Substrate-free abrasive material and manufacturing method therefor

Abstract

The present invention provides a substrate-free abrasive material or the like that adopts a configuration in which no substrate is provided, and flexibly deforms so as to follow a surface to be polished of an object to be polished even when the surface to be polished has, in particular, a curved shape or the like, thereby achieving good polishing characteristics.　In a substrate-free abrasive material 1 according to the present invention, no substrate is provided, and a plurality of abrasive grains 2 are held in a dispersed state in a base part 3 containing a total of 60 vol% or more of a base component of at least one of a resin and an elastomer. The substrate-free abrasive material 1 has a type-A durometer hardness of 50-80, a tensile strength of 70-250 MPa, and a tensile elongation of 10-360%, these values being measured in conformity with a hardness test defined in JIS K7311-1995.

Description

Substrate-less abrasive and its manufacturing method

[0001] The present invention relates to a substrate-less abrasive and a method for producing the same.

[0002] As shown in Figure 7, a conventional abrasive 100 is composed of a substrate 104 made of a sheet-like material such as paper, cloth, film, or nonwoven fabric, and a plurality of abrasive grains (abrasive particles) 102 that are dispersed on the surface of the substrate 104 and adhered and fixed with adhesive 103.

[0003] The reason why abrasives usually require a substrate is to fix the abrasive grains. By fixing the abrasive grains to the substrate, they maintain their shape (posture), making them easier to handle and allowing for faster polishing than with loose abrasive grains.

[0004] However, when a hard substrate is used for the abrasive 100 having the substrate 104, there are problems such as the abrasive not conforming to the surface irregularities of the workpiece being polished, resulting in excessive abrasion or inadvertent scratches, and when a soft substrate is used, the abrasive is prone to wrinkles during manufacturing and polishing, making it difficult to achieve uniform polishing and tending to result in a high defect rate.

[0005] In particular, in the manufacture of automobiles, there is a process of polishing the paint film formed on the outer surface (surface to be polished) of the exterior panel of the automobile body, but the automobile body is not flat but is formed into a curved surface called an R surface or a reverse R surface.

[0006] When polishing such a curved surface using an abrasive material 100 having a substrate 104, workers try to suppress uneven polishing by using a urethane foam cushioning material between the abrasive material and the support (called a sander or file), or by using a flexible substrate such as a sponge pad, as in the polishing sheet described in Patent Document 1, but the current situation is that sufficient polishing performance is not achieved.

[0007] Furthermore, such conventional abrasive material 100 has a laminated structure in which an abrasive layer 105 composed of abrasive grains and adhesive 103 is adhesively fixed to the surface of a substrate 104, and since an adhesive interface exists between the substrate 104 and the abrasive layer 105, there is a risk that the abrasive layer 105 will peel off from the substrate 104 at the adhesive interface during polishing, and if peeling of the abrasive layer 105 occurs, the abrasive material's original polishing properties will not be obtained.

[0008] Furthermore, the thickness ratio of the substrate 104 to the thickness of the abrasive 100 is usually around 30 to 40%, and in the state of a used abrasive that is discarded after abrasive use, the abrasive layer 105 is considerably worn, so the thickness ratio of the substrate to the used abrasive is expected to be even higher, at 50% or more. Therefore, the use of an abrasive 100 in which a film or sheet made of plastic such as PET is used as the substrate 104 is particularly undesirable, as it will result in an increase in the amount of waste.

[0009] For this reason, it is desirable to use a so-called substrate-less abrasive, which does not use a substrate 104, as the abrasive.

[0010] As a conventional substrate-less abrasive, for example, Patent Document 2 describes an abrasive film made of a cured product of a resin composition containing an epoxy resin (A), a curing accelerator (B), and abrasive particles (C).

[0011] However, the polishing film described in Patent Document 2 uses a relatively hard resin, epoxy resin, as the resin constituting the base portion. Therefore, it does not take into account cases where the surface to be polished of the object to be polished has a curved shape, such as an outer panel of an automobile body, or a complex, uneven curved shape known as an R surface or an inverse R surface. Therefore, the polishing film cannot flexibly deform to conform to the curved shape of the surface to be polished during polishing. As a result, with the polishing film described in Patent Document 2, for example, when polishing a painted surface (paint film) formed on the surface of an automobile outer panel having a curved shape, the paint film is partially excessively scraped off, making it impossible to polish uniformly. In addition, when polishing a polishing film using epoxy resin using a roll-to-roll type film manufacturing device (die coater) using a carrier film, the hardness of the polishing film makes it difficult to work with and handle, making it impractical.

[0012] Furthermore, some conventional abrasives have low bending rigidity and use a soft urethane resin as a base material. However, although such abrasives can flexibly deform to conform to the curved shape of the surface of the workpiece, they are too flexible as a whole to maintain their shape, and also have low tensile strength, which means that good abrasive properties cannot be obtained.

[0013] JP 9-123065 A JP 2023-28400 A

[0014] The object of the present invention is to provide a substrate-less abrasive material that employs a configuration that does not have a substrate, and that flexibly deforms to conform to the surface to be polished, even when the surface to be polished is particularly curved or has a complex uneven curved shape, thereby having good polishing properties, and a method for manufacturing the same.

[0015] In order to solve the above problems, the present invention has the following characteristic configurations.

[0016] (1) A substrateless abrasive sheet having no substrate, and comprising a base portion containing a total of 60 volume % or more of a base component of at least one of a resin and an elastomer, with a plurality of abrasive grains dispersed and held in the base portion, the substrateless abrasive having a Type A durometer hardness of 50 to 80, a tensile strength of 70 to 250 MPa, and a tensile elongation of 10 to 360% when measured in accordance with the hardness test specified in JIS K7311-1995. (2) The substrateless abrasive according to (1) above, wherein the base component of the base portion is a urethane resin. (3) The substrateless abrasive according to (1) above, wherein the base portion is composed of two layers, a lower base layer and an upper base layer, the base component of the lower base layer being a urethane resin, and the base component of the upper base layer being a soft epoxy resin. (4) The substrate-less abrasive according to (3) above, wherein the ratio of the thickness of the lower base layer to the thickness of the upper base layer is in the range of 30: 1 to 2: 1. (5) The substrate-less abrasive according to any one of (1) to (4) above, wherein the base portion further contains a filler having properties that increase the tensile strength and decrease the tensile elongation of the substrate-less abrasive. (6) A method for producing a substrate-less abrasive described in any one of (1) to (5) above, comprising the steps of: applying a first adhesive containing at least one base component of a resin and an elastomer to the surface of a support having releasability to form a first adhesive layer; adhering a plurality of abrasive grains in a dispersed state to the first adhesive layer; applying a second adhesive having the same or different composition as the first adhesive to the first adhesive layer to which the plurality of abrasive grains are adhered in a dispersed state to form a second adhesive layer, thereby forming a first composite film on the surface of the support that corresponds to a sheet-like substrate-less abrasive; and peeling the first composite film from the support to obtain the substrate-less abrasive.

[0017] According to the present invention, it is possible to provide a substrate-less abrasive and a method for manufacturing the same, which has a configuration that does not use a substrate and which flexibly deforms to conform to the surface to be polished, even if the surface to be polished is particularly curved or has a complex uneven shape, and has good polishing properties.

[0018] Fig. 1 is a cross-sectional view schematically showing a substrate-less abrasive according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view schematically showing a substrate-less abrasive according to a second embodiment. Fig. 3 is a cross-sectional view schematically showing a substrate-less abrasive according to a third embodiment. Fig. 4 is a cross-sectional view schematically showing a substrate-less abrasive according to a fourth embodiment. Fig. 5 is a cross-sectional view schematically showing a substrate-less abrasive according to a fifth embodiment. Fig. 6 is a view for explaining each step of the method for manufacturing the substrate-less abrasive shown in Fig. 1. Fig. 7 is a cross-sectional view schematically showing a conventional abrasive.

[0019] Next, several embodiments according to the present invention will be described in detail below. (1) First Embodiment The substrate-less abrasive according to the first embodiment is a sheet-like substrate-less abrasive having a base portion that does not have a substrate and contains a plurality of abrasive grains dispersed in a base portion that contains a total of 60 volume % or more of a base component of at least one of a resin and an elastomer, and the substrate-less abrasive has a Type A durometer hardness of 50 to 80, a tensile strength of 70 to 250 MPa, and a tensile elongation of 10 to 360% when measured in accordance with the hardness test specified in JIS K7311-1995.

[0020] <Substrate-less Abrasive> Figure 1 is a schematic diagram of a substrate-less abrasive according to a first embodiment. The substrate-less abrasive 1 shown in the figure does not have a substrate and is mainly composed of a plurality of abrasive grains 2 and a base portion 3. More specifically, it is formed as a composite film in which at least some of the abrasive grains 2 are embedded in the base portion 3, the main component of which is at least one of a resin and an elastomer (containing a total of 60% by volume or more). Note that the term "composite film" used here refers to a sheet or film that does not have a supporting material (substrate).

[0021] <Abrasive grains> As shown in FIG. 1, a plurality of abrasive grains 2 are dispersed and held in a base portion 3. The abrasive grains 2 function as abrasives when some of them are exposed on the film surface. The abrasive grains 2 can be made of alumina (Al ２ O ３), silicon carbide (SiC), cubic boron nitride (cBN), diamond, emery, silica (SiO ２ ), zirconia (ZrO ２ ), glass, and other inorganic materials can be used, but there is no particular limitation.

[0022] The average particle size of the abrasive grains 2 is preferably, for example, in the range of 0.1 to 125 μm, and more preferably in the range of 3 to 100 μm. If the average particle size is larger than 125 μm, the abrasive grains will be hard and rough, and sufficient abrasiveness may not be ensured without a substrate. Also, abrasive grains smaller than 0.1 μm may be difficult to handle when manufacturing the abrasive. The particle size of the abrasive grains can be measured by laser diffraction or the Coulter method (electrical detection zone method).

[0023] The material and particle size of the abrasive grains 2 are appropriately selected depending on the material of the workpiece (object to be polished) and the required finishing precision. In this case, the particle size of the abrasive grains 2 is preferably within the range of -10 to +10% of the selected average particle size, and more preferably within the range of -5 to +5%. Using abrasive grains 2 with a uniform particle size can provide uniform polishing performance.

[0024] The content of the abrasive grains 2 in the abrasive material 1 is preferably in the range of 1 to 70% by volume, and more preferably in the range of 10 to 50% by volume. The content of the abrasive grains 2 is adjusted to an appropriate amount depending on the average particle size and thickness of the abrasive material.

[0025] <Base Portion> The base portion 3 is a sheet-like member containing a total of 60% by volume or more of a base component of at least one of a resin and an elastomer, and holding a plurality of abrasive grains 2 in a dispersed state.

[0026] [Base Component] The base component is at least one of a resin and an elastomer.

[0027] Examples of resins include urethane resins, silicone resins, polyester resins, polyol resins, and epoxy resins (soft resins only), and examples of elastomers include polyurethane and polyester thermoplastic elastomers.

[0028] From the viewpoint of handling during production, the base component is preferably a urethane-based resin, and in particular, a polyester-based urethane resin is more preferred.

[0029] Urethane Resin For the urethane resin used in the present invention, an isocyanate-based crosslinking agent is preferably used.

[0030] [Mechanical Properties of Abrasive] The substrate-less abrasive of this embodiment has mechanical properties of a Type A durometer hardness of 50 to 80, a tensile strength of 70 to 250 MPa, and a tensile elongation of 10 to 360%, when measured in accordance with the hardness test specified in JIS K7311-1995.

[0031] (I) Durometer Hardness The substrate-less abrasive of this embodiment has a Type A durometer hardness of 50 to 80 when measured in accordance with the durometer hardness test method specified in JIS K7215-1986. If the Type A durometer hardness is less than 50, the abrasive is too soft, and good abrasiveness cannot be obtained even when performing abrasive work aimed at smoothing a coating, such as removing bumps or smoothing the surface. On the other hand, if the Type A durometer hardness exceeds 80, the abrasive is too hard and cannot deform to conform to the curved surface being polished. The durometer hardness of the substrate-less abrasive can be measured, for example, by stacking 20 mm x 20 mm test pieces to a thickness of 2.5 mm or more and slowly pressing a durometer (model number: GS-706N (manufactured by Teclock Corporation)) so that the indenter is perpendicular to the measurement surface.

[0032] (II) Tensile Strength: The substrate-less abrasive of this embodiment has a tensile strength of 70 to 250 MPa. If the tensile strength is less than 70 MPa, the force required to secure the abrasive grains during polishing is insufficient, and the (relative) movement of the abrasive grains 2 relative to the base portion 3 constituting the abrasive 1 cannot be suppressed, resulting in poor polishing performance. Furthermore, if the tensile strength exceeds 250 MPa, the flexibility of the abrasive is impaired, making it more susceptible to tearing and breaking. The tensile strength of the substrate-less abrasive can be measured by cutting the prepared substrate-less abrasive into a 25 mm x 150 mm test piece and pulling the test piece in the longitudinal direction using a Tensilon universal testing machine RTG-1225 (manufactured by A&D Corporation) under conditions of a chuck distance of 100 mm and a pulling speed of 200 mm / min, and measuring the maximum point load at this time as the tensile strength (MPa).

[0033] (III) Tensile elongation The substrate-less abrasive of this embodiment has a tensile elongation of 10 to 360%. This is because if the tensile elongation is less than 10%, tearing or breaking is likely to occur. Furthermore, if the tensile elongation exceeds 360%, the force fixing the abrasive grains during polishing is insufficient, the (relative) movement of the abrasive grains relative to the base cannot be suppressed, and good polishing properties cannot be achieved. The tensile elongation of the substrate-less abrasive can be measured by cutting the prepared substrate-less abrasive into a 25 mm x 150 mm test piece and pulling the test piece in the longitudinal direction using a Tensilon universal testing machine RTG-1225 (manufactured by A&D Corporation) under conditions of a chuck distance of 100 mm and a pulling speed of 200 mm / min, and measuring the maximum elongation at this time as the tensile elongation (%).

[0034] (2) Second Embodiment A substrate-less abrasive according to the second embodiment will now be described. FIG. 2 is a schematic diagram of a substrate-less abrasive according to the second embodiment. The illustrated substrate-less abrasive 1A has the same basic structure as the abrasive 1 according to the first embodiment, differing only in that the base portion 3A is composed of two layers: a lower base layer 3a and an upper base layer 3b. The lower base layer 3a and the upper base layer 3b of the base portion 3A may be composed of the same or different compositions. The thickness ratio of the lower base layer 3a to the upper base layer 3b of the base portion 3A is preferably in the range of 30:1 to 2:1. For example, the lower base layer 3a of the base portion 3A may be composed of a urethane-based resin, and the upper base layer 3b may be composed of a resin that firmly fixes the abrasive grains, such as a soft epoxy resin (type A durometer hardness: 70 to 80).

[0035] (3) Third Embodiment A substrate-less abrasive according to the third embodiment will now be described. Figure 3 is a schematic diagram of the substrate-less abrasive according to the third embodiment. The substrate-less abrasive 1B shown in the figure has the same basic configuration as the abrasive 1 according to the first embodiment, except that the base portion 3 further contains a filler 4 that has the properties of increasing the tensile strength and decreasing the tensile elongation of the substrate-less abrasive. The substrate-less abrasive 1B containing the filler 4 has a tensile strength that is 5 to 160 MPa higher and a tensile elongation that is 30 to 90% lower than the substrate-less abrasive 1 that does not contain the filler 4, which is preferable in that it can achieve a better balance between good polishing performance and trackability.

[0036] By further including filler 4 in base portion 3, the flexibility of the base portion can be maintained while suppressing the movement of abrasive grains in base portion 3 during polishing, thereby improving polishing performance.

[0037] The filler 4 may be any material that has the property of increasing the tensile strength without significantly reducing the flexibility of the abrasive 1, more precisely the base portion 3, and suppressing (fixing) the movement of the abrasive grains 2 in the base portion 3 during polishing. There are no particular limitations on the filler 4, but examples include calcium carbonate (CaCO ３), titanium oxide (TiO ２ ), potassium titanate, wollastonite, etc.

[0038] It is preferable that the filler 4 has an average particle size in the range of 0.1 μm to 100 μm, and that the aspect ratio is in the range of 1.0 to 40, which more effectively suppresses the movement of abrasive grains in the base portion 3 during polishing, thereby improving polishing performance.

[0039] The blending ratio of filler 4 in base portion 3 is preferably in the range of 1 to 40 volume %, more preferably in the range of 10 to 25 volume %. If the blending ratio of filler 4 is less than 1 volume %, the effect of suppressing the movement of abrasive grains in base portion 3 during polishing cannot be sufficiently obtained, and it is necessary to adjust the physical properties such as hardness, tensile strength, tensile elongation, etc. of the resin or elastomer base component itself, which is the component other than the filler that makes up the base portion, so that they fall within the range of the present invention. Furthermore, if the blending ratio exceeds 40 volume %, the entire base portion 3 becomes too hard and tends to be unsuitable for polishing curved surfaces.

[0040] (4) Fourth Embodiment A substrate-less abrasive according to the fourth embodiment will now be described. FIG. 4 is a schematic diagram of the substrate-less abrasive according to the fourth embodiment. The illustrated substrate-less abrasive 1C has the same basic structure as the abrasive 1 according to the first embodiment, differing only in that the base portion 3C is composed of two layers, a lower base layer 3c and an upper base layer 3d, and that the lower base layer 3c constituting the base portion 3 further contains a filler 4. In the base portion 3C, the base components 5 of the lower base layer 3c and the upper base layer 3d may be composed of the same composition or different compositions. The thickness ratio of the lower base layer 3a to the upper base layer 3b of the base portion 3C is preferably in the range of 30:1 to 2:1. The base portion 3A may have, for example, a lower base layer 3a made of a urethane-based resin and an upper base layer 3b made of a resin that firmly fixes the abrasive grains, such as a soft epoxy resin (type A durometer hardness: 70 to 80).

[0041] (5) Fifth Embodiment A substrate-less abrasive according to the fifth embodiment will now be described. Fig. 5 is a schematic diagram of the substrate-less abrasive according to the fifth embodiment. The substrate-less abrasive 1D shown in the figure has the same basic structure as the abrasive 1 according to the first embodiment, except that abrasive grains 2D are present in a base portion 3D in a state of being distributed in multiple layers.

[0042] The substrateless abrasive according to the fourth embodiment can be produced, for example, by mixing a plurality of abrasive grains with a solution containing a crosslinking agent and at least one base component of a resin and an elastomer to prepare a mixed liquid, then applying this mixed liquid to the surface of a support (release sheet) having peelability and drying it to form a second composite film that corresponds to the sheet-like substrateless abrasive, which is a coating film, and then peeling the second composite film from the release sheet.

[0043] (6) Other Embodiments The substrate-less abrasive of this embodiment can be coated with an anti-clogging agent or have a loop material attached thereto. In a preferred embodiment, the abrasive of this embodiment can further form a base portion by forming an anti-clogging layer on a layer of a base component made of a highly flexible resin. Here, the term "anti-clogging layer" refers to a layer that has the function of preventing shavings generated during polishing from entering the spaces between the abrasive particles, thereby hindering polishing, a phenomenon known as "clogging." There are no particular restrictions on the material for the anti-clogging layer, as long as it has this function. However, aliphatic metal salts such as calcium stearate and zinc stearate can be used. The anti-clogging layer can be formed on a layer of a base component made of a highly flexible resin by a commonly used method, such as roll coating.

[0044] In another preferred embodiment, the abrasive material of this embodiment can further have a loop material (not shown) formed on the back surface of the base portion 3. This embodiment makes it easy to use the abrasive material of this embodiment by attaching it to a sponge pad or the like. Here, "loop material" refers to a member that is provided to maintain the engaging force of a hook-and-loop fastener or the like. To form the loop material on the back surface of the base portion 3, a commonly used adhesive or pressure-sensitive adhesive can be used.

[0045] <Method of manufacturing substrate-less abrasive>

[0046] Fig. 6 is a flow diagram schematically illustrating an example of a method for manufacturing the substrate-less abrasive of the first embodiment shown in Fig. 1. The method for manufacturing the substrate-less abrasive of the first embodiment includes a first adhesive layer forming step S1, an abrasive grain dispersion and attachment step S2, a first composite film forming step S3, and a support peeling step S4.

[0047] (1) Preparation of Release Sheet (S0) First, a release sheet 10, which is a support having releasability, is prepared ( FIG. 6( a)). The release sheet 10 may be any support that can be releasably supported on its surface, and is not particularly limited. Examples include silicone-based release-treated paper, silicone-based release-treated film, fluorine-based release-treated paper, fluorine-based release-treated film, olefin-based release-treated film, and olefin-based release-treated paper. It is particularly preferable to use a silicone-based release-treated film as the release sheet 10.

[0048] (2) First Adhesive Layer Forming Step (S1) After preparing the release sheet, the first adhesive layer forming step (S1) is performed. The first adhesive layer forming step S1 is a step of applying a first adhesive containing at least one base component of a resin and an elastomer to the surface of the release sheet 10 to form a first adhesive layer 3a' corresponding to the lower base layer constituting the base portion 3 of the substrate-less abrasive 1 (FIG. 6(b)). The first adhesive may be prepared, for example, by blending the base component, crosslinking agent, dilution solvent, and, if necessary, filler in appropriate proportions and stirring and mixing them using a stirrer. The stirrer is not particularly limited, but examples include stirrers such as a disper mixer, an ultra mixer, a homogenizer, and a planetary stirring and defoaming machine.

[0049] (3) Abrasive Grain Dispersion Adhesion Step S2 After the First Adhesive Layer Formation Step (S1), the Abrasive Grain Dispersion Adhesion Step S2 is performed. The Abrasive Grain Dispersion Adhesion Step S2 is a step of adhering a plurality of abrasive grains 2 in a dispersed state to the first adhesive layer 3a' (FIG. 6(c)). The abrasive grains 3 can be adhered to the first adhesive layer 3a' by electrostatic deposition or drop coating. After the abrasive grains are adhered, the first adhesive layer 3a' is solidified (cured) by drying it in a constant temperature oven, for example, to fix the abrasive grains 2 to the lower base layer of the base portion.

[0050] (4) First Composite Film Formation Step S3 After the Abrasive Grain Dispersion and Adhesion Step S2, the First Composite Film Formation Step S3 is performed. In the First Composite Film Formation Step S3, a second adhesive having the same or different composition as the first adhesive is applied to the first adhesive layer 3a', on which a plurality of abrasive grains 2 are dispersed and attached, to form a second adhesive layer 3b' corresponding to the upper base layer constituting the base portion 3 of the substrate-less abrasive, thereby forming a first composite film corresponding to a sheet-like substrate-less abrasive on the surface of the support 10 (FIG. 6(d)). The second adhesive may be prepared, for example, by blending a base component, a crosslinking agent, a dilution solvent, and, if necessary, a filler in appropriate proportions and stirring and mixing them using a stirrer. The stirrer is not particularly limited, but examples include a disper mixer, an ultra mixer, a homogenizer, and a planetary stirring and defoaming machine. Furthermore, when the base components constituting the first adhesive layer 3a' and the second adhesive layer 3b' have the same composition, the first composite film is formed as a single film with essentially no interface, as in the substrate-less abrasive 1 shown in Figure 1; and when the first adhesive layer 3a' and the second adhesive layer 3b' have different compositions, the first composite film is formed as a sheet-like two-layer composite film, as in the substrate-less abrasive 1A shown in Figure 2.

[0051] (5) Support Peeling Step S4 The support peeling step S4 is a step of peeling the first composite film from the release sheet 10, which is the support, to obtain the substrate-less abrasive 1 (FIG. 6(e)).

[0052] The thickness of the release sheet 10 is not particularly limited, but is preferably in the range of 25 to 100 μm, for example. <Uses> The substrate-less abrasive of this embodiment is used by cutting it into a tape, disk, or other shape for polishing, for example, materials such as metals, ceramics, glass, and single crystals, or the surfaces of magnetic hard disks, magnetic heads, semiconductor substrate surfaces, magnetic heads, lenses, etc., or the end faces of optical fibers. In particular, the polishing film of this embodiment is suitable for polishing the painted surface of an exterior panel having a curved shape, such as the exterior panel of an automobile body.

[0053] Furthermore, since the abrasive material of this embodiment does not have a substrate, there is no problem of the abrasive layer peeling off from the substrate, and in addition, the amount of waste can be reduced compared to abrasive materials that use a film or sheet made of plastic such as PET as the substrate.

[0054] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0055] Next, in order to further clarify the effects of the present invention, examples and comparative examples will be described, but the present invention is not limited to these examples.

[0056] Example 1 Example 1 has the cross-sectional structure shown in FIG. 1. A first adhesive was prepared by blending 100 parts by weight of polyester-based urethane resin as the base component, 4 parts by weight of a cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent, and uniformly stirring the mixture using a stirrer. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method so that the film thickness after drying was 25 μm, forming a first adhesive layer. Subsequently, alumina abrasive grains with a particle size of P400 (particle size of ds-50: 35 μm) were attached to the first adhesive layer using electrostatic deposition, and the resulting layer was dried using a constant temperature dryer (temperature: 120°C) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm-thick carrier film manufactured by Nan Ya Plastics Corp., model number H375A. Next, in order to more firmly fix the abrasive grains on the surface of the lower base layer of the base portion, a second adhesive was prepared by mixing 100 parts by weight of polyester urethane resin, 75 parts by weight of crosslinking agent (isocyanate curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent, and uniformly stirring the mixture using a mixer. The mixture was then applied by roll coating and dried and cured in a constant temperature oven (120 ° C), forming a second adhesive layer (thickness: 7 μm) which is the upper base layer of the base portion. A first composite film corresponding to a sheet-like substrate-less abrasive was then formed on the surface of the release sheet. The first composite film was then peeled off from the release sheet to obtain the substrate-less abrasive of Example 1 (total thickness including the abrasive grains (vertical distance from the bottom surface of the base portion 3 to the tip (apex) of the abrasive grain 2): 55 μm).

[0057] Example 2 Example 2 has the cross-sectional structure shown in FIG. 2. A first adhesive was prepared by blending 100 parts by weight of polyester-based urethane resin as the base component, 4 parts by weight of a cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent, and uniformly stirring the mixture using a stirrer. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method to form a first adhesive layer with a film thickness of 25 μm after drying. Alumina abrasive grains with a particle size of P400 (particle size of ds-50: 35 μm) were then attached to the first adhesive layer by electrostatic deposition and dried in a constant temperature dryer (temperature: 120°C) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm thick model H375A manufactured by Nan Ya Plastics Corp. Next, in order to more firmly fix the abrasive grains to the surface of the lower base layer of the base portion, a soft epoxy resin mixture (composed of a soft epoxy resin, an epoxy curing agent, and a diluting solvent) was applied by roll coating, and then dried and cured in a constant temperature dryer (120°C) to form a second adhesive layer, which was the upper base layer of the base portion (thickness: 7 μm). A first composite film corresponding to a sheet-like substrateless abrasive was formed on the surface of the release sheet. The soft epoxy resin used in the second adhesive layer had a Type A durometer hardness of 75. The first composite film was then peeled off from the release sheet to obtain the substrateless abrasive of Example 1 (total thickness including the abrasive grains: 55 μm).

[0058] Example 3 Example 3 has the cross-sectional structure shown in Figure 4. As the base component, 100 parts by weight of polyester-based urethane resin, 25 parts by weight of filler (calcium carbonate), 4 parts by weight of cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent were blended and uniformly stirred using a mixer to prepare a first adhesive. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method so that the film thickness after drying was 25 μm to form a first adhesive layer. Thereafter, alumina abrasive grains with a particle size of P400 (particle diameter of ds-50: 35 μm) were attached to the first adhesive layer by electrostatic deposition and dried using a constant temperature dryer (temperature: 120 ° C.) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm thick carrier film manufactured by Nan Ya Plastics Corp., model number H375A. Next, to more firmly fix the abrasive grains to the surface of the lower base layer of the base, a soft epoxy resin mixture (composed of a soft epoxy resin, an epoxy curing agent, and a diluting solvent) was applied by roll coating and then dried and cured in a constant temperature oven (120°C) to form a second adhesive layer (thickness: 7 μm) which was the upper base layer of the base. A first composite film corresponding to the sheet-like substrateless abrasive was then formed on the surface of the release sheet. The soft epoxy resin used in the second adhesive layer had a Type A durometer hardness of 75. The first composite film was then peeled off from the release sheet to obtain the substrateless abrasive of Example 1 (total thickness including the abrasive grains: 55 μm).

[0059] Example 4 Example 4 has the cross-sectional structure shown in Figure 4. As the base component, 100 parts by weight of polyester-based urethane resin, 25 parts by weight of filler (wollastonite), 4 parts by weight of cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent were blended and uniformly stirred using a mixer to prepare a first adhesive. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method so that the film thickness after drying was 25 μm to form a first adhesive layer. Thereafter, alumina abrasive grains with a particle size of P400 (particle diameter of ds-50: 35 μm) were attached to the first adhesive layer by electrostatic deposition and dried using a constant temperature dryer (temperature: 120 °C) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm thick carrier film manufactured by Nan Ya Plastics Corp., model number H375A. Next, to more firmly fix the abrasive grains to the surface of the lower base layer of the base, a soft epoxy resin mixture (composed of a soft epoxy resin, an epoxy curing agent, and a diluting solvent) was applied by roll coating and then dried and cured in a constant temperature oven (120°C) to form a second adhesive layer (thickness: 7 μm) which was the upper base layer of the base. A first composite film corresponding to the sheet-like substrateless abrasive was then formed on the surface of the release sheet. The soft epoxy resin used in the second adhesive layer had a Type A durometer hardness of 75. The first composite film was then peeled off from the release sheet to obtain the substrateless abrasive of Example 1 (total thickness including the abrasive grains: 55 μm).

[0060] Example 5 has the cross-sectional structure shown in FIG. 4. As the base component, 100 parts by weight of polyester-based urethane resin, 15 parts by weight of filler (titanium oxide), 4 parts by weight of cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent were blended and uniformly stirred using a mixer to prepare a first adhesive. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method so that the film thickness after drying was 25 μm to form a first adhesive layer. Thereafter, alumina abrasive grains with a particle size of P400 (particle diameter of ds-50: 35 μm) were attached to the first adhesive layer by electrostatic deposition and dried using a constant temperature dryer (temperature: 120 ° C.) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm thick carrier film manufactured by Nan Ya Plastics Corp., model number H375A. Next, to more firmly fix the abrasive grains to the surface of the lower base layer of the base, a soft epoxy resin mixture (composed of a soft epoxy resin, an epoxy curing agent, and a diluting solvent) was applied by roll coating and then dried and cured in a constant temperature oven (120°C) to form a second adhesive layer (thickness: 7 μm) which was the upper base layer of the base. A first composite film corresponding to the sheet-like substrateless abrasive was then formed on the surface of the release sheet. The soft epoxy resin used in the second adhesive layer had a Type A durometer hardness of 75. The first composite film was then peeled off from the release sheet to obtain the substrateless abrasive of Example 1 (total thickness including the abrasive grains: 55 μm).

[0061] Example 6 Example 6 has the cross-sectional structure shown in FIG. 4. As the base component, 100 parts by weight of polyester-based urethane resin, 15 parts by weight of filler (potassium titanate), 4 parts by weight of cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent were blended and uniformly stirred using a mixer to prepare a first adhesive. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method so that the film thickness after drying was 25 μm to form a first adhesive layer. Thereafter, alumina abrasive grains with a particle size of P400 (particle diameter of ds-50: 35 μm) were attached to the first adhesive layer by electrostatic deposition and dried using a constant temperature dryer (temperature: 120 ° C.) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm thick carrier film manufactured by Nan Ya Plastics Corp., model number H375A. Next, to more firmly fix the abrasive grains to the surface of the lower base layer of the base, a soft epoxy resin mixture (composed of a soft epoxy resin, an epoxy curing agent, and a diluting solvent) was applied by roll coating and then dried and cured in a constant temperature oven (120°C) to form a second adhesive layer (thickness: 7 μm) which was the upper base layer of the base. A first composite film corresponding to the sheet-like substrateless abrasive was then formed on the surface of the release sheet. The soft epoxy resin used in the second adhesive layer had a Type A durometer hardness of 75. The first composite film was then peeled off from the release sheet to obtain the substrateless abrasive of Example 1 (total thickness including the abrasive grains: 55 μm).

[0062] Example 7 Example 7 has the cross-sectional structure shown in FIG. 4. As the base component, 100 parts by weight of polyester-based urethane resin, 15 parts by weight of filler (potassium titanate), 4 parts by weight of cross-linking agent (isocyanate-based curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent were blended and uniformly stirred using a mixer to prepare a first adhesive. Next, the first adhesive was uniformly applied to a silicone-release-treated carrier film (release sheet) using a comma method so that the film thickness after drying was 25 μm to form a first adhesive layer. Thereafter, alumina abrasive grains with a particle size of P400 (particle diameter of ds-50: 35 μm) were attached to the first adhesive layer by electrostatic deposition and dried using a constant temperature dryer (temperature: 120 ° C.) to form a lower base layer (thickness: 25 μm) of the base portion. The carrier film used was a 75 μm thick carrier film manufactured by Nan Ya Plastics Corp., model number H375A. Next, in order to more firmly fix the abrasive grains to the surface of the lower base layer of the base portion, a second adhesive was prepared by blending 100 parts by weight of polyester urethane resin, 75 parts by weight of a crosslinking agent (isocyanate curing agent), and an appropriate amount of methyl ethyl ketone (MEK) as a dilution solvent, and uniformly stirring the mixture using a mixer. The mixture was then applied by roll coating and dried and cured in a constant temperature oven (120°C) to form a second adhesive layer, which was the upper base layer of the base portion (thickness: 7 μm). A first composite film, corresponding to a sheet-like substrate-less abrasive, was then formed on the surface of the release sheet. The first composite film was then peeled off from the release sheet to obtain the substrate-less abrasive of Example 1 (total thickness including the abrasive grains: 55 μm).

[0063] Conventional Example 1 is an abrasive having a substrate with a cross-sectional structure shown in Figure 7, where the substrate is PET (A-4360 manufactured by Toyobo) with a thickness of 75 μm, and the abrasive layer formed on the substrate is made of alumina abrasive grains with a particle size of P400 (particle size of ds-50: 35 μm), the first adhesive is urethane resin, and the thickness of the first adhesive layer is 6 μm. The second adhesive is phenolic resin that is harder than hard epoxy resin (type A durometer hardness: 96), and the thickness of the second adhesive layer is 30 μm.

[0064] Conventional Example 2 is an abrasive having a substrate as shown in Figure 7, in which the substrate is made of thermoplastic polyurethane (TPU) having a thickness of 35 μm, the abrasive layer formed on the substrate is made of alumina abrasive grains having a grain size of P400 (particle size of ds-50: 35 μm), the first adhesive is made of urethane resin, and the thickness of the first adhesive layer is 14 μm. The second adhesive is also made of urethane resin, and the thickness of the second adhesive layer is 25 μm.

[0065] (Comparative Example 1) In Comparative Example 1, a substrate-less abrasive material 1 was produced in the same manner as in Example 1, except that a hard epoxy resin (type A durometer hardness: 96) was used instead of a polyester-based urethane resin as the base component of the first adhesive and the second adhesive layer.

[0066] <Evaluation of Mechanical Properties of Abrasives> (I) Durometer Hardness The durometer hardness of a substrate-less abrasive can be measured by stacking, for example, 20 mm × 20 mm test pieces to a thickness of 2.5 mm or more, and slowly pressing a durometer (model number: GS-706N (manufactured by Teclock Corporation)) against the stack so that the indenter is perpendicular to the measurement surface.

[0067] (II) Tensile strength The tensile strength of a substrate-less abrasive can be measured by cutting the prepared substrate-less abrasive into a test piece of 25 mm x 150 mm, and using a Tensilon universal testing machine RTG-1225 (manufactured by A&D Co., Ltd.) to pull the test piece in the longitudinal direction under conditions of a chuck distance of 100 mm and a pulling speed of 200 mm / min, and measuring the maximum point load at this time as the tensile strength (MPa).

[0068] (III) Tensile elongation The tensile elongation of a substrate-less abrasive can be measured by cutting the prepared substrate-less abrasive into a test piece of 25 mm × 150 mm, and pulling the test piece in the longitudinal direction using a Tensilon universal testing machine RTG-1225 (manufactured by A&D Co., Ltd.) under conditions of a chuck distance of 100 mm and a pulling speed of 200 mm / min, and measuring the maximum elongation at this time as the tensile elongation (%).

[0069] <Abrasive Performance Evaluation> The abrasives were evaluated for their abrasiveness and followability. (i) A loop material with an adhesive layer was laminated onto the carrier film release surface of the abrasive to obtain a φ125 mm abrasive disc. A stainless steel (SUS) plate (size: 200 mm x 400 mm) spray-painted with nax Multi Eco [3:1] 20LX Clear (manufactured by Nippon Paint) was prepared as the workpiece. As a preliminary test, the plate was manually polished five times back and forth using a CLOG FREE #320 (manufactured by Sankyo Rikagaku Co., Ltd.). As a test step, a Double Action Sander 914L (manufactured by Compact Tools) and a cushion pad Super Ashire Pad (manufactured by KOVAX) were used to polish the abrasive 10 times at an air pressure of 0.45 Pa. After every five strokes, the abrasive was checked for removal of the polishing marks from the previous step. Abrasiveness was evaluated on a three-point scale based on the following evaluation criteria. The evaluation results are shown in Table 1. In this example, abrasiveness ratings of "1" and "2" were deemed to be good and acceptable, and abrasiveness rating of "3" was deemed to be unacceptable.

[0070] [Evaluation Criteria] 1: When polishing marks can be removed by 5 strokes 2: When polishing marks cannot be removed by 5 strokes, but can be removed by 10 strokes 3: When polishing marks cannot be removed even by 10 strokes

[0071] (ii) Trackability: To evaluate trackability, a gently curved outer panel (1350mm x 700mm) of an automobile hood was prepared as the workpiece and spray-painted with nax Multi Eco [3:1] 20LX Clear (Nippon Paint). The workpiece was polished using a Double Action Sander 914L (Compact Tools) and a KOVAX Super Ashile Pad cushion pad attached with an abrasive. The sander was moved back and forth along a linear path perpendicular to the curved surface at a constant speed (0.3 m / s) and a constant time (2 seconds (one round trip)) of 0.45 Pa air pressure. Any difference in the polished finish between the center and periphery of the workpiece (outer panel) was considered to be polishing unevenness. The extent of the polishing unevenness within the polished area (area size: 125mm x 300mm) was measured, and trackability during polishing of uneven curved surfaces was evaluated using the following three-point scale. The evaluation results are shown in Table 1. In this example, abrasiveness ratings of "1" and "2" were deemed to be good and acceptable, and abrasiveness rating of "3" was deemed to be unacceptable.

[0072] [Evaluation criteria] 1: No uneven polishing occurs, or even if uneven polishing occurs, it is less than 5% of the polished area. 2: Uneven polishing occurs in 5% or more but less than 20% of the polished area. 3: Uneven polishing occurs in 20% or more of the polished area.

[0073]

[0074] From the results in Table 1, it can be seen that the substrate-less abrasives of Examples 1 to 7 all had good conformability (the ability to conform and deform) to the uneven curved surface of the surface to be polished, and had excellent polishing properties. On the other hand, Conventional Example 1 and Comparative Example 1 both had poor conformability to the uneven curved surface of the surface to be polished. Furthermore, since Conventional Example 1 and Conventional Example 2 are both abrasives having a substrate, the amount of waste increased, and during polishing, the abrasive layer containing the grinding stone sometimes peeled off from the substrate at the adhesive interface, making it impossible to obtain sufficient polishing performance.

[0075] 1 Substrate-less abrasive material 2, 2B Abrasive grains 3, 3A, 3B Base portion 3a Lower base layer constituting base portion 3A 3b Upper base layer constituting base portion 3A 3c Lower base layer constituting base portion 3C 3d Upper base layer constituting base portion 3C 3a' First adhesive layer 3b' Second adhesive layer 4 Filler 5 Resin or elastomer 10 Release sheet 100 Abrasive material 102 Abrasive grains 103 Adhesive 104 Substrate 105 Abrasive layer

Claims

1. A substrate-less abrasive sheet having no substrate, and consisting of a base containing at least one of a resin and an elastomer in a total of 60% by volume or more of a base component, and a plurality of abrasive grains dispersed and held in the base, wherein the substrate-less abrasive has a Type A durometer hardness of 50 to 80 when measured in accordance with the hardness test specified in JIS K7311-1995, a tensile strength of 70 to 250 MPa, and a tensile elongation of 10 to 360%.

2. The substrate-less abrasive according to claim 1, wherein the base component of the base portion is a urethane resin.

3. A substrateless abrasive material as described in claim 1, wherein the base portion is composed of two layers, a lower base layer and an upper base layer, the base component of the lower base layer being a urethane resin, and the base component of the upper base layer being a soft epoxy resin.

4. The substrateless abrasive according to claim 3, wherein the ratio of the thickness of the lower base layer to the thickness of the upper base layer is in the range of 30:1 to 2:

1.

5. The substrateless abrasive according to claim 1, wherein said base portion further contains a filler having properties that increase the tensile strength and decrease the tensile elongation of said substrateless abrasive.

6. A method for producing a substrate-less abrasive as claimed in any one of claims 1 to 5, comprising the steps of: applying a first adhesive containing at least one base component of a resin and an elastomer to the surface of a support having releasability to form a first adhesive layer; adhering a plurality of abrasive grains in a dispersed state to the first adhesive layer; applying a second adhesive having the same or different composition as the first adhesive to the first adhesive layer to which the plurality of abrasive grains are adhered in a dispersed state to form a second adhesive layer, thereby forming a first composite film on the surface of the support that corresponds to a sheet-like substrate-less abrasive; and peeling the first composite film from the support to obtain the substrate-less abrasive.

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