JP6683339B1 - Gypsum molding excellent in chipping resistance and compressive strength and method for producing the same - Google Patents
Gypsum molding excellent in chipping resistance and compressive strength and method for producing the same Download PDFInfo
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Abstract
耐チッピング改良として、接着剤を使用せずとも作業者の安全衛生管理が可能であり、圧縮強度が低下しないかもしくは、向上する水溶性樹脂を配合した石膏成形体及びその製造方法を提供する。焼石膏100重量部に対し、ポリビニルピロリドン水溶液、ポリビニルアルコール水溶液、エチレン酢酸ビニル共重合体エマルジョンから選択された、1つ又は2つ以上の組み合せからなる樹脂0.5〜20重量部を配合した石膏組成物に対して、加水硬化する処理工程において、60℃〜230℃の乾燥処理を実施した石膏成形体であって、圧縮強度と耐チッピングに優れた石膏成形体である。Provided is a gypsum molded product containing a water-soluble resin that can be controlled in safety and hygiene of an operator without using an adhesive as an improvement in chipping resistance, and whose compressive strength does not decrease or is improved, and a method for producing the same. Gypsum containing 0.5 to 20 parts by weight of a resin selected from an aqueous polyvinylpyrrolidone solution, an aqueous polyvinyl alcohol solution, and an ethylene vinyl acetate copolymer emulsion based on 100 parts by weight of calcined gypsum. The composition is a gypsum molded body that is subjected to a drying treatment at 60 ° C to 230 ° C in the treatment step of hydrolyzing, and is a gypsum molded body excellent in compressive strength and chipping resistance.
Description
本発明は、水と練和し硬化後に得られる成形体の圧縮強度を改良し、かつ切削加工時の耐チッピングに優れ、特に歯科用石膏模型の製作に有用な焼石膏を主成分とした石膏組成物及び石膏成形体並びに石膏成形体の製造方法に関する。 The present invention improves the compressive strength of a molded body obtained by kneading with water and curing, and is excellent in chipping resistance during cutting, and especially plaster mainly composed of calcined gypsum which is useful for producing a dental plaster model. The present invention relates to a composition, a gypsum molded body, and a method for producing a gypsum molded body.
焼石膏に水を混合し混練することにより針状・板状の結晶が成長し結晶同志が密に凝集することから硬い石膏成形体が得られる。石膏業界ではこの工程を硬化という。石膏成形体は美術、工作物から、タイヤ製造時の型に利用されるなど工業用途に利用され、またギブスや歯科の型取りとしても広く利用されている。 By mixing and kneading water with calcined gypsum, needle-shaped and plate-shaped crystals grow, and the crystals are densely aggregated, so that a hard gypsum compact can be obtained. This process is called curing in the gypsum industry. Gypsum moldings are used for industrial purposes such as arts, works, and molds for tire manufacturing, and are also widely used as casts for dental casts and dentistry.
特に歯科分野においては、アルジネートやシリコーンなどの印象材を用いて撮像した患者口腔内の歯型印象に歯科用石膏のスラリー(泥漿)を注入し、硬化後、離型及び乾燥することにより得られた歯型模型を切削加工した後、種々の工程を経て最終的に義歯や冠が作製されている。 Particularly in the field of dentistry, it is obtained by injecting a dental plaster slurry (slurry) into a dental impression of a patient's mouth imaged using an impression material such as alginate or silicone, curing, releasing and drying. After cutting the tooth model, the dentures and crowns are finally manufactured through various processes.
このような従来技術においては以下のような課題がある。
歯科技工における石膏模型の切削作業(カービング)においてはチッピング及び支台歯辺縁など鋭利な形状部分が欠けることがある。この場合は最初からやり直しをするか補修を施すことで作業効率が著しく損なわれる。硬度対策として石膏の種類(α、β)の選択と加水量の調整がなされる。針状・板状の結晶成長の結果、成形体は膨張する。膨張を抑えるためには加水量を多くすることがあるが、逆に硬度の低下となってトレードオフの関係となる。そこで膨張しない無機フィラーを混合するケースもあるが、加水混合中の分離なども随伴することから制御が困難である。The conventional technique has the following problems.
In the cutting work (carving) of a gypsum model in a dental technician, a sharp shape part such as chipping and an abutment tooth edge may be missing. In this case, work efficiency is significantly impaired by reworking or repairing from the beginning. As a measure against hardness, the type of gypsum (α, β) is selected and the amount of water added is adjusted. As a result of needle-like and plate-like crystal growth, the compact expands. The amount of water added may be increased in order to suppress expansion, but on the contrary, the hardness decreases, which results in a trade-off relationship. Therefore, there is a case where an inorganic filler that does not expand is mixed, but it is difficult to control because it is accompanied by separation during mixing with water.
歯科技工現場では切削時の欠けは製品の作り直しを要することから切実な問題である。そこで石膏成形体に接着剤を塗布することで対応していることもある。特許文献3に例示されている接着剤にジェル状の2−シアノアクリレート系瞬間接着剤がある。2−シアノアクリレートの速硬化性を利用したものであるが、溶媒は疎水性あるので、石膏成形体が乾燥している場合は塗布が可能であるが、石膏成形体が乾燥不十分であれば弾かれて塗布することができない。石膏成形体は厚みが厚いほど内部までの乾燥に時間を要するため、表面が乾く時間乾燥しても内部の乾燥が不十分であるから接着剤は内部まで浸透しない。 In the dental laboratory, chipping during cutting is a serious problem because it requires remaking the product. Therefore, it may be possible to deal with this by applying an adhesive to the gypsum molded body. An adhesive exemplified in Patent Document 3 is a gel-like 2-cyanoacrylate instant adhesive. Although the rapid curing property of 2-cyanoacrylate is used, since the solvent is hydrophobic, it can be applied when the gypsum molded product is dry, but if the gypsum molded product is insufficiently dried. It is repelled and cannot be applied. Since the thicker the gypsum molded body, the longer it takes to dry the interior, the adhesive does not penetrate into the interior because the interior is not sufficiently dried even if the surface is dried for the time.
従って、通常は接着剤塗布効果の発現は乾燥した表面に限られる。よって切削作業は石膏成形体表面から乾燥、接着剤塗布を繰り返しながら内部へ進めるか、十分に乾燥した後に接着剤を塗布して行うかに限定される。さらに接着剤が有機溶媒を含有していることは、成形体に顔を近接して作業する作業形態になることから安全衛生的には好ましくはないと考える。技工所の管理者はドラフト設備(換気設備)を充実させることが求められ、狭い作業場では対応が厳しいことが多い。そこで有機溶剤含有接着剤を使用しないこと、内部まで耐チッピングが良好な石膏成形体の実現が望まれている。 Therefore, the effect of applying the adhesive is usually limited to the dry surface. Therefore, the cutting work is limited to either proceeding from the surface of the gypsum molded body to the inside by repeating the drying and applying the adhesive, or performing the cutting operation by applying the adhesive after sufficiently drying. Further, it is considered that it is not preferable in terms of safety and hygiene that the adhesive contains an organic solvent, because it is a work mode in which the face is brought close to the molded product. The manager of the laboratory is required to enhance draft equipment (ventilation equipment), and it is often difficult to deal with it in a small work space. Therefore, it is desired that an adhesive containing an organic solvent is not used and that a gypsum molded product having good chipping resistance even inside is realized.
歯科技工において石膏成形体を型から取り出す際にクラックが発生しないように石膏に水溶性樹脂を配合することは知られている。メチルセルロース(以下、「MC」ともいう)ポリビニルアルコール(以下、「PVA」ともいう)などが該当する。しかし、このような樹脂を配合することによって石膏成形体の圧縮強度の低下を招いていた。水溶性樹脂を配合しても圧縮強度が低下しないことは本発明まで知られていなかった。 It is known in dental technicians to incorporate a water-soluble resin into gypsum so that cracks do not occur when the gypsum compact is removed from the mold. Methyl cellulose (hereinafter, also referred to as “MC”) polyvinyl alcohol (hereinafter, also referred to as “PVA”) and the like are applicable. However, compounding such a resin causes a decrease in the compressive strength of the gypsum molded product. It has not been known until the present invention that the compressive strength does not decrease even if a water-soluble resin is added.
耐チッピング改良として抗菌性繊維の配合は知られており、特許文献2に開示される発明の目的は患者からの唾液、血液内細菌に技工士が汚染されることを防止するものではあるが、結果として耐チッピングが改良されている。同時に水性樹脂の併用も試みているが、既に抗菌性配合で耐チッピング改良が目的を達していることから、水性樹脂で耐チッピングが改良されることを示してはいない。当該特許文献2でも水溶性樹脂の配合により圧縮強度が低下することが開示されている。 The blending of antibacterial fibers is known as an improvement in chipping resistance, and the purpose of the invention disclosed in Patent Document 2 is to prevent the technician from being contaminated with saliva or blood bacteria from a patient. As a result, chipping resistance is improved. At the same time, attempts have been made to use water-based resins in combination, but it has not been shown that water-based resins improve chipping resistance, since anti-chipping resistance has already been achieved. Patent Document 2 also discloses that the compressive strength is lowered by blending a water-soluble resin.
このように、メチルセルロース(MC)やポリビニルアルコール(PVA)の配合は圧縮強度を低下させる。かかる樹脂単体での圧縮強度は石膏に比較して低い。複合則に従って配合量に依存して圧縮強度が低下すると考えるのが一般的である。一方、本発明者らの多くの実験を通じて判明したことは、かかる水溶性樹脂が石膏成形体中に存在した場合、成形体の表面で乾燥固化膜が形成されると内部の水分が蒸発揮散し難くなることである。オーブンタイプの加熱装置やマイクロウエーブ加熱装置でも表面乾燥固化膜が形成されると乾燥速度は遅くなる。水分が石膏成形体中に存在することになるので圧縮強度が更に低下する。 Thus, the compounding of methyl cellulose (MC) or polyvinyl alcohol (PVA) reduces the compressive strength. The compressive strength of such a resin alone is lower than that of gypsum. It is generally considered that the compressive strength decreases depending on the compounding amount according to the compounding rule. On the other hand, what has been found out through many experiments by the inventors of the present invention is that when such a water-soluble resin is present in a gypsum molded body, the internal moisture evaporates when a dried and solidified film is formed on the surface of the molded body. It will be difficult. Even with an oven-type heating device or a microwave heating device, the drying speed becomes slow when the surface-dried and solidified film is formed. Since the water content is present in the gypsum molding, the compressive strength is further reduced.
ここで、従来の耐チッピング、耐チッピング補修材、石膏乾燥に関する特許文献について以下に説明する。耐チッピングに関して特許文献1、2が存在する。特許文献1は、埋没石膏から義歯を取り出す際の取り出しやすさ対策として圧縮強度を低下させるための水溶性高分子を配合することが開示されているが、ポリビニルピロリドン(PVP)は記載されていない。特許文献2は、繊維状抗菌剤配合石膏により耐チッピング性及び切削加工性及び抗菌性が改良されることを開示している。 Here, patent documents relating to conventional chipping resistance, anti-chipping repair material, and gypsum drying will be described below. Patent documents 1 and 2 exist regarding chipping resistance. Patent Document 1 discloses blending a water-soluble polymer for reducing the compressive strength as a measure for easy removal when taking out a denture from a buried gypsum, but does not describe polyvinylpyrrolidone (PVP). . Patent Document 2 discloses that chipping resistance, cutting workability and antibacterial property are improved by a gypsum containing a fibrous antibacterial agent.
耐チッピング補修材に関して特許文献3がある。特許文献3は、歯科技工用石膏モデルの補修剤および補修方法を開示するものであり、シアノアクリレート系瞬間接着剤の代替として光硬化性組成物を塗布後に波長380〜600nmの光源を照射する。但し、紫外線では表面から50μmまでが到達限界である。 Patent Document 3 discloses a chipping-resistant repair material. Patent Document 3 discloses a repairing agent and a repairing method for a gypsum model for dental technology, and irradiates a light source having a wavelength of 380 to 600 nm after applying a photocurable composition as an alternative to a cyanoacrylate instant adhesive. However, with ultraviolet rays, the reaching limit is 50 μm from the surface.
石膏乾燥に関して特許文献4、5、6がある。特許文献4は石膏製歯形模型をシリカゲル粒状物中に埋没させて乾燥することを開示しており、特許文献5はタイヤ製造石膏型乾燥方法及びその装置として除湿ファン乾燥後に熱風乾燥することを開示しており、特許文献6はタイヤ成形用石膏鋳型をマイクロウエーブ加熱及び加熱雰囲気内での加熱を行って結晶水を除去することを開示している。但し、これらの文献は石膏に樹脂が配合されていない事例であり、樹脂による表面皮膜形成では参考にならない。発明者らの樹脂配合石膏組成物での実験結果では効果がないことが判明している。
また、吉野石膏のインターネットホームページには室温乾燥では1週間が推奨され、乾燥温度50〜60℃では24時間が推奨されており、70℃以上では脆くなると記載されている。There are Patent Documents 4, 5, and 6 regarding gypsum drying. Patent Document 4 discloses that a tooth model made of gypsum is embedded in silica gel granules and dried, and Patent Document 5 discloses that a method for drying a gypsum mold for tire production and its apparatus are drying with a dehumidifying fan followed by hot air drying. Patent Document 6 discloses that a gypsum mold for tire molding is heated in a microwave and heated in a heating atmosphere to remove water of crystallization. However, these documents are cases in which a resin is not mixed with gypsum, and cannot be used as a reference for forming a surface film with a resin. The results of experiments conducted by the inventors with the resin-containing gypsum composition proved to be ineffective.
In addition, one week is recommended for drying at room temperature on the Internet homepage of Yoshino Gypsum, for 24 hours at a drying temperature of 50 to 60 ° C., and brittleness is described at 70 ° C. or higher.
本発明は、耐チッピング改良として接着剤を使用せずとも作業者の安全衛生管理が可能であり、圧縮強度が低下しないかもしくは向上する水溶性樹脂を配合した石膏成形体及びその製造方法を提供することを課題とする。 The present invention provides a gypsum molded article containing a water-soluble resin that can manage the health and safety of workers without using an adhesive as an improvement in chipping resistance, and that does not reduce or improve the compressive strength, and a method for producing the same. The task is to do.
本発明者らは上記課題を解決するために、第1に耐チッピング改良として接着剤を使用せずとも作業者の安全衛生管理が可能である石膏組成物として水溶性樹脂を最適化すること、第2に水溶性樹脂の配合は一般的に圧縮強度の低下をするが圧縮強度が低下しないかもしくは向上する手法を開発すること、に注目して多くの実験を重ねて本発明に至った。 In order to solve the above-mentioned problems, the present inventors firstly optimize a water-soluble resin as a gypsum composition that enables worker safety and hygiene management without using an adhesive as an improvement in chipping resistance, Secondly, many experiments have been conducted to arrive at the present invention by paying attention to the fact that the compounding of the water-soluble resin generally reduces the compressive strength but develops a method of not reducing or improving the compressive strength.
本発明は、焼石膏100重量部に対しポリビニルピロリドン水溶液、ポリビニルアルコール水溶液、エチレン酢酸ビニル共重合体エマルジョンから選択された1つ又は2つ以上の組み合せからなる樹脂0.5〜20重量部を配合した石膏組成物に対して加水硬化する処理工程において、60℃〜230℃の乾燥処理を実施した石膏成形体であって、圧縮強度と耐チッピングに優れている石膏成形体である。また、焼石膏はα型石膏を主成分とし、成形体表面において観察されるボイド数が0.05〜0.2個/μm2であり、乾燥処理は150〜230℃の過熱水蒸気を利用する処理であり、乾燥処理装置は過熱水蒸気乾燥装置である。In the present invention, 0.5 to 20 parts by weight of a resin composed of one or a combination of two or more selected from an aqueous polyvinylpyrrolidone solution, an aqueous polyvinyl alcohol solution and an ethylene vinyl acetate copolymer emulsion is mixed with 100 parts by weight of calcined gypsum. In the process of hydrolyzing the gypsum composition described above, the gypsum molded product is a gypsum molded product that has been subjected to a drying treatment at 60 ° C to 230 ° C and is excellent in compressive strength and chipping resistance. Further, calcined gypsum has α-type gypsum as a main component, the number of voids observed on the surface of the molded body is 0.05 to 0.2 / μm 2 , and the drying treatment uses superheated steam at 150 to 230 ° C. Processing, the drying treatment device is a superheated steam drying device.
本発明の石膏成形体は歯科又は整形外科の材料として用いられ、石膏成形体の圧縮強度は水のみを配合した成形体に比して100〜150%である。また、本発明の石膏成形体の製造方法は、焼石膏100重量部に対してポリビニルピロリドン水溶液、ポリビニルアルコール水溶液、エチレン酢酸ビニル共重合体エマルジョンから選択された1つ又は2つ以上の組み合せからなる樹脂0.5〜20重量部を配合した石膏組成物を作製し、石膏組成物の加水硬化乾燥工程において、過熱水蒸気乾燥装置を用いて設定温度150〜230℃の温度領域にて10〜30分乾燥処理を実施して、圧縮強度と耐チッピングに優れた石膏成形体を得るものである。 The gypsum molding of the present invention is used as a dental or orthopedic material, and the gypsum molding has a compressive strength of 100 to 150% as compared with a molding containing only water. Further, the method for producing a gypsum molded product of the present invention comprises one or two or more combinations selected from an aqueous polyvinylpyrrolidone solution, an aqueous polyvinyl alcohol solution, and an ethylene vinyl acetate copolymer emulsion with respect to 100 parts by weight of calcined gypsum. A gypsum composition containing 0.5 to 20 parts by weight of a resin is prepared, and 10 to 30 minutes in a temperature range of a preset temperature of 150 to 230 ° C. using a superheated steam drying device in a step of hydrolyzing and drying the gypsum composition. A gypsum molded product excellent in compressive strength and chipping resistance is obtained by performing a drying treatment.
本発明によれば、切削におけるチッピングがなく、耐圧縮強度に優れた石膏成形体を得ることができる。歯科用途、工業用途などで切削不良が撲滅され生産性の向上と高価な超硬質石膏の代用として比較的経済的価格の硬質石膏が利用できることは工業用としても有意である。 According to the present invention, it is possible to obtain a gypsum molded body that is free from chipping during cutting and has excellent compression strength. It is also significant for industrial use that hard gypsum at relatively economical price can be used as a substitute for expensive ultra-hard gypsum by eliminating cutting defects in dental applications, industrial applications, etc. and improving productivity.
また、本発明においては硬質石膏の量を削減することも可能である。石膏に対する加水の割合が増えることでスラリー泥漿の取り扱いは容易になるほか膨張率も小さくなるので歯科医、歯科技工所の現場作業性からは好ましい効果が期待できる。さらに本発明によって接着剤を切削の都度塗布する必要がなくなり、有機溶剤フリーの環境での作業が可能となり安全衛生管理面でも有益である。 Further, in the present invention, it is possible to reduce the amount of hard gypsum. Increasing the ratio of water to gypsum facilitates the handling of slurry slurry and also reduces the expansion coefficient, so that a favorable effect can be expected from the field workability of dentists and dental laboratories. Further, according to the present invention, it is not necessary to apply the adhesive each time the cutting is performed, it is possible to work in an environment free of organic solvent, which is also beneficial in terms of health and safety management.
次に本発明の実施の形態について実施例、比較例を挙げて詳細に説明する。本発明の耐チッピング及び圧縮強度に優れた石膏成形体及びその製造方法は下記の実施形態及び実施例に限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変更を加えることができる。本発明は、焼石膏100重量部に対しポリビニルピロリドン水溶液、ポリビニルアルコール水溶液、エチレン酢酸ビニル共重合体エマルジョンから選択された1つ又は2つ以上の組み合せからなる樹脂0.5〜20重量部を配合した石膏組成物に対して加水硬化する処理工程において、60℃〜230℃の乾燥処理を実施した石膏成形体であって圧縮強度と耐チッピングに優れている石膏成形体である。焼石膏はα型石膏を主成分とし、成形体表面において観察されるボイド数が0.05〜0.2個/μm2であり、乾燥処理は150〜230℃の過熱水蒸気を利用する処理であり、乾燥処理装置は過熱水蒸気乾燥装置である。本発明の石膏成形体は歯科又は整形外科の材料として用いられ、石膏成形体の圧縮強度は水のみを配合した成形体に比して100〜150%である。Next, embodiments of the present invention will be described in detail with reference to examples and comparative examples. The gypsum molded article excellent in chipping resistance and compressive strength and the method for producing the same of the present invention are not limited to the following embodiments and examples, and various changes may be made within the scope not departing from the gist of the present invention. it can. In the present invention, 0.5 to 20 parts by weight of a resin composed of one or a combination of two or more selected from an aqueous polyvinylpyrrolidone solution, an aqueous polyvinyl alcohol solution and an ethylene vinyl acetate copolymer emulsion is mixed with 100 parts by weight of calcined gypsum. In the treatment step of hydrolyzing the gypsum composition described above, it is a gypsum molded product that has been subjected to a drying treatment at 60 ° C to 230 ° C and is excellent in compressive strength and chipping resistance. The calcined gypsum has α-type gypsum as a main component, the number of voids observed on the surface of the molded body is 0.05 to 0.2 pieces / μm 2 , and the drying treatment is a treatment utilizing superheated steam at 150 to 230 ° C. Yes, the drying treatment device is a superheated steam drying device. The gypsum molding of the present invention is used as a dental or orthopedic material, and the gypsum molding has a compressive strength of 100 to 150% as compared with a molding containing only water.
また、本発明の石膏成形体の製造方法は、焼石膏100重量部に対してポリビニルピロリドン水溶液、ポリビニルアルコール水溶液、エチレン酢酸ビニル共重合体エマルジョンから選択された1つ又は2つ以上の組み合せからなる樹脂0.5〜20重量部を配合した石膏組成物を作製し、石膏組成物の加水硬化乾燥工程において、過熱水蒸気乾燥装置を用いて設定温度150〜230℃の温度領域にて10〜30分乾燥処理を実施して、圧縮強度と耐チッピングに優れた石膏成形体を得るものである。
以下に本発明を構成する石膏、ポリビニルピロリドン(以下、「PVP」ともいう)、エチレン酢酸ビニル共重合体エマルジョン(以下、「EVAエマルジョン」ともいう)、ポリビニルアルコール(PVA)、乾燥について説明する。Further, the method for producing a gypsum molded product of the present invention comprises one or two or more combinations selected from an aqueous polyvinylpyrrolidone solution, an aqueous polyvinyl alcohol solution, and an ethylene vinyl acetate copolymer emulsion with respect to 100 parts by weight of calcined gypsum. A gypsum composition containing 0.5 to 20 parts by weight of a resin is prepared, and 10 to 30 minutes in a temperature range of a preset temperature of 150 to 230 ° C. using a superheated steam drying device in a step of hydrolyzing and drying the gypsum composition. A gypsum molded product excellent in compressive strength and chipping resistance is obtained by performing a drying treatment.
The gypsum, polyvinylpyrrolidone (hereinafter, also referred to as “PVP”), ethylene-vinyl acetate copolymer emulsion (hereinafter, also referred to as “EVA emulsion”), polyvinyl alcohol (PVA), and drying that constitute the present invention will be described below.
<石膏>
本発明において、焼石膏とは、土壌や溶岩などから産出される天然石膏または化学プラントから排出されて石膏が焼成されたβ型半水石膏及び加圧水蒸気処理により得られたα型半水石膏をいう。歯科技工業界ではβ型半水石膏を普通石膏と区別し、α型半水石膏を硬質石膏、超硬質石膏と区別している。普通石膏は加水量が40重量%前後で圧縮強度など機械的強度は低いが泥漿作成は容易である。安価ではあるので咬合器と歯列模型の位置決めに適用される(白色に識別されている石膏)。<Gypsum>
In the present invention, calcined gypsum refers to β-type hemihydrate gypsum obtained by natural gypsum produced from soil or lava or β-type hemihydrate gypsum discharged from a chemical plant and calcined gypsum and pressurized steam treatment. Say. In the dental industry, β-type hemihydrate gypsum is distinguished from ordinary gypsum, and α-type hemihydrate gypsum is distinguished from hard gypsum and ultra-hard gypsum. Ordinary gypsum has a low water content of about 40% by weight and has low mechanical strength such as compressive strength, but it is easy to make sludge. It is cheap and therefore applied to the positioning of articulators and dental models (white plaster).
咬合器では普通石膏の上層に硬質石膏が利用される。加水量は20%前後で得られる石膏体の硬度が高い。α型半水石膏は20%前後の低水量では過飽和状態で、硬化では一気に結晶が成長するため硬度が高いが膨張係数も大きい。さらに精密加工が求められるときは超硬質石膏が利用される(薄い茶色)。 In the articulator, hard gypsum is used as the upper layer of ordinary gypsum. When the amount of water added is about 20%, the hardness of the gypsum body obtained is high. α-type hemihydrate gypsum is in a supersaturated state at a low water content of around 20%, and has a high hardness but a large expansion coefficient because crystals grow at a stretch during hardening. When more precise processing is required, ultra-hard gypsum is used (light brown).
支台歯上で技工物の作成をする際に、幾度も技工物を抜き挿して確認及び調整をしながらの作成をする。得られた技工物を咬合器に装填し上顎歯と下顎歯の咬合状態を確認すると共に咬合応力による破損しないために十分な耐圧縮強度を有しているかを確認する。保険診療の場合は、高価な超硬質石膏は用いられず支台であっても硬質石膏が採用されている。それだけに、硬質石膏でありながら圧縮強度が改良され超硬質石膏と同様に扱うことが可能であれば大いに利便性があると言える。硬質石膏も超硬質石膏も加水量が少ないことから泥漿の粘度は高く本発明において耐チッピング性、圧縮強度改良のための水溶性樹脂配合に当たっては泥漿作業性を低下させないことが重要である。 When creating a technical product on an abutment tooth, the technical product is repeatedly inserted and extracted for confirmation and adjustment. The obtained artefact is loaded into an articulator, and the occlusal state of the upper and lower jaw teeth is confirmed, and it is confirmed that it has sufficient compressive strength to prevent damage due to occlusal stress. In the case of insurance medical care, expensive ultra-hard gypsum is not used, and hard gypsum is used even for an abutment. Therefore, it can be said that it is very convenient if the compressive strength of the hard gypsum is improved and it can be handled in the same manner as the super hard gypsum. Since both hard gypsum and ultra-hard gypsum have a small amount of water, it is important that the viscosity of the sludge is high and that the workability of the sludge is not deteriorated in the present invention when blending a water-soluble resin for improving chipping resistance and compressive strength.
本発明の焼石膏はα型石膏を主成分としているが、本発明の技術によって硬質石膏の圧縮強度が著しく向上したことにより、スラリー泥漿混合のし易さや、膨張率の低さを利用するためのβ型半水石膏を併用することが可能である。β型半水石膏においても水溶性樹脂配合及び特定乾燥条件による成形体の圧縮強度及び耐チッピング特性は水溶性樹脂無配合で通常の乾燥条件で得られる成形体の物性より優れることが本発明で実証されている。 The calcined gypsum of the present invention is mainly composed of α-type gypsum, but since the compressive strength of hard gypsum is remarkably improved by the technique of the present invention, the ease of mixing slurry slurry and the low expansion coefficient are used. The β-type hemihydrate gypsum can be used together. In β type hemihydrate gypsum, according to the present invention, the compressive strength and chipping resistance of the molded product according to the water-soluble resin composition and the specific drying conditions are superior to the physical properties of the molded product obtained under the normal drying condition without the water-soluble resin compound Has been proven.
<PVP>
本発明において使用するポリビニルピロリドン(以下、「PVP」ともいう)とはビニルピロリドン(N−ビニル−2−ピロリドンの直鎖重合体であり、ポリビニルピロリドンの製造法について特開2015−059163号公報で開示されている。ポリビニルアルコールーポリビニルピロリドングラフト共重合体について製造法が特開2008−274181号公報に開示されている。この文献によればグラフト率40%以上が得られている。またビニルピロリドンとエチレン性不飽和モノマーを重合する製造法について特開2015−168764号公報に開示されている。<PVP>
The polyvinylpyrrolidone (hereinafter, also referred to as “PVP”) used in the present invention is vinylpyrrolidone (a linear polymer of N-vinyl-2-pyrrolidone, and Japanese Patent Application Laid-Open No. 2015-059163 discloses a method for producing polyvinylpyrrolidone. A method for producing a polyvinyl alcohol-polyvinylpyrrolidone graft copolymer is disclosed in Japanese Patent Application Laid-Open No. 2008-274181. According to this document, a graft ratio of 40% or more is obtained. Japanese Patent Application Laid-Open No. 2015-168664 discloses a production method of polymerizing an ethylenically unsaturated monomer.
ポリビニルピロリドンは歴史的にみると代替血漿として広く用いられた水溶性高分子であり、人体や環境への安全性の高さと可溶化性を生かし、例えば消毒薬のポピドンヨードの原料、医療品添加物として錠剤のバインダーにも利用されている。有機溶剤を含有する瞬間接着剤の利用に比較すると安全な材料である。水やアルコール、酢酸、クロロホルム、アミン類など多くの極性溶剤に溶解し、ほかの高分子との相溶性も優れている。さらに分散性、保護コロイド性、可溶化性、被膜形成性、接着性などの特性を持ち合わせている。但し石膏への適用事例は見られない。高価であることも原因の一つである。 Polyvinylpyrrolidone has historically been a water-soluble polymer that has been widely used as an alternative plasma, and it has high safety and solubilization properties for the human body and the environment. It is also used as a tablet binder. It is a safer material compared to the use of instant adhesives containing organic solvents. It is soluble in many polar solvents such as water, alcohol, acetic acid, chloroform and amines, and has excellent compatibility with other polymers. Furthermore, it has properties such as dispersibility, protective colloid property, solubilization property, film forming property and adhesive property. However, there are no cases of application to gypsum. One of the reasons is that it is expensive.
国内製造販売会社である第一工業製薬株式会社の商品名ピッツコールは、低分子量型から高分子量型まであり、液体系および粉体の形態がある。分子量は9000〜280万まで広範囲のグレードが存在するが、石膏に利用するには石膏泥漿の攪拌、注型時の取り扱いからPVPの分子量は制約され、石膏の耐チッピング性能とのバランスで選択される。好ましい分子量として30,000以上、1200,000未満、更に好ましくは40,000以上、100,000未満である。適宜低分子量と高分子量の混合でも利用可能である。ポリビニルアルコールがPVPにグラフトした共重合タイプも利用できる。本発明においてはこれを水溶液にして使用する。 The Pittscol brand name of Daiichi Kogyo Seiyaku Co., Ltd., which is a domestic manufacturing and sales company, ranges from low molecular weight type to high molecular weight type, and has liquid and powder forms. There are a wide range of molecular weights from 9000 to 2.8 million, but for use in gypsum, the molecular weight of PVP is restricted due to the agitation of gypsum slurry and handling during casting, and it is selected in balance with the chipping resistance of gypsum. It The molecular weight is preferably 30,000 or more and less than 1.2 million, more preferably 40,000 or more and less than 100,000. It is also possible to use a mixture of a low molecular weight and a high molecular weight as appropriate. A copolymer type in which polyvinyl alcohol is grafted on PVP can also be used. In the present invention, this is used as an aqueous solution.
<ポリエチレンビニル酢酸エマルジョン;EVAエマルジョン>
本発明において使用するエチレン酢酸ビニル共重合体エマルジョン(以下、「EVAエマルジョン」ともいう)は、主としてエチレンと酢酸ビニル共重合体を、乳化剤を利用して水にエマルジョンで分散させた水溶性樹脂である。エチレンと酢酸ビニル比率は任意に決めることができる。乾燥後の弾性率やガラス転移点は酢酸ビニル濃度が50〜70重量%付近で低く、それ以外の濃度組成では高くなる傾向にある。逆に伸びは酢酸ビニル濃度が50〜70重量%付近が高い。石膏に適用するには接着性能と粒子径がポイントであり接着性を重視する場合は酢酸ビニル濃度の高いグレードを選択する。粒子径は石膏の粒子径より細かいことが重要である。多くのエマルジョンでは1ミクロン以下の平均粒子径であり石膏では全く問題がない。また固形物濃度が概ね50重量%であり分散体が水であることから石膏との泥漿作成は極めて容易である。水溶性樹脂を配合しないで水のみの加水により泥漿作成した場合とほとんど作業性は同じである。<Polyethylene vinyl acetate emulsion; EVA emulsion>
The ethylene-vinyl acetate copolymer emulsion used in the present invention (hereinafter, also referred to as "EVA emulsion") is a water-soluble resin obtained by mainly dispersing ethylene and a vinyl acetate copolymer in water using an emulsifier as an emulsion. is there. The ratio of ethylene and vinyl acetate can be arbitrarily determined. The elastic modulus and glass transition point after drying tend to be low when the vinyl acetate concentration is around 50 to 70% by weight, and tend to be high for other concentration compositions. On the contrary, the elongation is high when the vinyl acetate concentration is around 50 to 70% by weight. Adhesive performance and particle size are important points when applied to gypsum, and when importance is attached to adhesiveness, a grade with a high vinyl acetate concentration is selected. It is important that the particle size is smaller than that of gypsum. Most emulsions have an average particle size of 1 micron or less, and gypsum has no problem. Moreover, since the solids concentration is approximately 50% by weight and the dispersion is water, it is extremely easy to make a slurry with gypsum. The workability is almost the same as when the slurry is prepared by adding water only without adding a water-soluble resin.
ポリビニル酢酸エマルジョン(固形分)の石膏への配合は石膏100重量部に対し耐チッピング性では1以上20重量部であるが、本発明の石膏成形体製造法によれば3〜5重量部付近では圧縮強度が水混合石膏より高くなることが分かった。耐チッピングと圧縮強度の両方が向上することは本発明に至る前までは全く想定外の結果である。PVP等との相溶性も優れていることから泥漿作業性の面からも寄与できる。 The composition of the polyvinyl acetic acid emulsion (solid content) in gypsum is 1 to 20 parts by weight with respect to 100 parts by weight of gypsum in terms of chipping resistance, but according to the method for producing a gypsum molded body of the present invention, in the vicinity of 3 to 5 parts by weight. It was found that the compressive strength was higher than that of the water-mixed gypsum. Improvements in both chipping resistance and compressive strength are entirely unexpected results before the present invention. Since it has excellent compatibility with PVP and the like, it can also contribute from the aspect of sludge workability.
<ポリビニルアルコール(PVA)>
上記のポリビニル酢酸共重合体を鹸化しビニルアルコールとする。従って、ベース樹脂のエチレンと酢酸ビニルの重合比率と鹸化割合からなるグレードマトリックスが、用意されている。鹸化の分類として完全鹸化、部分鹸化に分かれている。PVAは水溶性ではあるが、常温では水に溶けにくいため、PVA粉末と水とを一旦98℃前後まで撹拌加熱溶解させ撹拌冷却後使用する。一般的に完全鹸化は冷却後も析出することから、部分鹸化を利用することが多い。ポリビニルアルコールと石膏の割合は、耐チッピング改良のみであれば石膏100重量部に対し1〜20重量部であるが、本発明では、ポリビニルアルコールについても3〜5重量部で圧縮強度が向上することが判明した。ポリビニルアルコールはPVP及びポリビニル酢酸共重合体水溶液とも容易に混合することがあり、三者を混合することも可能である。<Polyvinyl alcohol (PVA)>
The above polyvinyl acetic acid copolymer is saponified into vinyl alcohol. Therefore, a grade matrix consisting of the polymerization ratio of ethylene and vinyl acetate of the base resin and the saponification ratio is prepared. The saponification is classified into complete saponification and partial saponification. PVA is water-soluble, but it is difficult to dissolve in water at room temperature. Therefore, PVA powder and water are once heated to about 98 ° C. with stirring and heating, and after stirring and cooling, they are used. In general, since complete saponification is precipitated even after cooling, partial saponification is often used. The ratio of polyvinyl alcohol to gypsum is 1 to 20 parts by weight with respect to 100 parts by weight of gypsum if only the chipping resistance is improved, but in the present invention, the compressive strength of polyvinyl alcohol is improved to 3 to 5 parts by weight. There was found. Polyvinyl alcohol may be easily mixed with PVP and an aqueous solution of polyvinyl acetic acid copolymer, and it is also possible to mix the three.
<乾燥>
一般的に乾燥には自然乾燥(風乾)、熱風乾燥オーブン、除湿乾燥オーブン、真空乾燥機、マイクロウエーブ装置などが利用されている。歯科業界で石膏乾燥にはシリカゲル埋設も提案されている。歯科業界では作業のスピードを重視することから自然乾燥やシリカゲル埋設法は適用できず、その他の方法は水溶性樹脂配合がない場合は利用できるが、水溶性樹脂配合の石膏成形体の場合は、上述の如く製品表面が乾燥し成膜が生成されると内部の水分は揮発しにくい。石膏業界のインターネットホームページには、70℃を越えない条件(50〜60℃、24時間)の乾燥が推奨されているが、水溶性樹脂配合の場合では70℃以下での乾燥は時間を要する。70℃以上の条件で長時間の乾燥は、水溶性樹脂も酸化劣化することが考えられる。過熱水蒸気加熱は、酸素が存在しない水蒸気による乾燥法である。<Dry>
Generally, natural drying (air drying), a hot air drying oven, a dehumidifying drying oven, a vacuum dryer, a microwave device and the like are used for drying. In the dental industry, silica gel embedding is also proposed for gypsum drying. In the dental industry, since the speed of work is important, the natural drying and silica gel burying methods cannot be applied, and other methods can be used when there is no water-soluble resin compound, but in the case of a water-soluble resin compound gypsum molding, As described above, when the product surface is dried and a film is formed, the water content inside is less likely to volatilize. Although it is recommended to dry on the internet homepage of the gypsum industry under the condition that the temperature does not exceed 70 ° C (50 to 60 ° C, 24 hours), the drying at 70 ° C or lower takes time in the case of blending a water-soluble resin. It is considered that the water-soluble resin is oxidatively deteriorated by drying for a long time at 70 ° C. or higher. Superheated steam heating is a drying method using steam without oxygen.
過熱水蒸気生成は圧力依存性もある。従って、減圧下で過熱水蒸気による乾燥ができれば更に好ましい。歯科技工で利用される石膏成形体のサイズで、かつボイラー資格がなくても利用できる装置として、調理器具がある。過熱水蒸気は、単位体積当たりの熱容量が大きく、非常に高い熱伝導性を有することから、熱伝導性の低い空気より乾燥が速い。過熱水蒸気は、水の分子しか存在しない低酸素状態の気体であるため、被過熱物が酸化せず、また火災や爆発の危険も低い。このためレトルト食品、ハンバーグなどの調理などにも利用されているほどである。 Superheated steam generation is also pressure dependent. Therefore, it is more preferable that drying with superheated steam can be performed under reduced pressure. There is a cooking utensil as a device that can be used even in the size of a gypsum molding used in dental technicians and does not require a boiler certification. Since superheated steam has a large heat capacity per unit volume and has a very high thermal conductivity, it dries faster than air having a low thermal conductivity. Since superheated steam is a gas in a low oxygen state in which only water molecules are present, the substance to be heated does not oxidize, and the risk of fire and explosion is low. Therefore, it is even used for cooking retort foods and hamburgers.
大型装置はトクデン株式会社、新熱工業株式会社、直本工業株式会社などから調達することが可能であるが、歯科技工の対象成形体のサイズからは、家庭用過熱水蒸気調理装置で十分な機能が発揮できる。家庭調理用としての温度設定は300℃以下であるが、石膏成形体乾燥に最適条件がセット可能である。すなわち室温で泥漿を注型後室内養生後、常温から徐々に加温し、次いで230℃以下の温度領域に5〜10分静置したのち、成形体を取り出し可能の温度まで放冷し取り出す。概ね30分程度の処理時間で乾燥が達成される。 Large-scale equipment can be procured from Tokuden Co., Ltd., Shinhoku Kogyo Co., Ltd., Naomoto Kogyo Co., Ltd., etc., but due to the size of the target molded body for dental technicians, a home-use superheated steam cooker has sufficient functions. Can be demonstrated. The temperature setting for home cooking is 300 ° C. or lower, but optimum conditions can be set for drying the gypsum molding. That is, after casting the slurry at room temperature and curing it in the room, it is gradually warmed from room temperature and then allowed to stand in a temperature range of 230 ° C. or lower for 5 to 10 minutes, and then the molded body is allowed to cool to a temperature at which it can be taken out. Drying is achieved in a processing time of about 30 minutes.
230℃を超えて時間を長くすると、石膏成形体の表面はSEMで観察すると、ささくれだち状態が観察されるので好ましくない。水溶性樹脂のガラス転移点(Tg)を超える条件に加熱することで、石膏表面に付着した樹脂の分子運動が活発になり、樹脂―樹脂もしくは樹脂―非樹脂付着石膏との接着が一層強くなる。因みに、ポリビニルアルコールのガラス転移点は71℃、ポリビニルピロリドン固形単体のガラス転移点文献値は85℃であるが、水と相溶性が良好なので、ガラス転移点降下により70℃以下になるものと予想される。ポリエチレン酢酸ビニルとして、今回実施例、比較例で使用した製品スミカフレックス752のTgは15℃である。 If the temperature is longer than 230 ° C. and the time is extended, the surface of the gypsum molded product is not preferable because the surface of the gypsum molded product is observed to be frayed. By heating to a temperature exceeding the glass transition point (Tg) of the water-soluble resin, the molecular motion of the resin adhering to the gypsum surface becomes active, and the adhesion between resin-resin or resin-non-resin adhering gypsum becomes stronger. . Incidentally, the glass transition point of polyvinyl alcohol is 71 ° C, and the glass transition point of polyvinylpyrrolidone solid simple substance is 85 ° C, but since it has good compatibility with water, it is expected that it will be 70 ° C or less due to the glass transition point drop. To be done. As polyethylene vinyl acetate, the Tg of the product Sumikaflex 752 used in the examples and comparative examples this time is 15 ° C.
本発明の水溶性樹脂を配合して乾燥した石膏成形体の特徴は、石膏成形体の表面のミクロボイドの数が、水溶性樹脂を配合しない通常乾燥石膏成形体のボイドの数と比較すると少ないことにある。水溶性樹脂を配合しない石膏結晶体が、細密充填されている形態は多くの粒子間隙が形成されている。一方、本発明の水溶性樹脂を配合して乾燥した石膏成形体の表面は大型ボイドが存在し、このことでボイド数自体は少ない。逆に、表面積におけるボイド面のトータル面積は大きい。このことは、加熱により内部水分が表面噴出した痕跡と理解することができる。 The feature of the gypsum molded product obtained by mixing and drying the water-soluble resin of the present invention is that the number of microvoids on the surface of the gypsum molded product is small compared with the number of voids of the normal dry gypsum molded product that does not contain the water-soluble resin. It is in. In the form in which the gypsum crystal body containing no water-soluble resin is closely packed, many particle gaps are formed. On the other hand, there are large voids on the surface of the gypsum molded product obtained by mixing and drying the water-soluble resin of the present invention, and the number of voids per se is small. On the contrary, the total area of the void surface in the surface area is large. This can be understood as a trace that internal moisture is ejected on the surface by heating.
本発明の水溶性樹脂を配合しない場合は、石膏結晶体が密に充填されているが、いわばセメントのない石を枠の中に充填しているが如くである、垂直方向から圧縮した場合、石膏結晶体では、応力が垂直方向成分と水平方向の応力成分の合体で圧縮強度が発現するが、水平方向の耐応力は、粒子間の摩擦だけに依存するので、ズレにより圧縮強度は低くなる。さらに、切削は結晶体の粒子界面で応力集中を受けることから、結晶界面及び結晶体の破壊が生ずる。耐チッピング性が悪い原因となる。 If the water-soluble resin of the present invention is not blended, the gypsum crystal is densely packed, but it is as if the stone without cement is packed in the frame, when compressed from the vertical direction, In the gypsum crystal, compressive strength is expressed by the combination of the stress component in the vertical direction and the stress component in the horizontal direction, but since the stress resistance in the horizontal direction depends only on the friction between particles, the compressive strength becomes low due to deviation. . Further, since the cutting is subjected to stress concentration at the grain interface of the crystal body, the crystal interface and the crystal body are broken. This causes poor chipping resistance.
一方、本発明の水溶性樹脂を配合した石膏成形体は、その樹脂の粘弾性により切削においては、応力分散および緩和により剪断応力は低下することから、耐チッピング性は向上する。
石膏結晶体の表面状態を観察すると、樹脂で被覆されていることが判明するが、乾燥がどのような条件でなされたのかを判定するには、ボイドのサイズ、大口径のボイドの存在、ボイド面積の割合などが指標となる。On the other hand, the gypsum molded product containing the water-soluble resin of the present invention has improved shear resistance due to stress dispersion and relaxation in cutting due to viscoelasticity of the resin, and thus improved chipping resistance.
Observation of the surface condition of the gypsum crystal reveals that it is covered with a resin, but to determine under what conditions the drying was performed, the size of the void, the presence of a large-diameter void, the void The ratio of the area is an index.
[実施例]
次に、実施例及び比較例を挙げて、本発明を更に具体的に説明する。実施例及び比較例において使用した原料、メーカー、商品名、グレードの詳細を表1に示す。[Example]
Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Table 1 shows details of raw materials, manufacturers, trade names, and grades used in Examples and Comparative Examples.
実施例及び比較例において使用した器具、乾燥装置、評価機器、分析装置、撮像統計処理等の詳細を以下に示す。
<器具>
減圧攪拌器「レンフェルト社製、商品名:ツイスター2」
バイブレーター「株式会社ビーエスエーサクライ社製、商品名:バイブレーターB4」
圧縮強度評価作成型「シリコーン製、直径10mm、高さ25m、円柱(6個取り)」
耐チッピング評価作成型「シリコーン製、幅25mm、長さ60mm、厚さ25mmm、ブロック(2個取り)」
<乾燥装置>
加熱オーブン(強制対流オーブン)「アドバンテック東洋株式会社製、FC−410」
過熱水蒸気調理器「シャープ株式会社製、ウオーターオーブン、商品名:ヘルシオAX−CA400R」
<評価機器>
圧縮強度 「測定機:株式会社島津製作所製オートグラフ、圧縮速度:2.5mm/min
耐チッピング 彫刻刀及びカッターナイフによる手工芸評価、彫刻刀(目黒彫刻刀製作所、本喜秀、7本組のうち教材汎用三角刃)、刃物鋼付三角刃、丸刃(汎用/鋼付)を予備実験により周囲への欠け伝搬が激しい刃物鋼付三角刃を選出、精密カッターナイフ「オルファ株式会社製アートナイフプロ」
<分析装置>
走査電子顕微鏡(SEM)「株式会社日立ハイテクノロジーズ製S−3400N
エネルギー分散型X線分析装置「アメテック株式会社製、加速電圧:15KV、導電処理:白金コーティング」
<撮像統計処理>
UBE分析センター株式会社において処理した。ボイドと考えられる領域とそれ以外の領域を画像の輝度の差からある閾値を用いて二値化処理を実施し、画像解析ソフトにて統計処理データの算出を行った。画像解析ソフト「住友金属テクノロジー社製、粒子解析Ver3.5 」により測定対象ボイド数/SEM撮影面積をμm2単位当たりのボイド数とした。Details of the instruments, the drying device, the evaluation device, the analyzing device, the imaging statistical processing, and the like used in Examples and Comparative Examples are shown below.
<Apparatus>
Vacuum stirrer "Product name: Twister 2 manufactured by Renfelt"
Vibrator “BSA Sakurai Co., Ltd., product name: Vibrator B4”
Compressive strength evaluation creation type "Silicone, diameter 10mm, height 25m, column (6 pieces)"
Chipping resistance evaluation making type "Silicone, width 25mm, length 60mm, thickness 25mmm, block (2 pieces)"
<Drying device>
Heating oven (forced convection oven) "Advantech Toyo Co., Ltd., FC-410"
Superheated steam cooker "Sharp Co., Ltd., water oven, trade name: Helcio AX-CA400R"
<Evaluation equipment>
Compressive strength "Measuring machine: Shimadzu Corporation autograph, compression speed: 2.5 mm / min
Chipping resistance Evaluation of handicrafts using chisel and cutter knife, chisel (Meguro chisel mill, Yoshihide Hon, general purpose triangular blade of 7 sets), triangular blade with steel blade, round blade (general / with steel) Precision cutter knife "Olfa Corporation Art Knife Pro" was selected by a preliminary experiment by selecting a triangular blade with blade steel, which propagates sharply to the surroundings.
<Analyzer>
Scanning electron microscope (SEM) "S-3400N manufactured by Hitachi High-Technologies Corporation
Energy dispersive X-ray analyzer "Ametec Co., Ltd., accelerating voltage: 15 KV, conductive treatment: platinum coating"
<Statistical processing of imaging>
Processed at UBE Analytical Center. Binarization processing was performed on a region considered to be a void and a region other than that using a threshold value based on a difference in image brightness, and statistical processing data was calculated by image analysis software. The number of voids to be measured / SEM imaging area was defined as the number of voids per μm 2 unit by the image analysis software “Sumitomo Metal Technology Co., Ltd., Particle Analysis Ver3.5”.
石膏成形体を次のようにして製造した。撹拌機のカップに所定量の石膏、水及び表1に記載の水溶性樹脂の水溶液を入れ、撹拌棒で撹拌したのちカップを攪拌機にセットして、60〜90秒間、回転数350〜400rpmで減圧攪拌後、カップを取り外し評価用のシリコーン型にバイブレーターで加振しながら注型し、1時間養生後、型から石膏成形体を取り出す。次に実施例、比較例記載の乾燥装置及び温度条件にて乾燥する。 A gypsum molded body was manufactured as follows. Put a predetermined amount of gypsum, water and an aqueous solution of the water-soluble resin shown in Table 1 in the stirrer cup, stir with a stir bar and then set the cup in the stirrer for 60 to 90 seconds at a rotation speed of 350 to 400 rpm. After stirring under reduced pressure, the cup was removed and cast into a silicone mold for evaluation while vibrating with a vibrator, and after curing for 1 hour, the gypsum molded product was taken out from the mold. Next, it is dried under the drying apparatus and temperature conditions described in Examples and Comparative Examples.
製造した石膏成形体の耐チッピング性の評価を行った。刃物鋼付三角刃を用いて、試験片表面に、V字溝を彫ったときの切削溝内部・周囲の欠けの有無、切削表面の状態、切削屑の状態を観察した。さらに、アートナイフにて試験片の稜線部を切削したときの切削面・周囲の欠け発生の有無、切削表面の状態、切削屑の状態を観察した。それぞれの切削の総合評価を耐チッピング性とする。また、その他の評価として、作業中の臭気、成形体の外観などを観察して異常点を記録した。 The chipping resistance of the manufactured gypsum molding was evaluated. Using a triangular blade with blade steel, the presence or absence of a chip inside and around the cutting groove when the V-shaped groove was engraved on the surface of the test piece, the state of the cutting surface, and the state of cutting chips were observed. Furthermore, the presence or absence of chipping on the cutting surface / surroundings when cutting the ridge of the test piece with an art knife, the state of the cutting surface, and the state of cutting chips were observed. The chipping resistance is a comprehensive evaluation of each cutting. In addition, as other evaluations, abnormal points were recorded by observing the odor during work, the appearance of the molded product, and the like.
次に、実施例及び比較例について表2を参照して説明する。実施例1〜5、比較例1〜4において使用した配合、養生、乾燥方法、評価等を表2に示す。 Next, examples and comparative examples will be described with reference to Table 2. Table 2 shows the composition, curing, drying method, evaluation and the like used in Examples 1 to 5 and Comparative Examples 1 to 4.
第一工業製薬株式会社製PVPピッツコールK−50の12%水溶液を作製したのち、混水比(水/石膏粉)が0.24、硬質石膏97重量部に対しK−50が3重量部となるように、硬質石膏、水および当該K−50水溶液を配合調整した。これを前記の方法で減圧撹拌して均一泥漿を得た。次に、この泥漿を耐チッピング評価用型及び圧縮強度評価用型に加振注型した。その後室内で1時間養生した後、各試験片を型から取出し、対流オーブンにて設定温度70℃で、24時間乾燥した。 After preparing a 12% aqueous solution of PVP Pitzcol K-50 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., the water mixing ratio (water / gypsum powder) was 0.24, and K-50 was 3 parts by weight with respect to 97 parts by weight of hard gypsum. The hard gypsum, water and the K-50 aqueous solution were blended and adjusted so that This was stirred under reduced pressure by the above method to obtain a uniform slurry. Next, this slurry was vibrated and cast into a chipping resistance evaluation mold and a compression strength evaluation mold. Then, after curing in the room for 1 hour, each test piece was taken out from the mold and dried in a convection oven at a set temperature of 70 ° C. for 24 hours.
耐チッピングを3種類の彫刻刃及び精密カッターナイフで切削したが、クラックは、どの彫刻刀及び精密カッターによっても発生せず、耐チッピング性総合評価は良であった。室温冷却後の圧縮強度は、113MPaの結果を得た。硬質石膏と水だけのケースとして比較例1にて同様の実験をしたが、圧縮強度は92MPaであり、著しい圧縮強度の改良が確認された。先行文献等では、水溶性樹脂の配合は圧縮強度が低下するのが斯界の常識となっていたが、この実施例は想定外とも言える結果となった。 Although chipping resistance was cut with three types of engraving blades and precision cutter knives, cracks were not generated by any engraving knife and precision cutter, and the chipping resistance comprehensive evaluation was good. The compressive strength after cooling at room temperature was 113 MPa. A similar experiment was conducted in Comparative Example 1 using only hard gypsum and water, but the compressive strength was 92 MPa, and a remarkable improvement in the compressive strength was confirmed. In the prior art documents and the like, it was common knowledge in the art that the blending of the water-soluble resin resulted in a decrease in compressive strength, but this example was an unexpected result.
実施例1の配合を、PVPに代えてEVAエマルジョン;スミカフレックス752を用いて、石膏95重量部、EVA5重量部とした。実施例1と同様に、対流オーブンにて設定温度70℃で24時間乾燥した。この成形体の圧縮強度は、101MPaであった。耐チッピング性総合評価は良であった。
図1に示すように、SEM観察から得られた表面のミクロボイド数は、0.10個/μm2であった(観察面積11287μm2における総ミクロボイド数は1108個、平均ボイド径は1.0μm)。ボイド数が少なく、平均ボイド径が大きい特徴があり室温加熱との比較例1と対象的である。The composition of Example 1 was changed to PVP, EVA emulsion; Sumika Flex 752 was used to make 95 parts by weight of gypsum and 5 parts by weight of EVA. Similar to Example 1, the sample was dried in a convection oven at a set temperature of 70 ° C for 24 hours. The compression strength of this molded body was 101 MPa. The chipping resistance comprehensive evaluation was good.
As shown in FIG. 1, microvoids number of the resulting surface from the SEM observation, was 0.10 pieces / [mu] m 2 (total microvoid number 1108 or in the observation area 11287Myuemu 2, the average void diameter is 1.0 .mu.m) . It is characterized by a small number of voids and a large average void diameter, which is in contrast to Comparative Example 1 with room temperature heating.
実施例2の配合を、石膏97重量部、EVA3重量部となるように配合調整した。乾燥は、過熱水蒸気調理器にて設定温度200℃で30分間行った。圧縮強度は、113MPaと実施例2を上回る結果であった。耐チッピング性総合評価は良であった。
なお、過熱水蒸気調理器は、装置の所定タンクに注水を確認後、加温プログラムにそって処理をする。室温から設定温度200℃までに約20分で到達する。200℃を約10分間維持して合計30分間乾燥する。石膏試料を入れる前に、予め過熱水蒸気調理器庫内を加熱する予熱モードを利用すれば、より早く乾燥させることができる。The formulation of Example 2 was adjusted to 97 parts by weight of gypsum and 3 parts by weight of EVA. Drying was performed in a superheated steam cooker at a set temperature of 200 ° C. for 30 minutes. The compressive strength was 113 MPa, which was higher than that in Example 2. The chipping resistance comprehensive evaluation was good.
The superheated steam cooker processes water according to a heating program after confirming that water has been poured into a predetermined tank of the device. It takes about 20 minutes to reach the set temperature of 200 ° C. from room temperature. Hold at 200 ° C. for about 10 minutes to dry for a total of 30 minutes. If a preheating mode in which the inside of the superheated steam cooker is preheated is used before adding the gypsum sample, the gypsum sample can be dried more quickly.
実施例1のPVPに代えて、EVAエマルジョン;スミカフレックス752およびPVPピッツコールK−30Lを用いて、配合をEVA含量1.8重量部、PVP含量1.2重量部とした。乾燥方法・条件は、実施例3と同様とした。圧縮強度は123MPa、耐チッピング性総合評価は良であった。 Instead of the PVP of Example 1, EVA emulsion; Sumikaflex 752 and PVP Pitzcol K-30L were used, and the blending ratio was EVA content 1.8 parts by weight and PVP content 1.2 parts by weight. The drying method and conditions were the same as in Example 3. The compressive strength was 123 MPa, and the chipping resistance comprehensive evaluation was good.
実施例1のPVPに代えて、PVP-PVAグラフト共重合体(V−7154:固形分30%)を3重量部配合した。乾燥方法・条件は実施例3と同様とした。圧縮強度は126MPa、耐チッピング性総合評価は良であった。 Instead of the PVP of Example 1, 3 parts by weight of a PVP-PVA graft copolymer (V-7154: solid content 30%) was blended. The drying method and conditions were the same as in Example 3. The compressive strength was 126 MPa, and the chipping resistance comprehensive evaluation was good.
[比較例1]
硬質石膏に水だけの配合による成形体(混水比0.24)を、室温で24時間自然乾燥させた。圧縮強度は92MPaであって、耐チッピング性に拘りがないのであれば、室温乾燥でも十分であることがわかる。但し、切削溝内部・周囲に多数の欠けが確認され、切削面の外観は粗くギザギザが確認された。耐チッピング性総合評価は劣るレベルであった。
図2に示すように、SEM観察から得られた表面のミクロボイド数は、0.24個/μm2であった(観察面積11287μm2における総ミクロボイド数は2743個、平均ボイド径は0.7μm)。[Comparative Example 1]
A molded body (mixed water ratio 0.24) prepared by mixing only hard gypsum with water was naturally dried at room temperature for 24 hours. The compressive strength is 92 MPa, and it can be seen that room temperature drying is sufficient if the chipping resistance is not concerned. However, a large number of chips were confirmed inside and around the cutting groove, and the appearance of the cutting surface was rough and jagged. The overall chipping resistance evaluation was at an inferior level.
As shown in FIG. 2, microvoids number of the resulting surface from the SEM observation, was 0.24 pieces / [mu] m 2 (total microvoid number in the observation area 11287Myuemu 2 is 2743 pieces, the average void diameter is 0.7 [mu] m) .
[比較例2]
配合を実施例2と同様にして、乾燥を比較例1と同様に室温24時間とした場合、耐チッピング性総合評価は良であるが、圧縮強度は43MPaと圧縮強度が普通石膏レベルであって硬質石膏には及ばない。[Comparative Example 2]
When the composition was the same as in Example 2 and the drying was at room temperature for 24 hours as in Comparative Example 1, the chipping resistance comprehensive evaluation was good, but the compressive strength was 43 MPa and the compressive strength was at the level of ordinary gypsum. It does not reach hard gypsum.
[比較例3]
配合を比較例2と同様にして、乾燥を吉野石膏のホームページにあるように室温にて、1週間(168時間)風乾した。耐チッピング性総合評価は良ではあるが、圧縮強度は67MPaであった。これでも圧縮強度が硬質石膏レベルに達してはいない。[Comparative Example 3]
The composition was the same as in Comparative Example 2, and the product was air-dried at room temperature for 1 week (168 hours) as described on the website of Yoshino Gypsum. Although the chipping resistance comprehensive evaluation was good, the compressive strength was 67 MPa. Even with this, the compressive strength does not reach the level of hard gypsum.
[比較例4]
配合を比較例2と同様にして、乾燥を吉野石膏のホームページにあるように対流オーブンにて50℃で24時間とした。圧縮強度は、73MPaと樹脂配合の成形体では硬質石膏の圧縮強度を低下させてしまうことが確認された。耐チッピング性総合評価は良であった。[Comparative Example 4]
The composition was the same as in Comparative Example 2, and the drying was carried out at 50 ° C. for 24 hours in a convection oven as described on the Yoshino Gypsum website. The compressive strength was 73 MPa, and it was confirmed that the molded product containing the resin reduces the compressive strength of the hard gypsum. The chipping resistance comprehensive evaluation was good.
[比較例5]
表2には示していないが、比較例1で使用した硬質石膏に水だけの配合による石膏成形体に、石膏模型硬化剤(齋藤歯研工業所:商品名:LABOクイックラック)を塗布したのち、耐チッピング評価を実施した。その結果、切削表面は、欠けが発生せず判定は良であったが、深彫りしていくと欠けが発生し、耐チッピング性総合評価は劣ると判定された。従って、切削の都度、接着剤を塗布することが必要となる。また、有機溶媒の長期的取り扱いを技工所管理面で対策する必要がある。[Comparative Example 5]
Although not shown in Table 2, after the hard plaster used in Comparative Example 1 was coated with a plaster molding prepared by mixing only water, a plaster model curing agent (Saito Denken Co., Ltd .: trade name: LABO Quick Rack) was applied. The chipping resistance was evaluated. As a result, it was judged that the cut surface did not cause chipping and was judged to be good, but as deep cutting was carried out, chipping occurred and the chipping resistance comprehensive evaluation was inferior. Therefore, it is necessary to apply the adhesive every time cutting is performed. In addition, it is necessary to take measures for the long-term handling of organic solvents in terms of laboratory management.
上述したように、本発明によれば石膏に水及び水溶性樹脂の水溶液を配合し、特定の条件で乾燥することによって、耐チッピング性能に加えて、高い圧縮強度が得られることが判明した。これは斯界の常識や先行文献とは反対の結果である。本発明により、耐チッピング性能に加えて高い圧縮強度が得られる理由を解明すべく、以下の作業を実施した。 As described above, according to the present invention, it was found that high compressive strength can be obtained in addition to chipping resistance by mixing water and an aqueous solution of a water-soluble resin with gypsum and drying under specific conditions. This is a result contrary to common sense in the field and prior literature. The following work was carried out in order to elucidate the reason why high compressive strength can be obtained in addition to chipping resistance according to the present invention.
従来の常識・知見と反する結果について、走査型電子顕微鏡(SEM)にて石膏成形体の表面の形態を観察した。その結果、
1.石膏結晶体表面に樹脂が付着していることが観察された。石膏結晶と石膏結晶の間に樹脂が存在している箇所があることが容易に推定される。
次に、石膏結晶と石膏結晶の空間(ボイド)について、空間を二値化ソフトにより計算した。その結果、
2.比較例1は、ミクロボイド数は多いが、大きなボイドはない(平均ボイド径が0.7μm)。これに対して、実施例2では、平均ボイド径が1.0μmとむしろ大きいボイドがある。
3.上記1及び2の結果より、樹脂で結晶体が接着した構造は、柱状骨格構造体であることが判明した。
耐チッピングはカービング(この実験では彫刻刀やナイフ)により、石膏成形体に対して剪断応力による界面破壊をすることになる。上記1の観測から、樹脂が石膏結晶に付着し、石膏結晶同士に接合点がある場合は、樹脂の粘弾性に依存して剪断抵抗力が働く。このことが、耐チッピング性が改良される理由である。Regarding the results contrary to conventional common sense and knowledge, the morphology of the surface of the gypsum molded body was observed with a scanning electron microscope (SEM). as a result,
1. It was observed that the resin adhered to the surface of the gypsum crystal. It is easily presumed that the resin exists between the gypsum crystals and the gypsum crystals.
Next, regarding the space (void) between the gypsum crystal and the gypsum crystal, the space was calculated by binarization software. as a result,
2. In Comparative Example 1, the number of microvoids is large, but there are no large voids (average void diameter is 0.7 μm). On the other hand, in Example 2, some voids have an average void diameter as large as 1.0 μm.
3. From the results of 1 and 2 described above, it was found that the structure in which the crystal body was adhered with the resin was a columnar skeleton structure body.
For chipping resistance, carving (in this experiment, a chisel or knife) causes interfacial failure due to shear stress on the gypsum molding. From the observation of the above 1, when the resin adheres to the gypsum crystal and there is a joint between the gypsum crystals, the shearing resistance works depending on the viscoelasticity of the resin. This is the reason why the chipping resistance is improved.
一方で、樹脂が存在しながら圧縮強度が低下しないのは、単純な強度の複合則では整理できないことを示している。自然乾燥ではなく、過熱水蒸気による加熱処理は高温であり、内部水分は突沸しながら表面に水分を解放する。それば、大きなボイドを形成することにつながっている。大きなボイドを形成した結果は、石膏結晶体が円周方向に配向され、結果として柱状、円筒状の骨格構造を取る。図1の奥の内部に、その形態を観ることができる。骨格構造は、建築のトラスト構造などに見られるように、剛性(圧縮強度)変形歪みの低下をもたらすことは、多くの事例にみることができる。 On the other hand, the fact that the compressive strength does not decrease despite the presence of the resin indicates that the simple composite rule of strength cannot be arranged. The heat treatment with superheated steam is not a natural drying, but the heat treatment is at a high temperature, and the internal moisture releases water to the surface while bumping. That leads to the formation of large voids. The result of forming large voids is that the gypsum crystal is oriented in the circumferential direction, resulting in a columnar or cylindrical skeletal structure. The form can be seen inside the back of FIG. It can be seen in many cases that the skeletal structure brings about a reduction in rigidity (compressive strength) deformation strain, as seen in a building trust structure and the like.
本発明は、美術、工作物のみならず、タイヤ製造時の型に利用するなど工業用途に広く利用することができ、歯科及び整形外科の材料として利用することができる。
INDUSTRIAL APPLICABILITY The present invention can be widely used not only for arts and works, but also for industrial purposes such as molds for tire production, and can be used as a material for dental and orthopedic surgery.
Claims (4)
前記石膏組成物の加水硬化乾燥工程において、過熱水蒸気乾燥装置を用いて設定温度150〜230℃の温度領域にて10〜30分乾燥処理を実施して、圧縮強度と耐チッピングに優れた石膏成形体を得ることを特徴とする石膏成形体の製造方法。 A gypsum composition in which 0.5 to 20 parts by weight of a resin, which is one or a combination of two or more selected from an aqueous polyvinylpyrrolidone solution, an aqueous polyvinyl alcohol solution, and an ethylene vinyl acetate copolymer emulsion, is mixed with 100 parts by weight of hard gypsum. Make things,
In the step of hydrolyzing and drying the gypsum composition, a gypsum molding excellent in compressive strength and chipping resistance is performed by using a superheated steam dryer to perform a drying treatment in a temperature range of a set temperature of 150 to 230 ° C. for 10 to 30 minutes. A method for producing a gypsum molded body, which comprises obtaining a body.
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JPS52121629A (en) * | 1976-04-07 | 1977-10-13 | Nippon Synthetic Chem Ind | Method of manufacturing composite material of gypsum system |
JPS57106560A (en) * | 1980-12-23 | 1982-07-02 | Showa Highpolymer | Colored inorganic hydrated hardened matter |
JPH05319890A (en) * | 1992-05-13 | 1993-12-03 | Kuraray Co Ltd | Gypsum composition |
JPH07317162A (en) * | 1994-05-25 | 1995-12-05 | Nippon Kayaku Co Ltd | Humidity conditioning composite material |
WO2007122804A1 (en) * | 2006-04-21 | 2007-11-01 | Next21 K.K. | Figure-forming composition, process for production of figures in three dimensions by using the composition and process for production of three-dimensional structures |
WO2017135250A1 (en) * | 2016-02-02 | 2017-08-10 | 吉野石膏株式会社 | Calcined gypsum treatment device and calcined gypsum treatment method |
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JPS52121629A (en) * | 1976-04-07 | 1977-10-13 | Nippon Synthetic Chem Ind | Method of manufacturing composite material of gypsum system |
JPS57106560A (en) * | 1980-12-23 | 1982-07-02 | Showa Highpolymer | Colored inorganic hydrated hardened matter |
JPH05319890A (en) * | 1992-05-13 | 1993-12-03 | Kuraray Co Ltd | Gypsum composition |
JPH07317162A (en) * | 1994-05-25 | 1995-12-05 | Nippon Kayaku Co Ltd | Humidity conditioning composite material |
WO2007122804A1 (en) * | 2006-04-21 | 2007-11-01 | Next21 K.K. | Figure-forming composition, process for production of figures in three dimensions by using the composition and process for production of three-dimensional structures |
WO2017135250A1 (en) * | 2016-02-02 | 2017-08-10 | 吉野石膏株式会社 | Calcined gypsum treatment device and calcined gypsum treatment method |
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