於本說明書中，所謂「基於單體之單元」係藉由單體1分子進行聚合而直接形成之原子團、與藉由使該原子團之一部分進行化學轉換而獲得之原子團之總稱。再者，以下，基於單體之單元亦簡稱為「單元」。 含氟聚合物所具有之各單元之含量(莫耳%)可藉由核磁共振譜法分析含氟聚合物而求出，亦可根據各單體之添加量進行推算。 所謂「交聯性基」意指藉由與硬化劑進行反應而可形成交聯結構之基、或交聯性基彼此進行反應而可形成交聯結構之基。 於本說明書中，數量平均分子量及質量平均分子量係藉由凝膠滲透層析(GPC)法，以聚苯乙烯換算而求出之值。數量平均分子量亦記作Mn。 所謂「水滑石」意指下式所表示之層狀雙金屬氫氧化物。其中，x為0.2〜0.33，m為0〜2。 所謂「(甲基)丙烯酸酯」係丙烯酸酯與甲基丙烯酸酯之總稱。 所謂「醚酯系溶劑」意指分子內具有醚鍵與酯鍵之兩者之化合物。 以下，對本發明之含氟樹脂之溶液、含氟樹脂之溶液之製造方法、塗料組合物及塗裝物品進行詳細說明。 [含氟樹脂之溶液] 本發明之含氟樹脂之溶液含有：包含具有基於氯三氟乙烯(CF2
=CFCl，以下亦稱為「CTFE」)之單元之含氟聚合物之氟樹脂、含胺基之化合物及有機溶劑，且藉由以下之氯離子濃度測定法所求出之氯離子濃度為50質量ppm以下。 氯離子濃度測定法：將上述含氟樹脂之溶液與二甲苯加以混合而製備試樣溶液，將所獲得之試樣溶液與水混合後，相分離為二甲苯相與水相，將水相進行回收並藉由離子層析法對回收之水中之氯離子濃度進行測定。 再者，以下亦將上述氯離子濃度測定法稱為「特定之測定法」，所謂氯離子濃度意指藉由特定之測定法所求出之氯離子濃度。 本發明之含氟樹脂之溶液之儲藏穩定性優異，可形成剛成膜後之光澤性優異之塗膜。其詳細原因尚未明確，但認為大致係基於以下原因。 於本發明中，使用包含具有基於CTFE之單元之含氟聚合物之氟樹脂。 發明者等人依照專利文獻1所具體記載之方法，使用含有具有基於CTFE之單元之含氟聚合物的含氟樹脂之溶液製造塗料組合物，並對使用該塗料組合物而獲得之塗膜研究光澤性(參照下文所述之比較例1)。其結果，本發明者等人發現塗膜之剛成膜後之光澤性降低。 然後，本發明者等人發現，含氟樹脂之溶液之氯離子濃度與剛成膜後之塗膜光澤性之降低密切相關。具體而言，本發明者等人發現，亦如下文所述之實施例所示，若將氯離子濃度設為特定值以下，則可獲得剛成膜後之光澤性優異之塗膜。 再者，氯離子與塗膜之光澤性相關之詳細之原因尚不明確，認為基於如下原因等導致光澤性變差：於形成塗膜時，源自酸之成分(源自氯化氫之氯離子等)局部存在於塗膜表面而於塗膜表面與塗膜內部產生硬化速度之差；或於烘烤塗裝時之成膜前氟樹脂凝膠化而熔融流動性變差，未形成均勻之塗膜。 再者，所謂「剛成膜後」係指自塗膜之製作起24小時以內。 又，由於本發明之含氟樹脂之溶液含有含胺基之化合物，因此推測氟樹脂可穩定存在於溶液中。其結果，認為含氟樹脂之溶液之經時性之增黏等受到抑制，含氟樹脂之溶液之儲藏穩定性優異。 再者，專利文獻1中揭示有使用含胺基之化合物及水滑石製造含有具有基於CTFE之單元之含氟聚合物之含氟樹脂之溶液的具體態樣，但本發明者等人發現該態樣中之氯離子濃度較高。其原因未必明確，但認為如以下所述。 首先，認為該含氟樹脂之溶液所含之氯離子主要由CTFE聚合時發生之CTFE之分解所產生。 於此種存在氯離子之情況下，若存在含胺基之化合物，則於含胺基之化合物與氯離子之間形成鹽酸鹽。又，於此種情況下若存在水滑石，則氯離子亦被水滑石所吸附。即，於專利文獻1之具體態樣中，進行氯離子與含胺基之化合物形成鹽及氯離子向水滑石吸附這兩者。 水滑石於聚合後藉由過濾處理等自含氟聚合物分離。因此，被水滑石吸附之氯離子被去除至系統外。另一方面，與含胺基之化合物形成鹽之氯離子依然殘存於系統內。即，含氟樹脂之溶液所含之氯離子之量受到含胺基之化合物與水滑石之使用量所影響。具體而言，本發明者等人發現，於含胺基之化合物之使用量多於水滑石之使用量之情形時，與含胺基之化合物形成鹽之氯離子大量殘存於系統內，結果其氯離子濃度變高，因此無法獲得所需之效果。 於本發明中，如下文所詳細說明般，於製造含氟樹脂之溶液時，將水滑石之使用質量相對於含胺基之化合物之使用質量設為特定比率，對氯離子之系統外去除量與系統內殘存量進行控制，因此認為可降低含氟樹脂之溶液之氯離子濃度，結果可獲得所需之效果。 本發明中之含氟聚合物具有基於CTFE之單元，較佳為進而具有上述單元以外之單元(以下亦稱為其他單元)。 其他單元較佳為基於CTFE以外之氟烯烴之單元、基於具有交聯性基之單體(以下亦稱為「單體1」)之單元、或基於不具有氟原子及交聯性基之單體(以下亦稱為「單體2」)之單元，更佳為基於單體1之單元或基於單體2之單元。尤佳為含氟聚合物具有基於單體1之單元與基於單體2之單元兩者。 CTFE以外之氟烯烴所具有之氟原子數較佳為2以上，更佳為2〜6，進而較佳為3〜4。若該氟原子數為2以上，則所獲得之塗膜之耐候性優異。 CTFE以外之氟烯烴較佳為CF2
=CF2
、CH2
=CF2
、或CH2
=CFCF3
，尤佳為CF2
=CF2
。 CTFE以外之氟烯烴亦可使用兩種以上。 單體1係具有交聯性基之單體。 交聯性基較佳為具有活性氫之官能基(羥基、羧基、胺基等)、或水解性矽烷基(烷氧基矽烷基等)、環氧基或氧雜環丁基。 單體1較佳為式CH2
=CX1
(CH2
)n1
-Q1
-R1
-Y1
所表示之單體。其中，式中，X1
為氫原子或甲基，n1為0或1，Q1
為單鍵、醚性氧原子、-C(O)O-或-O(O)C-，R1
為碳數2〜20之伸烷基、碳數2〜20之含有醚性氧原子之伸烷基、或具有環結構之碳數6〜20之伸烷基，Y1
為交聯性基。 X1
較佳為氫原子。 n1較佳為0。 Q1
較佳為氧原子或-O(O)O-，較佳為氧原子。 R1
較佳為直鏈狀之碳數1〜10之伸烷基。該伸烷基之碳數更佳為1〜6，進而較佳為2〜4。 Y1
較佳為水解性矽烷基、羥基、羧基或胺基，更佳為羥基、羧基或胺基，進而較佳為羥基。 作為單體1之具體例，可列舉：羥基烷基乙烯基醚(2-羥基乙基乙烯基醚、羥基甲基乙烯基醚、4-羥基丁基乙烯基醚等)、羥基烷基乙烯基酯、羥基烷基烯丙基醚(羥基乙基烯丙基醚等)、羥基烷基烯丙基酯、(甲基)丙烯酸羥基烷基酯((甲基)丙烯酸羥基乙酯等)等。較佳為羥基烷基乙烯基酯、羥基烷基烯丙基酯中之羥基烷基及羥基烯丙基分別與酯鍵之羰基之碳原子鍵結。 單體1較佳為羥基烷基乙烯基醚、或羥基烷基烯丙基醚，就共聚性優異、所形成之塗膜之耐候性優異之方面而言，更佳為羥基烷基乙烯基醚，尤佳為4-羥基丁基乙烯基醚。 單體1亦可使用兩種以上。 單體2係不具有氟原子及交聯性基之單體。 作為單體2，較佳為式CH2
=CX2
(CH2
)n2
-Q2
-R2
所表示之單體。其中，式中，X2
為氫原子或甲基，n2為0或1，Q2
為單鍵、氧原子、-C(O)O-或-O(O)C-，R2
為碳數2〜20之烷基、碳數2〜20之含有醚性氧原子之烷基、或具有環結構之碳數6〜20之烷基。 X2
較佳為氫原子。 n2較佳為0。 Q2
較佳為氧原子或-O(O)C-，較佳為氧原子。 R2
較佳為碳數1〜10之烷基、或具有環結構之碳數6〜20之烷基，更佳為碳數1〜6之烷基、或碳數6〜12之環烷基，尤佳為碳數2〜4之烷基、或碳數6〜10之環烷基。 作為單體2之具體例，可列舉：烷基乙烯基醚、環烷基乙烯基醚、烷基乙烯基酯、烷基烯丙基醚、烷基烯丙基酯、(甲基)丙烯酸烷基酯等。較佳為烷基乙烯基酯及烷基烯丙基酯中之烷基與酯鍵之羰基之碳原子鍵結。 單體2較佳為烷基乙烯基醚、或環烷基乙烯基醚，更佳為乙基乙烯基醚、環己基乙烯基醚、或2-乙基己基乙烯基醚，就氟樹脂之剛性較高、可溶於有機溶劑、於應用於塗料中之情形時容易施工、可獲得較硬之塗膜之方面而言，尤佳為環己基乙烯基醚。 單體2亦可使用兩種以上。 含氟聚合物中之基於CTFE之單元之比率相對於含氟聚合物所具有之全部單元，較佳為40〜60莫耳%，更佳為45〜55莫耳%。若該比率為40莫耳%以上，則所獲得之塗膜之耐候性優異。若該比率為60莫耳%以下，則於有機溶劑或稀釋劑中之溶解性優異。 於含氟聚合物具有基於單體1之單元及基於單體2之單元之情形時，其合計之比率相對於含氟聚合物所具有之全部單元，較佳為40〜60莫耳%，更佳為45〜55莫耳%。 因此，於基於CTFE之單元以外之單元僅為基於單體1之單元及基於單體2之單元之情形時，基於單體1之單元及基於單體2之單元之合計之比率相對於含氟聚合物所具有之全部單元，較佳為40〜60莫耳%，更佳為45〜55莫耳%。 具有基於單體1之單元之情形時之比率相對於含氟聚合物所具有之全部單元，較佳為5〜40莫耳%，更佳為8〜35莫耳%。若該比率為5莫耳%以上，則為了獲得硬度較高之塗膜所充分之量之交聯性基被導入至含氟聚合物中。若該比率為40莫耳%以下，則即便為高固形物成分型，亦可維持作為含氟樹脂之溶液所充分之低黏度。 具有基於單體2之單元之情形時之比率相對於含氟聚合物所具有之全部單元，較佳為超過0莫耳%且為45莫耳%以下，更佳為3〜45莫耳%，進而較佳為20〜45莫耳%。若具有該單元，則可適當調整所獲得之塗膜之硬度或柔軟性。若上述比率為45莫耳%以下，則容易於含氟聚合物中導入為了獲得耐候性優異、硬度較高之塗膜所充分之量之交聯性基。 於具有基於CTFE之單元、基於單體1之單元及基於單體2之單元以外之基於單體之單元之情形時，該單元之比率相對於含氟聚合物所具有之全部單元，較佳為20莫耳%以下，更佳為10莫耳%以下。 含氟聚合物之Mn較佳為3,000〜50,000，更佳為5,000〜30,000。若含氟聚合物之Mn為上述下限值以上，則塗膜之耐水性、耐鹽水性等優異。若含氟聚合物之Mn為上述上限值以下，則塗膜之表面平滑性優異。 再者，於本發明之含氟樹脂之溶液中實質上不含水滑石。所謂實質上不含水滑石意指本發明之含氟脂之溶液所含之水滑石量未達0.1質量%，通常較佳為0.01質量%以下。水滑石量之下限為0質量%。 本發明中之含胺基之化合物只要為含有胺基之化合物，則並無特別限定。再者，於本說明書中，上述「含胺基之化合物」中亦包括與氯化氫(HCl)形成鹽之態樣。即，上述「含胺基之化合物」中亦包括含胺基之化合物之鹽酸鹽。 作為胺基，可列舉：一級胺基(-NH2
)、二級胺基、三級胺基。 二級胺基係式-NHRN
(RN
為一價取代基)所表示之單取代胺基，作為RN
之具體例，可列舉：烷基、芳基、乙醯基、苯甲醯基、苯磺醯基、第三丁氧基羰基等。作為二級胺基之具體例，可列舉：甲基胺基、乙基胺基、丙基胺基、異丙基胺基等R為烷基之二級胺基；或苯基胺基、萘基胺基等R為芳基之二級胺基等。又，RN
中氫原子亦可進一步經乙醯基、苯甲醯基、苯磺醯基、第三丁氧基羰基等所取代。 三級胺基為式-NRN1
RN2
(RN1
及RN2
為一價取代基)所表示之二取代胺基，作為RN1
及RN2
之具體例，與RN
相同。作為三級胺基之具體例，可列舉：二甲胺基、二乙胺基、二丁胺基、乙基甲基胺基、二苯基胺基、甲基苯基胺基等。 作為胺基，亦可列舉脂環式胺基。脂環式胺基係環內至少含有1個氮原子之脂環基。 作為脂環式胺基，較佳為吡咯啶基、哌啶基、哌𠯤基、氮雜環庚烷基等5〜7員環之脂環式胺基，尤佳為6員環之脂環式胺基(哌啶基)。又，脂環式胺基中之氫原子可進一步經取代基(烷基、芳基等)所取代。 6員環之脂環式胺基較佳為哌啶基或具有取代基之哌啶基，更佳為具有取代基之哌啶基，進而較佳為四取代哌啶基，尤佳為2,2,6,6-四取代哌啶基。 含胺基之化合物亦可使用兩種以上。 含胺基之化合物較佳為下式所表示之化合物(具有2,2,6,6-四取代哌啶基之化合物)。 [化1]R11
〜R14
分別獨立為碳數1〜18之烷基(甲基、乙基、丙基、十二烷基、硬脂基等)、環烷基(環戊基、環己基等)、取代烷基(2-羥基乙基、2-甲氧基羰基乙基、3-羥基丙基等)、芳基(苯基、萘基等)或芳烷基(苯乙基、苄基等)，R11
及R12
、或R13
及R14
可形成碳數3〜6之脂肪族環。作為R11
〜R14
，就價格、獲得容易性之方面而言，較佳為碳數1〜18之烷基，尤佳為甲基。 R15
為氫原子、烷基(甲基、乙基、丙基、丁基、十二烷基、硬脂基等)、取代烷基(2-羥基乙基、2-甲氧基羰基乙基、2-乙醯氧基乙基、2-(3-甲氧基羰基丙醯氧基)乙基、3-羥基丙基等)、芳基(苯基、萘基、羥基苯基等)、芳烷基(苯乙基、苄基、羥基苯基烷基等)或環烷基(環己基等)。 R16
為氫原子、羥基、烷基(甲基、乙基、丙基、丁基、十二烷基、硬脂基等)、取代烷基(2-羥基乙基、2-甲氧基羰基乙基、2-乙醯氧基乙基、2-(3-甲氧基羰基丙醯氧基)乙基、3-羥基丙基等)、芳基(苯基、萘基等)、芳烷基(苯乙基、苄基等)、含酯鍵之基(乙醯氧基、丙醯氧基、丁醯氧基、月桂醯氧基、取代烷基羰氧基、苯甲醯氧基、取代苯甲醯氧基等)、含胺基之基(烷氧基羰基胺基、N-單烷基胺甲醯基胺基、N,N-二烷基胺甲醯基胺基等)或含2,2,6,6-四取代哌啶基之基。R16
可組合該等基兩種以上。 作為含胺基之化合物之具體例，可列舉：2,2,6,6-四甲基哌啶、1,2,2,6,6-五甲基哌啶、4-羥基-2,2,6,6-四甲基哌啶、4-羥基-1,2,2,6,6-五甲基哌啶、1-乙基-2,2,6,6-四甲基哌啶、1-乙基-4-羥基-2,2,6,6-四甲基哌啶、1-丁基-4-羥基-2,2,6,6-四甲基哌啶、1-十二烷基-2,2,6,6-四甲基哌啶、1-苯基-2,2,6,6-四甲基哌啶、1-(2-羥基乙基)-2,2,6,6-四甲基哌啶、1-(6-羥基乙基)-4-羥基-2,2,6,6-四甲基哌啶、4-乙醯氧基-2,2,6,6-四甲基哌啶、4-乙醯氧基-1,2,2,6,6-五甲基哌啶、1-(2-乙醯氧基乙基)-4-乙醯氧基-2,2,6,6-四甲基哌啶、1-(2-苯甲醯氧基乙基)-4-苯甲醯氧基-2,2,6,6-四甲基哌啶、4-乙基-2,2,6,6-四甲基哌啶、4-乙基-1,2,2,6,6-五甲基哌啶、4-丁基-2,2,6,6-四甲基哌啶、4-辛基-2,2,6,6-四甲基哌啶、4-十二烷基-2,2,6,6-四甲基哌啶、4-硬脂基-2,2,6,6-四甲基哌啶、4-硬脂基-1,2,2,6,6-五甲基哌啶、癸二酸甲酯1,2,2,6,6-五甲基-4-哌啶酯、癸二酸雙(2,2,6,6-四甲基-4-哌啶基)酯等。 作為R16
為含2,2,6,6-四取代哌啶基之基之含胺基之化合物，可列舉使具有羥基之2,2,6,6-四甲基哌啶(4-羥基-2,2,6,6-四甲基哌啶、4-羥基-1,2,2,6,6-五甲基哌啶、1-(2-羥基乙基)-4-羥基-2,2,6,6-四甲基哌啶、1-(2-羥基乙基)-2,2,6,6-四甲基哌啶等)與多元酸(琥珀酸、己二酸、癸二酸、壬二酸、癸烷-1,10-二羧酸、鄰苯二甲酸、間苯二甲酸、對苯二甲酸、偏苯三甲酸、丙二酸、取代丙二酸等)進行反應而獲得之1分子中含有2個以上之2,2,6,6-四甲基哌啶基之含胺基之化合物，具體而言，可列舉下式所表示之化合物。 其中，n3為1〜20之整數。 [化2]含胺基之化合物之含量相對於上述氟樹脂100質量份，較佳為0.1〜2.0質量份，更佳為0.5〜2.0質量份，進而較佳為0.5〜1.5質量份。若該含量為0.1質量份以上，則於單體成分之聚合中或聚合後，含氟樹脂之溶液變得更不易凝膠化，含氟樹脂之溶液之儲藏穩定性更優異。又，若該含量為2.0質量份以下，則含氟樹脂之溶液於儲藏中之溶液之變色(例如黃變或白濁等)或含氟聚合物之分子量之增大進一步受到抑制，含氟樹脂之溶液之儲藏穩定性更優異。 本發明中之有機溶劑只要為可溶解氟樹脂之有機溶劑，則並無特別限定，較佳為選自由芳香族烴系溶劑、酮系溶劑、酯系溶劑、醇系溶劑、醚酯系溶劑所組成之群之一種以上之有機溶劑。 芳香族烴系溶劑較佳為甲苯、二甲苯、乙基苯、芳香族石腦油、萘滿、或松節油。芳香族烴系溶劑可使用市售品，可使用Solvesso(註冊商標)#100(Exxon Chemical公司製造)、Solvesso(註冊商標)#150(Exxon Chemical公司製造)等。 酮系溶劑較佳為丙酮、甲基乙基酮、甲基戊基酮、甲基異丁基酮、乙基異丁基酮、二異丁基酮、環己酮、或異佛酮。 酯系溶劑較佳為乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸異丁酯、或乙酸第三丁酯。 醇系溶劑較佳為碳數4以下之醇，較佳為乙醇、第三丁醇、或異丙醇。 醚酯系溶劑較佳為3-乙氧基丙酸乙酯、丙二醇單甲醚乙酸酯、或乙酸甲氧基丁酯。 有機溶劑亦可使用兩種以上。又，有機溶劑可為與用作聚合溶劑之有機溶劑相同之有機溶劑，亦可為與之不同之有機溶劑。 有機溶劑之含量就氟樹脂之溶解性變得良好之觀點而言，較佳為以含氟樹脂之溶液中之固形物成分濃度成為40〜80質量%之方式含有。 本發明之含氟樹脂之溶液亦可於可充分發揮本發明之效果之範圍內含有上述以外之成分(例如，丙烯酸系樹脂或聚酯樹脂等通用樹脂成分)。 本發明之含氟樹脂之溶液藉由特定之測定法所求出之氯離子濃度為50質量ppm以下。氯離子濃度更佳為40質量ppm以下，進而較佳為30質量ppm以下，尤佳為10質量ppm以下。下限值較佳為1質量ppm，尤佳為3質量ppm。 若氯離子濃度為50質量ppm以下，則使用本發明之含氟樹脂之溶液所獲得之塗膜剛成膜後之光澤性優異。另一方面，若上述氯離子濃度超過50質量ppm，則剛成膜後之光澤性變得不充分。 尤其是若氯離子濃度為3〜30質量ppm，則使用含氟樹脂之溶液所獲得之塗料組合物之流動性亦優異。若使用含氟樹脂之溶液所獲得之塗料組合物之流動性優異，則於將塗裝於基材之粉體組合物熔融而形成塗膜(硬化膜)時，塗料組合物之流動性提高，因此就可獲得平滑且均勻之塗膜(硬化膜)之方面而言較佳。 若氯離子濃度為30質量ppm以下，則可抑制由含氟樹脂之溶液之粉體化(脫溶劑)或烘烤塗裝時之熱引起之氯化氫之產生。推測藉此塗料組合物所含之氟樹脂之凝膠化受到抑制，塗料組合物之流動性提高。 於本發明中，氯離子濃度係藉由特定之測定法測定，即，將本發明之含氟樹脂之溶液與二甲苯加以混合而製備試樣溶液，將所獲得之試樣溶液與水混合後，相分離為二甲苯相與水相，將水相進行回收並藉由離子層析法對回收之水中之氯離子濃度進行測定。 更詳細而言，氯離子濃度係以如下方式進行測定。 首先，將本發明之含氟樹脂之溶液與二甲苯進行混合及攪拌而獲得試樣溶液。再者，含氟樹脂之溶液之量相對於二甲苯之量5 mL設為0.5 g。 繼而，將試樣溶液與純水進行混合及攪拌而獲得混合液。再者，純水之量相對於試樣溶液之添加量4.9 g設為3 mL。 繼而，將混合液進行離心分離而將混合液相分離為水相與二甲苯相，去除二甲苯相而獲得分離液。進而，將分離液進行離心分離而使其相分離為殘留二甲苯(二甲苯相)與水(水相)，去除二甲苯相，將水相回收。 繼而，製備於所回收之水(水相)中添加純水稀釋而成之測定液，藉由離子層析法對氯離子濃度進行測定。 再者，於任一離心分離中均使用公知之離心分離裝置(具體而言為依照久保田製作所製造之商品名「台式冷卻離心機5500」之裝置)，離心分離之條件設為於12000 rpm下5分鐘。 又，利用離子層析法進行之測定例如係使用依照離子層析儀ICS-1500(商品名，Dionex公司製造)之裝置進行測定。 利用離子層析法測得之氯離子濃度之具體之測定條件如下所述。再者，以相對於濃度已知之標準液之峰面積比測定檢測量，並換算氯離子(Cl-
)之量。又，氯離子(Cl-
)之定量極限為0.6 ppm以下。 ＜離子層析儀條件＞ 裝置：使用Dionex公司製造之ICS-1500抑制器 分析管柱：Dionex IonPac AS14 內徑4.0 mm×長度50 mm 保護管柱：Dionex IonPac AG14 內徑4.0 mm×長度250 mm 溶離液：3.5 mmol Na2
CO3
、1.0 mmol NaHCO3
流量：1.5 ml/min [含氟樹脂之溶液之製造方法] 本發明之含氟樹脂之溶液之製造方法係如下方法：於含胺基之化合物及水滑石之存在下，使包含CTFE之單體成分於有機溶劑中進行聚合而獲得含有含氟聚合物之混合液，繼而自上述含有含氟聚合物之混合液去除源自上述水滑石之不溶解成分而製造含氟樹脂之溶液。 又，於單體成分開始聚合之時間點，水滑石之量相對於含胺基之化合物之量之比率(水滑石之量/含胺基之化合物之量)為1〜4。 進而，藉由特定之測定法所求出之氯離子濃度較佳為50質量ppm以下。 根據本發明之含氟樹脂之溶液之製造方法，可獲得儲藏穩定性優異之含氟樹脂之溶液，可形成剛成膜後之光澤性優異之塗膜。 以下，將進行聚合之步驟稱為聚合步驟、進行過濾之步驟稱為過濾步驟，對各步驟進行詳細說明。 藉由所謂之溶液聚合法使聚合步驟中之單體成分進行聚合。各成分於聚合系統中之添加順序可適當選擇。作為單體成分，除了CTFE以外，亦可使用單體1及單體2。 關於聚合步驟中之含胺基之化合物、CTFE、及氟樹脂之詳細內容如上所述，省略其說明。 作為有機溶劑，可列舉與含氟樹脂之溶液一項所記載之有機溶劑相同之有機溶劑。聚合步驟中之有機溶劑可與本發明之含氟樹脂之溶液所含之有機溶劑相同，亦可與之不同。 聚合步驟中之水滑石就氯離子之吸附性優異之方面及容易獲得之方面而言，較佳為Mg6
Al2
(OH)16
CO3
·4H2
O(於上述之表示水滑石之式中，x＝0.25，m＝0.5)、或Mg4.5
Al2
(OH)13
CO3
·3.5H2
O(於上述之表示水滑石之式中，x＝0.308，m＝0.538)。 水滑石亦可使用兩種以上。 水滑石之粒徑較佳為5〜500 μm，更佳為5〜110 μm。若水滑石之粒徑為5 μm以上，則變得容易利用過濾進行去除。若水滑石之粒徑為500 μm以下，則每單位質量之表面積較大，進一步發揮由水滑石獲得之效果。 水滑石之粒徑係依照JIS K 0069之「化學製品之篩分試驗方法」而測定。 於聚合步驟中，較佳為藉由聚合起始劑之作用使單體成分進行聚合。 作為聚合起始劑，可列舉：偶氮系起始劑(2,2'-偶氮雙異丁腈、2,2'-偶氮雙環己腈、2,2'-偶氮雙(2,4-二甲基戊腈)、2,2'-偶氮雙(2-甲基丁腈)等)、過氧化物系起始劑{過氧化酮(過氧化環己酮等)、過氧化氫(第三丁基過氧化氫等)、過氧化二醯基(過氧化苯甲醯等)、過氧化二烷基(過氧化二第三丁基等)、過氧縮酮(2,2-二-(第三丁基過氧基)丁烷等)、烷基過氧化酯(過氧化特戊酸第三丁酯等)、過氧化碳酸酯(過氧化二碳酸二異丙酯等)}。 於聚合步驟之開始聚合之時間點，水滑石之質量相對於含胺基之化合物之質量(水滑石之質量/含胺基之化合物之質量)之比率為1〜4，較佳為1.0〜3，尤佳為1.0〜2。 若該比率為1以上，則如含氟樹脂之溶液一項所記載，可將氯離子濃度調整為特定範圍，剛成膜後之塗膜之光澤性優異。又，若該比率為4以下，則於過濾步驟中去除不溶解成分時容易抑制過濾材料之堵塞。 含胺基之化合物之量相對於單體成分100質量份，較佳為0.1〜2.0質量份，更佳為0.5〜2.0質量份，進而較佳為0.5〜1.5質量份。若該量為0.1質量份以上，則於單體成分之聚合中或聚合後，含氟樹脂之溶液變得更不易凝膠化，含氟樹脂之溶液之儲藏穩定性更優異。又，若該量為2.0質量份以下，則含氟樹脂之溶液於儲藏中之溶液之變色(例如黃變或白濁等)或氟樹脂之分子量之增大進一步受到抑制，含氟樹脂之溶液之儲藏穩定性更優異。 單體成分中之CTFE之量相對於全部單體成分，較佳為40〜60莫耳%，更佳為45〜55莫耳%。若CTFE之量為40莫耳%以上，則所獲得之塗膜之耐候性優異。若CTFE之量為60莫耳%以下，則於有機溶劑或稀釋劑中之溶解性優異。 於含有單體1及單體2作為單體成分之情形時，其合計量相對於全部單體成分，較佳為40〜60莫耳%，更佳為45〜55莫耳%。 因此，於CTFE以外之單體成分僅為單體1及單體2之情形時，單體1及單體2之合計量相對於全部單體成分，較佳為40〜60莫耳%，更佳為45〜55莫耳%。 單體成分中之單體1之量相對於全部單體成分，較佳為5〜40莫耳%，更佳為8〜35莫耳%。若該量為5莫耳%以上，則為了獲得硬度較高之塗膜所充分之量之交聯性基被導入至含氟聚合物。若該量為40莫耳%以下，則即便為高固形物成分型，亦可作為含氟樹脂之溶液而維持低黏度。 單體成分中之單體2之量相對於全部單體成分，較佳為超過0莫耳%且為45莫耳%以下，更佳為3〜45莫耳%，進而較佳為20〜45莫耳%。若使用單體2，則可適當調整所獲得之塗膜之硬度或柔軟性。若該量為45莫耳%以下，則容易於含氟聚合物中導入為了獲得耐候性優異、硬度較高之塗膜所充分之量之交聯性基。 於含有CTFE、單體1及單體2以外之單體的單體成分之情形時，該單體之量相對於全部單體成分，較佳為20莫耳%以下，更佳為10莫耳%以下。 於本發明中之過濾步驟中，將作為不溶於有機溶劑之不溶解成分之吸附有聚合步驟中產生之氯離子的水滑石(即源自水滑石之不溶解成分)去除。去除係藉由過濾等固液分離處理進行。 藉由以上之本發明之製造方法所獲得之含氟樹脂之溶液較佳為藉由特定之測定法測得之氯離子濃度為50質量ppm以下。關於氯離子濃度之更佳之範圍及效果，如含氟樹脂之溶液一項所說明，因此省略其說明。 又，藉由本發明之製造方法而獲得之含氟樹脂之溶液較佳為實質上不含水滑石。所謂實質上不含水滑石意指含氟脂之溶液所含之水滑石量未達0.1質量%，通常較佳為0.01質量%以下。水滑石量之下限為0質量%。 於本發明之製造方法中，亦可於聚合步驟後且過濾步驟前於含有含氟聚合物之混合液中添加水滑石。進而，於添加水滑石後且過濾步驟前亦可進行攪拌處理。藉此，可進一步降低上述氯離子濃度，所獲得之塗膜之剛成膜後之光澤性更優異。又，亦有含氟樹脂之溶液之儲藏穩定性更優異之傾向。 所添加之水滑石之量相對於所產生之含氟聚合物100質量份，較佳為0.1〜3.0質量份，更佳為0.5〜2.0質量份。若該量處於上述範圍內，則進一步表現上述之效果。 [塗料組合物] 本發明之塗料組合物係使用本發明之含氟樹脂之溶液而獲得之塗料組合物。本發明之塗料組合物可為液狀，亦可為粉末狀(所謂之粉體塗料組合物)。 液狀之塗料組合物係含有上述之含氟樹脂之溶液之塗料組合物，較佳為除了含氟樹脂之溶液以外亦含有硬化劑。 作為硬化劑，可列舉：異氰酸酯系硬化劑、封端化異氰酸酯系硬化劑、或胺基樹脂。 異氰酸酯系硬化劑較佳為無黃變異氰酸酯(例如，六亞甲基二異氰酸酯、異佛酮二異氰酸酯等)。 封端化異氰酸酯系硬化劑較佳為藉由己內醯胺、異佛酮、β-二酮等將異氰酸酯系硬化劑之異氰酸基進行封端而成之硬化劑。 胺基樹脂係胺(三聚氰胺、三聚氰二胺、脲等)與醛(甲醛等)之反應產物(羥甲基三聚氰胺等)或其衍生物(烷基醚化羥甲基三聚氰胺等)。作為胺基樹脂，可列舉：三聚氰胺樹脂、三聚氰二胺樹脂、脲樹脂、磺醯胺樹脂、苯胺樹脂等。 硬化劑之含量相對於塗料組合物中之氟樹脂100質量份，較佳為1〜100質量份，更佳為1〜50質量份。若硬化劑為1質量份以上，則塗膜之耐溶劑性與硬度優異。若為100質量份以下，則塗膜之加工性與耐衝擊性優異。 液狀之塗料組合物亦可進一步含有上述以外之成分。作為此種成分，可列舉：著色劑、上述之氟樹脂以外之樹脂、矽烷偶合劑、紫外線吸收劑、硬化觸媒等。 又，本發明之塗料組合物亦可為含有自本發明之含氟樹脂之溶液去除上述有機溶劑而成之氟樹脂組合物的塗料組合物。該塗料組合物亦可為使該氟樹脂組合物溶解於溶劑或分散於分散介質而獲得之液狀之塗料組合物。較佳為含有不含上述有機溶劑等液狀介質之氟樹脂組合物之塗料組合物。作為含有不含液狀介質之氟樹脂組合物之塗料組合物，較佳為粉末狀之塗料組合物(所謂之粉體塗料組合物)。 粉末狀之塗料組合物含有自本發明之含氟樹脂之溶液去除上述有機溶劑而製成粉末狀之氟樹脂組合物。粉末狀之氟樹脂組合物可對本發明之含氟樹脂之組合物實施乾燥處理及粉碎處理等公知之處理而製造。 粉末狀之塗料組合物較佳為除了上述氟樹脂組合物以外亦含有硬化劑。關於硬化劑，與上述之液狀之塗料組合物相同，省略說明。 又，粉末狀之塗料組合物可進一步含有上述以外之成分。作為此種成分，與上述之液狀之塗料組合物相同，省略說明。 [塗裝物品] 本發明之塗裝物品具有基材、及藉由上述塗料組合物而形成於上述基材上之塗膜。 作為塗裝方法，例如可列舉：噴塗、空氣噴塗、刷塗、浸漬法、靜電塗裝法、輥塗、流塗等方法。 塗膜亦可為塗裝於基材後實施公知之熔融處理而獲得之膜(熔融膜)。 作為基材之材質，可列舉無機物、有機物、有機無機複合材料等。作為無機物，可列舉混凝土、自然石、玻璃、金屬(鐵、不鏽鋼、鋁、銅、黃銅、鈦等)等。作為有機物，可列舉塑膠、橡膠、接著劑、木材等。作為有機無機複合材料，可列舉纖維強化塑膠、樹脂強化混凝土、纖維強化混凝土等。 基材之形狀、尺寸等並無特別限定。 作為本發明之塗裝物品之用途，可列舉：運輸用機件(汽車、電車、飛機等)、土木構件(橋樑構件、鐵塔等)、產業機件(防水材片材、槽、管等)、建築構件(樓房外裝、門、窗門構件、紀念碑、桿等)、道路構件(道路之中央隔離帶、護軌、隔音壁等)、通信機件、電氣機件、電子機件、太陽電池模組用表面片材、太陽電池模組用背面片材等。 實施例 以下，列舉實施例對本發明進行詳細說明。但本發明並不限定於該等實施例。 下文所述之表中之各成分之調配量表示質量基準。 含氟樹脂之溶液之固形物成分濃度係藉由JIS K 5601-1-2(2009年制定)測定加熱殘餘物而求出。 含氟樹脂之溶液所含之氟樹脂之Mn係藉由GPC(Tosoh公司製造，HLC-8220)進行測定。使用四氫呋喃作為展開溶劑，使用聚苯乙烯作為標準物質。 [含氟樹脂之溶液] 實施例及比較例之各含氟樹脂之溶液係以如下方式製備。 ＜實施例1之含氟樹脂之溶液之製備＞ 於安裝有攪拌機之內容積2500 mL之不鏽鋼製耐壓反應器中添加7.32 g之含胺基之化合物(BASF製造，商品名「TINUVIN292」，癸二酸雙(1,2,2,6,6-五甲基-4-哌啶基)酯與癸二酸甲酯1,2,2,6,6-五甲基-4-哌啶酯之混合物(質量比3：1))、7.32 g之水滑石(協和化學工業公司製造，商品名「KW500」，粒徑：45 μm以下：38%、45〜7 μm：35%、75〜106 μm：21%、106〜500 μm：6%)、746 g之二甲苯、153 g之4-羥基丁基乙烯基醚、601 g之環己基乙烯基醚，藉由利用氮氣進行之脫氣而去除溶液中之溶氧。進而，於上述反應器中導入701 g之CTFE，逐漸升溫，於溫度達到65℃之時間點間歇性地添加4.1 g之過氧化特戊酸第三丁酯(聚合起始劑)，藉此進行聚合。 24小時後，將反應器進行水冷而停止反應。將反應液冷卻至室溫後，清除未反應單體，藉由以矽藻土作為濾材之過濾將所獲得之反應液之不溶解成分去除，進而添加適量二甲苯，獲得固形物成分濃度60.0%之實施例1之含氟樹脂之溶液。 再者，實施例1之含氟樹脂之溶液所含之含氟聚合物之Mn為15500。 ＜實施例2之含氟樹脂之溶液之製備＞ 以與實施例1之含氟樹脂之溶液之製備同樣之方式進行聚合，於所獲得之反應液中進一步添加水滑石KW500，攪拌1小時後，藉由以矽藻土作為濾材之過濾將不溶解成分去除，進而添加適量二甲苯，獲得固形物成分濃度60.0%之實施例2之含氟樹脂之溶液。 再者，實施例2之含氟樹脂之溶液所含之含氟聚合物之Mn為15500。 ＜實施例3〜5及比較例1之含氟樹脂之溶液之製備＞ 將聚合時所添加之含胺基之化合物及水滑石之至少一者之添加量變更為第1表所記載之量，除此以外，進行與實施例1之含氟樹脂之溶液之製備同樣之操作，獲得實施例3〜5及比較例1之含氟之樹脂溶液。 再者，實施例3〜5及比較例1之含氟樹脂之溶液所含之含氟聚合物之Mn分別為15100、14900、14800、15400。 ＜實施例6〜7＞ 將聚合時所添加之含胺基之化合物由TINUVIN292變更為TINUVIN770DF(商品名，BASF製造，癸二酸雙(2,2,6,6-四甲基-4-哌啶基)酯)或二乙醇胺，將含胺基之化合物及水滑石之添加量設為第1表所記載之量，除此以外，進行與實施例1之含氟之溶液之製備同樣之操作，獲得實施例6〜7之含氟之樹脂溶液。 再者，實施例6〜7之含氟樹脂之溶液所含之含氟聚合物之Mn分別為15000、14900。又，以上之各例中獲得之含氟樹脂之溶液中之水滑石之含量為0.01質量%以下。 ＜比較例2之含氟樹脂之溶液之製備＞ 於聚合時不添加含胺基之化合物，除此以外，進行與實施例1之含氟樹脂之溶液之製備同樣之操作，獲得比較例2之含氟樹脂之溶液。 再者，比較例2之含氟樹脂之溶液所含之含氟聚合物之Mn為16400。 ＜比較例3之含氟樹脂之溶液之製備＞ 將聚合時所添加之含胺基之化合物之添加量變更為第1表所記載之量，於聚合時不添加水滑石，除此以外，進行與實施例2之含氟樹脂之溶液之製備同樣之操作，獲得比較例3之含氟樹脂之溶液。 再者，比較例3之含氟樹脂之溶液所含之含氟聚合物之Mn為15600。 ＜氯離子濃度＞ 藉由以下程序測定各含氟樹脂之溶液之氯離子濃度。 將各含氟樹脂之溶液0.5 g與二甲苯5 mL裝入至PP(聚丙烯)管中，用手振盪1分鐘而獲得含氟樹脂之溶液被二甲苯完全溶解而成之試樣溶液。 繼而，於試樣溶液中添加純水3 mL，用手劇烈振盪而獲得混合液。 繼而，將混合液進行離心分離，相分離為水與二甲苯後，使用微量吸管自混合液去除二甲苯相(上層)。 進而，對去除了二甲苯相之混合液進行離心分離，使其分離為殘留二甲苯(二甲苯相)與水(水相)。任一離心分離均使用離心分離裝置(商品名「台式冷卻離心機5500」，久保田公司製造)，於12000 rpm下進行5分鐘。 繼而，準備以純水將分離回收之水(水層)稀釋5倍或10倍而成之測定液，藉由離子層析法對測定液之氯離子濃度進行測定。利用離子層析法進行之測定係使用離子層析儀ICS-3000(商品名，Thermo Fisher公司製造)進行。利用離子層析法之測定條件如以下所述。 具體而言，以相對於濃度已知之標準液之峰面積比測定檢測量，並換算氯離子(Cl-
)之量。再者，定量極限以氯離子(Cl-
)計為0.6 ppm以下。 (離子層析儀條件) 裝置：使用Dionex製造之ICS-1500抑制器 分析管柱：Dionex IonPac AS14 內徑4.0 mm×長度50 mm 保護管柱：Dionex IonPac AG14 內徑4.0 mm×長度250 mm 溶離液：3.5 mmol Na2
CO3
、1.0 mmol NaHCO3
流量：1.5 mL/min 將以上之氯離子濃度之測定結果彙總示於第1表。 [評價試驗] 使用各含氟樹脂之溶液，實施以下之評價試驗。 ＜儲藏穩定性＞ 將各含氟樹脂之溶液以70℃加溫2週，測定加溫前後之Mn，以(加溫後之Mn)/(加溫前之Mn)作為分子量增加率，基於其分別對儲藏穩定性進行評價。 ＜剛成膜後之光澤性＞ 將各含氟樹脂之溶液蒸發乾燥、粉碎，分別獲得粉末狀之氟樹脂組合物。相對於所獲得之各粉末狀之氟樹脂組合物100質量份添加氧化鈦(Dupont公司製造，Ti-Pure(註冊商標)R960)67質量份、封端化異氰酸酯系硬化劑(Evonik公司製造，Vestagon(註冊商標)B1530)25質量份、作為硬化觸媒之二月桂酸二丁基錫之二甲苯溶液(10,000倍稀釋品)0.012質量份、作為除氣劑之安息香0.8質量份、表面調整劑(BYK-Chemie公司製造，BYK(註冊商標)-360P)2質量份，使用高速混合器(佑崎有限公司製造)混合10〜30分鐘左右而分別獲得粉末狀之混合物。 使用雙軸擠出機(Thermo Prism公司製造，16 mm擠出機)，於120℃之機筒設定溫度下，將粉末狀之混合物進行熔融混練而獲得顆粒。繼而，使用粉碎機(FRITSCH公司製造，高速旋轉粉碎機(rotor speed mill)P14)於常溫下將顆粒粉碎，藉由150目之篩進行分級而分別獲得平均粒徑約為40 μm之粉體塗料組合物。 使用各粉體塗料組合物，藉由靜電塗裝機(Onoda Cement公司製造，GX3600C)對經鉻酸鹽處理之鋁板之一面進行靜電塗裝，於200℃環境中保持20分鐘。然後，將其放置冷卻至室溫，獲得附有厚度55〜65 μm之塗膜(硬化膜)之鋁板。 使用光澤計(日本電色工業公司製造，PG-1M)，於形成塗膜後24小時後對塗膜之表面之20°光澤度進行測定。 ＜流動性＞ 將各含氟樹脂之溶液蒸發乾燥、粉碎而分別獲得粉末狀之氟樹脂組合物。使用錠劑成形機，於壓力20 MPa、10秒之條件下將粉末狀之氟樹脂組合物0.5 g成形為錠劑狀。 使用雙面膠帶將錠劑狀之氟樹脂組合物貼附於鋁板，於傾斜60度之狀態下以200℃加溫20分鐘，測定流動之距離。基於流動之距離，藉由以下基準對流動性進行評價。 ◎：流動距離為100 mm以上 ○：流動距離為60 mm以上且未達100 mm △：流動距離為30 mm以上且未達60 mm ×：流動距離未達30 mm ＜評價結果＞ 將以上評價試驗之結果示於第1表。再者，第1表中之括號內之數值表示相對於氟樹脂之含量(固形物成分)100質量份之各成分之含量(質量份)。 [表1]
如第1表所示，實施例之含氟樹脂之溶液之氯離子濃度均為50質量ppm以下，因此藉由使用其而獲得之塗料組合物所製作之塗膜之剛成膜後之塗膜之光澤性優異。又，實施例之含氟樹脂之溶液之儲藏穩定性亦均優異。 又，根據實施例1〜7之對比顯示，若氯離子濃度為3〜30質量ppm(實施例4及5)，則流動性亦優異。 另一方面，比較例1及比較例3之含氟樹脂之溶液之氯離子濃度超過50質量ppm，因此藉由使用其而獲得之塗料組合物所製作之塗膜之剛成膜後之塗膜之光澤性不充分。 此處，比較例1及比較例3中，使氟樹脂進行聚合時之水滑石之量相對於含胺基之化合物之量之比率處於1〜4之範圍外。因此認為，與水滑石一併作為不溶解成分而排出至含氟樹脂之溶液之系統外的氯離子量變少，氯離子濃度上升。 又，比較例2之含氟樹脂之溶液雖然氯離子濃度較低，但不含含胺基之化合物，因此儲藏穩定性較差(加溫後含氟樹脂之溶液凝膠化而無法測定氟樹脂之Mn)。又，於製作使用比較例2之含氟樹脂之溶液所獲得之塗料組合物時發生凝膠化，無法製造粉體組合物，而無法評價剛成膜後之光澤性。 再者，將於2016年01月14日提出申請之日本專利申請案2016-005279號之說明書、申請專利之範圍及摘要之全部內容引用至此，作為本發明之說明書之揭示而併入。In the present specification, the "unit based on a monomer" is a general term for an atomic group directly formed by polymerization of one molecule of a monomer and an atomic group obtained by chemically converting a part of the atomic group. In addition, hereinafter, a unit based on a single unit is also simply referred to as a "unit". The content (mol%) of each unit of the fluoropolymer can be determined by analyzing the fluoropolymer by nuclear magnetic resonance spectroscopy, or can be estimated from the amount of each monomer added. The "crosslinkable group" means a group which can form a crosslinked structure by reacting with a curing agent to form a crosslinked structure or a crosslinkable group. In the present specification, the number average molecular weight and the mass average molecular weight are values obtained by polystyrene conversion by a gel permeation chromatography (GPC) method. The number average molecular weight is also referred to as Mn. The term "hydrotalcite" means a layered double hydroxide represented by the following formula. Where x is 0.2 to 0.33 and m is 0 to 2. The term "(meth)acrylate" is a generic term for acrylate and methacrylate. The "ether ester solvent" means a compound having both an ether bond and an ester bond in the molecule. Hereinafter, the solution of the fluorine-containing resin of the present invention, the method for producing a solution of the fluorine-containing resin, the coating composition, and the coated article will be described in detail. [Solution of fluorine-containing resin] The solution of the fluorine-containing resin of the present invention contains: contains chlorotrifluoroethylene (CF) 2 a fluoropolymer fluororesin, an amine group-containing compound, and an organic solvent of a unit of CFCC, hereinafter referred to as "CTFE", and having a chloride ion concentration of 50 by the following chloride ion concentration measurement method The mass is below ppm. Chloride ion concentration measurement method: a solution of the above fluorine-containing resin and xylene are mixed to prepare a sample solution, and the obtained sample solution is mixed with water, and then phase separated into a xylene phase and an aqueous phase, and the aqueous phase is subjected to an aqueous phase. The chloride ion concentration in the recovered water was recovered and determined by ion chromatography. In addition, the above-described chloride ion concentration measurement method is also referred to as a "specific measurement method", and the chloride ion concentration means a chloride ion concentration determined by a specific measurement method. The solution of the fluorine-containing resin of the present invention is excellent in storage stability, and can form a coating film excellent in gloss immediately after film formation. The detailed reason is not clear, but it is considered to be based on the following reasons. In the present invention, a fluororesin comprising a fluoropolymer having a unit based on CTFE is used. The inventors of the present invention prepared a coating composition using a solution containing a fluorine-containing resin having a fluoropolymer based on a unit of CTFE, and a coating film obtained by using the coating composition, according to the method specifically described in Patent Document 1. Gloss (refer to Comparative Example 1 described below). As a result, the inventors of the present invention found that the glossiness of the coating film immediately after film formation was lowered. Then, the inventors have found that the chloride ion concentration of the solution of the fluorine-containing resin is closely related to the decrease in the gloss of the coating film immediately after film formation. Specifically, the present inventors have found that, as shown in the examples below, when the chloride ion concentration is equal to or less than a specific value, a coating film excellent in gloss immediately after film formation can be obtained. Further, the reason for the detailed correlation between the chloride ion and the gloss of the coating film is not clear, and it is considered that the gloss is deteriorated based on the following reasons: when the coating film is formed, an acid-derived component (chloride ion derived from hydrogen chloride, etc.) The difference in the hardening rate between the surface of the coating film and the inside of the coating film locally formed on the surface of the coating film; or the gelation of the fluororesin before the film formation in the baking coating, the melt fluidity is deteriorated, and the uniform coating is not formed. membrane. In addition, "after film formation" means that it is within 24 hours from the production of the coating film. Further, since the solution of the fluorine-containing resin of the present invention contains an amine group-containing compound, it is presumed that the fluororesin can be stably present in the solution. As a result, it is considered that the viscosity-increasing or the like of the solution of the fluorine-containing resin is suppressed, and the storage stability of the solution of the fluorine-containing resin is excellent. Further, Patent Document 1 discloses a specific aspect in which a solution containing a fluorine-containing resin having a fluorine-containing polymer having a unit based on CTFE is produced using an amine group-containing compound and hydrotalcite, but the inventors found that the state The concentration of chloride ions in the sample is high. The reason for this is not necessarily clear, but it is considered as follows. First, it is considered that the chloride ion contained in the solution of the fluorine-containing resin is mainly produced by decomposition of CTFE which occurs when CTFE is polymerized. In the case where such a chloride ion is present, if an amine group-containing compound is present, a hydrochloride is formed between the amine group-containing compound and the chloride ion. Further, in the case where hydrotalcite is present in this case, chloride ions are also adsorbed by the hydrotalcite. That is, in the specific aspect of Patent Document 1, both the chloride ion and the amine group-containing compound form a salt, and the chloride ion is adsorbed to the hydrotalcite. The hydrotalcite is separated from the fluoropolymer by filtration treatment or the like after polymerization. Therefore, the chloride ions adsorbed by the hydrotalcite are removed to the outside of the system. On the other hand, chloride ions forming a salt with the amine group-containing compound remain in the system. That is, the amount of chloride ions contained in the solution of the fluorine-containing resin is affected by the amount of the amine group-containing compound and the hydrotalcite. Specifically, the present inventors have found that when the amount of the amine group-containing compound used is larger than that of the hydrotalcite, a large amount of chloride ions which form a salt with the amine group-containing compound remain in the system, and as a result, The concentration of chloride ions becomes high, so the desired effect cannot be obtained. In the present invention, as described in detail below, when the solution of the fluorine-containing resin is produced, the quality of use of the hydrotalcite is set to a specific ratio with respect to the mass of the amine group-containing compound, and the system external removal amount of the chloride ion is used. Since the residual amount in the system is controlled, it is considered that the chloride ion concentration of the solution of the fluorine-containing resin can be lowered, and as a result, the desired effect can be obtained. The fluoropolymer in the present invention has a unit based on CTFE, and preferably further has units other than the above units (hereinafter also referred to as other units). The other unit is preferably a unit based on a fluoroolefin other than CTFE, a unit based on a monomer having a crosslinkable group (hereinafter also referred to as "monomer 1"), or a single unit based on having no fluorine atom and a crosslinkable group. The unit of the body (hereinafter also referred to as "monomer 2") is more preferably a unit based on monomer 1 or a unit based on monomer 2. It is especially preferred that the fluoropolymer has both monomer based units and monomer 2 based units. The number of fluorine atoms in the fluoroolefin other than CTFE is preferably 2 or more, more preferably 2 to 6, and still more preferably 3 to 4. When the number of fluorine atoms is 2 or more, the coating film obtained is excellent in weather resistance. The fluoroolefin other than CTFE is preferably CF 2 =CF 2 , CH 2 =CF 2 , or CH 2 =CFCF 3 , especially good for CF 2 =CF 2 . Two or more kinds of fluoroolefins other than CTFE may be used. Monomer 1 is a monomer having a crosslinkable group. The crosslinkable group is preferably a functional group having a living hydrogen (hydroxy group, carboxyl group, amine group, etc.), or a hydrolyzable decyl group (alkoxyalkylene group or the like), an epoxy group or an oxetanyl group. Monomer 1 is preferably of formula CH 2 =CX 1 (CH 2 ) N1 -Q 1 -R 1 -Y 1 The monomer represented. Where, in the formula, X 1 Is a hydrogen atom or a methyl group, n1 is 0 or 1, Q 1 Is a single bond, an etheric oxygen atom, -C(O)O- or -O(O)C-,R 1 Is an alkylene group having 2 to 20 carbon atoms, an alkylene group having an etheric oxygen atom having 2 to 20 carbon atoms, or an alkylene group having a ring structure of 6 to 20 carbon atoms, Y 1 It is a crosslinkable group. X 1 It is preferably a hydrogen atom. N1 is preferably 0. Q 1 It is preferably an oxygen atom or -O(O)O-, preferably an oxygen atom. R 1 It is preferably a linear alkyl group having 1 to 10 carbon atoms. The carbon number of the alkylene group is more preferably from 1 to 6, more preferably from 2 to 4. Y 1 It is preferably a hydrolyzable alkylene group, a hydroxyl group, a carboxyl group or an amine group, more preferably a hydroxyl group, a carboxyl group or an amine group, and further preferably a hydroxyl group. Specific examples of the monomer 1 include a hydroxyalkyl vinyl ether (2-hydroxyethyl vinyl ether, hydroxymethyl vinyl ether, 4-hydroxybutyl vinyl ether, etc.), a hydroxyalkyl vinyl group. An ester, a hydroxyalkyl allyl ether (such as hydroxyethyl allyl ether), a hydroxyalkyl allyl ester, a hydroxyalkyl (meth) acrylate (hydroxyethyl (meth) acrylate), or the like. Preferably, the hydroxyalkyl vinyl ester, the hydroxyalkyl group of the hydroxyalkyl allyl ester, and the hydroxyallyl group are bonded to the carbon atom of the carbonyl group of the ester bond, respectively. The monomer 1 is preferably a hydroxyalkyl vinyl ether or a hydroxyalkyl allyl ether, and is preferably a hydroxyalkyl vinyl ether in terms of excellent copolymerizability and excellent weather resistance of the formed coating film. More preferably, it is 4-hydroxybutyl vinyl ether. Two or more types of the monomer 1 can also be used. Monomer 2 is a monomer which does not have a fluorine atom and a crosslinkable group. As monomer 2, preferably formula CH 2 =CX 2 (CH 2 ) N2 -Q 2 -R 2 The monomer represented. Where, in the formula, X 2 Is a hydrogen atom or a methyl group, n2 is 0 or 1, Q 2 Is a single bond, an oxygen atom, -C(O)O- or -O(O)C-,R 2 It is an alkyl group having 2 to 20 carbon atoms, an alkyl group having an etheric oxygen atom having 2 to 20 carbon atoms, or an alkyl group having 6 to 20 carbon atoms having a ring structure. X 2 It is preferably a hydrogen atom. N2 is preferably 0. Q 2 It is preferably an oxygen atom or -O(O)C-, preferably an oxygen atom. R 2 Preferably, it is an alkyl group having 1 to 10 carbon atoms or an alkyl group having a ring structure of 6 to 20 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 6 to 12 carbon atoms. Preferably, it is an alkyl group having 2 to 4 carbon atoms or a cycloalkyl group having 6 to 10 carbon atoms. Specific examples of the monomer 2 include an alkyl vinyl ether, a cycloalkyl vinyl ether, an alkyl vinyl ester, an alkyl allyl ether, an alkyl allyl ester, and an alkyl (meth)acrylate. Base ester and the like. Preferably, the alkyl group in the alkyl vinyl ester and the alkyl allyl ester is bonded to the carbon atom of the carbonyl group of the ester bond. The monomer 2 is preferably an alkyl vinyl ether or a cycloalkyl vinyl ether, more preferably ethyl vinyl ether, cyclohexyl vinyl ether or 2-ethylhexyl vinyl ether, and the rigidity of the fluororesin It is preferably a cyclohexyl vinyl ether in terms of being high in solubility in an organic solvent, easy to apply in the case of application to a coating, and a hard coating film. Two or more types of the monomer 2 can also be used. The ratio of the CTFE-based unit in the fluoropolymer is preferably from 40 to 60 mol%, more preferably from 45 to 55 mol%, based on all units of the fluoropolymer. When the ratio is 40 mol% or more, the obtained coating film is excellent in weather resistance. When the ratio is 60 mol% or less, the solubility in an organic solvent or a diluent is excellent. In the case where the fluoropolymer has a unit based on the monomer 1 and a unit based on the monomer 2, the total ratio thereof is preferably 40 to 60 mol% with respect to all units of the fluoropolymer, and more preferably Good for 45~55 mol%. Therefore, when the unit other than the unit based on the CTFE is only based on the unit of the monomer 1 and the unit based on the monomer 2, the ratio of the unit based on the monomer 1 and the unit based on the monomer 2 is relative to the fluorine-containing All of the units of the polymer are preferably from 40 to 60 mol%, more preferably from 45 to 55 mol%. The ratio in the case of having a unit based on the monomer 1 is preferably from 5 to 40 mol%, more preferably from 8 to 35 mol%, based on all units of the fluoropolymer. When the ratio is 5 mol% or more, a crosslinkable group in an amount sufficient to obtain a coating film having a high hardness is introduced into the fluoropolymer. When the ratio is 40 mol% or less, even if it is a high solid content type, the low viscosity which is sufficient as a solution of a fluorine resin can be maintained. The ratio in the case of having a unit based on the monomer 2 is preferably more than 0 mol% and more than 45 mol%, more preferably 3 to 45 mol%, based on all units of the fluoropolymer. Further preferably, it is 20 to 45 mol%. If the unit is provided, the hardness or flexibility of the obtained coating film can be appropriately adjusted. When the ratio is 45 mol% or less, it is easy to introduce a crosslinkable group in an amount sufficient for obtaining a coating film having excellent weather resistance and high hardness in the fluoropolymer. In the case of a cell based on a unit based on CTFE, a unit based on monomer 1 and a unit based on a unit based on monomer 2, the ratio of the unit is preferably relative to all units of the fluoropolymer. 20 mol% or less, more preferably 10 mol% or less. The Mn of the fluoropolymer is preferably from 3,000 to 50,000, more preferably from 5,000 to 30,000. When the Mn of the fluoropolymer is at least the above lower limit value, the coating film is excellent in water resistance, salt water resistance, and the like. When the Mn of the fluoropolymer is at most the above upper limit value, the surface smoothness of the coating film is excellent. Further, in the solution of the fluorine-containing resin of the present invention, substantially no hydrotalcite is contained. The substantially non-hydrotalcite means that the amount of the hydrotalcite contained in the solution of the fluorine-containing fat of the present invention is less than 0.1% by mass, and usually preferably 0.01% by mass or less. The lower limit of the amount of hydrotalcite is 0% by mass. The amine group-containing compound in the present invention is not particularly limited as long as it is an amine group-containing compound. Further, in the present specification, the above "amino group-containing compound" also includes a form of forming a salt with hydrogen chloride (HCl). That is, the above "amino group-containing compound" also includes a hydrochloride salt of an amine group-containing compound. As the amine group, a primary amine group (-NH) 2 ), a secondary amine group, a tertiary amine group. Secondary amine system - NHR N (R N a monosubstituted amine group represented by a monovalent substituent) as R N Specific examples thereof include an alkyl group, an aryl group, an ethyl fluorenyl group, a benzamidine group, a benzenesulfonyl group, and a third butoxycarbonyl group. Specific examples of the secondary amine group include a methylamine group, an ethylamino group, a propylamine group, an isopropylamine group, and the like, wherein R is an alkyl group-based amine group; or a phenylamine group or a naphthalene group; R such as an amino group is a secondary amine group of an aryl group or the like. Also, R N The hydrogen atom may be further substituted with an ethyl hydrazide group, a benzamidine group, a benzenesulfonyl group, a third butoxycarbonyl group or the like. The tertiary amine group is of the formula -NR N1 R N2 (R N1 And R N2 a disubstituted amine group represented by a monovalent substituent) as R N1 And R N2 Specific examples, with R N the same. Specific examples of the tertiary amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, an ethylmethylamino group, a diphenylamino group, and a methylphenylamino group. As the amine group, an alicyclic amine group can also be mentioned. An alicyclic group having at least one nitrogen atom in the alicyclic amine ring. The alicyclic amine group is preferably a pyrrolidinyl group, a piperidinyl group, a piperidine group, a sulfonyl group, or a 5- to 4-membered ring alicyclic amine group, and particularly preferably a 6-membered ring. An alicyclic amine group (piperidinyl). Further, the hydrogen atom in the alicyclic amine group may be further substituted with a substituent (alkyl group, aryl group, etc.). The alicyclic amine group of the 6-membered ring is preferably a piperidinyl group or a piperidinyl group having a substituent, more preferably a piperidinyl group having a substituent, and further preferably a tetra-substituted piperidinyl group, and particularly preferably 2, 2,6,6-tetrasubstituted piperidinyl. The amine group-containing compound may be used alone or in combination of two or more. The amine group-containing compound is preferably a compound represented by the following formula (a compound having a 2,2,6,6-tetrasubstituted piperidinyl group). [Chemical 1] R 11 ~R 14 Each is independently an alkyl group having 1 to 18 carbon atoms (methyl, ethyl, propyl, dodecyl, stearyl, etc.), a cycloalkyl group (cyclopentyl group, cyclohexyl group, etc.), a substituted alkyl group (2) - hydroxyethyl, 2-methoxycarbonylethyl, 3-hydroxypropyl, etc.), aryl (phenyl, naphthyl, etc.) or aralkyl (phenethyl, benzyl, etc.), R 11 And R 12 , or R 13 And R 14 An aliphatic ring having a carbon number of 3 to 6 can be formed. As R 11 ~R 14 In terms of price and ease of availability, an alkyl group having 1 to 18 carbon atoms is preferred, and a methyl group is particularly preferred. R 15 Is a hydrogen atom, an alkyl group (methyl, ethyl, propyl, butyl, dodecyl, stearyl, etc.), a substituted alkyl group (2-hydroxyethyl, 2-methoxycarbonylethyl, 2 -Ethyloxyethyl, 2-(3-methoxycarbonylpropoxy)ethyl, 3-hydroxypropyl, etc., aryl (phenyl, naphthyl, hydroxyphenyl, etc.), aralkyl a group (phenethyl, benzyl, hydroxyphenylalkyl, etc.) or a cycloalkyl group (cyclohexyl, etc.). R 16 Is a hydrogen atom, a hydroxyl group, an alkyl group (methyl, ethyl, propyl, butyl, dodecyl, stearyl, etc.), a substituted alkyl group (2-hydroxyethyl, 2-methoxycarbonylethyl) , 2-ethoxymethoxyethyl, 2-(3-methoxycarbonylpropoxy)ethyl, 3-hydroxypropyl, etc., aryl (phenyl, naphthyl, etc.), aralkyl ( Phenylethyl, benzyl, etc., an ester-containing group (acetoxy, propyloxy, butyloxy, lauryloxy, substituted alkylcarbonyloxy, benzhydryloxy, substituted benzene Alkoxy group, etc., an amino group-containing group (alkoxycarbonylamino group, N-monoalkylamine formamylamino group, N,N-dialkylamine formamylamine group, etc.) or 2 a 2,6,6-tetrasubstituted piperidinyl group. R 16 Two or more of these groups may be combined. Specific examples of the amine group-containing compound include 2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethylpiperidine, and 4-hydroxy-2,2. 6,6-tetramethylpiperidine, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, 1-ethyl-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-butyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-12 Alkyl-2,2,6,6-tetramethylpiperidine, 1-phenyl-2,2,6,6-tetramethylpiperidine, 1-(2-hydroxyethyl)-2,2, 6,6-tetramethylpiperidine, 1-(6-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-ethyloxy-2,2,6 ,6-tetramethylpiperidine, 4-ethenyloxy-1,2,2,6,6-pentamethylpiperidine, 1-(2-acetoxyethyl)-4-ethoxime Base-2,2,6,6-tetramethylpiperidine, 1-(2-benzylideneoxyethyl)-4-benzylideneoxy-2,2,6,6-tetramethylper Pyridine, 4-ethyl-2,2,6,6-tetramethylpiperidine, 4-ethyl-1,2,2,6,6-pentamethylpiperidine, 4-butyl-2,2 6,6-tetramethylpiperidine, 4-octyl-2,2,6,6-tetramethylpiperidine, 4-dodecyl-2,2,6,6-tetramethylpiperidine , 4-stearyl-2,2,6,6-tetramethylpiperidine, 4-stearyl-1,2,2,6,6-pentamethylpiperidine, methyl sebacate 1, 2,2,6,6-pentamethyl-4- Piperidine sebacate bis (2,2,6,6-tetramethyl-4-piperidyl) ester. As R 16 The amine group-containing compound having a 2,2,6,6-tetra-substituted piperidinyl group may, for example, be a 2,2,6,6-tetramethylpiperidine having a hydroxyl group (4-hydroxy-2, 2,6,6-tetramethylpiperidine, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, 1-(2-hydroxyethyl)-4-hydroxy-2,2, 6,6-tetramethylpiperidine, 1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine, etc.) and polybasic acids (succinic acid, adipic acid, sebacic acid, Obtained by reacting azelaic acid, decane-1,10-dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, malonic acid, substituted malonic acid, etc. The amine group-containing compound containing two or more of 2,2,6,6-tetramethylpiperidinyl groups in one molecule, and specific examples thereof include compounds represented by the following formulas. Wherein n3 is an integer of 1 to 20. [Chemical 2] The content of the amine group-containing compound is preferably 0.1 to 2.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, even more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the fluororesin. When the content is 0.1 parts by mass or more, the solution of the fluorine-containing resin becomes less likely to be gelled during the polymerization of the monomer component or after the polymerization, and the storage stability of the solution of the fluorine-containing resin is further excellent. In addition, when the content is 2.0 parts by mass or less, the discoloration (for example, yellowing or white turbidity) of the solution in the storage of the fluororesin solution or the increase in the molecular weight of the fluoropolymer is further suppressed, and the fluororesin is further suppressed. The storage stability of the solution is more excellent. The organic solvent in the present invention is not particularly limited as long as it is an organic solvent capable of dissolving the fluororesin, and is preferably selected from the group consisting of an aromatic hydrocarbon solvent, a ketone solvent, an ester solvent, an alcohol solvent, and an ether ester solvent. One or more organic solvents of the group. The aromatic hydrocarbon solvent is preferably toluene, xylene, ethylbenzene, aromatic naphtha, tetralin, or turpentine. A commercially available product can be used as the aromatic hydrocarbon solvent, and Solvesso (registered trademark) #100 (manufactured by Exxon Chemical Co., Ltd.), Solvesso (registered trademark) #150 (manufactured by Exxon Chemical Co., Ltd.), or the like can be used. The ketone solvent is preferably acetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, diisobutyl ketone, cyclohexanone, or isophorone. The ester solvent is preferably methyl acetate, ethyl acetate, n-propyl acetate, isobutyl acetate, or tert-butyl acetate. The alcohol solvent is preferably an alcohol having 4 or less carbon atoms, preferably ethanol, third butanol or isopropanol. The ether ester-based solvent is preferably ethyl 3-ethoxypropionate, propylene glycol monomethyl ether acetate, or methoxybutyl acetate. Two or more organic solvents can also be used. Further, the organic solvent may be the same organic solvent as the organic solvent used as the polymerization solvent, or may be an organic solvent different therefrom. The content of the organic solvent is preferably such that the concentration of the solid content in the solution of the fluorine-containing resin is 40 to 80% by mass, from the viewpoint of the solubility of the fluororesin. The solution of the fluorine-containing resin of the present invention may contain a component other than the above (for example, a general-purpose resin component such as an acrylic resin or a polyester resin) within a range in which the effects of the present invention can be sufficiently exhibited. The solution of the fluorine-containing resin of the present invention has a chloride ion concentration of 50 ppm by mass or less as determined by a specific measurement method. The chloride ion concentration is more preferably 40 ppm by mass or less, further preferably 30 ppm by mass or less, and particularly preferably 10 ppm by mass or less. The lower limit is preferably 1 ppm by mass, and more preferably 3 ppm by mass. When the chloride ion concentration is 50 ppm by mass or less, the coating film obtained by using the solution of the fluorine-containing resin of the present invention is excellent in gloss immediately after film formation. On the other hand, when the chloride ion concentration exceeds 50 ppm by mass, the glossiness immediately after film formation becomes insufficient. In particular, when the chloride ion concentration is 3 to 30 ppm by mass, the coating composition obtained by using the solution of the fluorine-containing resin is also excellent in fluidity. When the coating composition obtained by using the fluororesin solution is excellent in fluidity, when the powder composition coated on the substrate is melted to form a coating film (cured film), the fluidity of the coating composition is improved. Therefore, it is preferable in terms of obtaining a smooth and uniform coating film (hardened film). When the chloride ion concentration is 30 ppm by mass or less, the generation of hydrogen chloride by the powder of the fluorine-containing resin (desolvation) or the heat during baking coating can be suppressed. It is presumed that the gelation of the fluororesin contained in the coating composition is suppressed, and the fluidity of the coating composition is improved. In the present invention, the chloride ion concentration is determined by a specific measurement method, that is, the solution of the fluorine-containing resin of the present invention is mixed with xylene to prepare a sample solution, and the obtained sample solution is mixed with water. The phase is separated into a xylene phase and an aqueous phase, and the aqueous phase is recovered and the chloride ion concentration in the recovered water is measured by ion chromatography. More specifically, the chloride ion concentration was measured as follows. First, the solution of the fluorine-containing resin of the present invention is mixed with xylene and stirred to obtain a sample solution. Further, the amount of the solution of the fluorine-containing resin was set to 0.5 g with respect to 5 mL of the amount of xylene. Then, the sample solution was mixed with pure water and stirred to obtain a mixed solution. Further, the amount of pure water was set to 3 mL with respect to the addition amount of the sample solution of 4.9 g. Then, the mixed solution was centrifuged to separate the mixed liquid phase into an aqueous phase and a xylene phase, and the xylene phase was removed to obtain a separating liquid. Further, the separation liquid is subjected to centrifugal separation to phase-separate into residual xylene (xylene phase) and water (aqueous phase), and the xylene phase is removed to recover the aqueous phase. Then, a measurement liquid obtained by adding pure water to the recovered water (aqueous phase) was prepared, and the chloride ion concentration was measured by ion chromatography. In addition, a known centrifugal separation apparatus (specifically, a device manufactured by Kubota Seisakusho Co., Ltd., "Baked Cooling Centrifuge 5500") is used in any of the centrifugation, and the conditions of the centrifugal separation are set at 12,000 rpm. minute. Further, the measurement by ion chromatography is carried out, for example, by using an apparatus according to an ion chromatograph ICS-1500 (trade name, manufactured by Dionex Co., Ltd.). The specific measurement conditions of the chloride ion concentration measured by ion chromatography are as follows. Furthermore, the detection amount is measured with respect to the peak area ratio of the standard solution whose concentration is known, and the chloride ion (Cl) is converted. - The amount. Also, chloride ion (Cl - The quantitative limit is below 0.6 ppm. <Ion Chromatography Conditions> Apparatus: Analytical column using Dionex ICS-1500 suppressor: Dionex IonPac AS14 Inner diameter 4.0 mm × length 50 mm Protection column: Dionex IonPac AG14 Inner diameter 4.0 mm × length 250 mm Dissolution Liquid: 3.5 mmol Na 2 CO 3 , 1.0 mmol NaHCO 3 Flow rate: 1.5 ml/min [Manufacturing method of the solution of the fluorine-containing resin] The method for producing the solution of the fluorine-containing resin of the present invention is a method of bringing a monomer containing CTFE in the presence of an amine group-containing compound and hydrotalcite. The component is polymerized in an organic solvent to obtain a mixed solution containing a fluorine-containing polymer, and then a solution containing the fluorine-free resin derived from the insoluble component of the hydrotalcite is removed from the mixed solution containing the fluorine-containing polymer. Further, at the time point when the polymerization of the monomer component is started, the ratio of the amount of the hydrotalcite to the amount of the amine group-containing compound (the amount of the hydrotalcite / the amount of the amine group-containing compound) is 1 to 4. Further, the chloride ion concentration determined by a specific measurement method is preferably 50 ppm by mass or less. According to the method for producing a solution of a fluorine-containing resin of the present invention, a solution of a fluorine-containing resin excellent in storage stability can be obtained, and a coating film having excellent glossiness immediately after film formation can be formed. Hereinafter, the step of performing the polymerization is referred to as a polymerization step, and the step of performing the filtration is referred to as a filtration step, and each step will be described in detail. The monomer component in the polymerization step is polymerized by a so-called solution polymerization method. The order of addition of each component in the polymerization system can be appropriately selected. As the monomer component, in addition to CTFE, monomer 1 and monomer 2 can also be used. The details of the amine group-containing compound, CTFE, and fluororesin in the polymerization step are as described above, and the description thereof will be omitted. The organic solvent is the same as the organic solvent described in the solution of the fluorine-containing resin. The organic solvent in the polymerization step may be the same as or different from the organic solvent contained in the solution of the fluorine-containing resin of the present invention. The hydrotalcite in the polymerization step is preferably Mg in terms of excellent adsorption of chloride ions and easy availability. 6 Al 2 (OH) 16 CO 3 ·4H 2 O (in the above formula indicating hydrotalcite, x = 0.25, m = 0.5), or Mg 4.5 Al 2 (OH) 13 CO 3 ·3.5H 2 O (in the above formula indicating hydrotalcite, x = 0.308, m = 0.538). Hydrotalcite can also be used in two or more types. The particle size of the hydrotalcite is preferably from 5 to 500 μm, more preferably from 5 to 110 μm. When the particle size of the hydrotalcite is 5 μm or more, it is easily removed by filtration. When the particle size of the hydrotalcite is 500 μm or less, the surface area per unit mass is large, and the effect obtained by the hydrotalcite is further exerted. The particle size of the hydrotalcite is measured in accordance with the "Chemical Screening Test Method" of JIS K 0069. In the polymerization step, it is preferred to polymerize the monomer component by the action of a polymerization initiator. Examples of the polymerization initiator include an azo initiator (2,2'-azobisisobutyronitrile, 2,2'-azobiscyclohexanenitrile, 2,2'-azobis (2, 4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), etc., peroxide-based initiator {peroxyketone (cyclohexanone peroxide, etc.), peroxidation Hydrogen (tertiary butyl hydroperoxide, etc.), diamyl peroxide (benzaldehyde peroxide, etc.), dialkyl peroxide (dibutylbutyl peroxide, etc.), peroxyketal (2, 2) -di-(t-butylperoxy)butane, etc.), alkyl peroxyester (tert-butyl peroxypivalate, etc.), peroxycarbonate (diisopropyl peroxydicarbonate, etc.) }. The ratio of the mass of the hydrotalcite to the mass of the amine group-containing compound (the mass of the hydrotalcite/the mass of the amine group-containing compound) is from 1 to 4, preferably from 1.0 to 3, at the point of polymerization at the beginning of the polymerization step. , especially good for 1.0~2. When the ratio is 1 or more, the chlorine ion concentration can be adjusted to a specific range as described in the solution of the fluorine-containing resin, and the gloss of the coating film immediately after the film formation is excellent. Moreover, when the ratio is 4 or less, clogging of the filter material is easily suppressed when the insoluble component is removed in the filtration step. The amount of the amine group-containing compound is preferably 0.1 to 2.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, still more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the monomer component. When the amount is 0.1 part by mass or more, the solution of the fluorine-containing resin becomes less likely to gel during or after the polymerization of the monomer component, and the storage stability of the solution of the fluorine-containing resin is further excellent. In addition, when the amount is 2.0 parts by mass or less, the discoloration (for example, yellowing or white turbidity) of the solution in the storage of the fluorine-containing resin or the increase in the molecular weight of the fluororesin is further suppressed, and the solution of the fluorine-containing resin is further suppressed. The storage stability is more excellent. The amount of CTFE in the monomer component is preferably from 40 to 60 mol%, more preferably from 45 to 55 mol%, based on the total of the monomer components. When the amount of CTFE is 40 mol% or more, the obtained coating film is excellent in weather resistance. When the amount of CTFE is 60 mol% or less, the solubility in an organic solvent or a diluent is excellent. In the case where monomer 1 and monomer 2 are contained as a monomer component, the total amount thereof is preferably 40 to 60 mol%, more preferably 45 to 55 mol%, based on the total monomer component. Therefore, when the monomer component other than the CTFE is only the monomer 1 and the monomer 2, the total amount of the monomer 1 and the monomer 2 is preferably 40 to 60 mol%, more preferably 40 to 60 mol%. Good for 45~55 mol%. The amount of the monomer 1 in the monomer component is preferably from 5 to 40 mol%, more preferably from 8 to 35 mol%, based on the total of the monomer components. When the amount is 5 mol% or more, a crosslinkable group in an amount sufficient to obtain a coating film having a high hardness is introduced into the fluoropolymer. When the amount is 40 mol% or less, even if it is a high solid content type, it can maintain a low viscosity as a solution of a fluorine resin. The amount of the monomer 2 in the monomer component is preferably more than 0 mol% and 45 mol% or less, more preferably 3 to 45 mol%, still more preferably 20 to 45, based on the total of the monomer components. Moer%. When the monomer 2 is used, the hardness or flexibility of the obtained coating film can be appropriately adjusted. When the amount is 45 mol% or less, it is easy to introduce a crosslinkable group in an amount sufficient for obtaining a coating film having excellent weather resistance and high hardness in the fluoropolymer. In the case of a monomer component containing a monomer other than CTFE, monomer 1 and monomer 2, the amount of the monomer is preferably 20 mol% or less, more preferably 10 mol%, based on the total monomer component. %the following. In the filtration step in the present invention, hydrotalcite (i.e., an insoluble component derived from hydrotalcite) adsorbed with chlorine ions generated in the polymerization step as an insoluble component insoluble in an organic solvent is removed. The removal is carried out by solid-liquid separation treatment such as filtration. The solution of the fluorine-containing resin obtained by the above production method of the present invention is preferably a chlorine ion concentration of 50 ppm by mass or less as measured by a specific measurement method. The range and effect of the chlorine ion concentration are more as described in the case of the solution of the fluorine-containing resin, and therefore the description thereof will be omitted. Further, the solution of the fluorine-containing resin obtained by the production method of the present invention is preferably substantially free of hydrotalcite. The term "substantially free of hydrotalcite" means that the amount of hydrotalcite contained in the solution of the fluorine-containing fat is less than 0.1% by mass, and usually preferably 0.01% by mass or less. The lower limit of the amount of hydrotalcite is 0% by mass. In the production method of the present invention, hydrotalcite may also be added to the mixed solution containing the fluoropolymer after the polymerization step and before the filtration step. Further, the stirring treatment may be carried out after the addition of the hydrotalcite and before the filtration step. Thereby, the chloride ion concentration can be further reduced, and the obtained coating film is more excellent in glossiness immediately after film formation. Further, the storage stability of the solution of the fluorine-containing resin tends to be more excellent. The amount of the hydrotalcite to be added is preferably from 0.1 to 3.0 parts by mass, more preferably from 0.5 to 2.0 parts by mass, per 100 parts by mass of the fluoropolymer produced. If the amount is within the above range, the above effects are further exhibited. [Coating Composition] The coating composition of the present invention is a coating composition obtained by using the solution of the fluorine-containing resin of the present invention. The coating composition of the present invention may be in the form of a liquid or a powder (so-called powder coating composition). The liquid coating composition is a coating composition containing a solution of the above fluorine-containing resin, and preferably contains a curing agent in addition to the solution of the fluorine-containing resin. Examples of the curing agent include an isocyanate curing agent, a blocked isocyanate curing agent, and an amine based resin. The isocyanate-based curing agent is preferably a yellow-free variant cyanate (for example, hexamethylene diisocyanate or isophorone diisocyanate). The blocked isocyanate-based curing agent is preferably a curing agent obtained by blocking an isocyanate group of an isocyanate-based curing agent by caprolactam, isophorone or β-diketone. An amine resin is a reaction product of an amine (melamine, melamine, urea, etc.) with an aldehyde (formaldehyde or the like) (hydroxymethyl melamine or the like) or a derivative thereof (alkyl etherified methylol melamine or the like). Examples of the amine-based resin include a melamine resin, a melamine resin, a urea resin, a sulfonamide resin, and an aniline resin. The content of the hardener is preferably from 1 to 100 parts by mass, more preferably from 1 to 50 parts by mass, per 100 parts by mass of the fluororesin in the coating composition. When the amount of the curing agent is 1 part by mass or more, the solvent resistance and hardness of the coating film are excellent. When it is 100 parts by mass or less, the workability and impact resistance of the coating film are excellent. The liquid coating composition may further contain components other than the above. Examples of such a component include a coloring agent, a resin other than the above fluororesin, a decane coupling agent, an ultraviolet absorber, and a curing catalyst. Further, the coating composition of the present invention may be a coating composition containing a fluororesin composition obtained by removing the organic solvent from the solution of the fluorine-containing resin of the present invention. The coating composition may be a liquid coating composition obtained by dissolving the fluororesin composition in a solvent or dispersing in a dispersion medium. A coating composition containing a fluororesin composition containing no liquid medium such as the above organic solvent is preferred. As the coating composition containing the fluororesin composition containing no liquid medium, a powdery coating composition (so-called powder coating composition) is preferred. The powdery coating composition contains a fluororesin composition which is obtained by removing the above organic solvent from the solution of the fluorine-containing resin of the present invention to form a powder. The powdery fluororesin composition can be produced by subjecting the composition of the fluorine-containing resin of the present invention to a known treatment such as drying treatment or pulverization treatment. The powdery coating composition preferably contains a curing agent in addition to the above fluororesin composition. The curing agent is the same as the above-described liquid coating composition, and the description thereof is omitted. Further, the powdery coating composition may further contain components other than the above. Such a component is the same as the above-described liquid coating composition, and the description thereof is omitted. [Coated article] The coated article of the present invention has a substrate and a coating film formed on the substrate by the coating composition. Examples of the coating method include spraying, air spraying, brushing, dipping, electrostatic coating, roll coating, and flow coating. The coating film may be a film (molten film) obtained by applying a known melt treatment after being applied to a substrate. Examples of the material of the substrate include inorganic materials, organic materials, and organic-inorganic composite materials. Examples of the inorganic material include concrete, natural stone, glass, metal (iron, stainless steel, aluminum, copper, brass, titanium, etc.). Examples of the organic substance include plastic, rubber, adhesive, wood, and the like. Examples of the organic-inorganic composite material include fiber-reinforced plastics, resin-reinforced concrete, and fiber-reinforced concrete. The shape, size, and the like of the substrate are not particularly limited. Examples of the use of the coated article of the present invention include transportation equipment (automobiles, electric trains, airplanes, etc.), civil structural members (bridge members, iron towers, etc.), and industrial parts (waterproof material sheets, grooves, tubes, etc.). , building components (building exterior, doors, window door components, monuments, poles, etc.), road components (central barriers for roads, guard rails, soundproof walls, etc.), communication parts, electrical parts, electronic parts, sun A surface sheet for a battery module, a back sheet for a solar cell module, or the like. EXAMPLES Hereinafter, the present invention will be described in detail by way of examples. However, the invention is not limited to the embodiments. The amount of each component in the tables described below represents the quality basis. The solid content concentration of the solution of the fluorine-containing resin was determined by measuring the heating residue by JIS K 5601-1-2 (established in 2009). The Mn of the fluororesin contained in the solution of the fluorine-containing resin was measured by GPC (manufactured by Tosoh Corporation, HLC-8220). Tetrahydrofuran was used as a developing solvent, and polystyrene was used as a standard substance. [Solution of Fluorine Resin] The solutions of the respective fluorine-containing resins of the examples and the comparative examples were prepared in the following manner. <Preparation of Solution of Fluoro Resin of Example 1> 7.32 g of an amine group-containing compound (manufactured by BASF, trade name "TINUVIN292", 癸) was added to a stainless steel pressure-resistant reactor containing 2500 mL of internal volume of a stirrer. Bis(1,2,2,6,6-pentamethyl-4-piperidinyl) diester and methyl 1,9,2,6,6-pentamethyl-4-piperidinyl ester Mixture (mass ratio: 3:1)), 7.32 g of hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd., trade name "KW500", particle size: 45 μm or less: 38%, 45 to 7 μm: 35%, 75 to 106 Mm: 21%, 106 to 500 μm: 6%), 746 g of xylene, 153 g of 4-hydroxybutyl vinyl ether, 601 g of cyclohexyl vinyl ether, degassed by using nitrogen gas The dissolved oxygen in the solution is removed. Further, 701 g of CTFE was introduced into the reactor, and the temperature was gradually raised, and 4.1 g of tributyl butyl peroxypivalate (polymerization initiator) was intermittently added at a temperature of 65 ° C. polymerization. After 24 hours, the reactor was water-cooled to stop the reaction. After cooling the reaction solution to room temperature, the unreacted monomer is removed, and the insoluble component of the obtained reaction liquid is removed by filtration using diatomaceous earth as a filter medium, and an appropriate amount of xylene is further added to obtain a solid content concentration of 60.0%. A solution of the fluorine-containing resin of Example 1. Further, the fluoropolymer contained in the solution of the fluorine-containing resin of Example 1 had an Mn of 15,500. <Preparation of a solution of the fluorine-containing resin of Example 2> Polymerization was carried out in the same manner as in the preparation of the solution of the fluorine-containing resin of Example 1, and hydrotalcite KW500 was further added to the obtained reaction liquid, and after stirring for 1 hour, The insoluble component was removed by filtration using diatomaceous earth as a filter medium, and an appropriate amount of xylene was further added to obtain a solution of the fluorine-containing resin of Example 2 having a solid content concentration of 60.0%. Further, the fluoropolymer contained in the solution of the fluorine-containing resin of Example 2 had an Mn of 15,500. <Preparation of a solution of the fluorine-containing resin of Examples 3 to 5 and Comparative Example 1> The amount of addition of at least one of the amine group-containing compound and the hydrotalcite added during the polymerization was changed to the amount described in the first table. Otherwise, the same procedure as in the preparation of the solution of the fluorine-containing resin of Example 1 was carried out, and the fluorine-containing resin solutions of Examples 3 to 5 and Comparative Example 1 were obtained. Further, the Mn of the fluoropolymer contained in the solutions of the fluorine-containing resins of Examples 3 to 5 and Comparative Example 1 was 15,100, 14,900, 14,800, and 15,400, respectively. <Examples 6 to 7> The amine group-containing compound added during the polymerization was changed from TINUVIN 292 to TINUVIN 770DF (trade name, manufactured by BASF, azelaic acid bis(2,2,6,6-tetramethyl-4-piperidine) The same operation as the preparation of the fluorine-containing solution of Example 1 except that the amount of the amine group-containing compound and the hydrotalcite added is the amount described in the first table. The fluorine-containing resin solutions of Examples 6 to 7 were obtained. Further, the fluoropolymers contained in the solutions of the fluorine-containing resins of Examples 6 to 7 had Mn of 15,000 and 14900, respectively. Moreover, the content of the hydrotalcite in the solution of the fluorine-containing resin obtained in each of the above examples is 0.01% by mass or less. <Preparation of the solution of the fluorine-containing resin of Comparative Example 2> The same procedure as the preparation of the solution of the fluorine-containing resin of Example 1 was carried out except that the compound of the fluorine-containing resin of Example 1 was not added, and Comparative Example 2 was obtained. A solution of a fluorine-containing resin. Further, the fluoropolymer contained in the solution of the fluorine-containing resin of Comparative Example 2 had an Mn of 16,400. <Preparation of the solution of the fluorine-containing resin of Comparative Example 3> The amount of the amine group-containing compound added during the polymerization was changed to the amount described in the first table, and the hydrotalcite was not added during the polymerization, and the addition was carried out. A solution of the fluorine-containing resin of Comparative Example 3 was obtained in the same manner as in the preparation of the solution of the fluorine-containing resin of Example 2. Further, the fluoropolymer contained in the solution of the fluorine-containing resin of Comparative Example 3 had an Mn of 15,600. <Chlorine ion concentration> The chloride ion concentration of each fluororesin solution was measured by the following procedure. 0.5 g of each of the fluorine-containing resin solutions and 5 mL of xylene were placed in a PP (polypropylene) tube, and shaken by hand for 1 minute to obtain a sample solution in which the solution of the fluorine-containing resin was completely dissolved in xylene. Then, 3 mL of pure water was added to the sample solution, and the mixture was vigorously shaken by hand to obtain a mixed solution. Then, the mixture was centrifuged, and the phases were separated into water and xylene, and then the xylene phase (upper layer) was removed from the mixed solution using a micropipette. Further, the mixed liquid from which the xylene phase has been removed is subjected to centrifugation to be separated into residual xylene (xylene phase) and water (aqueous phase). Any of the centrifugation was carried out for 5 minutes at 12,000 rpm using a centrifugal separator (trade name "Desktop Cooling Centrifuge 5500", manufactured by Kubota Corporation). Then, the measurement liquid obtained by diluting the separated water (water layer) by 5 times or 10 times with pure water is prepared, and the chloride ion concentration of the measurement liquid is measured by ion chromatography. The measurement by ion chromatography was carried out using an ion chromatograph ICS-3000 (trade name, manufactured by Thermo Fisher Co., Ltd.). The measurement conditions by ion chromatography are as follows. Specifically, the detection amount is measured with respect to the peak area ratio of the standard liquid whose concentration is known, and the chloride ion (Cl) is converted. - The amount. Furthermore, the quantitative limit is chloride ion (Cl - ) is calculated to be 0.6 ppm or less. (Ion Chromatography Conditions) Apparatus: Analytical column using Dionex ICS-1500 suppressor: Dionex IonPac AS14 Inner diameter 4.0 mm × length 50 mm Protection column: Dionex IonPac AG14 Inner diameter 4.0 mm × length 250 mm Dissolution :3.5 mmol Na 2 CO 3 , 1.0 mmol NaHCO 3 Flow rate: 1.5 mL/min The measurement results of the above chloride ion concentration are collectively shown in Table 1. [Evaluation Test] The following evaluation test was carried out using a solution of each fluorine-containing resin. <Storage stability> The solution of each fluorine-containing resin was heated at 70 ° C for 2 weeks, and Mn before and after the heating was measured, and (the Mn after heating) / (Mn before heating) was used as the molecular weight increase rate, based on The storage stability was evaluated separately. <Glossiness after Film Formation> Each of the fluorine-containing resin solutions was evaporated to dryness and pulverized to obtain a powdery fluororesin composition. 70 parts by mass of titanium oxide (manufactured by Dupont Co., Ltd., Ti-Pure (registered trademark) R960), and a blocked isocyanate-based curing agent (manufactured by Evonik Co., Ltd., Vestagon) were added to 100 parts by mass of each of the obtained fluororesin compositions. (registered trademark) B1530) 25 parts by mass, a xylene solution of dibutyltin dilaurate (10,000 times diluted product) as a curing catalyst, 0.012 parts by mass, 0.8 parts by weight of benzoin as a deaerator, and a surface conditioner (BYK- 2 parts by mass of BYK (registered trademark)-360P), which was mixed with a high-speed mixer (manufactured by Usaki Co., Ltd.) for about 10 to 30 minutes to obtain a powdery mixture. Using a twin-screw extruder (manufactured by Thermo Prism, a 16 mm extruder), the powdery mixture was melt-kneaded at a cylinder set temperature of 120 ° C to obtain pellets. Then, the granules were pulverized at a normal temperature using a pulverizer (manufactured by FRITSCH Co., Ltd., a high speed rotary mill P14), and classified by a sieve of 150 mesh to obtain a powder coating having an average particle diameter of about 40 μm, respectively. combination. One surface of the chromate-treated aluminum plate was electrostatically coated by an electrostatic coating machine (manufactured by Onoda Cement Co., Ltd., GX3600C) using each of the powder coating compositions, and kept at 200 ° C for 20 minutes. Then, it was left to cool to room temperature, and an aluminum plate with a coating film (hardened film) having a thickness of 55 to 65 μm was obtained. Using a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd., PG-1M), the 20° gloss of the surface of the coating film was measured 24 hours after the formation of the coating film. <Flowability> Each of the fluororesin solutions was evaporated to dryness and pulverized to obtain a powdery fluororesin composition. Using a tablet molding machine, 0.5 g of the powdery fluororesin composition was molded into a tablet form under the conditions of a pressure of 20 MPa and 10 seconds. The tablet-shaped fluororesin composition was attached to an aluminum plate using a double-sided tape, and the mixture was heated at 200 ° C for 20 minutes while being inclined at 60 degrees, and the flow distance was measured. Based on the distance of the flow, the fluidity was evaluated by the following criteria. ◎: The flow distance is 100 mm or more ○: The flow distance is 60 mm or more and less than 100 mm △: The flow distance is 30 mm or more and less than 60 mm ×: The flow distance is less than 30 mm <Evaluation results> The above evaluation test The results are shown in Table 1. In addition, the numerical value in the brackets in the first table indicates the content (parts by mass) of each component with respect to 100 parts by mass of the content (solid content) of the fluororesin. [Table 1] As shown in the first table, the chloride ion concentration of the solution of the fluorine-containing resin of the examples is 50 ppm by mass or less. Therefore, the coating film immediately after film formation of the coating film produced by using the coating composition obtained by using the same is used. Excellent gloss. Further, the solution of the fluorine-containing resin of the examples was also excellent in storage stability. Further, according to the comparison of Examples 1 to 7, when the chloride ion concentration was 3 to 30 ppm by mass (Examples 4 and 5), the fluidity was also excellent. On the other hand, since the chloride ion concentration of the solution of the fluorine-containing resin of Comparative Example 1 and Comparative Example 3 exceeds 50 ppm by mass, the coating film immediately after film formation of the coating film produced by using the coating composition obtained by using the same The gloss is not sufficient. Here, in Comparative Example 1 and Comparative Example 3, the ratio of the amount of hydrotalcite to the amount of the amine group-containing compound when the fluororesin was polymerized was outside the range of 1 to 4. Therefore, it is considered that the amount of chlorine ions outside the system which is discharged as a solution of the fluorine-containing resin as the insoluble component together with the hydrotalcite becomes small, and the chloride ion concentration increases. Further, although the solution of the fluorine-containing resin of Comparative Example 2 has a low chloride ion concentration, it does not contain an amine group-containing compound, so storage stability is poor (the solution of the fluorine-containing resin gels after heating, and the fluorine resin cannot be measured. Mn). Further, gelation occurred when the coating composition obtained by using the solution of the fluorine-containing resin of Comparative Example 2 was produced, and the powder composition could not be produced, and the glossiness immediately after film formation could not be evaluated. The entire disclosure of Japanese Patent Application No. 2016-005279, filed on Jan.