Mill blank assembly

Abstract

Provided is a mill blank assembly which relaxes vibration generated during processing in a CAD / CAM processing machine and is excellent in processing accuracy. The present invention pertains to the mill blank assembly that includes a part to be processed, a holding part, and an adhesive composition, satisfying the following conditions [1] and / or [2]: [1] The loss coefficient tanδ at 20°C in a very micro-indentation test (nanoindenter) of a cured product of the adhesive composition is 0.70 or less; and [2] The ratio (X1 / Y1) of the peel adhesive strength (X1) and the fracture strain (Y1) in the compression-shear adhesion test between the part to be processed and the holding part at 20°C is 1,200 N / mm or less.

Description

Mill Blank Assembly

[0001] The present invention relates to a mill blank assembly including a workpiece, a holder, and an adhesive composition, and more particularly to a mill blank assembly including a workpiece, a holder, and an adhesive composition that can reduce vibrations that occur during machining using a CAD / CAM machine and improve machining accuracy.

[0002] Mill blank assemblies used in dental applications consist of a holder fixed to a processing machine, a workpiece, and an adhesive that bonds them together. To prevent the workpiece from detaching from the holder during processing and failing to produce the desired prosthesis, resins that firmly bond the holder and the workpiece have been used as adhesives (see Patent Documents 1 to 3, etc.).

[0003] For example, Patent Document 1 discloses a zirconia mill blank made of an epoxy adhesive and a cyanoacrylate adhesive, and Patent Document 2 discloses an adhesive composition containing a 2-cyanoacrylic acid ester and a specific (meth)acrylate compound or a (meth)acrylamide compound.

[0004] Furthermore, Patent Document 3 discloses a mill blank assembly in which the support portion has a specific surface roughness and surface properties, thereby reducing the risk of coming off.

[0005] JP 2020-151235 A JP 2018-76272 A JP 2020-068873 A

[0006] The mill blank assemblies disclosed in Patent Documents 1 to 3 use adhesive compositions with a high elastic modulus for the purpose of strong adhesion. However, the inventors discovered a problem in that when the mill blank assemblies disclosed in Patent Documents 1 to 3 are processed using a CAD / CAM processing machine, the vibrations generated by the rotation of the milling bur during processing cannot be sufficiently alleviated, resulting in a decrease in processing accuracy.

[0007] An object of the present invention is to provide a mill blank assembly that reduces vibrations that occur during machining with a CAD / CAM machining machine and provides excellent machining accuracy.

[0008] As a result of extensive research into solving the above problems, the inventors discovered that vibrations that occur during processing with a CAD / CAM processing machine can be alleviated by, for example, keeping the ratio of the shear force at break to the displacement up to break within a predetermined range in the "stress-strain curve" in a compression shear adhesion test of the processed part and the holding part. Based on this finding, they conducted further research and completed the present invention.

[0009] The present invention includes the following inventions. [1] A mill blank assembly comprising a workpiece, a holding part, and an adhesive composition, which satisfies the following conditions [1] and / or [2]: [1] A cured product of the adhesive composition has a loss factor tanδ of 0.70 or less at 20°C in an ultra-microindentation test (nanoindenter); [2] A ratio (X1 / Y1) of peel adhesion strength (X1) to fracture strain (Y1) between the workpiece and the holding part in a compressive shear adhesion test at 20°C is 1200 N / mm or less. [2] A cured product of the adhesive composition has a storage modulus E' of 200 N / mm or less at 20°C in an ultra-microindentation test. 2 [3] The mill blank assembly according to [1], wherein the cured product of the adhesive composition has a loss modulus E" of 100 N / mm at 20°C in an ultra-microindentation test. 2[4] The mill blank assembly according to [1] or [2], wherein the peel adhesion strength (X1) at 20°C in the compressive shear adhesion test is 100 N or more. [5] The mill blank assembly according to [1] or [4], wherein the breaking strain (Y1) at 20°C in the compressive shear adhesion test is 0.38 to 1.0 mm. [6] The mill blank assembly according to any of [1] to [5], wherein the adhesive composition forms a layer held between the workpiece and a holding part, and the thickness of the layer is 5 to 500 μm. [7] The mill blank assembly according to any of [1] to [6], wherein the Vickers hardness of the workpiece, measured in accordance with JIS Z 2244:2009, is 40 to 140 HV 5 / 30. [8] The mill blank assembly according to any one of [1] to [7], wherein the adhesive composition comprises at least one selected from the group consisting of epoxy-modified silicone compounds, (meth)acrylic compounds, and urethane compounds (excluding cyanoacrylate compounds). [9] The mill blank assembly according to any one of [1] to [8], wherein the workpiece comprises an oxide ceramic.

[10] The mill blank assembly according to any one of [1] to [9], wherein the workpiece comprises at least one selected from the group consisting of zirconia, alumina, and glass ceramics.

[11] The mill blank assembly according to any one of [1] to

[10] , wherein the holder comprises an aluminum alloy and / or an iron alloy.

[12] The mill blank assembly according to any one of [1] to

[11] , wherein the mill blank assembly is for dental use.

[13] A method for manufacturing a mill blank assembly according to any one of [1] to

[12] , comprising a step of curing an adhesive composition to bond a workpiece and a holding part, wherein the adhesive composition is either (i) a mixture obtained by mixing an epoxy resin and a silicone-modified polymer; (ii) a mixture obtained by mixing a (meth)acrylic monomer and / or a (meth)acrylic oligomer with a modified silicone; or (iii) at least one urethane-based compound (excluding cyanoacrylate compounds).

[0010] According to the present invention, it is possible to provide a mill blank assembly that can reduce vibrations that occur during machining using a CAD / CAM machine and achieve excellent machining accuracy. Furthermore, since vibrations during product transportation can also be sufficiently reduced, the amount of cushioning material used for product packaging can be reduced, reducing environmental impact and minimizing product boxes.

[0011] 1 is a schematic diagram showing a mill blank assembly according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a "stress-strain curve" in a compressive shear adhesion test of the mill blank assembly according to an embodiment of the present invention.

[0012] The mill blank assembly of the present invention includes a workpiece, a holder, and an adhesive composition, and satisfies the following conditions [1] and / or [2]: [1] a cured product of the adhesive composition has a loss factor tanδ of 0.70 or less at 20°C in an ultra-microindentation test (nanoindenter); [2] a ratio (X1 / Y1) of peel adhesion strength (X1) to fracture strain (Y1) in a compressive shear adhesion test between the workpiece and the holder at 20°C is 1200 N / mm or less.

[0013] In this specification, the methods for measuring and calculating the loss factor tan δ at 20°C, the storage modulus E' at 20°C, and the loss modulus E" at 20°C in an ultra-microindentation test (nanoindenter) of a cured product of an adhesive composition are as described in the Examples below. In this specification, the upper and lower limits of the numerical ranges (contents of each component, values ​​calculated from each component, and each physical property, etc.) can be combined as appropriate.

[0014] The mill blank assembly of the present invention provides the adhesive composition with the minimum elastic properties required during processing, and also has increased viscous properties, thereby making it possible to mitigate vibrations that occur during processing on a CAD / CAM processing machine, thereby mitigating the difference in vibration frequency between the processed part and the holding part, and ensuring processing accuracy when processing the processed part to obtain a prosthesis.

[0015] As shown in Figures 1A and 1B, the mill blank assembly of the present invention includes a workpiece (1), a retaining portion (2), and an adhesive composition (3). As shown in Figure 1B, when viewed from the axial direction of the retaining portion (2), the adhesive composition (3) may be applied only to the same area as the bottom surface of the retaining portion (2), or as shown in Figure 1A, it may be applied to the entire joint surface of the workpiece (1) with the retaining portion (2), or the adhesive composition may be applied to only a portion of the retaining portion (2). Each embodiment will be described below.

[0016] In one embodiment, the mill blank assembly of the present invention includes a workpiece, a holding part, and an adhesive composition, and satisfies condition [1]. Hereinafter, this embodiment will be referred to as the "first embodiment." Specifically, condition [1] is that the loss factor tan δ at 20°C in an ultra-microindentation test (nanoindenter) of a cured product of the adhesive composition is 0.70 or less. The loss factor tan δ at 20°C is calculated by tan δ = E" / E', using the storage modulus E' of the cured product of the adhesive composition at 20°C and the loss modulus E" of the cured product of the adhesive composition at 20°C. Hereinafter, the loss factor tan δ at 20°C, the storage modulus E' of the cured product of the adhesive composition at 20°C, and the loss modulus E" of the cured product of the adhesive composition at 20°C refer to values ​​measured and calculated for the cured product of the adhesive composition in the ultra-microindentation test.

[0017] The storage modulus E' of the cured product at 20°C as an elastic index (hereinafter also referred to simply as "storage modulus E'") is set to 200 N / mm because it can reduce vibration during processing, improve processing accuracy, and make it difficult for the workpiece to separate from the holding part or for a part of the workpiece to separate during processing or transportation. 2 Preferably, it is 150 N / mm or less. 2 More preferably, it is 120 N / mm or less. 2 More preferably, it is 90 N / mm or less. 2Furthermore, it is most preferable that the storage modulus E' is 5 N / mm or less, because the material is viscous and has the minimum elasticity required during processing, can mitigate vibrations that occur during processing with a CAD / CAM processing machine, can ensure the processing precision of the prosthesis, and can mitigate the difference in vibration frequency between the processed part and the holding part during transportation. 2 It is preferable that the strength is 8 N / mm or more. 2 More preferably, it is 10 N / mm or more. 2 It is even more preferable that the storage modulus E' at 20°C is equal to or greater than this. The lower the storage modulus E' of the cured product at 20°C, the lower the elastic properties and the higher the viscous properties of the cured product tend to be, so this point can also be taken into consideration when adjusting the viscoelasticity of the cured product. Furthermore, in order to make it less likely for the workpiece or a portion of the workpiece to detach from the holder under low-temperature conditions, it is preferable that the storage modulus E' at -30°C, for example, be within the same range as the range of the storage modulus E' at 20°C.

[0018] The loss modulus E" of the cured product at 20°C as a viscosity index (hereinafter also referred to simply as "loss modulus E") is set to 100 N / mm because the product is viscous and has the minimum elasticity required during processing, can mitigate vibrations that occur during processing with a CAD / CAM processing machine, can ensure the processing precision of the prosthesis, and can mitigate the difference in vibration frequency between the processed part and the holding part during transportation. 2 Preferably, it is 80 N / mm or less. 2 More preferably, it is 50 N / mm or less. 2 Furthermore, the loss modulus E" is preferably 0.5 N / mm or less, since the elastic properties decrease and the viscous properties increase, making it easier to mitigate vibrations that occur during processing with a CAD / CAM processing machine and making it possible to mitigate the difference in vibration frequency between the processed part and the holding part. 2 It is preferable that the strength is 1 N / mm or more. 2 More preferably, it is 2 N / mm 2Furthermore, in order to make it difficult for the workpiece or a part of the workpiece to be detached from the holder under low-temperature conditions, it is preferable that the loss modulus E" at -30°C is within the same range as the range of the loss modulus E" at 20°C.

[0019] The loss factor tan δ at 20°C measured by an ultra-microindentation test (hereinafter also simply referred to as "loss factor tan δ at 20°C") is preferably 0.12 or more, more preferably 0.14 or more, and even more preferably 0.15 or more, from the viewpoints of being able to reduce vibration during processing, improving processing accuracy, and making it difficult for the workpiece to detach from the holder or for a portion of the workpiece to detach during processing or transportation. Furthermore, tan δ is preferably 0.70 or less, more preferably 0.60 or less, more preferably 0.55 or less, and even more preferably 0.50 or less. Furthermore, from the viewpoint of making it difficult for the workpiece to detach from the holder or for a portion of the workpiece to detach under low-temperature conditions, for example, the loss factor tan δ at -30°C is preferably within the same range as the range of the loss factor tan δ at 20°C. Furthermore, in order to prevent the workpiece from detaching from the holder or a portion of the workpiece from detaching under low-temperature conditions, in a graph in which the horizontal axis represents the measurement temperature and the vertical axis represents tan δ measured at each temperature, it is preferable that the peak top of the loss factor tan δ is in a temperature range lower than the temperature to which the mill blank is exposed during transportation, storage, etc. The peak top of the loss factor tan δ is preferably below 20°C, more preferably below 0°C, and even more preferably below −30°C.

[0020] In another embodiment, the mill blank assembly of the present invention includes a processing portion, a retaining portion, and an adhesive composition, and satisfies condition [2]. Hereinafter, this embodiment will be referred to as the "second embodiment." Condition [2] specifically relates to the mill blank assembly of the present invention, where the ratio (X1 / Y1) of the peel adhesion strength (X1) in a compressive shear adhesion test between the processing portion and the retaining portion at 20°C (hereinafter also referred to as "peel adhesion strength (X1)" or "peel adhesion strength (X1) at 20°C") to the fracture strain (Y1) in the same test (hereinafter also referred to as "fracture strain (Y1)" or "fracture strain (Y1) at 20°C") is 1200 N / mm or less. The ratio (X1 / Y1) of the peel strength (X1) to the breaking strain (Y1) is preferably 1200 N / mm or less, more preferably 1150 N / mm or less, more preferably 1100 N / mm or less, even more preferably 1000 N / mm or less, and most preferably 900 N / mm or less, from the viewpoint of being able to mitigate vibration during processing and increasing processing accuracy. Furthermore, the ratio (X1 / Y1) of the peel strength (X1) to the breaking strain (Y1) is preferably 550 N / mm or more, more preferably 600 N / mm or more, from the viewpoint of being able to mitigate vibration during processing and increasing processing accuracy. The methods for measuring the peel strength (X1) and the breaking strain (Y1) are as described in the Examples below. By ensuring that the ratio (X1 / Y1) of the peel strength (X1) to the breaking strain (Y1) is 1200 N / mm or less, the storage modulus E' can be adjusted within a predetermined range. When the ratio (X1 / Y1) of peel adhesion strength (X1) to fracture strain (Y1) is within the above-mentioned range, the slope of the "stress-strain curve" in the compressive shear adhesion test becomes gentler, as shown by the line on the right side of Figure 2, compared to the conventional technology (left side of Figure 2) in which the holding part suddenly separates from the processed part, and the holding part is prevented from suddenly separating from the processed part, making the processed part less likely to break and allowing more time for peeling. These characteristics make it possible to reduce vibration during processing and improve processing accuracy when processing with a CAD / CAM processing machine.Furthermore, in view of the fact that the workpiece or a portion of the workpiece is less likely to detach from the holding part even under low-temperature conditions, and in view of excellent processing precision and high temperature stability, the ratio (X2 / X1) of the peel adhesion strength (X2) in a compressive shear adhesion test between the processing part and the holding part after storage at -30°C (hereinafter also referred to as "peel adhesion strength (X2)" or "peel adhesion strength (X2) after storage at -30°C") to the peel adhesion strength (X1) at 20°C is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more.

[0021] The peel adhesion strength (X1) is preferably 100 N or more, more preferably 150 N or more, even more preferably 200 N or more, and most preferably 300 N or more, from the viewpoint of preventing detachment between the workpiece and the holder during processing or transportation. The peel adhesion strength (X1) is preferably within the above range regardless of the measurement temperature, from the viewpoint of preventing detachment between the workpiece and the holder during processing or transportation. For example, the peel adhesion strength (X2) after storage at -30°C is also preferably within the same range as the peel adhesion strength (X1).

[0022] The breaking strain (Y1) at 20 ° C. is preferably 0.38 mm or more, more preferably 0.50 mm or more, and even more preferably 0.55 mm or more, from the viewpoint of reducing vibration during processing, increasing processing accuracy, and reducing the likelihood of detachment between the workpiece and the holding part during processing or transportation. Furthermore, the breaking strain (Y1) is preferably 1.0 mm or less, more preferably 0.90 mm or less, and even more preferably 0.80 mm or less, from the viewpoint of reducing distortion during processing and increasing processing accuracy. The breaking strain (Y1) is preferably within the above range regardless of the measurement temperature, from the viewpoint of reducing the likelihood of detachment between the workpiece and the holding part during processing or transportation. For example, the breaking strain (Y2) in a compressive shear adhesion test of the processing part and the holding part after storage at -30 ° C. (hereinafter also referred to as "breaking strain (Y2)" or "breaking strain (Y2) after storage at -30 ° C.") is also preferably within the same range as the breaking strain (Y1).

[0023] In the mill blank assembly of the present invention, the adhesive composition forms a layer held between the workpiece and the holder. In the first embodiment, the thickness of the layer is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, because it is easy to achieve the desired loss factor tan δ when a predetermined adhesive composition is used, and / or the desired ratio (X1 / Y1) of the peel adhesion strength (X1) to the fracture strain (Y1) in the second embodiment. In the first embodiment, the thickness of the layer is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less, because it is easy to achieve the desired loss factor tan δ when a predetermined adhesive composition is used, and / or the desired ratio (X1 / Y1) of the peel adhesion strength (X1) to the fracture strain (Y1) in the second embodiment. Note that the thickness of the adhesive layer is treated as having no thickness variation, since the mill blank assembly is bonded under a constant load during manufacture. However, if there is variation in thickness, the minimum thickness can be used as the thickness of the adhesive layer.

[0024] In the mill blank assembly of the present invention, in order to ensure that the mill blank assembly is suitable for machining using a CAD / CAM machine and has sufficient mechanical strength as a dental prosthesis, the Vickers hardness of the workpiece in the first and / or second embodiments is preferably 40 HV 5 / 30 or more, more preferably 60 HV 5 / 30 or more, even more preferably 65 HV 5 / 30 or more, and most preferably 70 HV 5 / 30 or more. Furthermore, in order to ensure that the mill blank assembly is suitable for machining using a CAD / CAM machine and has sufficient mechanical strength as a dental prosthesis, the Vickers hardness of the workpiece in the first and / or second embodiments is preferably 140 HV 5 / 30 or less, more preferably 135 HV 5 / 30 or less, even more preferably 130 HV 5 / 30 or less, and most preferably 125 HV 5 / 30 or less. Vickers hardness can be measured in accordance with JIS Z 2244:2009. "HV 5 / 30" means that the test force is held at a load of 5 kgf for 30 seconds. If the sample cracks or the indentation is chipped at HV 5 / 30, HV 1 / 10 may be used instead. Therefore, in this specification, the Vickers hardness of the processed portion can be interpreted as "preferably 40 HV 1 / 10 or more," etc.

[0025] In the mill blank assembly according to the first and / or second embodiment of the present invention, the adhesive composition preferably contains at least one selected from the group consisting of an epoxy-modified silicone compound, a (meth)acrylic compound, and a urethane-based compound, since it is easy to bring the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesion strength (X1) to the fracture strain (Y1) at 20°C within the desired range. An epoxy-modified silicone compound is more preferred, since it sufficiently damps vibrations generated during processing with a CAD / CAM processing machine, exhibits excellent processing accuracy, and has high adhesion and water resistance. The adhesive composition may be used alone or in combination with two or more types. However, when a cyanoacrylate compound is used, it is not possible to sufficiently increase the viscous properties while reducing the elastic properties, and therefore it is not possible to set the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesion strength (X1) to the fracture strain (Y1) at 20°C within the desired range. Therefore, it is preferable that the adhesive composition does not contain a cyanoacrylate compound. The adhesive composition may be in the form of a one-component type or a two-component type.

[0026] The epoxy-modified silicone compound is not particularly limited as long as it is obtained by reacting a modified silicone resin with an epoxy resin, and any known epoxy resin (e.g., bisphenol A-type epoxy resin) can be used as the epoxy resin, as long as it achieves the effects of the present invention. The modified silicone resin is not particularly limited as long as it achieves the effects of the present invention, and any known modified silicone resin can be used. The epoxy-modified silicone compound can form a sea-island structure in which epoxy resin domains are dispersed within a flexible matrix phase of the modified silicone resin. It is believed that this structure allows the modified silicone resin to have excellent adhesive properties while retaining the rubber-like elasticity after curing, which is a characteristic of the modified silicone resin. Furthermore, during the curing process, the modified silicone resin becomes a continuous phase, imparting a morphology in which the epoxy resin is finely dispersed.

[0027] As the epoxy-modified silicone compound used in the present invention, commercially available products can be used as long as the loss factor tan δ at 20°C and / or the ratio (X1 / Y1) of peel adhesive strength (X1) to fracture strain (Y1) can be set within the desired range described above. Commercially available products include "EP001K" (trade name, two-component epoxy-modified silicone elastic adhesive, base: epoxy resin, curing agent: modified silicone polymer, Tg: -65°C, manufactured by Cemedine Co., Ltd.), which can be used in a wide temperature range of -40 to 100°C; "EP001N" (trade name, two-component epoxy-modified silicone elastic adhesive, base: epoxy resin (bisphenol A epoxy resin), curing agent: modified silicone resin, manufactured by Cemedine Co., Ltd.), which can be used in a wide temperature range of -60 to 120°C; and "Bond" (trade name, two-component epoxy-modified silicone elastic adhesive, base: epoxy resin (bisphenol A epoxy resin), curing agent: modified silicone resin, manufactured by Cemedine Co., Ltd.), which can be used in a wide temperature range of -30 to 80°C. Examples of suitable elastic adhesives include "EFLEX (registered trademark)" (trade name, one-component room temperature curing epoxy-modified silicone resin, manufactured by Konishi Co., Ltd.), and "BOND MOS-8" (trade name, two-component mixed epoxy-modified silicone resin, manufactured by Konishi Co., Ltd.), which can be used in a wide temperature range of -60 to 120°C, and have rubber-like elasticity after curing. "EP001K" and "EP001N" are preferred because they are more likely to reduce vibrations that occur during processing with a CAD / CAM processing machine.

[0028] Examples of (meth)acrylic compounds include (meth)acrylic-modified silicone compounds, butyl acrylate having a long-chain alkyl group on the side chain, and 2-ethylhexyl acrylate, which can easily adjust the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesive strength (X1) to the breaking strain (Y1) at 20°C within the desired ranges. Of these, acrylic-modified silicone compounds are preferred. Commercially available (meth)acrylate compounds can be used as long as they can adjust the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesive strength (X1) to the breaking strain (Y1) at 20°C within the desired ranges. Examples of commercially available products include elastic adhesives that have rubber-like elasticity after curing, such as "Super X No. 8008" (trade name, one-component room temperature curing acrylic-modified silicone resin elastic adhesive, Tg: -63°C, manufactured by Cemedine Co., Ltd.). A low molecular weight (meth)acrylic compound may be added to the (meth)acrylic compound to shift the peak top of tan δ to a lower temperature side.

[0029] The urethane compound has a urethane bond, and by utilizing an addition reaction (urethanization reaction) between a polyisocyanate and a polyol, it is possible to control the microphase-separated structure specific to urethane resins. The microphase-separated structure is composed of two phases: a hard domain and a soft domain. The hard domain functions as a hard segment having a urethane bond with high cohesive energy due to hydrogen bonding, and the soft domain is composed of methylene chains, ether, and ester bonds with low cohesive energy. The two-phase structure, consisting of a hard domain and a soft domain, provides high toughness and flexibility and can reduce vibrations that occur during processing with a CAD / CAM processing machine. As the urethane compound, commercially available products can be used as long as the loss factor tan δ at 20°C and / or the ratio (X1 / Y1) of the peel adhesion strength (X1) to the breaking strain (Y1) can be set within the desired range.

[0030] In the first and second embodiments, the workpiece preferably contains an oxide ceramic, more preferably a dental oxide ceramic. Examples of dental oxide ceramics include zirconia, alumina, and glass ceramics. One type of dental oxide ceramic may be used alone, or two or more types may be used in combination. When the dental oxide ceramic is zirconia, the zirconia may contain a stabilizer (hereinafter also referred to as a "stabilizer") capable of suppressing the phase transition of zirconia. The stabilizer is preferably capable of forming partially stabilized zirconia. The zirconia in the workpiece may be a zirconia molded body or a zirconia calcined body. A zirconia molded body is formed by applying an external force to a powder containing zirconia-based particles, and since it is a pre-fired product, it does not exhibit necking (sticking). When producing a zirconia molded body by a method including a step of press-molding a powder containing zirconia particles, the specific press-molding method is not particularly limited, and it can be performed using a known press molding machine. The zirconia calcined body can be a precursor (intermediate product) of the zirconia sintered body. In this specification, the zirconia calcined body refers to a state in which zirconia particles are necked (adhered) to each other and are not completely sintered. The zirconia calcined body can be obtained by calcining the zirconia molded body. In order to ensure blocking, the firing temperature (calcination temperature) in the calcination step is, for example, preferably 800°C or higher, more preferably 900°C or higher, and even more preferably 950°C or higher. Furthermore, the calcination temperature is, for example, preferably lower than 1200°C, more preferably 1150°C or lower, and even more preferably 1100°C or lower. Examples of the stabilizer include calcium oxide (CaO), magnesium oxide (MgO), yttria (Y2O3), cerium oxide (CeO2), scandium oxide (Sc2O3), niobium oxide (Nb2O5), lanthanum oxide (La2O3), erbium oxide (Er2O3), and praseodymium oxide (Pr6O 11Examples of oxides include oxides such as PrO, samarium oxide (SmO), europium oxide (EuO), and thulium oxide (TmO). Yttria is preferred because the zirconia sintered body has excellent translucency. The content of the stabilizer (preferably yttria) in the zirconia is preferably 3.0 mol% or more, more preferably 3.5 mol% or more, and even more preferably 4.0 mol% or more, based on the total moles of zirconia (zirconium (IV) oxide; ZrO)) and stabilizer, because the zirconia sintered body has excellent translucency. When the content is 3.0 mol% or more, the cubic crystal structure contained in the sintered body increases, improving the translucency of the zirconia sintered body. The content of the stabilizer is preferably 7.5 mol% or less, more preferably 7.0 mol% or less, and even more preferably 6.5 mol% or less. When the content is 7.5 mol % or less, it is possible to suppress a decrease in the strength of the zirconia sintered body. Any combination of these ranges may be used.

[0031] In the first and second embodiments, the retainer may be made of aluminum alloys, iron alloys, or other materials, as long as they can secure the workpiece. Examples of materials include aluminum and its alloys, iron and its alloys, pure iron, cast iron, stainless steel (e.g., SUS304, SUS316), nickel alloys (alumel, chromel, etc.), chromium alloys, cobalt alloys, carbon steel, manganese steel (e.g., SMn420, SMn433, SMn438, SMn443), invar alloys, molybdenum, copper, bronze, silver, gold, platinum, and the like. The alloys may be used without limitation in composition as long as they are recognized as such alloys. For example, a cobalt alloy may contain 42 to 65% cobalt. Among these materials, materials with a thermal expansion coefficient close to that of the workpiece are preferably used. The retainer may be made of a single material, or two or more materials may be used in combination.

[0032] The mill blank assembly of the present invention is particularly suitable for use in dental applications.

[0033] The method for manufacturing a mill blank assembly of the present invention includes a step of curing an adhesive composition to bond a workpiece and a holding part, wherein the adhesive composition is any one of: (i) a mixture obtained by mixing an epoxy resin with a silicone-modified polymer; (ii) a mixture obtained by mixing a (meth)acrylic monomer and / or a (meth)acrylic oligomer with a modified silicone; or (iii) at least one urethane-based compound (excluding cyanoacrylate compounds).

[0034] The mixture obtained by mixing the epoxy resin and the silicone-modified polymer in embodiment (i) of the adhesive composition is not particularly limited, and commercially available products can be used as long as it functions as an epoxy-modified silicone compound and can adjust the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesive strength (X1) to the breaking strain (Y1) within the desired ranges described above.

[0035] The mixture obtained by mixing at least two or more of the acrylic monomers and / or (meth)acrylic oligomers in embodiment (ii) of the adhesive composition is not particularly limited, as long as it can adjust the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesive strength (X1) to the breaking strain (Y1) within the desired ranges described above, and commercially available products (preferably, acrylic-modified silicone compounds, etc.) can be used.

[0036] The at least one urethane-based compound in the embodiment (iii) of the adhesive composition is not particularly limited, and commercially available products can be used as long as the loss factor tan δ and / or the ratio (X1 / Y1) of the peel adhesive strength (X1) to the breaking strain (Y1) can be adjusted within the desired ranges described above.

[0037] The step of curing the adhesive composition to bond the workpiece and the holding part is not particularly limited, and the bonding can be performed by a known method. As shown in Figures 1A and 1B, the area to which the adhesive composition is applied is not limited as long as the workpiece and the holding part can be bonded and the condition [1] and / or the condition [2] are satisfied, and the area can be appropriately selected.

[0038] The amount of adhesive composition to be applied can be appropriately selected so that the adhesive layer after curing falls within the desired range.

[0039] The present invention includes various combinations of all or part of the configurations in the above-described embodiments within the scope of the technical concept of the present invention, as long as the effects of the present invention are achieved. The present invention also includes embodiments that satisfy both condition [1] and condition [2] (embodiments in which the loss factor tan δ at 20°C is within the desired range described above and the ratio (X1 / Y1) of the peel strength (X1) to the breaking strain (Y1) is within the desired range described above).

[0040] Next, the present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way, and many modifications within the technical scope of the present invention are possible by those skilled in the art.

[0041] The types of adhesives used in the examples and comparative examples described below are as follows: Epoxy-modified silicone resin "EP001K": two-component epoxy-modified silicone elastic adhesive (product name "EP001K", base: epoxy resin, curing agent: modified silicone polymer, Tg: -65°C, manufactured by Cemedine Co., Ltd.) Epoxy-modified silicone resin "EP001N": two-component epoxy-modified silicone elastic adhesive (product name "EP001N", manufactured by Cemedine Co., Ltd.) Epoxy-modified silicone resin "MOS-8": two-component epoxy-modified silicone elastic adhesive (product name "Bond MOS-8", manufactured by Konishi Co., Ltd.) Epoxy-based resin "Hi-Super 5": two-component epoxy adhesive (product name "Hi-Super 5", manufactured by Cemedine Co., Ltd.) Cyanoacrylate-based resin "Aron Alpha 403X": cyanoacrylate adhesive (product name "Aron Alpha 403X", manufactured by Toa Gosei Co., Ltd.) The adhesives described above were all used according to the instructions attached to the product, by mixing the base agent and curing agent, waiting a few minutes, and then applying the mixture to the designated position of the holding part.

[0042] Example 1 The workpiece, holder, and adhesive composition used were those listed in Table 1. At room temperature (20°C), epoxy-modified silicone was applied to the workpiece so that the adhesive layer formed after curing had the thickness shown in Table 1. After joining the holder, a mill blank assembly was produced by curing the adhesive composition at room temperature while applying a load so that the adhesive layer reached the specified thickness. The physical properties of the resulting mill blank assembly, the workpiece, and the adhesive composition were evaluated using the following methods. The results for each physical property are summarized in Table 1 below.

[0043] [Examples 2 to 5 and Comparative Example 1] Mill blank assemblies were manufactured in the same manner as in Example 1, except that the workpiece portion, the holding portion, the adhesive composition, and the thickness of the adhesive layer were changed to those shown in Table 1.

[0044] [Measurement of Vickers hardness of processed portion] The Vickers hardness of the processed portion was measured in accordance with JIS Z 2244: 2009. Using a micro / macro Vickers hardness tester (product name "Falcon500", manufactured by Innovatest Japan Co., Ltd.), a load of 5 kgf was applied for 30 seconds, and the Hv value was calculated (arithmetic mean value of n = 10).

[0045] [Measurement of Thickness of Cured Adhesive Composition (Thickness of Adhesive Layer)] The mill blank assembly prepared above was cut, and the thickness of the cured adhesive composition on the cut surface was measured as the thickness of the adhesive layer. The thickness of the adhesive layer of the cured adhesive composition was measured by observation with an optical microscope (DIGITAL MICROSCOPE KH-7700: Hirox Co., Ltd.) (n=1). Note that the thickness of the adhesive layer was treated as having no variation in thickness because the adhesive layer was bonded under a constant load during the manufacture of the mill blank assembly.

[0046] [Measurement of dynamic viscoelasticity by nanoindentation test (nanoindenter)] Using a nanoindentation hardness tester (ENT-5X, manufactured by Elionix Co., Ltd.), dynamic viscoelasticity was measured by the following method. The holder was removed from the prepared mill blank assembly, and the cured portion of the adhesive composition remaining only on the holder side was used for measurement. Using a nanoindentation hardness tester (ENT-5X, manufactured by Elionix Co., Ltd.) as the measuring machine, the storage modulus E' and loss modulus E" of the cured adhesive composition were measured under the following conditions. From the obtained measured values, the loss factor tan δ = E" / E' was calculated. For one test piece in each Example and Comparative Example, the measurement distance was set to 100 μm, and data were obtained at three points at each of the set temperatures below, and the arithmetic mean value was calculated. <Measurement conditions> Test load: 200 μN Load and unload time: 10 sec (500 divisions, 20 msec step intervals) Load holding time: 5 sec Vibration frequency: 1.0 Hz Vibration time: 10 sec Amplitude: 20 μN Set temperature: 20°C and -30°C Indenter: Berkovich indenter Correction method in analysis: Oliver method

[0047] [Compression Shear Adhesion Test: Measurement of Peel Adhesion Strength] The holding part 2 was fixed (rotated 90 degrees in FIG. 1B and fixed horizontally), and a load was applied to the workpiece 1 at a point 18 mm from the adhesive surface (the surface to be bonded to the workpiece) using a support roller (the load direction was vertical). The load at which the workpiece 1 peeled from the holding part 2 was measured using a bench-top precision universal testing machine (Autograph AGS-5kNX, manufactured by Shimadzu Corporation). The support roller descended at a speed of 1.0 mm / sec. The peel adhesion strength was measured after adhering the workpiece 1 and the holding part 2 and leaving them to stand at 20°C for 1 day, or after adhering them to the holding part 2 and leaving them to stand at 20°C for 1 day, then leaving them to stand at -30°C for 1 day, and then further leaving them to stand at 20°C for 1 day (arithmetic mean value of n = 5). The adhesive area (adhesion area between the holding part 2 and the workpiece 1) in each mill blank assembly in the peel adhesion strength measurement was 317 [mm 2The adhesion area was calculated from the area of ​​the entire surface of the holding part 2 to be adhered to the workpiece 1 (the area of ​​the part where the holding part 2 overlaps with the workpiece 1 when FIG. 1B is viewed in a plan view from the vertical direction).

[0048] The peel adhesion strength (X1) at 20°C is preferably 100 N or more, more preferably 150 N or more, even more preferably 200 N or more, and most preferably 300 N or more, so that the workpiece is less likely to detach from the holder during processing of the workpiece. The peel adhesion strength (X2) at -30°C is also preferably in the same range as the peel adhesion strength (X1) at 20°C.

[0049] [Compression Shear Adhesion Test: Measurement of Breaking Strain] The displacement was read from the stress-strain curve graph obtained in the above [Compression Shear Adhesion Test: Measurement of Peel Adhesion Strength] and used as the breaking strain (arithmetic mean value of n = 5). As with the peel adhesion strength, the breaking strain was measured after leaving the specimens to stand at 20°C for 1 day after adhesion, or after leaving the specimens to stand at 20°C for 1 day after adhesion, then at -30°C for 1 day, and then further at 20°C for 1 day (arithmetic mean value of n = 5).

[0050] The breaking strain (Y1) at 20°C is preferably 0.38 mm or more, more preferably 0.50 mm or more, and even more preferably 0.55 mm or more, from the viewpoints of being able to mitigate vibration during processing, increasing processing accuracy, and making it difficult for the workpiece and the holding part to separate during processing or transportation. Furthermore, the breaking strain (Y1) is preferably 1.0 mm or less, more preferably 0.90 mm or less, and even more preferably 0.80 mm or less, from the viewpoints of reducing distortion during processing and increasing processing accuracy. The breaking strain (Y2) at -30°C is also preferably in the same range as the breaking strain (Y1) at 20°C.

[0051] [Evaluation of Machining Accuracy] Based on the three-dimensional NC data, the obtained mill blank assembly was machined into the shape of a predetermined dental prosthesis using a milling machine (trade name "DWX-52DC", manufactured by Roland DG Corporation) with an unused Katana (registered trademark) drill (manufactured by Kuraray Noritake Dental Co., Ltd., Φ2 mm, not diamond coated) (arithmetic mean value of n=10).

[0052] The processing accuracy was evaluated according to the following criteria: A: A dental prosthesis could be processed to the exact dimensions. B: There was one instance where a dental prosthesis could not be obtained to the exact dimensions. C: There were two or more instances where a dental prosthesis could not be obtained to the exact dimensions. D: No dental prosthesis could be obtained to the exact dimensions.

[0053]

[0054] From the above results, it was confirmed that the mill blank assembly of the present invention can sufficiently mitigate vibrations that occur during machining using a CAD / CAM machining machine, and also has excellent machining accuracy.

[0055] The mill blank assembly of the present invention is useful for dental applications and provides excellent machining accuracy because it can adequately dampen vibrations caused by the rotation of the milling bur during machining. Furthermore, the mill blank assembly of the present invention can also adequately dampen vibrations during product transportation, reducing the amount of cushioning material used for product packaging, thereby reducing environmental impact and minimizing product boxes.

[0056] 1 Processed part 2 Holding part 3 Adhesive composition

Claims

1. A mill blank assembly comprising a workpiece, a holding part, and an adhesive composition, and satisfying the following conditions [1] and / or [2]: [1] the loss factor tan δ of a cured product of the adhesive composition at 20°C in an ultra-microindentation test (nanoindenter) is 0.70 or less; [2] the ratio (X1 / Y1) of the peel adhesion strength (X1) to the breaking strain (Y1) in a compressive shear adhesion test of the workpiece and the holding part at 20°C is 1,200 N / mm or less.

2. The storage modulus E' of the cured product of the adhesive composition at 20°C in an ultra-microindentation test is 200 N / mm 2 2. The mill blank assembly of claim 1 , wherein:

3. The loss modulus E" of the cured product of the adhesive composition at 20°C in an ultra-microindentation test is 100 N / mm 2 3. The mill blank assembly of claim 1, wherein:

4. The mill blank assembly of claim 1, wherein the peel adhesion strength (X1) at 20°C in the compressive shear adhesion test is 100 N or more.

5. The mill blank assembly according to claim 1 or 4, wherein the breaking strain (Y1) at 20°C in the compressive shear adhesion test is 0.38 to 1.0 mm.

6. A mill blank assembly according to any one of claims 1, 2 or 4, wherein the adhesive composition forms a layer held between the workpiece and the holding part, and the thickness of the layer is 5 to 500 μm.

7. A mill blank assembly according to claim 1, 2 or 4, wherein the Vickers hardness of the processed portion measured in accordance with JIS Z 2244:2009 is 40 to 140 HV 5 / 30.

8. A mill blank assembly according to any one of claims 1, 2 or 4, wherein the adhesive composition comprises at least one selected from the group consisting of epoxy-modified silicone compounds, (meth)acrylic compounds, and urethane compounds (excluding cyanoacrylate compounds).

9. The mill blank assembly of claim 1, 2 or 4, wherein the workpiece comprises an oxide ceramic.

10. The mill blank assembly according to any one of claims 1, 2 or 4, wherein the workpiece comprises at least one material selected from the group consisting of zirconia, alumina and glass ceramics.

11. The mill blank assembly of any of claims 1, 2 or 4, wherein the retaining portion comprises an aluminum alloy and / or an iron alloy.

12. A mill blank assembly according to any of claims 1, 2 or 4 for dental applications.

13. A method for manufacturing a mill blank assembly according to any one of claims 1, 2 or 4, comprising a step of curing an adhesive composition to bond a workpiece and a retaining part, wherein the adhesive composition is either: (i) a mixture obtained by mixing an epoxy resin with a silicone modified polymer; (ii) a mixture obtained by mixing a (meth)acrylic monomer and / or a (meth)acrylic oligomer with a modified silicone; or (iii) at least one urethane-based compound (excluding cyanoacrylate compounds).

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