Method for producing polyurethane-based materials

Abstract

To provide a method capable of stably producing a polyurethane-based material having a crosslinked structure, and having excellent transparency as well as strength and water resistance.SOLUTION: There is provided a method for producing a polyurethane-based material which comprises: subjecting a primary raw material composition which comprises a diol compound (a1) having one or more radical polymerizable groups and a non-polyaddition radical polymerizable monomer (B) and may contain a radical polymerization initiator (C) to dehydration treatment and adjusting the water content contained in the composition to 20000 ppm or less based on the total mass of the liquid component; then adding a diisocyanate compound (a2) and subjecting the (a1) and (a2) to polyaddition to form a polyurethane component (A) having a radical polymerizable group in the molecule which has an average molecular weight of 1500 to 10000, further followed by curing by radical polymerization.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polyurethane-based material that can be suitably used as a material for dental cutting. [Background technology]

[0002] In dental treatment, one method for fabricating dental prostheses, such as inlays, onlays, crowns, bridges, and implant superstructures, is to use a dental CAD / CAM system for machining. A dental CAD / CAM system uses a computer to design dental prostheses based on three-dimensional coordinate data, and then fabricates the crown restoration using a machining machine. Various materials, including glass ceramics, zirconia, titanium, and resin, are used for machining. Resin-based dental machining materials include curable compositions containing inorganic fillers such as silica, polymerizable monomers such as methacrylate, and polymerization initiators, which are cured into block or disk shapes. Machining materials using computer systems has attracted increasing interest due to their improved workability, resulting from the reduced number of steps compared to conventional dental prosthesis fabrication methods, as well as the aesthetic and strength properties of the cured products.

[0003] Such cutting materials are mainly applied to dental crowns, and higher strength is required when used as molar crowns or bridges. Polyurethane resins are generally known to have high strength, and their use as dental materials has been considered. For example, Patent Document 1 describes a polyurethane composite material that can be suitably used as a cutting material, which is made by introducing a crosslinked structure formed by polymerization of radically polymerizable groups into the polyurethane resin, thereby taking advantage of the high strength characteristic of polyurethane resin while improving its drawback of low water resistance, and also describes a method for producing the polyurethane composite material.

[0004] That is, Patent Document 1 discloses a method for preparing a primary raw material composition containing the diol compound (a1), the non-polyaddition type radical polymerizable monomer (B), and the filler (D) using raw materials: a diol compound (a1) having one or more radical polymerizable groups; a diisocyanate compound (a2); a polymerizable monomer (B) having one or more radical polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound (a1) or the diisocyanate compound (a2) (hereinafter also referred to as a "non-polyaddition type radical polymerizable monomer"); a radical polymerization initiator (C); and a filler (D). The document describes that the diisocyanate compound (a2) is then further added to the primary raw material composition, and polyaddition is carried out to form a polyurethane component (A) having a molecular weight adjusted to 1,500 to 5,000, thereby preparing a secondary raw material composition containing the polyurethane component (A) and the non-polyaddition radically polymerizable monomer (B), and that the radically polymerizable group contained in (A) in the secondary raw material composition is then reacted with (B) to introduce a crosslinked structure, thereby producing a polyurethane composite material that is uniform throughout, has excellent strength and water resistance, and is suitable as a material for dental cutting work. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 153446 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] The polyurethane composite material described in Patent Document 1 is an excellent material having the above-mentioned characteristics. However, it has been found that when the polyurethane composite material is produced according to the method for producing the composite material described in Patent Document 1, the transparency of the resulting polyurethane composite material varies.

[0007] When a dental prosthesis is fabricated using a polyurethane composite material with unstable transparency as a dental cutting material, it becomes impossible to consistently obtain a prosthesis with excellent aesthetics. For example, when producing a crown for aesthetic restoration using a CAD / CAM system, the color tone of the dental cutting material is adjusted using pigments to reproduce the state of highly transparent enamel and relatively opaque dentin, but if the transparency of the material cannot be controlled, it becomes difficult to consistently obtain a prosthesis with excellent aesthetics. Furthermore, when a crown is fabricated using a CAD / CAM system, it becomes impossible to consistently obtain a prosthesis with excellent aesthetics. R Even when a two-layer structure is used and the color tone is adjusted so that both layers have the same color family using the same pigment, it becomes extremely difficult to manufacture such a two-layer dental cutting material.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for stably producing a polyurethane material having a crosslinked structure that is excellent not only in strength and water resistance but also in transparency. [Means for solving the problem]

[0009] The present invention solves the above-mentioned problems, and a first aspect of the present invention is a method for producing a diisocyanate compound (a2) having one or more radical polymerizable groups, a diol compound (a1) having one or more radical polymerizable groups in the molecule, and a diisocyanate compound (a2) having one or more radical polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound (a1) or the diisocyanate compound (a2). It consists of compounds with a vapor pressure of 0.001 to 1.60 Pa at 25°C. A non-polyaddition radical polymerizable monomer (B); and a radical polymerization initiator (C) are used as raw materials, a first raw material composition preparation step of preparing a first raw material composition containing the diol compound (a1) and the non-polyaddition-type radically polymerizable monomer (B) and optionally containing the radical polymerization initiator (C); a secondary raw material composition preparation step of mixing the primary raw material composition with the diisocyanate compound (a2) and polyaddition-forming the diisocyanate compound (a2) to form a polyurethane component (A) having a number average molecular weight of 1,500 to 10,000 and having a radically polymerizable group in the molecule, and, if the primary raw material composition does not contain the radical polymerization initiator (C), adding the radical polymerization initiator (C) to prepare a secondary raw material composition which contains the polyurethane component (A), the non-polyaddition-type radically polymerizable monomer (B), and the radical polymerization initiator (C) and which may contain unreacted diol compound (a1) and / or unreacted diisocyanate compound (a2); The polyurethane component (A) and the non-polyaddition radically polymerizable monomer (B) in the secondary raw material composition are reacted with a radical polymerization initiator (C). Using Polymerization and curing process in which radical polymerization is carried out to harden the material; A method for producing a polyurethane-based material having a crosslinked structure by comprising: Before carrying out the second raw material composition preparation step, , normal pressure, absolute humidity 6.0 (g / m 3 ) by keeping it in a dehumidifying dryer kept below a drying step of dehydrating the primary raw material composition to reduce the amount of water contained in the primary raw material composition to 20,000 ppm or less based on the total mass of the liquid components of the primary raw material composition, The method for producing the polyurethane material is characterized in that:

[0010] In the manufacturing method of the above embodiment (hereinafter also referred to as the "manufacturing method of the present invention"), it is preferable that the raw material further contains a filler (D), and that a primary raw material composition further containing the filler (D) is prepared in the primary raw material composition preparation step.

[0012] Furthermore, in the preferred embodiment, the primary raw material composition is maintained in the dehumidifying dryer by placing the primary raw material composition in an open container, and (1) controlling the mass of the primary raw material composition, which is the object to be treated, to the external air contact area: s (cm 2 ) ratio: s / w( cm 2 / g ) is 0.30( cm 2 / g It is preferable to carry out the process by (1) leaving the mixture to stand in a state where the temperature is equal to or higher than (2), or by (3) stirring the mixture. [Effects of the Invention]

[0014] According to the present invention, it is possible to efficiently produce a polyurethane composite material that is excellent not only in strength and water resistance but also in transparency and can be suitably used as a material for dental cutting work. DETAILED DESCRIPTION OF THE INVENTION

[0015] In order to solve the above-mentioned problems, the present inventors investigated the cause of the decrease in transparency. Generally, isocyanate reacts with alcohol to form urethane. However, it is known that a side reaction occurs in which the isocyanate reacts with water to decarboxylate, producing an amine, which then reacts with the isocyanate to form urea. Urea is more crystalline than urethane, and its formation can reduce transparency. Therefore, in the manufacturing method described in Patent Document 1, depending on the amount of water mixed in up to the secondary raw material composition preparation step to obtain the secondary raw material composition, urea is generated during polyaddition, which is thought to reduce the transparency of the resulting cured product.

[0016] The present inventors therefore conceived the idea of ​​preventing a decrease in the transparency of the resulting polyurethane composite material by controlling the water content of the urea raw material, and conducted research. As a result, they discovered that the incorporation of moisture from the environment is unavoidable during the process of obtaining the primary raw material composition, that the primary raw material composition obtained can be dried (moisture removal) effectively by using a specific method, and that by keeping the water content of the primary raw material composition matrix component at 20,000 ppm or less, the transparency of the final cured product can be stabilized. These effects are also observed in polyurethane materials that do not contain fillers in the raw materials and are not composited with fillers, leading to the completion of the present invention. The manufacturing method of the present invention is described in detail below.

[0017] In this specification, unless otherwise specified, the expression "x to y" using numerical values ​​x and y means "greater than or equal to x and less than or equal to y." In such an expression, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x. Furthermore, in this specification, the term "(meth)acrylic" means both "acrylic" and "methacrylic."

[0018] 1. Manufacturing method of the present invention The manufacturing method of the present invention is essentially an improvement over the manufacturing method described in Patent Document 1. As such, while the manufacturing method of the present invention includes the same steps as Patent Document 1, namely, a primary raw material composition preparation step, a secondary raw material composition preparation step, and a polymerization / curing step, it differs in the following key features: (1) it does not require the use of a filler as a raw material; (2) it further includes a drying step, prior to the secondary raw material composition preparation step, in which the primary raw material composition is dehydrated to reduce the water content in the primary raw material composition to 20,000 ppm or less based on the total mass of the liquid components of the primary raw material composition; and (3) the allowable range of the number-average molecular weight of the polyurethane component (A) is changed due to these differences. Apart from these key features, the manufacturing method of the present invention is essentially the same as the manufacturing method described in Patent Document 1. However, including these features, the various raw materials and steps used in the manufacturing method of the present invention will be described below.

[0019] 2. Regarding raw materials 2-1. Radical polymerizable diol compound (a1) The radically polymerizable diol compound (a1) is a compound that serves as a raw material for forming the radically polymerizable polyurethane component (A). The two hydroxyl groups of the radically polymerizable diol compound (a1) and the isocyanate groups of the diisocyanate compound (a2), which is the other polyurethane precursor component, undergo a polyaddition reaction in the secondary raw material composition preparation step, thereby forming the radically polymerizable polyurethane component (A).

[0020] The radically polymerizable diol compound (a1) can be any compound having at least one radically polymerizable group and two hydroxyl groups in the molecule, without any particular limitation. Here, the radically polymerizable group refers to a functional group that reacts with an initiator that generates radicals and polymerizes, specifically, a group having a radically polymerizable carbon-carbon double bond, such as a vinyl group, a (meth)acrylate group, or a styryl group.

[0021] The diol compound contains radically polymerizable groups, which are introduced into the main chain of the polyurethane molecule formed by the polyaddition reaction. Furthermore, during the radical polymerization process in the polymerization and curing process, radically polymerizable groups within the radically polymerizable polyurethane component (A) react with each other, or with the radically polymerizable groups of the non-polyaddition radically polymerizable monomer (B), forming bonds to form crosslinks. This improves the water resistance of the cured polyurethane material.

[0022] From the viewpoint of the strength and water resistance of the polyurethane material product, the number of radically polymerizable groups contained in the molecule of the radically polymerizable diol compound (a1) is preferably 1 to 4, and particularly preferably 1 to 2. When the number of radically polymerizable groups is 4 or less, it becomes easier to suppress shrinkage of the cured body formed during the radical polymerization reaction.

[0023] Examples of compounds that can be suitably used as the radically polymerizable diol compound (a1) include trimethylolpropane mono(meth)acrylate, glycerol mono(meth)acrylate, erythritol di(meth)acrylate, pentaerythritol di(meth)acrylate, and ring-opened products of ethylene glycol diglycidyl ether with acids ((meth)acrylic acid and vinylbenzoic acid). These can be used alone or in combination of different types.

[0024] 2-2. Diisocyanate compound (a2) The diisocyanate compound (a2) is the other polyurethane precursor component for forming the radically polymerizable polyurethane component (A), and any known compound having two isocyanate groups in one molecule can be used without any particular limitation.

[0025] Examples of compounds that can be suitably used as the diisocyanate compound (a2) include 1,3-bis(2-isocyanato-2-propyl)benzene, 2,2-bis(4-isocyanatophenyl)hexafluoropropane, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4'-methylenediphenyldiisocyanate, 3,3'-dichloro-4,4'-diisocyanatobiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, diisocyanato-4,4'-diisocyanato ... Examples include cyclohexylmethane 4,4'-diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, norbornane diisocyanate, isophorone diisocyanate, 1,5-diisocyanatonaphthalene, 1,3-phenylene diisocyanate, trimethylhexamethylene diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, and m-xylylene diisocyanate.

[0026] Among these, the diisocyanate compound (a2) is preferably a diisocyanate compound (a2) having a phenyl group in the molecule from the viewpoint of the fluidity of the resulting secondary raw material composition and the strength of the resulting polyurethane composite material.

[0027] The amount of diisocyanate compound (a2) used relative to radically polymerizable diol compound (a1) in the secondary raw material composition preparation step is not particularly limited as long as it is about 1 mol / mol in terms of molar ratio [amount of diisocyanate compound (a2) used / amount of radically polymerizable diol compound (a1) used], but is generally preferably about 0.9 to 1.2 mol / mol. Note that in the secondary raw material composition preparation step to obtain the secondary raw material composition, the molar ratio is preferably 1.0 to 1.1 mol / mol from the viewpoint of quantitatively reacting the radically polymerizable diol compound (a1) with the diisocyanate compound (a2) to form the radically polymerizable polyurethane component (A) and minimizing unreacted materials.

[0028] 2-3. Radical polymerizable polyurethane component (A) The radically polymerizable polyurethane component (A) is a component formed by a polyaddition reaction between a radically polymerizable diol compound (a1) and a diisocyanate compound (a2) in the secondary raw material composition preparation step, and has a number average molecular weight of 1500 to 10000 and contains a radically polymerizable group in the molecule. The structure of the radically polymerizable polyurethane component (A) is almost uniquely determined by the radically polymerizable diol compound (a1) used in the step of obtaining the primary raw material composition and the diisocyanate compound (a2) used in the secondary raw material composition preparation step.

[0029] The radically polymerizable polyurethane component (A) is a component that constitutes the final polyurethane material by radical polymerization with the non-polyaddition-type radically polymerizable monomer (B) under the catalytic action of the radical polymerization initiator (C). When a polyurethane composite material is produced using a filler (D) as a raw material, the radically polymerizable polyurethane component (A) also constitutes the polyurethane resin matrix therein. Therefore, in this case, the remaining components of the secondary raw material composition excluding the filler (D)—in other words, the components primarily comprising the radically polymerizable polyurethane component (A), the non-polyaddition-type radically polymerizable monomer (B), and the radical polymerization initiator (C)—can also be referred to as the matrix raw material composition. Furthermore, when the secondary raw material composition further contains components other than components A to D, if these other components dissolve in the radically polymerizable polyurethane component (A) and / or the non-polyaddition-type radically polymerizable monomer (B), these other components also constitute the matrix raw material composition.

[0030] The number average molecular weight of the radically polymerizable polyurethane component (A) contained in the secondary raw material composition may be in the range of 1500 to 10000. The radically polymerizable polyurethane component (A) in the production method described in Patent Document 1 must have a number average molecular weight controlled within the range of 1500 to 5000, the upper limit of which is determined primarily from the perspective of moldability, but the present invention does not require the inclusion of a filler, and in that case (when the secondary raw material composition is a matrix raw material composition), moldability is also improved, so the upper limit is broadened.

[0031] The number-average molecular weight of the radically polymerizable polyurethane component (A) has almost no effect on the transparency of the final polyurethane composite material, but the number-average molecular weight itself is affected by the amount of water in the primary raw material composition. In other words, in the polyaddition reaction, water reacts with an equivalent amount of isocyanate, decarboxylates to form an amine, and then further reacts with an equivalent amount of isocyanate to form urea, so the number-average molecular weight is affected by the water content in the primary raw material composition. Therefore, in relation to the water content, a lower limit of the number-average molecular weight of 2000, particularly 2500, is preferred from the viewpoint of facilitating the production of a polyurethane (composite) material with stable transparency.

[0032] The number-average molecular weight of the radically polymerizable polyurethane component (A) refers to the polystyrene-equivalent number-average molecular weight determined by gel permeation chromatography (GPC). The number-average molecular weight of the radically polymerizable polyurethane component (A) in the secondary raw material composition can be determined by adding a solvent such as tetrahydrofuran (THF) or dimethyl sulfoxide (DMSO) to the radically polymerizable raw material composition as needed, removing insoluble components such as the filler (D) by filtration or centrifugation, and then performing GPC measurement on the resulting solution (i.e., the matrix raw material composition or a solution consisting of a mixture of the matrix raw material composition and an optional solvent).

[0033] 2-4. Non-polyaddition radical polymerizable monomer (B) The non-polyaddition radically polymerizable monomer (B) is a compound that has at least one radically polymerizable group in its molecule and does not undergo polyaddition with either the radically polymerizable diol compound (a1) or the diisocyanate compound (a2). Here, "does not undergo polyaddition with either the radically polymerizable diol compound (a1) or the diisocyanate compound (a2)" means that the monomer does not contain both a group that undergoes polyaddition with the radical diol compound (a1) and a group that undergoes polyaddition with the diisocyanate compound (a2). Specifically, this means that the monomer does not contain a hydroxyl group, an amino group, a carboxyl group, an isocyanate group, or a mercapto group. Among these functional groups, the group that can undergo polyaddition with the radically polymerizable diol compound (a1) is an isocyanate group, and the group that can undergo polyaddition with the diisocyanate compound (a2) is a hydroxyl group, an amino group, a carboxyl group, or a mercapto group. Therefore, the non-polyaddition radically polymerizable monomer (B) does not contain a hydroxyl group, an amino group, a carboxy group, an isocyanate group, or a mercapto group in the molecule. Furthermore, the radically polymerizable group may be the same as the radically polymerizable group contained in the radically polymerizable diol compound (a1). Suitable radically polymerizable groups are preferably (meth)acrylate groups and / or (meth)acrylamide groups, or groups having the same molecular structure as the radically polymerizable group contained in the radically polymerizable diol compound (a1). From the viewpoint of ease of crosslink formation, the number of radically polymerizable groups contained in the molecule of the non-polyaddition radically polymerizable monomer (B) is preferably 2 to 6, more preferably 2 to 4. By having two or more radically polymerizable groups, the crosslink density can be increased, making it easier to obtain a cured product with sufficient strength. Furthermore, by having six or fewer radically polymerizable groups, it is easier to suppress shrinkage during curing. Furthermore, the non-polyaddition radically polymerizable monomer (B) is preferably liquid at room temperature (i.e., 25°C).

[0034] Used in the manufacturing method of the present invention The vapor pressure of the non-polyaddition radical polymerizable monomer (B) is 25℃ At 0.001 to 1.60 Pa。 If the vapor pressure is higher than 1.60 Pa, particularly if the drying process is prolonged, the polymerizable monomer (B) will volatilize, increasing the filling rate of the resulting secondary raw material composition, worsening operability, and making it difficult to obtain a cured product with uniform transparency. As will be described later, the drying process is preferably carried out at room temperature (for example, normal room temperature of 15 to 35°C) to 80°C, so a non-polyaddition radically polymerizable monomer (B) with a vapor pressure at 25°C of 0.001 to 1.60 Pa is used. Examples of the non-polyaddition radically polymerizable monomer (B) having such a vapor pressure include diethylene glycol diacrylate (vapor pressure: 0.268 Pa), diethylene glycol dimethacrylate (vapor pressure: 0.0364 Pa), triethylene glycol diacrylate (vapor pressure: 0.0127 Pa), triethylene glycol dimethacrylate (vapor pressure: 0.0159 Pa), trimethylolpropane acrylate (vapor pressure: 7.03 × 10 -4 Pa), trimethylolpropane methacrylate (vapor pressure: 3.22 × 10 -5 Pa), pentaerythritol acrylate (vapor pressure: 3.55 × 10 -6 Pa), pentaerythritol methacrylate (vapor pressure: 6.32 × 10 -8 Pa), ditrimethylolpropane acrylate (vapor pressure: 1.28 x 10 -9 Pa), ditrimethylolpropane methacrylate (vapor pressure: 1.69 × 10 -11 Pa), dipentaerythritol acrylate (vapor pressure: 3.47 x 10 -14 Pa), dipentaerythritol methacrylate (vapor pressure: 4.09 × 10 -17 Among these, diethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate are particularly preferred.

[0035] The content of the non-polyaddition-type radical polymerizable monomer (B) in the secondary raw material composition is expressed by the following formula (1), where Ar is the content of the radical polymerizable polyurethane component (A), Br is the content of the non-polyaddition-type polymerizable monomer (B), a1r is the content of the radical polymerizable diol compound (a1), and a2r is the content of the diisocyanate compound (a2), respectively: Rr=100×Br / 〔a1r+a2r+Ar+Br〕 It is preferable that the polymerizable monomer blending ratio Rr defined by: is an amount of 20% by mass or more and less than 80% by mass.

[0036] By setting the polymerizable monomer blending ratio Rr to 80% by mass or less, the content of the radically polymerizable polyurethane component (A), which contributes to improving strength, is increased, resulting in a polyurethane-based composite material with sufficient strength. Furthermore, by setting the polymerizable monomer blending ratio Rr to 20% by mass or more, the homogeneity of the secondary raw material composition is increased, resulting in suppressing uneven curing of the resulting cured product and obtaining a cured product with excellent uniformity.

[0037] 2-5. Radical polymerization initiator (C) The radical polymerization initiator (C) may be a thermal radical polymerization initiator and / or a photoradical polymerization initiator. However, a thermal radical polymerization initiator is preferred because it allows for uniform curing throughout the secondary raw material composition. From the standpoints of ease of handling and stability, a thermal polymerization initiator with a 10-hour half-life temperature in the range of 40°C to 150°C is preferred, with a 10-hour half-life temperature in the range of 70°C to 100°C being particularly preferred. The 10-hour half-life temperature is the temperature at which the amount of thermal polymerization initiator present decreases to half of its initial amount after 10 hours from the initial time point, and is used as an index of the reactivity of the thermal polymerization initiator. Specific examples of suitable thermal radical polymerization initiators include peroxide initiators such as benzoyl peroxide and tert-butyl peroxylaurate, and azo-based initiators such as azobisbutyronitrile and azobis(2,4-dimethylvaleronitrile). These thermal polymerization initiators may be used alone or in combination of two or more.

[0038] The amount of radical polymerization initiator (C) used may be determined appropriately depending on the type of initiator, but is generally preferably in the range of 0.005% by mass to 2.0% by mass, and more preferably in the range of 0.01% by mass to 1.0% by mass, based on the mass of the matrix raw material composition.

[0039] 2-6. Filler (D) The filler (D) is used as a raw material as needed, and has the function of improving the physical properties such as mechanical strength, abrasion resistance, and water resistance of the polyurethane composite material by dispersing it in the polyurethane resin matrix and forming a composite with the polyurethane resin matrix.

[0040] As the filler (D), inorganic fillers such as silica, alumina, titania, zirconia, or composite oxides thereof, glass, etc. are preferably used. Specific examples of such inorganic fillers include spherical or irregularly shaped particles such as amorphous silica, silica-zirconia, silica-titania, silica-titania-zirconia, quartz, and alumina. When the polyurethane composite material produced by the production method of the present invention is used as a dental material, silica, titania, zirconia, or composite oxides thereof are preferably used as the filler (D), with silica or composite oxides thereof being particularly preferred. These inorganic fillers are unlikely to dissolve in the oral cavity environment, and the refractive index difference with the polyurethane resin matrix can be easily adjusted, making it easy to control transparency and aesthetics.

[0041] The shape of the filler (D) is not particularly limited and can be appropriately selected depending on the intended use of the polyurethane composite material. However, from the viewpoint of obtaining a polyurethane composite material that is particularly excellent in abrasion resistance, surface smoothness, and gloss durability, for example, a (nearly) spherical shape is preferred.

[0042] The average particle size of the filler (D) is preferably 0.001 μm to 100 μm, more preferably 0.01 μm to 10 μm, from the viewpoints of abrasion resistance, surface smoothness, and gloss durability. Furthermore, it is preferable to use fillers (D) having multiple particle sizes, since this facilitates increasing the content of the filler (D) in the polyurethane composite material. Specifically, it is preferable to combine particle sizes of 0.001 μm to 0.1 μm with particle sizes of 0.1 μm to 100 μm, and more preferably to combine particle sizes of 0.01 μm to 0.1 μm with particle sizes of 0.1 μm to 10 μm.

[0043] The average particle diameter of the inorganic filler can be determined, for example, by taking a photograph of the powder at a magnification of 5,000 to 100,000 times using a scanning electron microscope (Philips, "XL-30S"), processing the photographed image using image analysis software ("IP-1000PC", product name; manufactured by Asahi Kasei Engineering Corporation), measuring the number n (30 or more) of particles observed within a unit field of view of the photograph and the primary particle diameter (maximum diameter) Xi, and calculating the average particle diameter based on the measured values ​​using the following formula (2): It can be obtained by calculating the number average primary particle diameter using TIFF0007789312000001.tif3071.

[0044] It is preferable to use a filler (D) that has been surface-treated in order to improve compatibility with the polyurethane resin matrix and to improve the mechanical strength and water resistance of the polyurethane composite material.

[0045] The amount of filler (D) used may be determined appropriately depending on the physical properties such as the strength of the target polyurethane composite material, but from the viewpoint of increasing the strength of the polyurethane composite material, the amount is preferably 60 to 85 mass%, more preferably 65 to 80 mass%, expressed in mass% based on the mass of the secondary raw material composition (hereinafter sometimes simply referred to as "filling rate"). Furthermore, when the polyurethane composite material produced by the production method for a polyurethane composite material of this embodiment is used as a dental cutting material, the filling rate is more preferably 65 to 80 mass%, even more preferably 70 to 80 mass%.

[0046] 2-7. Other additives In addition to the essential components described above, various other additives may be blended into the primary raw material composition, the dried primary raw material composition, or the secondary raw material composition. Examples of the various additives include polymerization inhibitors, fluorescent agents, ultraviolet absorbers, antioxidants, pigments, antibacterial agents, and X-ray contrast agents. The amounts of these additives may be determined appropriately depending on the desired purpose.

[0047] 3.About each process The manufacturing method of the present invention includes a primary raw material composition preparation step, a drying step, a secondary raw material composition preparation step, and a polymerization and curing step. Each step will be described in detail below.

[0048] 3-1. Primary raw material composition preparation process In the primary raw material composition preparation step, a primary raw material composition is prepared containing a radically polymerizable diol compound (a1), a non-polyaddition-type radically polymerizable monomer (B), and a radical polymerization initiator (C). When a filler (D) is used, a primary raw material composition is prepared that further contains the filler (D).

[0049] The blending amounts of each component are determined as follows: The composition of the primary raw material composition is determined based on the composition of the secondary raw material composition to be obtained. Specifically, assuming that equimolar amounts of radically polymerizable diol compound (a1) and diisocyanate compound (a2) are quantitatively polyaddition-reacted to produce the radically polymerizable polyurethane component (A), the amounts of radically polymerizable diol compound (a1) and diisocyanate compound (a2) used in the secondary raw material composition preparation step are determined so that the molar ratio [amount of diisocyanate compound (a2) used / amount of radically polymerizable diol compound (a1) used] is approximately 1 mol / mole, typically about 0.9 to 1.2 mol / mole, preferably 1.0 to 1.1 mol / mole. The amounts of (a1) and (B) in the primary raw material composition and the amount of (a2) used in the secondary raw material composition preparation step are determined accordingly. The amounts of (A), (B), remaining (a1), and remaining (a2) in the secondary raw material composition are automatically determined based on these amounts. Furthermore, the amounts of (C) and (D), which are used if necessary, may be selected based on the above-mentioned criteria.

[0050] The primary raw material composition may be prepared by mixing all of the components constituting the primary raw material composition at once, or by preparing a mixture by mixing some of the components constituting the primary raw material composition and then adding and mixing the remaining components constituting the primary raw material composition. The mixing method for mixing the components in the preparation of the primary raw material composition is not particularly limited, and methods using a magnetic stirrer, a mortar and pestle mixer, a planetary mixer, a trimix, a centrifugal mixer, etc. are appropriately used. Furthermore, because it is easier to uniformly disperse the filler (D), it is preferable to first mix the radically polymerizable diol compound (a1) and the non-polyaddition-type radically polymerizable monomer (B) to prepare a mixed composition, and then add the filler (D) to this mixed composition and mix it to prepare the primary raw material composition. Furthermore, it is preferable to add other additives to the primary raw material composition because it is easier to suppress side reactions and facilitate dispersion. Furthermore, if the components are mixed under vacuum conditions, the progress of radical polymerization will deteriorate operability, making it difficult to uniformly disperse the components, and ultimately making it difficult to obtain a uniform cured product. Therefore, mixing is preferably carried out under normal pressure or pressurized conditions. The primary raw material composition prepared in this manner is preferably subjected to a degassing treatment to remove any air bubbles contained therein. As a degassing method, a known method carried out under normal pressure or pressurized conditions can be used, and methods such as pressurized degassing and centrifugal degassing can be used as desired.

[0051] The primary raw material composition may further contain, as other additives, a catalyst that promotes the polyaddition reaction, if necessary, but it is not necessary to contain a catalyst that promotes the polyaddition reaction. Examples of catalysts that promote the polyaddition reaction include tin octoate and dibutyltin diacetate.

[0052] 3-2.Drying process In the drying step, prior to the secondary raw composition preparation step, the primary raw composition is dehydrated to reduce the water content of the primary raw composition to 20,000 ppm or less based on the total mass of the liquid components of the primary raw composition. Here, the water content refers to the water content measured by Karl Fischer analysis of the dried primary raw composition (after drying). Note that the liquid components of the primary raw composition refer to the entire primary raw composition if the primary raw composition does not contain filler (D), or to the components excluding filler (D) if the primary raw composition contains filler (D). Furthermore, when measuring the water content, the dried primary raw composition may be used as a measurement sample as is, or the measurement sample may be prepared by diluting the dried primary raw composition with an inert solvent (e.g., a dehydrating solvent) with a low water content and a known amount. the latter In this case, the dried primary raw material composition matrix component in the sample (liquid component) Included in Based on the total mass of the liquid component Moisture content (mass ppm): M is the measured moisture content of the sample (mass ppm): M s, mass of the measurement sample: Ws, moisture content of the dry primary raw material composition in the measurement sample: Mp , the water content of the dilution solvent (mass ppm): Ma, the mass of the dry primary raw material composition in the measurement sample: Wp, the mass of the dilution solvent in the measurement sample: Wa, and In the dry primary raw material composition Filling rate of filler : Cp (mass%) Then, Ms×Ws=Ms×(Wa+Wp)=(Ma×Wa)+(Mp×Wp), and M=Mp×100 / (100-Cp). From the above, the following equation (3): M ={M s ×(Wp+Wa)-(Ma×Wa)} / (W p) ×100 / (100-Cp) It can be calculated as follows.

[0053] In the manufacturing method of the present invention, the transparency of the final cured product is stabilized by keeping the water content of the dried primary raw material composition (based on the total mass of the liquid components) at 20,000 ppm or less, more preferably 10,000 ppm or less. The reason why the transparency of the polyurethane composite material is stabilized is not necessarily clear, and the present invention is not bound by any theory, but it is speculated that a water content of 20,000 ppm prevents urea from being produced in the polyaddition step, or that the amount is not within a range that would affect transparency.

[0054] The dehydration method in the drying process is as follows: heat When a polymerization initiator is contained, the process is preferably carried out at 80°C or less from the viewpoint of preventing unintended progress of radical polymerization. Since there is no particular advantage to cooling, the process is preferably carried out at room temperature (for example, a normal room temperature of 15 to 35°C) to 80°C. Furthermore, from the viewpoint of efficient drying and shortening the drying process time, the desiccation process in the production method of the present invention is carried out under normal pressure in a low-humidity atmosphere with an absolute humidity of 0.1 (g / m 3 ) or more 6.0 (g / m 3 ) or less, preferably 0.1 (g / m 3 ) or more 4.0 (g / m 3 ) or less, and take measures to increase the surface area in contact with the outside air, such as stirring, as necessary. place In addition, when the primary raw material composition contains a filler (D) and has a high viscosity, in order to increase the dehydration efficiency, the primary raw material composition is placed in an open container, and (1) the surface area of ​​contact with the outside air relative to the mass of the primary raw material composition, which is the object to be treated: w (g): s (cm 2 ) ratio (also called "dry specific surface area"): s / w( cm 2 / g ) is 0.30( cm 2 / g ) or more, or (2) placing the mixture in the atmosphere while stirring. In the above (1), from the viewpoint of efficiency, it is preferable to set the specific surface area when dried: s / w( cm 2 / g) is 0.50cm 2 / g or more, especially 1.00cm 2 / g or more. cm 2 / g ) is set at 5.00 cm from the practical viewpoint of productivity etc. 2 / g or less. In this case, the treatment time is usually selected from the range of 15 to 168 hours, preferably from the range of 40 to 100 hours. The low humidity atmosphere described above can be obtained, for example, by adjusting the atmosphere inside a drying device having a humidity control function so as to satisfy the above conditions.

[0055] The stirring in (2) can be suitably carried out using a magnetic stirrer, a mortar and pestle mixer, a planetary mixer, a trimix, a centrifugal mixer, or the like. The drying time (dehydration treatment time) is preferably 1 to 9 hours, particularly 2 to 8 hours. The method (2) can be suitably employed for a primary raw material composition having a viscosity at 25°C in the range of 100 Pa·s to 100,000 Pa·s, particularly 1,000 Pa·s to 10,000 Pa·s.

[0056] 3-3. Secondary raw material composition preparation process In the secondary raw material composition preparation step, the dry primary raw material composition is mixed with the diisocyanate compound (a2) to polyaddition react the diol compound (a1) with the diisocyanate compound (a2) to form a polyurethane component (A) having a radical polymerizable group, thereby preparing a secondary raw material composition. The secondary raw material composition contains the radical polymerizable polyurethane component (A), the non-polyaddition-type radical polymerizable monomer (B), and a radical polymerization initiator (C), and may contain unreacted radical polymerizable diol compound (a1) and / or unreacted diisocyanate compound (a2). When a filler (D) is used, a secondary raw material composition is prepared that further contains the filler (D). The polyaddition reaction is initiated simultaneously with mixing the dry primary raw material composition with the diisocyanate compound (a2), or by heating the mixture as needed after mixing the dry primary raw material composition with the diisocyanate compound (a2). The polyaddition reaction is carried out until at least one of the radically polymerizable diol compound (a1) and the diisocyanate compound (a2) is substantially consumed by the polyaddition reaction; in other words, until the degree of progress of the polyaddition reaction approaches its maximum value (saturation value). The mixing method for mixing the components in preparing the secondary raw material composition is not particularly limited, and methods using a magnetic stirrer, a mortar and pestle mixer, a planetary mixer, a trimix, a centrifugal mixer, or the like may be appropriately used. Furthermore, mixing the components for a long period under vacuum conditions may undesirably cause unintended radical polymerization, as in the drying process, and therefore mixing is preferably carried out under normal or pressurized conditions. In addition, in the secondary raw material composition preparation process, if the water content in the secondary raw material composition increases, the effect of the preceding drying process is negated; therefore, the mixing is preferably carried out in a dry atmosphere (low humidity atmosphere).

[0057] 3-4.Polymerization / curing process The polymerization and curing process is carried out after the secondary raw material composition preparation process is completed. In the polymerization and curing process, the radical polymerization initiator (C) contained in the secondary raw material composition is activated to cause radical polymerization, thereby curing the secondary raw material composition. This results in a cured product made of a polyurethane-based material, or a polyurethane-based composite material if a filler (D) is included. When a thermal radical polymerization initiator is used as the radical polymerization initiator (C), radical polymerization proceeds by heating the secondary raw material composition. When a photoradical polymerization initiator is used as the radical polymerization initiator (C), radical polymerization proceeds by irradiating the secondary raw material composition with light that activates it.

[0058] Because radical polymerization generates heat due to reaction heat, it is preferable to control the heating temperature (curing temperature) when using a thermal radical polymerization initiator as the radical polymerization initiator (C). In this case, the heating temperature is preferably controlled so as not to exceed 150°C. It is particularly preferable to control the heating temperature within the range of −10°C to +25°C of the 10-hour half-life temperature of the thermal radical polymerization initiator, i.e., a temperature 10°C lower than the 10-hour half-life temperature T (lower limit temperature L) to 25°C higher than the 10-hour half-life temperature T (upper limit temperature H), where T (°C) is the 10-hour half-life temperature. Setting the heating temperature above the lower limit temperature L not only sufficiently increases the radical polymerization rate but also facilitates the prevention of unintended coloration of the cured product. Furthermore, setting the heating temperature below the upper limit temperature H prevents excessive consumption of radically polymerizable groups present in the reaction system and suppresses rapid radical polymerization. By controlling the heating temperature within the above-mentioned temperature range, polymerization and curing can proceed at an industrially acceptable reaction rate, preventing distortion and cracking in the cured product due to rapid reaction progress, and significantly reducing deterioration of the non-polyaddition radically polymerizable monomer (B). Furthermore, when radically polymerizing by heating, the secondary raw material composition may be pressurized during radical polymerization to prevent voids due to bubbles from forming in the cured product. There are no limitations on the pressurization method, and mechanical pressurization or pressurization with a gas such as nitrogen may be used.

[0059] 4. Uses of polyurethane materials The manufacturing method of the present invention makes it possible to stably obtain a polyurethane-based material having excellent transparency. The excellent transparency of the polyurethane-based material makes it possible to freely adjust the desired transparency by blending pigments and the like.

[0060] The polyurethane (composite) material obtained by the manufacturing method of the present invention using the filler (D) also has the above-mentioned characteristics and can be particularly suitably used as a material for dental cutting. The transparency in such applications can be suitably adjusted, for example, by controlling the amount of white pigments such as zinc oxide and titanium oxide added to make the material opaque. The transparency can be measured by the contrast ratio: Y b / Y w The contrast ratio is often expressed as an index of spectral reflectance (Y) against a black background measured using a color difference meter for a 1.0 mm thick sample. b ) and spectral reflectance on a white background (Y w ) ratio: Y b / Y w The whiteness: W is the value determined by measuring the L * value, a * value and b * Based on the values, the following formula (4): W=100-{(100-L * ) 2 +(a * ) 2 +(b * ) 2} 1 / 2 It is calculated by:

[0061] The contrast ratio of a general dental cutting material is preferably in the range of 0.1 to 0.6, more preferably 0.2 to 0.5. This allows for adjustment within the range to express two layers, transparent enamel and relatively opaque dentin, from a single hardenable composition, resulting in a dental cutting material with excellent aesthetics. Therefore, a contrast ratio of 0.05 to 0.55, more preferably 0.05 to 0.45, without adding pigments, allows for easy adjustment to any desired transparency. Furthermore, a whiteness of 30 to 65, more preferably 35 to 60, allows for restoration of an appearance similar to that of natural teeth. Therefore, a whiteness of 30 to 60, more preferably 30 to 55, without adding pigments, allows for easy adjustment to any desired transparency. Furthermore, polyurethane (composite) materials can be subjected to post-treatments and processing, such as heat treatment to relieve residual stress, shape modification by cutting, and polishing, as needed, and then attached with fixtures such as pins for holding them in a CAD / CAM system, to obtain dental cutting materials. [Example]

[0062] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0063] 1. Raw materials The components used in each of the examples and comparative examples and their abbreviations are shown below.

[0064] (1) Radical polymerizable diol compound (a1) GLM: Glycerol monomethacrylate (vapor pressure at 25°C: 0.00724 Pa) (2) Diisocyanate compound (a2) XDI: m-xylylene diisocyanate (3) Non-polyaddition radical polymerizable monomer (B) TEGDMA: Triethylene glycol dimethacrylate (vapor pressure at 25°C: 0.0159 Pa) EGDMA: Ethylene glycol dimethacrylate (vapor pressure 1.61 Pa at 25°C) (4) Filler (D) F1: Silica-zirconia (average particle size: 0.4 μm, surface treated with 3-(trimethoxysilyl)propyl methacrylate) F2: Silica-titania (average particle size: 0.08 μm, surface treated with 3-(trimethoxysilyl)propyl methacrylate) (5) Radical polymerization initiator (C) PBL: t-butyl peroxylaurate (10-hour half-life temperature 98°C) 2. Manufacturing method of polyurethane-based materials Examples of the manufacturing method of the present invention will be described below together with comparative examples.

[0065] Example 1 (1) Primary raw material composition preparation process First, a mixture of GLM (10.4 parts by mass), a non-polyaddition radically polymerizable diol compound (a1), TEGDMA (5.8 parts by mass), and PBL (0.1 parts by mass), a radical polymerization initiator (C), was prepared. Next, fillers (D) F1 (49.0 parts by mass) and F2 (20.9 parts by mass) were added to the mixture and kneaded to prepare a primary raw material composition.

[0066] (2) Drying process The obtained primary raw material composition (10.0 Mass part ) was placed in an automatic dry desiccator, Drymax DMX-400 (manufactured by AS ONE) (temperature inside the desiccator: 25°C, humidity: 2% = absolute humidity: 0.5 (g / m 3 The sample was placed in a 20cm x 20cm x 1.1cm container and left to stand for 96 hours. The specific surface area was 0.50cm. 2 After drying, the mixture was kneaded for 1 minute to homogenize the moisture content, thereby preparing a dry primary raw material composition.

[0067] (3) Moisture content evaluation of dried primary raw material composition The moisture content of the dried primary raw material composition was measured. The evaluation method and results are shown below.

[0068] The resulting dry primary raw material composition was suspended in Aquamicron Dehydrating Solvent OLII (manufactured by Mitsubishi Chemical Corporation), a dehydrating solvent, to prepare a concentration of Aquamicron OLII / dry primary raw material composition = 1.25 g / g, which was used as a measurement sample. Next, the moisture content of the measurement sample and Aquamicron OLII was measured using an 870 Titrino Plus (volumetric KF moisture meter) (manufactured by Metrohm International Headquarters), a volumetric titration moisture measurement device, to obtain actual values ​​for each. The moisture content was then calculated using the respective measured values ​​using the above formula (3), and the moisture content in the dry primary raw material composition matrix component was found to be 15,600 ppm.

[0069] (4) Secondary raw material composition preparation process The resulting dried primary raw material composition (8.0 Mass part ), a diisocyanate compound (a2) XDI (0.91 Mass part ) was added and kneaded, and then the mixture was left to stand in an incubator at 60°C for 24 hours to carry out a polyaddition reaction, forming a radically polymerizable polyurethane component (A) and preparing a secondary raw material composition. In the present examples, all compositions were prepared in an environment of room temperature (25°C), except for the case where the polyaddition reaction was carried out by heating to 60°C.

[0070] (5) Evaluation of secondary raw material composition The number-average molecular weight of the radically polymerizable polyurethane component (A) of the resulting secondary raw material composition was evaluated as follows. Specifically, 1 g of the resulting secondary raw material composition was weighed into a screw cap, 3.5 ml of DMSO was added, and the resulting DMSO solution was centrifuged at 10,000 rpm for 10 minutes in a centrifuge (manufactured by AS ONE Corporation). The supernatant obtained by centrifugation was then filtered through a membrane filter (pore size 20 μm, manufactured by ADVANTEC Corporation) to obtain a filtrate. This filtrate was then subjected to GPC measurement under the GPC measurement conditions shown below to determine the polystyrene-equivalent number-average molecular weight of the radically polymerizable polyurethane component (A) obtained by the polyaddition reaction. The resulting number-average molecular weight was 2,200.

[0071] [GPC measurement conditions] Measurement equipment: Advanced Polymer Chromatography (manufactured by Japan Waters) Column: ACQUITY APCTMXT45 1.7μm ACQUITY APCTMXT125 2.5μm Column temperature: 40℃ ·Developing solvent: THF (flow rate: 0.5ml / min) Detector: Photodiode array detector 254nm (PDA detector)

[0072] (6) Polymerization / curing process The obtained secondary raw material composition was poured into a mold (12 mm long x 18 mm wide x 14 mm thick) and a mold (circular with a diameter of 5 mm x 1 mm thick) and subjected to radical polymerization at 120°C for 15 hours under nitrogen pressure (0.3 MPa), to obtain a polyurethane composite material in which the filler was dispersed in a polyurethane resin matrix.

[0073] (7) Evaluation of polyurethane composite materials (cured bodies) The obtained polyurethane composite material was subjected to the following tests: bending strength, underwater bending strength, water resistance, whiteness, and contrast ratio T=(Y b / Y wThe evaluation method and results are shown below.

[0074] [Flexural strength BS d ] The resulting polyurethane composite (cured body) was cut using a mold (12 mm long x 18 mm wide x 14 mm thick) with a low-speed diamond cutter (Buehler). Five rectangular prism-shaped test specimens (approximately 1.2 mm thick x 4.0 mm wide x 14.0 mm long) were then prepared by polishing with #2000 waterproof abrasive paper. Next, a three-point bending test was performed on each test specimen using an autograph (Shimadzu Corporation), and the bending load at the maximum point was measured. The bending strength (MPa): BS was calculated from the bending load at the maximum point (N): P, the distance between supports: S, the width (measured value, mm): W, and the thickness (measured value, mm): B, using the following formula: BS=3PS / 2WB 2 The bending strength BS was calculated based on the above. The bending load at the maximum point was measured with a support distance of 12.0 mm and a crosshead speed of 1.0 mm / min. As a result, the average value of the bending strength BS of the five test pieces (Bending strength BS d ) was 300 MPa.

[0075] [Underwater bending strength BS W ] Five test pieces were prepared in the same manner as described in the [Flexural strength] section, and all test pieces were stored in ion-exchanged water at 37°C for one week. After that, the test pieces were taken out of the ion-exchanged water, and after removing the moisture adhering to the surface, a three-point bending test was carried out under the same test conditions as described in the [Flexural strength] section, and the bending load at the maximum point of the test piece after underwater storage was measured. Then, the bending strength BS of each test piece after underwater storage was calculated based on the above formula. As a result, the average value of the bending strength BS of the five test pieces after underwater storage (underwater bending strength BS w ) was 263 MPa.

[0076] [Retention rate (water resistance)] The retention rate, which is an index showing the water resistance of the hardened body, is calculated using the following formula: Retention rate (%)=100×BSW / BS d In this example, the retention rate was 88%, confirming high water resistance.

[0077] [Transparency] The polyurethane composite material (cured body) obtained using a mold (circular, 5 mm diameter x 1 mm thick) was polished with waterproof abrasive paper #2000, and then mirror-polished using an automatic polishing machine Ecomet 250 (Buehler) with alumina abrasive Baikalox 0.05CR GAMMA (Baikowski) to prepare a test piece with a thickness of 1.00 mm (±0.02 mm). The spectral reflectance of the obtained test piece was measured using a spectrophotometer SE7700 set (Nippon Denshoku Kogyo) against a black background, and the measured L * value, a * value and b * The whiteness W was calculated based on the Y value. b The contrast ratio T = (Y b / Y w As a result, the whiteness W was 53, and the Y b / Y w was 0.46.

[0078] Examples 2 to 6 Using the primary raw material composition prepared in Example 1, polyurethane composite materials were produced in the same manner as in Example 1, except that the drying time in the drying step and the specific surface area when dried (s / w) were changed as shown in Table 1. The moisture content of the dried primary raw material composition matrix component and the resulting polyurethane composite materials were evaluated in the same manner as in Example 1. The results are shown in Table 1. In the table, "↑" means "same as above."

[0079] Example 7 The primary raw material composition prepared in Example 1 was subjected to the following drying process. Dry air (temperature of dry air: 25°C, humidity: 8% = absolute humidity: 1.8 (g / m)) was dried using an air dryer AD-0001 (manufactured by AS ONE). 3 The mixture was mixed at 45°C for 3 hours using a Trimix (manufactured by Inoue Seisakusho) in which the contents of the chamber had been dried by running water. Thereafter, a polyurethane composite material was produced in the same manner as in Example 1. The moisture content of the dried primary raw material composition matrix component and the resulting polyurethane composite material were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0080] Example 8 The same procedures as in Example 1 were carried out except that the non-polyaddition radically polymerizable monomer (B) was changed from TEGDMA to EGDMA, and the drying time, specific surface area upon drying (s / w), and absolute humidity in the drying chamber were changed as shown in Table 1. The results are shown in Table 1.

[0081] Comparative Example 1 A polyurethane composite material was produced in the same manner as in Example 1, using the primary raw material composition prepared in Example 1, except that the drying step was not performed. The water content of the primary raw material composition and the resulting polyurethane composite material were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0082] Comparative Examples 2 and 3 Using the primary raw material composition prepared in Example 1, polyurethane composite materials were produced in the same manner as in Example 1, except that the dry specific surface area (s / w) and the absolute humidity inside the chamber were changed as shown in Table 1. The moisture content of the dried primary raw material composition matrix component and the resulting polyurethane composite materials were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0083] Comparative Example 4 The same procedure as in Example 1 was repeated, except that the non-polyaddition radically polymerizable monomer (B) was changed from TEGDMA to EGDMA, and the drying time and dry specific surface area (s / w) in the drying step were changed as shown in Table 1. As a result, it was found that the dried primary raw material composition was powdery after drying. Therefore, no further evaluation was performed.

[0084] Comparative Example 5 The primary raw material composition prepared in Example 1 was subjected to the following drying process. Mass part The sample was placed in a square vacuum dryer ADP-300 (Yamato Scientific) to a size of 20 cm x 20 cm x 0.5 cm and left to stand at 25°C and 100 Pa for 168 hours. The specific surface area was 1.05 cm. 2 / g. As a result, it was found that the dried primary raw material composition was solid after drying. Therefore, no further evaluation was carried out.

[0085] [Table 1]

[0086] Example 9 The primary raw material composition preparation step and drying step were carried out in the same manner as in Example 1, except that the filler (D) was not added and the dry specific surface area (s / w) was changed. The moisture content of the obtained dried primary raw material composition was calculated in the same manner as in Example 1, except that the measurement sample was prepared without adding a solvent or the like. As a result, the moisture content of the dried primary raw material composition matrix component was found to be 2000 ppm. Next, XDI (2.1 g), which is a diisocyanate compound (a2), was added to a vial containing the obtained dry primary raw material composition (2.9 g) and mixed. The mixture was then left to stand in an incubator at 60°C for 24 hours to carry out a polyaddition reaction, forming a radically polymerizable polyurethane component (A) and preparing a secondary raw material composition (secondary raw material composition preparation process). The obtained secondary raw material composition was then poured into a mold (circular with a diameter of 5 mm and a thickness of 1 mm) and subjected to radical polymerization at 120°C for 15 hours under nitrogen pressure (0.3 MPa) to obtain a polyurethane material (polymerization and curing step). The whiteness and contrast ratio T=(Y b / Y w ) was evaluated in the same manner as in Example 1. As a result, the whiteness W was 15, and the Y b / Y w was 0.02.

[0087] Examples 10 to 13 and Comparative Example 6 Polyurethane materials were produced in the same manner as in Example 9, except that the drying time in the drying step was changed as shown in Table 2. The water content of the primary raw material composition and the resulting polyurethane materials were evaluated in the same manner as in Example 9. The results are shown in Table 2.

[0088] Comparative Example 7 A polyurethane-based material was produced in the same manner as in Example 9, except that the drying step was not carried out after the primary raw material composition preparation step. The water content of the primary raw material composition and the resulting polyurethane-based material were evaluated in the same manner as in Example 9. The results are shown in Table 2.

[0089] [Table 2]

[0090] As shown in the results of Examples 9 to 13, when the moisture content of the primary raw material composition is less than 20,000 ppm, the whiteness is stable at 15 to 20 and the contrast ratio is stable at 0.02 to 0.04. On the other hand, the results of Comparative Examples 6 and 7 show that when the moisture content of the primary raw material composition is 20,000 ppm or more, the contrast ratio and whiteness increase as the moisture content increases.

Claims

1. a diol compound (a1) having one or more radically polymerizable groups; a diisocyanate compound (a2); a non-polyaddition radically polymerizable monomer (B) having one or more radically polymerizable groups in the molecule and consisting of a compound that does not undergo a polyaddition reaction with either the diol compound (a1) or the diisocyanate compound (a2), and having a vapor pressure at 25°C in the range of 0.001 to 1.60 Pa; and a radical polymerization initiator (C), a primary raw material composition preparation step of preparing a primary raw material composition containing the diol compound (a1) and the non-polyaddition-type radically polymerizable monomer (B) and optionally containing the radical polymerization initiator (C); a secondary raw material composition preparation step of mixing the primary raw material composition with the diisocyanate compound (a2) and polyadding the diisocyanate compound (a2) to form a polyurethane component (A) having a number average molecular weight of 1,500 to 10,000 and having a radically polymerizable group in the molecule, and, if the primary raw material composition does not contain the radical polymerization initiator (C), adding the radical polymerization initiator (C) to prepare a secondary raw material composition that contains the polyurethane component (A), the non-polyaddition-type radically polymerizable monomer (B), and the radical polymerization initiator (C) and that may contain unreacted diol compound (a1) and / or unreacted diisocyanate compound (a2); a polymerization / curing step of radically polymerizing the polyurethane component (A) and the non-polyaddition radically polymerizable monomer (B) in the secondary raw material composition using a radical polymerization initiator (C) to cure the resulting mixture; A method for producing a polyurethane-based material having a crosslinked structure by comprising: The method further includes a drying step of dehydrating the primary raw material composition by holding it in a dehumidifying dryer maintained at normal pressure and an absolute humidity of 6.0 (g / m 3 ) or less before carrying out the secondary raw material composition preparation step, so that the water content of the primary raw material composition is 20,000 ppm or less based on the total mass of the liquid components of the primary raw material composition.

3. A method for producing a polyurethane material, comprising:

2. 2. The method for producing a polyurethane material according to claim 1, wherein the raw materials further contain a filler (D), and a primary raw material composition further containing the filler (D) is prepared in the primary raw material composition preparation step.

3. The primary raw material composition is maintained in the dehumidifying dryer by placing the primary raw material composition in an open container, and (1) determining the mass of the primary raw material composition to be treated, w (g), relative to the external air contact area, s (cm ２ 2. The method for producing a polyurethane material according to claim 1, wherein the mixing is carried out by (1) leaving the mixture to stand in a state where the ratio of s / w (cm 2 / g) to s / w (cm 2 / g) is 0.30 (cm 2 / g) or more, or (2) stirring the mixture.

Images