JP2024065389A - Method for producing polyurethane composite material, polyurethane composite material obtained by said method, and method for producing material for dental cutting - Google Patents

Abstract

[Problem] To provide a high-strength and highly water-resistant polyurethane composite material having a crosslinked structure and in which a filler is dispersed in a resin matrix having a polyurethane content of more than 80% by mass in the resin, and a method for producing the same. [Solution] A first raw material composition containing a radically polymerizable diol: A1, a non-polyaddition-type radically polymerizable monomer: C, and a filler: D is mixed with a diisocyanate: B1 to carry out polyaddition of A1 and B1 to form a radically polymerizable polyurethane component: PU, and a second raw material composition containing PU, C, D, and a filler, in which the ratio of the amount of PU to the total amount of PU and C is substantially 80 to 95% by mass is prepared and radically polymerized, and the addition polymerization is carried out in the coexistence of a specific amount of a radically polymerizable monool: A2 or a radically polymerizable monoisocyanate: B2 to set the number average molecular weight of the PU to 1000 to 2000. [Selected Figure] None

Description

The present invention relates to a method for producing a polyurethane composite material, a polyurethane composite material and a material for dental cutting obtained by the method, and a method for producing a material for dental cutting.

In dental treatment, one method for producing dental prostheses such as inlays, onlays, crowns, bridges, and implant superstructures is to use a dental CAD/CAM system for cutting. A dental CAD/CAM system is a system that uses a computer to design dental prostheses based on three-dimensional coordinate data, and creates crown restorations using a cutting machine or the like. Various materials such as glass ceramics, zirconia, titanium, and resin are used as cutting materials. Resin-based materials for dental cutting include hardening compositions containing inorganic fillers such as silica, polymerizable monomers such as methacrylate, and polymerization initiators, which are hardened into block or disk shapes. Cutting materials are attracting attention from the perspective of high workability due to the shorter number of steps compared to conventional methods for producing dental prostheses, as well as the aesthetics and strength of the hardened products.

Such cutting materials are mainly used in the crown area, 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 is being considered. For example, Patent Document 1 describes a polyurethane composite material that can be suitably used as a cutting material, which takes advantage of the high strength characteristic of polyurethane resin while improving its drawback of low water resistance by introducing a crosslinked structure formed by polymerization of radically polymerizable groups into the polyurethane resin.

That is, Patent Document 1 describes that a raw material composition containing a diol compound (A2) having one or more radically polymerizable groups; a diisocyanate compound (A1); a polymerizable monomer (B) having one or more radically polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound (A2) or the diisocyanate compound (A1) (hereinafter also referred to as a "non-polyaddition radically polymerizable monomer"); a radical polymerization initiator (C); and a filler (D) is used, and A2 and A1 are polyadded to form a polyurethane component (A) having a molecular weight of 1500 to 5000, and then the radically polymerizable group contained in (A) is reacted with (B) to introduce a crosslinked structure. The polyurethane composite material is uniform throughout, has excellent strength and water resistance, and is suitable for use as a dental cutting material.

International Publication No. 2021/153446

The polyurethane composite material described in Patent Document 1 is an excellent material having the above-mentioned characteristics, but in order to maintain good uniformity, the proportion of the polyurethane component in the resin component cannot be increased beyond 80 mass%. Specifically, the "polymerizable monomer blending ratio Rr," defined as the proportion (mass%) of the mass of B in the total mass of the monomer components in the raw material composition {total mass of A2, A1, and B}, must be 20 to 80 mass% ("100-Rr," which represents the proportion of the polyurethane component, is 80 to 20 mass%).

For this reason, it was unclear what characteristics a crosslinked polyurethane composite material would have in the region where the polyurethane component content exceeds 80% by mass, or whether it would have the characteristics of being uniform overall and having excellent strength and water resistance, similar to the polyurethane composite material described in Patent Document 1. By increasing the content of the polyurethane component in a crosslinked polyurethane composite material, not only can high strength (derived from the polyurethane structure) be expected, but if it becomes possible to produce a crosslinked polyurethane composite material with a polyurethane component content of more than 80% by mass and it is confirmed that the uniformity and water resistance are well maintained, a new crosslinked polyurethane composite material with similar characteristics to the polyurethane composite material described in Patent Document 1 will be available.

The present invention therefore aims to provide a method for producing a crosslinked polyurethane composite material having a polyurethane component content of more than 80% by mass, and by extension, to provide a crosslinked polyurethane composite material having a polyurethane component content of more than 80% by mass, which is homogeneous, has excellent strength, and is water-resistant.

The present invention is to solve the above-mentioned problems, and a first aspect of the present invention is a method for producing a polyurethane-based composite material in which a filler is dispersed in a matrix made of a polyurethane-based resin having a crosslinked structure, using as raw materials a radically polymerizable diol (A1) made of a diol compound having a radically polymerizable group; a diisocyanate (B1) made of a diisocyanate compound; a non-polyaddition monomer (C) made of a non-polyaddition-reactive polymerizable monomer having a radically polymerizable group in the molecule; a filler (D) made of an inorganic filler; and an initiator (E) made of a thermal radical polymerization initiator; and a radically polymerizable monool (A2) made of a monool compound having a radically polymerizable group, or a radically polymerizable monoisocyanate (B2) made of a monoisocyanate compound having a radically polymerizable group,
a first raw material composition preparation step of preparing a first raw material composition containing the radical polymerizable diol (A1), the non-polyaddition monomer (C), and the filler (D);
a second raw material composition preparation step of mixing the first raw material composition with the diisocyanate (B1) and subjecting them to a polyaddition reaction to form a radically polymerizable polyurethane component (PU) composed of a polyurethane component having a radically polymerizable group, and preparing a second raw material composition containing the radically polymerizable polyurethane component (PU), the non-polyaddition monomer (C), the filler (D) and the initiator (E);
a polymerization/curing step of heating the second raw material composition to carry out radical polymerization to crosslink the radically polymerizable polyurethane component (PU) to obtain the polyurethane composite material,
In the second raw material composition preparation step,
The polyaddition reaction is
(1) in the presence of 0.2 to 0.7 mol of the radically polymerizable monol (A2) relative to 1 mol of the radically polymerizable diol (A1), such that the ratio of the total number of moles of the isocyanate groups of the diisocyanate (B1) to the total number of moles of the hydroxyl groups of the radically polymerizable monol (A2) and the radically polymerizable diol (A1): _TOH : T _NCO / _{T OH is} 0.9 to 1.1, or (2) in the presence of 0.2 to 0.7 mol of the radically polymerizable monoisocyanate (B2) relative to 1 mol of the _diisocyanate (B1), such that the ratio of the total number of moles of the hydroxyl groups of the radically polymerizable diol (A1) to the total number of moles of the isocyanate groups of the radically polymerizable monoisocyanate (B2) and the diisocyanate _{(B1): T NCO /} T _{The OH} is adjusted to 0.9 to 1.1.
thereby forming the radically polymerizable polyurethane component (PU) having a number average molecular weight of 1000 to 2000,
In the first raw material composition preparation step and the second raw material composition preparation step, the first raw material composition and the second raw material composition are prepared so that the content of the non-polyaddition monomer (C) contained in the second raw material composition is 5 mass% or more and less than 20 mass% of the total mass of the raw materials (A1), (B1), (C), and (A2) or (B2) expressed in terms of the amount of raw materials used in the polyaddition reaction.
The method for producing the polyurethane composite material is characterized in that:

In the above-mentioned manufacturing method (hereinafter also referred to as the "manufacturing method of the present invention"), it is preferable to: (1) prepare a first raw material composition further containing the radical polymerizable monool (A2) in the first raw material composition preparation step, and perform the polyaddition reaction in the second raw material composition preparation step in the presence of the radical polymerizable monool (A2); or (2) prepare a first raw material composition not containing the radical polymerizable monool (A2) in the first raw material composition preparation step, and mix the radical polymerizable monoisocyanate (B2) with the first raw material composition together with the diisocyanate (B1), thereby performing the polyaddition reaction in the second raw material composition preparation step in the presence of the radical polymerizable monoisocyanate (B2).

The radically polymerizable diol compound (A1) is preferably a diol compound in which the number of atoms constituting the main chain in the divalent organic residue interposed between the two hydroxyl groups contained in the molecule is 2 to 4.

The second aspect of the present invention is a polyurethane composite material (hereinafter also referred to as the "polyurethane composite material of the present invention") obtained by the manufacturing method of the present invention, in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure.

The third aspect of the present invention is a method for producing a material for dental cutting comprising a molded body of a polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure, the method including the production method of the present invention, and characterized in that the polymerization and curing steps are carried out in a mold.

According to the present invention, it is possible to obtain a polyurethane composite material that is uniform, has excellent strength and water resistance, and can be suitably used as a material for dental cutting. Furthermore, according to the manufacturing method of the present invention, it is possible to manufacture the polyurethane composite material of the present invention having the above-mentioned characteristics.

As a result of investigations to solve the above problems, the present inventors improved the manufacturing method of a crosslinked polyurethane composite material, specifically by adopting the manufacturing method described below (hereinafter also referred to as the "proposed manufacturing method"), they succeeded in obtaining a new crosslinked polyurethane composite material (hereinafter also referred to as the "proposed composite material") that is a polyurethane composite material in which a filler is dispersed in a polyurethane resin matrix having a polyurethane component content of more than 80 mass%, and that is uniform and has excellent strength and water resistance, and have already reported the manufacturing method thereof (hereinafter also referred to as the "proposed manufacturing method") (Patent Application No. 2021-191505).

That is,
"A polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin, the polyurethane resin having a number average molecular weight of 1500 to 5000, and having a crosslinked structure formed by radical polymerization of a radical polymerizable group of a polyurethane component having a radical polymerizable group and a radical polymerizable monomer, the polyurethane component occupying a proportion of more than 80 mass% and not more than 95 mass% of the polyurethane resin" (already proposed composite material) and a method for producing a molded article made of the polyurethane composite material, comprising: "a diol compound having one or more radical polymerizable groups; a polymerizable monomer having one or more radical polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound or the diisocyanate compound; a 10-hour half-life temperature: T a first raw material composition preparation step of preparing a first raw material composition comprising a thermal radical polymerization initiator having a _T10 of 60° C. or higher; and a filler; a second raw material composition preparation step of mixing the first raw material composition with a diisocyanate compound to polyaddition-react the diol compound with the diisocyanate compound to form a polyurethane component having a number average molecular weight of 1500 to 5000 and having a radically polymerizable group, thereby preparing a second raw material composition comprising the polyurethane component, the polymerizable monomer, the thermal radical polymerization initiator, and a filler, and which may also contain unreacted diol compound and/or unreacted diisocyanate compound; a second raw material composition preparation step of filling the second raw material composition into a mold while maintaining the temperature of the second raw material composition at 40° C. or higher and at a temperature not higher than a temperature 15° C. lower than the _T10 of the thermal radical polymerization initiator, and then heating the second raw material composition at a temperature 10° C. lower than the _T10 of the thermal radical polymerization initiator to a temperature a molding process for obtaining a polyurethane composite material molded body by heating the polyurethane composite material molded body to a temperature 25° C. higher than ₁₀ and carrying out radical polymerization; and
Formula: Rr = 100 x Br / [a1r + a2r + Ar + Br]
A method for producing a polyurethane composite molded body, characterized in that the polymerizable monomer blend ratio Rr defined by is 5 mass% or more and less than 20 mass% (already proposed manufacturing method)
is proposed.

The reason why the second raw material composition is heated to 40° C. or higher in the molding step of the above-mentioned proposed manufacturing method is to make it easier to fill the mold in the form of a uniform fluid paste, and it is necessary to use a thermal polymerization initiator having a _T10 of 60° C. or higher in order to prevent the progress of unexpected radical polymerization during heating. From the viewpoint of production efficiency and from the viewpoint of removing restrictions on the thermal polymerization initiator, it is preferable not to include such a heating step, but when the molecular weight of the polyurethane component exceeds 2000, the fluidity of the second raw material composition at room temperature is low and it is very difficult to fill the mold.

The inventors of the present invention thought that if the amount of the diisocyanate compound was reduced when preparing the radically polymerizable polyurethane component, the resulting polyurethane component would have a low molecular weight, and the fluidity of the second raw material composition would be increased, so that mold filling would be easily performed at room temperature even if the proportion of the polyurethane component exceeded 80% by mass. When they tried this, they were able to obtain the desired effect in terms of fluidity. However, it was found that the water resistance of the molded body obtained after polymerization and curing was greatly reduced. The manufacturing method of the present invention solves such problems. In addition, the polyurethane-based composite material of the present invention obtained by this manufacturing method is a new crosslinked polyurethane-based composite material (with a structure different from that of the previously proposed composite material) that has the characteristics of being uniform, having excellent strength and water resistance, and having a proportion of the polyurethane component in the polyurethane-based resin that serves as the matrix exceeding 80% by mass, just like the previously proposed composite material.

It is extremely difficult to identify the structure (particularly the state of crosslinking) of the polyurethane composite material of the present invention by analysis, etc., and even if analysis were possible, it would take a long time. For this reason, the polyurethane composite material of the present invention is identified by the manufacturing method (raw materials used, composition, reactions, etc.).

The manufacturing method of the present invention will be described in detail below. In this specification, unless otherwise specified, the notation "x to y" using the numerical values x and y means "greater than or equal to x and less than or equal to y." In such notations, when a unit is added only to the numerical value y, the unit is also applied to the numerical value x. In addition, in this specification, the term "(meth)acrylic" means both "acrylic" and "methacrylic."

1. Manufacturing method of the present invention In the manufacturing method of the present invention, a polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure is manufactured using the compounds and materials shown below as raw materials. Note that, in the present invention, for the sake of simplicity, each compound is represented by its abbreviation (the notation written to the right of ":" in the description of the compounds below) or abbreviation (the notation in parentheses following the abbreviation).
Diol compound having a radical polymerizable group: radical polymerizable diol (A1),
Diisocyanate compound: diisocyanate (B1),
Non-polyaddition reactive polymerizable monomer having a radical polymerizable group in the molecule: non-polyaddition monomer (C),
Inorganic filler: filler (D),
Thermal radical polymerization initiator: initiator (E), and Monool compound having a radical polymerizable group: radical polymerizable monool (A2), or Monoisocyanate compound having a radical polymerizable group: radical polymerizable monoisocyanate (B2)
The production method of the present invention includes the following "first raw material composition preparation step", "second raw material composition preparation step", and "polymerization and curing step".

<First raw material composition preparation step>
A step of preparing a first raw material composition containing a radical polymerizable diol (A1), a non-polyaddition monomer (C), and a filler (D).

<Second raw material composition preparation step>
a step of mixing the first raw material composition with the diisocyanate (B1) and carrying out a polyaddition reaction to form a radically polymerizable polyurethane component (PU), which is a polyurethane component having a radically polymerizable group, and preparing a second raw material composition containing the radically polymerizable polyurethane component (PU), the non-polyaddition monomer (C), the filler (D), and the initiator (E).

<Polymerization and curing process>
a step of heating the second raw material composition to carry out radical polymerization to crosslink the radically polymerizable polyurethane component (PU) to obtain the polyurethane composite material;

In the production method of the present invention, the polyaddition reaction in the second raw material composition preparation step is carried out so as to satisfy the following condition (1) or (2), thereby forming the radically polymerizable polyurethane component (PU) having a number average molecular weight of 1,000 to 2,000:
(1) In the coexistence of 0.2 to 0.7 moles of the radically polymerizable monol (A2) per mole of the radically polymerizable diol (A1), the ratio of the total moles of the isocyanate groups in the diisocyanate (B1) (T _NCO ) to the total moles of the hydroxyl groups in the radically polymerizable monol (A2) and the radically polymerizable diol (A1) (T _OH ) (T _NCO /T _OH) is 0.9 to 1.1.
(2) In the coexistence of 0.2 to 0.7 mol of the radically polymerizable monoisocyanate (B2) relative to the diisocyanate (B1), the total molar number of hydroxyl groups in the radically polymerizable diol (A1) is adjusted so that the ratio of the total molar number _{of isocyanate groups in the radically polymerizable monoisocyanate (B2) and the diisocyanate (B1) to TOH: T NCO / T OH} is 0.9 to 1.1.

Furthermore, in the manufacturing method of the present invention, in the first raw material composition preparation step and the second raw material composition preparation step, the first raw material composition and the second raw material composition are prepared so that the content of the non-polyaddition monomer (C) contained in the second raw material composition is 5% by mass or more and less than 20% by mass of the total mass of the raw materials (A1), (B1), (C), and (A2) or (B2) expressed as the amount on a raw material basis used in the polyaddition reaction.

This makes it possible to give the second raw material composition fluidity that allows it to be easily filled into a mold at room temperature, making it possible to efficiently produce the polyurethane composite material of the present invention that is uniform and has excellent strength and water resistance.

The manufacturing method of the present invention will be described below in detail with reference to the above-mentioned compounds and materials used, and each step will be described in detail.

1-1. Raw material compounds, etc. <Diol compound having a radically polymerizable group: radically polymerizable diol (A1)>
Diol compound having a radical polymerizable group: The radical polymerizable diol (A1) is a compound that serves as a raw material for forming the radical polymerizable polyurethane component (PU). The two hydroxyl groups (-OH groups) of the radical polymerizable diol (A1) and the two isocyanate groups of the diisocyanate (B1) undergo a polyaddition reaction to form the main chain portion of the radical polymerizable polyurethane component (PU).

As the radically polymerizable diol (A1), a compound having at least one radically polymerizable group and two hydroxyl groups in the molecule can be used. Here, the radically polymerizable group means 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. As the radically polymerizable group, a (meth)acrylate group is particularly preferred. In the radically polymerizable diol (A1), the organic residue to which the two hydroxyl groups and the radically polymerizable group are bonded is preferably a hydrocarbon group.

The radically polymerizable diol (A1) has a radically polymerizable group, which introduces the radically polymerizable group into the main chain of the polyurethane molecule formed by the polyaddition reaction. In addition, during the radical polymerization in the molding process, the radically polymerizable groups in the molecule of the radically polymerizable polyurethane component (PU) react with each other, or with the radically polymerizable group in the molecule of the radically polymerizable polyurethane component (PU) and the radically polymerizable group of the non-polyaddition monomer (C) to form bonds, thereby forming crosslinks. This improves the water resistance of the polyurethane material, which is the cured product.

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 (A1) is preferably 1 to 4, and more preferably 1 to 2. When the number of radically polymerizable groups is 4 or less, it becomes easier to suppress the shrinkage of the cured body formed during the radical polymerization reaction.

The number of atoms constituting the main chain in the divalent organic residue between the two hydroxyl groups contained in the molecule of the radically polymerizable diol (A1) (hereinafter sometimes referred to as the "OH distance") is preferably 2 to 4. By setting the OH distance of the radically polymerizable diol (A1) within the above range, radically polymerizable groups and urethane bonds can be introduced at a high density into the molecule of the radically polymerizable polyurethane component (PU) obtained by the polyaddition reaction, and the strength of the polyurethane composite material can be increased.

When two or more types of radically polymerizable diols (A1) are used, the OH distance refers to a value calculated as the average value of two or more types of radically polymerizable diols (A1). Here, when n types of radically polymerizable diols (A1), where n is an integer of 2 or more, are used, the average OH distance refers to a value calculated as the sum of the products obtained by multiplying the OH distance: Dx of each radically polymerizable diol by the mole fraction (mol/mol): Mx of each radically polymerizable diol, which is defined as the number of moles of each radically polymerizable diol in the total number of moles of radically polymerizable diols.

In addition, from the viewpoint of reactivity during polyaddition, the radically polymerizable diol (A1) has primary or secondary hydroxyl groups. In particular, it is preferable that the radically polymerizable diol (A1) has both primary and secondary hydroxyl groups. By using a radically polymerizable diol (A1) that satisfies the above conditions, it becomes easier to adjust the number average molecular weight of the radically polymerizable polyurethane component (PU) to 1000 to 2000 when the radically polymerizable monol (A2) is added, and it becomes easier to maintain high bending strength and water resistance of the obtained molded body.

Examples of compounds suitable for use as the radically polymerizable diol (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 or vinylbenzoic acid). These can be used alone or in combination with different types.

<Diisocyanate Compound: Diisocyanate (B1)>
Diisocyanate (B1) is a polyurethane precursor component for forming a radically polymerizable polyurethane component (PU), and any compound having two isocyanate groups (-N=C=O groups) in one molecule can be used without any particular limitation. The (divalent) organic residue to which the two isocyanate groups are bonded does not need to have a radically polymerizable group. The organic residue is preferably a divalent hydrocarbon group in which at least one hydrogen atom in the hydrocarbon group may be substituted with at least one heteroatom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms, and is preferably a divalent hydrocarbon group having an alicyclic structure or an aromatic ring which may have as a substituent a (substituted) alkyl group in which at least one hydrogen atom may be substituted with the heteroatom.

Examples of compounds that can be suitably used as diisocyanate (B1) 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, and dicyclohexyl. Examples include diisocyanate such as dihexylmethane 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.

Among these, it is preferable for the diisocyanate (B1) to have a phenyl group in the molecule from the viewpoints of the fluidity of the resulting second raw material composition and the strength of the resulting polyurethane composite material.

<Monool Compound Having Radically Polymerizable Group: Radically Polymerizable Monool (A2)>
The radical polymerizable monool (A2) is a compound that is a raw material for forming the radical polymerizable polyurethane component (PU), and forms the terminal portion of the radical polymerizable polyurethane component (PU) by coexisting during the polyaddition. As the radical polymerizable monool (A2), a compound having at least one radical polymerizable group and one hydroxyl group in the molecule can be used without any particular limitation. The radical polymerizable group of the radical polymerizable monool (A2) can be the same as the radical polymerizable group of the radical polymerizable diol (A1). In the radical polymerizable monool (A2), the organic residue to which one hydroxyl group and the radical polymerizable group are bonded is preferably a hydrocarbon group.
From the viewpoint of strength and water resistance of the polyurethane material, which is the product, the number of radically polymerizable groups contained in the molecule of the radically polymerizable monool (A2) is preferably 1 to 4, and particularly preferably 1 to 2. From the viewpoint of reactivity during polyaddition and molecular weight reduction effect, the radically polymerizable monool compound (A2) has a primary or secondary hydroxyl group that is highly reactive with an isocyanate group. In particular, it is preferable to have a primary hydroxyl group that is more excellent in molecular weight reduction effect. Examples of compounds that are preferably used as the radically polymerizable monool (A2) include ethylene glycol (meth)acrylate, pentaerythritol tri(meth)acrylate, and 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid. The radically polymerizable monool (A2) may be used alone or in a mixture of two or more kinds.

<Monoisocyanate compound having a radically polymerizable group: radically polymerizable monoisocyanate (B2)>
The radically polymerizable monoisocyanate (B2) is also a compound that serves as a raw material for forming the radically polymerizable polyurethane component (PU), and forms the terminal portion of the radically polymerizable polyurethane component (PU) by coexisting during the polyaddition. As the radically polymerizable monoisocyanate (B2), a compound having at least one radically polymerizable group and one isocyanate group in the molecule can be used without any particular limitation. The radically polymerizable group is the same as in (A2) and (A1). In the radically polymerizable monoisocyanate (B2), the organic residue to which one isocyanate group and the radically polymerizable group are bonded is preferably a hydrocarbon group. From the viewpoint of the strength and water resistance of the polyurethane material, which is the product, the number of radically polymerizable groups contained in the molecule is preferably 1 to 4, and particularly preferably 1 to 2. When the number of radically polymerizable groups is 4 or less, it is easier to suppress the shrinkage of the cured body formed during the radical polymerization reaction. Examples of compounds that can be suitably used as the radical polymerizable monoisocyanate (B2) include 2-isocyanatoethyl (meth)acrylate, 2-(2-(meth)acryloyloxyethyloxy)ethyl isocyanate, 1,1-(bis(meth)acryloyloxymethyl)ethyl isocyanate, etc. The radical polymerizable monoisocyanate (B2) may be used alone or in combination of two or more kinds.

<Non-polyaddition reactive polymerizable monomer having a radical polymerizable group in the molecule: non-polyaddition monomer (C)>
The non-polyaddition monomer (C) is a compound having at least one radical polymerizable group in the molecule, and not undergoing polyaddition reaction with either the radical polymerizable diol (A1) or the diisocyanate (B1). That is, the molecule does not contain any group that undergoes polyaddition reaction with the radical polymerizable diol (A1) or with the diisocyanate (B1), specifically, any group of hydroxyl group, amino group, carboxy group, isocyanate group, or mercapto group. Therefore, the non-polyaddition monomer (C) does not undergo polyaddition reaction with either the radical polymerizable monool (A2) or the radical polymerizable monoisocyanate (B2).

The type of radical polymerizable group is the same as in the cases of (A2), (A1), and (B2). From the viewpoint of ease of forming crosslinks, the number of radical polymerizable groups is preferably 2 to 6, and more preferably 2 to 4. By making the number of radical polymerizable groups 2 or more, the crosslink density can be increased, making it easier to obtain a cured product with sufficient strength. Furthermore, by making the number of radical polymerizable groups 6 or less, it becomes easier to suppress shrinkage during curing. Furthermore, it is preferable that the non-polyaddition radical polymerizable monomer (B) is a liquid at room temperature (i.e., 25°C).

Examples of compounds that can be suitably used as the non-polyaddition monomer (C) include diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, trimethylolpropane acrylate, trimethylolpropane methacrylate, pentaerythritol acrylate, pentaerythritol methacrylate, ditrimethylolpropane acrylate, ditrimethylolpropane methacrylate, dipentaerythritol acrylate, dipentaerythritol methacrylate, etc. Among these, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate are particularly preferred.

<Inorganic filler: filler (D)>
The filler (D) disperses in the polyurethane resin matrix and forms a composite with the polyurethane resin matrix, thereby improving the physical properties such as mechanical strength, abrasion resistance, and water resistance of the polyurethane composite material.

As the filler (D), it is preferable to use an inorganic filler consisting of a powder of an inorganic substance such as silica, alumina, titania, zirconia, or a composite oxide thereof, or glass. Specific examples of such inorganic fillers include spherical particles or irregular 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, it is preferable to use silica, titania, zirconia, or a composite oxide thereof as the filler (D), and silica or a composite oxide thereof is particularly preferable. These inorganic fillers are not likely 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 the transparency and aesthetics.

The shape of the particles constituting 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 preferable.

From the viewpoints of abrasion resistance, surface smoothness, and gloss durability, the average particle size of the powder constituting the filler (D) is preferably 0.001 μm to 100 μm, and more preferably 0.01 μm to 10 μm. In addition, it is preferable to use a filler (D) having a plurality of particle sizes, since it is easier to increase the content of the filler (D) in the polyurethane composite material. Specifically, it is preferable to combine a particle size of 0.001 μm to 0.1 μm with a particle size of 0.1 μm to 100 μm, and it is more preferable to combine a particle size of 0.01 μm to 0.1 μm with a particle size of 0.1 μm to 10 μm.

The average particle diameter of the inorganic filler means the average particle diameter determined by image analysis using a scanning electron microscope (SEM) image, and means the value obtained by measuring the maximum diameter (nm) of each of 30 or more arbitrarily selected particles based on an image (or photograph) obtained by observing a powder sample with an SEM at a magnification of 5,000 to 100,000 times so that 100 or more spherical particles whose overall shape can be confirmed are included in the field of view, and dividing the sum by the number: n (a natural number of ≧30). In other words, when the maximum diameter of each particle is represented by x _i (i is a natural number from 1 to n) and the average particle diameter is represented by x _AV , it means a value defined by x _AV = (Σx _i )/n.

When using an inorganic filler as filler (D), it is preferable to use one 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.

<Thermal Radical Polymerization Initiator: Initiator (E)>
Thermal radical polymerization initiator: The initiator (E) has a function of initiating a radical polymerization reaction in the polymerization and curing process, and reacts and bonds the radical polymerizable group of the radical polymerizable polyurethane component (PU) with the radical polymerizable group of the radical polymerizable monomer (C), thereby polymerizing and curing the second raw material composition and forming crosslinking points in the polyurethane resin that becomes the matrix. By using a thermal radical polymerization initiator, it is possible to heat and polymerize the second raw material composition filled in the mold (molding die) in the polymerization and curing process. From the viewpoint of the heating temperature during polyaddition and the temperature at which the second raw material composition is filled into the mold, it is preferable to use one having a 10-hour half-life temperature T ₁₀ in the range of 40 to 120°C. Here, the 10-hour half-life temperature: T ₁₀ is the temperature at which the amount of the thermal polymerization initiator present is reduced to half of the initial amount after 10 hours have passed from the initial time, and is used as an index of the reactivity of the thermal polymerization initiator. Specific examples of the thermal radical polymerization initiator (E) that can be suitably used include peroxide initiators such as benzoyl peroxide and tert-butyl peroxylaurate, and azo initiators such as azobisbutyronitrile, etc. These thermal polymerization initiators may be used alone or in combination of two or more.

<Other additives>
In addition to the essential components described above, the first raw material composition or the second raw material composition may contain various other additives, such as polymerization inhibitors, fluorescent agents, ultraviolet absorbers, antioxidants, pigments, antibacterial agents, X-ray contrast agents, etc., and the amounts of the additives may be appropriately determined depending on the desired purpose.

1-2. Each step in the production method of the present invention will be described below.

<First raw material composition preparation step>
In the first raw material composition preparation step, a first raw material composition containing a radical polymerizable diol (A1), a non-polyaddition monomer (C), and a filler (D) is prepared. The initiator (E) may be mixed in either the first raw material composition preparation step or the second raw material composition preparation step, but it is preferable to mix it in the first raw material composition preparation step. In addition, when the polyaddition reaction in the second raw material composition preparation step described later is carried out in the presence of a radical polymerizable monool (A2), it is preferable to mix the radical polymerizable monool (A2) in the first raw material composition. By doing so, the radical polymerizable monool (A2) is dispersed in the first raw material composition, and it becomes easy to adjust the number average molecular weight of the radical polymerizable polyurethane component (PU) prepared during the polyaddition reaction to a range of 1000 to 2000. However, in order to prevent the polyaddition reaction from occurring in the first raw material composition, it is necessary not to mix the diisocyanate (B1).

The amount of each component is determined as follows. That is, the composition of the first raw material composition is determined based on the composition of the second raw material composition to be obtained. Specifically, on the premise that the radical polymerizable diol (A1) and the diisocyanate (B1), and the radical polymerizable monool (A2) or the radical polymerizable monoisocyanate (B2) are quantitatively polyaddition reacted to produce the radical polymerizable polyurethane component (PU), the ratio of the total number of moles of hydroxyl groups possessed by the radical polymerizable monool (A2) and the radical polymerizable diol compound (A1): T _OH to the total number of moles of isocyanate groups possessed by the radical polymerizable monoisocyanate (B2) and the diisocyanate (B1): T _NCO /T _OH is determined to be 0.9 to 1.1. Note that, it is more preferable that T _NCO /T _OH is 1.0 to 1.05 because the strength of the obtained _polyurethane composite material is less likely to decrease and the second raw material composition is easier to mold.

Here, when the polyaddition reaction in the second raw material composition preparation step described later is carried out in the presence of a radical polymerizable monool (A2), the total number of moles of hydroxyl groups in the radical polymerizable monool (A2) and the radical polymerizable diol compound (A1) is T _OH , and since the radical polymerizable monoisocyanate (B2) is not used, the above T _NCO is the total number of moles of isocyanate groups in the diisocyanate (B1). In this case, it is necessary to use 0.2 to 0.7 moles of the radical polymerizable monool (A2) per mole of the radical polymerizable diol (A1). If the ratio is less than 0.2, the effect of reducing the molecular weight is small, making it difficult to obtain a uniform cured product, and if the ratio is more than 0.7, the bending strength and water resistance of the obtained cured product are reduced.

On the other hand, when the polyaddition reaction is carried out in the presence of a radically polymerizable monoisocyanate (B2), no radically polymerizable monool (A2) is used, so the above T _OH is the total number of moles of hydroxyl groups in the radically polymerizable diol compound (A1), and the total number of moles of isocyanate groups in the radically polymerizable monoisocyanate (B2) and the diisocyanate (B1) is T _NCO . In this case, it is necessary to use 0.2 to 0.7 moles of the radically polymerizable isocyanate (B2) per mole of the diisocyanate (B1). If the ratio is less than 0.2, the effect of reducing the molecular weight is small, making it difficult to obtain a uniform cured product, and if the ratio is more than 0.7, the bending strength and water resistance of the obtained cured product are reduced.

The quantitative ratios of (A2), (A1), (B2) and (B1) used in the first raw material composition preparation process and the second raw material composition preparation process may be determined based on the amount of the radically polymerizable diol compound (A1), provided that such conditions are met. Note that these components undergo a substantially quantitative polyaddition reaction in the second raw material composition preparation process to become the radically polymerizable polyurethane component (PU), and although some unreacted material remains depending on the quantitative ratio, the total mass of these components can be considered to be substantially the same as the mass of the radically polymerizable polyurethane component (PU) contained in the second raw material composition.

The amount of the non-polyaddition monomer (C) is required to be 5% by mass or more and less than 20% by mass of the total mass of the raw materials (A2), (A1), (B2), (B1) and (C) expressed in terms of the amount of raw materials used in the polyaddition reaction. Therefore, the amount of the non-polyaddition monomer (C) contained in the second raw material composition should be determined so as to be 5% by mass or more and less than 20% by mass of the total mass of the raw materials (A2), (A1), (B2), (B1) and (C) based on the amount of the radical polymerizable diol (A1) and the radical polymerizable monool (A2) used in the first raw material composition preparation step, based on the amount of the diisocyanate (B1) and the radical polymerizable isocyanate (B2) determined so as to satisfy the above conditions from these amounts. In addition, with regard to (A1), (B1), and (A2) or (B2), a small amount may remain partially unreacted, and (A2) or (B2) that is not used is naturally not included (the content is zero parts by mass). Therefore, the content (parts by mass) of each of the components contained in the second raw material composition is, respectively,
Content of radically polymerizable polyurethane component (PU): [PU],
Content of non-polyaddition monomer (C): [C],
Content of radical polymerizable diol (A1): [A1],
Content of diisocyanate (B1): [B1]
Content of radical polymerizable monool (A2): [A2],
Content of radically polymerizable monoisocyanate (B2): [B2],
When expressed as:, the total mass of these is equal to the total mass of the raw materials (A2), (A1), (B2), (B1) and (C) expressed in the amount based on the raw materials. Therefore, the total mass of these:
When [PU] + [C] + [A1] + [A2] + [B1] + [B2] = [SUM], the amount of the non-polyaddition monomer (C) is determined so that the "polymerizable monomer blend ratio: Rr" defined by the formula: Rr = ([C] / [SUM]) x 100 is 5% by mass or more and less than 20% by mass. If Rr is less than 5% by mass, it is very difficult to obtain a polyurethane composite material with a uniform crosslinked structure. In addition, since most of the unreacted (A1), (B1), and (A2) or (B2) are also incorporated into the crosslinked body (crosslinked polyurethane resin) in the polymerization and curing process, (100-Rr) (mass%) is the (substantial) polyurethane content in the crosslinked polyurethane resin, and the manufacturing method of the present invention obtains a polyurethane composite material having a crosslinked polyurethane resin with a content of 80% by mass or more and less than 95% by mass as a matrix.

The amount of filler (D) used may be appropriately determined depending on the physical properties such as the strength of the desired polyurethane composite material. When the content (parts by mass) of filler (D) contained in the second raw material composition is [D], the amount is preferably such that the filling rate (% by mass) defined by the formula: filling rate = {[D]/([D]+[SUM])}x100 is 60% by mass to 85% by mass, and more preferably 65% by mass to 80% by mass. In addition, when the polyurethane composite material produced by the method for producing a polyurethane composite material of this embodiment is used as a material for dental cutting, the filling rate is more preferably 65% by mass to 80% by mass, and even more preferably 70% by mass to 80% by mass.

The amount of initiator (E) may be within the range of 0.005 to 2.0 parts by mass per 100 parts by mass of [SUM], but is preferably within the range of 0.01 to 1.0 part by mass.

The first raw material composition may be prepared by mixing all the components constituting the first raw material composition at once, or by preparing a mixture by mixing some of the components constituting the first raw material composition, and then adding and mixing the remaining components constituting the first raw material composition. In this case, the mixing method for mixing each component is not particularly limited, and a method using a magnetic stirrer, a Raikai machine, a planetary mixer, a Trimix, a centrifugal mixer, etc. is appropriately used. In addition, because it is easy to uniformly disperse the filler (D), it is preferable to prepare a mixed composition by first mixing the radical polymerizable diol (A1), the radical polymerizable monool (A2) used as needed, and the non-polyaddition monomer (C), and then add the filler (D) to this mixed composition and mix it to prepare the first raw material composition. In addition, it is preferable to add other additives to the first raw material composition because it is easy to suppress side reactions and easy to disperse. Furthermore, if the components are mixed under vacuum conditions, the radical polymerization will progress, which will deteriorate operability and make it difficult to uniformly disperse the components, making it difficult to obtain a uniform hardened body. Therefore, it is preferable to mix the components under normal pressure or pressurized conditions. The first raw material composition thus prepared is preferably subjected to a degassing treatment to remove any air bubbles contained therein. As a degassing method, a known method performed under normal pressure or pressurized conditions can be used, and methods such as pressurized degassing and centrifugal degassing can be used as desired.

The first raw material composition may further contain, as an additive, a catalyst that promotes the polyaddition reaction, if necessary. Examples of catalysts that promote the polyaddition reaction include tin octoate and dibutyltin diacetate.

<Second raw material composition preparation step>
In the second raw material composition preparation step, the first raw material composition is mixed with diisocyanate (B1) and subjected to a polyaddition reaction to form a radically polymerizable polyurethane component (PU), which is a polyurethane component having a radically polymerizable group, and a second raw material composition containing the radically polymerizable polyurethane component (PU), a non-polyaddition monomer (C), a filler (D) and an initiator (E) is prepared. Note that, if the first raw material composition does not contain the initiator (E), the initiator (E) is blended in the second raw material composition preparation step.

The polyaddition reaction in the second raw material composition preparation step must be carried out in the presence of 0.2 to 0.7 mol of radically polymerizable monool (A2) per mol of radically polymerizable diol compound (A1), or in the presence of 0.2 to 0.7 mol of radically polymerizable monoisocyanate (B2) per mol of diisocyanate compound (B1).

For this reason, when the first raw material composition does not contain a predetermined amount of radical polymerizable monool (A2), it is necessary to mix (B2). When mixing (B2), it is preferable to prepare a mixture of each of the predetermined amounts of (B2) and (B1) in advance and mix this with the first raw material composition. When mixing (A2), it is preferable to mix (A2) with the first raw material composition before mixing (B1) or simultaneously with mixing (B1) so that the amount of (A2) used is a predetermined amount, without (A2) coming into direct contact with (B1). Note that when the first raw material composition contains a predetermined amount of radical polymerizable monool (A2), only (B1) is mixed with the first raw material composition. The amounts of (B1) and (A2) or (B2) used may be determined so as to satisfy the above-mentioned conditions.

In the second raw material composition preparation step, a radical polymerizable polyurethane component (PU) having a number average molecular weight of 1000 to 2000 is formed by the polyaddition reaction. Here, the number average molecular weight of the radical polymerizable polyurethane component (PU) means the number average molecular weight in terms of polystyrene determined by GPC (gel permeation chromatography) measurement. The number average molecular weight of the radical polymerizable polyurethane component (A) in the second raw material composition can be determined by adding a solvent such as THF (tetrahydrofuran) or dimethyl sulfoxide (DMSO) to the radical polymerizable raw material composition as necessary, removing insoluble components such as the filler (D) by filtration, centrifugation, or the like, and performing GPC measurement on the resulting solution (i.e., a solution consisting of a matrix raw material composition or a mixture of the matrix raw material composition and a solvent added as necessary). The number average molecular weight of the radical polymerizable polyurethane component (PU) can be controlled to a range of 1000 to 2000 by satisfying the above-mentioned conditions in the amounts of (A1), (B1), and (A2) or (B2) used.

In the polymerization and curing process described below, the radically polymerizable polyurethane component (PU) forms a crosslink by polymerization between the radically polymerizable groups of the radically polymerizable polyurethane component (PU) or between the radically polymerizable groups of the radically polymerizable monomer (C), resulting in a "polyurethane resin having a crosslinked structure" that constitutes the matrix of the polyurethane composite material obtained in the end. If the number average molecular weight of the radically polymerizable polyurethane component (PU) exceeds 2000, it becomes necessary to heat and mold the second raw material composition to 40°C or higher in order to obtain a uniform molded product. If the number average molecular weight is below 1000, the strength and water resistance of the resulting polyurethane composite material will decrease.

The polyaddition reaction is started by heating the first raw material composition with the diisocyanate (B1) or the diisocyanate (B1) and the radical polymerizable monoisocyanate (B2) simultaneously or after mixing, if necessary, and is carried out until at least one of the radical polymerizable diol (A1) and the diisocyanate (B1) is substantially consumed by the polyaddition reaction. At this time, it is necessary to carry out the polyaddition reaction at a reaction temperature lower than the _T10 of the thermal radical polymerization initiator: initiator (E) used. In the production method of the present invention, a small amount of unavoidable radical polymerization reaction is allowed.

The reaction time varies depending on the reaction temperature. For example, if the reaction temperature is 30°C or more and less than 50°C, it is preferably 60 hours or more, more preferably 72 hours or more. If the heating temperature is 50°C or more and less than 80°C, it is preferably 24 hours or more, more preferably 36 hours or more. If the heating temperature is 80°C or more, it is preferably 15 hours or more, more preferably 24 hours or more. In any of these cases, the upper limit of the heating time is not particularly limited, but from the practical viewpoint of productivity, it is preferable to set it to 120 hours or less. When preparing the second raw material composition, the mixing method for mixing each component is not particularly limited, and a method using a magnetic stirrer, a Raikai machine, a planetary mixer, a trimix, a centrifugal mixer, etc. is appropriately used. In addition, when mixing each component, if it is performed under vacuum conditions for a long time, unintended radical polymerization may occur, which is not preferable, so it is preferable to mix it under normal pressure conditions or pressurized conditions.

As described above, in the proposed method of polyaddition using only radically polymerizable diol (A1) and diisocyanate (B1), if the amount of diisocyanate (B1) used is reduced, the molecular weight of the resulting radically polymerizable polyurethane component (PU) decreases, and the fluidity of the second raw material composition can be increased. However, the polyurethane composite material obtained through the polymerization and curing process has low water resistance. This is because, as shown in the reaction formula below, the radically polymerizable polyurethane component (PU) obtained by polyaddition using only radically polymerizable diol (A1) and diisocyanate (B1) has highly hydrophilic hydroxyl groups (-OH groups) or isocyanate groups (-N=C=O) at both ends of the molecule, and the molecular weight is reduced (the number of these groups increases relatively), which is thought to be the reason for this. The following formula is a simplification for explaining the terminal structure of the resulting radically polymerizable polyurethane component (PU), in which the group -R ¹ - in (A1) represents a divalent organic group having a radically polymerizable group and no hydroxyl group or isocyanate group, and the group -R ² - in (B1) represents a divalent organic group having no hydroxyl group or isocyanate group.

In contrast, in the production method of the present invention, since the radical polymerizable monool (A2) or the radical polymerizable monoisocyanate (B2) is coexisted during the polyaddition reaction, as shown in the reaction formula below, at least one end of the radical polymerizable polyurethane component (PU) molecule is neither a hydroxyl group nor an isocyanate group, and therefore the hydrophilicity of the radical polymerizable polyurethane component (PU) decreases according to the blending ratio of these components, and it is considered that the decrease in water resistance of the obtained polyurethane composite material is suppressed even if the molecular weight is reduced. The following formula is also simplified to explain the terminal structure of the obtained radical polymerizable polyurethane component (PU). In the following formula, the groups -R ¹ - and -R ² - are as described above, the group -X represents a radical polymerizable group, and the groups -R ³ - and -R ⁴ - represent divalent organic groups having no radical polymerizable group, hydroxyl group, or isocyanate group.

<Polymerization and curing process>
In the polymerization and curing step, the second raw material composition is heated to perform radical polymerization, thereby crosslinking the radically polymerizable polyurethane component (PU) to obtain the polyurethane composite material. In the polymerization and curing step, it is preferable to fill the second raw material composition into a mold and then perform the radical polymerization, because a polyurethane composite material molded body of a desired shape can be obtained. In the manufacturing method of the present invention, since the radically polymerizable polyurethane component (PU) contained in the second raw material composition obtained in the step is as described above, the second raw material composition becomes a uniform fluid paste even at a relatively low temperature, for example, less than 40°C, and can be easily filled into the mold. The method of filling the second raw material composition into the mold is not particularly limited, and can be suitably performed, for example, by pressure casting or vacuum casting.

During radical polymerization, heat is generated by reaction heat, so it is preferable to control the heating temperature (curing temperature). In this case, it is preferable to control the heating temperature so as not to exceed 150°C, and it is particularly preferable to carry out the heating in the range of -10°C to +25°C of the 10-hour half-life temperature: T ₁₀ (°C) of the thermal radical polymerization initiator, that is, a temperature 10°C lower than T ₁₀ (lower limit temperature L) to a temperature 25°C higher than T ₁₀ (upper limit temperature H). By setting the heating temperature to the lower limit temperature L or higher, it is possible to sufficiently increase the radical polymerization rate, and it is also easy to suppress the occurrence of unintended coloring of the cured body. In addition, by setting the heating temperature to the upper limit temperature H or lower, it is possible to prevent excessive consumption of the radical polymerizable group present in the reaction system and to suppress the rapid progress of radical polymerization. By controlling the heating temperature within the above-mentioned temperature range, it is possible to proceed with polymerization curing at an industrially acceptable reaction rate, and it is also possible to suppress the occurrence of distortion or cracks in the cured body due to the rapid progress of the reaction, and it is also extremely easy to suppress the occurrence of deterioration of the non-polyaddition monomer (C). In addition, when radical polymerization is performed by heating, the second raw material composition may be pressurized during radical polymerization in order to suppress the formation of voids due to bubbles in the cured body. There is no limitation on the pressurization method, and the pressurization may be performed mechanically or with a gas such as nitrogen. By performing the radical polymerization step in this manner, a molded body made of the polyurethane composite material of the present invention in which the filler (D) is dispersed in the polyurethane resin matrix can be efficiently obtained.

2. Polyurethane Composite Material of the Present Invention The polyurethane composite material of the present invention is obtained by the manufacturing method of the present invention, and is a matrix of a novel polyurethane resin having a crosslinked structure formed by radical polymerization of radical polymerizable groups of the radical polymerizable polyurethane component (PU) and/or between the radical polymerizable groups and a radical polymerizable monomer, and having a filler dispersed therein. The polyurethane resin has a feature that the ratio of the polyurethane component in the polyurethane resin is more than 80 mass% and not more than 95 mass%. The composite material has water resistance while maintaining high strength even in a hydrophilic environment such as the oral cavity. Because of such high water resistance, the manufacturing method of the present invention can be suitably used as a manufacturing method of a material for dental cutting, particularly when a dental prosthesis is manufactured by cutting the material for dental cutting using a dental CAD/CAM system.

3. Manufacturing method of dental cutting material The manufacturing method of dental cutting material, which is the third embodiment of the present invention, is a method for manufacturing a dental cutting material comprising a molded body of a polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure, and includes the manufacturing method of the present invention, characterized in that the polymerization and curing steps are carried out in a mold.

That is, in the polymerization and curing step in the manufacturing method of the present invention, the molded article of the polyurethane composite material of the present invention obtained by filling the second raw material composition into a mold and then heating it to carry out radical polymerization to crosslink the radically polymerizable polyurethane component (PU) becomes a dental cutting material. The dental cutting material obtained by the above manufacturing method can be suitably used as the cutting part of a so-called dental mill blank, which is used to manufacture dental prostheses by cutting the dental cutting material using a dental CAD/CAM system.

When manufacturing such dental mill blanks, a mold corresponding to the shape of the part to be machined is used, and the second raw material composition, heated to a temperature of, for example, 40°C or less as necessary, is injected and filled into the mold using pressure casting or vacuum casting, and hardened. The hardened body obtained is then removed from the mold, and post-processing such as heat treatment to relieve residual stress, correction of shape by cutting, and polishing are performed as necessary, and a fixing device such as a pin for holding the blank in a CAD/CAM device is attached to obtain a material for dental machining.

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

1. Raw Materials The components used in each of the Examples and Comparative Examples and their abbreviations are shown below.

(1) Radically Polymerizable Diol (A1)
GLM: glycerol monomethacrylate (OH distance: 2)
(2) Diisocyanate (B1)
XDI: m-xylylene diisocyanate (3) Radical polymerizable monool (A2)
HEMA: Ethylene glycol monomethacrylate GDMA: Glycerin dimethacrylate (4) Radically polymerizable monoisocyanate (B2)
MOI: Isocyanatoethyl methacrylate (5) Non-polyaddition monomer (C)
TEGDMA: Triethylene glycol dimethacrylate (6) 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)
(7) Initiator (E)
PBC: t-butylcumyl peroxide (10 hour half-life temperature 120° C.).

2. Manufacturing Method of Polyurethane Material Examples of the manufacturing method of the present invention will be described below together with comparative examples.

Example 1
(1) First raw material composition preparation step First, a mixed composition was prepared by mixing GLM (7.9 parts by mass) which is a radical polymerizable diol (A1), HEMA (2.2 parts by mass) which is a radical polymerizable monool (A2), TEGDMA (4.3 parts by mass) which is a non-polyaddition monomer (C), and PBC (0.1 parts by mass) which is an initiator (E). Next, the first raw material composition was prepared by adding F1 (52.5 parts by mass) and F2 (22.5 parts by mass) which are fillers (D) to this mixed composition and kneading. The above operation was carried out under a room temperature (25 ° C) environment.

(2) Second raw material composition preparation step In a room temperature (25° C.) environment, XDI (1.24 g), which is the diisocyanate (B1), was added to a planetary centrifugal mixer containing the obtained first raw material composition (9.0 g) and kneaded, and then the mixture was allowed to stand in an incubator at 37° C. for 72 hours to carry out a polyaddition reaction, thereby forming a radically polymerizable polyurethane component (PU) to prepare a second raw material composition.
Table 1 summarizes the raw materials (abbreviations) and amounts used (numbers in parentheses: units are parts by mass) and composition parameters used in the first raw material composition preparation step and the second raw material composition preparation step. In Table 1, "radical polymerizability" is abbreviated as "polymerizable". In Table 1, "T _NCO /T _OH " means the ratio of the total number of moles of isocyanate groups in (B1): T _NCO to the total number of moles of hydroxyl groups in (A1) and (A2): T _OH , "A2/A1 molar ratio" means the molar ratio of (A2) to 1 mole of (A1), "C blending ratio Rr" means the "polymerizable monomer blending ratio: Rr" defined as Rr = ([C] / [SUM]) x 100 described above, and "D filling rate" means the "filling rate" of the filler (D) described above. In the table, "↑" means "same as above".

(3) Evaluation of the second raw material composition (3-1) Evaluation of the number average molecular weight of the radical polymerizable polyurethane component (PU) With respect to the obtained second raw material composition, the number average molecular weight of the radical polymerizable polyurethane component (PU) was evaluated as follows. That is, 1 g of the obtained second raw material composition was weighed into a screw tube bottle, 3.5 ml of DMSO was added and stirred to obtain a DMSO solution, which was centrifuged at 10,000 rpm for 10 minutes in a centrifuge (manufactured by AS ONE Corporation). Next, the supernatant obtained by centrifugation was filtered with a membrane filter (PORE SIZE 20 μm, manufactured by ADVANTEC Co., Ltd.) to obtain a filtrate. Then, the filtrate was subjected to GPC measurement under the GPC measurement conditions shown below to obtain the polystyrene-equivalent number average molecular weight of the radical polymerizable polyurethane component (PU) obtained by the polyaddition reaction. As a result, the number average molecular weight was 1400.

[GPC measurement conditions]
Measurement device: Advanced Polymer Chromatography (manufactured by Japan Waters)
Column: ACQUITY APCTMXT45 1.7 μm
ACQUITY APCTMXT125 2.5μm
Column temperature: 40°C
Developing solvent: THF (flow rate: 0.5 ml/min)
Detector: Photodiode array detector 254 nm (PDA detector)
(3-2) Evaluation of fluidity The fluidity at 37°C, which is the holding temperature when the second raw material composition is filled into the mold, was evaluated by measuring it according to the following procedure. That is, the second raw material composition was filled into a hole of a sample table having a hole with a diameter of 9 mm and a depth of 5 mm, the surface was flattened, and the sample was shielded from light. Next, after leaving it at 37°C for 2 minutes, a pressure-sensitive rod with a diameter of 5 mm was compressed and inserted into the hole filled with the second raw material composition at a speed of 120 mm/min using a Sun Rheometer (Sun Scientific Co., Ltd.) to a depth of 2 mm. The maximum load (Kg) at this time was measured and evaluated. As a result, the maximum load at 37°C was 3.2 (kg).

(4) Polymerization and curing step The obtained second raw material composition was vacuum degassed at 37°C, poured into a mold (length 12 mm × width 18 mm × thickness 14 mm), and radically polymerized at 120°C for 18 hours under nitrogen pressure (0.3 MPa) to obtain a polyurethane composite material in which a filler was dispersed in a polyurethane resin matrix.

(5) Evaluation of polyurethane composite material (cured product) The obtained polyurethane composite material was evaluated for bending strength, underwater bending strength, and water resistance. The evaluation methods and results are shown below.

[Flexural strength _BSd ]
The polyurethane composite material (cured product) obtained using a mold (length 12 mm x width 18 mm x thickness 14 mm) was cut out with a low-speed diamond cutter (manufactured by Buehler), and then polished with #2000 waterproof abrasive paper to prepare five rectangular columnar test pieces (thickness: about 1.2 mm x width: about 4.0 mm x length: 14.0 mm). Next, a three-point bending test was performed on each test piece using an autograph (manufactured by 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 (actual value, mm): W of the test piece, and the thickness (actual value, mm): B of the test piece, according to 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 314 MPa.

[Underwater bending strength BS _W ]
Five test pieces were prepared in the same manner as described in the [Bending 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 the moisture adhering to the surface was removed, and a three-point bending test was performed under the same test conditions as described in the [Bending strength] section, and the bending load at the maximum point of the test pieces 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 291 MPa.

[Retention rate (water resistance)]
The water resistance retention rate, which is an index of the hardened body, is calculated by the following formula:
Retention rate (%) = 100 × BS _W / BS _d
In this example, the retention rate was 93%, and it was confirmed that the sample had high water resistance.

Examples 2 to 3, Comparative Examples 1 to 3
A polyurethane-based composite material was produced in the same manner as in Example 1, except that the raw materials and the amounts used were changed as shown in Table 1, and the second raw material composition and the polyurethane-based composite material were evaluated. The results are shown in Table 3.

Examples 4 to 5, Comparative Examples 4 to 5
A first raw material composition was prepared in the same manner as in Example 1, except that the radical polymerizable monool (A2) was not added, and the amounts of (A1) and (C) added were changed as shown in Table 2. Next, a second raw material composition was prepared in the same manner as in Example 1, except that in the second raw material composition preparation step, the types and amounts of (B1) and (B2) shown in Table 2 were mixed in advance and then added to the first raw material composition, and the obtained second raw material composition was evaluated.
In Table 2, "radical polymerizable" is expressed as "polymerizable." In Table 2, "T _NCO /T _OH " means the ratio of the total number of moles of isocyanate groups in (B1) and (B2): T _NCO to the total number of moles of hydroxyl groups in (A1): T _OH , and "B2/B1 molar ratio" means the molar ratio of (B2) to 1 mole of (B1).
Thereafter, polymerization and curing were carried out in the same manner as in Example 1, and the obtained cured product (polyurethane-based composite material) was evaluated. The evaluation results of the second raw material composition and the polyurethane-based composite material are shown in Table 3.

Claims (6)

A method for producing a polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure, using as raw materials a radically polymerizable diol (A1) made of a diol compound having a radically polymerizable group; a diisocyanate (B1) made of a diisocyanate compound; a non-polyaddition monomer (C) made of a non-polyaddition reactive polymerizable monomer having a radically polymerizable group in the molecule; a filler (D) made of an inorganic filler; and an initiator (E) made of a thermal radical polymerization initiator; and a radically polymerizable monool (A2) made of a monool compound having a radically polymerizable group, or a radically polymerizable monoisocyanate (B2) made of a monoisocyanate compound having a radically polymerizable group, the method comprising the steps of:
a first raw material composition preparation step of preparing a first raw material composition containing the radical polymerizable diol (A1), the non-polyaddition monomer (C), and the filler (D);
a second raw material composition preparation step of mixing the first raw material composition with the diisocyanate (B1) and subjecting them to a polyaddition reaction to form a radically polymerizable polyurethane component (PU) composed of a polyurethane component having a radically polymerizable group, and preparing a second raw material composition containing the radically polymerizable polyurethane component (PU), the non-polyaddition monomer (C), the filler (D) and the initiator (E);
a polymerization/curing step of heating the second raw material composition to carry out radical polymerization to crosslink the radically polymerizable polyurethane component (PU) to obtain the polyurethane composite material,
In the second raw material composition preparation step,
The polyaddition reaction is
(1) in the presence of 0.2 to 0.7 mol of the radically polymerizable monol (A2) relative to 1 mol of the radically polymerizable diol (A1), such that the ratio of the total number of moles of the isocyanate groups of the diisocyanate (B1) to the total number of moles of the hydroxyl groups of the radically polymerizable monol (A2) and the radically polymerizable diol (A1): _TOH : T _NCO / _{T OH is} 0.9 to 1.1, or (2) in the presence of 0.2 to 0.7 mol of the radically polymerizable monoisocyanate (B2) relative to 1 mol of the _diisocyanate (B1), such that the ratio of the total number of moles of the hydroxyl groups of the radically polymerizable diol (A1) to the total number of moles of the isocyanate groups of the radically polymerizable monoisocyanate (B2) and the diisocyanate _{(B1): T NCO /} T _{The OH} is adjusted to 0.9 to 1.1.
thereby forming the radically polymerizable polyurethane component (PU) having a number average molecular weight of 1000 to 2000,
In the first raw material composition preparation step and the second raw material composition preparation step, the first raw material composition and the second raw material composition are prepared so that the content of the non-polyaddition monomer (C) contained in the second raw material composition is 5 mass% or more and less than 20 mass% of the total mass of the raw materials (A1), (B1), (C), and (A2) or (B2) expressed in terms of the amount of raw materials used in the polyaddition reaction.
4. A method for producing the polyurethane composite material, comprising: The method for producing a polyurethane composite material according to claim 1, wherein in the first raw material composition preparation step, a first raw material composition further containing the radically polymerizable monool (A2) is prepared, and in the second raw material composition preparation step, the polyaddition reaction is carried out in the coexistence of the radically polymerizable monool (A2). The method for producing a polyurethane composite material according to claim 1, characterized in that in the first raw material composition preparation step, a first raw material composition not containing the radical polymerizable monool (A2) is prepared, and the radical polymerizable monoisocyanate (B2) is mixed with the first raw material composition together with the diisocyanate (B1), thereby carrying out the polyaddition reaction in the second raw material composition preparation step in the presence of the radical polymerizable monoisocyanate (B2). The method for producing a polyurethane composite material according to claim 1, characterized in that the radically polymerizable diol compound (A1) is a diol compound in which the number of atoms constituting the main chain in the divalent organic residue interposed between two hydroxyl groups contained in the molecule is 2 to 4. A polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure, obtained by the method for producing a polyurethane composite material described in claim 1. A method for producing a dental cutting material comprising a molded body of a polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin having a crosslinked structure, comprising:
A method for producing a material for dental cutting, comprising the method for producing the polyurethane composite material according to claim 1, characterized in that the polymerization and curing steps are carried out in a molding die.