JP5243824B2 - Platinum colloid solution and method for producing the same - Google Patents
Platinum colloid solution and method for producing the same Download PDFInfo
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims description 316
- 229910052697 platinum Inorganic materials 0.000 title claims description 161
- 239000000084 colloidal system Substances 0.000 title claims description 88
- 238000004519 manufacturing process Methods 0.000 title claims description 30
- 239000000243 solution Substances 0.000 claims description 93
- 239000002245 particle Substances 0.000 claims description 33
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 27
- 150000003057 platinum Chemical class 0.000 claims description 21
- 238000000108 ultra-filtration Methods 0.000 claims description 19
- 239000012266 salt solution Substances 0.000 claims description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- -1 platinum ions Chemical class 0.000 claims description 9
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 8
- 230000005587 bubbling Effects 0.000 claims description 6
- 238000010979 pH adjustment Methods 0.000 claims description 6
- 239000003638 chemical reducing agent Substances 0.000 claims description 5
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical class [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 claims description 4
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 4
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 3
- 238000006722 reduction reaction Methods 0.000 description 39
- 239000003223 protective agent Substances 0.000 description 32
- 230000002776 aggregation Effects 0.000 description 31
- 238000004220 aggregation Methods 0.000 description 30
- 238000001556 precipitation Methods 0.000 description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 239000002904 solvent Substances 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 238000003860 storage Methods 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000000926 separation method Methods 0.000 description 6
- 239000002537 cosmetic Substances 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 235000013305 food Nutrition 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 230000007774 longterm Effects 0.000 description 5
- 239000012528 membrane Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000011946 reduction process Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910001410 inorganic ion Inorganic materials 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000012046 mixed solvent Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000002829 reductive effect Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- 230000002292 Radical scavenging effect Effects 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 125000005396 acrylic acid ester group Chemical group 0.000 description 2
- 230000003078 antioxidant effect Effects 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
- TUJKJAMUKRIRHC-UHFFFAOYSA-N hydroxyl Chemical compound [OH] TUJKJAMUKRIRHC-UHFFFAOYSA-N 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000010992 reflux Methods 0.000 description 2
- 229910001415 sodium ion Inorganic materials 0.000 description 2
- VCUVETGKTILCLC-UHFFFAOYSA-N 5,5-dimethyl-1-pyrroline N-oxide Chemical compound CC1(C)CCC=[N+]1[O-] VCUVETGKTILCLC-UHFFFAOYSA-N 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- FBPFZTCFMRRESA-KVTDHHQDSA-N D-Mannitol Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-KVTDHHQDSA-N 0.000 description 1
- 229930195725 Mannitol Natural products 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000003064 anti-oxidating effect Effects 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000000594 mannitol Substances 0.000 description 1
- 235000010355 mannitol Nutrition 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 238000013319 spin trapping Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 229910021642 ultra pure water Inorganic materials 0.000 description 1
- 239000012498 ultrapure water Substances 0.000 description 1
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- General Preparation And Processing Of Foods (AREA)
- Cosmetics (AREA)
- Catalysts (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
Description
本発明は、白金コロイド溶液及びその製造方法に関する。特に、高分子保護剤を含まない白金コロイド溶液及びその製造方法を提供する。 The present invention relates to a platinum colloid solution and a method for producing the same. In particular, a platinum colloid solution containing no polymer protective agent and a method for producing the same are provided.
白金コロイドは、触媒として自動車排ガス処理用途等に利用されており、燃料電池の電極としても使用されている。また、近年では、白金の光学特性を利用したバイオセンサーへの利用や、抗酸化性を利用した食料品、化粧品等への利用も行われている。 Platinum colloid is used as a catalyst for automobile exhaust gas treatment and the like, and is also used as a fuel cell electrode. In recent years, it has also been used for biosensors utilizing the optical properties of platinum, and for foods and cosmetics utilizing antioxidant properties.
このような白金コロイドとしては、溶媒中に１〜１００ｎｍ程度の白金微粒子を分散、懸濁し、溶媒として液体を用いた白金コロイド溶液が通常用いられている。これら白金コロイド溶液としては、高分子や界面活性剤等の保護剤を含むものが一般的である。保護剤を含むコロイド溶液では、コロイド粒子の表面に保護剤が吸着することにより、白金粒子同士の直接接触が抑制され、コロイドの凝集や沈殿を防ぐことができる。特許文献１には、保護剤としてポリ（アクリル酸エステル）を用いた白金コロイド溶液が記載されている。ポリ（アクリル酸エステル）を用いた場合、白金粒子の凝集を抑制できることに加え、粒子の粒径制御も可能となる。
しかしながら、保護剤を含む白金コロイド溶液では、食料品や化粧品等の抗酸化剤用途において、人体に与える安全面での影響が問題となる場合がある。また、バイオセンサー用途に用いる場合、保護剤の種類によって、測定の検出感度が低下する場合があった。また、触媒用途では、白金表面が保護剤で被覆されることにより、触媒性能が充分には発揮されないことがあった。 However, in the case of a colloidal platinum solution containing a protective agent, there may be a problem in terms of safety on the human body in the use of antioxidants such as foods and cosmetics. In addition, when used for biosensor applications, the detection sensitivity of measurement may be reduced depending on the type of protective agent. Moreover, in the catalyst use, catalyst performance may not be fully exhibited because the platinum surface is coated with a protective agent.
このため、白金コロイドの用途により、保護剤を含まない白金コロイド溶液の提供が求められる場合があるが、保護剤を含む白金コロイド溶液と比較すると、製造時に凝集や沈殿を生じやすいものであり、製造後に白金コロイド溶液を保管する際も、長期の保存が困難であった。また、白金コロイド溶液を用いて加工した食品等を、白金濃度の高いものとしたい場合、添加剤となる白金コロイド溶液の白金濃度も高いことが好ましい。しかし、保護剤を含まない白金コロイド溶液は、白金濃度の高いものとすると、特に白金粒子の凝集による沈殿を生じやすい傾向があった。 For this reason, depending on the use of the platinum colloid, it may be required to provide a platinum colloid solution containing no protective agent, but compared to a platinum colloid solution containing a protective agent, it tends to cause aggregation and precipitation during production, Even when the platinum colloid solution is stored after production, long-term storage is difficult. In addition, when a food processed using a platinum colloid solution is to have a high platinum concentration, the platinum concentration of the platinum colloid solution as an additive is preferably high. However, a platinum colloid solution containing no protective agent tends to cause precipitation due to aggregation of platinum particles, particularly when the platinum concentration is high.
そして、白金コロイド溶液を製造する際も、保護剤を含まない場合は、白金イオンの還元による白金粒子の形成が進行しにくい傾向があった。また、白金粒子の形成が進行した場合でも、白金粒子の凝集による沈殿が発生し、層分離等を生じやすいものであった。 And also when manufacturing a platinum colloid solution, when a protective agent was not included, there existed a tendency for formation of the platinum particle by the reduction | restoration of a platinum ion not to advance easily. Even when the formation of platinum particles progressed, precipitation due to aggregation of the platinum particles occurred, and layer separation or the like was likely to occur.
そこで、本発明は、保護剤を含まない白金コロイド溶液に関し、高濃度であっても、凝集や沈殿を生じにくく、長期間安定性に優れるものを提供することを目的とする。また、保護剤を含まない白金コロイド溶液の製造方法であって、白金イオンの還元が安定して進行し、凝集による沈殿を防いで、層分離等の発生を抑制できる方法を提供する。 Therefore, the present invention relates to a platinum colloid solution that does not contain a protective agent, and an object thereof is to provide a platinum colloid solution that does not easily aggregate or precipitate even at a high concentration and has excellent long-term stability. Also provided is a method for producing a colloidal platinum solution that does not contain a protective agent, wherein the reduction of platinum ions proceeds stably, prevents precipitation due to aggregation, and suppresses the occurrence of layer separation or the like.
本発明者等は、上記課題を解決するため、保護剤を含まず、かつ、白金濃度も高い白金コロイド溶液について鋭意検討を行った。そして、白金コロイド溶液を保存する際のｐＨに着目したところ、凝集による沈殿を生じやすい白金コロイド溶液は、保存中にｐＨが低下する傾向にあることが分かった。また、ｐＨが低下しにくい白金コロイド溶液でも、電気伝導度が一定の値以上であると、長期間の保存中に、凝集による沈殿を生じる場合があった。その結果、ｐＨ及び電気伝導度が所定の範囲内である場合には、長期間、凝集による沈殿を生じにくい白金コロイド溶液となることを見出し、本発明に想到した。 In order to solve the above-mentioned problems, the present inventors diligently studied a platinum colloid solution containing no protective agent and having a high platinum concentration. Then, when focusing on the pH at the time of storing the colloidal platinum solution, it was found that the platinum colloidal solution which is likely to cause precipitation due to aggregation tends to decrease the pH during storage. Further, even in a platinum colloid solution in which the pH is not easily lowered, precipitation due to aggregation may occur during long-term storage when the electric conductivity is a certain value or more. As a result, when the pH and electrical conductivity are within a predetermined range, the inventors have found that the solution is a platinum colloid solution that hardly causes precipitation due to aggregation for a long period of time.
すなわち、本発明は、白金粒子からなる白金コロイドと、水又は水及び有機溶媒の混合溶媒よりなる溶媒とからなる保護剤を含まない白金コロイド溶液において、白金コロイド溶液中の白金含有量が３００〜２００００ｐｐｍ、かつ、ｐＨ５．０〜１２．０、電気伝導度１００ｍＳ／ｍ以下である白金コロイド溶液に関する。 That is, the present invention relates to a platinum colloid solution that does not include a protective agent composed of platinum colloid composed of platinum particles and a solvent composed of water or a mixed solvent of water and an organic solvent, and the platinum content in the platinum colloid solution is 300 to The present invention relates to a platinum colloid solution having 20000 ppm, pH 5.0 to 12.0, and electric conductivity of 100 mS / m or less.
本発明の白金コロイド溶液は、保護剤を含まないため、食料品、化粧品、又はバイオセンサー等の用途に好適である。また、保護剤を含まない高濃度の白金コロイド溶液であるにもかかわらず、凝集や沈殿を生じにくく、３０日以上安定して保存可能となる。このように、本発明の白金コロイド溶液の安定性が高いものとなるのは、ｐＨ及び電気伝導度が上記範囲内であることにより、溶液中で正又は負の電荷を帯びた白金粒子について、粒子間の斥力や引力のバランスが良好となるためと考えられる。 Since the platinum colloid solution of the present invention does not contain a protective agent, it is suitable for foodstuffs, cosmetics, biosensors and the like. Moreover, although it is a high-concentration platinum colloid solution containing no protective agent, it is difficult to cause aggregation and precipitation and can be stably stored for 30 days or more. As described above, the platinum colloid solution of the present invention has high stability because the pH and electrical conductivity are within the above ranges, so that the positively or negatively charged platinum particles in the solution, This is considered to be because the balance between repulsive force and attractive force between particles becomes good.
この白金コロイド溶液は、白金含有量が３００〜２００００ｐｐｍと高濃度であるため、添加剤として用いた場合、加工後の製品を白金濃度の高いものとすることが容易となる。白金濃度は、２００００ｐｐｍを超えると、凝集による沈殿が生じやすくなり、３００ｐｐｍ未満であると、添加剤として用いる場合、加工時の取り扱い性が不十分となる。白金含有量は、好ましくは６００〜１００００ｐｐｍである。 Since this platinum colloid solution has a high platinum content of 300 to 20000 ppm, when used as an additive, it becomes easy to make the processed product high in platinum concentration. If the platinum concentration exceeds 20000 ppm, precipitation due to agglomeration tends to occur, and if it is less than 300 ppm, handleability at the time of processing becomes insufficient when used as an additive. The platinum content is preferably 600 to 10,000 ppm.
本発明の白金コロイド溶液は、ｐＨ５．０〜１２．０であるとともに、電気伝導度は、１００ｍＳ／ｍ以下であることにより、保護剤を含まないにもかかわらず、凝集や沈殿が発生しにくいものとなる。後述する製造方法において説明するように、白金コロイド溶液は、還元処理直後（製造から２日以内）はｐＨ７．０〜１２．０の範囲内であり、ｐＨ７．５〜１０．５の範囲内であることが好ましい。ｐＨ７．０未満の場合や、ｐＨ１２．０を超えると、凝集による沈殿が発生しやすくなる。 The platinum colloid solution of the present invention has a pH of 5.0 to 12.0 and has an electric conductivity of 100 mS / m or less, so that aggregation and precipitation are unlikely to occur despite the absence of a protective agent. It will be a thing. As will be described later in the production method, the colloidal platinum solution is within the range of pH 7.0 to 12.0 and within the range of pH 7.5 to 10.5 immediately after the reduction treatment (within 2 days from production). Preferably there is. If the pH is less than 7.0 or exceeds pH 12.0, precipitation due to aggregation tends to occur.
還元処理後、保管中に白金コロイド溶液のｐＨは低下する場合があるが、低下後（製造から２日経過後）のｐＨが５．０〜１１．０の範囲内であれば、凝集による沈殿が発生しにくいものとなる。ｐＨ５．０未満の場合や、ｐＨ１１．０を超えると、凝集による沈殿が発生しやすくなる。この低下後のｐＨは、５．０〜１０．５の範囲内であることが好ましい。 After the reduction treatment, the pH of the platinum colloid solution may decrease during storage, but if the pH after the decrease (after 2 days from production) is within the range of 5.0 to 11.0, precipitation due to aggregation will occur. It is difficult to generate. When the pH is less than 5.0 or exceeds pH 11.0, precipitation due to aggregation tends to occur. It is preferable that pH after this fall exists in the range of 5.0-10.5.
電気伝導度は、溶液が電気を通しやすいかどうかの指標となる値であり、電気伝導度が大きいと、無機イオン等の電解質が多く含まれる傾向となり、白金粒子の分散性が低下するものと考えられる。無機イオンは、白金粒子の周りに集中しやすく、白金粒子間の斥力を低下させる要因となるためである。無機イオンとしては、白金コロイド溶液の製造過程において、ナトリウムイオンやカルシウムイオン等が含まれやすいことが知られている。電気伝導度は１００ｍＳ／ｍを超えると、長期間保存した場合に、凝集による沈殿を生じる場合がある。電気伝導度は、低いほどｐＨの変動が少なく、長期安定性に優れた白金コロイド溶液となるため下限値は限定されない。但し、長期安定性と製造効率とのバランスを考慮する場合には、電気伝導度５ｍＳ／ｍ以上とする。 The electrical conductivity is a value that indicates whether the solution easily conducts electricity. If the electrical conductivity is large, the electrolyte tends to contain a large amount of inorganic ions and the like, and the dispersibility of the platinum particles decreases. Conceivable. This is because inorganic ions tend to concentrate around the platinum particles and cause a reduction in repulsive force between the platinum particles. As inorganic ions, it is known that sodium ions, calcium ions and the like are easily contained in the production process of the platinum colloid solution. When the electrical conductivity exceeds 100 mS / m, precipitation may occur due to aggregation when stored for a long period of time. The lower the electrical conductivity is, the lower the pH value is, and the lower limit value is not limited because the platinum colloid solution has excellent long-term stability. However, when considering the balance between long-term stability and production efficiency, the electric conductivity is set to 5 mS / m or more.
本発明の白金コロイド溶液の溶媒は、水又は水及び有機溶媒の混合溶媒よりなる。特に、溶媒が水であると、食料品や化粧品用途にも好適なものとなる。 The solvent of the platinum colloid solution of the present invention is composed of water or a mixed solvent of water and an organic solvent. In particular, when the solvent is water, it is suitable for food and cosmetic applications.
次に、白金コロイド溶液の製造方法について説明する。従来の白金コロイド溶液では、保護剤を含むものが一般的であり、溶媒中に白金塩と保護剤とを添加した後、還元処理等を行って製造するものであった。この方法では、製造工程の初期段階で保護剤を添加するため、溶液の安定性が向上し、製造工程で多少のｐＨや温度変化があっても、白金粒子の凝集や沈殿を生じることが少なかった。 Next, a method for producing a platinum colloid solution will be described. Conventional platinum colloidal solutions generally contain a protective agent, and are manufactured by adding a platinum salt and a protective agent to a solvent and then performing a reduction treatment or the like. In this method, since a protective agent is added at the initial stage of the production process, the stability of the solution is improved, and even if there is some pH or temperature change in the production process, platinum particles are hardly aggregated or precipitated. It was.
そして、本発明の保護剤を含まない白金コロイド溶液の製造方法は、基本的に、上記した従来の保護剤を含む白金コロイド溶液の製造方法と同様の還元方法を採用するものである。しかし、保護剤を含む場合と比べ、還元工程において、白金粒子の形成が良好に進行しない場合や、白金粒子の形成が進行しても、凝集による沈殿が発生して層分離を生じる場合があった。このような問題を解決すべく、本発明者等は、還元工程前の白金塩溶液の調製条件に着目したところ、ｐＨ及び溶存酸素濃度を調整することにより、白金粒子の形成を良好に進行させることができることを見出した。 And the manufacturing method of the platinum colloid solution which does not contain the protective agent of this invention employ | adopts the reduction | restoration method similar to the manufacturing method of the platinum colloid solution containing the above-mentioned conventional protective agent fundamentally. However, compared to the case where a protective agent is included, in the reduction process, the formation of platinum particles may not proceed well, or even if the formation of platinum particles proceeds, precipitation due to aggregation may occur, resulting in layer separation. It was. In order to solve such a problem, the present inventors focused on the preparation conditions of the platinum salt solution before the reduction step, and by appropriately adjusting the pH and dissolved oxygen concentration, the formation of platinum particles proceeds favorably. I found that I can do it.
さらに、保護剤を含まない場合、還元工程後も、白金粒子の凝集による沈殿を生じやすかった。このため、本発明者等は、還元工程後の白金コロイド溶液の保存条件についても鋭意検討した。そして、還元工程後、得られた白金コロイド溶液の電気伝導度及びｐＨを一定範囲内に保持することにより、長期間安定して保存可能となる白金コロイド溶液が得られることを見出した。 Furthermore, when no protective agent was included, precipitation due to aggregation of platinum particles was likely to occur even after the reduction step. For this reason, the present inventors have also intensively studied the storage conditions of the platinum colloid solution after the reduction step. And it discovered that the platinum colloid solution which can be stably preserve | saved for a long period of time is obtained by hold | maintaining the electrical conductivity and pH of the obtained platinum colloid solution in a fixed range after a reduction process.
すなわち、本発明の白金コロイド溶液は、白金イオンの還元工程前に白金塩溶液のｐＨ及び溶存酸素濃度を調整し、還元処理後には、得られた白金コロイド溶液の電気伝導度及びｐＨを調整する方法により製造できる。より具体的には、白金塩溶液中の白金イオンを還元し、白金粒子からなる白金コロイドを形成する還元工程を含む白金コロイド溶液の製造方法であって、還元工程前に、白金塩溶液のｐＨを７．０〜８．５に調整し、不活性ガスのバブリングにより溶存酸素濃度を１．０ｐｐｍ以下に調整する工程を有し、還元工程後、得られた白金コロイド溶液を、限外ろ過により電気伝導度１００ｍＳ／ｍ以下、白金含有量３００〜２００００ｐｐｍの範囲内とし、ｐＨを７．０〜１２．０に調整する工程を有する白金コロイド溶液の製造方法である。 That is, the platinum colloid solution of the present invention adjusts the pH and dissolved oxygen concentration of the platinum salt solution before the platinum ion reduction step, and adjusts the electrical conductivity and pH of the obtained platinum colloid solution after the reduction treatment. It can be manufactured by a method. More specifically, a method for producing a platinum colloid solution including a reduction step of reducing platinum ions in the platinum salt solution to form a platinum colloid composed of platinum particles, wherein the pH of the platinum salt solution is reduced before the reduction step. Is adjusted to 7.0-8.5, and the dissolved oxygen concentration is adjusted to 1.0 ppm or less by bubbling with an inert gas. After the reduction step, the obtained platinum colloid solution is subjected to ultrafiltration. It is a method for producing a platinum colloidal solution having a step of adjusting the pH to 7.0 to 12.0 with an electric conductivity of 100 mS / m or less and a platinum content of 300 to 20000 ppm.
以上説明したように、この製造方法によれば、保護剤を含まない白金コロイド溶液であっても、白金イオンの還元工程において、白金粒子の凝集沈殿による層分離等の発生を抑制できるとともに、還元工程後も、白金粒子を、４週間以上、凝集による沈殿を生じることなく保存できる。 As described above, according to this production method, even in the case of a platinum colloid solution that does not contain a protective agent, generation of layer separation due to aggregation and precipitation of platinum particles can be suppressed in the platinum ion reduction step, and reduction can be achieved. Even after the process, the platinum particles can be stored for 4 weeks or more without causing precipitation due to aggregation.
以下、本発明の白金コロイド溶液の製造方法について詳細に説明する。原料となる白金塩溶液には、ジニトロジアンミン白金塩、塩化白金酸、塩化第二白金、ヘキサヒドロキソ白金酸、テトラアンミン白金等のいずれか1種以上を使用できる。好ましくは、ジニトロジアンミン白金塩を用いる。また、これら白金塩を添加する溶媒としては、水又は水及び有機溶媒の混合溶媒を使用できる。尚、白金塩溶液中の白金濃度は、０．１〜１０．０ｗｔ％のものを使用することが好ましい。白金塩溶液中の白金濃度を調整することにより、得られた白金コロイド溶液中における白金含有量の絶対量を調整できる。０．１ｗｔ％よりも濃度が薄いと全体の液量が増えてしまい、製造が困難になる。１０．０ｗｔ％よりも濃度が濃いと白金塩が溶解しにくい傾向となる。 Hereinafter, the method for producing a platinum colloid solution of the present invention will be described in detail. As the raw material platinum salt solution, one or more of dinitrodiammine platinum salt, chloroplatinic acid, diplatinum chloride, hexahydroxoplatinic acid, tetraammineplatinum and the like can be used. Preferably, dinitrodiammine platinum salt is used. Moreover, as a solvent to which these platinum salts are added, water or a mixed solvent of water and an organic solvent can be used. The platinum concentration in the platinum salt solution is preferably 0.1 to 10.0 wt%. By adjusting the platinum concentration in the platinum salt solution, the absolute amount of platinum content in the obtained platinum colloid solution can be adjusted. If the concentration is lower than 0.1 wt%, the total amount of liquid increases, making production difficult. If the concentration is higher than 10.0 wt%, the platinum salt tends to be hardly dissolved.
白金塩溶液は、あらかじめｐＨ及び溶存酸素濃度を調整してから、還元処理を行うものとする。このように、還元工程前の条件管理を厳格に行うことにより、保護剤を使用しなくとも、還元工程において白金コロイド粒子を安定して形成できる。具体的には、還元工程前にｐＨを７．０〜８．５に調整する。ｐＨがこの範囲内であると、白金粒子の凝集による沈殿の発生等を抑制し、白金コロイド粒子を安定して形成できる。ｐＨ７．０未満や、８．５を超えると、白金粒子の凝集が生じやすい傾向がある。好ましくは、ｐＨ７．５〜７．９に調整する。 The platinum salt solution is subjected to reduction treatment after adjusting pH and dissolved oxygen concentration in advance. Thus, by strictly controlling the conditions before the reduction step, the colloidal platinum particles can be stably formed in the reduction step without using a protective agent. Specifically, the pH is adjusted to 7.0 to 8.5 before the reduction step. When the pH is within this range, the occurrence of precipitation due to aggregation of platinum particles is suppressed, and platinum colloid particles can be stably formed. If the pH is less than 7.0 or exceeds 8.5, the platinum particles tend to aggregate. Preferably, the pH is adjusted to 7.5 to 7.9.
上記した、白金塩溶液のｐＨ調製は、水酸化ナトリウム及び／又は炭酸水素ナトリウムを用いて行うことが好ましい。これらのアルカリ性溶液を用いると、還元処理において層分離等が発生することなく安定して白金粒子を形成できる。また、ｐＨ調整は水酸化ナトリウムを添加した後、炭酸水素ナトリウムを添加することがさらに好ましい。ｐＨの正確な調整が可能になるとともに、高濃度の白金コロイド溶液とすることも可能となる。 The pH adjustment of the platinum salt solution described above is preferably performed using sodium hydroxide and / or sodium bicarbonate. When these alkaline solutions are used, platinum particles can be stably formed without causing layer separation in the reduction treatment. Further, it is more preferable to adjust the pH by adding sodium hydrogen carbonate after adding sodium hydroxide. The pH can be adjusted accurately, and a high-concentration platinum colloid solution can be obtained.
また、還元工程の前には、上記ｐＨの調整とともに溶存酸素濃度を調整する。溶存酸素濃度は、不活性ガスのバブリングによって、濃度１．０ｐｐｍ以下となるように調整する。溶存酸素濃度が高くなると、還元工程において白金イオンの還元が進行しにくくなり、白金コロイドが不安定で凝集しやすい傾向となる。溶存酸素濃度が１．０ｐｐｍを超えると、白金コロイド溶液の液面に浮遊する凝集体が発生する場合がある。尚、バブリングに用いるガスとしては、アルゴンや窒素等を使用できる。 Moreover, before a reduction process, a dissolved oxygen concentration is adjusted with adjustment of the said pH. The dissolved oxygen concentration is adjusted to be 1.0 ppm or less by bubbling with an inert gas. When the dissolved oxygen concentration becomes high, the reduction of platinum ions hardly proceeds in the reduction step, and the platinum colloid tends to be unstable and easily aggregated. When the dissolved oxygen concentration exceeds 1.0 ppm, aggregates floating on the liquid surface of the platinum colloid solution may be generated. In addition, argon, nitrogen, etc. can be used as gas used for bubbling.
ｐＨ及び溶存酸素濃度を調整した後、白金コロイドを形成するための還元処理を行う。この還元工程においては、還元剤として、水素、メタノール、エタノール、プロパノール、エチレングリコール、水素化ホウ素ナトリウム、ヒドラジン等の一般的な還元剤を使用できる。還元剤は、好ましくはエタノールを使用する。還元反応中の雰囲気ガスとしては、アルゴンガス、窒素ガス等を使用できる。酸化反応を抑制し、還元反応を充分に進行させることができるからである。 After adjusting the pH and dissolved oxygen concentration, reduction treatment for forming a platinum colloid is performed. In this reduction step, a general reducing agent such as hydrogen, methanol, ethanol, propanol, ethylene glycol, sodium borohydride, hydrazine or the like can be used as the reducing agent. As the reducing agent, ethanol is preferably used. Argon gas, nitrogen gas, etc. can be used as the atmospheric gas during the reduction reaction. This is because the oxidation reaction can be suppressed and the reduction reaction can proceed sufficiently.
還元反応は、加熱還流や、マイクロウェーブ等により行うことができる。還元反応の処理時間は、マイクロウェーブを用いる場合は０．２〜３時間、加熱還流による場合は３〜１０時間とすることが好ましい。処理時間が短すぎると、白金粒子の形成が充分に進行せず、処理時間が長すぎると、凝集による沈殿が生じやすくなる。また、還元処理における液温は、７０〜１００℃とすることが好ましく、８０〜９２℃とすることがより好ましい。７０℃未満では、還元反応が進行しにくい傾向があり、１００℃より高温では、沈殿が生じやすくなる。 The reduction reaction can be performed by heating under reflux, microwave, or the like. The treatment time for the reduction reaction is preferably 0.2 to 3 hours when microwaves are used, and 3 to 10 hours when heated and refluxed. If the treatment time is too short, the formation of platinum particles does not proceed sufficiently, and if the treatment time is too long, precipitation due to aggregation tends to occur. Moreover, it is preferable to set it as 70-100 degreeC, and, as for the liquid temperature in a reduction process, it is more preferable to set it as 80-92 degreeC. If it is less than 70 degreeC, there exists a tendency for a reductive reaction to advance, and precipitation becomes easy to arise at temperature higher than 100 degreeC.
還元処理後は、限外ろ過を行い、電気伝導度を１００ｍＳ／ｍ以下、白金含有量は、３００〜２００００ｐｐｍとする。白金含有量は、６００〜１００００ｐｐｍであると好ましい。限外ろ過によれば、未反応成分や、ナトリウムイオン、塩素、硝酸イオン等を取り除くことができ、製造した白金コロイド溶液の保存中における凝集沈殿を抑制できる。白金含有量は、限外ろ過時に溶媒を供給する量を調整することにより、容易に調整できる。白金含有量は、３００ｐｐｍ未満であると同じ白金量とするために多くの液量が必要なため、加工性に劣る傾向となり、２００００ｐｐｍを超えると凝集による沈殿を生じやすくなる。限外ろ過には、分画分子量（ＭＷＣＯ：Molecular Weight Cut Off）が５０００〜５００００の限外ろ過膜（ＵＦ膜）を用いるのが好ましく、ＭＷＣＯが７０００〜２００００のＵＦ膜を用いることがより好ましい。ＭＷＣＯが５０００未満であると、限外ろ過時に目詰まりが生じやすい傾向となり、５００００を超えると白金コロイドがＵＦ膜を透過してしまう場合がある。尚、この限外ろ過の処理は少なくとも１回行うが、複数回繰返し行っても良い。また、複数回の限外ろ過を行う場合、ろ過毎に溶媒添加量を適宜に変更しながら調整して白金含有量を調整しても良い。 After the reduction treatment, ultrafiltration is performed so that the electric conductivity is 100 mS / m or less and the platinum content is 300 to 20000 ppm. The platinum content is preferably 600 to 10,000 ppm. According to ultrafiltration, unreacted components, sodium ions, chlorine, nitrate ions and the like can be removed, and aggregation precipitation during storage of the produced platinum colloidal solution can be suppressed. The platinum content can be easily adjusted by adjusting the amount of solvent supplied during ultrafiltration. If the platinum content is less than 300 ppm, a large amount of liquid is required to obtain the same platinum content, so that the processability tends to be inferior, and if it exceeds 20000 ppm, precipitation due to aggregation tends to occur. For ultrafiltration, it is preferable to use an ultrafiltration membrane (UF membrane) having a molecular weight cut off (MWCO) of 5000 to 50000, and more preferably a UF membrane having a MWCO of 7000 to 20000. . If the MWCO is less than 5000, clogging tends to occur during ultrafiltration, and if it exceeds 50000, the platinum colloid may permeate the UF membrane. The ultrafiltration treatment is performed at least once, but may be repeated a plurality of times. Moreover, when performing ultrafiltration of multiple times, you may adjust, changing a solvent addition amount suitably for every filtration, and may adjust platinum content.
そして、還元処理後は、限外ろ過を行うとともに、得られた白金コロイド溶液のｐＨを７．０〜１２．０に調整する。ｐＨは７．５〜１０．０に調整することが好ましい。ｐＨ調整には、アルカリ性のｐＨ調整剤、例えば、水酸化ナトリウム、水酸化カリウム、水酸化カルシウム、アンモニア等を用いることができ、好ましくは水酸化ナトリウムを用いる。白金コロイドを形成した後、速やかにｐＨ調整することにより、長期間、凝集や沈殿を生じにくい白金コロイド溶液とすることができる。また、限外ろ過処理後、ｐＨを調整した白金コロイド溶液を保存している間にｐＨが変動した場合、再度ｐＨを７．０〜１２．０に調整することが好ましい。このとき、ｐＨ７．５〜１０．０に調整すると、より好ましい。 And after a reduction process, while performing ultrafiltration, pH of the obtained platinum colloid solution is adjusted to 7.0-12.0. The pH is preferably adjusted to 7.5 to 10.0. For pH adjustment, an alkaline pH adjuster such as sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia or the like can be used, and sodium hydroxide is preferably used. After the platinum colloid is formed, the pH is quickly adjusted to obtain a platinum colloid solution that hardly causes aggregation or precipitation for a long period of time. In addition, after the ultrafiltration treatment, when the pH fluctuates while the platinum colloid solution adjusted in pH is stored, it is preferable to adjust the pH again to 7.0 to 12.0. At this time, it is more preferable to adjust the pH to 7.5 to 10.0.
還元処理後、白金コロイド溶液のｐＨがやや低下する場合があるが、上記したようにｐＨ調整を数回繰り返す方法によれば、保存中にｐＨが低下した白金コロイド溶液であっても、ｐＨ調整を数回繰り返すことにより、ｐＨの変動しにくい白金コロイド溶液となることが分かった。 After the reduction treatment, the pH of the platinum colloid solution may decrease slightly. However, according to the method in which the pH adjustment is repeated several times as described above, even if the platinum colloid solution has a decreased pH during storage, the pH adjustment It was found that a platinum colloid solution in which the pH does not easily fluctuate by repeating several times.
以上で説明したように、本発明に係る白金コロイド溶液は、長期間凝集による沈殿が発生しにくく、分散性の高いものであり、保護剤を含まないため食品や化粧品用途にも好適である。また、白金濃度が３００〜２００００ｐｐｍであるため、添加剤として用いた場合に、製品に加工した後の白金濃度を高めることも容易となる。さらに、本発明の白金コロイドの製造方法によれば、白金イオンの還元が安定して進行し、層分離等の発生を抑制できる。 As described above, the platinum colloid solution according to the present invention is suitable for foods and cosmetics because it does not easily precipitate due to aggregation for a long period of time, has high dispersibility, and does not contain a protective agent. Moreover, since platinum concentration is 300-20000 ppm, when it uses as an additive, it becomes easy to raise platinum concentration after processing into a product. Furthermore, according to the method for producing a platinum colloid of the present invention, the reduction of platinum ions proceeds stably, and generation of layer separation or the like can be suppressed.
以下、本発明における最良の実施形態について説明する。 Hereinafter, the best embodiment of the present invention will be described.
実施例１：Ｐｔ濃度４．５３ｗｔ％のジニトロジアンミン白金６．６２ｇ（Ｐｔ含有量３００ｍｇ）を、水３００ｍＬ中に添加し白金塩溶液を調整した。この白金塩溶液に、１％水酸化ナトリウムを添加してｐＨ７．５６に調整した後、４％炭酸水素ナトリウムを添加してｐＨ７．８０に調整した。次に、還元剤としてエタノール６０ｇを添加した後、２Ｌ／ｍｉｎの速度でＡｒガスによるバブリングを１０分間行った。蛍光式酸素計（オートマチックシステムリサーチ社製、ＦＯ−９６０）を用いて酸素濃度を測定したところ、酸素濃度は検出限界以下（０．１ｐｐｍ以下）であった。そして、１Ｌ／ｍｉｎでＡｒガスを供給しながら、マイクロウェーブにて、２４５０ＭＨｚ、１２０〜１３０Ｗとして、８７℃で１００分間還元処理を行い、白金粒子からなる白金コロイドを形成した。 Example 1: A platinum salt solution was prepared by adding 6.62 g (Pt content: 300 mg) of dinitrodiammine platinum having a Pt concentration of 4.53 wt% to 300 mL of water. The platinum salt solution was adjusted to pH 7.56 by adding 1% sodium hydroxide, and then adjusted to pH 7.80 by adding 4% sodium bicarbonate. Next, after adding 60 g of ethanol as a reducing agent, bubbling with Ar gas was performed for 10 minutes at a rate of 2 L / min. When the oxygen concentration was measured using a fluorescence oximeter (manufactured by Automatic System Research, FO-960), the oxygen concentration was below the detection limit (0.1 ppm or less). Then, while supplying Ar gas at 1 L / min, a reduction treatment was performed at 87 ° C. for 100 minutes using microwaves at 2450 MHz and 120 to 130 W to form platinum colloids composed of platinum particles.
得られた溶液は、放冷し、３μｍのフィルターによりろ過処理を行い、凝集のないことを確認した。その後、ロータリーエバポレーターを用いて、過剰なエタノールを取り除いた。このときの白金コロイド溶液は、電気伝導度４５７ｍＳ／ｍ、ｐＨ８．３７であった。その後、水酸化ナトリウムを用いて、白金コロイド溶液をｐＨ１１に調整した。調整後の電気伝導度は、４６９ｍＳ／ｍであった。 The obtained solution was allowed to cool and filtered through a 3 μm filter, and it was confirmed that there was no aggregation. Thereafter, excess ethanol was removed using a rotary evaporator. At this time, the platinum colloid solution had an electric conductivity of 457 mS / m and a pH of 8.37. Thereafter, the platinum colloid solution was adjusted to pH 11 using sodium hydroxide. The adjusted electric conductivity was 469 mS / m.
ｐＨ調整後、分画分子量が１００００の限外ろ過膜を用いて、４ｋｇｆ／ｃｍ２の加圧条件で限外ろ過を行った。純水を加えて更に限外ろ過を行った。これを３回繰り返した。３回目の限外ろ過終了後の電気伝導度は、１０ｍＳ／ｍであった。限外ろ過後、水酸化ナトリウムを用いてｐＨ９．５０に調整し白金コロイド溶液を得た。得られた白金コロイド溶液については、以下に示すような安定性の評価を行った。尚、この時の白金コロイド溶液は、質量１３．２ｇ、Ｐｔ濃度１２１４０ｐｐｍ、ｐＨ９．５０、電気伝導度２３ｍＳ／ｍであった。 After pH adjustment, ultrafiltration was carried out under pressure conditions of 4 kgf / cm 2 using an ultrafiltration membrane with a molecular weight cut off of 10,000. Ultrafiltration was further performed by adding pure water. This was repeated three times. The electric conductivity after completion of the third ultrafiltration was 10 mS / m. After ultrafiltration, the pH was adjusted to 9.50 using sodium hydroxide to obtain a platinum colloid solution. The obtained platinum colloid solution was evaluated for stability as shown below. At this time, the platinum colloid solution had a mass of 13.2 g, a Pt concentration of 12140 ppm, a pH of 9.50, and an electric conductivity of 23 mS / m.
実施例２〜７：表１に示すようにｐＨや電気電導度等の製造条件を変化させて得られた白金コロイド溶液について、実施例１と同様に安定性の評価を行った。実施例７は、８６℃で４時間、加熱還流させることにより還元反応させた。また、これらの実施例では、限外ろ過後に添加する純水量を調整して種々の粒子濃度のコロイド溶液とした。 Examples 2 to 7: As shown in Table 1, the stability of the platinum colloid solution obtained by changing the production conditions such as pH and electric conductivity was evaluated in the same manner as in Example 1. In Example 7, the reduction reaction was carried out by heating to reflux at 86 ° C. for 4 hours. In these examples, the amount of pure water added after ultrafiltration was adjusted to obtain colloidal solutions having various particle concentrations.
比較例１〜６：比較例１、２は、還元処理前のｐＨを６．５０と、９．３０に調整し、比較例５では、Ａｒのバブリングを行わなかった。比較例２、６は、還元工程後にｐＨを１２．３と、５．９３に調整し、比較例４は、電気伝導度を３０７ｍＳ／ｍに調整した。また、比較例３については、還元処理後の限外ろ過において、白金粒子濃度を２１０００ｐｐｍまで濃縮して得られた白金コロイド溶液について、安定性の評価を行った。 Comparative Examples 1 to 6: In Comparative Examples 1 and 2, the pH before the reduction treatment was adjusted to 6.50 and 9.30. In Comparative Example 5, no bubbling of Ar was performed. In Comparative Examples 2 and 6, the pH was adjusted to 12.3 and 5.93 after the reduction step, and in Comparative Example 4, the electrical conductivity was adjusted to 307 mS / m. For Comparative Example 3, the stability of the platinum colloid solution obtained by concentrating the platinum particle concentration to 21000 ppm in the ultrafiltration after the reduction treatment was evaluated.
[安定性の評価]
得られた白金コロイド溶液は、室温において、保存容器を密封した状態で静置して安定性の評価を行った。白金コロイド製造直後の数日間は、２４時間ごとにｐＨを測定し、この測定をｐＨが安定するまで行った。また、得られた白金コロイド溶液は、凝集や沈殿が発生するまで評価を行った。安定性の評価は、最大で１ヶ月行った。
[Stability evaluation]
The obtained colloidal platinum solution was allowed to stand at room temperature with the storage container sealed, and the stability was evaluated. For several days immediately after the production of platinum colloid, the pH was measured every 24 hours, and this measurement was performed until the pH was stabilized. The obtained platinum colloid solution was evaluated until aggregation and precipitation occurred. The stability evaluation was conducted for a maximum of one month.
以上より、実施例１〜７のように、白金含有量が３００〜２００００ｐｐｍ、ｐＨ５．０〜１２．０、電気伝導度１００ｍＳ／ｍ以下である白金コロイド溶液は、１ヶ月以上、凝集や沈殿を生じない白金コロイド溶液となった。一方、比較例１〜６のように、上記いずれかの条件を満たさない場合には、凝集や沈殿を生じてしまい、長期間保存をすることができなかった。 From the above, as in Examples 1 to 7, a platinum colloid solution having a platinum content of 300 to 20000 ppm, pH 5.0 to 12.0, and electrical conductivity of 100 mS / m or less is aggregated or precipitated for one month or more. A platinum colloidal solution that did not occur was obtained. On the other hand, as in Comparative Examples 1 to 6, when any of the above conditions was not satisfied, aggregation or precipitation occurred, and the product could not be stored for a long time.
また、実施例１〜７のように、白金塩溶液をｐＨ７．０〜８．５、溶存酸素濃度１．０ｐｐｍ以下とした後に還元処理を行い、得られた白金コロイド溶液をｐＨ７．０〜１２．０、電気伝導度１００ｍＳ／ｍ以下とした場合、１ヶ月以上、凝集や沈殿を生じない白金コロイド溶液を得ることができた。一方、比較例１〜６のように、いずれかの条件を満たさない場合には、得られた白金コロイド溶液を保存すると凝集や沈殿を生じるものとなった。 Further, as in Examples 1 to 7, the platinum salt solution was adjusted to pH 7.0 to 8.5 and the dissolved oxygen concentration was adjusted to 1.0 ppm or less, followed by reduction treatment, and the resulting platinum colloid solution was adjusted to pH 7.0 to 12 When the electric conductivity was set to 0.0 or less and 100 mS / m or less, a platinum colloid solution that did not cause aggregation or precipitation was obtained for one month or more. On the other hand, when one of the conditions was not satisfied as in Comparative Examples 1 to 6, when the obtained platinum colloid solution was stored, aggregation or precipitation occurred.
[抗酸化性試験]
上記により得られた実施例２の白金コロイド溶液について、超純水で希釈し約２００ｐｐｍに調整後、ヒドロキシルラジカル消去活性の評価を行った。比較として、ポリビニルピロリドン（ＰＶＰ）を保護剤として含む白金コロイド溶液（従来例１）、及びポリアクリル酸（ＰＡＡ）を保護剤として含む白金コロイド溶液（従来例２）についても、同様の活性測定を行った。
[Antioxidation test]
The platinum colloid solution of Example 2 obtained above was diluted with ultrapure water and adjusted to about 200 ppm, and then the hydroxyl radical scavenging activity was evaluated. As a comparison, the same activity measurement was performed for a platinum colloid solution (conventional example 1) containing polyvinylpyrrolidone (PVP) as a protective agent and a platinum colloid solution (conventional example 2) containing polyacrylic acid (PAA) as a protective agent. went.
ヒドロキシルラジカル消去活性：
ＤＭＰＯを用いたスピントラッピング法により、過酸化水素−Ｆｅ２＋系で発生させたヒドロキシルラジカルを捕捉して、白金コロイド溶液による消去活性を測定した。活性は、マンニトールの相当量で表す。
Hydroxyl radical scavenging activity :
Hydroxyl radicals generated in the hydrogen peroxide-Fe 2+ system were captured by spin trapping using DMPO, and the erasing activity with a platinum colloid solution was measured. Activity is expressed as a substantial amount of mannitol.
以上より、実施例２の白金コロイド溶液の抗酸化活性は、低濃度のコロイド溶液であっても、従来例１、２の保護剤を用いた白金コロイド溶液より高い抗酸化活性を有することが分かった。 From the above, it can be seen that the antioxidative activity of the colloidal platinum solution of Example 2 is higher than that of the colloidal platinum solution using the protective agent of Conventional Examples 1 and 2 even in the case of a low concentration colloidal solution. It was.
Claims (4)
還元工程前に、白金塩溶液のｐＨを７．０〜８．５に調整し、不活性ガスのバブリングにより溶存酸素濃度を１．０ｐｐｍ以下に調整する工程を有し、
還元工程後、得られた白金コロイド溶液を、限外ろ過により電気伝導度１００ｍＳ／ｍ以下、白金含有量３００〜２００００ｐｐｍの範囲内とし、ｐＨを７．０〜１２．０に調整する工程を有する白金コロイド溶液の製造方法。 A method for producing a platinum colloid solution comprising a reduction step of reducing platinum ions in the platinum salt solution by forming a platinum colloid composed of platinum particles by adding a reducing agent to the platinum salt solution,
Before the reduction step, the step of adjusting the pH of the platinum salt solution to 7.0 to 8.5 and adjusting the dissolved oxygen concentration to 1.0 ppm or less by bubbling with an inert gas,
After the reduction step, the obtained platinum colloidal solution is subjected to ultrafiltration to have an electric conductivity of 100 mS / m or less, a platinum content of 300 to 20000 ppm, and a pH of 7.0 to 12.0. A method for producing a colloidal platinum solution.
The method for producing a platinum colloid solution according to any one of claims 1 to 3 , wherein the pH adjustment after the reduction treatment is performed with sodium hydroxide.
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