【発明の詳細な説明】[Detailed description of the invention]
本発明は改良されたカルシウムアルミネート系
赤外線放射材料に関する。
赤外線放射エネルギーを加熱用、乾燥用に利用
する技術はよく知られている。その被熱物、すな
わちタンパク質、脂肪、水などが数μ以上の赤外
線吸収特性を有することから、それに適した赤外
線放射材料として粘土、ジルコン、コーデイエラ
イト、ジルコニア、アルミナ等を主成分としたセ
ラミツクス系赤外線放射材料が種々公開されてい
る。本願発明者も6μ以上の長波長域の放射率を
改善したカルシウムアルミネート系赤外線放射材
料を開発し、先に特許出願した（特願昭56−
167888号）。
しかし上述の被熱物は長波長の吸収特性に大き
い特徴を有するが、短波長域の放射エネルギー量
も乾燥操作上には重要なフアクターである。
Planckの輻射式にしたがえば100〜1000℃での黒
体の放射エネルギーは主に6μ以下の波長であり、
この領域における放射率が高い程全放射エネルギ
ーは大きい。しかるに従来の赤外線放射材料は主
に長波長域を目標として開発されたものであり、
短波長での放射率が非常に小さい。つまり全放射
エネルギーが小さく乾燥等の効率が低かつた。
本発明はかかる事情に鑑みなされたもので、そ
の目的はAl2O3―CaO系赤外線放射材料が短波長
側、特に6μ以下の波長の放射率を改善すること
にある。すなわち本発明の要旨はAl2O3とCaOを
主成分とする赤外線放射組成物に、該組成物に対
し10〜90重量％の鉄、コバルト、ニツケル、クロ
ム、マンガンの酸化物を１種以上含有させた焼結
体からなる赤外線放射材料である。
本発明の赤外線放射材料を製造するにあたつて
その主成分たるAl2O3とCaOは、Al2O3とCaOの
合計量に対しAl2O3が78〜97重量％（以下％と表
示する）の範囲に原料配合することが好ましく、
Al2O3が78％未満では製造過程で前記材料中に水
硬性のCaO・Al2O3が生成し、特に65％以下にな
ると水和活性な3CaO・Al2O3が生成し、水分を
含む雰囲気では水との反応によつて前記材料の劣
化のおそれが生じる。またAl2O3含有量が97％を
超えれば未反応のAl2O3が増加するため赤外線放
射強度が低くなり、特に10μ以上の長波長域でこ
の傾向が著しく、さらに赤外線放射強度も小さく
なるので好ましくない。
本発明において主成分のAl2O3―CaO系赤外線
放射材料組成物に添加される金属の酸化物は鉄、
コバルト、ニツケル、クロム、マンガンであり、
これらのうちいずれの金属酸化物を選択使用して
も同程度の効果を奏するし、勿論１種以上併用す
ることも可能である。これら金属酸化物は上記組
成物に対し10〜90％（外割）加えられるのが好ま
しく、10％未満では6μ以下での放射率が低く添
加効率がなく、90％を超えるを10μより長波長で
の放射率が低下するので好ましくない。
本発明に使用されるAl2O3源としては市販のア
ルミナや水酸化アルミニウム、硫酸アルミニウム
等のアルミニウム塩類があげられ、CaO源として
は市販の生石灰、消石灰、炭酸カルシウム等があ
げられる。また金属酸化物源としては市販の酸化
鉄、酸化コバルト、酸化ニツケル、酸化クロム、
弁がら、クロム鉄鉱、赤鉄鉱、磁鉄鉱、マンガン
カンラン石等があげられる。
これらの原料を所定量秤量し、44μ篩残分が３
％以下になる迄混合粉砕する。ついでこの混合物
を中空円筒状または板状として成形する。成形に
あたつて適宜アラビアノリ、メチルセルローズ、
ポリビニルアルコール等のバインダーを、さらに
必要に応じ水を加えて真空土練機またはロールミ
ルで十分混練した後、押出し成形または加圧成形
を行なう。（なお本発明に係る材料を用いて成形
する際には適宜に水を添加することは差支えない
ので以下の説明では水については省略する）。ま
た成形にあたつては粘土を上記バインダーと併用
することにより、より一層の成形性向上を達成で
きる。勿論粘土添加による組成変動は前記要旨に
示した範囲でなければならないが、その添加量は
Al2O3―CaO―金属酸化物の混合物に対して外割
で15％以下が望ましい。粘土としては本山木節粘
土、土岐口蛙目土等があげられる。上記以外にも
ベントナイト、カオリンを加えればAl2O3―CaO
混合原料の成形性が向上する。
さらに成形後のハンドリングを容易にする目的
からAl2O3源およびCaO源の一部としてアルミナ
セメントを使用することができる。その場合には
成形後硬化し始め、数十分後にはその成形体を自
由に持ち運びし得る程度の機械的強度を発現し、
その後の乾燥、焼成工程における取扱いを容易に
する。なお粘土あるいはアルミナセメントを添加
した場合にはAl2O3およびCaOの成分調整をする
必要がある。
上記のようにして得られた各原材料を適宜配合
した混合物を中空円筒状ないし板状に成形した
後、110℃で乾燥し慣用の電気炉等で焼成を行な
う。焼成は1200〜1600℃の温度で20分以上保持
し、その後放冷して本発明の赤外線放射材料が得
られる。焼成温度は予め同一組成物を昇温させな
がら収縮率を連続測定し、収縮開始温度と引続き
生じる軟化開始温度との中間附近とした。
次に実施例によつて本発明をさらに詳細に説明
する。ここで使用材料の赤外線放射特性を調べる
方法として赤外線の放射率を測定するか、または
水を加熱した際の温度上昇のいずれかを測定し
た。
すなわち前者の測定は以下のようにして行なつ
た。赤外分光度計を用いて放射率既知の疑似黒体
（基準光源）と放射率未知の赤外線放射材料との
比を測定して放射率を得た。
実験例 １
純薬Al2O385％と同CaO15％からなる組成物に
Fe2O3、Co3O4、NiO、Mn3O4、Cr2O3の各純薬
をそれぞれ第１表に示すように配合し、44μ篩残
分が2.9％になるように乾式混合粉砕した。
この混合物に５％ポリビニルアルコール水溶液
を８％加え慣用の方法で十分混練した後40×20×
６mmの板状に成形した。この成形体を110℃で１
時間乾燥し第１表に記載された温度で１時間焼成
した後放冷した。
得られた焼結板の他面を加熱し、赤外線を放射
する一方の表面温度を510℃と一定にして放射率
を測定した。その結果を第１図に示す。図より金
属酸化物をAl2O3―CaO混合原材料に対して外割
で10〜90％加えると放射率の向上が見られる。10
％未満では6μ以下での放射率が低く、90％を超
えるとAl2O3―CaO系セラミツクスの特徴である
10μ以上での放射率が著しく低下する。
The present invention relates to improved calcium aluminate-based infrared emitting materials. The use of infrared radiant energy for heating and drying purposes is well known. Since the materials to be heated, such as proteins, fats, and water, have infrared absorption characteristics of several microns or more, ceramics mainly composed of clay, zircon, cordierite, zirconia, alumina, etc. are suitable infrared emitting materials. Various types of infrared emitting materials have been published. The inventor of this application also developed a calcium aluminate-based infrared emitting material with improved emissivity in the long wavelength range of 6μ or more, and previously filed a patent application (Japanese Patent Application No. 1983-
No. 167888). However, although the above-mentioned object to be heated has a large characteristic of absorbing long wavelengths, the amount of radiant energy in the short wavelength range is also an important factor in drying operations.
According to Planck's radiation equation, the radiant energy of a black body at 100 to 1000 degrees Celsius is mainly at a wavelength of 6μ or less,
The higher the emissivity in this region, the greater the total radiated energy. However, conventional infrared emitting materials were developed mainly for the long wavelength range.
Emissivity at short wavelengths is very low. In other words, the total radiant energy was small and the efficiency of drying etc. was low. The present invention was made in view of the above circumstances, and its purpose is to improve the emissivity of an Al 2 O 3 --CaO-based infrared emitting material on the short wavelength side, particularly at wavelengths of 6 μ or less. That is, the gist of the present invention is to add one or more oxides of iron, cobalt, nickel, chromium, and manganese to an infrared emitting composition containing Al 2 O 3 and CaO as main components, in an amount of 10 to 90% by weight based on the composition. This is an infrared emitting material made of a sintered body containing In producing the infrared emitting material of the present invention, the main components, Al 2 O 3 and CaO, are such that Al 2 O 3 is 78 to 97% by weight (hereinafter referred to as %) based on the total amount of Al 2 O 3 and CaO. It is preferable to mix raw materials within the range of (displayed),
If the Al 2 O 3 content is less than 78%, hydraulic CaO/Al 2 O 3 will be generated in the material during the manufacturing process, and if it is less than 65%, hydration-active 3CaO/Al 2 O 3 will be generated and water will be removed. In an atmosphere containing water, there is a risk of deterioration of the material due to reaction with water. Furthermore, if the Al 2 O 3 content exceeds 97%, unreacted Al 2 O 3 increases, so the infrared radiation intensity decreases, and this tendency is particularly noticeable in the long wavelength range of 10 μ or more, and the infrared radiation intensity also decreases. This is not desirable. In the present invention, the metal oxides added to the main component Al 2 O 3 -CaO-based infrared emitting material composition are iron,
cobalt, nickel, chromium, manganese,
Selecting and using any of these metal oxides will produce similar effects, and of course it is also possible to use one or more metal oxides in combination. It is preferable that these metal oxides be added in an amount of 10 to 90% (externally divided) to the above composition; if it is less than 10%, the emissivity at 6μ or less is low and there is no addition efficiency; if it exceeds 90%, the wavelength is longer than 10μ. This is not preferable because the emissivity at Examples of the Al 2 O 3 source used in the present invention include commercially available alumina, aluminum salts such as aluminum hydroxide and aluminum sulfate, and examples of the CaO source include commercially available quicklime, slaked lime, calcium carbonate, and the like. In addition, as metal oxide sources, commercially available iron oxide, cobalt oxide, nickel oxide, chromium oxide,
Examples include valve rat, chromite, hematite, magnetite, manganese olivine, etc. Weigh the specified amount of these raw materials and make sure that the residue on the 44μ sieve is 3
% or less. This mixture is then shaped into a hollow cylinder or plate. Arabic nori, methyl cellulose,
After a binder such as polyvinyl alcohol is thoroughly kneaded with water added if necessary using a vacuum kneader or a roll mill, extrusion molding or pressure molding is performed. (Note that water may be added as appropriate when molding using the material according to the present invention, so water will be omitted in the following explanation). In addition, when molding, by using clay together with the above-mentioned binder, further improvement in moldability can be achieved. Of course, the compositional change due to the addition of clay must be within the range shown in the summary above, but the amount added is
It is desirable that the amount is 15% or less based on the Al 2 O 3 -CaO-metal oxide mixture. Examples of clay include Motoyama Kibushi clay and Tokiguchi Kame clay. In addition to the above, if bentonite and kaolin are added, Al 2 O 3 -CaO
The moldability of mixed raw materials is improved. Furthermore, for the purpose of facilitating handling after molding, alumina cement can be used as part of the Al 2 O 3 source and CaO source. In that case, it begins to harden after molding, and after several tens of minutes, the molded product develops mechanical strength that allows it to be carried freely.
It facilitates handling in the subsequent drying and firing steps. Note that when clay or alumina cement is added, it is necessary to adjust the components of Al 2 O 3 and CaO. A mixture of the raw materials obtained as described above is formed into a hollow cylinder or plate, dried at 110° C., and fired in a conventional electric furnace or the like. The calcination is maintained at a temperature of 1200 to 1600°C for 20 minutes or more, and then allowed to cool to obtain the infrared emitting material of the present invention. The firing temperature was determined by continuously measuring the shrinkage rate while raising the temperature of the same composition in advance, and was set to be approximately midway between the shrinkage start temperature and the subsequent softening start temperature. Next, the present invention will be explained in more detail with reference to Examples. In order to investigate the infrared radiation characteristics of the materials used here, either the infrared emissivity was measured or the temperature rise when water was heated was measured. That is, the former measurement was performed as follows. Using an infrared spectrometer, the emissivity was obtained by measuring the ratio between a pseudo black body (reference light source) with a known emissivity and an infrared emitting material with an unknown emissivity. Experimental example 1 A composition consisting of 85% pure Al 2 O 3 and 15% CaO
The pure chemicals Fe 2 O 3 , Co 3 O 4 , NiO, Mn 3 O 4 , and Cr 2 O 3 were mixed as shown in Table 1 and dry mixed so that the residue on the 44 μ sieve was 2.9%. Shattered. Add 8% of 5% polyvinyl alcohol aqueous solution to this mixture and thoroughly knead by a conventional method.
It was molded into a 6 mm plate. This molded body was heated to 110℃ for 1
After drying for an hour and baking at the temperature listed in Table 1 for 1 hour, the mixture was allowed to cool. The other side of the obtained sintered plate was heated, and the emissivity was measured while keeping the temperature of the one surface that emits infrared rays constant at 510°C. The results are shown in FIG. The figure shows that when 10 to 90% of the metal oxide is added to the Al 2 O 3 -CaO mixed raw material, the emissivity improves. Ten
If it is less than %, the emissivity is low below 6μ, and if it exceeds 90%, it is a characteristic of Al 2 O 3 -CaO ceramics.
Emissivity drops significantly above 10μ.
【表】
実験例 ２
純薬Al2O3および同CaOをそれぞれ第２表に示
すように配合し、その混合物に純薬のFe2O3、
Co3O4、NiO、Mn3O4、Cr2O3を各々外割で8.0％
添加し、実験例１と同様な方法で粉砕、混合、成
形、乾燥、を行ない1270℃で２時間焼成した後放
冷した。
これらの焼結体の放射率を測定した結果、第１
図の曲線No.７〜９と同程度の値を示すことが認め
られた。[Table] Experimental Example 2 Pure chemicals Al 2 O 3 and CaO were mixed as shown in Table 2, and pure chemicals Fe 2 O 3 and CaO were added to the mixture.
Co 3 O 4 , NiO, Mn 3 O 4 , Cr 2 O 3 each at 8.0%
The mixture was then crushed, mixed, molded, and dried in the same manner as in Experimental Example 1. After baking at 1270°C for 2 hours, the mixture was allowed to cool. As a result of measuring the emissivity of these sintered bodies, the first
It was observed that the values were comparable to those of curves Nos. 7 to 9 in the figure.
【表】
実験例 ３
第１表No.７の組成物およびジルコン30％、
TiO230％、粘土20％、Mn2O34％、Fe2O38％、
Cr2O38％からなる公知の組成物の両者を実験例
１の要領で混練し、外径14mm、内径10mm、長さ
300mmの円筒管状に押出し成形し、110℃で１時間
乾燥し、前者は1270℃、45分間、後者は1380℃、
４時間の焼成を行なつた。
それぞれの円筒管内部にニクロム線発熱体
（150ワツト）を挿入して赤外線放射素子を作成
し、通電して当該表面から放射する赤外線によつ
て1.5の水を撹拌しつつ加熱し、その温度上昇
の経時変化を調べた。
その結果を第２図に示すが、従来の材料により
作製した赤外線放射材料に比し本発明に係わる物
の方が加熱特性が良好であつた。
実験例 ４
出発原料としてアルミナセメント84.5重量部と
市販のAl2O3粉末15.5重量部を混合し、この混合
物に弁がら、酸化コバルトを各々外割で15％加
え、44μふるい残分2.7％となる迄乾式で混合粉砕
した。
この混合物に５％ポリビニルアルコール水溶液
及び土岐口蛙目粘度を外割で各々11％加え、慣用
の方法で十分混練した後、40×20×６mmの板状に
成形し、乾燥後1250℃で２時間焼成した。
この焼成体の放射率を実験例１と同様な方法に
より測定した。放射率は第１図の５，６とほぼ同
じ値であつた。[Table] Experimental Example 3 Composition of Table 1 No. 7 and 30% zircon,
TiO2 30%, clay 20%, Mn2O3 4 %, Fe2O3 8 %,
Both of the known compositions consisting of 8% Cr 2 O 3 were kneaded in the same manner as in Experimental Example 1, and the outer diameter was 14 mm, the inner diameter was 10 mm, and the length was
It was extruded into a 300mm cylindrical tube shape and dried at 110℃ for 1 hour, the former at 1270℃ for 45 minutes, the latter at 1380℃,
Firing was performed for 4 hours. Insert a nichrome wire heating element (150 watts) inside each cylindrical tube to create an infrared radiating element, turn on electricity, and use the infrared rays emitted from the surface to stir and heat 1.5 water, raising its temperature. We investigated changes over time. The results are shown in FIG. 2, and the heating characteristics of the material according to the present invention were better than that of infrared emitting materials made from conventional materials. Experimental Example 4 As a starting material, 84.5 parts by weight of alumina cement and 15.5 parts by weight of commercially available Al 2 O 3 powder were mixed, and to this mixture was added 15% of each of valve shells and cobalt oxide, and the remaining amount after sieving through a 44μ sieve was 2.7%. The mixture was mixed and ground in a dry manner until the mixture was mixed and pulverized. To this mixture, 11% each of a 5% polyvinyl alcohol aqueous solution and Tokiguchi Frogme viscosity were added, and after thorough kneading by a conventional method, it was formed into a plate shape of 40 x 20 x 6 mm, and after drying, it was heated at 1250℃ for 2 hours. Baked for an hour. The emissivity of this fired body was measured in the same manner as in Experimental Example 1. The emissivity was approximately the same value as 5 and 6 in FIG.
【表】【table】
【図面の簡単な説明】[Brief explanation of drawings]
第１図は第１表に記載された各種組成物の放射
率の測定結果であり、第２図は水の加熱実験の結
果を示すグラフである。
FIG. 1 shows the measurement results of the emissivity of the various compositions listed in Table 1, and FIG. 2 is a graph showing the results of a water heating experiment.