Method for producing photocurable composition

Abstract

To provide a method for suppressing agglomeration that occurs when a powder composition containing an α-diketone compound and an amorphous resin powder, which is suitably used as a powder for light-curable powder-liquid denture base backing materials, is stored for a long period of time, and in addition, to provide an efficient method of manufacturing powder-liquid denture base backing materials with high storage stability.SOLUTION: A raw material powder containing an α-diketone compound and an amorphous resin powder is treated at a heat treatment temperature of 40°C or higher and lower than the glass transition point of the amorphous resin, with the result that amorphous resin particles are positively agglomerated and the α-diketone compound is adhered to surfaces of the agglomerated particles by sublimation and coagulation. After that, the agglomerated particles are pulverized, and the obtained powder composition is used as a powder material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a photocurable composition, and more particularly to a method for producing a photocurable composition suitable for use as a photopolymerizable denture base lining material. [Background technology]

[0002] Denture relining materials are used to repair dentures that have become poorly compatible with the patient's oral mucosa, and the most widely known type of denture relining material is a powder-liquid type consisting of a powder material whose main component is resin particles and a liquid material whose main component is a polymerizable monomer. These powder-liquid denture relining materials are prepared by mixing the powder and liquid materials to obtain a paste, which is then applied to the denture, and after ensuring compatibility with the oral mucosa, the material is finally cured. Depending on the type of curing catalyst used, there are two types: chemical polymerization and photopolymerization.

[0003] In other words, in the chemical polymerization type, radicals are generated by the coexistence of a chemical polymerization initiator and a polymerizable monomer, resulting in polymerization and hardening. Polymerization and hardening typically occurs simply by mixing a powder and a liquid material. In contrast, in the photopolymerization type, radicals are generated by irradiating a photopolymerization initiator with light (hereinafter simply referred to as "active light"), which excites the photopolymerization initiator, resulting in polymerization and hardening. Typically, the paste obtained after mixing the powder and liquid materials is applied to the denture, and after ensuring a proper fit to the oral cavity, final hardening is achieved by irradiating the denture with light using a dedicated light irradiator outside the oral cavity. Therefore, in the photopolymerization type, the denture base relining material is removed from the oral cavity before final hardening, while still in a rubber-elastic state, allowing for painless treatment even in cases with undercuts.

[0004] In light-polymerizing denture base lining materials, in order to increase the stability of the material during storage, a combination of an α-diketone compound and a tertiary amine compound is generally used as the photopolymerization initiator, and both are added separately to the powder material and the liquid material.

[0005] Known examples of such photopolymerization type denture base lining materials include a liquid material comprising (a) a polymerizable monomer, (d) a tertiary amine compound, and (e) an α-hydroxycarboxylic acid having an acid dissociation constant of 3.0 or more in water (25°C) and two or more carbonyl groups in the same molecule; (b) resin particles having a weight-average molecular weight of 30,000,000 to 2,000,000 as measured by gel permeation chromatography; and (c) a powder material comprising an α-diketone compound (see Patent Document 1). The final curing of such denture base lining materials is usually achieved by applying active light having a wavelength range of about 360 to 500 nm (the main absorption range of α-diketone compounds) at a light intensity of 50 to 6,000 mW / cm in that wavelength range. 2 This is done using a dedicated light irradiator with a light source that can irradiate with an output of approximately [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6779506 Summary of the Invention [Problem to be solved by the invention]

[0007] In powder-liquid types using a photopolymerization initiator comprising a combination of an α-diketone compound and a tertiary amine compound as described above, the allocation of catalyst components to the powder and liquid materials can basically be arbitrary. However, as in the denture base relining material described in Patent Document 1, the α-diketone compound is often blended into the powder material and the tertiary amine compound into the liquid material, and then packaged separately.

[0008] However, according to the inventors' investigations, it has become clear that in the denture base lining material described in Patent Document 1, the powder material containing resin particles and an α-diketone compound may aggregate when stored at room temperature for a long period of time or when stored in a state where the temperature is suddenly elevated.

[0009] If the powder material aggregates, it becomes difficult for the aggregated components to dissolve when the powder material and liquid material are mixed to prepare a paste for use as a denture base relining material, which causes problems such as the speed at which the viscosity of the paste increases deviating from the designed value, resulting in poor usability, and the aggregated components remaining undissolved as they harden, making the material brittle.

[0010] Therefore, an object of the present invention is to provide a technique for preventing aggregation of a powder material containing resin particles and an α-diketone compound during storage. [Means for solving the problem]

[0011] The present invention is intended to solve the above-mentioned problems, and a first aspect of the present invention is a method for producing a powder composition, comprising: a raw material powder preparation step of preparing a raw material powder containing 100 parts by mass of an amorphous resin powder and 0.05 to 1.0 parts by mass of an α-diketone compound powder; an agglomeration step of treating the raw material powder at a heat treatment temperature of 40°C or higher and lower than the glass transition point of the amorphous resin to obtain coarse agglomerated particles formed by agglomeration of the amorphous resin that constitutes the amorphous resin powder, the coarse agglomerated particles having an α-diketone compound present on the surface thereof; and a crushing step of crushing the coarse agglomerated particles, wherein a powder composition containing agglomerated particles that are a crushed product of the coarse agglomerated particles is obtained.

[0012] In the manufacturing method of the above form (hereinafter also referred to as "the composition manufacturing method of the present invention"), the raw material powder preferably contains an amorphous resin powder having an average particle size (50% volume average particle size) measured by laser diffraction method of 1 to 300 μm, and an α-diketone compound powder having an average particle size (50% number average particle size) measured by laser diffraction method in the range of 50 to 300 μm.

[0013] The raw material powder preferably contains 0.03 to 0.3 parts by mass of inorganic fine particles having an average particle size (50% volume average particle size) measured by laser diffraction method of 0.01 to 0.2 μm per 100 parts by mass of resin powder.

[0014] Furthermore, in the agglomeration step, it is preferable to obtain coarse agglomerated particles by leaving the raw material powder to stand at atmospheric pressure and the heat treatment temperature.

[0015] A second aspect of the present invention is a liquid material containing a polymerizable monomer and a tertiary amine compound, Coarse agglomerated particles formed by agglomeration of amorphous resin constituting amorphous resin powder, with an α-diketone compound present on the surface thereof. and a powder material comprising a powder composition containing the powder composition, wherein the powder composition constituting the powder material is produced by the composition production method of the present invention. Includes processes The method for producing the denture base lining material (hereinafter also referred to as "the method for producing the lining material of the present invention") is characterized in that: [Effects of the Invention]

[0016] According to the composition manufacturing method of the present invention, it is possible to efficiently manufacture a powder composition that is unlikely to aggregate even when stored for a long period of time and that can be suitably used as a powder material for denture base relining materials. Furthermore, a (light-curing type) denture base relining material manufactured by the relining material manufacturing method of the present invention, which uses the powder composition manufactured by the manufacturing method as the powder material, is unlikely to aggregate due to long-term storage at room temperature or unexpected temperature rise, and therefore has excellent storage stability and can maintain for a long period of time the same usability and curing characteristics as when it was first manufactured. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to solve the above-mentioned problems, the present inventors first investigated the aggregation characteristics of a powder material containing resin particles and an α-diketone compound. As a result, they found that the α-diketone compound in the powder material has sublimation properties, and after sublimation, the α-diketone compound solidifies on the surface of the resin particles in the powder material system, thereby adhering adjacent resin particles to each other and agglomerating the powder material. Based on this finding, they further investigated methods for controlling the sublimation-sublimation characteristics of the α-diketone compound, and found that if the powder material is actively aggregated to form coarse aggregated particles and then pulverized, the pulverized material is less likely to re-agglomerate, which led to the completion of the present invention.

[0018] The reason for such excellent effects is not entirely clear, but the inventors speculate as follows. Immediately after mixing the resin particles and the α-diketone compound, the resin particles and the α-diketone compound are dispersed and not aggregated. However, in the coarse aggregated particles formed by heat treatment, the sublimated α-diketone compound diffuses into the surroundings and then sublimes on the surface of the resin particles, resulting in a widely and uniformly dispersed state. It is also believed that the slight entanglement of polymer chains on the surface of the resin particles (not covered with the α-diketone compound) that occurred during the heat treatment is fixed. Furthermore, when the coarse aggregated particles are pulverized, the surfaces of most of the resulting pulverized particles (aggregated particles) are (at least partially) covered with the α-diketone compound, which inhibits contact between the surface polymers of the resin particles and makes aggregation less likely.

[0019] As described above, the composition manufacturing method and the lining material manufacturing method of the present invention have a major feature in that a raw material powder containing a resin powder and an α-diketone compound powder, such as those used as powder materials for conventional powder-liquid lining materials using photopolymerization initiators, is first aggregated and then disintegrated. The raw materials constituting the raw material powder are not particularly different from those used in the above-mentioned conventional powder materials. Furthermore, the liquid material in the lining material obtained by the lining material manufacturing method of the present invention is not particularly different from conventional liquid materials (containing a polymerizable monomer and a tertiary amine compound). The present invention, including these points, will be described in detail below.

[0020] In this specification, unless otherwise specified, the expression "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 an expression, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x. Furthermore, in this specification, the term "(meth)acrylic" means both "acrylic" and "methacrylic." Similarly, the term "(meth)acrylate" means both "acrylate" and "methacrylate," and the term "(meth)acryloyl" means both "acryloyl" and "methacryloyl."

[0021] 1. Method for producing the composition of the present invention The method for producing a composition of the present invention comprises the following steps: (1) a raw material powder preparation step, (2) an agglomeration step, and (3) a pulverization step, and is characterized by obtaining a powder composition containing agglomerated particles (which are pulverized products of coarse agglomerated particles) obtained in the pulverization step. Each of these steps will be described below.

[0022] (1) Raw material powder preparation process In the raw material powder preparation step, a raw material powder containing 100 parts by mass of amorphous resin powder and 0.05 to 1.0 parts by mass of α-diketone compound powder is prepared. As long as the raw material powder satisfies the above conditions, the powder of a powder-liquid type lining material using a photopolymerization initiator may be used as is, or it may be prepared separately. When prepared separately, it is sufficient to mix predetermined amounts of each component. Mixing can be suitably performed using, for example, a rocking mixer in which the container itself rotates, or a blade agitator using rotating blades. Since the amount of α-diketone compound contained in the raw material powder is small compared to the amount of amorphous resin powder, taking into account ease of handling of the powder, the raw material powder may be mixed with a portion of the amorphous resin powder in advance to form a master batch. The various raw materials that make up the raw material powder and the amounts of each raw material mixed will be described below.

[0023] (1-1) Amorphous resin powder Examples of amorphous resin powders suitable for use as raw material powders include amorphous resin particles made of polymethyl methacrylate, polyethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate, methyl methacrylate-ethyl methacrylate copolymer, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-styrene-butadiene copolymer, etc. These amorphous resin particles may be used alone or in combination. When the powder composition that is the target of the composition production method of the present invention is for dental use, particularly for denture base lining materials, it is preferable to use polyethyl methacrylate because of its good solubility in liquid materials and its good viscosity-increasing properties in a paste state.

[0024] These amorphous resins may be either crosslinked or non-crosslinked, but non-crosslinked resin particles are generally used for denture base relining materials. In this case, the weight-average molecular weight of the amorphous resin measured by gel permeation chromatography (GPC) is preferably 30,000 to 2,000,000 in terms of the solubility of the resin particles in the liquid material and the appropriate timing for increasing the viscosity of the paste, and is preferably in the range of 30,000 to 1,000,000 because it facilitates the pulverization (disintegration) of the aggregates obtained in the agglomeration step.

[0025] The shape of the resin particles constituting the amorphous resin powder is not particularly limited and may be either spherical or irregular. The particle size is also not particularly limited, and a plurality of resin particles having different average particle sizes may be used in combination.

[0026] However, when the powder composition, which is the target of the composition manufacturing method of the present invention, is for dental use, particularly for denture base lining materials, it is preferable to use amorphous resin particles having an average particle size (50% volume average particle size) measured by laser diffraction method of 1 to 300 μm. Furthermore, because the aggregates obtained in the agglomeration step can be easily pulverized (disintegrated), the average particle size is more preferably 5 to 300 μm. Furthermore, it is preferable that the resin (primary) particles are spherical particles with a sphericity of 0.6 or more. The BET specific surface area of ​​the amorphous resin powder measured by nitrogen adsorption method is usually 0.5 to 10 m 2 / g range.

[0027] (1-2) α-diketone compounds α-diketone compounds have a maximum absorption wavelength of 350 to 700 nm and are capable of generating active species, such as radicals, that are effective in polymerization when exposed to actinic light. Active species are usually generated as a result of energy or electron transfer between polymerizable monomers or other substances.

[0028] Examples of α-diketone compounds suitable for use in the present invention include camphorquinone, benzil, camphorquinonesulfonic acid, acenaphthenequinone, 1,2-naphthoquinone, 1,2-phenanthrenequinone, and 9,10-phenanthrenequinone. Among these, camphorquinone is particularly suitable for dental applications, particularly for denture lining materials, due to its high polymerization activity and safety to living organisms. From the viewpoint of quickly carrying out the aggregation process, it is preferable to use compounds having an average particle size (50% number-average particle size) of 50 to 300 μm or less, and particularly 50 to 200 μm or less. The average particle size referred to here refers to a value measured by laser diffraction.

[0029] The particle size of the α-diketone compound can be controlled by adjusting the conditions for grinding, such as dry grinding or wet grinding, and the average particle size can be controlled in advance by using a sieve with the desired mesh size.

[0030] If the amount of α-diketone compound in the raw material powder is too high, the hardened product tends to become soft when used as a powder material for denture base relining material, and if the amount is too low, the effects of the present invention are difficult to achieve. Therefore, the amount of α-diketone compound needs to be 0.05 to 1.0 parts by mass per 100 parts by mass of the amorphous resin powder.

[0031] (1-3) Inorganic fine particles It is preferable to blend inorganic fine particles into the raw powder for the reasons of facilitating disintegration (pulverization) in the pulverization process and enhancing the (re)agglomeration prevention effect. It is presumed that disintegration is facilitated because the powder material agglomerates with the inorganic fine particles interposed between the resin particles, and the inorganic fine particles become the starting point for disintegration during disintegration. It is also presumed that reagglomeration is suppressed because the inorganic fine particles are interposed between the resin particles coated with the α-diketone compound in the disintegrated powder material, making it difficult for the resin particles to come into contact with each other.

[0032] When inorganic fine particles are blended, the inorganic particles are preferably sufficiently smaller than the resin particles constituting the amorphous resin powder, and preferably have an average particle size (50% volume average particle size) measured by laser diffraction of 0.01 to 0.2 μm. From the viewpoint of effectiveness, the blending amount is preferably 0.03 to 0.3 parts by mass per 100 parts by mass of the amorphous resin powder.

[0033] Suitable inorganic fine particles include quartz, silica, alumina, silica titania, silica zirconia, lanthanum glass, barium glass, and strontium glass. Cation-eluting inorganic particles made of hydroxides such as calcium hydroxide and strontium hydroxide, or oxides such as zinc oxide, silicate glass, and fluoroaluminosilicate glass, can also be used. Among these, silica fine particles are preferred because they are readily available in the desired particle size.

[0034] The inorganic fine particles described above are preferably treated with a surface treatment agent, such as a silane coupling agent, in order to improve compatibility with polymerizable monomers and improve mechanical strength and water resistance.The surface treatment method can be carried out by a known method, and as the silane coupling agent, methyltrimethoxysilane, methyltriethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloyloxypropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, hexamethyldisilazane, etc. are preferably used.

[0035] (1-4) Other ingredients Depending on the purpose, organic pigments, inorganic pigments, ultraviolet absorbers, etc. may be added to the raw material powder within a range that does not impair the performance of the raw material powder. In addition, organic peroxides such as benzoyl peroxide may be added as other initiator components.

[0036] (2) Agglomeration process In the agglomeration step, the raw material powder is heat-treated at a temperature above 40°C and below the glass transition temperature (Tg) of the amorphous resin to obtain coarse agglomerated particles formed by the agglomeration of the amorphous resin constituting the amorphous resin powder, with the α-diketone compound present on the surface. Heat-treatment temperatures below 40°C require a long time for agglomeration, while those above the glass transition temperature likely result in agglomeration of only the amorphous resin particles themselves, or the sublimated α-diketone compound dissipates, making it difficult to achieve the desired effect. From the standpoint of effectiveness, heat treatment is preferably performed at a temperature above 40°C and in the range of 20°C below Tg to 5°C below Tg. Note that in the agglomeration step, the α-diketone compound is present on the surface of the resulting coarse agglomerated particles due to the sublimation and coagulation of the α-diketone compound caused by the heat treatment.

[0037] The glass transition point (Tg) of amorphous resins is well known in literature and books for general-purpose homopolymers, and if it is unknown, it can be easily measured using a differential scanning calorimeter.

[0038] To prevent the α-diketone compound from sublimating and dissipating outside the system, the heat treatment can be performed by placing the raw material powder in a sealed container and storing it in a thermostatically controlled incubator. Examples of container materials include resin containers such as polystyrene, polyethylene, polypropylene, ABS resin, polyvinyl chloride, and PET resin, as well as glass, enamel, stainless steel, and porcelain. Resin containers are preferred for their moldability and airtightness. To protect the container from ambient light, it is preferable to incorporate a black pigment into the container to enhance its light-blocking properties. Examples of black pigments include carbon black, perylene black, aniline black, and iron oxide. A rocking mixer equipped with a heating device can also be used as the container. In this case, the grinding process can be carried out directly after the agglomeration process.

[0039] The heat treatment is preferably carried out by leaving the raw material powder at rest under atmospheric pressure at the heat treatment temperature.

[0040] The heat treatment may be terminated when the formation of coarse particles with particle diameters of 2 mm or more, preferably 3 mm or more, in the raw material powder can be confirmed by the heat treatment. The formation of coarse particles and the presence or absence of powder can be confirmed visually. Usually, when coarse particles of this size are formed by the heat treatment, the α-diketone compound adheres to the surface of the coarse particles through sublimation and coagulation of the α-diketone compound. Such sublimation and coagulation causes the α-diketone compound powder (particles) present during the preparation of the raw material powder to disappear, and their presence can no longer be confirmed visually. From the perspective of performing the heat treatment step more reliably, it is preferable to sample a small amount and confirm the disappearance of the α-diketone compound powder (particles) through observation under an optical microscope. The α-diketone compound can be easily confirmed visually or with an optical microscope (because α-diketone compounds have a color tone such as yellow-green to yellow to brown, which is associated with their excitation by visible light wavelengths).

[0041] The heat treatment time in the agglomeration step varies depending on the heat treatment temperature and the amount of the α-diketone compound, but is usually about 8 hours to 10 days.

[0042] (3) Crushing process In the pulverization step, the coarse agglomerated particles obtained in the above step are pulverized. The pulverization is usually carried out after the raw material powder after the heat treatment has been cooled to about room temperature. There are no particular limitations on the method for pulverizing the coarse agglomerated particles, and for example, a device such as a roll mill, a ball mill, a blade agitator, a hammer mill, or a jet mill may be used. After the treatment, the container containing the coarse agglomerated particles may be shaken to cause the agglomerated powder to collide with the wall and be pulverized, or the particles may be transferred to a bag and kneaded.

[0043] However, when a strong shear force is applied for a long period of time, such as when using high-speed blade stirring, the (primary) particles that make up the amorphous resin powder may deform, which may change the paste fluidity and the timing of viscosity increase when used, for example, as a powder-liquid type denture base relining material, so care must be taken. For this reason, when mechanically pulverizing using a pulverizer, it is preferable to check the conditions, pulverization efficiency, particle deformation, etc. in advance.

[0044] During pulverization (disintegration), it is not possible to disintegrate all coarse agglomerated particles into primary particles, and the powder composition obtained after pulverization contains agglomerated particles. The degree of pulverization (disintegration) can be determined appropriately depending on the application. However, in the case of a powder material for a denture base relining material, it is preferable to pulverize the agglomerated particles so that the maximum diameter of the resulting particles is 0.3 mm or less, in order to avoid impairing the viscosity-increasing performance of the paste in that application. The maximum diameter of the agglomerated particles can be confirmed by placing 0.1 g of the agglomerated particles obtained after pulverization on a transparent resin film, gently spreading them out to a 5 cm square without disintegrating the agglomerates, and observing them with a micrometer-equipped optical microscope at 100x magnification. Note that classification using a sieve may result in a different composition from the raw powder. Therefore, if coarse particles are present, it is preferable to omit classification and instead pulverize (disintegrate) the entire amount until the desired particle diameter is reached by increasing the output power of the device or extending the processing time.

[0045] In addition, the pulverization process also has the function of adhering to the surface of the crushed particles the α-diketone compound that did not adhere to the surface of the coarse agglomerated particles due to sublimation-coagulation in the agglomeration process but remained inside the particles, thereby also achieving the effect of preventing reagglomeration.

[0046] 2. Method for manufacturing lining material of the present invention The powder composition obtained by the composition production method of the present invention can be used for various purposes such as self-polymerizing resins and dental adhesives, but is particularly suitable for use as a powder material for photopolymerizing denture base lining materials. That is, the powder composition is a mixture of a liquid material containing a polymerizable monomer and a tertiary amine compound and a powder material containing resin particles and an α-diketone compound. powder Material and consists of It can be particularly suitably used as a powder material for a light-curing type denture base lining material. A method for producing a photopolymerization type denture base relining material, comprising producing the powder composition constituting the powder material by the composition production method of the present invention. Includes processes According to the relining material manufacturing method of the present invention, aggregation of powder material during storage is prevented, and it is possible to manufacture a denture base relining material that has appropriate paste fluidity and stable timing of viscosity increase during use for a long period of time.

[0047] The method for producing the liquid material in the lining material manufacturing method of the present invention is not particularly different from the method for producing the liquid material in conventional powder-liquid lining materials using photopolymerization initiators, and the polymerizable monomer, tertiary amine compound, and other components to be blended as necessary are each measured out in the required amounts and mixed together.

[0048] Examples of the polymerizable monomer include monofunctional (meth)acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, hydroxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-(meth)acryloyloxyethyl propionate, and acetoacetoxyethyl (meth)acrylate; bifunctional (meth)acrylic monomers such as 1,6-bis((meth)acryloylethyloxycarbonylamino)trimethylhexane, 2,2-bis((meth)acryloyloxyphenyl)propane, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate; and trifunctional (meth)acrylic monomers such as trimethylolmethane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate. These (meth)acrylic monomers may be used alone or in combination of two or more. In particular, the combined use of a monofunctional (meth)acrylic monomer and a difunctional or higher functional (meth)acrylic monomer is preferred because it can improve the mechanical properties such as strength and durability of the resulting cured product.

[0049] Examples of the tertiary amine compound include methyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, N,N-dimethylaniline, N,N-dibenzylaniline, N,N-dimethyl-p-toluidine, N,N-diethyl-p-toluidine, triethanolamine, N-methyldiethanolamine, 2-(dimethylamino)ethyl methacrylate, etc. The amount of the tertiary amine compound to be added is preferably 0.1 to 2 parts by mass per 100 parts by mass of the polymerizable monomer.

[0050] Examples of other components include non-polymerizable acidic compounds such as malic acid, tartaric acid, and citric acid, and fragrances such as essences, flavors, and refined oils. The amount of other components to be added is preferably 0.005 to 0.05 parts by mass relative to 100 parts by mass of the polymerizable monomer. [Example]

[0051] EXAMPLES In the following, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0052] First, the names, characteristics, abbreviations (when abbreviations are used) and evaluation methods of the substances used to prepare the raw material powders (powder materials) in each of the examples and comparative examples will be explained.

[0053] (1) Amorphous resin powder PEMA35: Spherical polyethyl methacrylate particles (average particle size 35 μm, weight-average molecular weight 500,000, Tg=65°C) PEMA2: Spherical polyethyl methacrylate particles (average particle size 2 μm, weight-average molecular weight 500,000, Tg=65°C) PEMA5: Spherical polyethyl methacrylate particles (average particle size 5 μm, weight-average molecular weight 500,000, Tg=65°C) PEMA100: Spherical polyethyl methacrylate particles (average particle size 100 μm, weight-average molecular weight 500,000, Tg=65°C) PEMA200: Spherical polyethyl methacrylate particles (average particle size 200 μm, weight-average molecular weight 500,000, Tg=65°C) PEMA35A: Spherical polyethyl methacrylate particles (average particle size 35 μm, weight-average molecular weight 50,000, Tg=65°C) PEMA35B: Spherical polyethyl methacrylate particles (average particle size 35 μm, weight-average molecular weight 200,000, Tg=65°C) PEMA35C: Spherical polyethyl methacrylate particles (average particle size 35 μm, weight-average molecular weight 1 million, Tg=65°C) PEMA35D: Spherical polyethyl methacrylate particles (average particle size 35 μm, weight average molecular weight 2 million, Tg=65℃).

[0054] (2) α-diketone compounds CQ: Camphorquinone (melting point 203°C) ·B: Benzyl (melting point 96℃).

[0055] (3) Inorganic fine particles · Silica microparticles: Reolosil (average particle size 120nm).

[0056] Example 1 A raw material powder was prepared by introducing 100 parts by mass of PEMA35 as an amorphous resin powder and 0.3 parts by mass of CQ (average particle size: 100 to 200 μm) as an α-diketone compound into a 100 ml polypropylene resin bottle that could be sealed with a screw-on lid, closing the lid, and mixing with a rocking mixer (raw material powder preparation process).

[0057] Next, the container was removed from the rocking mixer, and with the lid closed, it was stored in an incubator (Yamato Scientific Co., Ltd.) at 55°C. Thereafter, the lid of the container was removed every day without vibrating the container, and the powder material inside was checked for agglomerations. If no agglomerations were found, or if they were found but the agglomerates were 2 mm or less in size, it was determined that no agglomeration had occurred, and the container was sealed and continued to be stored at 55°C. The number of days (4 days in this example) when agglomerates of 2 mm or more were first found in the raw material powder was defined as the heat treatment period (hours), and the heat treatment was terminated. Note that, as is clear from this determination method, the heat treatment period (days) corresponds to the agglomeration period (hours) of the raw material powder when stored at 55°C.

[0058] After the heat treatment, the raw powder was visually inspected again to confirm the formation of many coarse particles with a particle size of 2 mm or more. Furthermore, when several coarse particles were sampled and observed under an optical microscope, it was found that the CQ particles had disappeared, and it was assumed that all the CQ particles had adhered to the aggregate surface through sublimation and coagulation (aggregation process).

[0059] The agglomerated powder was then shaken and mixed in the container to break down coarse particles. To determine whether the powder was broken down, 0.1 g of the powder was taken out of the container and placed on a transparent resin film, gently spread out in a 5 cm square area, and observed under a microscope with a micrometer, repeatedly repeating the process until the agglomerated particles were 0.3 mm or less (crushing process).

[0060] A portion of the obtained powder composition (powder material) was used to evaluate the reagglomeration property as follows. That is, to evaluate the reagglomeration property, the powder composition was sealed in a container and heated again in an incubator at 55°C, and checked every day, in the same manner as in the determination of the heat treatment period described above. The number of days until agglomerates of 2 mm or more appeared in the powder material was defined as the reagglomeration period. As a result, the number of days required for reagglomeration was 22 days, which was 18 days longer than when the raw material powder was stored as is.

[0061] To confirm the effect of photopolymerization on the paste properties and hardening properties of the paste (obtained by mixing the powder and liquid materials) when used as a photopolymerizable powder-liquid denture base relining material, we measured the consistency and hardening depth of paste 1, which used the powder and liquid materials obtained by the above-mentioned agglomeration and grinding processes, and paste 2, which used raw powder (prepared within three days) without these processes. The liquid material used was prepared by adding 0.5 parts by weight of ethyl p-dimethylaminobenzoate (a tertiary amine compound) and 0.01 parts by weight of malic acid (an additional component) to a polymerizable monomer mixture of 50 parts by weight of 2-methacryloxyethyl propionate and 50 parts by weight of 1,9-nonamethylenediol dimethacrylate, and stirring the mixture. The method for measuring consistency and hardening depth and the results are shown below.

[0062] <Consistency> Measurement method: 1.8 g (180 parts by mass) of powder material and 1.0 g (100 parts by mass) of liquid material were placed in a rubber cup and mixed for 20 seconds, after which the paste (a photocurable composition composed of a mixture of powder and liquid materials) was filled into a graduated syringe. One minute and 30 seconds after mixing began, 0.5 mL of paste was dispensed onto a polypropylene film, and then, two minutes after mixing began, another polypropylene film was inserted and a 7.355 N weight was applied for five minutes. The diameter of the spread paste was then measured at four points, and the average value was taken as the consistency. Results: The consistency 1 of Paste 1 was 45 mm, and the consistency 2 of Paste 2 was 47 mm, with no significant difference between the two.

[0063] <Photocuring depth> Measurement method: 1.8 g (180 parts by mass) of powder material and 1.0 g (100 parts by mass) of liquid material were placed in a rubber cup and mixed for 20 seconds. The kneaded paste (a photocurable composition formed by mixing the powder material and the liquid material) was filled into a cylindrical black rubber tube with an inner diameter of 4 mm, an outer diameter of 6 mm, and a height of 10 mm, and both sides were pressure-welded with polypropylene film. Then, actinic light with a wavelength of 465 to 475 nm (light output density 100 mW / cm) was irradiated from one end of the cylindrical black rubber tube filled with the paste using a dental laboratory photopolymerization device, Alpha Light V (manufactured by MORITA). 2 The sample was removed from the black rubber tube, the uncured portion was removed, and the length of the cured portion was measured with a vernier caliper to obtain the photocuring depth. Results: The photocuring depth 1 of Paste 1 was 4.4 mm, and the photocuring depth 2 of Paste 2 was 4.4 mm, with no significant difference between the two.

[0064] Comparative Example 1 The raw material powder was prepared and agglomerated in the same manner as in Example 1, and the powder obtained by the agglomeration process was used as the powder material without performing the pulverization process. Except for this, the paste properties and the hardened body properties were evaluated in the same manner as in Example 1. The results were a consistency of 66 mm and a photocuring depth of 3.8 mm, which were significantly different from the values ​​of Paste 2 (the consistency was longer and the photocuring depth was shallower).

[0065] Comparative Example 2 The raw material powder was prepared in the same manner as in Example 1, and the agglomeration process was carried out in the same manner as in Example 1 except that the temperature of the thermostatic bath was set to 25°C. It took 70 days for agglomerates of 2 mm or larger to form.

[0066] Comparative Example 3 The raw material powder was prepared in the same manner as in Example 1 and left in a thermostatic chamber at 70°C for one day. As a result, the raw material powder strongly agglomerated in the container, and the grinding process could not be carried out in the same manner.

[0067] Examples 2 to 9 The evaluation was carried out in the same manner as in Example 1, except that the α-diketone compound used was changed as shown in Table 1, and further the heat treatment temperature and time in the agglomeration step were changed as shown in Table 1.

[0068] The time required for reagglomeration is also shown in Table 1. Note that the heat treatment period (hours) in Table 1 refers to the day on which agglomerates of 2 mm or more were first observed as a result of daily observation, as in Example 1, and the heat treatment was terminated on that day. If the number of days required for reagglomeration were longer than that, it would mean that reagglomeration was suppressed. Furthermore, as in Example 1, no significant differences were observed in the consistency and hardening depth.

[0069] [Table 1]

[0070] In Example 2, the heat treatment temperature was lowered to 45°C, and although the treatment period was prolonged, it was still within the acceptable range. Examples 3 to 5 were examples in which the average particle size of the CQ used was changed, and the larger the average particle size, the longer the minimum required heat treatment period. Examples 6 to 8 were examples in which the blending amount of CQ was changed, and the greater the blending amount, the shorter the minimum required heat treatment period. Example 9 was an example in which B was used instead of CQ, and the same effect was confirmed.

[0071] Examples 10 to 17 The evaluation was carried out in the same manner as in Example 1, except that the amorphous resin powder used was changed as shown in Table 2, and further the heat treatment temperature and time in the agglomeration step were changed as shown in Table 2.

[0072] The time required for re-aggregation is also shown in Table 2. As with Example 1, no significant differences were observed in the consistency and hardening depth.

[0073] [Table 2]

[0074] Among the examples shown in Table 2, Examples 1 and 10 to 13 varied the average particle size of the PEMA powder, which is an amorphous resin powder. These results show that the average particle size of the amorphous resin powder does not have a significant effect on the effect, but in Example 11, which used PEMA with an average particle size of 2 μm, agglomerations were more difficult to break down and disintegration was more difficult than in Example 1, which used PEMA with an average particle size of 35 μm, and the number of days until reagglomeration was shorter than in Example 1. This is thought to be because the smaller average particle size of the resin particles increases the number of contact points between particles, resulting in stronger agglomerations.

[0075] Furthermore, in Examples 1, 14 to 17, the weight-average molecular weight of PEMA was changed while maintaining the same average particle size, and these results show that the weight-average molecular weight does not have a significant effect on the effect. In Example 17, which used a weight-average molecular weight of 2 million, it was more difficult to break down the agglomerates than in Example 1. This is thought to be because the large molecular weight of the polymer constituting the resin particles resulted in increased entanglement of the polymer molecular chains between the resin particles.

[0076] Examples 18 to 20 Raw material powders were prepared in the same manner as in Example 1, except that silica fine particles were further mixed with 100 parts by mass of PEMA35 and 0.3 parts by mass of CQ (average particle diameter: 100 to 200 μm). The amounts of silica fine particles were 0.15 parts by mass in Example 18, 0.03 parts by mass in Example 19, and 0.3 parts by mass in Example 20. Using each of the obtained raw material powders, powder materials were prepared and evaluated in the same manner as in Example 1. As a result, in Examples 18 and 20, no reagglomeration occurred even after 50 days or more, and in Example 19, it took 29 days for reagglomeration to occur. The results are shown in Table 3. No significant differences were observed in the paste state and hardened body properties between the examples. Furthermore, in all examples, the agglomerations were more easily broken down in the grinding process than in the grinding process of Example 1.

[0077] [Table 3]

Claims

1. a raw material powder preparation step of preparing a raw material powder containing 100 parts by mass of an amorphous resin powder and 0.05 to 1.0 parts by mass of an α-diketone compound powder; an agglomeration step of treating the raw material powder at a heat treatment temperature of 40°C or higher and lower than the glass transition point of the amorphous resin to obtain coarse agglomerated particles formed by agglomeration of the amorphous resin constituting the amorphous resin powder, the coarse agglomerated particles having an α-diketone compound on the surface thereof; and a pulverization step of pulverizing the coarse agglomerated particles; Including, obtaining a powder composition containing agglomerated particles that are pulverized products of the coarse agglomerated particles; A method for producing a powder composition comprising:

2. 2. The method for producing a powder composition according to claim 1, wherein the raw material powder comprises an amorphous resin powder having an average particle size (50% volume average particle size) measured by a laser diffraction method of 1 to 300 μm, and an α-diketone compound powder having an average particle size (50% number average particle size) measured by a laser diffraction method in the range of 50 to 300 μm.

3. 3. The method for producing a powder composition according to claim 1, wherein the raw material powder contains 0.03 to 0.3 parts by mass of inorganic fine particles having an average particle diameter (50% volume average particle diameter) measured by a laser diffraction method of 0.01 to 0.2 μm per 100 parts by mass of the amorphous resin powder.

4. 4. The method for producing a powder composition according to claim 1, wherein in the agglomeration step, coarse agglomerated particles are obtained by leaving the raw material powder to stand at atmospheric pressure and at the heat treatment temperature.

5. 5. The method for producing a powder composition according to claim 1, wherein in the pulverization step, the coarse agglomerated particles are pulverized so that the agglomerated particles have a maximum particle diameter of 0.3 mm or less as measured with an optical microscope.

6. A method for producing a photopolymerization type denture base lining material comprising a liquid material containing a polymerizable monomer and a tertiary amine compound, and a powder material made of a powder composition containing coarse agglomerated particles formed by agglomeration of amorphous resin constituting an amorphous resin powder, the coarse agglomerated particles being pulverized and having an α-diketone compound on the surface thereof, comprising: A method for producing the denture base relining material, comprising the step of producing the powder composition constituting the powder material by the method of claim 1.

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