JP2009203317A - Polyacrylonitrile-based polymer particle, and method for producing same - Google Patents
Polyacrylonitrile-based polymer particle, and method for producing same Download PDFInfo
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本発明は、例えばアクリル系繊維の原料に好適なポリアクリロニトリル系ポリマー粒子およびその製造方法に関する。 The present invention relates to polyacrylonitrile-based polymer particles suitable for a raw material for acrylic fibers, for example, and a method for producing the same.
アクリル系繊維の原料となるポリアクリロニトリル系ポリマー粒子（以下、「ポリマー粒子」という。）は、水系析出重合または溶液重合によって製造されるのが一般的である。特に水系析出重合は、溶液重合に比べて短い反応時間（重合反応器内の滞在時間）で連続生産が可能で、しかも簡便な重合反応容器を使用するため、生産性に非常に優れる。水系析出重合によって製造されるポリマー粒子の溶剤への溶解性は、これを原料として製造されるアクリル系繊維などの製品の性能だけでなく、製造工程の安定性に対しても大きな影響を与えることが多い。特に、アクリルニトリル単位を９５質量％以上含むポリマー粒子は、紡糸してアクリル系繊維を製造する際に用いる紡糸溶剤への分散条件や溶解条件が厳しいのが一般的である。 In general, polyacrylonitrile polymer particles (hereinafter referred to as “polymer particles”) as a raw material for acrylic fibers are produced by aqueous precipitation polymerization or solution polymerization. In particular, aqueous precipitation polymerization can be continuously produced in a shorter reaction time (residence time in the polymerization reactor) than solution polymerization, and uses a simple polymerization reaction vessel, so that it is extremely excellent in productivity. The solubility of polymer particles produced by water-based precipitation polymerization in a solvent has a significant impact not only on the performance of products such as acrylic fibers produced from this, but also on the stability of the production process. There are many. In particular, polymer particles containing 95% by mass or more of acrylonitrile units generally have severe conditions for dispersion and dissolution in a spinning solvent used when spinning to produce an acrylic fiber.
そこで、紡糸溶剤等の溶剤に対する分散性や溶解性を向上させるために、ポリマー粒子の形状を改善する試みがなされている。
例えば特許文献１には、粉末粒子１個当りの重量が５×１０−５ｍｇ以下である超高分子量重合体微粉末が開示されている。特許文献１によれば、ポリマー粒子１個当りの質量を小さくすることで、溶剤への分散性や溶解性を良好なものとしている。
また、特許文献２には、嵩密度が０．５５ｇ／ｃｍ３以上のアクリロニトリル系重合体が開示されている。特許文献２によれば、ポリマー粒子の嵩密度を高くすることで、溶解性の向上を図っている。
Therefore, attempts have been made to improve the shape of the polymer particles in order to improve dispersibility and solubility in solvents such as spinning solvents.
For example, Patent Document 1 discloses an ultrahigh molecular weight polymer fine powder having a weight per powder particle of 5 × 10 −5 mg or less. According to Patent Document 1, the dispersibility and solubility in a solvent are improved by reducing the mass per polymer particle.
Patent Document 2 discloses an acrylonitrile-based polymer having a bulk density of 0.55 g / cm 3 or more. According to Patent Document 2, the solubility is improved by increasing the bulk density of the polymer particles.
さらに、特許文献３には、粒子直径が２０〜８０ミクロン、空孔率が２０％以上、この内独立気泡が１０％以下のアクリロニトリル系ポリマー粉体が開示されている。特許文献３によれば、粒子直径や空孔率などを制御することで、溶解性を向上させている。
また、特許文献４には、重合体粉体嵩比重が０．３０ｇ／ｃｍ３以下、細孔分布平均が２００ｎｍ以上、Ｘ線回折測定による結晶化指数が０．７８以上のポリアクリロニトリル系重合体粒子が開示されている。特許文献４によれば、嵩比重や細孔分布平均、結晶化指数などを制御することで、分散性や溶解性を向上させている。
Patent Document 4 discloses a polyacrylonitrile polymer having a polymer powder bulk specific gravity of 0.30 g / cm 3 or less, an average pore distribution of 200 nm or more, and a crystallization index of 0.78 or more by X-ray diffraction measurement. Particles are disclosed. According to Patent Document 4, dispersibility and solubility are improved by controlling bulk specific gravity, pore distribution average, crystallization index, and the like.
しかしながら、特許文献１〜４に記載のように、ポリマー粒子の質量、嵩密度、粒子直径、嵩比重などを制御する方法では、分散性や溶解性を向上させることは必ずしも十分ではなかった。 However, as described in Patent Documents 1 to 4, it is not always sufficient to improve the dispersibility and solubility in the method of controlling the mass, bulk density, particle diameter, bulk specific gravity and the like of the polymer particles.
本発明は、上記事情を鑑みてなされたもので、分散性および溶解性に優れたポリアクリロニトリル系ポリマー粒子およびその製造方法の実現を目的とする。 This invention is made | formed in view of the said situation, and it aims at realization of the polyacrylonitrile-type polymer particle excellent in the dispersibility and solubility, and its manufacturing method.
本発明者等は鋭意検討した結果、ポリマー粒子を溶剤に分散した際の均一性が、後に溶液の均一性を支配すること、そしてポリマー粒子の分散性は、該ポリマー粒子の嵩密度を規定することで向上できることを見出した。さらに、ポリマー粒子の粒子構造を制御することが分散性および溶解性の向上に影響を与えることを見出し、本発明を完成するに至った。 As a result of intensive studies, the present inventors have determined that the uniformity when polymer particles are dispersed in a solvent later dominates the uniformity of the solution, and the dispersibility of the polymer particles defines the bulk density of the polymer particles. I found out that it can be improved. Furthermore, it has been found that controlling the particle structure of the polymer particles affects the improvement of dispersibility and solubility, and the present invention has been completed.
すなわち、本発明のポリアクリロニトリル系ポリマー粒子は、アクリロニトリル単位を９５質量％以上、アクリルアミド単位を０．５質量％以上含む単量体組成物を重合して得られ、嵩密度が０．２５〜０．４０ｇ／ｃｍ３であり、空孔率が２０％未満である中心部と、該中心部を取り囲み、かつ空孔率が２０％以上である外周部とから構成されたことを特徴とする。
ここで、前記外周部の平均厚さが１０μｍ以下であることが好ましい。
That is, the polyacrylonitrile-based polymer particles of the present invention are obtained by polymerizing a monomer composition containing 95% by mass or more of acrylonitrile units and 0.5% by mass or more of acrylamide units, and have a bulk density of 0.25 to 0. .40 g / cm 3 and having a porosity of less than 20% and an outer peripheral portion surrounding the center and having a porosity of 20% or more.
Here, the average thickness of the outer peripheral portion is preferably 10 μm or less.
また、本発明のポリアクリロニトリル系ポリマー粒子の製造方法は、還元剤および酸化剤を用い、アクリロニトリル単位を９５質量％以上、アクリルアミド単位を０．５質量％以上含む単量体組成物をレドックス水系懸濁重合するポリアクリロニトリル系ポリマー粒子の製造方法において、水と前記単量体組成物との質量比（水／単量体組成物）が２．５〜４．０、前記還元剤と前記酸化剤との質量比（還元剤／酸化剤）が１．０〜２．５であることを特徴とする。 The method for producing polyacrylonitrile-based polymer particles of the present invention uses a reducing agent and an oxidizing agent, and a monomer composition containing 95% by mass or more of acrylonitrile units and 0.5% by mass or more of acrylamide units is a redox aqueous suspension. In the method for producing polyacrylonitrile-based polymer particles that undergo turbid polymerization, the mass ratio of water to the monomer composition (water / monomer composition) is 2.5 to 4.0, the reducing agent and the oxidizing agent. The mass ratio (reducing agent / oxidizing agent) is 1.0 to 2.5.
本発明のポリアクリロニトリル系ポリマー粒子は、分散性および溶解性に優れる。
また、本発明のポリアクリロニトリル系ポリマー粒子の製造方法によれば、分散性および溶解性に優れたポリアクリロニトリル系ポリマー粒子が得られる。
The polyacrylonitrile-based polymer particles of the present invention are excellent in dispersibility and solubility.
Moreover, according to the method for producing polyacrylonitrile-based polymer particles of the present invention, polyacrylonitrile-based polymer particles excellent in dispersibility and solubility can be obtained.
以下本発明を詳細に説明する。
本発明のポリアクリロニトリル系ポリマー粒子（以下、「ポリマー粒子」という。）は、アクリロニトリル単位およびアクリルアミド単位を含む単量体組成物を重合して得られる。
アクリロニトリル単位の含有量は、単量体組成物１００質量％中、９５質量％以上であり、９５〜９９質量％が好ましい。アクリロニトリル単位を９５質量％以上含有することで、例えばポリマー粒子を紡糸した繊維を焼成して炭素繊維を製造する場合に、前駆体繊維に対する炭素繊維の収率が高くなるので、生産性の点で好ましい。
The present invention will be described in detail below.
The polyacrylonitrile-based polymer particles (hereinafter referred to as “polymer particles”) of the present invention are obtained by polymerizing a monomer composition containing acrylonitrile units and acrylamide units.
Content of an acrylonitrile unit is 95 mass% or more in 100 mass% of monomer compositions, and 95-99 mass% is preferable. By containing 95% by mass or more of acrylonitrile units, for example, in the case of producing carbon fibers by firing fibers obtained by spinning polymer particles, the yield of carbon fibers with respect to the precursor fibers is increased. preferable.
一方、アクリルアミド単位は、ポリマー粒子を紡糸する際の凝固過程において、凝固を緩慢にさせることができる。その結果、緻密な繊維構造が形成されやすくなるので、例えば炭素繊維などの前駆体繊維を製造する場合に好適である。アクリルアミド単位の含有量は、単量体組成物１００質量％中、０．５質量％以上であり、１．０〜４．０質量％が好ましい。アクリルアミド単位を０．５質量％以上含有すれば、凝固過程における凝固を十分に緩慢できる。 On the other hand, acrylamide units can slow the coagulation during the coagulation process when spinning polymer particles. As a result, a dense fiber structure is easily formed, which is suitable for producing precursor fibers such as carbon fibers. The content of acrylamide units is 0.5% by mass or more, preferably 1.0 to 4.0% by mass, in 100% by mass of the monomer composition. If the acrylamide unit is contained in an amount of 0.5% by mass or more, solidification in the solidification process can be sufficiently slowed down.
また、本発明においては、単量体組成物中に他のビニル単量体を含有させてもよい。他のビニル単量体としては、前記アクリロニトリル単位と共重合可能なものであれば特に制限されないが、例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、プロピル（メタ）アクリレート、ブチル（メタ）アクリレート、ヘキシル（メタ）アクリレート等の（メタ）アクリル酸エステル類；塩化ビニル、臭化ビニル、塩化ビニリデン等のハロゲン化ビニル類；（メタ）アクリル酸、イタコン酸、クロトン酸等の酸類及びそれらの塩類；マレイン酸イミド、フェニルマレイミド、（メタ）アクリルアミド、スチレン、α−メチルスチレン、酢酸ビニル、（メタ）アリルスルホン酸ナトリウム、（メタ）アリルオキシベンゼンスルホン酸ナトリウム、スチレンスルホン酸ナトリウム、２−アクリルアミド−２−メチルプロパンスルホン酸及びそれらの塩類などが挙げられる。 In the present invention, another vinyl monomer may be contained in the monomer composition. The other vinyl monomer is not particularly limited as long as it is copolymerizable with the acrylonitrile unit. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) (Meth) acrylic acid esters such as acrylate and hexyl (meth) acrylate; vinyl halides such as vinyl chloride, vinyl bromide and vinylidene chloride; acids such as (meth) acrylic acid, itaconic acid and crotonic acid and their Salts: maleic imide, phenylmaleimide, (meth) acrylamide, styrene, α-methylstyrene, vinyl acetate, sodium (meth) allylsulfonate, sodium (meth) allyloxybenzenesulfonate, sodium styrenesulfonate, 2-acrylamide -2-Methylpropa Sulfonic acids and their salts.
他のビニル単量体の含有量は、単量体組成物１００質量％中、０〜４．５質量％が好ましく、０．５〜４．０質量％がより好ましい。他のビニル単量体の含有量が４．５質量％以下であれば、例えば炭素繊維を製造するための前駆体繊維に用いた場合に、炭素繊維の収率を向上できる他、炭化反応速度を好適に制御できるようになる。 The content of the other vinyl monomer is preferably 0 to 4.5% by mass and more preferably 0.5 to 4.0% by mass in 100% by mass of the monomer composition. If the content of other vinyl monomers is 4.5% by mass or less, for example, when used as a precursor fiber for producing carbon fiber, the yield of carbon fiber can be improved, and the carbonization reaction rate Can be suitably controlled.
ポリマー粒子の分散性および溶解性を向上させるには、嵩密度、粒子径、粒子構造などのポリマー粒子の特性を制御することが重要となる。特に、粒子構造を制御することで、分散性および溶解性により優れたポリマー粒子が得られる。 In order to improve the dispersibility and solubility of the polymer particles, it is important to control the properties of the polymer particles such as bulk density, particle diameter, and particle structure. In particular, by controlling the particle structure, polymer particles having superior dispersibility and solubility can be obtained.
本発明のポリマー粒子は、嵩密度が０．２５〜０．４０ｇ／ｃｍ３である。ポリマー粒子は、嵩密度が小さくなるに連れて空隙の割合が多い疎な構造になりやすく、嵩密度が大きくなるに連れて空隙の割合が少ない密な構造になりやすい。
また、嵩密度が小さくなるほどポリマー粒子は疎な構造となるため、溶剤がポリマー粒子の内部に浸透しやすくなり、ポリマー粒子の一つ一つが溶解しやすい傾向にある。しかし、このような疎な構造のポリマー粒子では、ポリマー粒子を溶剤に分散させた直後から溶解し始めるので、分散液の濃度が上昇してポリマー粒子が不均一に分散した分散液となりやすく、結果、濃度ムラが生じやすくなる。さらに、部分的に溶解途中のポリマー粒子が凝集した、いわゆるママコができやすくなる。ママコは、分散液が昇温などにより溶解されてポリマー粒子が溶解した溶液となっても、未溶解の状態で溶液中に存在しやすい。そのため、溶液をろ過する際にママコ（未溶解物）がろ過されずにフィルターに捕捉され、フィルターが目詰まりしやすくなる。
The polymer particles of the present invention have a bulk density of 0.25 to 0.40 g / cm 3 . The polymer particles tend to have a sparse structure with a large proportion of voids as the bulk density decreases, and a dense structure with a small proportion of voids as the bulk density increases.
Further, since the polymer particles have a sparse structure as the bulk density decreases, the solvent tends to penetrate into the polymer particles, and each of the polymer particles tends to be easily dissolved. However, since the polymer particles having such a sparse structure start to dissolve immediately after the polymer particles are dispersed in the solvent, the concentration of the dispersion is increased, and the dispersion tends to be a dispersion in which the polymer particles are unevenly dispersed. Density unevenness tends to occur. Furthermore, it becomes easy to form so-called Mako, in which polymer particles partially dissolved are aggregated. Mamako tends to exist in the solution in an undissolved state even if the dispersion is dissolved by heating or the like to form a solution in which the polymer particles are dissolved. Therefore, when the solution is filtered, Mamako (undissolved matter) is captured by the filter without being filtered, and the filter is easily clogged.
嵩密度が０．２５ｇ／ｃｍ３以上であれば、ポリマー粒子が過度に疎な構造となるのを防げるので、ポリマー粒子の内部に浸透する溶剤の浸透速度が制御され、ポリマー粒子の一つ一つの溶解性を適度に抑制できる。そのため、ポリマー粒子を溶剤に分散させた直後は溶解しにくくなり、分散液の粘度の上昇を抑制して均一な分散液となりやすく、結果、濃度ムラが生じにくくなる。また、ママコもできにくくなる。従って、均一な状態の分散液を溶解すると、ポリマー粒子が均一に溶解した溶液が得られ、該溶液をろ過してもフィルターが目詰まりしにくい。 If the bulk density is 0.25 g / cm 3 or more, the polymer particles can be prevented from having an excessively sparse structure. Therefore, the permeation rate of the solvent that permeates the inside of the polymer particles is controlled, and each of the polymer particles is controlled. One solubility can be moderately suppressed. For this reason, the polymer particles are hardly dissolved immediately after being dispersed in the solvent, and an increase in the viscosity of the dispersion is suppressed to easily form a uniform dispersion. As a result, density unevenness is less likely to occur. In addition, it becomes difficult to make Mamako. Therefore, when the dispersion in a uniform state is dissolved, a solution in which the polymer particles are uniformly dissolved is obtained, and the filter is not easily clogged even if the solution is filtered.
一方、嵩密度が大きくなるほどポリマー粒子は空隙の割合が少なくなり、密な構造となる。その結果、溶剤がポリマー粒子の内部に極端に浸透しにくくなり、ポリマー粒子が分散した分散液を溶解させても、ポリマー粒子が溶け残りやすくなる。全てのポリマー粒子を溶解させるには、溶解時間を長くすればよいが、生産性が低下しやすくなる。
嵩密度が０．４０ｇ／ｃｍ３以下であれば、ポリマー粒子が過度に密な構造となるのを防げるので、ポリマー粒子が分散した分散液を容易に溶解できる。
従って、ポリマー粒子の分散性と溶解性のバランスを良好にするには、嵩密度を上記範囲内とすればよいが、好ましい嵩密度は０．２５〜０．３５ｇ／ｃｍ３である。
On the other hand, the larger the bulk density, the smaller the proportion of voids in the polymer particles, and the denser the structure. As a result, the solvent becomes extremely difficult to penetrate into the interior of the polymer particles, and the polymer particles are likely to remain undissolved even if the dispersion in which the polymer particles are dispersed is dissolved. In order to dissolve all the polymer particles, the dissolution time may be increased, but the productivity tends to decrease.
If the bulk density is 0.40 g / cm 3 or less, the polymer particles can be prevented from having an excessively dense structure, so that the dispersion in which the polymer particles are dispersed can be easily dissolved.
Therefore, in order to achieve a good balance between the dispersibility and solubility of the polymer particles, the bulk density may be within the above range, but the preferred bulk density is 0.25 to 0.35 g / cm 3 .
なお、本発明において溶剤とは、ポリマー粒子を紡糸する際に用いる紡糸溶剤のことである。具体的には、ジメチルホルムアミド、ジメチルアセトアミド、ジメチルスルホキサイド、γ−ブチロラクトン、硝酸水溶液、チオ硫酸ナトリウム水溶液等が挙げられる。中でも、ポリマー粒子の溶解性が優れる観点、および紡糸時における凝固のしやすさの観点からジメチルアセトアミドが好ましい。 In the present invention, the solvent is a spinning solvent used when spinning polymer particles. Specific examples include dimethylformamide, dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, aqueous nitric acid, and aqueous sodium thiosulfate. Among these, dimethylacetamide is preferable from the viewpoint of excellent solubility of the polymer particles and ease of coagulation during spinning.
ポリマー粒子の嵩密度の測定は、以下のようにして測定する。
予め嵩密度測定用容器の容積（Ａ）と質量（Ｂ）を測定しておく。嵩密度測定用容器にポリマー粒子を溢れるまで入れ、嵩密度測定用容器と同じ形状で、かつ底に穴の開いた蓋を底が上になるように嵩密度測定用容器にかぶせる。蓋の穴を指で押さえ、嵩密度測定用容器を蓋と一緒に上下にゆっくり５回振る。その後、蓋を取り、ポリマー粒子の上面が容器の縁と同じ高さになるように棒で素早くすり切り、余分なポリマー粒子を除去する。ポリマー粒子の入った嵩密度測定用容器の質量（Ｃ）を測定し、下記式（１）により嵩密度を求める。上記操作を５回行い、その平均値をポリマー粒子の嵩密度（ｇ／ｃｍ３）とした。
ポリマー粒子の嵩密度（ρ）＝（Ｃ−Ｂ）／Ａ ・・・（１）
The bulk density of the polymer particles is measured as follows.
The volume (A) and mass (B) of the bulk density measuring container are measured in advance. Put the polymer particles in the bulk density measuring container until it overflows, and cover the bulk density measuring container with a lid having the same shape as the bulk density measuring container and having a hole in the bottom so that the bottom is up. Hold the lid hole with your finger and gently shake the bulk density measurement container up and down 5 times with the lid. The lid is then removed and the excess polymer particles are removed by quickly scraping with a stick so that the top surface of the polymer particles is flush with the edge of the container. The mass (C) of the container for measuring the bulk density containing the polymer particles is measured, and the bulk density is obtained by the following formula (1). The said operation was performed 5 times and the average value was made into the bulk density (g / cm < 3 >) of a polymer particle.
Bulk density of polymer particles (ρ) = (C−B) / A (1)
ポリマー粒子は、平均粒子径が２０〜４０μｍであることが好ましく、２５〜３５μｍであることがより好ましい。
平均粒子径が小さくなるほど、単位質量あたりの粒子数が増加し、その結果、表面積が大きくなりポリマー粒子が溶剤と接触する割合が増える。溶剤と接触する割合が増えると、必然的にポリマー粒子が溶解する割合も増えるので、ポリマー粒子を溶剤に分散させた直後から溶解しやすくなる。そのため、分散液の粘度が上昇してポリマー粒子が不均一に分散した分散液となりやすく、結果、濃度ムラが生じやすくなる。
平均粒子径が２０μｍ以上であれば、単位質量あたりの粒子数は適度な数となるので、ポリマー粒子が溶剤に接触する割合を制御できる。
The polymer particles preferably have an average particle diameter of 20 to 40 μm, and more preferably 25 to 35 μm.
As the average particle size decreases, the number of particles per unit mass increases. As a result, the surface area increases and the proportion of polymer particles in contact with the solvent increases. As the ratio of contact with the solvent increases, the ratio of the polymer particles inevitably increasing also increases, so that the polymer particles are easily dissolved immediately after being dispersed in the solvent. Therefore, the viscosity of the dispersion is increased, and the dispersion tends to be a dispersion in which polymer particles are dispersed non-uniformly. As a result, density unevenness is likely to occur.
If the average particle size is 20 μm or more, the number of particles per unit mass is an appropriate number, and the ratio of the polymer particles contacting the solvent can be controlled.
一方、平均粒子径が大きくなるほど、溶剤がポリマーの内部にまで浸透しにくくなる傾向にあるため、分散液を溶解する際にポリマー粒子が溶け残りやすくなる。
平均粒子径が４０μｍ以下であれば、溶剤がポリマー粒子の内部にまで浸透しやすくなるので、必要以上に溶解時間を長く設定しなくてもポリマー粒子が均一に溶解した溶液が得られやすくなる。
従って、ポリマー粒子の分散性と溶解性のバランスを良好にするには、平均粒子径を上記範囲内とするのが好ましい。
On the other hand, the larger the average particle size, the more difficult the solvent penetrates into the interior of the polymer, and therefore the polymer particles are more likely to remain undissolved when the dispersion is dissolved.
When the average particle diameter is 40 μm or less, the solvent easily penetrates into the polymer particles, and thus a solution in which the polymer particles are uniformly dissolved can be easily obtained without setting the dissolution time longer than necessary.
Therefore, in order to achieve a good balance between the dispersibility and solubility of the polymer particles, it is preferable that the average particle diameter is within the above range.
ポリマー粒子の平均粒子径は、以下のようにして測定する。
レーザー回折散乱法を原理とした粒度分布測定機を用い、ポリマー粒子の粒度分布を屈折率１．３３０−０．０１ｉ、形状係数１．０００にて測定し、体積平均から算出された５０％正規分布の値を平均粒子径（μｍ）とした。
粒度分布測定機としては、例えばセイシン企業社製のＳＫレーザーマイクロンサイザー「ＬＭＳ−３５０」などが挙げられる。
The average particle diameter of the polymer particles is measured as follows.
Using a particle size distribution measuring machine based on the principle of laser diffraction scattering method, the particle size distribution of the polymer particles is measured at a refractive index of 1.330-0.01i and a shape factor of 1.000, and 50% normal calculated from the volume average. The distribution value was defined as the average particle size (μm).
Examples of the particle size distribution measuring machine include SK Laser Micron Sizer “LMS-350” manufactured by Seishin Enterprise Co., Ltd.
本発明のポリマー粒子は、空孔率が２０％未満である中心部と、該中心部を取り囲み、かつ空孔率が２０％以上である外周部とから構成されている。空孔率が２０％未満の中心部は空隙の割合が少なく密な構造となっている。一方、空孔率が２０％以上の外周部は、空隙の割合が多い疎な構造となっている。
本発明のポリマー粒子が、密な中心部と疎な外周部とからなる二重構造であることにより、ポリマー粒子を溶剤に分散したときに粒子内部（中心部）への溶剤の浸透が抑制され、溶剤に分散させた直後は溶解せずにポリマー粒子が均一に分散した分散液が得られると共に、ママコができにくくなる。一方、ポリマー粒子は疎な外周部を有するので、分散液を溶解させる際は、溶剤が外周部に浸透して溶解しやすい。
このような二重構造であるポリマー粒子は、溶剤の浸透速度が適度に制御されるので、分散性と溶解性とのバランスが良好である。
The polymer particles of the present invention are composed of a central part having a porosity of less than 20% and an outer peripheral part surrounding the central part and having a porosity of 20% or more. The central portion having a porosity of less than 20% has a small void ratio and a dense structure. On the other hand, the outer peripheral portion having a porosity of 20% or more has a sparse structure with a large proportion of voids.
Since the polymer particles of the present invention have a double structure consisting of a dense central portion and a sparse outer peripheral portion, the penetration of the solvent into the particles (center portion) is suppressed when the polymer particles are dispersed in the solvent. Immediately after being dispersed in the solvent, a dispersion in which the polymer particles are uniformly dispersed without being dissolved is obtained, and it is difficult to produce mako. On the other hand, since the polymer particles have a sparse outer peripheral part, when the dispersion is dissolved, the solvent easily penetrates into the outer peripheral part and dissolves.
The polymer particles having such a double structure have a good balance between dispersibility and solubility because the penetration rate of the solvent is appropriately controlled.
前記外周部は、平均厚さが１０μｍ以下であることが好ましく、５〜１０μｍであることがより好ましい。平均厚さが１０μｍ以下であれば、ポリマー粒子全体に対する中心部の割合（大きさ）を十分に確保できるので、分散性および溶解性の向上効果がより得られやすくなる。 The outer peripheral portion preferably has an average thickness of 10 μm or less, more preferably 5 to 10 μm. If the average thickness is 10 μm or less, the ratio (size) of the central portion with respect to the entire polymer particles can be sufficiently secured, so that the effect of improving dispersibility and solubility can be more easily obtained.
ポリマー粒子の空孔率は、以下のようにして測定する。
ポリマー粒子を乾燥させて乾燥粉とし、該乾燥粉をＵＶ硬化型アクリル系樹脂で重合包埋した後、ダイヤモンドナイフを装着したミクロトームにより、０．５ｍｍ×０．５ｍｍの大きさで約７０ｎｍの厚さの切片を切り出し、ＴＥＭ観察用グリッド上に回収する（配置する）。
ついで、切片を載せたグリッドを酢酸イソアミルに浸して包埋樹脂（ＵＶ硬化型アクリル系樹脂）を溶解除去、乾燥して試験片とし、透過型電子顕微鏡により、加速電圧８０ｋＶ、観察倍率３，０００〜５，０００倍の条件で観察する。
空孔率の計測には日本ローパー社製の画像解析ソフト「Ｉｍａｇｅ−Ｐｒｏ Ｐｌｕｓ」を用い、画像上で２μｍ×２μｍの計測範囲を設定して、この範囲内にてポリマー粒子の半径線上で最表層から中心に向かって順次移動しながら、空孔が占める比率を計測して空孔率（％）を求める。このとき、ポリマー部分と空孔部分との区別は画像のコントラストに基づいて行うことができる。
１個のポリマー粒子について３方向から計測した平均値から、ポリマー粒子の表面からの距離と空孔率との関係を求める。また、１個の試験片について１０個以上のポリマー粒子を計測する。
なお、上述した測定方法では、必ずしもポリマー粒子の中心を通る断面が得られているとは限らないが、１個の試験片の中でみかけの粒径の大きいものを計測することとする。このようにして、空孔率が２０％以上の部分を外周部、２０％未満の部分を中心部とし、外周部の厚さを測定し、その平均値を求めた。
The porosity of the polymer particles is measured as follows.
The polymer particles are dried to obtain a dry powder, and the dry powder is polymer-embedded with a UV curable acrylic resin, and then a thickness of about 70 nm in a size of 0.5 mm × 0.5 mm by a microtome equipped with a diamond knife. The slice is cut out and collected (arranged) on the TEM observation grid.
Next, the grid on which the section was placed was immersed in isoamyl acetate to dissolve and remove the embedding resin (UV curable acrylic resin), dried to obtain a test piece, and an accelerating voltage of 80 kV and an observation magnification of 3,000 using a transmission electron microscope. Observe under 5,000 times condition.
For the measurement of porosity, the image analysis software “Image-Pro Plus” manufactured by Nippon Roper is used, and a measurement range of 2 μm × 2 μm is set on the image. While sequentially moving from the surface layer toward the center, the ratio of the voids is measured to obtain the porosity (%). At this time, the polymer part and the hole part can be distinguished based on the contrast of the image.
The relationship between the distance from the surface of the polymer particle and the porosity is determined from the average value measured from three directions for one polymer particle. Moreover, ten or more polymer particles are measured for one test piece.
In the measurement method described above, a cross-section passing through the center of the polymer particles is not always obtained, but a test piece having a large apparent particle size is measured. Thus, the thickness of the outer peripheral portion was measured with the portion having a porosity of 20% or more as the outer peripheral portion and the portion having a porosity of less than 20% as the central portion, and the average value was obtained.
ポリマー粒子の嵩密度、平均粒子径、および粒子構造は、ポリマー粒子を製造する際の製造条件を調整することで制御できる。
ここで、本発明のポリマー粒子の製造方法の一例について具体的に説明する。
The bulk density, average particle diameter, and particle structure of the polymer particles can be controlled by adjusting the production conditions when producing the polymer particles.
Here, an example of the manufacturing method of the polymer particle of this invention is demonstrated concretely.
ポリマー粒子は、上述した単量体組成物を水系懸濁法によるレドックス重合（レドックス水系懸濁重合）して製造される。レドックス水系懸濁重合には、レドックス触媒として還元剤と酸化剤を用いる。
具体的には、重合釜などに脱イオン交換水などの水と、アクリロニトリル単位およびアクリルアミド単位を含む単量体組成物とを投入し、さらに還元剤、酸化剤および重合開始剤を各々水に溶解させた各水溶液を重合釜に供給し、十分に攪拌を行ってポリマー水系分散液（重合スラリー）を調製する。また、重合反応の開始前に、重合釜内の重合反応液のｐＨが２．５〜３．５になるように、ｐＨ調製剤を添加するのが好ましい。重合の際の反応温度は３０〜７０℃が好ましく、４０〜６０℃がより好ましい。また、反応時間（重合釜内の滞在時間）は０．５〜１０時間が好ましく、生産速度の観点から１〜２時間がより好ましい。
The polymer particles are produced by redox polymerization (redox aqueous suspension polymerization) of the above-described monomer composition by an aqueous suspension method. In the redox aqueous suspension polymerization, a reducing agent and an oxidizing agent are used as a redox catalyst.
Specifically, water such as deionized exchange water and a monomer composition containing acrylonitrile units and acrylamide units are charged into a polymerization kettle and the like, and a reducing agent, an oxidizing agent, and a polymerization initiator are dissolved in water. Each of the aqueous solutions is supplied to a polymerization kettle and sufficiently stirred to prepare a polymer aqueous dispersion (polymerization slurry). Moreover, it is preferable to add a pH adjusting agent so that the pH of the polymerization reaction solution in the polymerization vessel becomes 2.5 to 3.5 before the start of the polymerization reaction. 30-70 degreeC is preferable and the reaction temperature in the case of superposition | polymerization has more preferable 40-60 degreeC. Further, the reaction time (the residence time in the polymerization kettle) is preferably 0.5 to 10 hours, and more preferably 1 to 2 hours from the viewpoint of production rate.
重合釜から重合スラリーを取り出した後、該重合スラリーに、重合停止剤を水に溶解させた重合停止剤水溶液をｐＨが５．５〜６．０になるように添加し、オリバー型連続フィルターなどを用いて脱水処理する。ついで、脱水処理物を加熱洗浄処理した後、乾燥させてポリマー粒子とする。加熱洗浄処理の方法としては、例えば水を脱水処理物に加えて、５０〜１００℃で５〜３０分間、ドラムフィルターなどを用いて連続洗浄する方法が挙げられる。
なお、乾燥工程でのポリマー粒子の取り扱いを容易にするために、乾燥前にペレット化してもよい。ただし、この場合は、乾燥後にハンマーミルなどの粉砕機にてペレットを粉砕してポリマー粒子とする。
After the polymerization slurry is taken out from the polymerization kettle, an aqueous solution of a polymerization terminator in which a polymerization terminator is dissolved in water is added to the polymerization slurry so that the pH becomes 5.5 to 6.0. To dehydrate. Next, the dehydrated product is heated and washed, and then dried to obtain polymer particles. As a method of the heat washing treatment, for example, a method of adding water to the dehydrated product and continuously washing it at 50 to 100 ° C. for 5 to 30 minutes using a drum filter or the like can be mentioned.
In order to facilitate handling of the polymer particles in the drying step, pelletization may be performed before drying. In this case, however, the pellets are pulverized with a pulverizer such as a hammer mill after drying to obtain polymer particles.
本発明者等は鋭意検討した結果、ポリマー粒子の分散性や溶解性の決め手となる粒子構造、すなわち上述したような中心部と外周部からなる二重構造のポリマー粒子は、重合体の成長速度と凝集構造の生成速度を制御することで容易に得られることを見出した。そして、重合体の成長速度と凝集構造の生成速度は、製造条件として重合反応に用いる媒体（水）と原料である単量体組成物の質量比と、レッドクス触媒である還元剤と酸化剤の質量比を調節することで制御できることを見出した。 As a result of intensive studies, the present inventors have determined that the particle structure that determines the dispersibility and solubility of the polymer particles, that is, the polymer particles having a double structure consisting of the central part and the outer peripheral part as described above, is a polymer growth rate. And it was found that it can be easily obtained by controlling the formation rate of aggregated structure. The growth rate of the polymer and the rate of formation of the aggregated structure are as follows: the mass ratio of the medium (water) used for the polymerization reaction and the monomer composition as the raw material as the production conditions, and the reducing agent and oxidizing agent as the Redox catalyst. It was found that it can be controlled by adjusting the mass ratio.
すなわち、本発明においては、水と単量体組成物の質量比Ｘ（水／単量体組成物）を２．５〜４．０に、還元剤と酸化剤との質量比Ｙ（還元剤／酸化剤）を１．０〜２．５に調節する。
質量比Ｘが２．５以上であれば、撹拌による重合熱の除去が安定に行え、ポリマー粒子の粒度分布や重合系の粘度などが一定になりやすく、安定な重合が行える。一方、質量比Ｘが４．０以下であれば、生成したポリマー粒子の一次粒子の凝集性が増すので、嵩密度が０．２５ｇ／ｃｍ３以上のポリマー粒子を形成しやすくなる。
また、質量比Ｙが１．０以上であれば、適度な重合転化率となるので、工業的に効率よくポリマー粒子を生産できる。一方、質量比Ｙが２．５以下であれば、生成したポリマー粒子の一次粒子の凝集性が増すので、嵩密度が０．２５ｇ／ｃｍ３以上のポリマー粒子を形成しやすくなる。
That is, in the present invention, the mass ratio X (water / monomer composition) of water to the monomer composition is set to 2.5 to 4.0, and the mass ratio Y of the reducing agent to the oxidizing agent (reducing agent). / Oxidizing agent) is adjusted to 1.0 to 2.5.
When the mass ratio X is 2.5 or more, the heat of polymerization can be stably removed by stirring, the particle size distribution of the polymer particles, the viscosity of the polymerization system and the like are easily constant, and stable polymerization can be performed. On the other hand, if the mass ratio X is 4.0 or less, the cohesiveness of the primary particles of the produced polymer particles is increased, so that it is easy to form polymer particles having a bulk density of 0.25 g / cm 3 or more.
In addition, when the mass ratio Y is 1.0 or more, an appropriate polymerization conversion rate is obtained, so that polymer particles can be produced industrially efficiently. On the other hand, if the mass ratio Y is 2.5 or less, the cohesiveness of the primary particles of the generated polymer particles is increased, so that polymer particles having a bulk density of 0.25 g / cm 3 or more can be easily formed.
このように質量比Ｘおよび質量比Ｙを調節することで、中央部と外周部からなる二重構造のポリマー粒子が容易に得られるようになる。得られたポリマー粒子は、分散性および溶解性に優れる。
また、質量比Ｘおよび質量比Ｙを調節することで、ポリマー粒子の嵩密度および粒子径をも調整できる。従って、質量比Ｘおよび質量比Ｙが前記範囲内であれば、嵩密度や平均粒子径を上述した範囲内に容易に調整できるので、分散性および溶解性に優れたポリマー粒子が得られる。
質量比Ｘおよび質量比Ｙの好ましい範囲としては、質量比Ｘが２．５〜３．５であり、質量比Ｙが１．０〜２．０である。
Thus, by adjusting the mass ratio X and the mass ratio Y, a double-structured polymer particle composed of a central portion and an outer peripheral portion can be easily obtained. The obtained polymer particles are excellent in dispersibility and solubility.
Further, by adjusting the mass ratio X and the mass ratio Y, the bulk density and particle diameter of the polymer particles can also be adjusted. Accordingly, when the mass ratio X and the mass ratio Y are within the above ranges, the bulk density and the average particle diameter can be easily adjusted within the above-described ranges, and thus polymer particles having excellent dispersibility and solubility can be obtained.
As a preferable range of the mass ratio X and the mass ratio Y, the mass ratio X is 2.5 to 3.5, and the mass ratio Y is 1.0 to 2.0.
還元剤および酸化剤としては、公知のレドックス触媒を用いることができる。例えば、還元剤としては、亜硫酸水素ナトリウム、亜硫酸水素アンモニウム、アルキルメルカプタン類などが挙げられ、中でも亜硫酸水素ナトリウム、亜硫酸水素アンモニウムが好ましい。一方、酸化剤としては、過硫酸カリウム、過硫酸ナトリウム、過硫酸アンモニウム、亜塩素酸ナトリウムが挙げられ、中でも過硫酸アンモニウムが好ましい。
還元剤の添加量は、単量体組成物１００質量部に対して０．０５〜２．０質量部が好ましく、０．１〜１．０質量部がより好ましい。
酸化剤の添加量は、単量体組成物１００質量部に対して０．０１〜１．０質量部が好ましく、０．０５〜０．５質量部がより好ましい。
As the reducing agent and oxidizing agent, known redox catalysts can be used. For example, examples of the reducing agent include sodium hydrogen sulfite, ammonium hydrogen sulfite, and alkyl mercaptans. Among them, sodium hydrogen sulfite and ammonium hydrogen sulfite are preferable. On the other hand, examples of the oxidizing agent include potassium persulfate, sodium persulfate, ammonium persulfate, and sodium chlorite. Among them, ammonium persulfate is preferable.
0.05-2.0 mass parts is preferable with respect to 100 mass parts of monomer compositions, and, as for the addition amount of a reducing agent, 0.1-1.0 mass part is more preferable.
The addition amount of the oxidizing agent is preferably 0.01 to 1.0 part by mass, more preferably 0.05 to 0.5 part by mass with respect to 100 parts by mass of the monomer composition.
このようにして得られるポリマー粒子は、粒子構造が上述した中心部と外周部からなる二重構造であり、嵩密度や粒子径といった特性が上述した範囲内であるため、溶剤中にポリマー粒子が均一に分散した状態でスラリー化でき、その後、昇温して分散液を溶解する過程で短時間に全てのポリマー粒子が溶解する。従って、本発明のポリマー粒子であれば、溶剤の溶解時間が５分以下になりやすく、全てのポリマー粒子を溶解させるために、必要以上に溶解温度を上げたり、溶解時間を長くしたりしなくても、短時間で溶剤に溶解でき、工業的に好適である。 The polymer particles thus obtained have a double structure in which the particle structure is composed of the center part and the outer peripheral part described above, and the properties such as the bulk density and the particle diameter are within the above-described ranges. It can be slurried in a uniformly dispersed state, and then all polymer particles dissolve in a short time in the process of raising the temperature and dissolving the dispersion. Therefore, with the polymer particles of the present invention, the solvent dissolution time tends to be 5 minutes or less, and in order to dissolve all the polymer particles, the dissolution temperature is not increased more than necessary or the dissolution time is not lengthened. However, it can be dissolved in a solvent in a short time, which is industrially suitable.
ポリマー粒子の溶解時間は、以下のようにして測定する。
−５℃に冷却したジメチルアセトアミド溶剤に、固形分が２１質量％になるように均一にポリマー粒子を分散させた分散液をスライドグラスに挟み、ＬＩＮＫＡＭ社製のホットステージにより１０℃／分で昇温しながら、位相差顕微鏡像によって２００倍の視野内のポリマー粒子の個数を計測する。溶解前（昇温前）のポリマー粒子の個数をｎ（０）個、昇温温度ｔ℃のときのポリマー粒子の個数をｎ（ｔ）個として、溶解進行率を下記式（２）より算出し、溶解開始から溶解終了（溶解進行率１００％）までに要する時間を溶解時間（分）とする。
溶解進行率（％）＝（１−ｎ（ｔ）／ｎ（０））×１００ ・・・（２）
The dissolution time of the polymer particles is measured as follows.
A dispersion in which polymer particles are uniformly dispersed in a dimethylacetamide solvent cooled to −5 ° C. so as to have a solid content of 21% by mass is sandwiched between slide glasses, and the temperature is increased at 10 ° C./min by a LINKAM hot stage. While warming, the number of polymer particles in a 200 × field of view is measured by a phase contrast microscope image. The number of polymer particles before dissolution (before temperature increase) is n (0), the number of polymer particles at temperature increase temperature t ° C. is n (t), and the rate of dissolution is calculated from the following formula (2). The time required from the start of dissolution to the end of dissolution (dissolution progress rate 100%) is defined as dissolution time (minutes).
Dissolution rate (%) = (1−n (t) / n (0)) × 100 (2)
ところで、通常、アクリロニトリル単位を９５質量％以上含有するポリマー粒子は、紡糸溶剤への分散条件や溶解条件が厳しい。
しかし、本発明のポリマー粒子であれば、嵩密度が特定の範囲内に制御され、かつ空孔率が２０％未満の中心部と、空孔率が２０％以上の外周部とからなる構成となっているので、ポリマー粒子に対する溶剤の浸透の度合いが適度なものとなる。従って、本発明によれば、分散性および溶解性に優れたポリマー粒子が得られるので、溶剤への分散条件や溶解条件の設定を緩和できる。
By the way, normally, polymer particles containing 95% by mass or more of acrylonitrile units are severely dispersed or dissolved in a spinning solvent.
However, with the polymer particles of the present invention, the bulk density is controlled within a specific range, and the center portion has a porosity of less than 20% and the outer peripheral portion has a porosity of 20% or more. Therefore, the degree of penetration of the solvent into the polymer particles is moderate. Therefore, according to the present invention, polymer particles having excellent dispersibility and solubility can be obtained, so that it is possible to relax the setting of dispersion conditions and dissolution conditions in a solvent.
また、本発明によれば、ポリマー粒子を溶剤に均一に分散させた後に、分散液を昇温して溶解させることができ、未溶解のポリマー粒子の割合が低減されやすい。そのため、溶液をろ過する際に、フィルターが目詰まりしにくくなるので、フィルターの交換頻度を軽減できると共に、紡糸した繊維の構造を均質化できる。 In addition, according to the present invention, after the polymer particles are uniformly dispersed in the solvent, the dispersion can be heated and dissolved, and the proportion of undissolved polymer particles can be easily reduced. Therefore, when the solution is filtered, the filter is less likely to be clogged, so that the frequency of replacement of the filter can be reduced and the structure of the spun fiber can be homogenized.
また、本発明のポリマー粒子は、紡糸する際に用いる紡糸溶剤への溶解性に優れることから、特にアクリル系繊維の原料として特に好適である。 The polymer particles of the present invention are particularly suitable as a raw material for acrylic fibers because they are excellent in solubility in a spinning solvent used for spinning.
以下、本発明を実施例により具体的に説明するが、本発明はこれらに限定されるものではない。
実施例における各測定方法については、下記の方法により実施した。
Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
About each measuring method in an Example, it implemented by the following method.
＜測定方法＞
（ポリマー粒子の組成比の分析）
ジメチルスルホキシド−ｄ６溶媒に、ポリマー粒子を５質量％溶解し、核磁気共鳴装置（日本電子社製、「ＥＸ−２７０型ＮＭＲ」）により、積算回数４０回、測定温度１２０℃で測定して、ケミカルシフトの積分比からポリマー粒子の共重合組成比を求めた。
なお、ポリマー粒子の共重合組成比は、単量体組成物中に含まれる各単量体単位の含有量とほぼ一致する。
<Measurement method>
(Analysis of composition ratio of polymer particles)
In a dimethyl sulfoxide-d6 solvent, 5% by mass of polymer particles were dissolved, and measured with a nuclear magnetic resonance apparatus (manufactured by JEOL Ltd., “EX-270 NMR”) at a measurement temperature of 120 ° C. 40 times. The copolymer composition ratio of the polymer particles was determined from the chemical shift integral ratio.
The copolymer composition ratio of the polymer particles substantially matches the content of each monomer unit contained in the monomer composition.
（ポリマー粒子の嵩密度の測定）
予め嵩密度測定用容器の容積（Ａ）と質量（Ｂ）を測定した。嵩密度測定用容器にポリマー粒子を溢れるまで入れ、嵩密度測定用容器と同じ形状で、かつ底に穴の開いた蓋を底が上になるように嵩密度測定用容器にかぶせた。蓋の穴を指で押さえ、嵩密度測定用容器を蓋と一緒に上下にゆっくり５回振った。その後、蓋を取り、ポリマー粒子の上面が容器の縁と同じ高さになるように棒で素早くすり切り、余分なポリマー粒子を除去した。ポリマー粒子の入った嵩密度測定用容器の質量（Ｃ）を測定し、下記式（１）により嵩密度を求めた。上記操作を５回行い、その平均値をポリマー粒子の嵩密度（ｇ／ｃｍ３）とした。
ポリマー粒子の嵩密度（ρ）＝（Ｃ−Ｂ）／Ａ ・・・（１）
(Measurement of bulk density of polymer particles)
The volume (A) and mass (B) of the bulk density measurement container were measured in advance. The polymer particles were put into a bulk density measuring container until it overflowed, and the bulk density measuring container was covered with a lid having the same shape as the bulk density measuring container and having a hole in the bottom so that the bottom was up. The hole in the lid was pressed with a finger, and the bulk density measurement container was slowly shaken up and down 5 times together with the lid. Thereafter, the lid was removed, and the polymer particles were quickly ground with a stick so that the top surface of the polymer particles was flush with the edge of the container, and the excess polymer particles were removed. The mass (C) of the bulk density measurement container containing the polymer particles was measured, and the bulk density was determined by the following formula (1). The said operation was performed 5 times and the average value was made into the bulk density (g / cm < 3 >) of a polymer particle.
Bulk density of polymer particles (ρ) = (C−B) / A (1)
（ポリマー粒子の平均粒子径の測定）
レーザー回折散乱法を原理とした粒度分布測定機（セイシン企業社製、「ＳＫレーザーマイクロンサイザー ＬＭＳ−３５０」）を用い、ポリマー粒子の粒度分布を屈折率１．３３０−０．０１ｉ、形状係数１．０００にて測定し、体積平均から算出された５０％正規分布の値を平均粒子径（μｍ）とした。
(Measurement of average particle diameter of polymer particles)
Using a particle size distribution analyzer based on the laser diffraction scattering method (“SK Laser Micronizer LMS-350” manufactured by Seishin Enterprise Co., Ltd.), the particle size distribution of the polymer particles is a refractive index of 1.330 to 0.01i, and a shape factor of 1 The average particle diameter (μm) was measured at 0.000 and the value of 50% normal distribution calculated from the volume average was used.
（粒子構造の分析）
ポリマー粒子を乾燥させて乾燥粉とし、該乾燥粉をＵＶ硬化型アクリル系樹脂で重合包埋した後、ダイヤモンドナイフを装着したミクロトームにより、０．５ｍｍ×０．５ｍｍの大きさで約７０ｎｍの厚さの切片を切り出し、ＴＥＭ観察用グリッド上に回収した（配置した）。
ついで、切片を載せたグリッドを酢酸イソアミルに浸して包埋樹脂（ＵＶ硬化型アクリル系樹脂）を溶解除去、乾燥して試験片とし、透過型電子顕微鏡により、加速電圧８０ｋＶ、観察倍率３，０００〜５，０００倍の条件で観察した。
空孔率の計測には日本ローパー社製の画像解析ソフト「Ｉｍａｇｅ−Ｐｒｏ Ｐｌｕｓ」を用い、画像上で２μｍ×２μｍの計測範囲を設定して、この範囲内にてポリマー粒子の半径線上で最表層から中心に向かって順次移動しながら、空孔が占める比率を計測して空孔率（％）を求めた。
１個のポリマー粒子について３方向から計測した平均値から、ポリマー粒子の表面からの距離と空孔率との関係を求めた。また、１個の試験片について１０個以上のポリマー粒子を計測した。その際、個の試験片の中でみかけの粒径の大きいものを計測した。このようにして、空孔率が２０％以上の部分を外周部、２０％未満の部分を中心部とし、二重構造の有無を確認した。
さらに、外周部の厚さを測定し、その平均値を求め、これを外周部の平均厚さとした。
また、ポリマー粒子の表面の空孔率の平均値を求め、これを表面空孔率とした。
(Particle structure analysis)
The polymer particles are dried to obtain a dry powder, and the dry powder is polymer-embedded with a UV curable acrylic resin, and then a thickness of about 70 nm in a size of 0.5 mm × 0.5 mm by a microtome equipped with a diamond knife. A section was cut out and collected (arranged) on a TEM observation grid.
Next, the grid on which the section was placed was immersed in isoamyl acetate to dissolve and remove the embedding resin (UV curable acrylic resin), dried to obtain a test piece, and an accelerating voltage of 80 kV and an observation magnification of 3,000 using a transmission electron microscope. It was observed under the condition of 5,000 times.
For the measurement of porosity, the image analysis software “Image-Pro Plus” manufactured by Nippon Roper is used, and a measurement range of 2 μm × 2 μm is set on the image. While sequentially moving from the surface layer toward the center, the ratio of the voids was measured to obtain the porosity (%).
The relationship between the distance from the surface of the polymer particle and the porosity was determined from the average value measured from three directions for one polymer particle. In addition, ten or more polymer particles were measured for one test piece. At that time, a specimen having a large apparent particle diameter was measured. In this way, the presence or absence of a double structure was confirmed with the portion having a porosity of 20% or more as the outer peripheral portion and the portion having a porosity of less than 20% as the central portion.
Furthermore, the thickness of the outer peripheral part was measured, the average value was calculated | required, and this was made into the average thickness of an outer peripheral part.
Moreover, the average value of the porosity of the surface of the polymer particle was calculated | required and this was made into the surface porosity.
（ポリマー粒子の溶解性の評価）
−５℃に冷却したジメチルアセトアミド溶剤に、固形分が２１質量％になるように均一にポリマー粒子を分散させた分散液をスライドグラスに挟み、ＬＩＮＫＡＭ社製のホットステージにより１０℃／分で昇温しながら、位相差顕微鏡像によって２００倍の視野内のポリマー粒子の個数を計測した。溶解前（昇温前）のポリマー粒子の個数をｎ（０）個、昇温温度ｔ℃のときのポリマー粒子の個数をｎ（ｔ）個として、溶解進行率を下記式（２）より算出し、溶解開始から溶解終了（溶解進行率１００％）までに要する時間を溶解時間（分）とした。
溶解進行率（％）＝（１−ｎ（ｔ）／ｎ（０））×１００ ・・・（２）
(Evaluation of solubility of polymer particles)
A dispersion in which polymer particles are uniformly dispersed in a dimethylacetamide solvent cooled to −5 ° C. so as to have a solid content of 21% by mass is sandwiched between slide glasses, and the temperature is increased at 10 ° C./min by a LINKAM hot stage. While warming, the number of polymer particles in a 200 × field of view was measured by a phase contrast microscope image. The number of polymer particles before dissolution (before temperature increase) is n (0), the number of polymer particles at temperature increase temperature t ° C. is n (t), and the rate of dissolution is calculated from the following formula (2). The time required from the start of dissolution to the end of dissolution (dissolution progress rate 100%) was defined as dissolution time (minutes).
Dissolution rate (%) = (1−n (t) / n (0)) × 100 (2)
＜実施例１＞
容量８０Ｌのステンレス製で、グラスライニングしたタービン撹拌翼付き重合釜に、脱イオン交換水５７．４ｋｇと、ポリマー粒子の組成比が表１に示す値になるように各単量体単位を含有した単量体組成物１９．１ｋｇとを投入し、単量体組成物に対して０．３５質量％の過硫酸アンモニウム（酸化剤）と、０．５質量％の亜硫酸水素アンモニウム（還元剤）と、０．３ｐｐｍの硫酸第一鉄（Ｆｅ２ＳＯ４・７Ｈ２Ｏ、重合開始剤）と、０．１質量％の硫酸（ｐＨ調整剤）を各々脱イオン交換水に溶解した各水溶液を重合釜に供給した。この際、重合反応液のｐＨが３．０になるように、硫酸の供給量を調整した。ついで重合反応液の温度を５０℃に保持しながら十分に攪拌を行い、平均滞在時間が７０分になるようにして、重合釜オーバーフローにより連続的にポリマー水系分散液（重合スラリー）を取り出した。
<Example 1>
A polymer kettle made of stainless steel with a capacity of 80 L and equipped with a glass-lined turbine stirring blade contained 57.4 kg of deionized water and each monomer unit so that the composition ratio of the polymer particles was the value shown in Table 1. 19.1 kg of the monomer composition was charged, and 0.35% by mass of ammonium persulfate (oxidizing agent), 0.5% by mass of ammonium bisulfite (reducing agent) with respect to the monomer composition, Each aqueous solution prepared by dissolving 0.3 ppm ferrous sulfate (Fe 2 SO 4 · 7H 2 O, polymerization initiator) and 0.1% by mass sulfuric acid (pH adjuster) in deionized water is used in the polymerization kettle. Supplied to. At this time, the supply amount of sulfuric acid was adjusted so that the pH of the polymerization reaction solution was 3.0. Next, the polymerization reaction liquid was sufficiently stirred while maintaining the temperature of the polymerization reaction liquid at 50 ° C. so that the average residence time was 70 minutes, and the polymer aqueous dispersion (polymerization slurry) was continuously taken out by the polymerization kettle overflow.
得られた重合スラリーに、単量体組成物に対して０．５質量％のシュウ酸ナトリウムおよび１．５質量％の重炭酸ナトリウム（重合停止剤）を水に溶解した重合停止剤水溶液を、重合スラリーのｐＨが５．５〜６．０になるように添加し、オリバー型連続フィルターで脱水処理した。
ついで、脱水処理物に、ポリマーに対して１０倍量の脱イオン交換水（７０℃に加温）を添加し、再度重合スラリーとした。ついで、この重合スラリーをオリバー型連続フィルターで脱水処理した。
ついで、脱水処理物をペレット状に成形し、８０℃にて８時間、熱風循環型の乾燥機にて乾燥後、ハンマーミルで粉砕し、ポリマー粒子を得た。
In the obtained polymerization slurry, a polymerization stopper aqueous solution in which 0.5% by mass of sodium oxalate and 1.5% by mass of sodium bicarbonate (polymerization stopper) were dissolved in water with respect to the monomer composition, It added so that pH of a polymerization slurry might be set to 5.5-6.0, and it spin-dry | dehydrated with the Oliver type | mold continuous filter.
Next, 10 times the amount of deionized exchange water (warmed to 70 ° C.) was added to the dehydrated product to obtain a polymerization slurry again. Subsequently, this polymerization slurry was dehydrated with an Oliver type continuous filter.
Subsequently, the dehydrated product was formed into pellets, dried at 80 ° C. for 8 hours with a hot-air circulating dryer, and then pulverized with a hammer mill to obtain polymer particles.
脱イオン交換水と単量体組成物の質量比Ｘ（脱イオン交換水／単量体組成物）、および還元剤と酸化剤の質量比Ｙ（還元剤／酸化剤）を表１に示す。
さらに、得られたポリマー粒子の物性を測定した。結果を表１に示す。
また、透過型電子顕微鏡（ＴＥＭ）により測定したポリマー粒子のＴＥＭ画像を図１に示す。
Table 1 shows the mass ratio X (deionized water / monomer composition) between the deionized water and the monomer composition, and the mass ratio Y (reducing agent / oxidant) between the reducing agent and the oxidizing agent.
Furthermore, the physical properties of the obtained polymer particles were measured. The results are shown in Table 1.
Moreover, the TEM image of the polymer particle measured with the transmission electron microscope (TEM) is shown in FIG.
＜比較例１＞
重合釜に投入する脱イオン交換水の量を６３．８ｋｇ、単量体組成物の量を１２．８ｋｇに変更した以外は、実施例１と同様にしてポリマー粒子を調製し、各測定を行った。結果を表１に示す。
<Comparative Example 1>
Polymer particles were prepared in the same manner as in Example 1 except that the amount of deionized water to be charged into the polymerization kettle was changed to 63.8 kg and the amount of the monomer composition was changed to 12.8 kg. It was. The results are shown in Table 1.
＜比較例２＞
重合釜に投入する脱イオン交換水の量を６０．０ｋｇ、単量体組成物の量を１５．０ｋｇ、単量体組成物に対する過硫酸アンモニウムの量を０．２９質量％、亜硫酸水素アンモニウムの量を０．８７質量％、硫酸第一鉄の量を５．０ｐｐｍ、硫酸の量を０．７質量％に変更した以外は、実施例１と同様にしてポリマー粒子を調製し、各測定を行った。結果を表１に示す。
<Comparative Example 2>
The amount of deionized water to be charged into the polymerization kettle is 60.0 kg, the amount of the monomer composition is 15.0 kg, the amount of ammonium persulfate with respect to the monomer composition is 0.29% by mass, and the amount of ammonium bisulfite Was prepared in the same manner as in Example 1, except that the amount of ferrous sulfate was changed to 5.0 ppm and the amount of sulfuric acid was changed to 0.7 mass%. It was. The results are shown in Table 1.
表１および図１から明らかなように、実施例１で得られた、嵩密度が０．２７ｇ／ｃｍ３であり、中心部と外周部とからなる二重構造のポリマー粒子は、溶解時間が４．９分と短く、溶解性に優れていた。
一方、比較例１および２で得られた、嵩密度が０．２５ｇ／ｃｍ３未満であり、二重構造を有さないポリマー粒子は、溶解性の評価においてジメチルアセトアミド溶剤に溶解させたところ、実施例１に比べて多くのママコが発生した。その結果、溶解時間が比較例１では７．２分、比較例２では６．４分と、いずれも実施例１に比べて長く、溶解性が劣っていた。また、これらポリマー粒子は、その内部まで空孔率が２０％以上であった。
As is clear from Table 1 and FIG. 1, the polymer particles having a bulk density of 0.27 g / cm 3 obtained in Example 1 and having a central part and an outer peripheral part have a dissolution time of It was as short as 4.9 minutes and was excellent in solubility.
On the other hand, the polymer particles obtained in Comparative Examples 1 and 2 having a bulk density of less than 0.25 g / cm 3 and having no double structure were dissolved in a dimethylacetamide solvent in the evaluation of solubility. Compared with Example 1, many mams were generated. As a result, the dissolution time was 7.2 minutes in Comparative Example 1 and 6.4 minutes in Comparative Example 2, both of which were longer than Example 1 and poor in solubility. Further, these polymer particles had a porosity of 20% or more up to the inside thereof.
Claims (3)
空孔率が２０％未満である中心部と、該中心部を取り囲み、かつ空孔率が２０％以上である外周部とから構成されたことを特徴とするポリアクリロニトリル系ポリマー粒子。 It is obtained by polymerizing a monomer composition containing 95% by mass or more of acrylonitrile units and 0.5% by mass or more of acrylamide units, and has a bulk density of 0.25 to 0.40 g / cm 3 ,
A polyacrylonitrile-based polymer particle comprising a central portion having a porosity of less than 20% and an outer peripheral portion surrounding the central portion and having a porosity of 20% or more.
水と前記単量体組成物との質量比（水／単量体組成物）が２．５〜４．０、前記還元剤と前記酸化剤との質量比（還元剤／酸化剤）が１．０〜２．５であることを特徴とするポリアクリロニトリル系ポリマー粒子の製造方法。 In the method for producing polyacrylonitrile-based polymer particles in which a reducing agent and an oxidizing agent are used, and a monomer composition containing 95% by mass or more of acrylonitrile units and 0.5% by mass or more of acrylamide units is subjected to redox aqueous suspension polymerization.
The mass ratio of water to the monomer composition (water / monomer composition) is 2.5 to 4.0, and the mass ratio of the reducing agent to the oxidizing agent (reducing agent / oxidizing agent) is 1. A method for producing polyacrylonitrile-based polymer particles, characterized in that it is from 0 to 2.5.
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