1297705 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種聚對苯二甲酸丁二酯薄膜之製法，其 係以T型模頭法製造具有優越的膜厚均勻性、耐熱收縮性 之聚對苯二甲酸丁二酯薄膜之方法。 【先前技術】 聚對苯二甲酸丁二酯（PBT )樹脂係具有優越的機械性 強度、耐熱性、耐化學藥品性、耐衝擊性、電氣特性等性 質’因此一向是被用作爲工程用塑膠而受到注目，且使用 於汽車零組件、電氣•電子零組件等之射出成型模製品。 由於PBT也具有優越的氣體障壁性或保香性，如能製得具 有優越的膜厚均勻性或耐熱收縮性之薄的PBT薄膜，則可 用作爲包裝材料。然而，PBT卻有由於熔體張力低，以致 不能作快速延伸，且由於玻璃轉移溫度接近常溫，容易產 生薄膜皺紋等之難題。因此，如欲使PBT樹脂成型厚度爲 約10至30微米之程度且具有均勻厚度之理想的包裝用薄 膜，則是極爲困難。 薄膜之製造方法，雖然有T型模頭法與吹塑成型法，但 是一般與T型模頭法相比較，吹塑成型法係生產牲較高且 適合用以製造薄膜。然而，在以吹塑成型法所製得之PBT 薄膜，卻有膜厚均勻性不佳，且熱收縮率大之難題。 在藉由T型模頭法製造PBT薄膜時，藉由將從T型模頭 所擠壓出之熔融PBT樹脂加以冷卻所製得之未經延伸之薄 膜，欲能加以薄膜化同時也能改善機械性強度等理由而加 1297705 以延伸。對於藉由T型模頭法所製成之未延伸薄膜施加雙 軸向延伸以製造ΡΒΤ薄膜之方法，日本國專利特開昭第49 -8 051 7 8號公報已提案一種將熔融ΡΒΤ從Τ型模頭擠壓出 至6 5 °C之泠卻輥上，並將所製得之未延伸薄膜在ΡΒΤ之第 二轉移點溫度以上且比熔點低1 0 °C以上的低溫下同時進行 雙軸向延伸之方法。另外，在特公昭第5 1 - 40,904號公報 ，則已提案一種將所製得之未延伸薄膜先在PBT之第二轉 移點溫度以上且比熔點低1 0 °C以上的低溫下加以延伸，接 著在第一段之延伸溫度以上的溫度下朝與對於第一段延伸 方向呈正交的方向進行延伸之方法。另外，在特開昭第51 -146,5 72號公報則已提案一種從T型模頭擠壓出至例如30 °C之冷卻輥上，然後將所製得之未延伸薄膜首先以PBT之 玻璃轉移溫度以上至1 00 °C以下的溫度下朝橫向進行延伸 ，接著在比第一段延伸溫度高且在PBT之熔點以下的溫度 下朝縱向進行延伸之方法。 然而，在該等文獻中，由於其係將藉由使熔融PBT樹脂 加以驟冷所製得之未延伸薄膜加以雙軸向延伸，因此延伸 加工性不足，且所製得之薄膜的膜厚非均勻性和熱收縮率 大。欲能使得PBT薄膜之雙軸向延伸更加容易，雖然已有 與其他樹脂薄膜形成積層之方法，摻合聚乙烯、聚丙烯等 相容性良好的樹脂之方法等提案，但是任一種方法也不易 加以薄膜化至最適合用作爲包裝薄膜之約10至30微米程 度的膜厚。 【發明內容】 -6- 1297705 發明目的 因此，本發明之目的係提供一種具有優越的膜厚均勻性 和耐熱收縮性之聚對苯二甲酸丁二醋薄膜之製造方法。 發明槪述 有鑑於如上所述之目的，經專心硏究結果，本發明人等 發現：如將經從T型模頭所擠壓出之熔融聚對苯二甲酸丁 二酯樹脂之薄膜，在實質的未經延伸之狀態下加以徐冷以 使其結晶化後再加以延伸，則可製得具有優越的膜厚均句 性和耐熱收縮性之聚對苯二甲酸丁二酯薄膜而達成本發明 〇 換言之，本發明之聚對苯二甲酸丁 一酯薄膜之製造方法 ，其特徵爲將熔融聚對苯二甲酸丁二酯樹脂從T型模頭擠 壓出成薄膜狀，.將所製得之薄膜在實質的未延伸之狀態下 徐冷，以使該聚對苯二甲酸丁二酯樹脂結晶化，然後將所 製得之結晶化薄膜加以延伸。 未經延伸之聚對苯二甲酸丁二酯樹脂薄膜之徐冷較佳爲 在如上所述之聚對苯二甲酸丁二酯樹脂之結晶化溫度- 4〇 °C與結晶化溫度 + 20°C之間的溫度下進行。該未經延伸之 聚對苯二甲酸丁二酯樹脂薄膜之徐冷速度較佳爲設定在30 °C /秒鐘以下。如上所述之結晶化未延伸薄膜之厚度較佳爲 30至200微米。該結晶化未延伸薄膜較佳爲至少向縱向（ MD )加以延伸。該結晶化未延伸薄膜較佳爲在該聚對苯二 甲酸丁二酯樹脂之結晶化溫度一5 0 °C至結晶化溫度一1 〇 °C 的溫度下進行延伸。該延伸之倍率較佳爲1.5倍以上。 1297705 延伸薄膜較佳爲在如上所述之聚對苯二甲酸丁二酯樹脂 - 之結晶化溫度-ll〇°C至結晶化溫度一 50°c的溫度下進行「 再延伸」。該再延伸之倍率較佳爲1 · 1倍以上。再延伸薄 膜也可在室溫至該聚對苯二甲酸丁二酯樹脂之玻璃轉移溫 度之範圍內的溫度下進行「冷延伸」。該冷延伸之倍率較 佳爲1 · 1倍以上。如上所述之聚對苯二甲酸丁二酯樹脂較 佳爲相對於樹脂全體100質量％爲基準，含有5至15質量’ %之聚烯烴和/或彈性體。 【實施方式】 Φ 本發朋之最佳實施形態 〔1〕 聚對苯二甲酸丁二酯薄膜樹脂 對於作爲原料的聚對苯二甲酸丁二酯（PBT )樹脂，雖 然並無特殊限制，但是較佳爲以1，4 - 丁二醇與對苯二甲 、 酸作爲構成成份之均聚物所製得者。但是也可在不致於損 ， 及熱收縮性等物理性質之範圍內含有1，4 - 丁二醇以外之 二醇成份，或對苯二甲酸以外之羧酸成份作爲共聚合成份 。該等「二醇」成份係包括例如：乙二醇、二伸乙甘醇、 Φ 新戊二醇、1，4 -環己烷甲醇等。「二羧酸」成份係包括 例如：間苯二甲酸、癸二酸、己二酸、壬二酸、丁二酸等 。較佳的PBT樹脂之具體實例則有例如售自東麗（Toray) 公司，商品名爲「Torecon」之均質PBT樹脂。 PBT樹脂係不限定於只由PBT所製成之情況，也可在不 致於抑制本發明效果之範圍內根據目的而含有其他之熱塑 性樹脂。其他之熱塑性樹脂係包括：聚對苯二甲酸乙二酯 1297705 (PET)、聚萘二甲酸乙二酯（PEN)等之聚酯；聚苯硫醚 (PPS );聚醯胺（PA);聚醯亞胺（PI );聚醯胺醯亞 胺（PAI);聚醚 （PES):聚醚醚酮（PEEK);聚碳酸 酯；聚胺甲酸酯；氟樹脂；聚乙烯、聚丙烯等之聚烯烴； 聚氯乙烯；彈性體等。特別是PBT樹脂含有聚乙烯、聚丙 烯等之聚烯烴和/或彈性體時，則由於熔體黏度和熔體張力 會變高，因此使得延伸加工性提高，同時所製得之薄膜的 機械強度或熱密封性提高，因此較佳。其中PBT樹脂係以 含有聚乙烯者爲較佳。若含有其他之熱塑性樹脂時，則其 比率以樹脂全體爲100質量％爲基準時，則較佳爲5至15 質量％，更佳爲5至1 0質量％。因此，除非另外有特別註 明，在本說明書中所使用之術語「聚對苯二甲酸丁二酯」 ，可理解不僅爲PBT單體，且包含PBT +其他之熱塑性 樹脂的組成物兩者。 在PBT樹脂，也可根據要求性能而適當地使用添加於泛 用熱塑性樹脂和熱固性樹脂之習知的添加劑，亦即例如： 塑化劑、抗氧化劑或紫外線吸收劑等之安定劑、抗靜電劑 、界面活性劑、染料或顏料等之著色劑、用以改善流動性 之潤滑劑、結晶化促進劑（成核結晶劑）和無機塡充劑等 〇 〔2〕 PBT薄膜之製造方法 第1圖係展示本發明之根據T型模頭法製造PBT薄膜的 裝置之一實例。將熔融PBT樹脂從T型模頭擠壓出所製得 之擠製薄膜5，係藉由加熱流延輥1牽引而徐冷以形成結 1297705 晶化未延伸薄膜6。所製得之結晶化未延伸薄膜6將在加 熱流延輥1與設置成與其呈平行的第二輥2之間加以延伸 後，藉由導輥9以捲取軸8加以捲取。 (a ) 結晶化未延伸薄膜之形成 (i ) 熔融捏合步驟 首先將PBT樹脂與如上所述〔1〕所提及之添加劑加以 熔融捏合，以調製熔融PBT樹脂。熔融捏合之方法並無特 殊限制，但是通常採用在雙螺桿擠壓機中均勻地混合之方 法。捏合溫度較佳爲在PBT樹脂之熔點+ 1〇。(：與熔點+ 4 0 °C之間。若將捏合溫度設定在高於PBT樹脂之熔點 + 40 °C時，則有會發生樹脂之熱降解的顧慮。因此，若在擠 壓機中進行捏合時，則應使用具有不會發熱的螺桿結構， 或是具有適當的冷卻裝置者。捏合溫度之下限値若設定爲 低於PBT樹脂之熔點+ l〇t時，則由於擠壓出量將趨於 不穩定，係爲不佳。例如PBT樹脂爲均聚物時，則由於其 熔點爲約220至230°C，因此捏合溫度應設定在23 0至270 °C。熔點係根據ASTM D459 1所測得者（以下同）。 將經捏合的熔融PBT樹脂以直接或藉由其他擠壓機從τ 型模頭7擠壓出，或一旦加以冷卻使其酯粒化後再藉由擠 壓機從T型模頭7擠壓出。T型模頭7之間隙通常設定爲5 毫米以下。從T型模頭7所擠壓出的樹脂溫度較佳爲在 PBT樹脂之熔點一 10°C至熔點+ 3(TC，更佳爲PBT樹脂 之熔點至熔點 + l〇°C。 (i〇 徐冷步驟 1297705 藉由將熔融PBT樹脂從T型模頭7擠壓出所製得之擠製 薄膜5，係以加熱流延輥1接受，並以輥丨使其徐冷以形 成結晶化未延伸薄膜6。由於藉由形成結晶化未延伸薄膜6 即能提高對於延伸之加工性，因此將其以延伸使其薄膜化 時’則比使用非晶質之未延伸薄膜加以薄膜化之情形，可 使得膜厚之非均勻性減少。 加熱流延輥1較佳爲設定在ΡΒΤ樹脂之結晶化溫度一 40 °C與結晶化溫度+ 2(TC之間的溫度。在此之術語「結晶化 溫度」，係意謂在250°C熔融試料後，以20°C /分鐘之速率 進行降溫時，可由微差掃描熱量測定儀（DSC )所檢測得 之結晶化尖峰溫度。例如，PBT樹脂爲均聚物時，則其結 晶化溫度爲約170至190 °C。經接觸到該溫度範圍的加熱 流延輥1之擠製薄膜5，將徐冷至PBT樹脂之結晶化溫度 —40°C與結晶化溫度 + 2(TC之間的溫度。 若輥1爲高於PBT樹脂之結晶化溫度 + 2〇°C的溫度時 ，則所製得之未延伸薄膜6將不會結晶化。反之，若輥1 爲低於PBT樹脂之結晶化溫度-40 °C的溫度時，則由於濟 製薄膜5之冷卻速度太快，以致所製得之未延伸薄膜6之 結晶化度太低，因此延伸加工性也低。擠製薄膜5更佳胃 徐冷至PBT樹脂之結晶化溫度一 35°C與結晶化溫度 + 1() °C之間的溫度。 若在T型模頭7與加熱流延輥1之間未設置加熱裝置時 ，則欲能確保足夠的徐冷速度，應儘量縮短T型模頭7 _ 加熱流延輥1之間的距離，具體而言，較佳爲2 0公分以γ 1297705 徐冷速度較佳爲30°C/秒鐘以下，更佳爲20°C/秒鐘以下 ，且特佳爲1 〇 °C /秒鐘以下。因爲擠製薄膜5若不經過徐冷 即不會徹底地結晶化。徐冷之下限雖然並無特殊限制，f旦 是從生產性之觀點來考量，則較佳爲0.3 °C /秒鐘。 欲能使得在後續步驟之延伸容易進行，較佳爲將結晶化 未延伸薄膜6之厚度設定在30至200微米，且更佳爲設定 在35至100微米。欲能使得結晶化未延伸薄膜6之厚度爲 30至200微米，且欲能抑制在形成結晶化未延伸薄膜6時 之頸縮現象〔流延於加熱流延輥1之薄膜會變得比T型模 參 頭7之有效寬度爲窄之現象〕，則較佳爲應設定加熱流延 輥1之周速爲5至20公尺/分鐘，且更佳爲設定在5至16 公尺/分鐘。加熱流延輥1之直徑較佳爲3 5至70公分。必 要時也可設置數個加熱流延輥1。在此種情形下，則各加 熱流延輥1之周速應設定爲相同，但是各加熱流延輥1之 溫度則可爲相同，或是也可使其愈往下游，則在PBT樹脂 之結晶化溫度- 40°C與結晶化溫度+ 20°C之範圍內依序使 其降低。 (b ) 延伸 (〇 延伸步驟 如第1圖所展示，所製得之結晶化未延伸薄膜6，係在 加熱流延輥1與第二輥2之間設定周速差以朝縱向（MD ) 進行延伸。結晶化未延伸薄膜6較佳爲在PBT樹脂之結晶 化溫度一50 °C至結晶化溫度—1〇。(：的溫度下進行延伸，藉 1297705 此即可使熔體張力控制成適合較高倍率之延伸範圍，因此 胃實現膜厚變動率較少之均勻延伸。延伸溫度更佳爲設定 在PBT樹脂之結晶化溫度一 “艽與結晶化溫度一 ”。(^之間 的溫度。結晶化未延伸薄膜6會受到延伸之區域（延伸區 域）61，係在加熱流延輥〗與第二輥2之間，因此較佳爲 應使輥間距離（兩輥在共同切線上之兩切點之間的距離） 設定爲10公分以下，以使延伸區域61會成爲如上所述之 較佳的延伸溫度範圍。使輥間距離設定爲1 0公分以下，即 可使延伸區域61變得較狹窄，藉此即可更有效地抑制頸縮 現象。欲能使得延伸區域之溫度保持成恆定，也可在兩輥 之間使用加熱器等來加熱結晶化未延伸薄膜6。經延伸之 薄膜較佳爲在第二輥2冷卻至PBT樹脂之結晶化溫度-1 40°C以下。藉此即可使延伸狀態穩定化。 延伸倍率係視結晶化未延伸薄膜6之厚度而有所不同， 但是較佳爲設定在1.5倍以上，更佳爲設定在1.8至4倍。 延伸倍率愈高，則透明性愈高。適當地設定加熱流延輥1 與第二輥2之周速比，藉此則可延伸成吾所欲之倍率。第 二輥2之外徑並無特殊限制，設定在與加熱流延輥1相同 的35至70公分即可。 (ϋ )再延伸步驟 藉由如上所述（i )之步驟的延伸薄膜，係也可朝縱向再 延伸，藉此即可使透明性更進一步提高，同時可更進一步 薄膜化。第2圖係展示經延伸後實施再延伸步驟的裝置t 一實例。該裝置係除在輥2之上方設置夾輥1 0，同時在輥 -13- 1297705 2與輥9之間插裝一對輥3、1 〇以外，其餘則與第丨圖相 同。在下文中即以一對輥3、1 0之作用爲主加以說明。 再延伸係在第2圖所示裝置之第二輥2與第三輥3之間 設定周速差來實施。位於第二輥2與第三輥3之間的延伸 區域62之溫度較佳爲設定在ρβτ樹脂之結晶化溫度- 110 °(：與結晶化溫度一 50°C之間的範圍，更隹爲ΡΒΤ樹脂之結 晶化溫度- 90 °C與結晶化溫度-50 °C之間的範圍。欲能使 得延伸區域62之溫度符合如上所述之較佳範圍，則較佳爲 以第二輥2在PBT樹脂之結晶化溫度- 90 °C與結晶化溫度 一 3 0°C之間的溫度下處理藉由如上所述（i)之步驟所製得 之延伸薄膜1 1，同時將第二輥2與第三輥3之輥間距離設 定爲10公分以下。使用第二輥2之處理溫度較佳爲在PBT 樹脂之結晶化溫度- 8〇 °C與結晶化溫度—40 之間的範圍 。再延伸薄膜1 2較佳爲以第三輥3冷卻至PBT樹脂之結 晶化溫度一 140 °C以下。第三輥3之直徑係採用與第二輥2 相同之35至70公分即可。再延伸之倍率較佳爲K1倍以 上，更佳爲1.3至3倍。 (iii) 冷延伸步驟 再延伸薄膜可再進一步朝縱向施加冷延伸。第3圖係展 示在經再延伸步驟後實施冷延伸步驟的裝置之一實例。該 裝置係除在輥3與輕9之間插裝一對輥4、10以外，其餘 則與第2圖之裝置相同。因此，以一對輥4、1 〇之作用爲 主加以說明。冷延伸係在第3圖所示之第三輥3與第四輥 4之間設定周速差來實施。位於第三輥3與第四輥4之間 1297705 的延伸區域63之溫度較佳爲設定在室溫與PBT樹脂之玻 璃轉移溫度（Tg )之間的範圍。玻璃轉移溫度Tg係根據 JIS K7 12 1所測得者。均質PBT樹脂之Tg —般爲22至45 °C。欲能使得延伸區域63之溫度符合如上所述之較佳範圍 ，則較佳爲以第三輥3在PBT樹脂之結晶化溫度- 110°C 與結晶化溫度-8 0 °C之間的溫度下處理再延伸薄膜1 2，同 時將第三輥3與第四輥4之輥間距離設定爲1 0公分以下。 使用第三輥3之處理溫度較佳爲在PBT樹脂之結晶化溫度 —140 °C與結晶化溫度-90 °C之間的範圍。經施加如此之冷 延伸即可更進一步提高薄膜之透明性。第四輥4之直徑係 採用與第三輥3相同之35至70公分即可。再延伸之倍率 較佳爲1.1倍以上，更佳爲1.3至3倍。 (i v )其他之模式 也可使用第2圖所示之裝置，僅實施如上所述（i )之延 伸步驟。在此種情形下，例如，邊使第三輥3與第二輥2 相同周速下旋轉，邊使延伸薄膜11冷卻至PBT樹脂之結 晶化溫度- 1 40 °C以下，即可以更長時間來實施冷卻處理。 而且，以第三輥3實施冷卻處理時，也可增設以第二輥2 在高於PBT樹脂之玻璃轉移溫度（Tg)與結晶化溫度—10 °C以下之間的溫度下將延伸薄膜1 1加以驟冷之步驟，藉此 即可更進一步提高所製得之PBT薄膜之耐熱收縮性。 也可使用第3圖所示之裝置，使延伸執行至如上所述（ ii )之再延伸步驟。在此種情形下，如將第四輥4作爲冷 卻之用，則可以更長時間來實施對於再延伸薄膜1 2之冷卻1297705 IX. Description of the Invention: [Technical Field] The present invention relates to a method for producing a polybutylene terephthalate film which is manufactured by a T-die method and has excellent film thickness uniformity and heat shrinkage resistance. A method of polybutylene terephthalate film. [Prior Art] Polybutylene terephthalate (PBT) resin has excellent mechanical strength, heat resistance, chemical resistance, impact resistance, electrical properties, etc. 'It has always been used as engineering plastics. It is attracting attention and is used for injection molding of automotive parts, electrical and electronic components. Since PBT also has superior gas barrier properties or aroma retention properties, it can be used as a packaging material if a thin PBT film having superior film thickness uniformity or heat shrinkage resistance can be obtained. However, PBT has a low melt tension, so that it cannot be rapidly extended, and since the glass transition temperature is close to normal temperature, it is easy to cause film wrinkles and the like. Therefore, it is extremely difficult to form a PBT resin into a film for packaging which has a thickness of about 10 to 30 μm and a uniform thickness. Although the T-die method and the blow molding method are used for the production method of the film, the blow molding method is generally superior to the T-die method, and is suitable for producing a film. However, the PBT film produced by the blow molding method has a problem that the film thickness uniformity is poor and the heat shrinkage rate is large. When the PBT film is manufactured by the T-die method, the unstretched film obtained by cooling the molten PBT resin extruded from the T-die is intended to be thinned and improved. For mechanical strength and other reasons, add 1297705 to extend. For the method of manufacturing a tantalum film by applying a biaxial extension to an unstretched film produced by a T-die method, Japanese Laid-Open Patent Publication No. SHO 49-051 051 7.8 proposes a method of melting a crucible. The die is extruded onto a roll of 65 ° C and the unstretched film is simultaneously doubled at a low temperature above the second transfer point of the crucible and at a temperature lower than the melting point by more than 10 ° C. The method of axial extension. Further, in Japanese Patent Publication No. 5-40-904, it is proposed to extend the obtained unstretched film at a low temperature which is higher than the second transfer point temperature of PBT and lower than the melting point by 10 ° C or higher. Next, a method of extending in a direction orthogonal to the direction in which the first segment extends is performed at a temperature above the extension temperature of the first segment. Further, in Japanese Laid-Open Patent Publication No. 51-146, No. 5, 72, a squeezing roll from a T-die to a cooling roll of, for example, 30 ° C has been proposed, and then the obtained unstretched film is firstly PBT. The glass transition temperature is extended to a lateral direction at a temperature of up to 100 ° C or less, and then extended in a longitudinal direction at a temperature higher than the first stage extension temperature and below the melting point of PBT. However, in these documents, since the unstretched film obtained by quenching the molten PBT resin is biaxially stretched, the elongation processability is insufficient, and the film thickness of the obtained film is not Uniformity and heat shrinkage rate are large. In order to make the biaxial stretching of the PBT film easier, although a method of laminating with other resin films and a method of blending a resin having good compatibility such as polyethylene and polypropylene are proposed, any method is not easy. It is thinned to a film thickness of about 10 to 30 μm which is most suitable for use as a packaging film. SUMMARY OF THE INVENTION -6 - 1297705 OBJECT OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for producing a polybutylene terephthalate film having superior film thickness uniformity and heat shrink resistance. In view of the above-described objects, the inventors have found that, as a result of intensive investigation, a film of a molten polybutylene terephthalate resin extruded from a T-die is used. The material can be crystallized and then extended without being stretched in a substantially unstretched state, thereby obtaining a polybutylene terephthalate film having excellent film thickness uniformity and heat shrink resistance. In other words, the method for producing a polybutylene terephthalate film of the present invention is characterized in that a molten polybutylene terephthalate resin is extruded from a T-die into a film shape. The obtained film was cooled in a substantially unstretched state to crystallize the polybutylene terephthalate resin, and then the obtained crystallized film was stretched. The uncooled polybutylene terephthalate resin film is preferably cooled at a crystallization temperature of 4 ° C and a crystallization temperature of 20 ° of the polybutylene terephthalate resin as described above. Performed at a temperature between C. The uncooled polybutylene terephthalate resin film preferably has a cooling rate of 30 ° C /sec or less. The thickness of the crystallized unstretched film as described above is preferably from 30 to 200 μm. Preferably, the crystallized unstretched film extends at least in the machine direction (MD). The crystallized unstretched film is preferably extended at a temperature at which the crystallization temperature of the polybutylene terephthalate resin is from 50 ° C to a crystallization temperature of 1 ° C. The magnification of the extension is preferably 1.5 times or more. The 1297705 stretched film is preferably "re-stretched" at a temperature of from crystallization temperature - ll ° C to crystallization temperature of 50 ° C of the polybutylene terephthalate resin as described above. The magnification of the re-expansion is preferably 1.1 times or more. The re-stretching film can also be "cold stretched" at a temperature ranging from room temperature to the glass transition temperature of the polybutylene terephthalate resin. The cold stretching ratio is preferably more than 1.1 times. The polybutylene terephthalate resin as described above preferably contains 5 to 15% by mass of the polyolefin and/or elastomer based on 100% by mass of the total resin. [Embodiment] Φ The best embodiment of the present invention [1] Polybutylene terephthalate film resin The polybutylene terephthalate (PBT) resin as a raw material is not particularly limited, but It is preferably prepared by using 1,4 - butanediol with terephthalic acid and acid as a homopolymer of a constituent component. However, it is also possible to contain a diol component other than 1,4-butanediol or a carboxylic acid component other than terephthalic acid as a copolymer component in the range of physical properties such as loss and heat shrinkage. The "diol" components include, for example, ethylene glycol, diethylene glycol, Φ neopentyl glycol, 1,4-cyclohexane methanol, and the like. The "dicarboxylic acid" component includes, for example, isophthalic acid, sebacic acid, adipic acid, sebacic acid, succinic acid, and the like. Specific examples of preferred PBT resins are, for example, homogenous PBT resins sold by Toray Corporation under the trade name "Torecon". The PBT resin is not limited to the case of being made only of PBT, and other thermoplastic resins may be contained depending on the purpose within the range not inhibiting the effects of the present invention. Other thermoplastic resins include polyesters such as polyethylene terephthalate 1297705 (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), and polydecylamine (PA); Polyimine (PI); polyamidoximine (PAI); polyether (PES): polyetheretherketone (PEEK); polycarbonate; polyurethane; fluororesin; polyethylene, polypropylene Polyolefins; polyvinyl chloride; elastomers, etc. In particular, when the PBT resin contains a polyolefin and/or an elastomer such as polyethylene or polypropylene, the melt viscosity and the melt tension become high, so that the elongation processability is improved and the mechanical strength of the obtained film is improved. Or the heat sealability is improved, so it is preferred. Among them, PBT resin is preferred to contain polyethylene. When the other thermoplastic resin is contained, the ratio is preferably from 5 to 15% by mass, more preferably from 5 to 10% by mass, based on 100% by mass of the total of the resin. Therefore, the term "polybutylene terephthalate" as used in this specification, unless otherwise specifically noted, is understood to mean not only a PBT monomer but also a composition of PBT + other thermoplastic resins. In the PBT resin, a conventional additive added to a general-purpose thermoplastic resin and a thermosetting resin, that is, a stabilizer such as a plasticizer, an antioxidant or an ultraviolet absorber, or an antistatic agent can be suitably used depending on the required properties. a coloring agent such as a surfactant, a dye or a pigment, a lubricant for improving fluidity, a crystallization accelerator (nucleating crystallizing agent), an inorganic chelating agent, etc. [2] A method for producing a PBT film. An example of a device for producing a PBT film according to the T-die method of the present invention is shown. The extruded PBT resin was extruded from a T-die and the resulting extruded film 5 was drawn by heating the casting roll 1 to form a knot 1297705 crystallized unstretched film 6. The obtained crystallized unstretched film 6 is stretched between the heating casting roll 1 and the second roll 2 disposed in parallel thereto, and then taken up by the take-up shaft 8 by the guide rolls 9. (a) Formation of crystallized unstretched film (i) Melt kneading step First, the PBT resin is melt-kneaded with the additive mentioned in [1] above to prepare a molten PBT resin. The method of melt-kneading is not particularly limited, but a method of uniformly mixing in a twin-screw extruder is usually employed. The kneading temperature is preferably + 1 Torr at the melting point of the PBT resin. (: between the melting point + 40 ° C. If the kneading temperature is set higher than the melting point of the PBT resin + 40 ° C, there is a concern that thermal degradation of the resin may occur. Therefore, if it is carried out in an extruder When kneading, use a screw structure that does not generate heat, or a suitable cooling device. If the lower limit of the kneading temperature is set to be lower than the melting point of the PBT resin + l〇t, the amount of extrusion will be It tends to be unstable and is not good. For example, when the PBT resin is a homopolymer, since the melting point is about 220 to 230 ° C, the kneading temperature should be set at 23 0 to 270 ° C. The melting point is according to ASTM D459 1 The measured (hereinafter the same). The kneaded molten PBT resin is extruded from the τ-type die 7 directly or by another extruder, or once cooled, the ester is granulated and then extruded. The machine is extruded from the T-die 7. The gap of the T-die 7 is usually set to be less than 5 mm. The temperature of the resin extruded from the T-die 7 is preferably 10 ° C at the melting point of the PBT resin. To the melting point + 3 (TC, more preferably the melting point of the PBT resin to the melting point + l〇 ° C. (i〇 Xu cold step 1297705 by The melted PBT resin is extruded from the T-die 7 to produce the extruded film 5, which is heated by a casting roll 1 and quenched by a roll to form a crystallized unstretched film 6. The crystallized unstretched film 6 can improve the processability for stretching, so that when it is stretched to be thinned, it is thinner than the amorphous unstretched film, and the film thickness can be made non-uniform. The heating casting roll 1 is preferably set to a temperature between the crystallization temperature of the resin of 40 ° C and the crystallization temperature + 2 (TC). The term "crystallization temperature" herein means 250. °C When the sample is melted at a rate of 20 ° C / min, the crystallization peak temperature can be detected by a differential scanning calorimeter (DSC). For example, when the PBT resin is a homopolymer, the crystal is crystallized. The temperature is about 170 to 190 ° C. The extruded film 5 of the heated casting roll 1 which is in contact with this temperature range is cooled to a crystallization temperature of 40 ° C and a crystallization temperature of the PBT resin + 2 (TC Temperature between rolls. If roll 1 is higher than the crystallization temperature of PBT resin + 2 ° ° C At the temperature, the unstretched film 6 produced will not be crystallized. Conversely, if the roll 1 is at a temperature lower than the crystallization temperature of the PBT resin of -40 ° C, the cooling rate of the film 5 is too high. So that the degree of crystallization of the unstretched film 6 produced is too low, so the elongation processability is also low. The extruded film 5 is better cooled to the crystallization temperature of the PBT resin by a temperature of 35 ° C and the crystallization temperature + Temperature between 1 () ° C. If there is no heating device between the T-die 7 and the heating casting roller 1, it is necessary to ensure a sufficient cooling rate, and the T-die 7 should be shortened as much as possible. The distance between the heating casting rolls 1 is specifically 20 cm, preferably γ 1297705, and the cooling rate is preferably 30 ° C / sec or less, more preferably 20 ° C / sec or less. Good for 1 〇 ° C / second. Since the extruded film 5 does not completely crystallize unless it is cooled. Although the lower limit of Xu Lengzhi is not particularly limited, it is preferably 0.3 ° C / sec from the viewpoint of productivity. In order to facilitate the extension of the subsequent step, it is preferred to set the thickness of the crystallized unstretched film 6 to 30 to 200 μm, and more preferably to 35 to 100 μm. It is desirable to make the thickness of the crystallized unstretched film 6 30 to 200 μm, and to suppress the necking phenomenon when the crystallized unstretched film 6 is formed [the film which is cast on the heating casting roll 1 becomes T Preferably, the circumferential speed of the heating casting roll 1 is set to 5 to 20 meters per minute, and more preferably set to 5 to 16 meters per minute. . The diameter of the heating casting roll 1 is preferably from 35 to 70 cm. It is also possible to provide a plurality of heating casting rolls 1 as necessary. In this case, the circumferential speed of each of the heating casting rolls 1 should be set to be the same, but the temperature of each of the heating casting rolls 1 may be the same, or it may be further downstream, then in the PBT resin. The crystallization temperature is lowered in the range of 40 ° C and the crystallization temperature + 20 ° C in order. (b) Extension (〇 extension step as shown in Fig. 1, the obtained crystallized unstretched film 6 is set between the heating casting roll 1 and the second roll 2 to set the circumferential speed difference to the longitudinal direction (MD) The crystallization of the unstretched film 6 is preferably carried out at a temperature of from 50 ° C to a crystallization temperature of the PBT resin of -1 〇 at a temperature of 1,297705 to control the melt tension to It is suitable for the extension range of higher magnification, so the stomach achieves a uniform extension of the film thickness variation rate. The extension temperature is more preferably set to the crystallization temperature of the PBT resin - "艽 and crystallization temperature one". The crystallized unstretched film 6 is subjected to an extended region (extension region) 61 between the heated casting roll and the second roll 2, so it is preferable to make the distance between the rolls (the two rolls are on a common tangent line). The distance between the two tangent points is set to be 10 cm or less so that the extended region 61 becomes a preferable extended temperature range as described above. By setting the inter-roller distance to 10 cm or less, the extended region 61 can be made It is narrower, so that it can suppress the neck more effectively In order to keep the temperature of the extended region constant, a crystallizer or the like may be used between the two rolls to heat the crystallized unstretched film 6. The stretched film is preferably cooled to the PBT resin in the second roll 2. The crystallization temperature is ～40° C. or lower, whereby the extended state can be stabilized. The stretching ratio varies depending on the thickness of the crystallized unstretched film 6, but is preferably set to 1.5 times or more, more preferably The setting is 1.8 to 4. The higher the stretching ratio, the higher the transparency. The peripheral speed ratio of the heating casting roll 1 and the second roller 2 is appropriately set, thereby extending the desired magnification. The outer diameter of the roller 2 is not particularly limited and may be set to be 35 to 70 cm which is the same as that of the heating casting roller 1. (ϋ) The extension step may be carried out by the stretching film of the step (i) as described above. Further extending in the longitudinal direction, thereby further improving the transparency and further thinning. Fig. 2 shows an example of a device t which is subjected to an extension step after extension. The device is placed above the roller 2. Set the nip roller 10, while at the roller -13 - 1297705 2 and roller 9 The other ones are the same as the first drawing except that a pair of rollers 3 and 1 are interposed. In the following, the action of a pair of rollers 3 and 10 is mainly explained. The extension is the same as that of the device shown in Fig. 2. The circumferential speed difference is set between the two rolls 2 and the third roll 3. The temperature of the extended region 62 between the second roll 2 and the third roll 3 is preferably set at a crystallization temperature of -110 ° of the ρβτ resin ( The range between the crystallization temperature and 50 ° C is more the range between the crystallization temperature of the enamel resin - 90 ° C and the crystallization temperature - 50 ° C. The temperature of the extended region 62 is required to be as above. The preferred range is preferably treated by the second roll 2 at a temperature between the crystallization temperature of the PBT resin of -90 ° C and the crystallization temperature of 30 ° C by the above (i) The stretch film 1 1 obtained in the step is set to have a distance between the rolls of the second roll 2 and the third roll 3 of 10 cm or less. The treatment temperature using the second roll 2 is preferably in the range of the crystallization temperature of the PBT resin - 8 ° C and the crystallization temperature - 40. The re-stretching film 12 is preferably cooled by the third roll 3 to a crystallization temperature of 140 ° C or less of the PBT resin. The diameter of the third roller 3 may be 35 to 70 cm which is the same as that of the second roller 2. The magnification of the re-expansion is preferably K1 or more, more preferably 1.3 to 3 times. (iii) Cold Extension Step The re-stretching film can be further applied with a cold extension in the longitudinal direction. Figure 3 shows an example of a device that performs a cold stretching step after the re-extension step. This apparatus is the same as the apparatus of Fig. 2 except that a pair of rolls 4, 10 are interposed between the rolls 3 and the light 9. Therefore, the action of the pair of rollers 4, 1 为 will be mainly described. The cold extension is carried out by setting a peripheral speed difference between the third roller 3 and the fourth roller 4 shown in Fig. 3 . The temperature of the extended region 63 of 1297705 between the third roller 3 and the fourth roller 4 is preferably set to a range between room temperature and the glass transition temperature (Tg) of the PBT resin. The glass transition temperature Tg is measured according to JIS K7 12 1. The Tg of the homogeneous PBT resin is generally 22 to 45 °C. In order to make the temperature of the extended region 63 conform to the above preferred range, it is preferred that the third roller 3 has a temperature between the crystallization temperature of the PBT resin of -110 ° C and the crystallization temperature of -80 ° C. The film 1 2 is processed and the distance between the rolls of the third roll 3 and the fourth roll 4 is set to be 10 cm or less. The treatment temperature using the third roll 3 is preferably in the range between the crystallization temperature of the PBT resin - 140 ° C and the crystallization temperature - 90 ° C. The transparency of the film can be further improved by applying such a cold extension. The diameter of the fourth roller 4 is 35 to 70 cm which is the same as that of the third roller 3. The magnification for re-expansion is preferably 1.1 times or more, more preferably 1.3 to 3 times. (i v ) Other modes It is also possible to use the apparatus shown in Fig. 2 to carry out only the stretching step of (i) as described above. In this case, for example, while the third roll 3 and the second roll 2 are rotated at the same peripheral speed, the stretched film 11 is cooled to a crystallization temperature of -1 40 ° C or less of the PBT resin, which is longer. To carry out the cooling process. Further, when the third roller 3 is subjected to the cooling treatment, the extension film 1 may be additionally added at a temperature higher than the glass transition temperature (Tg) of the PBT resin and the crystallization temperature of -10 ° C or lower. 1 The step of quenching can further improve the heat shrinkage resistance of the obtained PBT film. It is also possible to use the apparatus shown in Fig. 3 to extend the extension to the re-expansion step of (ii) as described above. In this case, if the fourth roll 4 is used for cooling, the cooling of the re-stretch film 12 can be carried out for a longer time.
處理。另外，以第四輥4實施冷卻處理時，也可增設以第 三輥3在高於PBT樹脂之玻璃轉移溫度（Tg)與結晶化溫度 一 1 〇°C以下之間的溫度下將延伸薄膜1 1加以驟冷之步驟。 (v ) 橫延伸步驟 對於藉由如上所述之（i)至（iv)中任一步驟所製得之 PBT薄膜，也可緊接著朝橫向（TD )施加延伸。施加橫延 伸之步驟可使用拉幅法等習知的方法。 (e ) 熱處理 藉由如上所述所製得之PBT薄膜係已經具有比以先前，製 · 造方法所能製得者具有更優越的耐熱收縮性，但是欲能進 一步提高耐熱收縮性，也可再進一步施加熱處理。熱處理 方法可使用「熱固定處理」或「熱收縮處理」中任一者。 該等熱處理較佳爲在介於高於PBT薄膜之Tg與結晶化溫 度- 10它以下之間的溫度下進行。 「熱固定處理」係以拉幅方法、輥方法或以輥壓方法實 施。至於「熱收縮處理」係以拉幅方法、輥方法、壓延方 法，或是以皮帶輸送機方法或浮動方法實施即可。 ® 〔3〕PBT薄膜 藉由如上所述所製得之PBT薄膜係呈半透明至透明，且 若與先前之單軸向延伸薄膜相比較，其係也具有優越的膜 厚均勻性和耐熱收縮性。具體而言，平均膜厚爲8至20微 米之薄膜的膜厚差爲1至3微米，熱收縮率在MD (縱向 )爲0.3 %以下，在TD (橫向）爲0.5 %以下。因此，可 用以形成不勻度較少的印刷層或金屬蒸鍍層。而且，在進 -16- 1297705 行熱密封、印刷等二次加工時，薄膜尺寸之變化也較少。 「平均膜厚」係將PBT薄膜寬度方向之中心部和兩端部之 厚度分別測定2點，總共6點所測得之値的平均値。「膜 厚差」係將PBT薄膜寬度方向之中心部和兩端部之厚度分 別測定2點，總共6點，然後計算得其中最大値與最小値 之差値。此値愈小，則愈能獲得良好結果。又所謂「熱收 縮率」係將PBT薄膜在150°C下暴露爲期10分鐘後，分別 測定其MD和TD之收縮率所測得之値。 根據本發明之製造方法所製得之PBT薄膜，必要時也可 與其他之薄膜作積層化。 本發明係藉由如下所述實施例作更詳細說明，但是本發 明並不受限於此等實施例。 實施例1 將PBT樹脂（商品名：Torecon「1 200S」，東麗（Toray )公司（股）製，熔點：220°C ;玻璃轉移溫度：22°C ;結 晶化溫度：182°C )進料至雙螺桿擠壓機（螺桿徑：300毫 米，擠壓量：50公斤/小時），在235 ±5 °C進行熔融捏合 ，在擠壓機中調製熔融PBT樹脂。然後使用第3圖所示之 裝置，從設置在擠壓機前端之T型模頭7擠壓出該熔融 PBT樹脂，並在調溫成17(TC之旋轉加熱流延輥1 (周速： 1 〇公尺/分鐘，輥徑：5 0公分）上加以接受。將擠製薄膜5 在加熱流延輥1上以9°C /秒鐘之速度使其徐冷，以形成平 均膜厚爲50微米之結晶化未延伸薄膜6。 然後，將所製得之結晶化未延伸薄膜6，在加熱流延輥1 -17- 1297705 與調溫成130°C之第二輥2 (周速：2〇公尺/分鐘）之間（ - 輕間距離：5公分）加以延伸2倍。將所製得之延伸薄膜 11在第二輥2與調溫成“它之第三輥3(周速：40公尺/ 分鐘）間（輕間距離：5公分）加以再延伸2倍。將所製 得之再延伸薄膜1 2以調溫成3 5艽之第四輥4 (周速：4 0 公尺/分鐘）加以冷卻，以製得平均膜厚爲13微米之PBT 薄膜13。經測定所製得之ΡΒΊΓ薄膜13之膜厚差及熱收縮 率結果，膜厚差爲2微米，縱向之熱收縮率爲〇1 %，橫向 之熱收縮率爲0.2 %。 φ 實施例2 除將加熱流延輥1之溫度設定在150°C，周速設定爲15 公尺/分鐘，徐冷速度爲18°C /秒鐘，且使用第2圖所示之 裝置以外’其餘則與實施例1同樣地形成平均膜厚爲40微 - 米之結晶化未延伸薄膜6。然後，將所製得之結晶化未延 ^ 伸薄膜6，在加熱流延輥1與調溫成1 〇〇 °c之第二輥2 (周 速：3 0公尺/分鐘）之間（輥間距離·· 5公分）加以延伸2 倍。將所製得之延伸薄膜1 1以調溫成3 5 °C之第三輥3 (周 · 速：30公尺/分鐘）加以冷卻，以製得平均膜厚爲20微米 之PBT薄膜13。經測定所製得之PBT薄膜13之膜厚差及 熱收縮率結果，膜厚差爲2微米，縱向之熱收縮率爲〇. 1 % ，橫向之熱收縮率爲0.15 %。 奮施例3 除將加熱流延輥1之溫度設定在180°C，周速設定爲15 公尺/分鐘，徐冷速度爲12 °C /秒鐘以外，其餘則與實施例 -18- 1297705 ， . 1同樣地形成平均膜厚爲40微米之結晶化未延伸薄膜6。 - 然後，將所製得之結晶化未延伸薄膜6，在加熱流延輥1 與調溫成130°C之第二輥2 (周速：30公尺/分鐘）之間（ 輥間距離：5公分）加以延伸2倍。將所製得之延伸薄膜 11，在第二輥2與調溫成60 °C之第三輥3(周速：45公尺/ 分鐘）之間（輥間距離：5公分）加以延伸1 .5倍。將所製 得之再延伸薄膜12，在第三輥3與調溫成25 °C之第四輥4 (周速：67.5公尺/分鐘）之間（輥間距離：5公分）加以 冷延伸1.5倍，以製得平均膜厚爲8微米之PBT薄膜13。 _ 經測定所製得之PBT薄膜13之膜厚差及熱收縮率結果， 膜厚差爲2微米，縱向之熱收縮率爲0.2 %，橫向之熱收縮 率爲0 · 2 % 〇 比較例1 " 除將加熱流延輥1之溫度設定在60°c以外，其餘則與實 · 施例1同樣地製得平均膜厚爲13微米之PBT薄膜。經測 定所製得之PBT薄膜13之膜厚差及熱收縮率結果，膜厚 差爲4微米，縱向之熱收縮率爲1 5 %，橫向之熱收縮率爲* 20 %。 因此，根據如上所述之實施例1至3之PBT薄膜，由於 其係將其從T型模頭擠壓所製得之薄膜，在加熱流延輥1 上加以徐冷以作成爲結晶化未延伸薄膜後才加以延伸，所 以具有優越的膜厚均勻性，且熱收縮率低。與此相對，比 較例1之PBT薄膜，由於其係將熔融PBT樹脂驟冷所製得 之非晶質之未延伸薄膜加以延伸者，所以與實施例1至3 -19 - 1297705 · · 相比較，則膜厚差大且熱收縮率不佳。 · 以上所述者，係參照實施例詳加說明本發明，但是本發 明並非局限於該等，其係可在本發明之精神範圍內作各種 變化。 產業上之利用件 如上所述，本發明聚對苯二甲酸丁二酯薄膜之製造方法 ，由於其係將熔融聚對苯二甲酸丁二酯樹脂從T型模頭擠 壓出成薄膜狀，將所製得之薄膜在實質的未經延伸之狀態 下加以徐冷以使聚對苯二甲酸丁二酯樹脂結晶化，然後將 嶋 所製得之結晶化薄膜加以延伸，因此所製得之聚對苯二甲 酸丁二酯薄膜係具有膜厚均勻性和耐熱收縮性。因此，根 據本發明之製造方法所製得之聚對苯二甲酸丁二酯薄膜， 係適合用作爲各種包裝材料、包裝袋、速食品用容器之用 、 途。 ' 【圖式簡單說明】 第1圖係展示本發明之根據T型模頭法之製造聚對苯二 甲酸丁二酯薄膜的裝置之一實例示意圖。 · 第2圖係展示本發明之根據T型模頭法之製造聚對苯二 甲酸丁二酯薄膜的裝置之其他實例示意圖。 第3圖係展示本發明之根據T型模頭法之製造聚對苯二 甲酸丁二酯薄膜的裝置之另一其他實例示意圖。 -20-deal with. Further, when the fourth roller 4 is subjected to the cooling treatment, the extension film may be additionally added at a temperature higher than the glass transition temperature (Tg) of the PBT resin and the crystallization temperature of 1 〇 ° C or less by the third roller 3 . 1 1 The step of quenching. (v) Lateral stretching step For the PBT film produced by any of the steps (i) to (iv) as described above, the stretching may be applied immediately to the lateral direction (TD). The step of applying the transverse stretching may be a conventional method such as a tenter method. (e) Heat treatment The PBT film system obtained as described above already has superior heat shrinkage resistance than those obtained by the prior art manufacturing method, but it is also possible to further improve heat shrinkage resistance. Further heat treatment is applied. For the heat treatment method, either "thermal fixing treatment" or "heat shrink treatment" can be used. These heat treatments are preferably carried out at a temperature between the Tg of the PBT film and the crystallization temperature of -10 or less. The "heat setting treatment" is carried out by a tenter method, a roll method or a roll method. The "heat shrinkage treatment" may be carried out by a tenter method, a roll method, a calendering method, or a belt conveyor method or a floating method. ® [3] PBT film is made translucent to transparent by the PBT film prepared as described above, and has superior film thickness uniformity and heat shrinkage when compared with the previous uniaxially stretched film. Sex. Specifically, the film having an average film thickness of 8 to 20 μm has a film thickness difference of 1 to 3 μm, and the heat shrinkage ratio is 0.3% or less in MD (longitudinal direction) and 0.5% or less in TD (transverse direction). Therefore, it can be used to form a printed layer or a metal evaporated layer having less unevenness. Moreover, when the -16- 1297705 line is subjected to secondary processing such as heat sealing and printing, the film size is also changed less. The "average film thickness" is obtained by measuring the thickness of the center portion and both end portions in the width direction of the PBT film at two points, and the average enthalpy of the enthalpy measured at six points in total. The "thickness difference" is obtained by measuring the thickness of the center portion and the both end portions in the width direction of the PBT film by 2 points for a total of 6 points, and then calculating the difference between the maximum 値 and the minimum 値. The smaller the sputum, the better the results. The so-called "heat shrinkage rate" is obtained by exposing the PBT film to a shrinkage rate of MD and TD after exposing it to a temperature of 150 ° C for 10 minutes. The PBT film obtained by the production method of the present invention may be laminated with other films as necessary. The present invention is explained in more detail by way of the following examples, but the invention is not limited to the embodiments. Example 1 PBT resin (trade name: Torecon "1 200S", manufactured by Toray Co., Ltd., melting point: 220 ° C; glass transition temperature: 22 ° C; crystallization temperature: 182 ° C) The mixture was fed to a twin-screw extruder (screw diameter: 300 mm, extrusion amount: 50 kg/hr), melt-kneaded at 235 ± 5 ° C, and a molten PBT resin was prepared in an extruder. Then, using the apparatus shown in Fig. 3, the molten PBT resin is extruded from a T-die 7 provided at the front end of the extruder, and is tempered to a temperature of 17 (TC rotating heating casting roll 1 (peripheral speed: Accepted by 1 ft/min, roll diameter: 50 cm. The extruded film 5 was quenched on a heated casting roll 1 at a rate of 9 ° C / sec to form an average film thickness of 50 μm of crystallized unstretched film 6. Then, the obtained crystallized unstretched film 6 was heated to a casting roll 1 -17 - 1297705 and a second roll 2 adjusted to 130 ° C (peripheral speed: 2 ft / min) (- light distance: 5 cm) is extended by 2 times. The obtained stretch film 11 is tempered in the second roll 2 to "the third roll 3 (peripheral speed) :40 m / min) (light distance: 5 cm) and then extended 2 times. The re-stretch film 1 2 was prepared to adjust the temperature to 3 5 第四 fourth roll 4 (peripheral speed: 4 0 The ft/min was cooled to obtain a PBT film 13 having an average film thickness of 13 μm. The film thickness difference and heat shrinkage ratio of the ruthenium film 13 obtained by the measurement were as follows, and the film thickness difference was 2 μm. heat The shrinkage is 〇1%, and the transverse heat shrinkage is 0.2%. φ Example 2 except that the temperature of the heating casting roll 1 is set to 150 ° C, the peripheral speed is set to 15 m/min, and the cooling rate is 18 In the same manner as in Example 1, a crystallized unstretched film 6 having an average film thickness of 40 μm was formed in the same manner as in Example 1 at ° C / sec. Then, the obtained crystal was crystallized. The film 6 is stretched between the heating casting roll 1 and the second roll 2 (peripheral speed: 30 m/min) adjusted to a temperature of 1 〇〇°c (the distance between the rolls is 5 cm) It was extended by a factor of 2. The obtained stretched film 1 1 was cooled with a third roll 3 (circumferential speed: 30 m/min) adjusted to 35 ° C to obtain an average film thickness of 20 μm. The PBT film 13. The film thickness difference and the heat shrinkage ratio of the PBT film 13 obtained by the measurement are as follows, the film thickness difference is 2 μm, the longitudinal heat shrinkage rate is 0.1%, and the transverse heat shrinkage rate is 0.15 %. Example 3 except that the temperature of the heating casting roll 1 is set to 180 ° C, the peripheral speed is set to 15 m / min, the cooling rate is 12 ° C / sec, and the rest is the same as in Example -18 - 129770 5, .1 Similarly, a crystallized unstretched film 6 having an average film thickness of 40 μm is formed. - Then, the obtained crystallized unstretched film 6 is heated to a temperature of 130 ° C by heating the casting roll 1 The second roll 2 (peripheral speed: 30 m/min) is stretched twice between (the distance between rolls: 5 cm). The stretch film 11 thus obtained is adjusted to 60 ° C in the second roll 2 The third roller 3 (peripheral speed: 45 m/min) is extended by 1.5 times between the rolls (5 cm). The prepared re-stretched film 12 was cold-extruded between the third roll 3 and a fourth roll 4 (peripheral speed: 67.5 m/min) adjusted to a temperature of 25 ° C (distance between rolls: 5 cm). 1.5 times to obtain a PBT film 13 having an average film thickness of 8 μm. _ The film thickness difference and heat shrinkage rate of the PBT film 13 obtained by the measurement were as follows, the film thickness difference was 2 μm, the longitudinal heat shrinkage rate was 0.2%, and the transverse heat shrinkage rate was 0 · 2 %. 〇Comparative Example 1 " A PBT film having an average film thickness of 13 μm was obtained in the same manner as in Example 1 except that the temperature of the heating casting roll 1 was set to 60 °C. As a result of measuring the difference in film thickness and heat shrinkage ratio of the obtained PBT film 13, the film thickness difference was 4 μm, the longitudinal heat shrinkage rate was 15%, and the transverse heat shrinkage rate was * 20%. Therefore, according to the PBT film of Examples 1 to 3 as described above, since it is obtained by extruding the film obtained from the T-die, it is cold-cooled on the heating casting roll 1 to be crystallized. After stretching the film, it is extended, so that it has superior film thickness uniformity and low heat shrinkage. On the other hand, in the PBT film of Comparative Example 1, since the amorphous unstretched film obtained by quenching the molten PBT resin was extended, it was compared with Examples 1 to 3 -19 - 1297705 · , the film thickness difference is large and the heat shrinkage rate is not good. The above is a detailed description of the present invention with reference to the embodiments, but the present invention is not limited thereto, and various changes can be made within the spirit and scope of the invention. INDUSTRIAL APPLICABILITY As described above, the method for producing a polybutylene terephthalate film of the present invention is obtained by extruding a molten polybutylene terephthalate resin from a T-die into a film shape. The obtained film is quenched in a substantially unstretched state to crystallize the polybutylene terephthalate resin, and then the crystallized film obtained by the ruthenium is extended, thereby preparing the film. The polybutylene terephthalate film has film thickness uniformity and heat shrinkage resistance. Therefore, the polybutylene terephthalate film obtained by the production method of the present invention is suitable for use as a container for various packaging materials, packaging bags, and instant food containers. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing an example of an apparatus for producing a film of polybutylene terephthalate according to the T-die method of the present invention. Fig. 2 is a view showing another example of the apparatus for producing a film of polybutylene terephthalate according to the T-die method of the present invention. Fig. 3 is a view showing another example of the apparatus for producing a film of polybutylene terephthalate according to the T-die method of the present invention. -20-
I 1297705 【主要元件符號說明】 1 加熱流延輥（輥） 2 第二輥（輥） 3 第二輕（輥） 4 第四輥（輥） 5 擠製薄膜 6 結晶化未延伸薄膜 7 T型模頭 8 捲取軸 9 導輥 10 夾輥 11 延伸薄膜 12 再延伸薄膜 13 PBT薄膜 61 、 62 ' 63 延伸區域 -21 -I 1297705 [Description of main component symbols] 1 Heating casting roll (roller) 2 Second roll (roller) 3 Second light (roller) 4 Fourth roll (roller) 5 Extruded film 6 Crystallized unstretched film 7 T type Die 8 take-up shaft 9 guide roll 10 nip roll 11 stretch film 12 stretch film 13 PBT film 61, 62 ' 63 extension area - 21