JP2024157802A - Polyurethane composite material and its manufacturing method, manufacturing method of molded body made of said polyurethane composite material, and material for dental cutting - Google Patents

Abstract

To provide a method for efficiently producing a polyurethane composite material with excellent strength, water resistance, and uniformity.SOLUTION: A radical-polymerizable raw material composition includes a urethane bond and an amide bond within a polyurethane component (A) obtained by the polyaddition reaction of a diol compound (a1) with one or more radical-polymerizable groups; a dicarboxylic acid compound (a3); and a diisocyanate compound (a2), has a number average molecular weight of 1500-5000, and includes (B) a non-polyadditive-radical-polymerizable monomer, (C) a heat radical polymerization initiator and (D) a filler. The radical-polymerizable raw material composition is radically polymerized and cured.SELECTED DRAWING: None

Description

The present invention relates to a polyurethane composite material and a method for producing the same, a method for producing a molded article made of the polyurethane composite material, and 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 uses a cutting machine to produce crown restorations. 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 for dental crowns, and when used for molar crowns or bridges, higher strength is required. However, current cutting materials are based on (meth)acrylic resin, and the strength limitations are an issue.

In contrast, polyurethane resins are generally known to have high strength, and are being considered for use as dental materials.

For example, Patent Document 1 describes a polyurethane composite material that 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 (hereinafter, a polyurethane composite material into which a crosslinked structure has been introduced in this way will also be referred to as a "crosslinked structure-introduced polyurethane composite material") and a method for producing the same.

That is, Patent Document 1 describes that a polyurethane composite material is manufactured by using as 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 radical polymerizable monomer"); a radical polymerization initiator (C); and a filler (D), polyadding a1 and a2 to form a polyurethane component (A) of a specific molecular weight, and then reacting the radical polymerizable group contained in (A) with (B) to introduce a crosslinked structure, which is uniform throughout, has excellent strength and water resistance, and is suitable as a material for dental cutting.

WO2021/153446

However, the present inventors further investigated the method for producing a polyurethane composite material described in Patent Document 1 and found that when a "radical polymerizable raw material composition containing the polyurethane component (A), the polymerizable monomer (B), the radical polymerization initiator (C), and the filler (D)" which is a composition in a state before the radical polymerizable group contained in (A) is reacted with (B) is poured into a mold of a predetermined shape and radical polymerization is performed to produce a polyurethane composite material, the radical polymerizable raw material composition becomes sticky and tacky to containers, tools, jigs, etc., and this may reduce operability.

If the radically polymerizable raw material composition is sticky to containers, tools, jigs, etc., it takes time to handle the radically polymerizable raw material composition, which results in a problem of reduced productivity of the polyurethane composite material.

In addition, in the polyurethane composite material described in Patent Document 1, 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 a1, a2, 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 content of the polyurethane component in the matrix resin 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 the matrix resin of a crosslinked polyurethane composite material, not only can high strength (derived from the polyurethane structure) be expected, but if a crosslinked polyurethane composite material with a polyurethane component content of more than 80% by mass can be produced and the existence of a region where uniformity and water resistance are well maintained is confirmed, 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 aims to provide a method for improving the stickiness of the radically polymerizable raw material composition, and for efficiently producing a polyurethane composite material, as well as for producing a crosslinked polyurethane composite material having a polyurethane component content of more than 80% by mass, and ultimately to provide a crosslinked polyurethane composite material having a polyurethane component content of more than 80% by mass, which is uniform, has excellent strength, and is water-resistant.

The present invention is intended to solve the above-mentioned problems. A first aspect of the present invention is a polyurethane composite material having a filler dispersed in a matrix made of a polyurethane resin,
the polyurethane resin has a number average molecular weight of 1,500 to 5,000, and has a crosslinked structure formed by radical polymerization of a radical polymerizable group of a polyurethane component having a radical polymerizable group and an amide bond in the molecule and a radical polymerizable monomer;
The proportion of the polyurethane component in the polyurethane-based resin is 20% by mass to 95% by mass.
The polyurethane composite material of the present invention is characterized in that:

A second aspect of the present invention is a method for producing the polyurethane composite material of the present invention, comprising the steps of:
a step of preparing a radically polymerizable raw material composition, the step of preparing a radically polymerizable raw material composition comprising: a polyurethane component (A) having a number average molecular weight of 1,500 to 5,000 and having a radically polymerizable group and an amide bond in the molecule; a polymerizable monomer (non-polyaddition type radically polymerizable monomer) (B) which does not undergo a polyaddition reaction with either a diol compound or a diisocyanate compound; a thermal radical polymerization initiator (C); and a filler (D);
a curing step of heating and curing the radically polymerizable raw material composition;
Including,
When the content of the polyurethane component (A) contained in the radical polymerizable raw material composition is Ar (parts by mass) and the content of the polymerizable monomer (B) is Br (parts by mass),
Formula: Rr (mass%) = {Br/(Ar+Br)}×100
The polymerizable monomer blending ratio Rr defined by is 5 to 80 mass%.
The present invention relates to a method for producing a polyurethane composite material.

In the method for producing a polyurethane composite material of the above aspect (hereinafter also referred to as the "composite material production method of the present invention"), the radical polymerizable raw material composition preparation step comprises:
a diol compound (a1) having one or more radically polymerizable groups (hereinafter also referred to as "radical polymerizable diol"); a dicarboxylic acid compound (a3) having two carboxyl groups and no functional group involved in a polyaddition reaction other than the two carboxyl groups, and in a divalent organic residue interposed between two OH groups derived from the two carboxyl groups, the atomic row connecting the carbon atoms at both ends in a single row has the smallest number of constituent atoms of 2 to 10 constituent atoms (hereinafter also referred to as "specific dicarboxylic acid"); 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 (a1) or a diisocyanate compound; a thermal radical polymerization initiator (C); and a filler (D); a second raw material composition preparation step of mixing the first raw material composition with a diisocyanate compound (a2) to cause a polyaddition reaction between the diol compound (a1) and the dicarboxylic acid compound (a3) and the diisocyanate compound (a2) to form the polyurethane component (A) and prepare a second raw material composition comprising the polyurethane component (A), the polymerizable monomer (B); a thermal radical polymerization initiator (C); and a filler (D), and which may contain at least one selected from the group consisting of unreacted diol compound (a1), unreacted dicarboxylic acid compound (a3), and unreacted diisocyanate compound (a2);
Including,
A step of converting the second raw material composition into the radical polymerizable raw material composition,
When the contents (parts by mass) of the respective components contained in the second raw material composition are respectively defined as the content of the polyurethane component (A): Ar, the content of the polymerizable monomer (B): Br, the content of the diol compound (a1): a1r, the content of the diisocyanate compound (a2): a2r, and the content of the dicarboxylic acid compound (a3): a3r,
Formula: Rr'={Br/(a1r+a2r+a3r+Ar+Br)}×100
The polymerizable monomer blending ratio Rr' defined by is 5 to 80 mass%.
It is preferred.

In the above-mentioned preferred embodiment of the composite material manufacturing method of the present invention,
(1) in the first raw material composition, the ratio of M a3 to the total content (moles) of the diol compound (radical polymerizable diol) (a1): M _a1 and the content (moles) of the dicarboxylic acid compound (specific dicarboxylic acid) ( _a3 ): _{M a3} : M _a3 / (M _a1 + M _a3 ) is 0.01 to _0.5 ;
(2) The content ratio of the filler (D) in the second raw material composition is 60% by mass to 80% by mass;
(3) The polymerizable monomer (non-polyaddition-type radically polymerizable monomer) (B) includes a polymerizable monomer that has a (meth)acrylate group, does not have a hydroxyl group, an amino group, a carboxy group, an isocyanate group, or a mercapto group in the molecule, and is a liquid at 25° C.;
(4) The polymerizable monomer (non-polyaddition-type radically polymerizable monomer) (B) contains a polymerizable monomer represented by the following structural formula (1):

In the structural formula (1), R ¹¹ and R ¹² are a hydrogen atom or a methyl group, and n ₁ is an integer of 1 to 10.

Or, (5) the diol compound (a1) is preferably a diol compound in which the number of constituent atoms in the atomic row that connects the carbon atoms at both ends in a single row is 2 to 8 in a divalent organic residue that is interposed between two hydroxyl groups (OH groups) contained in the diol compound.

A third aspect of the present invention is a method for producing a molded article made of the polyurethane composite material of the present invention obtained by the composite material production method of the present invention according to the above-mentioned preferred embodiment, comprising the steps of:
the curing step is performed at a 10-hour half-life temperature _T10 of the thermal radical polymerization initiator (C) of 60° C. or higher, and 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 (C), the second raw material composition is filled into a mold, and then the composition is heated to a temperature 10° C. lower than the _T10 of the thermal radical polymerization initiator (C) to a temperature 25° C. higher than the _T10 to perform radical polymerization, thereby obtaining a polyurethane composite material molded body;
The present invention relates to a method for producing a polyurethane composite material molded article (hereinafter, also referred to as the "molded article production method of the present invention").

Furthermore, the fourth aspect of the present invention is a material for dental cutting that is made of the polyurethane composite material of the present invention.

The present invention provides a polyurethane composite material that is excellent in strength, water resistance, and uniformity, similar to the polyurethane composite material described in Patent Document 1, and can be suitably used as a material for dental cutting. In particular, the polyurethane composite material of the present invention, which has a polyurethane component content of more than 80% by mass, can have a higher strength than the polyurethane composite material described in Patent Document 1.

Furthermore, according to the composite manufacturing method and molded article manufacturing method of the present invention, it is possible to efficiently manufacture the polyurethane composite material and molded articles thereof having the above-mentioned characteristics of the present invention. In particular, the second raw material composition used in the composite manufacturing method of the present invention not only has improved fluidity by heating to a temperature at which polymerization does not occur, but is also less likely to become sticky, so that in the molded article manufacturing method of the present invention using this composition, not only is it possible to fill the mold, but the operability during this process is also good.

This figure is a schematic diagram for explaining the estimated mechanism of the effect of the present invention, where (A) shows the state of interaction between the polyurethane component in Patent Document 1 and the surface of a container, etc., and (B) shows the state of interaction between the polyurethane component into which an amide bond has been introduced and the surface of a container, etc. In the figure, _R1 represents a divalent group derived from the diisocyanate (a2), _R2 represents a divalent group derived from the radically polymerizable diol (a1), and _R3 represents a divalent group derived from the specific dicarboxylic acid compound (a3).

1. Background of the invention and summary of the present invention As described above, in the polyurethane composite material described in Patent Document 1, in order to maintain good uniformity, the ratio of the polyurethane component in the resin component (also simply referred to as the "polyurethane content") cannot be increased beyond 80 mass%, but the reason for this is not particularly described in Patent Document 1. Therefore, in order to solve the above problem, the present inventors first investigated the reason.

the result,
(1) In a crosslinked polyurethane composite material, a radically polymerizable raw material composition (second raw material composition) containing the radically polymerizable polyurethane component (A), the non-polyaddition reactive radically polymerizable monomer (B), a radical polymerization initiator (C) and a filler (D) is polymerized and cured by radical polymerization to obtain a molded product having a desired shape, which is then processed as necessary for use. However, when the polyurethane content exceeds 80% by mass, the raw material composition becomes very hard and has almost no fluidity, and in some cases, the non-polyaddition reactive monomer may be unevenly distributed (rather than uniformly distributed) in the composition.
(2) A molded article of a uniform crosslinked polyurethane composite material can be obtained by heating the radically polymerizable raw material composition to a temperature at which radical polymerization does not substantially occur.
(3) However, even in this case, the stickiness problem is not solved, and (4) it has been found that high water resistance can be maintained so long as the polyurethane content is 95% by mass or less.

Therefore, in order to solve the stickiness problem, further studies were conducted to suppress the stickiness of the radically polymerizable raw material composition. In other words, it was thought that the cause of the "stickiness" was due to the relatively large amount of (B) contained in the radically polymerizable raw material composition, which increased the fluidity of the polyurethane component (A), making it easier for hydrogen bonds to be formed between the urethane bonds contained in the component and the hydroxyl groups present on the surfaces of containers, instruments, jigs, etc., and a method for suppressing the generation of the hydrogen bonds was investigated. As a result, it was discovered that the "stickiness" can be suppressed by introducing an amide bond into the molecule in the presence of a dicarboxylic acid compound when preparing the polyurethane component (A) by polyaddition of the radically polymerizable diol (a1) and the diisocyanate (a2). This led to the completion of the present invention.

In the present invention, for example, when the diisocyanate (a2) and the radically polymerizable diol compound (a1) are reacted to obtain "a polyurethane component (A) having a number average molecular weight of 1500 to 5000 and having a radically polymerizable group in the molecule," the reaction is carried out in the presence of a dicarboxylic acid compound (specific dicarboxylic acid) (a3) that has two carboxylic acids, and in which the number of atoms constituting the main chain in the divalent organic residue intervening between the OH groups derived from the two carboxylic acids contained in the molecule is 10 or less, and that does not have any functional group involved in a polyaddition reaction other than the two carboxylic acids, thereby introducing an amide bond into the main chain of the polyurethane component (A), thereby eliminating the stickiness problem, and by heating the radically polymerizable raw material composition (second raw material composition) to an appropriate temperature as necessary to increase the fluidity, mold filling is made possible, and a uniform matrix resin with a polyurethane content in the range of 20 to 95% by mass can be obtained.

The reason why the stickiness problem is solved is not entirely clear, but it is speculated that, as shown in FIG. 1(A), in the polyurethane component of Patent Document 1, the carbonyl group of the urethane bond in the molecule forms a hydrogen bond with the hydroxyl group on the surface of the container, tool, jig, etc., causing stickiness, whereas when the dicarboxylic acid compound (a3) is used to introduce an amide bond into the molecule (so as to replace a part of the urethane bond), as shown in FIG. 1(B), a hydrogen bond is formed (intramolecularly) between two adjacent amide bonds, and the number of hydrogen bonds formed with the hydroxyl group on the surface of the container, etc. is reduced.

The polyurethane composite material of the present invention is a polyurethane composite material in which a filler is dispersed in a matrix made of a polyurethane resin, and the polyurethane resin has a crosslinked structure formed by radical polymerization of a radically polymerizable group of a polyurethane component having a number average molecular weight of 1500 to 5000 and having a radically polymerizable group and an amide bond in the molecule and a radically polymerizable monomer, and the proportion of the polyurethane component in the polyurethane resin is 20% by mass to 95% by mass. The structure of the matrix made of a polyurethane resin, particularly the microstructure including the crosslinked structure, depends on the manufacturing method, and it is very difficult to specify this by analysis or the like. For this reason, the above-mentioned specification was performed.

The polyurethane composite material of the present invention is a material produced by the composite manufacturing method of the present invention, and is provided as a molded body obtained by the molded body manufacturing method of the present invention. Therefore, the composite manufacturing method and molded body manufacturing method of the present invention will be described in detail below.

In this specification, unless otherwise specified, the expression "x~y" using the numerical values x and y means "greater than or equal to x and less than or equal to y." In such expressions, when a unit is assigned 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. Composite manufacturing method of the present invention The composite manufacturing method of the present invention is a method for producing the polyurethane composite material of the present invention, comprising the steps of:
a step of preparing a radically polymerizable raw material composition, the step of preparing a radically polymerizable raw material composition comprising: a polyurethane component (A) having a number average molecular weight of 1,500 to 5,000 and having a radically polymerizable group and an amide bond in the molecule; a polymerizable monomer (non-polyaddition type radically polymerizable monomer) (B) which does not undergo a polyaddition reaction with either a diol compound or a diisocyanate compound; a thermal radical polymerization initiator (C); and a filler (D);
a curing step of heating and curing the radically polymerizable raw material composition;
Including,
When the content of the polyurethane component (A) contained in the radical polymerizable raw material composition is Ar (parts by mass) and the content of the polymerizable monomer (B) is Br (parts by mass),
Formula: Rr (mass%) = {Br/(Ar+Br)}×100
The polymerizable monomer blending ratio Rr defined by the following formula is set to 80% by mass or less and 5% by mass or more.
It is characterized by:

Here, the polyurethane component (A) is not particularly limited as long as it satisfies the above conditions, but it is preferably produced by mixing a radically polymerizable diol (a1), a specific dicarboxylic acid compound (a3) and a diisocyanate (a2) and subjecting the radically polymerizable diol (a1) and the specific dicarboxylic acid (a3) to a polyaddition reaction with the diisocyanate (a2).

Furthermore, the radical polymerizable raw material composition preparation step
a first raw material composition preparation step of preparing a first raw material composition including: a radically polymerizable diol (a1); a specific dicarboxylic acid compound (a3); a non-polyaddition type radically polymerizable monomer (B); a thermal radical polymerization initiator (C); and a filler (D);
a second raw material composition preparation step of mixing the first raw material composition with a diisocyanate (a2) to polyaddition-react the radically polymerizable diol (a1) and the specific dicarboxylic acid (a3) with the diisocyanate (a2) to form a polyurethane component (A) having a number average molecular weight of 1,500 to 5,000 and having a radically polymerizable group and an amide bond in the molecule, thereby preparing a second raw material composition comprising the polyurethane component (A), the non-polyaddition-type radically polymerizable monomer (B); a thermal radical polymerization initiator (C); and a filler (D), and which may contain at least one selected from the group consisting of unreacted radically polymerizable diol (a1), unreacted specific dicarboxylic acid (a3), and unreacted diisocyanate (a2);
a curing step of heating and curing the second raw material composition;
Including,
When the contents (parts by mass) of the respective components contained in the second raw material composition are respectively defined as the content of the polyurethane component (A): Ar, the content of the non-polyaddition-type radically polymerizable monomer (B): Br, the content of the radically polymerizable diol (a1): a1r, the content of the diisocyanate (a2): a2r, and the content of the specific dicarboxylic acid (a3): a3r,
Formula: Rr=100×Br/[a1r+a2r+a3r+Ar+Br]
It is preferable that the polymerizable monomer blending ratio Rr defined by the following formula is 80 mass % or less and 5 mass % or more.

The following provides a detailed explanation of the various raw materials and steps used in the manufacturing method of the present invention, focusing on the preferred embodiment described above.

2. Various raw materials 2-1. Polyurethane component (A)
The polyurethane component (A) is a polyurethane component having a number average molecular weight of 1,500 to 5,000 and having a radical polymerizable group and an amide bond in the molecule.

The number average molecular weight of the polyurethane component (A) means the number average molecular weight in terms of polystyrene determined by GPC (gel permeation chromatography) measurement. The number average molecular weight of the polyurethane component (A) in the second raw material composition can be determined by adding a solvent such as THF (tetrahydrofuran) to the second 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. The measurement can be performed using an ADVANCED POLYMER CHROMATOGRAPHY (manufactured by Nihon Waters) under the following measurement conditions.

[Measurement conditions]
Measurement device: ADVANCED POLYMER CHROMATOGRAPHY (manufactured by Nihon Waters)
Column: ACQUITY APC ^™ XT 45 1.7 μm
ACQUITY APC ^TM XT 125 2.5μm
Column temperature: 40°C
・Developing solvent: THF (flow rate: 0.5 ml/min)
Detector: Photodiode array detector 254 nm (PDA detector).

The polyurethane component (A) must have a number average molecular weight of 1500 to 5000. By setting the number average molecular weight to 1500 or more, a polyurethane composite material having sufficient strength can be obtained. In addition, according to the study by the present inventors, it is practically impossible or extremely difficult to obtain a polyurethane component (A) having a number average molecular weight exceeding 5000. In addition, if the number average molecular weight is smaller within the range of 1500 to 5000, the polyurethane component (A) can be more reliably prevented from precipitating in the second raw material composition described below, making it easier to carry out uniform radical polymerization. From the viewpoint of achieving a good balance between the fluidity of the second raw material composition and the strength of the polyurethane composite material, the number average molecular weight is preferably 1500 to 3500, and more preferably 2000 to 3000.

In addition, the polyurethane component (A) having a radical polymerizable group and an amide bond in the molecule can be confirmed by, for example, infrared spectroscopy, which shows absorption attributable to the radical polymerizable group and the amide bond. The amounts of these can also be analyzed from the absorption amount. However, from the viewpoint of easy control of these amounts, it is preferable to use a product produced by mixing a radical polymerizable diol (a1), a specific dicarboxylic acid compound (a3) and a diisocyanate (a2) and polyaddition-reacting the radical polymerizable diol (a1) and the specific dicarboxylic acid (a3) with the diisocyanate (a2). The polyaddition reaction between the diisocyanate compound (a2) and the radically polymerizable diol (a1) and the polyaddition reaction between the diisocyanate compound (a2) and the specific dicarboxylic acid compound (a3) both proceed quantitatively, and therefore, by controlling the value of M _a3 /(M _a1 + M _a3 ), it is possible to control the (average) quantitative ratio of polyurethane bonds and amide bonds contained in the molecule of the polyurethane component (A) and the (average) content of radically polymerizable groups.

From the viewpoint of effectiveness, the ratio of the amount of radical polymerizable diol (a1) to the specific dicarboxylic acid compound (a3) is preferably such that M _a3 / (M _a1 + M a3 ) is 0.01 to 0.5 when the amount (mol) of the radical polymerizable diol compound (a1) used is M _a1 and the amount (mol) of the specific dicarboxylic acid compound (a3) used is M _a3 . If the value of M _a3 / (M _a1 + _{M a3} ) exceeds 0.5, the content of amide bonds in the polyurethane component increases, and the radical polymerizable raw material composition (second raw material composition) is no longer in a paste state but becomes powder, making molding difficult. In addition, if the value is less than 0.01, the number of amide bonds in the polyurethane component decreases, making it difficult to suppress stickiness. It is particularly preferable that the value of _{M a3} / (M _a1 + M _a3 ) is 0.01 to 0.3, particularly 0.1 to 0.3.

The amount (moles) of the diisocyanate compound (a2) used: M _a2 is not particularly limited as long as it is about 1 mol/mol, expressed as {M _a2 /(M _a1 +M _a3 )}, but is generally preferably about 0.9 to 1.2 mol/mol, and particularly preferably 1.0 to 1.1 mol/mol.

The radically polymerizable diol (a1), specific dicarboxylic acid compound (a3), and diisocyanate (a2) used as raw materials for polyurethane component (A) are described below.

2-2. Radical polymerizable diol (a1)
The radically polymerizable diol (a1) is a compound that serves as a raw material for forming the polyurethane component (A). Two hydroxyl groups in (a1) and an isocyanate group in the diisocyanate compound (a2) undergo a polyaddition reaction to form a urethane bond in the polyurethane component (A).

As the radically polymerizable diol (a1), any compound having at least one radically polymerizable group and two hydroxyl groups in the molecule can be used without any particular restrictions. 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.

The diol compound has a radical polymerizable group, which introduces the radical polymerizable group into the main chain of the polyurethane molecule formed by the polyaddition reaction. During the radical polymerization in the curing process, the radical polymerizable groups in the polyurethane component (A) react with each other, or with the radical polymerizable groups in the polyurethane component (A) and the non-polyaddition radical polymerizable monomer (B) to form bonds, resulting in crosslinks. This improves the water resistance of the polyurethane composite material, which is the cured product.

From the viewpoint of the strength and water resistance of the polyurethane composite 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.

In addition, in the divalent organic residue between two hydroxyl groups (OH groups) contained in the molecule of the radically polymerizable diol (a1), the number of constituent atoms in the atomic row that connects the carbon atoms (bonded to the OH groups) at both ends in a single row (hereinafter sometimes referred to as the "OH distance") is preferably 2 to 8, more preferably 2 to 6, and particularly 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 molecules of the radically polymerizable polyurethane component (A) obtained by the polyaddition reaction, and the strength of the polyurethane composite material can be increased.

The divalent organic residue between two OH groups is an organic residue having two carbon atoms at both ends to which the OH groups are bonded, and the atomic row with the smallest number of constituent atoms among the atomic rows connecting the carbon atoms at both ends in a row means an atomic row having the two carbon atoms at both ends that forms the basic skeleton of the organic residue, in which the constituent atoms are connected (in a straight chain) by single bonds, double bonds, or triple bonds. If the divalent organic residue has a ring structure, the atomic row with the shorter chain length of the two branched routes corresponds to this, but it is preferable that the divalent organic residue does not include a ring structure.

When two or more types of radically polymerizable diols (a1) are used, the OH distance means 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 value of the OH distance means a value calculated as the sum of the products obtained by multiplying the OH distance: Dx of each radically polymerizable diol compound 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 compound in the total number of moles of the radically polymerizable diol compounds.

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.

2-3. Specific dicarboxylic acid (a3)
The specific dicarboxylic acid (a3) is a compound that serves as a raw material for forming the polyurethane component (A). Two carboxyl groups in (a3) and an isocyanate group in the diisocyanate (a2) undergo a polyaddition reaction to form an amide bond in the polyurethane component (A).

As the specific dicarboxylic acid (a3), any dicarboxylic acid compound can be used without particular restrictions, which has two carboxyl groups in the molecule and no functional groups other than the two carboxyl groups that participate in the polyaddition reaction, and in which, in the divalent organic residue between the two OH groups derived from the two carboxyl groups, the number of constituent atoms in the atomic row that connects the carbon atoms (bonded to the OH groups) at both ends in a single row is 2 to 10 (hereinafter, sometimes referred to as the "dicarboxylic acid OH distance").

Here, the divalent organic residue between the two OH groups derived from the two carboxyl groups is an organic residue having two carbon atoms at both ends to which the OH groups are bonded, and the atomic row with the smallest number of constituent atoms among the atomic rows connecting the carbon atoms at both ends in a row means an atomic row having the two carbon atoms at both ends that constitute the basic skeleton of the organic residue, in which the constituent atoms are connected (in a straight chain) by single bonds, double bonds, or triple bonds, and when the divalent organic residue has a ring structure, the atomic row with the shorter chain length of the two branched routes corresponds to this. For example, when the specific dicarboxylic acid (a3) is adipic acid, the divalent organic residue is -C(=O)-(C-) ₄ -(O=)C-, so the dicarboxylic acid OH distance is 6. In addition, in the case of isophthalic acid, the divalent organic residue is -C(=O)-Ph-(O=)C- and is divided into two routes by the ring structure. However, since -Ph- is an o-phenylene group, the number of constituent atoms in the atomic row of the route with the shorter chain length, 5, becomes the distance between dicarboxylic acid OH groups (incidentally, the number of constituent atoms in the atomic row of the route with the longer chain length is 7).

The distance between the dicarboxylic acid OH groups is preferably 2 to 8, and particularly preferably 2 to 6. By making the distance between the dicarboxylic acid OH groups of the dicarboxylic acid compound (a3) within the above range, amide bonds can be introduced at a high density into the molecules of the polyurethane component (A) obtained by the polyaddition reaction, which not only improves the stickiness suppression of the second raw material composition, but also increases the strength of the polyurethane composite material.

The specific dicarboxylic acid (a3) must not have any functional groups involved in the polyaddition reaction other than the two carboxyl groups (carboxylic acid). Here, not having any functional groups involved in the polyaddition reaction other than the two carboxyl groups is synonymous with (a3) not inhibiting the polyaddition reaction of (a1) and (a2) and not causing any reaction other than the polyaddition reaction between the two carboxyl groups in (a3) and the isocyanate group in (a2). Specifically, it means that the molecule of (a3) does not contain any hydroxyl groups (other than the two hydroxyl groups contained in the two carboxyl groups), amino groups, carboxy groups (other than the two carboxyl groups), isocyanate groups, or mercapto groups.

The dicarboxylic acid OH distance in the case where different types of specific dicarboxylic acid compounds (a3) are used means a value calculated as the average value of two or more types of dicarboxylic acid compounds (a3). Here, when n types of dicarboxylic acid compounds (a3), where n is an integer of 2 or more, are used, the average value of the dicarboxylic acid OH distance means a value calculated as the sum of the products obtained by multiplying the dicarboxylic acid OH distance: CX of each dicarboxylic acid compound (a3) by the molar fraction (mol/mol): MX of each dicarboxylic acid compound (a3), which is defined as the number of moles of each dicarboxylic acid compound (a3) in the total number of moles of the dicarboxylic acid compounds (a3).

Examples of compounds that are suitable for use as the specific dicarboxylic acid (a3) include hexadecafluorosebacic acid, dihydromuconic acid, 2,5-furandicarboxylic acid, 1,3-acetonedicarboxylic acid, adipic acid, 4-cyclohexanedicarboxylic acid, isophthalic acid, and itaconic acid.

2-4. Diisocyanate (a2)
The diisocyanate (a2) is a component for forming the polyurethane component (A), similar to the radically polymerizable diol (a1) and the specific dicarboxylic acid (a3), and the polyurethane component (A) is formed by a polyaddition reaction between them.

As diisocyanate (a2), any compound having two isocyanate groups in one molecule can be used without any particular limitation.

Examples of compounds that can be suitably used as diisocyanate (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, 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, diisocyanate (a2) having a phenyl group in the molecule is preferred from the viewpoints of the fluidity of the resulting second raw material composition and the strength of the resulting polyurethane composite material.

2-5. Non-polyaddition radically polymerizable monomer (B)
The non-polyaddition radical polymerizable monomer (B) is a compound having at least one radical polymerizable group in the molecule, and not undergoing a polyaddition reaction with any of the radical polymerizable group diol compound (a1), the specific dicarboxylic acid (a3), and the diisocyanate (a2). Here, not undergoing a polyaddition reaction with any of (a1) to (a3) means that the monomer does not have any group capable of undergoing a polyaddition reaction with (a2) or any group capable of undergoing a polyaddition reaction with (a1) or (a2) in the molecule. Specifically, it means that the monomer does not contain a hydroxyl group, an amino group, a carboxy group, or a mercapto group (the former group), or an isocyanate group (the latter group) in the molecule.

The radical polymerizable group possessed by the non-polyaddition radical polymerizable monomer (B) may be the same as the radical polymerizable group possessed by the radical polymerizable diol (a1). Among them, a (meth)acrylate group and/or a (meth)acrylamide group is preferred, and a group having the same molecular structure as the radical polymerizable group possessed by the radical polymerizable diol (a1) is also preferred.

From the viewpoint of ease of forming crosslinks, the number of radically polymerizable groups contained in the molecule of the non-polyaddition radically polymerizable monomer (B) is preferably 2 to 6, and more preferably 2 to 4. By making the number of radically 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 radically polymerizable groups 6 or less, it becomes easier to suppress shrinkage during curing. Furthermore, it is preferable that the non-polyaddition radically polymerizable monomer (B) is a liquid at room temperature (i.e., 25°C).

The viscosity of the non-polyaddition radically polymerizable monomer (B) is not particularly limited, but is preferably in the range of 1 mPa·s to 1000 mPa·s at room temperature, and more preferably in the range of 1 mPa·s to 100 mPa·s.

From the viewpoint of facilitating dispersion of the polyurethane component (A), the non-polyaddition radical polymerizable monomer (B) preferably contains a polymerizable monomer represented by the following structural formula (1):

In the structural formula (1), R ¹¹ and R ¹² represent a hydrogen atom or a methyl group, and n ₁ represents an integer of 1 to 10, preferably an integer of 1 to 3.

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

2-6. Thermal radical polymerization initiator (C)
The thermal radical polymerization initiator (C) has a function of initiating a radical polymerization reaction, and by reacting and bonding radically polymerizable groups with each other, the second raw material composition is polymerized and cured, and a crosslinking point is formed. In the manufacturing method of the present invention, the thermal radical polymerization initiator (C) is used in order to heat and polymerize the polyurethane-based polymerizable composition. There is no particular restriction on the use of the thermal radical polymerization initiator, but in order to prevent radical polymerization from occurring in the second raw material composition heated to a predetermined temperature, it is preferable to use a thermal polymerization initiator having a 10-hour half-life temperature: T ₁₀ of 60° C. or higher. The upper limit temperature of T ₁₀ is not particularly limited, but is usually 150° C. From the viewpoint of fluidity, etc., it is preferable to use a thermal polymerization initiator having a T ₁₀ in the range of 70 to 120° C., particularly 80 to 100° 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 representing 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 initiators such as azobisbutyronitrile, etc. These thermal polymerization initiators may be used alone or in combination of two or more.

2-7. Filler (D)
The filler (D) is dispersed in the radically polymerizable raw material composition (second raw material composition) to form a polymer of the polyurethane component (A) and the non-polyaddition type radically polymerizable monomer (B). By forming a composite material, it has the function of 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 inorganic fillers such as silica, alumina, titania, zirconia, or composite oxides thereof, glass, etc. 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 composite oxides thereof as the filler (D), and silica or composite oxides thereof are particularly preferable. This is because these inorganic fillers are not likely to dissolve in the oral cavity environment, and their transparency and aesthetics are easy to control.

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. For example, a spherical shape is preferable from the viewpoint of obtaining a polyurethane composite material that is particularly excellent in abrasion resistance, surface smoothness, and gloss retention. In addition, polyurethane composite materials containing spherical fillers (D) dispersed therein are particularly suitable for dental use. The spherical shape here means that the average uniformity obtained in image analysis of images taken with a scanning or transmission electron microscope is 0.6 or more. The average uniformity is more preferably 0.7 or more, and even more preferably 0.8 or more. The average uniformity can be calculated by measuring the long diameter (L) and the short diameter (B) perpendicular to the long diameter (L) for each of N particles (usually 40 or more, preferably 100 or more) in image analysis of images taken with a scanning or transmission electron microscope, determining the ratio (B/L), and dividing the sum (ΣB/L) by N.

From the viewpoints of abrasion resistance, surface smoothness, and gloss durability, the average particle size of 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 multiple 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.

It is preferable to use a filler (D) that has been surface-treated in order to improve the mechanical strength and water resistance of the polyurethane composite material. A silane coupling agent is generally used as the surface treatment agent, and the effect of surface treatment with a silane coupling agent is particularly high for silica-based inorganic particle filler (D). Suitable silane coupling agents include methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and the like.

3. Composition of the radically polymerizable raw material composition (second raw material composition) In the radically polymerizable raw material composition, when the content of the polyurethane component (A) contained in the raw material composition is Ar (parts by mass) and the content of the polymerizable monomer (B) is Br (parts by mass),
Formula: Rr (mass%) = {Br/(Ar+Br)}×100
The polymerizable monomer blending ratio Rr defined by the following formula must be 5 to 80 mass %.

If Rr is less than 5% by mass, it is difficult to obtain a polyurethane composite material with a uniform crosslinked structure, and if it exceeds 80% by mass, it is difficult to obtain a polyurethane composite material with sufficient strength. From the viewpoint of achieving a better balance between maintaining the strength of the polyurethane composite material and obtaining a polyurethane composite material with a uniform crosslinked structure, Rr is preferably 7 to 50% by mass, and particularly preferably 10 to 30% by mass.

In addition, when the radical polymerizable raw material composition is a second raw material composition prepared by mixing the first raw material composition with a diisocyanate compound (a2), (a1) and/or (a3) or (a2) may remain unreacted in the second raw material composition. Therefore, when the contents (parts by mass) of each of the components contained in the second raw material composition are respectively the content of the polyurethane component (A): Ar, the content of the polymerizable monomer (B): Br, the content of the diol compound (a1): a1r, the content of the diisocyanate compound (a2): a2r, and the content of the dicarboxylic acid compound (a3): a3r,
Formula: Rr'={Br/(a1r+a2r+a3r+Ar+Br)}×100
It is preferable that the polymerizable monomer blending ratio Rr′ defined by the following formula is 5 to 80 mass %.

The amount of thermal radical polymerization initiator (C) used may be determined appropriately depending on the type of initiator, but is usually preferably in the range of 0.005% to 5.0% by mass, and more preferably in the range of 0.01% to 3.0% by mass, based on the total mass of (A) and (B) and (a1) to (a3) remaining in the radically polymerizable raw material composition (second raw material composition).

The amount of filler (D) used may be appropriately determined 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% by mass to 80% by mass, more preferably 65% by mass to 75% by mass, expressed in mass % based on the mass of the radically polymerizable raw material composition (second raw material composition) (hereinafter, sometimes simply referred to as "filling rate"). Furthermore, when the polyurethane composite material produced by the method for producing a polyurethane composite material of this embodiment is used as a dental cutting material, the filling rate is more preferably 65% by mass to 75% by mass.
The radically polymerizable raw material composition (second raw material composition) may contain various other additives in addition to the essential components described above. Examples of the various additives include 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.

4. Radically Polymerizable Raw Material Composition Preparation Step The radically polymerizable raw material composition may be prepared by mixing the above-mentioned components to obtain the above-described composition.

When the radically polymerizable raw material composition is a second raw material composition prepared by mixing the first raw material composition with a diisocyanate compound (a2), it is preferable to prepare the second raw material composition through the first raw material composition preparation step and the second raw material composition preparation step described below.

4-1. First raw material composition preparation step In the first raw material composition preparation step, a first raw material composition is prepared, which contains the radical polymerizable diol (a1); the specific dicarboxylic acid (a3); the non-polyaddition type radical polymerizable monomer (B); the thermal radical polymerization initiator (C); and the filler (D).

The amount of each of these components may be determined according to the composition of the intended radically polymerizable raw material composition (second raw material composition) on the premise that the polyaddition reaction between the diisocyanate compound (a2) and the radically polymerizable diol (a1) and the polyaddition reaction between the diisocyanate compound (a2) and the specific dicarboxylic acid compound (a3) proceeds quantitatively. In addition, it is preferable to add the optional component to the first raw material composition. The first raw material composition may further contain a catalyst that promotes the polyaddition reaction as an optional component if necessary, but may not contain a catalyst that promotes the polyaddition reaction. Examples of catalysts that promote the polyaddition reaction include tin octylate and dibutyltin diacetate.

When preparing the first raw material composition, all of the components constituting the first raw material composition may be mixed at once, or a mixture of some of the components constituting the first raw material composition may be prepared, and then the remaining components constituting the first raw material composition may be added and mixed. When preparing the first raw material composition, the method for mixing the components is not particularly limited, and a method using a magnetic stirrer, a mortar and pestle mixer, a planetary mixer, a centrifugal mixer, or the like may be used as appropriate.

Because it is easy to uniformly disperse the filler (D), it is preferable to first mix the radically polymerizable diol (a1), the specific dicarboxylic acid (a3), the non-polyaddition radically polymerizable monomer (B) and the radical polymerization initiator (C), and then add the filler (D) to the resulting mixed composition and mix to prepare the first raw material composition. It is preferable to subject the first raw material composition prepared in this way to a degassing treatment to remove any air bubbles contained therein. As a degassing method, a known method can be used, and any method such as pressurized degassing, vacuum degassing, or centrifugal degassing can be used.

4-2. Second raw material composition preparation step In the second raw material composition preparation step, the first raw material composition obtained in the first raw material composition preparation step is mixed with a diisocyanate compound (a2) to cause a polyaddition reaction between the diol compound (a1) and the dicarboxylic acid compound (a3) and the diisocyanate compound (a2), thereby forming the polyurethane component (A). The amount of the diisocyanate compound (a2) used at this time may be such that the {M _a2 /(M _a1 +M _a3 )} is 0.9 to 1.2 mol/mol, particularly 1.0 to 1.1 mol/mol.

The polyaddition reaction is started by heating the first raw material composition and the diisocyanate (a2) simultaneously or after mixing the first raw material composition and the diisocyanate (a2) as necessary. The polyaddition reaction is carried out so that the radical polymerizable diol compound (a1) and the specific dicarboxylic acid (a3), or the diisocyanate (a2) are substantially consumed by the polyaddition reaction, in other words, until the progress of the polyaddition reaction reaches near the maximum value (saturation value). At this time, it is preferable to carry out the polyaddition reaction at a reaction temperature lower than the 10-hour half-life temperature: T ₁₀ of the thermal radical polymerization initiator (C) contained in the first raw material composition, and it is particularly preferable to carry out the polyaddition reaction at a temperature maintained at 80°C to 20°C lower than T ₁₀ , particularly 70°C to 30°C lower. In addition, in the second raw material composition preparation step, even if the above-mentioned method is adopted, a small amount of radical polymerization reaction is unavoidably caused.

The reaction time varies depending on the reaction temperature. For example, (1) if the reaction temperature is 30°C or higher and lower than 50°C, it is preferably 60 hours or more, and more preferably 72 hours or more; (2) if the heating temperature is 50°C or higher and lower than 80°C, it is preferably 24 hours or more, and more preferably 36 hours or more; and (3) if the heating temperature is 80°C or higher, it is preferably 15 hours or more, and more preferably 24 hours or more. In the cases shown in (1) to (3) above, the upper limit of the heating time is not particularly limited, but from the practical viewpoint of productivity and the like, 120 hours or less is preferable.

When preparing the second raw material composition, the mixing means used to mix the components is not particularly limited, and any known mixing means can be used as appropriate. Examples of such mixing means include a magnetic stirrer, a mortar and pestle mixer, a planetary mixer, and a centrifugal mixer. In order to prevent air bubbles from being mixed into the composition during mixing, the components may be mixed under pressurized and/or vacuum conditions.

In the curing step, the radical polymerizable raw material composition (second raw material composition) is heated and cured. The curing step is preferably carried out by filling a mold with the radical polymerizable raw material composition (second raw material composition), because a molded product having a shape corresponding to the mold shape can be obtained without performing any post-processing such as cutting.

When the radically polymerizable raw material composition (second raw material composition) has fluidity at room temperature, it may be filled into a mold as is and cured by thermal polymerization. However, when Rr (Rr') in the radically polymerizable raw material composition (second raw material composition) is less than 20 mass%, particularly 15 mass% or less, the second raw material composition loses fluidity and becomes in a solid-like state, and in some cases, the non-polyaddition-type radically polymerizable monomer (B), which is a liquid component, separates and is unevenly distributed, thereby reducing uniformity. In such a case, it is preferable to use a thermal radical polymerization initiator (C) having a 10-hour half-life temperature; _T10 of 60°C or higher, fill the radical polymerizable raw material composition (second raw material composition) into a mold while maintaining the temperature at 40°C or higher and at a temperature not higher than 15°C lower than the _T10 of the thermal radical polymerization initiator (C), and then heat the composition to a temperature 10°C lower than the _T10 of the thermal radical polymerization initiator (C) to a temperature 25°C higher than the _T10 to perform radical polymerization, thereby obtaining a polyurethane composite material molded body. In this way, the radical polymerizable raw material composition (second raw material composition) is filled into the mold in a uniform, fluid paste state, and radical polymerization is performed while maintaining uniformity, making it possible to efficiently obtain a molded body made of a polyurethane composite material having a uniform crosslinked structure introduced therein.

From the viewpoint of being able to change the state into a paste more uniformly, it is preferable to use a thermal radical polymerization initiator (C) having a 10-hour half-life temperature: _T10 in the range of 70 to 120° C., particularly 80 to 100° C., and to set the temperature (heating temperature) at which the second raw material composition is held before filling into the mold to 45° C. to a temperature 15° C. lower than _T10 , particularly 50° C. to a temperature 20° C. lower than _T10 . By controlling the temperature within this range, preferably within this range but not exceeding 150° C., polymerization and curing can be carried out at a sufficiently fast rate that is industrially acceptable, while preventing the occurrence of distortion or cracks due to the rapid progress of radical polymerization.

As a method for holding the temperature (heating temperature) at which the radical polymerizable raw material composition (second raw material composition) is to be held before filling the mold, a method of placing the container holding the radical polymerizable raw material composition (second raw material composition) in an atmosphere held at a predetermined temperature, or a method of contacting the container with a heat medium (liquid, plate, or other solid) held at a predetermined temperature, can be suitably adopted in order to avoid localized high temperatures. The time for holding the predetermined temperature may be within a range that does not adversely affect mold filling (due to radical polymerization during the holding period), and is usually within a range of 5 minutes to several hours, preferably 10 to 60 minutes, after the predetermined temperature is reached. By holding the composition at the above temperature, the radical polymerizable raw material composition (second raw material composition) becomes homogeneous without any special operation such as stirring, but stirring may be performed as long as no air bubbles remain inside.

As the mold (forming tool) used in the curing process, any mold having a cavity corresponding to the shape of the desired molded product can be used. There are no particular restrictions on the material, so long as it can withstand the temperature and pressure during radical polymerization, and metal, ceramic, or resin materials can be used. Specifically, molds made of SUS, polypropylene, polyacetal, polytetrafluoroethylene, etc. are preferably used.

As a method for filling the mold with the radically polymerizable raw material composition (second raw material composition), a pressure casting method, a vacuum casting method, etc. can be suitably used. In particular, it is more preferable to use the pressure casting method because it can reliably transfer heat to the radically polymerizable raw material composition (second raw material composition) and can suppress the formation of voids in the hardened body due to air bubbles. There are no limitations on the method of pressurization, and mechanical pressurization or air pressurization can be used.

The radically polymerizable raw material composition (second raw material composition) filled in the mold is heated and polymerized at the temperature described above, and a polyurethane composite material molded body having the desired shape can be obtained.

6. Uses of the Polyurethane Composite Material of the Present Invention The polyurethane composite material of the present invention has water resistance while maintaining high strength even in a hydrophilic environment such as the oral cavity. Because of its high water resistance, the polyurethane composite material of the present invention can be suitably used as a dental prosthesis, particularly by cutting a dental cutting material using a dental CAD/CAM system.

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)
BMOHE: 1,2-bis(3-methacryloyloxy-2-hydroxypropoxy)ethane (OH distance: 8).

(2) Specific dicarboxylic acid (a3)
DCA1: Adipic acid (dicarboxylic acid OH distance: 6)
DCA2: 4-cyclohexanedicarboxylic acid (distance between dicarboxylic acid OH: 6)
DCA3: Isophthalic acid (dicarboxylic acid OH distance: 5)
DCA4: Itaconic acid (dicarboxylic acid OH distance: 4).

(3) Diisocyanate (a2)
XDI: m-xylylene diisocyanate TDI: toluene diisocyanate HDI: hexamethylene diisocyanate.

(4) Non-polyaddition radically polymerizable monomer (B)
1G: Ethylene glycol dimethacrylate 3G: Triethylene glycol dimethacrylate 9G: Polyethylene glycol #400 dimethacrylate A-DOG: Dioxane glycol diacrylate UDMA: 1,6-bis(methacrylethyloxycarbonylamino)-2,2-4-trimethylhexane A-TMPT-3EO: EO-modified trimethylolpropane triacrylate (5) Thermal radical polymerization initiator (C)
PBC: tert-butyl α,α-dimethylbenzyl peroxide (10 hour half-life temperature 120° C.).

(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).

2. Method for Producing Polyurethane Composite Material Examples of the polyurethane polymerizable composition of the present invention and the method for producing a polyurethane composite material 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 (31.2 parts by mass) which is a radical polymerizable diol (a1), 3G (14.3 parts by mass) which is a non-polyaddition radical polymerizable monomer (B), DCA1 (3.7 parts by mass) which is a specific dicarboxylic acid (a3), and PBC (0.3 parts by mass) which is a thermal radical polymerization initiator (C). Next, the first raw material composition was prepared by adding F1 (175.6 parts by mass) and F2 (74.9 parts by mass) which are fillers (D) to this mixed composition and kneading.

(2) Second raw material composition preparation step In a planetary centrifugal mixer containing the entire amount of the obtained first raw material composition, XDI (40.9 parts by mass) as diisocyanate (a2) was added and kneaded. Next, the mixture was left to stand in an incubator at 37°C for 72 hours to carry out a polyaddition reaction, forming a polyurethane component (A) to prepare a second raw material composition.

(3) Evaluation of the second raw material composition (3-1) Measurement of number average molecular weight of polyurethane component (A) (GPC measurement)
1 g of the obtained second raw material composition was weighed into a screw tube bottle, 3.5 ml of THF was added and stirred to obtain a THF 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 through 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 number average molecular weight of the polyurethane component (A) obtained by the polyaddition reaction in terms of polystyrene. As a result, the number average molecular weight was 2800.

[GPC measurement conditions]
Measurement device: ADVANCED POLYMER CHROMATOGRAPHY (manufactured by Nihon Waters)
Column: ACQUITY APC ^™ XT 45 1.7 μm
ACQUITY APC ^TM XT 125 2.5μm
Column temperature: 40°C
・Developing solvent: THF (flow rate: 0.5ml/min)
Detector: Photodiode array detector 254 nm (PDA detector).

(3-2) Evaluation of Sticky Energy for Stainless Steel Materials The second raw material composition was filled into a stainless steel hole having a diameter of 9 mm and a depth of 5 mm, and the surface was flattened and shaded. Then, after leaving it at 80°C for 2 minutes, a stainless steel pressure-sensitive rod having 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 to a depth of 2 mm using a Sun Rheometer (Sun Scientific Co., Ltd.) and held for 1 second. Then, the pressure-sensitive rod was pulled out of the second raw material composition at a speed of 120 mm/min. Then, the maximum negative load [kg] at this time and the distance [m] from the point where the negative load was measured until the load became 0 [kg] were measured, and the sticking energy [J] was calculated from the maximum negative load [kg] and the distance [m] according to the following formula (3).

Equation (3) Stickiness energy [J] = negative maximum load [kg] x 9.8 [m/ ^s2 ] x distance [m]
As a result, the sticking energy of the second raw material composition against the stainless steel material was 80×10 ⁻⁶ [J].
(3-3) Evaluation of stickiness to glass material A glass plate having a thickness of 2 [cm], a length of 20 [cm], and a width of 10 [cm] was left standing at 80 ° C. for 5 minutes using a hot plate, and then 30 [g] of the second raw material composition was uniformly pressed onto the glass plate to a length of 20 [cm] and a width of 10 [cm], and left standing again for 5 minutes. Next, using a polypropylene sheet having a thickness of 0.1 [cm], a length of 3 [cm], and a width of 3 [cm], six different evaluators each performed once to determine how much of the second raw material composition could be recovered in one minute, and the average recovery rate was taken as an evaluation of stickiness to the glass material. The results are shown in Table 2.

Examples 2 to 17, Comparative Examples 1 to 3
The first raw material composition and the second raw material composition were prepared in the same manner as in Example 1, except that the raw materials and the filling rate used in Example 1 were changed as shown in Table 1. The number average molecular weight of the second raw material composition was evaluated in the same manner as in Example 1, and the results are shown in Table 2. The evaluation was performed by changing the temperature during the evaluation of stickiness and the temperature during the evaluation of the recovery rate as shown in Table 2, and the results are shown in Table 2. In the table, "↑" means "same as above."

Claims (10)

A polyurethane composite material having a filler dispersed in a matrix made of a polyurethane resin,
the polyurethane resin has a number average molecular weight of 1,500 to 5,000, and has a crosslinked structure formed by radical polymerization of a radical polymerizable group of a polyurethane component having a radical polymerizable group and an amide bond in the molecule and a radical polymerizable monomer;
The proportion of the polyurethane component in the polyurethane-based resin is 20% by mass to 95% by mass.
The polyurethane composite material is characterized in that A method for producing the polyurethane-based composite material according to claim 1, comprising the steps of:
a step of preparing a radically polymerizable raw material composition, the step of preparing a radically polymerizable raw material composition comprising: a polyurethane component (A) having a number average molecular weight of 1,500 to 5,000 and having a radically polymerizable group and an amide bond in the molecule; a polymerizable monomer (B) which does not undergo a polyaddition reaction with either a diol compound or a diisocyanate compound; a thermal radical polymerization initiator (C); and a filler (D);
a curing step of heating and curing the radically polymerizable raw material composition;
Including,
When the content of the polyurethane component (A) contained in the radical polymerizable raw material composition is Ar (parts by mass) and the content of the polymerizable monomer (B) is Br (parts by mass),
Formula: Rr={Br/(Ar+Br)}×100
The polymerizable monomer blending ratio Rr defined by is 5 to 80 mass%.
A method for producing a polyurethane composite material, comprising: The radical polymerizable raw material composition preparation step includes:
a diol compound (a1) having one or more radically polymerizable groups; a dicarboxylic acid compound (a3) having two carboxyl groups in the molecule and no functional group participating in a polyaddition reaction other than the two carboxyl groups, and in a divalent organic residue interposed between two OH groups derived from the two carboxyl groups, the atomic row having the smallest number of constituent atoms in an atomic row connecting the carbon atoms at both ends in a single row has 2 to 10 constituent atoms; 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 (a1) or a diisocyanate compound; a thermal radical polymerization initiator (C); and a filler (D); a second raw material composition preparation step of mixing the first raw material composition with a diisocyanate compound (a2) to cause a polyaddition reaction between the diol compound (a1) and the dicarboxylic acid compound (a3) and the diisocyanate compound (a2) to form the polyurethane component (A) and prepare a second raw material composition comprising the polyurethane component (A), the polymerizable monomer (B); a thermal radical polymerization initiator (C); and a filler (D), and which may contain at least one selected from the group consisting of unreacted diol compound (a1), unreacted dicarboxylic acid compound (a3), and unreacted diisocyanate compound (a2);
Including,
A step of converting the second raw material composition into the radical polymerizable raw material composition,
When the contents (parts by mass) of the respective components contained in the second raw material composition are respectively defined as the content of the polyurethane component (A): Ar, the content of the polymerizable monomer (B): Br, the content of the diol compound (a1): a1r, the content of the diisocyanate compound (a2): a2r, and the content of the dicarboxylic acid compound (a3): a3r,
Formula: Rr'={Br/(a1r+a2r+a3r+Ar+Br)}×100
The polymerizable monomer blending ratio Rr' defined by is 5 to 80 mass%.
A method for producing a polyurethane composite material according to claim 2. 4. The method for producing a polyurethane composite material according to claim 3, wherein the ratio of M _a3 to the total content (moles) of the diol compound (a1): M _a1 and the content (moles) of the dicarboxylic acid compound ( _a3 ): M _a3 in the first raw material composition: M _a3 /(M _a1 + _{M a3} ) is 0.01 to 0.5. The method for producing a polyurethane composite material according to claim 3, wherein the content of the filler (D) in the second raw material composition is 60% by mass to 80% by mass. The method for producing a polyurethane composite material according to claim 3, wherein the polymerizable monomer (B) includes a polymerizable monomer that has a (meth)acrylate group, does not have a hydroxyl group, an amino group, a carboxy group, an isocyanate group, or a mercapto group in the molecule, and is liquid at 25°C. The polymerizable monomer (B) is represented by the following structural formula (1):

[In the structural formula (1), R ¹¹ and R ¹² are a hydrogen atom or a methyl group, and n1 is an integer from 1 to 10.]
The method for producing the polyurethane composite material according to claim 3, further comprising the step of: The method for producing a polyurethane composite material according to claim 3, wherein the diol compound (a1) is a diol compound in which the number of constituent atoms in the atomic row that connects the carbon atoms at both ends in a single row in a divalent organic residue interposed between two hydroxyl groups contained in the diol compound is 2 to 8. A method for producing a molded article made of the polyurethane composite material according to claim 1 obtained by the method according to claim 3, comprising the steps of:
the curing step is performed at a 10-hour half-life temperature _T10 of the thermal radical polymerization initiator (C) of 60° C. or higher, and 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 (C), the second raw material composition is filled into a mold, and then the composition is heated to a temperature 10° C. lower than the _T10 of the thermal radical polymerization initiator (C) to a temperature 25° C. higher than the _T10 to perform radical polymerization, thereby obtaining a polyurethane composite material molded body;
A method for producing a polyurethane composite material molded article, comprising: A dental cutting material comprising the polyurethane composite material according to claim 1.