JP2005219945A - Light precipitated calcium carbonate-silica composite - Google Patents
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本発明は、填料や顔料として紙に使用される無機複合粒子に関するものであり、具体的には、軽質炭酸カルシウムとシリカの複合物に関するものである。該軽質炭酸カルシウム−シリカ複合物は、軽質炭酸カルシウム由来の高白色度、高い比散乱係数(高不透明性)という性状と、シリカ由来の高吸油量、嵩高という性状を併せ持つ複合物である。本発明の軽質炭酸カルシウム−シリカ複合物は、これらの性状に加えて、製紙工程中のカレンダー処理やスーパーキャレンダー処理を受けても潰れ難いという性状を有する複合物である。 The present invention relates to inorganic composite particles used for paper as a filler or pigment, and specifically to a composite of light calcium carbonate and silica. The light calcium carbonate-silica composite is a composite having properties of high whiteness and high specific scattering coefficient (high opacity) derived from light calcium carbonate, high oil absorption and bulkiness derived from silica. In addition to these properties, the light calcium carbonate-silica composite of the present invention is a composite that has the property that it is not easily crushed even when subjected to calendaring or supercalendering during the papermaking process.
一般に抄紙を行う場合、その紙質改善を目的として、パルプ繊維以外に填料と呼ばれる無機系微粒子を内添、含有させる場合が多い。填料はその種類により、不透明度、白色度等の光学的性質を改善する効果が高いもの、填料自身の高吸油性による印刷時の裏移りや裏抜けを防止するものなどがある。更に近年では、環境問題や輸送時のコスト削減、紙ユーザーに高級感を感じさせるため、低密度(嵩高)で高不透明度の紙が多く求められるようになり、このような品質を付加できる高性能な填料の開発が望まれている。 In general, when making paper, in order to improve the paper quality, inorganic fine particles called fillers are often added and contained in addition to pulp fibers. Depending on the type of filler, there are those that are highly effective in improving optical properties such as opacity and whiteness, and those that prevent set-off and show-through during printing due to the high oil absorption of the filler itself. Furthermore, in recent years, low density (bulk) and high opacity paper has been increasingly demanded in order to reduce environmental issues, transportation costs, and make paper users feel high-quality. Development of a high-performance filler is desired.
現在抄紙に用いられている填料には、タルク、カオリン、重質炭酸カルシウム、チョークのように鉱山より採石された石を、そのまま、または過酸化水素等漂白薬品で高白色化した後、分級または粉砕して平均粒子径を調整して用いる天然鉱物型のものと、軽質炭酸カルシウムやケイ酸の非晶質凝集物であるシリカのように、化学反応を経て得られる合成型のものに大別される。この合成型填料は合成反応時または反応後に、分級または粉砕して平均粒子径を調整して用いられることもある。 The fillers currently used for papermaking include talc, kaolin, heavy calcium carbonate, and stones quarried from the mine, either as they are or after whitening with bleaching chemicals such as hydrogen peroxide, Natural mineral type that is used by adjusting the average particle size by grinding, and synthetic type that is obtained through chemical reaction, such as silica, which is an amorphous aggregate of light calcium carbonate and silicic acid Is done. This synthetic filler is sometimes used after the synthesis reaction or after the reaction by classification or pulverization to adjust the average particle size.
軽質炭酸カルシウムは、生石灰を水中で消和し、生成した水酸化カルシウムのスラリーに、二酸化炭素または炭酸ナトリウムを添加し、炭酸化反応させることで製造されている。この軽質炭酸カルシウムは、反応温度や軽カル濃度、攪拌条件の違いにより、米粒状やいがぐり状、針状、球状、繊維状などの種々の形状をとる。 Light calcium carbonate is manufactured by dehydrating quick lime in water and adding carbon dioxide or sodium carbonate to the resulting calcium hydroxide slurry to cause a carbonation reaction. This light calcium carbonate takes various shapes such as rice grain shape, sawtooth shape, needle shape, spherical shape, and fiber shape, depending on the reaction temperature, light calcium concentration, and stirring conditions.
一方シリカは、アルカリ性であるケイ酸アルカリと、硫酸を代表とする鉱酸との中和反応により製造する方法が一般的である。この方法で製造されたシリカは、アルカリ側から反応が行われたものは沈降法シリカ、酸性側から反応が行われたものはゲル法シリカと呼ばれ、これらシリカは一次粒子が不定形に二次凝集した非晶質結晶であるため、決まった形状を持たないが、これも反応開始温度や攪拌条件、さらに酸添加速度等を変化させることで、吸油量や比表面積等の諸物性が大きく変化することが知られている。この他、四塩化珪素を気層中で燃焼させることにより得られる気層法(無水)シリカや、ケイ酸アルカリのナトリウムイオンをイオン交換樹脂などで水素イオンに置換し、一次粒子が凝集しないような形状にしたコロイダルシリカなどもあるが、これらの方法では、一次粒子が単独で存在する形状をとることに特徴がある。 On the other hand, silica is generally produced by a neutralization reaction between alkaline alkali silicate and a mineral acid typified by sulfuric acid. The silica produced by this method is called precipitated silica when the reaction is performed from the alkali side, and gel silica when the reaction is performed from the acidic side. Since it is an agglomerated amorphous crystal, it does not have a fixed shape, but it also has various physical properties such as oil absorption and specific surface area by changing the reaction start temperature, stirring conditions, and acid addition rate. It is known to change. In addition, gas phase method (anhydrous) silica obtained by burning silicon tetrachloride in the gas phase and sodium ions of alkali silicate are replaced with hydrogen ions with ion exchange resin so that primary particles do not aggregate. Although there are colloidal silica having various shapes, these methods are characterized in that they have a shape in which primary particles exist alone.
この軽質炭酸カルシウムとシリカは、いずれも抄紙用の内添填料としては広く普及しているが、それぞれの物性に特徴があり、填料として用いた場合、異なる効果を示す。まず、シリカは、非晶質であるため粒子内に微細な細孔が多数存在し、このため吸油量が高く、填料として用いた場合には、印刷時のインクの裏移りや裏抜けの防止効果が高い。また填料自身が嵩高であるため、他の填料と比較した場合、嵩高な紙を製造することができる。一方、軽質炭酸カルシウムは、その形状や平均粒子径により効果発現の程度が様々であるが、一般的に、光散乱程度を表す比散乱係数はシリカより高く、不透明度改善効果が大きい。また、内添填料として紙に用いた場合、シリカに比べ紙の強度低下は低く、さらに比較的安価であるため、紙へ高配合することも可能である。 Both light calcium carbonate and silica are widely used as internal fillers for papermaking, but they are characterized by their physical properties and show different effects when used as fillers. First, since silica is amorphous, there are a lot of fine pores in the particles. Therefore, the oil absorption is high, and when used as a filler, it prevents ink back-off and back-through. High effect. Further, since the filler itself is bulky, a bulky paper can be produced when compared with other fillers. On the other hand, light calcium carbonate has various effects depending on its shape and average particle diameter. In general, however, the specific scattering coefficient representing the degree of light scattering is higher than that of silica, and the effect of improving opacity is great. Further, when used for paper as an internal filler, the strength reduction of the paper is lower than that of silica, and it is relatively inexpensive, so that it can be highly blended into the paper.
このように、軽質炭酸カルシウムは光学的特性の向上効果が高く、シリカは嵩高で、高吸油性のため印刷時の裏移りや裏抜け防止効果が高い、という優れた特徴をもつ。これらの光学的特性向上効果、嵩高効果、高吸油性(裏移り防止効果、裏抜け防止効果)などの性質を兼ね備えた填料を製造することができれば、抄紙において非常に有益であり、その開発が望まれていた。また、同様な性質を有する塗工用の顔料の開発も望まれていた。 As described above, light calcium carbonate has an excellent effect of improving optical characteristics, and silica is bulky and has a high oil-absorbing property, so that it has a high effect of preventing set-off and back-through during printing. If it is possible to produce fillers that combine these properties such as optical properties improvement effect, bulkiness effect, high oil absorption (back-off prevention effect, back-through prevention effect), etc., it will be very beneficial in papermaking, and its development will be It was desired. It has also been desired to develop coating pigments having similar properties.
ここで、これらの性質を紙に付与するため、軽質炭酸カルシウムとシリカの２種類の填料を紙に配合することが考えられる。しかし、軽質炭酸カルシウムとシリカを配合した場合には、シリカ単独配合時よりも嵩高向上効果が低く、また軽質炭酸カルシウム単独配合時よりも不透明度が低くなることが知られており、問題解決には至っていない。 Here, in order to impart these properties to the paper, it is conceivable to mix two kinds of fillers of light calcium carbonate and silica into the paper. However, it is known that when light calcium carbonate and silica are blended, the bulkiness improvement effect is lower than when silica is blended alone, and the opacity is lower than when light calcium carbonate is blended alone. Has not reached.
炭酸カルシウムとシリカとの複合物に関する従来の技術としては、以下の文献がある。
例えば、炭酸カルシウム粒子の核と、該核に化学結合したケイ酸および／またはケイ酸塩の被覆層とからなる複合改質顔料が開示され、炭酸カルシウム粒子表面におけるケイ酸またはケイ酸塩との反応は、炭酸カルシウム粒子を塩酸、硫酸などの無機酸で処理し、表面を活性化し、次いでケイ酸および／またはケイ酸塩の反応成分と反応させることで製造されることが記載されている(特許文献１参照)。しかし、この方法では、炭酸カルシウムを予め無機酸で処理することが必要であり、製造工程が複雑であり、しかもこの無機酸が炭酸カルシウムを分解するという問題がある。
The following documents are known as conventional techniques related to a composite of calcium carbonate and silica.
For example, a composite modified pigment comprising a core of calcium carbonate particles and a coating layer of silicic acid and / or silicate chemically bonded to the core is disclosed. The reaction is described as being produced by treating calcium carbonate particles with an inorganic acid such as hydrochloric acid, sulfuric acid, activating the surface and then reacting with the reaction components of silicic acid and / or silicate ( (See Patent Document 1). However, in this method, it is necessary to treat calcium carbonate with an inorganic acid in advance, the manufacturing process is complicated, and there is a problem that this inorganic acid decomposes calcium carbonate.
一方、合成シリカを炭酸カルシウム製造時(炭酸化反応時)に加え、合成シリカと炭酸カルシウムを複合化させ、炭酸カルシウムとシリカの特性を併せ持つ粒子の製造方法が提案されている。例えば、炭酸カルシウムの形成工程である炭酸化反応工程において、炭酸カルシウムの結晶核生成後から炭酸化率が95%の間にコロイダルシリカまたは無水シリカを添加し、その後、炭酸化反応を終了させて、炭酸カルシウムの表面に平均粒子径が1ｎｍ〜100ｎｍの範囲にあるシリカ微粒子を付着し固定させ、炭酸カルシウム−シリカ複合粒子を製造する方法が記載されている(特許文献２参照)。 On the other hand, there has been proposed a method for producing particles having the characteristics of calcium carbonate and silica by adding synthetic silica at the time of calcium carbonate production (at the time of carbonation reaction) and combining synthetic silica and calcium carbonate. For example, in a carbonation reaction step, which is a calcium carbonate formation step, colloidal silica or anhydrous silica is added while the carbonation rate is 95% after the formation of crystal nuclei of calcium carbonate, and then the carbonation reaction is terminated. In addition, a method for producing calcium carbonate-silica composite particles by attaching and fixing silica fine particles having an average particle diameter in the range of 1 nm to 100 nm on the surface of calcium carbonate is described (see Patent Document 2).
また、アラゴナイト質柱状炭酸カルシウムの生成過程である炭酸化反応過程に、一次粒子の平均径が1〜100ｎｍの範囲にある合成シリカ(コロイダルシリカ、シリカゲル、無水シリカ、ホワイトカーボンなど)を共存させることにより、合成シリカ微粒子を長径0.5〜50μｍ、短径0.05〜5μｍ、アスペクト比5〜25の範囲にあるアラゴナイト質柱状炭酸カルシウムの表面に、直接、担持固定させ、炭酸カルシウム−シリカ複合粒子を製造する方法が記載されている(特許文献３参照)。 Synthetic silica (colloidal silica, silica gel, anhydrous silica, white carbon, etc.) with an average primary particle size in the range of 1 to 100 nm coexists in the carbonation reaction process, which is the process of producing aragonite columnar calcium carbonate. To produce a calcium carbonate-silica composite particle by directly supporting and fixing synthetic silica fine particles on the surface of aragonite columnar calcium carbonate having a major axis of 0.5-50 μm, a minor axis of 0.05-5 μm and an aspect ratio of 5-25. A method is described (see Patent Document 3).
これらの方法はいずれも、合成済みのシリカを炭酸カルシウム製造工程で混合し、炭酸ガスを吹き込み、炭酸カルシウムを析出させ、炭酸カルシウム−シリカ複合粒子を製造する方法となっている。従って、合成済みの軽質炭酸カルシウムのスラリーにケイ酸アルカリ溶液を添加し、この混合スラリーに鉱酸を添加し、最終pHが7〜9まで中和し、軽質炭酸カルシウム−シリカ複合粒子を得る本発明の製造方法とは異なる方法である。また、特許文献１、２で示されている方法で製造される複合物は、本発明の軽質炭酸カルシウム−シリカ複合物に比べ、吸油性が非常に低い。 In any of these methods, synthesized silica is mixed in a calcium carbonate production process, carbon dioxide is blown, calcium carbonate is precipitated, and calcium carbonate-silica composite particles are produced. Therefore, the alkali silicate solution is added to the synthesized light calcium carbonate slurry, the mineral acid is added to the mixed slurry, and the final pH is neutralized to 7 to 9, thereby obtaining light calcium carbonate-silica composite particles. This method is different from the manufacturing method of the invention. Moreover, the composite manufactured by the method shown by patent document 1, 2 is very low in oil absorption compared with the light calcium carbonate-silica composite of this invention.
また、シリカ粒子により被覆された炭酸カルシウムを填料として0.5〜5重量%含んでおり、さらに、炭酸カルシウム/シリカ粒子の重量比が2.5〜4.0(炭酸カルシウム：シリカ粒子＝71：29〜80：20)である中性紙が示されている(特許文献４参照)。一般に、シリカは軽質炭酸カルシウムよりも吸油量が高く、本発明の複合物においても軽質炭酸カルシウム比率が増加するに従って吸油量は低くなる傾向がある。従って、印刷後不透明度はむしろシリカの比率が高いほど有利に働く。このため、特許文献３記載の炭酸カルシウム−シリカ複合物では光学特性向上効果は期待できるが、本発明の軽質炭酸カルシウム−シリカ複合物(炭酸カルシウム：シリカ粒子＝30：70〜55：45)に比べ、吸油量向上は小さいと思われ、大幅な印刷後不透明度向上や裏抜け改善は期待できず、更に抄紙機カレンダーにおける処理により潰れやすく、紙を嵩高化する効果が劣る。従って、特許文献４記載の技術は、本発明とは一線を画す。 Further, it contains 0.5 to 5% by weight of calcium carbonate coated with silica particles as a filler, and the weight ratio of calcium carbonate / silica particles is 2.5 to 4.0 (calcium carbonate: silica particles = 71: 29 to 80:20). ) Is shown (see Patent Document 4). In general, silica has a higher oil absorption than light calcium carbonate, and even in the composite of the present invention, the oil absorption tends to decrease as the light calcium carbonate ratio increases. Therefore, the post-print opacity is more advantageous as the silica ratio is higher. For this reason, the calcium carbonate-silica composite described in Patent Document 3 can be expected to improve the optical properties, but the light calcium carbonate-silica composite of the present invention (calcium carbonate: silica particles = 30: 70 to 55:45) In comparison, the improvement in oil absorption is considered to be small, and a significant improvement in opacity after printing and anti-through-through improvement cannot be expected. Further, it is easily crushed by the processing in the paper machine calendar, and the effect of increasing the bulk of the paper is inferior. Therefore, the technique described in Patent Document 4 is different from the present invention.
また、ケイ酸アルカリ水溶液に耐アルカリ微小粒子(二酸化チタン、炭酸カルシウム、炭酸マグネシウム、硫酸バリウム、尿素ホルマリン、ポリスチレンなど)を添加して分散し、次いで液温を70〜95℃まで昇温し、液温を該温度範囲に保持しながら鉱酸を添加することにより液pHを3〜6.5の範囲に調整し、耐アルカリ微小粒子とシリカとの複合物を製造する方法が記載されている(特許文献５参照)。しかし、この方法において耐アルカリ微小粒子を炭酸カルシウムとした場合、ケイ酸アルカリ水溶液を混合後、鉱酸を添加し、液pHを3〜6.5の酸性とすると、炭酸カルシウムが分解し、複合物の収率が低下すると同時に、炭酸カルシウムの光学特性などが損なわれる問題がある。 In addition, alkali-resistant fine particles (titanium dioxide, calcium carbonate, magnesium carbonate, barium sulfate, urea formalin, polystyrene, etc.) are added to and dispersed in an alkali silicate aqueous solution, and then the liquid temperature is raised to 70 to 95 ° C. A method for producing a composite of alkali-resistant fine particles and silica by adjusting the liquid pH to a range of 3 to 6.5 by adding a mineral acid while maintaining the liquid temperature in the temperature range is described (patents). Reference 5). However, when the alkali-resistant microparticles are calcium carbonate in this method, after mixing the alkali silicate aqueous solution, adding mineral acid, and adjusting the pH of the solution to 3 to 6.5, the calcium carbonate decomposes and the composite There is a problem that the optical properties of calcium carbonate are impaired at the same time as the yield is lowered.
本発明は、填料や顔料として紙に使用される軽質炭酸カルシウム−シリカ複合物に関するものである。該軽質炭酸カルシウム−シリカ複合物は、軽質炭酸カルシウム由来の高い比散乱係数(高不透明性)という性状と、シリカ由来の高吸油量、嵩高という性状を併せ持つ複合物である。本発明の軽質炭酸カルシウム−シリカ複合物は、これらの性状に加えて、製紙工程中のカレンダー処理やスーパーカレンダー処理を受けても潰れ難いという性状を有する複合物である。 The present invention relates to a light calcium carbonate-silica composite used for paper as a filler or pigment. The light calcium carbonate-silica composite is a composite having both a property of high specific scattering coefficient (high opacity) derived from light calcium carbonate, a property of high oil absorption and bulkiness derived from silica. In addition to these properties, the light calcium carbonate-silica composite of the present invention is a composite that has the property that it is not easily crushed even when subjected to calendaring or supercalendering during the papermaking process.
本発明が解決しようとする課題は、軽質炭酸カルシウム由来の高い比散乱係数(高不透明性)という性状と、シリカ由来の高吸油量、嵩高という性状を併せ持ち、更に、製紙工程中のカレンダー処理やスーパーカレンダー処理を受けても潰れ難いという性状を有する、紙用の填料や顔料として使用できる軽質炭酸カルシウム−シリカ複合物の提供にある。 The problem to be solved by the present invention has both a property of high specific scattering coefficient (high opacity) derived from light calcium carbonate, a high oil absorption amount derived from silica, and a property of bulkiness. An object of the present invention is to provide a light calcium carbonate-silica composite that can be used as a filler or pigment for paper and has a property that it is not easily crushed even when subjected to a super calender treatment.
軽質炭酸カルシウムとアルカリ性のケイ酸金属塩水溶液を混合した液に、その煮沸温度以下の温度で、鉱酸を添加し液pHを7〜9として得られる、軽質炭酸カルシウム−シリカ複合物における、軽質炭酸カルシウムとケイ酸との重量比率を30:70〜55：45とする。 In a light calcium carbonate-silica composite obtained by adding mineral acid to a mixture of light calcium carbonate and alkaline metal silicate aqueous solution at a temperature equal to or lower than the boiling temperature to obtain a liquid pH of 7-9. The weight ratio of calcium carbonate and silicic acid is 30:70 to 55:45.
本発明の軽質炭酸カルシウム−シリカ複合物は、高白色度、高比散乱係数(高不透明性)、高吸油度、嵩高の性状を有する。更に、製紙工程中のカレンダー処理やスーパーカレンダー処理を受けても潰れ難いという性状を有し、軽質炭酸カルシウム−シリカ複合物を含有する紙はより嵩高(低密度)となる。 The light calcium carbonate-silica composite of the present invention has high whiteness, high specific scattering coefficient (high opacity), high oil absorption, and bulky properties. Further, the paper containing the light calcium carbonate-silica composite is more bulky (low density) because it is difficult to be crushed even when subjected to calendering or super calendering during the papermaking process.
本発明の紙用の軽質炭酸カルシウム−シリカ複合物の製造では、まず軽質炭酸カルシウムを水中に分散させる。この軽質炭酸カルシウムの結晶形態はカルサイト、アラゴナイトのいずれでも良く、また形状についても針状、柱状、紡錘状、球状、立方体状、ロゼッタ型のいずれでも良い。この中でも特にロゼッタ型のカルサイト系の軽質炭酸カルシウムを用いた場合に、特に優れた嵩高、不透明度改善効果が高い軽質炭酸カルシウム−シリカ複合物が得られる。なお、ロゼッタ型とは、紡錘状の軽質炭酸カルシウム一次粒子がいがくり状に凝集した形状を指し、他の軽質炭酸カルシウムより高い比表面積と吸油性を示す特徴がある(図１参照)。また、軽質炭酸カルシウムは粉砕処理を施して使用しても良い。 In the production of the light calcium carbonate-silica composite for paper of the present invention, first, the light calcium carbonate is dispersed in water. The crystal form of the light calcium carbonate may be either calcite or aragonite, and the shape may be any of acicular, columnar, spindle, spherical, cubic, and rosetta types. Among these, in particular, when a rosetta-type calcite-type light calcium carbonate is used, a light calcium carbonate-silica composite having a particularly high bulk and high opacity improvement effect can be obtained. The rosetta type refers to a shape in which spindle-shaped light calcium carbonate primary particles are aggregated in a corrugated shape, and is characterized by higher specific surface area and oil absorption than other light calcium carbonates (see FIG. 1). Light calcium carbonate may be used after being pulverized.
この軽質炭酸カルシウムの反応原液中濃度は、後述の軽質炭酸カルシウムとケイ酸の配合比率が重要であるため、ケイ酸濃度の影響も加味しなくてはならないが、1〜20固形分重量%が好ましい。1%未満の低濃度であると１バッチ当たりの生産量が少なく、生産性に問題がある。また、20%を超える高濃度とすると分散性が悪く、また軽質炭酸カルシウム量と比例して、反応に用いるケイ酸アルカリの濃度が高くなるため、反応時の粘度が上昇し、操業性に問題がある。 The concentration of the light calcium carbonate in the reaction stock solution is important for the ratio of light calcium carbonate and silicic acid, which will be described later, so the influence of the silicic acid concentration must be taken into account. preferable. When the concentration is less than 1%, the production amount per batch is small, and there is a problem in productivity. In addition, if the concentration exceeds 20%, dispersibility is poor, and the concentration of alkali silicate used in the reaction increases in proportion to the amount of light calcium carbonate. There is.
ついで、この軽質炭酸カルシウムのスラリーに、ナトリウム、カリウムのようなアルカリ溶液中に溶解した形のケイ酸を加える。一般的に工業用に用いられるものは、ケイ酸ソーダ(ナトリウム)もしくはケイ酸カリウムであるが、本発明である複合物を形成するためには、ケイ酸とアルカリのモル比はいずれでも良い。3号ケイ酸はSiO2：Na2O＝3〜3.4：1程度のモル比のものであるが、一般に入手しやすく、好適に使用される。軽質炭酸カルシウムとケイ酸アルカリとの仕込重量比は、生成する軽質炭酸カルシウム−シリカ複合物中の炭酸カルシウムとシリカの重量比が目標とする範囲に入るように仕込む。軽質炭酸カルシウム−シリカ複合物の炭酸カルシウムとシリカの重量比は、CaCO3/SiO2＝30/70〜55/45である。 Next, silicic acid dissolved in an alkaline solution such as sodium or potassium is added to the light calcium carbonate slurry. Generally used for industrial use is sodium silicate (sodium) or potassium silicate, but in order to form the composite according to the present invention, any molar ratio of silicic acid and alkali may be used. No. 3 silicic acid has a molar ratio of about SiO 2 : Na 2 O = 3 to 3.4: 1, but is generally easily available and is preferably used. The weight ratio of light calcium carbonate and alkali silicate is charged so that the weight ratio of calcium carbonate and silica in the resulting light calcium carbonate-silica composite falls within the target range. The weight ratio of calcium carbonate to silica in the light calcium carbonate-silica composite is CaCO3 / SiO2 = 30/70 to 55/45.
このスラリーをアジテータ、ホモミキサー、ミキサー等で攪拌、分散させるが、これは軽質炭酸カルシウムが水に十分に分散し、軽質炭酸カルシウムの粒子が極端に凝集してなければ問題なく、特に時間やアジテーションの強さ等の制限はない。 This slurry is stirred and dispersed with an agitator, homomixer, mixer, etc. This is fine as long as the light calcium carbonate is sufficiently dispersed in water and the light calcium carbonate particles are not extremely aggregated, especially time and agitation. There is no limit on the strength of the.
次に、酸を用いた中和反応を行う。この場合、酸は鉱酸ならいずれでも良く、さらには鉱酸中に硫酸バンドや硫酸マグネシウムのような酸性金属塩を含む酸でも使用できる。工業的には硫酸、塩酸等の比較的安価に購入できる酸が好ましい。高濃度の酸を用いた場合、酸による中和時の攪拌が不十分であると、高濃度の酸の添加により部分的にpHの低い部分ができ、軽質炭酸カルシウムが分解するため、酸添加口でホモミキサー等を用いた強攪拌を行う必要がある。一方、あまりに希薄な酸を用いると、酸添加により全体的な容量が極端に増えてしまうので好ましくない。この面からも、0.05N以上の濃度の酸を用いることが適当である。鉱酸または酸性金属塩水溶液の添加は、アルカリ性であるケイ酸金属塩水溶液と軽質炭酸カルシウムとの混合物の沸点以下の温度で行う。この中和処理によりケイ酸分を析出させ、非晶質ケイ酸を形成し、これが軽質炭酸カルシウム粒子の表面を被覆する。 Next, a neutralization reaction using an acid is performed. In this case, the acid may be any mineral acid, and further, an acid containing an acidic metal salt such as a sulfate band or magnesium sulfate in the mineral acid can be used. Industrially preferred are acids that can be purchased relatively inexpensively, such as sulfuric acid and hydrochloric acid. When a high concentration acid is used, if the stirring during neutralization with the acid is insufficient, the addition of the high concentration acid will result in a portion with a low pH, and light calcium carbonate will decompose, so acid addition It is necessary to perform strong stirring using a homomixer or the like at the mouth. On the other hand, if a too dilute acid is used, the overall capacity is extremely increased by the acid addition, which is not preferable. Also from this aspect, it is appropriate to use an acid having a concentration of 0.05 N or more. The mineral acid or acidic metal salt aqueous solution is added at a temperature not higher than the boiling point of the alkaline silicate metal salt aqueous solution and light calcium carbonate. By this neutralization treatment, silicic acid is deposited to form amorphous silicic acid, which covers the surface of the light calcium carbonate particles.
さらに、この酸添加は数回に分けて行っても良い。酸添加後、熟成を行っても良い。なお、熟成とは酸添加を一時中止し、攪拌のみを施し放置しておくことを指す。この熟成中中に強攪拌や粉砕を行い、粒子の形態をコントロールすることも可能である。 Furthermore, this acid addition may be performed in several times. Aging may be performed after the acid addition. The aging means that the acid addition is temporarily stopped, only stirred and left to stand. It is also possible to control the morphology of the particles by vigorous stirring and pulverization during this aging.
次に、上記酸添加によるスラリーの中和はpH＝7〜9を目標に行う。析出してきたケイ酸分により軽質炭酸カルシウムが被覆されていくが、酸性側(pH7未満)にすると、軽質炭酸カルシウムが分解してしまう。一方、pHが高い(9.0超)状態で中和を終了すると、ケイ酸分の析出が十分に行われず、スラリー中に未反応のケイ酸分が残り、ケイ酸分のロスが多くなり、工業的に好ましくない。そのため、目標pHは7〜9で中和を終了させる。 Next, neutralization of the slurry by the above acid addition is carried out with the target of pH = 7-9. The light calcium carbonate is coated with the precipitated silicic acid component, but when it is on the acidic side (less than pH 7), the light calcium carbonate is decomposed. On the other hand, when neutralization is completed at a high pH (above 9.0), silicic acid is not sufficiently precipitated, unreacted silicic acid remains in the slurry, and the loss of silicic acid increases. Is not preferable. Therefore, neutralization is completed at a target pH of 7-9.
このようにして、製造された軽質炭酸カルシウム−ケイ酸の複合物は、軽質炭酸カルシウム粒子表面をシリカが被覆した懸濁液の状態となる。この懸濁液のまま抄紙工程等に使用しても良いが、生産規模が小規模の場合にはろ紙やメンブランフィルタ等のろ過設備、中規模以上の場合にはベルトフィルタやドラムフィルタ等を用いたろ過、または遠心分離機を用いた遠心分離を行うことによって固液分離を行い、中和反応で生成した余分な副生成物である塩を極力取り除いたほうが好ましい。これは、余分な塩が残存していると、抄紙工程においてこの塩が難溶性の金属塩(例えば、硫酸カルシウム)に変化し、これを原因としたスケーリングの問題を発生するおそれがあるためである。さらにこの固液分離を行った固形分濃度10〜50%のケーキ状複合物を、水またはエタノールにより再分散後、再び固液分離を行い、さらに余分なケイ酸や副生成物である塩を取り除いても良い。 Thus, the manufactured light calcium carbonate-silicic acid composite is in a suspension state in which the surface of the light calcium carbonate particles is coated with silica. This suspension may be used in the papermaking process, but if the production scale is small, filter equipment such as filter paper or membrane filter is used, and if it is medium or larger, a belt filter or drum filter is used. It is preferable to carry out solid-liquid separation by performing filtration or centrifugal separation using a centrifuge, and to remove as much as possible the salt which is an extra by-product generated by the neutralization reaction. This is because if excess salt remains, this salt may change into a poorly soluble metal salt (e.g., calcium sulfate) in the papermaking process, which may cause scaling problems. is there. Furthermore, after re-dispersing the cake-like composite having a solid content concentration of 10 to 50%, which has been subjected to the solid-liquid separation, with water or ethanol, the solid-liquid separation is performed again to further remove excess silicic acid and by-product salts. It may be removed.
得られた軽質炭酸カルシウム−ケイ酸の複合物は、目的粒子径より大きい粗粒物を取り除くため、振動篩やスクリーンを用いて、100μｍ以上の粒子を除去する。 The obtained light calcium carbonate-silicic acid composite removes particles of 100 μm or more using a vibrating sieve or a screen in order to remove coarse particles larger than the target particle size.
本発明の軽質炭酸カルシウム−ケイ酸の複合物の平均粒子径の調整は、前述のように、熟成中に強攪拌や粉砕を行うことにより粒子の形態をコントロールすることも可能であるが、中和反応終了後または反応終了後の固液分離したものを、湿式粉砕機を用いて、目的の平均粒子径に調整しても良い。また、この組み合わせにより平均粒子径を調整しても良い。 As described above, the average particle size of the light calcium carbonate-silicic acid composite of the present invention can be controlled by vigorous stirring and pulverization during ripening. What was solid-liquid separated after completion of the summation reaction or after completion of the reaction may be adjusted to the target average particle size using a wet pulverizer. Further, the average particle diameter may be adjusted by this combination.
粗大粒子を除去した後、あるいは粗大粒子除去後さらに強撹拌や粉砕処理を施した軽質炭酸カルシウム−ケイ酸の複合物の平均粒子径は、その用途が紙用の填料である場合には、30μｍ以下が良く、20μｍ以下が好ましく、10μｍ以下が更に好ましい。 After removing the coarse particles, or after removing the coarse particles, the average particle size of the light calcium carbonate-silicic acid composite that has been further stirred and pulverized is 30 μm when the use is a filler for paper. The following is preferable, preferably 20 μm or less, and more preferably 10 μm or less.
以下、実施例にて本発明を具体的に説明するが、本発明はこれ等の実施例に限定されるものではない。なお、実施例及び比較例中の％、部は各々重量％、重量部を表す。本発明における軽質炭酸カルシウムーシリカ複合物の各特性値と、これを填料として配合した紙の紙質の測定方法を下記に示した。
（1)吸油量：JIS K5101の方法による。
（2）粒度分布測定：軽質炭酸カルシウム−ケイ酸の複合物のスラリーを分散剤ヘキサメタリン酸ソーダ0.2重量%を添加した純水中に滴下混合して均一分散体とし、レーザー法粒度測定機(使用機器：マルバーン社製マスターサイザーＳ型)を使用して粒度測定し、平均粒子径を求めた。
（3）紙の不透明度、嵩高率の測定：熊谷理機工業株式会社製の配向性抄紙機により、抄紙原料としてLBKPスラリーを用い、各実施例において得られた軽質炭酸カルシウム−ケイ酸の複合物のスラリーを填料として、その添加率を対パルプ5、10、15%として坪量60g/m2になるように抄造して、プレスにより脱水後、送風乾燥機にて乾燥し、各添加率のシートサンプルを作製した。このシートサンプルをJIS P8138に準じ、色差計(村上色彩研究所製)を用い、不透明度を測定した。また嵩高率は、このシートサンプルの紙厚を測定し、下記の式に従い算出した。各シートサンプルを525℃にて焼成し灰分量を測定し、紙中填料率と不透明度、紙中填料率と嵩高率の関係図を描いた。この図から、紙中填料率7%時の不透明度および嵩高率を求めた。また、前記シートサンプルを線圧を変えてカレンダー処理(処理温度65℃、2ニップ)し、紙中填料率7%時、かつ平滑度100sec.時の不透明度および嵩高率を求めた。
嵩高率＝(1−サンプル密度/填料無添加品の密度)×100
なお、填料無配合のシートの密度は、カレンダー未処理で0.572g/cm3、カレンダー処理した場合の平滑度100sec.時の密度は0.812g/cm3であった。
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the examples and comparative examples, “%” and “part” represent “% by weight” and “part by weight”, respectively. Each characteristic value of the light calcium carbonate-silica composite in the present invention and a method for measuring the paper quality of the paper blended with this as a filler are shown below.
(1) Oil absorption: According to JIS K5101 method.
(2) Particle size distribution measurement: Light calcium carbonate-silicic acid composite slurry is dropped and mixed in pure water to which 0.2% by weight of sodium hexametaphosphate is added to form a uniform dispersion. The particle size was measured using an apparatus: Mastersizer S type manufactured by Malvern, and the average particle size was determined.
(3) Measurement of paper opacity and bulkiness ratio: Light calcium carbonate-silicic acid composites obtained in each example using LBKP slurry as a papermaking raw material by an orientation paper machine manufactured by Kumagai Riki Kogyo Co., Ltd. Using the slurry of the product as a filler, making the addition rate to pulp 5, 10, 15% to a basis weight of 60 g / m 2 , dehydrating with a press and drying with a blow dryer, each addition rate A sheet sample was prepared. The opacity of this sheet sample was measured using a color difference meter (Murakami Color Research Laboratory) according to JIS P8138. The bulkiness ratio was calculated according to the following formula by measuring the paper thickness of the sheet sample. Each sheet sample was baked at 525 ° C., and the amount of ash was measured. The relationship between the filler content in paper and the opacity, the filler content in paper and the bulk ratio was drawn. From this figure, the opacity and bulkiness when the filler content in the paper was 7% were determined. Further, the sheet sample was calendered (treatment temperature 65 ° C., 2 nips) while changing the linear pressure, and the opacity and bulkiness ratio were obtained when the filler content in the paper was 7% and the smoothness was 100 sec.
Bulkiness factor = (1−sample density / density of filler-free product) × 100
The density of the unfilled sheet was 0.572 g / cm 3 when the calendar was not treated, and the density when the smoothness was 100 seconds when the calendar was treated was 0.812 g / cm 3 .
［実施例１］
反応容器(12L)中に市販ロゼッタ型軽質炭酸カルシウム(商品名:アルバカー5970、ＳＭＩ社製、平均粒子径2.4μｍ)603gを水に分散し、ここにSiO2濃度18.0wt/wt%、Na2O濃度6.1wt/wt%のケイ酸ソーダ溶液を3400g加えた後、水を加え、全量を12Lとした。この混合スラリーをラボ用アジテータで十分に攪拌しながら加熱し、85℃とした。このスラリーに、ロータリーポンプも用いて10%硫酸溶液をにより加えた。なお、この硫酸添加口付近が十分攪拌されるように、添加はホモミキサーの攪拌羽根直下とした。このように添加された硫酸が十分に分散される条件のもと、温度一定で、硫酸添加後の最終pHは8.0、全硫酸添加時間は240分間となるように、一定速度で硫酸を添加した。このスラリーは100メッシュ篩で粗粒分を分離した後、No.2のろ紙を用いて吸引ろ過し、さらに固形分濃度約10%に再分散し、平均粒子径、手抄き分析用サンプルとした。吸油量、ＢＥＴ比表面積用サンプルは吸引ろ過後のサンプルをエタノール中に約10%となるよう再分散した後、ろ過、105℃の乾燥機にて乾燥をおこない、粉体サンプルとした後に測定した。測定結果を表１に示す。
[Example 1]
In a reaction vessel (12 L), 603 g of commercially available Rosetta-type light calcium carbonate (trade name: Albuquer 5970, manufactured by SMI, average particle size 2.4 μm) was dispersed in water, where SiO 2 concentration was 18.0 wt / wt%, Na 2 After 3400 g of a sodium silicate solution having an O concentration of 6.1 wt / wt% was added, water was added to make the total volume 12 L. This mixed slurry was heated to 85 ° C. with sufficient stirring with a laboratory agitator. To this slurry was also added 10% sulfuric acid solution using a rotary pump. The addition was performed directly under the stirring blade of the homomixer so that the vicinity of the sulfuric acid addition port was sufficiently stirred. Under such conditions that the added sulfuric acid was sufficiently dispersed, sulfuric acid was added at a constant rate so that the temperature was constant, the final pH after addition of sulfuric acid was 8.0, and the total sulfuric acid addition time was 240 minutes. . This slurry is separated into coarse particles with a 100 mesh sieve, filtered with suction using No. 2 filter paper, and redispersed to a solid content concentration of about 10%. did. The sample for oil absorption and BET specific surface area was measured after re-dispersing the sample after suction filtration to about 10% in ethanol, followed by filtration and drying in a dryer at 105 ° C. to obtain a powder sample. . The measurement results are shown in Table 1.
[実施例２]
反応に使用する市販ロゼッタ型軽質炭酸カルシウムを、262gを用いた以外は、実施例１と同様に製造した。選られた複合物は物性を測定評価し、結果を表１に示した。
[Example 2]
A commercially available Rosetta-type light calcium carbonate used in the reaction was produced in the same manner as in Example 1 except that 262 g was used. The selected composite was measured and evaluated for physical properties, and the results are shown in Table 1.
[実施例３]
反応に使用する軽質炭酸カルシウムを、紡錘状軽カル(奥多摩工業製、ＴＰ１２１、平均粒子径1.2μｍ)とした以外は、実施例１と同様に製造した。選られた複合物は物性を測定評価し、結果を表１に示した。
[Example 3]
It was produced in the same manner as in Example 1 except that the light calcium carbonate used for the reaction was spindle-shaped light cal (TPO 121, average particle size 1.2 μm, manufactured by Okutama Kogyo). The selected composite was measured and evaluated for physical properties, and the results are shown in Table 1.
［実施例４］
市販ロゼッタ型軽質炭酸カルシウム(商品名:アルバカー5970、ＳＭＩ社製)を、平均粒径1.5μｍまでサンドグラインダーにて粉砕したものを、反応に使用した以外は、実施例１と同様に製造した。選られた複合物は物性を測定評価し、結果を表１に示した。
[Example 4]
A commercially available Rosetta-type light calcium carbonate (trade name: Albuquer 5970, manufactured by SMI Co., Ltd.) was produced in the same manner as in Example 1 except that a crushed powder with a sand grinder to an average particle size of 1.5 μm was used for the reaction. The selected composite was measured and evaluated for physical properties, and the results are shown in Table 1.
［比較例１］
実施例１に記載した市販ロゼッタ型軽質炭酸カルシウム(商品名:アルバカー5970、ＳＭＩ社製)を複合化せずそのまま用いた。この物性を測定評価し、結果を表１に示した。
[Comparative Example 1]
Commercially available rosetta-type light calcium carbonate (trade name: Albuquer 5970, manufactured by SMI) described in Example 1 was used as it was without being combined. The physical properties were measured and evaluated, and the results are shown in Table 1.
[比較例２]
反応に使用した市販ロゼッタ型軽質炭酸カルシウム(商品名:アルバカー5970、ＳＭＩ社製)を、150g用いた以外は、実施例１と同様に製造した。選られた複合物は物性を測定評価し、結果を表１に示した。
[Comparative Example 2]
This was produced in the same manner as in Example 1 except that 150 g of commercially available light rosette type calcium carbonate (trade name: Albuquer 5970, manufactured by SMI) used in the reaction was used. The selected composite was measured and evaluated for physical properties, and the results are shown in Table 1.
[比較例３]
反応に軽質炭酸カルシウムを用いなかった以外は、実施例１と同様に製造した。選られたシリカは物性を測定評価し、結果を表１に示した。
[Comparative Example 3]
Production was carried out in the same manner as in Example 1 except that light calcium carbonate was not used in the reaction. The selected silica was measured and evaluated for physical properties, and the results are shown in Table 1.
[比較例４]
市販ロゼッタ型軽質炭酸カルシウム(商品名:アルバカー5970、ＳＭＩ社製)と、市販の沈降法シリカであるローディアジャパン社Ｔｉｘｏｌｅｘ17(平均粒子径5.2μｍ)を、固形分重量比で50：50混合して用いた。この物性を測定評価し、結果を表１に示した。
[Comparative Example 4]
Commercially available Rosetta-type light calcium carbonate (trade name: Albuquer 5970, manufactured by SMI) and Rhodia Japan's Tixolex 17 (average particle size 5.2 μm), which is a commercially available precipitated silica, are mixed at a weight ratio of 50:50. Using. The physical properties were measured and evaluated, and the results are shown in Table 1.
実施例１〜４と比較例１、４との比較から、軽質炭酸カルシウム−シリカ複合物の吸油量は、軽質炭酸カルシウムのみよりも高く、シリカのもよりも低くなることがわかる。また、実施例１、２と比較例１〜４から、軽質炭酸カルシウム−シリカ複合物中の炭酸カルシウム重量比率が高くなるほど、吸油量が低下することがわかる。このことから、本発明の軽質炭酸カルシウム−シリカ複合物は、原料である軽質炭酸カルシウムよりも吸油量を高めることができ、印刷時の裏移りや裏抜け改善の効果が期待できる。 From comparison between Examples 1 to 4 and Comparative Examples 1 and 4, it can be seen that the amount of oil absorption of the light calcium carbonate-silica composite is higher than that of light calcium carbonate alone and lower than that of silica. Further, Examples 1 and 2 and Comparative Examples 1 to 4 show that the oil absorption decreases as the weight ratio of calcium carbonate in the light calcium carbonate-silica composite increases. From this, the light calcium carbonate-silica composite of the present invention can increase the amount of oil absorption compared to the light calcium carbonate that is the raw material, and can be expected to have an effect of improving the set-off during printing and the show-through.
軽質炭酸カルシウム−シリカ複合物を填料として配合した紙の特徴は次の通りである。実施例１〜４の不透明度は、カレンダー未処理紙、カレンダー処理した平滑度100sec.の紙のいずれも比較例１と比較例３との間にあるが、むしろ核である軽質炭酸カルシウムの不透明度に近い値である。また、実施例１〜４の嵩高率は、カレンダー処理紙、カレンダー処理した平滑度100sec.の紙のいずれも比較例１、４よりも高いことから、シート形成後の密度が低く、カレンダー処理しても、その低密度化の特徴は維持されることがわかる。 The characteristic of the paper which mix | blended the light calcium carbonate-silica composite as a filler is as follows. The opacity of Examples 1 to 4 is between Comparative Example 1 and Comparative Example 3 for both uncalendered paper and calendered smooth paper of 100 sec. The value is close to transparency. Moreover, since the bulkiness rate of each of Examples 1 to 4 is higher than that of Comparative Examples 1 and 4 for both the calendered paper and the calendered smooth paper of 100 sec. However, it can be seen that the low density feature is maintained.
このように、本発明の軽質炭酸カルシウム−シリカ複合物は吸油度に優れ、この複合物を填料として配合した紙は、不透明度が高く、顕著に嵩高になることがわかる。軽質炭酸カルシウム−シリカ複合物を顔料として含有する塗工紙においても同様な効果が期待できる。 Thus, it can be seen that the light calcium carbonate-silica composite of the present invention is excellent in oil absorption, and the paper blended with this composite as a filler has high opacity and is significantly bulky. A similar effect can be expected for coated paper containing a light calcium carbonate-silica composite as a pigment.
Claims (3)
An average particle size of the light calcium carbonate-silica composite for paper according to claim 1 or 2, wherein the average particle size is 1 to 30 µm.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007154333A (en) * | 2005-12-01 | 2007-06-21 | Nippon Paper Industries Co Ltd | Method for producing coated paper for printing use |
| JP2007217267A (en) * | 2006-01-19 | 2007-08-30 | Oji Paper Co Ltd | Porous filler, its production method, porous filler slurry and paper |
| JP2008156773A (en) * | 2006-12-22 | 2008-07-10 | Daio Paper Corp | Coated paperboard and method for producing the same |
| WO2008123493A1 (en) | 2007-03-30 | 2008-10-16 | Nippon Paper Industries Co., Ltd. | Process for producing coated-paper base and for producing coated paper |
| JP2012122159A (en) * | 2010-12-07 | 2012-06-28 | Daio Paper Corp | Composite particle, composite particle-internally added paper, and coated paper |
| US8241462B2 (en) | 2007-07-26 | 2012-08-14 | Harima Chemicals, Inc. | Papermaking internal sizing agent and use thereof |
| EP3498782B1 (en) | 2017-12-12 | 2020-09-16 | Imertech Sas | Preparation of silica-coated calcium carbonates with increased surface area and mesoporosity and silica hollow shells obtained from them |
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2004
- 2004-02-04 JP JP2004027483A patent/JP4225929B2/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007154333A (en) * | 2005-12-01 | 2007-06-21 | Nippon Paper Industries Co Ltd | Method for producing coated paper for printing use |
| JP2007217267A (en) * | 2006-01-19 | 2007-08-30 | Oji Paper Co Ltd | Porous filler, its production method, porous filler slurry and paper |
| JP2008156773A (en) * | 2006-12-22 | 2008-07-10 | Daio Paper Corp | Coated paperboard and method for producing the same |
| WO2008123493A1 (en) | 2007-03-30 | 2008-10-16 | Nippon Paper Industries Co., Ltd. | Process for producing coated-paper base and for producing coated paper |
| US8101046B2 (en) | 2007-03-30 | 2012-01-24 | Nippon Paper Industries, Co. Ltd. | Methods for producing coating base papers and coated papers |
| US8241462B2 (en) | 2007-07-26 | 2012-08-14 | Harima Chemicals, Inc. | Papermaking internal sizing agent and use thereof |
| JP2012122159A (en) * | 2010-12-07 | 2012-06-28 | Daio Paper Corp | Composite particle, composite particle-internally added paper, and coated paper |
| EP3498782B1 (en) | 2017-12-12 | 2020-09-16 | Imertech Sas | Preparation of silica-coated calcium carbonates with increased surface area and mesoporosity and silica hollow shells obtained from them |
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| JP4225929B2 (en) | 2009-02-18 |
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