between fibers is less likely to occur, and there is a problem that fallen fibers contaminate products.

Further, in Patent Document 4, a heat-resistant cushioning material is formed by laminating heat-resistant organic fiber layers in the state of a web on both sides of an inorganic fiber layer to form a structure of three or more layers, and entangling and integrating them by needle punching. is disclosed. With this method, the outermost surface is covered with heat-resistant organic fibers, which suppresses the decrease in strength after high-temperature treatment and the fall-off of inorganic fibers. was rare.

JP-A-7-324267 JP-A-7-34367 JP-A-11-200211 JP 2017-95840 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-resistant process sheet for metalworking, which has flexibility, is less prone to fiber shedding at high temperatures, and prevents the metal surface from being scratched.

As a result of intensive research to solve the above problems, the following invention was found.

A heat resistant material for metalworking, which has a base material containing glass fibers and fibrillated fibers with a flat cross section, and a surface layer containing a clay mineral, and which satisfies the following formulas (1) and (2): process sheet.
25≦surface layer content≦80 (1)
(In formula (1), the surface layer content [% by mass] is the coating amount of the surface layer [g/m ² ]/the basis weight of the base material [g/m ² ]×100. )
0.5≦A/B (2)
(In formula (2), A [μm] is the thickness of the heat-resistant process sheet minus the thickness of the substrate, and B [g/m ² ] is the coating amount of the surface layer.)

The heat-resistant process sheet for metalworking of the present invention has a base material containing glass fibers and fibrillated fibers, and a surface layer containing a clay mineral. By entangling the fibrillated fibers with the glass fibers to form a composite, it is possible to prevent the fibers from coming off and improve the strength. In addition, by covering the base material with a surface layer containing a clay mineral with excellent heat resistance, heat resistance in a high temperature environment, especially at 450° C. or higher, can be improved, and fiber shedding can be further reduced. Since the flexibility of the metal can be maintained, it can follow the thermal expansion and contraction of the metal and prevent the metal surface from being damaged.

In addition, by satisfying the formulas (1) and (2), the content of clay minerals on the outermost surface becomes higher than the content of the center of the base material, so that the core does not become too hard and the heat of the metal surface is reduced. It can follow expansion and thermal contraction.

The present invention will be described in detail below. The heat-resistant process sheet for metalworking in the present invention has a base material containing glass fibers and fibrillated fibers with a flat cross section, and a surface layer containing a clay mineral, and is represented by the following formulas (1) and (2). is characterized by satisfying

25≦surface layer content≦80 (1)
(In formula (1), the surface layer content [% by mass] is the coating amount of the surface layer [g/m ² ]/the basis weight of the base material [g/m ² ]×100. )

0.5≦A/B (2)
(In formula (2), A [μm] is the thickness of the heat-resistant process sheet−the thickness of the base material, and B [g/m ² ] is the coating amount of the surface layer.)

In the present invention, examples of glass fibers include chopped strands, glass wool, and glass flakes. Any glass fiber may be used as long as it is hard to break and has the ability to form a base material.

In the present invention, the substrate contains flat cross-section glass fibers. In the flat cross-section glass fiber, the dimensions of the major axis and the minor axis of the flat cross section are not particularly limited. The ratio of the major axis to the minor axis" is referred to as the "flatness ratio") is preferably 3-5. If the flatness ratio is less than 3, the effect of improving the strength may be reduced. On the other hand, if the flatness ratio exceeds 5, spinning of flat glass fibers may become difficult, or the number of fibers may decrease in papermaking. Therefore, the texture of the base material may deteriorate, the heat-resistant process sheet may become too thin, and pinholes may easily occur.

The converted fiber diameter of the glass fiber having a flat cross section is preferably 5 to 17 μm, more preferably 6 to 14 μm, even more preferably 7 to 11 μm. Also, the short diameter is preferably 2.8 to 9.6 μm, more preferably 3.5 to 7.0 μm, even more preferably 4.0 to 6.0 μm. The term "converted fiber diameter" means the value of the diameter of a circular cross-section fiber having the same cross-sectional area as that of a flattened fiber. When the converted fiber diameter is less than 5 μm, economical spinning becomes difficult, while when the converted fiber diameter exceeds 17 μm, the fibers become too thick and have high rigidity, making dispersion in the papermaking process difficult. There is In addition, since the number of glass fibers is reduced, voids are increased, and the coatability and adhesion amount of the surface layer may be reduced.

In the present invention, the substrate may contain glass fibers with a circular cross section in addition to the glass fibers with a flat cross section. The fiber diameter of the glass fiber having a circular cross section is preferably 1 to 11 μm, more preferably 2 to 8 μm, even more preferably 3 to 7 μm. If the fiber diameter is less than 1 μm, the glass fibers may be too fine to fall off from the base material during papermaking, resulting in insufficient strength and thickness of the base material. If the fiber diameter exceeds 11 μm, the glass fiber becomes too thick, and the gap between the substrates becomes large. be. When the fiber diameter of the glass fiber is 1 to 11 μm, the gaps between the substrates are fine and uniform, so that the heat-resistant process sheet is less likely to fall off after the formation of the surface layer and has excellent flexibility.

The fiber length of the glass fiber is preferably 1 to 15 mm, more preferably 3 to 13 mm, even more preferably 5 to 10 mm. If the fiber length is less than 1 mm, the strength of the base material may be insufficient, and if the fiber length exceeds 15 mm, the texture of the base material may deteriorate, or clumps or kinks entangled with glass fibers may occur. It may become easier or less flexible.

The glass fiber content is preferably 78 to 94% by mass, more preferably 80 to 92% by mass, and more preferably 82 to 90% by mass with respect to the total raw material constituting the base material. More preferred. If the content is less than 78% by mass, the strength and heat resistance of the base material may deteriorate. In some cases, the coatability of the surface layer deteriorates, and the glass fibers tend to fall off at high temperatures.

The content of glass fibers with a flat cross section is preferably 75% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and further 85% by mass or more and 100% by mass or less. preferable. When the content is within this range, the tensile strength of the base material when dry and wet is high, and the coatability of the surface layer is excellent. In addition, the flexibility of the heat-resistant process sheet is excellent, the folding endurance strength is increased, and corner cracking during use can be prevented. If the content is less than 75% by mass, the glass fibers may easily fall off from the substrate.

The fibrillated fiber in the present invention includes natural cellulose, solvent-spun cellulose, acrylic, wholly aromatic polyamide, wholly aromatic polyester, polyimide, polyamideimide, polyetheretherketone, polyethersulfone, polyphenylene sulfide, polybenzimidazole, poly -Fibrillated fibers made of heat-resistant resins such as p-phenylenebenzobisthiazole, poly-p-phenylenebenzobisoxazole, and polytetrafluoroethylene. Among these, wholly aromatic polyamides, which have high heat resistance, high hydrophilicity, and are easily fibrillated, are preferred. More preferably, pulp-like materials made of meta-aromatic polyamides such as poly(m-phenylene isophthalamide) and poly(m-phenylene terephthalamide) resins are preferred. A pulp-like material composed of a meta-aromatic polyamide is a thin leaf-like or scale-like small piece having a large number of minute fibril parts capable of making a paper-like structure using a paper machine. It has the effect of filling voids and smoothing the sheet. In addition, when the moisture present in the crystal structure is removed by heating, pressure reduction, or the like, it shrinks significantly and strengthens the fiber network, so it has the effect of improving the wet strength of the base material.

The modified freeness of the fibrillated fiber in the present invention is preferably 0 to 300 ml, more preferably 0 to 200 ml, still more preferably 0 to 100 ml. When the modified freeness exceeds 300 ml, the fiber width of the trunk portion of the fibrillated fiber is thick and fibrillation is not so advanced, so the dense network with the glass fiber is reduced, resulting in a decrease in tensile strength. Sometimes. On the other hand, when the modified freeness is less than 0 ml, the fine content of the fibrillated fibers increases, and the percentage of the fibrillated fibers falling off from the substrate increases, which may lower the yield. In addition, fibrillation of fibers takes a long time and is very expensive. As fibrillation of fibrillated fibers progresses, the modified freeness continues to decrease. Even after the modified freeness reaches 0 ml, if the fibers are further fibrillated, the fibers will pass through the mesh and the modified freeness will start to rise. In the present invention, the state in which the modified freeness starts to reversely rise is called "the modified freeness is less than 0 ml".

In the present invention, the modified freeness is JIS P8121-2: 2012 except that an 80-mesh wire mesh with a wire diameter of 0.14 mm and an opening of 0.18 mm is used as the sieve plate, and the sample concentration is set to 0.1%. It is a value measured according to

The fibrillated fiber of the present invention preferably has a mass-weighted average fiber length of 0.02 mm or more and 1.50 mm or less. Also, the length-weighted average fiber length is preferably 0.02 mm or more and 1.00 mm or less. If the average fiber length is shorter than the preferred range, the fibrillated fibers may fall off from the substrate. If the average fiber length is longer than the preferred range, the fibers are not easily disaggregated, and poor dispersion tends to occur.

When the fibrillated fibers have the above mass-weighted average fiber length and length-weighted average fiber length, even if the content of fibrillated fibers contained in the base material is small, the fibrillated fibers and the glass fibers In between, a dense network structure is formed by the fibers, making it easier to obtain a substrate that has high tensile strength and can improve the permeability and liquid retention of the coating liquid for forming the surface layer.

The average fiber width of the fibrillated fibers is preferably 0.5 μm or more and 40.0 μm or less, more preferably 3.0 μm or more and 35.0 μm or less, and even more preferably 5.0 μm or more and 30.0 μm or less. If the average fiber width exceeds 40.0 μm, the entanglement between the fibrillated fibers and the glass fibers is reduced, which may reduce the tensile strength. Tensile strength may decrease unless binder fibers are increased due to excessive fiber shedding and cross points.

In the present invention, the mass-weighted average fiber length, length-weighted average fiber length and average fiber width of the fibrillated fibers are defined in "JIS P 8226-2: 2011, Pulp-Method for measuring fiber length by automatic optical analysis Part 2: Non-Polarization Method”, OpTest Equipment Inc. It is a value measured using a Fiber Quality Analyzer (FQA-360) manufactured by Co., Ltd.

Fibrillated fibers are produced by using a refiner, a beater, a mill, a grinder, a rotary homogenizer that applies a shearing force with high-speed rotating blades, a cylinder with an inner blade that rotates at high speed, and a fixed outer blade. A double-cylinder high-speed homogenizer that generates shear force between blades, an ultrasonic crusher that miniaturizes with ultrasonic impact, and a small-diameter orifice by applying a pressure difference of at least 20 MPa to a heat-resistant resin suspension. A high-pressure homogenizer that applies a shearing force and a cutting force to the resin by passing it through at high speed and colliding it to rapidly decelerate it, a ring-shaped blade (rotor) with fine slits that rotates at high speed, and a fixed fine It can be obtained by processing using a disintegrator or the like arranged so as to mesh with a ring-shaped blade (stator) having a slit.

In the present invention, the content of the fibrillated fibers is preferably 3% by mass or more and 12% by mass or less, more preferably 4% by mass or more and 11% by mass or less, based on the total raw materials constituting the base material. It is preferably 5% by mass or more and 10% by mass or less. If the fibrillated fiber content exceeds 12% by mass, the glass fibers tend to come off at high temperatures. On the other hand, if the fibrillated fiber content is less than 3% by mass, the entanglement between the fibrillated fibers and between the fibrillated fibers and the glass fibers is reduced, resulting in a decrease in tensile strength.

The base material of the heat-resistant process sheet of the present invention preferably contains binder fibers. As the binder fiber, a wet heat adhesive binder fiber or a heat adhesive binder fiber can be used. A wet heat adhesive binder fiber is a fiber that exhibits an adhesive function by flowing or easily deforming from a fibrous state at a certain temperature in a wet state. Specifically, it is a thermoplastic fiber that can be softened by hot water or steam (for example, about 80 to 120 ° C.) and self-adhesive or can be adhered to other fibers. , polyvinyl alcohol, polyvinyl acetal, etc.), cellulosic fibers (C1-3 alkyl cellulose such as methyl cellulose, hydroxy C1-3 alkyl cellulose such as hydroxymethyl cellulose, carboxy C1-3 alkyl cellulose such as carboxymethyl cellulose, or salts thereof), Fibers made of modified vinyl-based copolymers (vinyl-based monomers such as isobutylene, styrene, ethylene, vinyl ether, and unsaturated carboxylic acids such as maleic anhydride, or copolymers with their anhydrides, or salts thereof etc.). As the wet heat adhesive binder fiber used in the present invention, polyvinyl-based fiber is preferable, and polyvinyl alcohol (PVA) fiber is more preferable. When polyvinyl alcohol fibers are used, it is easy to form a film between the fibers, and the strength of the substrate is increased.

As the wet heat adhesive binder fiber, a modified polyvinyl alcohol fiber modified with a compound having a cross-linking functional group, and a cross-linked polyvinyl alcohol fiber cross-linked under mild conditions during or after spinning using a cross-linking agent are used. It is possible to impart hot water resistance to the drawn yarn, which is more preferable.

Examples of crosslinkable functional groups include silanol groups, carboxyl groups, and methylol groups. By adjusting the pH or the like, the polyvinyl alcohol modified with a compound having a crosslinkable functional group can be dissolved in water without cross-linking and spun to obtain a modified polyvinyl alcohol fiber. The modified polyvinyl alcohol fibers may be crosslinked during or after spinning. The degree of modification is preferably 0.01 to 10 mol%, more preferably 0.1 to 5 mol%. As a preferred example, silanol-modified polyvinyl alcohol (denaturation degree 0.1 to 2 mol%) is dissolved in an alkaline solution (pH 9 to 13), and the solution is acidified (pH 5 to 6) to crosslink while spinning. and silanol-modified polyvinyl alcohol fibers obtained by heat treatment after drying.

Also, crosslinked polyvinyl alcohol fibers obtained by a method of spinning non-self-crosslinking unmodified polyvinyl alcohol and then imparting various organic or inorganic crosslinking agents to crosslink the fibers can also be used. Examples of inorganic cross-linking agents include phosphoric acid, ammonium phosphate, ammonium sulfate, and titanyl sulfate. Examples of organic cross-linking agents include methylol-based, epoxy-based, isocyanate-based, and aldehyde-based cross-linking agents. After adding these cross-linking agents to the undenatured polyvinyl alcohol spinning dope and spinning, or after spinning the undenatured polyvinyl alcohol alone and passing it through a cross-linking agent-containing bath, heat treatment can be performed to promote cross-linking. can. Moreover, it is also possible to use these methods together.

Although the wet heat adhesive binder fiber used in the present invention is not limited to the above, the silanol-modified polyvinyl alcohol fiber further increases the adhesiveness to the glass fiber, so that the tensile strength of the substrate can be further increased. , is particularly preferred.

A heat-fusible binder fiber is a fiber that exhibits a bonding function by being heat-fusible during drying in papermaking. Examples of heat-fusible binder fibers include core-sheath type, eccentric type, side-by-side type, islands-in-the-sea type, orange type, multi-bimetal type composite fibers, single fibers, and the like. It preferably contains binder fibers. The core-sheath type heat-fusible binder fiber is suitable for bonding fibers by softening and melting only the sheath portion while maintaining the fiber shape of the core portion. There are no particular limitations on the resin component that constitutes the core and sheath of the core-sheath type heat-fusible fiber, and any resin having fiber-forming ability may be used. Specific examples of heat-fusible binder fibers include polypropylene monofilament, polyethylene monofilament, low-melting-point polyester monofilament, composite fibers of a combination of polypropylene (core) and polyethylene (sheath), and polypropylene (core) and ethylene. Composite fibers of a combination of vinyl alcohol (sheath), composite fibers of a combination of high-melting polyester (core) and low-melting polyester (sheath), and the like.

The fineness of the binder fibers is preferably 0.1 to 5.6 decitex, more preferably 0.4 to 2.2 decitex, and even more preferably 0.6 to 1.1 decitex. If the fineness is less than 0.1 decitex, the fiber itself becomes very expensive, and the substrate may become too dense and thin. On the other hand, if it exceeds 5.6 decitex, the contact points with the glass fibers are reduced, and it may become difficult to maintain the strength in a wet state. In addition, a uniform formation may not be obtained. The fiber length of the binder fibers is preferably 1 to 15 mm, more preferably 2 to 10 mm, even more preferably 3 to 5 mm. If the fiber length is less than 1 mm, the binder fibers may fall off from the papermaking wires during papermaking, and a heat-resistant process sheet having sufficient strength may not be obtained. On the other hand, if the thickness exceeds 15 mm, the binder fibers may become entangled when dispersed in water, and the texture of the heat-resistant process sheet may become uneven.

In the present invention, each binder fiber may be used alone, or may be used in combination. The binder fiber content is preferably 3 to 10% by mass, more preferably 4 to 9% by mass, and more preferably 5 to 8% by mass, based on the total raw material constituting the base material. More preferred. If the binder fiber content is less than 3% by mass, the strength of the base material is lowered, and the paper may be broken when the surface layer is coated, or the glass fibers may fall off. On the other hand, if the binder fiber content exceeds 10% by mass, the peelability from the drier may deteriorate when the substrate is made into paper by a wet papermaking method.

In the present invention, in addition to the glass fiber, the fibrillated fiber, and the binder fiber described above, various fibers can be blended, if necessary, as long as the performance is not impaired. As a result, finer voids can be increased, and the retention of clay minerals and the strength of the heat-resistant process sheet can be improved. Such fibers include regenerated fibers such as rayon, cupra, and lyocell fibers; semi-synthetic fibers such as acetate, triacetate, and promix; polyolefin, polyamide, polyacrylic, vinylon, vinylidene, polyvinyl chloride, and polyester. synthetic resin fibers, metal fibers, carbon fibers, alumina, silica, ceramics, rock fibers Inorganic fibers such as can be added.

The synthetic resin fiber may be a fiber (single fiber) made of a single resin, or a composite fiber made of two or more resins. Composite fibers include core-sheath type, eccentric type, side-by-side type, sea-island type, orange type, and multi-bimetal type. Further, the above various fibers may be used singly or in combination of two or more.

In the present invention, the thickness of the substrate is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. Also, it is preferably 1.0 mm or less, more preferably 0.8 mm or less, and even more preferably 0.6 mm or less. When the thickness of the substrate is within the above range, the substrate in the present invention can easily maintain the necessary tensile strength in the papermaking process and the coating process. Good workability. If the thickness of the base material exceeds 1.0 mm, the flexibility of the heat-resistant process sheet may be impaired, making it difficult to handle. If the thickness of the base material is less than 0.1 mm, the strength required for the heat-resistant process sheet cannot be obtained, and cracks or breaks may occur when used at high temperatures.

The density of the substrate in the invention is preferably 0.10 g/cm ³ or more, more preferably 0.20 g/cm ³ or more. Also, it is preferably 0.50 g/cm ³ or less, more preferably 0.40 g/cm ³ or less. If the density ^is less than 0.10 g/cm ³ , the tensile strength of the substrate becomes too weak, and the substrate may be damaged during handling or coating. In some cases, the flexibility of the base material deteriorates, making it difficult to take up the base material with a papermaking reeler.

In the present invention, the basis weight of the substrate is preferably 30 g/m ² or more, more preferably 50 g/m ² or more. Also, it is preferably 150 g/m ² or less, more preferably 100 g/m ² or less. If the basis weight ^of the base material is less than 30 g/m ² , the tensile strength of the base material becomes too weak, and the base material may be damaged during handling or coating. In some cases, the flexibility of the base material deteriorates, making it difficult to take up the base material with a papermaking reeler.

The substrate in the present invention is preferably a wet-laid nonwoven fabric produced by a wet-laid papermaking method (paper-making method). In the wet papermaking method, fibers are dispersed in water to form a uniform papermaking slurry, and the papermaking slurry is made by a paper machine to produce a wet nonwoven fabric. The paper machine includes a cylinder paper machine, a fourdrinier paper machine, an inclined paper machine, an inclined wire mesh paper machine, and a combination of these machines. It can also be manufactured on a paper machine having multiple headboxes and overlapping wet paper webs on wires. In addition to the fiber raw material, the papermaking slurry may optionally contain a dispersant, a paper strength agent, a thickener, an inorganic filler, an organic filler, an antifoaming agent, and the like. The solid content concentration of the papermaking slurry is preferably about 0.5 to 0.001% by mass. This papermaking slurry is further diluted to a predetermined concentration and then made into paper to obtain a wet paper web. The wet paper web thus made into paper is then nipped by a press roll or the like, and then a Yankee dryer is used to melt the binder fibers to develop strength. By drying with a Yankee dryer, the dried surface becomes flat and a surface with less unevenness can be formed. In addition, there is no problem even if a heating device such as a hot air dryer, a heating roll, or an infrared heater is used for auxiliary drying. The drying temperature at this time is preferably a temperature at which the water content of the wet paper web can be sufficiently removed and strength can be exhibited by the binder fibers.

In the present invention, the heat-resistant process sheet contains a clay mineral in the surface layer. By covering the base material surface with this surface layer, it is possible to prevent the fibers from falling off from the heat-resistant process sheet at high temperatures and prevent the metal surface from being scratched.

In the present invention, the clay minerals belong to clay minerals according to mineralogical classification, and include layered clay minerals such as kaolin, serpentine, halloysite, pyrophyllite, talc, mica, smectite, bentonite, chlorite, and sepiolite. , fibrous clay minerals such as palygorskite, and amorphous clay minerals such as allophane and imogolite. Among them, layered clay minerals or fibrous clay minerals are preferred, and kaolin, bentonite, and sepiolite are particularly preferred from the viewpoint of suppressing fiber dropout from the heat-resistant process sheet at high temperatures. The above clay minerals may be used alone or in combination of two or more.

In the present invention, the particle size of the clay mineral is preferably 0.08 μm or more and 20.0 μm or less, more preferably 0.30 μm or more and 15.0 μm or less, and 0.40 μm or more and 10.0 μm or less. is more preferred. If the particle size exceeds 20.0 μm, high-temperature metal products may be scratched when used as a heat-resistant process sheet, or powder falling off may be aggravated. On the other hand, if the particle size is less than 0.08 μm, the viscosity of the coating liquid becomes high, which may make coating difficult, or cracks may occur when the resulting heat-resistant process sheet is used at high temperatures. The particle size of the clay mineral was obtained by diluting the clay mineral with water, dispersing it with a stirrer, and measuring it with a laser scattering type particle size analyzer (manufactured by Microtrack, trade name: MT3000). The median diameter (D50, volume basis) was taken as the particle diameter.

The medium for preparing the surface layer forming coating liquid is not particularly limited as long as it can uniformly dissolve or disperse the clay mineral. For example, aromatic hydrocarbons such as toluene, ethers such as tetrahydrofuran, ketones such as methyl ethyl ketone, alcohols such as isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), dimethylacetamide, dimethylformamide, dimethylsulfoxide, Water or the like can be used as necessary. Moreover, the medium to be used is preferably a medium that does not expand the substrate or a medium that does not dissolve the substrate.

The surface layer content is a value calculated by "coating amount of surface layer (g/m ² )/basis weight of base material (g/m ² ) × 100", and is 25% by mass or more and 30% by mass. % by mass or more is more preferable, and 40% by mass or more is even more preferable. If the content of the surface layer is less than 25% by mass, the fibers tend to come off from the substrate significantly when the heat-resistant process sheet is treated at high temperatures. Also, the surface layer content is 80% by mass or less, preferably 70% by mass or less, and even more preferably 60% by mass or less. The higher the content of the surface layer, the higher the heat resistance. However, when the content exceeds 80% by mass, powder falls off and the metal product is damaged when used as a heat-resistant process sheet.

In the present invention, when A/B is 0.5 or more, the content of the clay mineral in the outermost surface of the heat-resistant process sheet is higher than the content in the central portion of the substrate, so that the central portion does not become too hard. It can follow the thermal expansion and thermal contraction of metal. If it is less than 0.5, the content of the clay mineral in the outermost surface of the heat-resistant process sheet becomes higher in the center of the substrate than in the outermost surface, and the center of the heat-resistant process sheet becomes too hard, resulting in thermal expansion and expansion of the metal. The sheet cannot follow the heat shrinkage, and the sheet cracks, and when used as a metal heat-resistant process sheet, the metal product is damaged.

Various coating apparatuses can be used as the apparatus for applying the surface layer forming coating liquid to the base material. For example, 2-roll size press, gate roll coater, gravure coater, die coater, lip coater, blade coater, curtain coater, air knife coater, rod coater, kiss touch coater, dip coater, impregnation such as comma coater (registered trademark), Alternatively, various coaters using a coating device can be used, but the present invention is not limited to this.

In the present invention, the surface layer includes, in addition to the above clay minerals, a binder resin such as polyvinyl alcohol, various dispersants such as polyacrylic acid and sodium carboxymethylcellulose, hydroxyethyl cellulose to increase the liquid stability of the coating liquid, Various additives such as various thickeners such as sodium carboxymethylcellulose and polyethylene oxide, various water retention agents, various wetting agents, preservatives and antifoaming agents may be added as necessary. In general, a non-aqueous coating liquid using an organic solvent as a medium has a low surface tension, and an aqueous coating liquid using water as a medium has a high surface tension. Since the base material of the present invention has high receptivity for coating liquids, both non-aqueous coating liquids and water-based coating liquids can be applied without problems. It is preferable to use the water-based coating liquid used.

In the present invention, the thickness of the heat-resistant process sheet is preferably 0.11 mm or more, more preferably 0.16 mm or more, and even more preferably 0.21 mm or more. Also, it is preferably 1.1 mm or less, more preferably 0.9 mm or less, and even more preferably 0.7 mm or less. If the thickness of the heat-resistant process sheet exceeds 1.1 mm, the flexibility may be impaired and handling may become difficult. If the thickness of the heat-resistant process sheet is less than 0.11 mm, the necessary strength cannot be obtained, and cracks and breaks may occur when used at high temperatures.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. All percentages (%) and parts in the examples are based on mass unless otherwise specified. Moreover, the amount of coating is the amount of absolutely dry coating.

<Production of fibrillated fiber 1>
A homomixer in which 10 parts of poly(m-phenylene isophthalamide) having a logarithmic viscosity of 1.5 in sulfuric acid is dissolved in 90 parts of N,N-dimethylacetamide containing 15 parts of lithium chloride, and this solution is stirred at high speed. A pulp-like material is obtained by introducing it into an aqueous glycerin solution in the medium, passing this pulp-like material through a single disc refiner, fibrillating it to adjust the modified freeness, 65 ml of freeness) was obtained.

<Production of fibrillated fiber 2>
Solvent-spun cellulose fibers having an average fiber diameter of 12 μm and a fiber length of 5 mm were refined with a refiner to obtain fibrillated cellulose (modified freeness of 100 ml).

<Preparation of base material 1>
85 parts of flat glass fiber (manufactured by Nitto Boseki Co., Ltd., major diameter 28 μm, minor diameter 7 μm, fiber length 13 mm, flat cross section), 8 parts of silanol-modified PVA fiber (wet heat adhesive binder fiber, trade name: SPG056-11, stock 7 parts of fibrillated fiber 1 (made by Kuraray Co., Ltd., fineness 0.6 decitex, fiber length 3 mm) was dispersed in water using a pulper to prepare a uniform papermaking slurry with a concentration of 0.5%. A wet paper web was obtained using a mesh paper machine and dried with a Yankee dryer having a surface temperature of 120° C. to produce a substrate having a basis weight of 75 g/m ² and a thickness of 210 μm.

<Preparation of base material 2>
In the fiber formulation, 66 parts of the flat glass fiber used in the base material 1, 22 parts of the glass fiber (manufactured by Nitto Boseki Co., Ltd., fiber diameter 6.5 μm, fiber length 6 mm, circular cross section), silanol used in base material 1 A base material having a basis weight of 75 g/m ² and a thickness of 225 μm was prepared in the same manner as base material 1 except that 5 parts of modified PVA fiber and 7 parts of fibrillated fiber 1 used in base material 1 were used.

<Preparation of base material 3>
In the fiber formulation, the same method as for base material 1 was used except that 84 parts of the flat glass fiber used in base material 1, 8 parts of the silanol-modified PVA fiber used in base material 1, and 8 parts of fibrillated fiber 2 were used. , a basis weight of 75 g/m ² and a thickness of 210 μm.

<Preparation of base material 4>
In the fiber formulation, the same method as in Base material 1 was used except that 90 parts of the flat glass fiber used in Base material 1 and 10 parts of the silanol-modified PVA fiber used in Base material 1 were used, and the basis weight was 75 g / m ² and the thickness was A 210 μm substrate was produced.

<Preparation of base material 5>
In the fiber formulation, except that 85 parts of the glass fiber (circular cross section) used in the base material 2, 8 parts of the silanol-modified PVA fiber used in the base material 1, and 7 parts of the fibrillated fiber 1 used in the base material 1 were used. , a substrate having a basis weight of 75 g/m ² and a thickness of 240 μm was produced in the same manner as the substrate 1 .

<Preparation of Surface Layer Forming Coating Liquid 1>
Kaolin (trade name: ASP (registered trademark) NC X-1, manufactured by BASF CORPORATION) 100 parts, water-soluble acrylic dispersant (trade name: Aron (registered trademark) T-50, manufactured by Toagosei Co., Ltd.) 0 A kaolin dispersion was prepared by mixing .4 parts in water and stirring thoroughly. Next, 20 parts of sepiolite (trade name: Milcon (registered trademark) SP-2, manufactured by Showa KDE Co., Ltd.) and 1.0 part of a water-soluble acrylic dispersant (Aron T-50) were mixed in water and thoroughly stirred. , a sepiolite dispersion was prepared. Then, the total amount of the kaolin dispersion, the total amount of the sepiolite dispersion, and 0.08 parts of a water retention agent (trade name: SN Thickener 926, manufactured by San Nopco) were mixed and stirred, and the concentration was adjusted with water to prepare a coating liquid.

<Preparation of Surface Layer Forming Coating Liquid 2>
A coating liquid was prepared in the same manner as for coating liquid 1, except that 0.08 part of a water retention agent (trade name: SN Thickener 926, manufactured by San Nopco) was not used.

<Production of heat-resistant process sheet>
The surface layer-forming coating solution was applied onto the base material described above under the conditions shown in Table 1 to prepare heat-resistant process sheets for metalworking of Examples 1 to 6 and Comparative Examples 1 to 6.

The following physical properties were measured and evaluated for the substrates and heat-resistant process sheets of Examples and Comparative Examples, and the results are shown in Table 1.

<Basis weight of base material and heat-resistant process sheet for metal processing>
The basis weight of the base material and the total basis weight of the heat-resistant process sheet were measured according to JIS P8124:2011. The coating weight of the surface layer was calculated by subtracting the basis weight of the substrate from the basis weight of the heat-resistant process sheet.

<Thickness of base material and heat resistant process sheet for metal processing>
The thickness was measured using an outer micrometer specified in JIS B7502:2016.

<Detachment of fibers or clay minerals>
Cut out three sheets of each heat-resistant process sheet with a size of 100 mm × 100 mm, sandwich them between aluminum plates of 100 mm × 100 mm with a thickness of 0.3 mm, place an iron piece with a mass of 4 kg on it, put it in an electric furnace, and raise the temperature from room temperature. After the temperature reached 550° C., the plate was heated for 8 hours, cooled to 100° C. or less, and taken out.

◯: Almost no detachment of fibers and clay minerals is observed.
Δ: Detachment of fibers or clay minerals is partially observed.
x: Detachment of fibers or clay minerals is observed on the entire surface.

<Sheet Crack>
Cut out three sheets of each heat-resistant process sheet with a size of 100 mm × 100 mm, sandwich them between aluminum plates of 100 mm × 100 mm with a thickness of 0.3 mm, place an iron piece with a mass of 4 kg on it, put it in an electric furnace, and raise the temperature from room temperature. After reaching 550° C., heat treatment was carried out for 8 hours, and then cooled to 100° C. or less.

◯: No cracks in the sheet.
Δ: Some cracks are observed in the sheet.
x: The sheet is cracked.

<Scratches on metal surface>
Cut out three sheets of each heat-resistant process sheet with a size of 100 mm × 100 mm, sandwich them between aluminum plates of 100 mm × 100 mm with a thickness of 0.3 mm, place an iron piece with a mass of 4 kg on it, put it in an electric furnace, and raise the temperature from room temperature. Heat treatment is performed for 8 hours after reaching 550°C, then cooled to 100°C or less, taken out, and visually observed for scratches on the surface of the aluminum plate in contact with the heat-resistant process sheet. evaluated.

◯: No scratches were observed on the surface of the aluminum plate.
Δ: Slight dent marks are observed on the surface of the aluminum plate.
x: Scratches are observed on the surface of the aluminum plate.

From the results in Table 1, it can be seen that the heat-resistant process sheet for metalworking of the present invention has flexibility, excellent strength at high temperatures, the clay minerals and fibers are less likely to fall off, and the metal surface is prevented from being scratched.

The heat-resistant process sheets of Examples 1 to 6, which have a base material containing flat cross-section glass fibers and fibrillated fibers, and a surface layer containing a clay mineral and satisfy formulas (1) and (2), , There was little dropout of fibers or clay minerals, and the sheet had flexibility that could follow the thermal expansion and contraction of the metal, so there were no cracks in the sheet and no scratches on the metal surface.

In the heat-resistant process sheet of Comparative Example 1, in which the content of the surface layer was 100%, the clay mineral fell off and the metal surface was damaged.

In the heat-resistant process sheet of Comparative Example 2 having a surface layer content of 20%, the fibers fell off and the metal surface was damaged.

The heat-resistant process sheet of Comparative Example 3, in which A/B is less than 0.5, is too hard up to the center of the heat-resistant process sheet, and cannot cope with the thermal expansion and thermal contraction of the metal, resulting in cracking of the sheet and scratches on the metal surface. It was observed.

The heat-resistant process sheet of Comparative Example 4, in which the base material did not contain fibrillated fibers, was weak in strength, fibers were observed to fall off, the sheet was broken, and the metal surface was scratched.

The heat-resistant process sheet of Comparative Example 5, in which the base material did not contain glass fibers having a flat cross section, was weak in strength, and fiber dropout was observed, the sheet was broken, and scratches were observed on the metal surface.

In the heat-resistant process sheet of Comparative Example 6, which did not contain a surface layer, many fibers fell off and faint scratches were observed on the metal surface.

Claims (1)

A heat resistant material for metalworking, which has a base material containing glass fibers and fibrillated fibers with a flat cross section, and a surface layer containing a clay mineral, and which satisfies the following formulas (1) and (2): process sheet.
25≦surface layer content≦80 (1)
(In formula (1), the surface layer content [% by mass] is the coating amount of the surface layer [g/m ² ]/the basis weight of the base material [g/m ² ]×100. )
0.5≦A/B (2)
(In formula (2), A [μm] is the thickness of the heat-resistant process sheet minus the thickness of the substrate, and B [g/m ² ] is the coating amount of the surface layer.)