1314940 九、發明說明： 【發明所屬之技術領域】 本發明係關於:種新穎之提升聚笨乙烯發㈣開孔率 之方法及其應用。错由混合聚笨乙烯 烯製 泡：料可具有高開孔率之特性，以本發明之發泡體= 之真空保溫片，可具有低熱傳導率之特性。 < 又 【先前技術】1314940 IX. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD OF THE INVENTION The present invention relates to a novel method for improving the opening ratio of polystyrene (IV) and its application. The foam is made of mixed polystyrene. The material can have the characteristics of high open porosity. The vacuum insulation sheet of the foam of the present invention can have the characteristics of low thermal conductivity. < again [Prior Art]
熱能傳遞方式有傳導、對流和輻射。傳導發生於熱能 透過固體介質傳遞，對流是透過氣體的流動，使熱能傳遞； 至於輻射熱能傳遞需於高溫環境之下才能明顯產生。就傳 導而言，固體介質比氣體介質具有較高的熱傳導係數，所 以在相同材料下，多孔性板㈣熱傳導低於沒有孔洞的板 材，因為多孔性板材的結構中有氣體存在，然而若能使多 孔性板材内氣體排除可進一步提升絕熱效果。 利用多孔性板材外面包覆阻隔袋（薄膜），藉由抽氣造 成保溫片内部負壓再封裝之，可產生一隔熱產品—真空保溫 片，其係利用真空絕緣方式以達到降低熱傳效果並加強絕 熱之目的。因此，真空保溫片之芯材需具孔洞使内部空氣 被抽出，並且需能承受負壓。 聚苯乙烯在做為真空保溫片芯材上具有相當潛力，由 於價格便宜，在高溫時可維持良好的熔融強度易發泡加 工，無論是傳統發泡（平均氣泡尺寸大於lOOym)或是微胞 發泡（平均氣泡尺寸小於1 〇 〇 β m)都非常容易得到閉孔結構 (各氣泡獨立不相通連）’不易得到開孔結構的發泡材，且具 有良好抗壓機械性質。未發泡聚苯乙烯(polystyrene, PS)的 熱傳係數約0.14 W/m.k，而PS發泡體的熱傳係數約 P02940027TW(本所案號 05P0324) 5 1314940 0.03〜0.035 W/m.k，由此可知氣體會大幅降低熱傳導係數。 若要進一降低發泡材的熱傳導係數，需將發泡體内的氣體 -儘可能去除，以降低氣體產生對流效應。開孔性發泡材内 ，氣泡與氣泡之間相互連通，可以放入多層袋内，抽氣造成 真空再密封袋子形成真空保溫片’其熱傳係數低％ps發泡 ' 材約2〜5倍。所以PS發泡體内部的開孔率越高，發泡^内 : 部的氣體被抽出的量就越多，有助於降低對流熱傳的效 . 應。由於製造高開孔率PS發泡體的加工範圍通常較為狹 鲁小’發泡體製造過程中，除了控制材料及配方以外，便是 調整操作條件例如發泡溫度及發泡壓力。發泡過程中，發 泡體的發泡條件越寬廣，越容易得到穩定的產品，意即PS 發泡配方若有範圍較大的發泡溫度和發泡壓力，則越容易 得到穩定高開孔率的PS發泡體。 目前文獻中記載製造多孔性發泡體方法，例如美國專 利公告號第5,679,718號係為聚氨酯開孔發泡體之製法，以 HFC-134a為主要氣體混入其他氣體，進行物理發泡。此外，美 國專利公告號第5,693,687號（Dow，1997)即以聚笨乙烯為 φ 原料，使用H CFC-124b，HCFC-22，Etcl或C02…等混合 氣體當發泡劑。主要以HCFC為主要氣體，再混入其他氣 體，利用物理發泡造成PS發泡。又WO 96/34038(Dow， 1996)，以及Dow公司提出美國專利公告號5,780,521 (1998)，5,863,960 (1999)，5,869,544 (1999)亦是聚苯乙烯開 孔發泡體，其發泡劑的重點是HFC-134a (多量）與Etcl， ' HCFC-22，HCFC-22，C〇2和N2混合，物理發泡製成聚笨 乙烯之開孔發泡體，其開孔率約70%以上。 以上方法只採用一種聚合物作為原料，而且都是以物 理方法進行發泡，但都必須採用含有氟或氯之氣體進行， P02940027TW(本所案號 05P0324) 6 1314940 容易產生環境污染的問題。 此外，亦有使用非氟或氯之氣體進行發泡反應，例如 EP 0849309Al(Sirap-Gema S.P.A，1998)和 RE37780 Reissue ,6,093,751(Sirap-Gema S.P.A，2002)係以聚苯乙烯為開孔板 之材料，以礙數4至 6之脂肪族烴（aliphatic • hydrocarbon(C4~C6))為發泡劑。聚苯乙烯(30~95wt%)、發 ； 泡劑（0~65wt%)和成核劑（0.2〜10wt%)的混合物置入押出 機，於高溫下形成開孔發泡板，其開孔率約50% ，然而脂 _ 肪族烴的氣體容易燃燒引起火災。 另外，還有混合兩種以上的聚合物做為原料，再混合 發泡劑等以製造開孔發泡體之習知技術。例如：WO 98/21252 (Sentinel products, 1998)係混合芳環烯金屬衍生物 之聚乙稀（netallocebe PE，mPE )與其他聚鍊烴烯(polyolefins) 例如LDPE、MDPE、LLDPE、HDPE與EVA等混合後，與 mPE進行交聯，使用化學發泡方法得到開孔開孔聚鍊烯烴 發泡體。又例如WO 98/56430 (Dow, 1998)是以聚苯乙烯或 聚苯乙烯與SEBS共聚合物混合物（SEBS : Styrene/ethyl φ benzene/styrene)為材料。發泡劑為 HFC-134a，Etcl 和 C02 混合氣體，以物理發泡方式形成開孔的發泡體。此外，WO 99/47592 (Dow，1999)，美國公告專利第 6,093,752(Dow， 2000)和6,174,471號(Dow，2001)是聚苯乙烯與乙烯-苯乙烯 共聚物（ethylene-styrene interpolymer (ESI))混合後，以二 氧化碳當作發泡劑形成開孔發泡體，聚苯乙烯的分子量約 ' 20萬，開孔率達80% 。 為改善上述習知製造聚苯乙烯發泡體之技術，研發一 高開孔率之聚苯乙烯發泡體以及真空保溫片芯材成為值得 研究課題。 P02940027TW(本所案號 05P0324) 7 1314940 【發明内容】 由前述可知’先前技術中之製造聚笨乙烯發泡體技 •術’物理發泡方法易產生污染且不易達成高開孔率之目 的，而化學發泡方法往往雖可提高開孔率至—定程度，但 ' 有材料易燃等問題，因此本發明之目的係提供一種用於製 : 備發泡體之組合物，該組合物可有效提高聚笨乙烯發泡體 . 之開孔率。 鲁 本發明之另一目的在於提供一發泡體之製備方法，利 用結合物理發泡和化學發泡方式來製備本發明之發泡體， 使其可達到高開孔率之目的。 本發明之再一目的為提供一種高開孔率之發泡體，其 具有高開孔率及低熱傳導率之特性，且該發泡體於抽氣造 成内部真空後可耐壓達lkg/cm2以上，適合作為真空保溫片 芯材。 為達上述目的’本發明提供一種用於製備發泡體之組 合物’係包含：90〜98wt%之聚笨乙烯；以及2~i〇wt%之聚 Φ 乙烯。該組合物可進一步包含成核劑、填充劑以及發泡劑。 組合物中之聚苯乙烯分子量介於2〇萬至3〇萬之間，聚乙 烯之分子量介於22萬至32萬之間。 前述聚乙烯包含低密度聚乙烯(LDPE)、高密度聚乙烯 (HDPE)或線性聚乙烯（LLDPE) ’較佳為低密度聚乙烯 (LDPE)。組合物中之成核劑的量為〇 lphr_2phr。填充劑的 ’ 量為〇.lphr_2Phr。發泡劑的量為0.5phr-3.0phr。其中前述成 核劑包含硬脂酸、硬脂酸鈣、硬脂酸鋅或硬脂酸鋇；填充 劑包含碳酸鈣、碳黑、石墨、滑石粉、二氧化鈦 、矽石或 雲母片；發泡劑為化學發泡劑，較佳為偶氮化合物，更佳 P02940027TW(本所案號 05P0324) 8 1314940 為偶氮化合物為偶氮甲醯胺(ADCA)。 另一方面，本發明提供一種發泡體之製備方法，包括 下列步驟：將聚苯乙烯、聚乙烯、成核劑、填充劑以及發 泡劑混鍊’以得到一未發泡混合物；將前述未發泡混合物 壓製成未發泡平板；將前述未發泡平板含浸於一超臨界狀 態下之氣體；及將前述未發泡平板進行發泡，以得到高開 孔率之發泡體。 在一較佳實施例中，前述步驟中之聚苯乙烯之含量為 90〜98wt%，聚乙烯之含量為2~10wt%。聚苯乙烯之分子量 介於20萬至30萬之間。聚乙烯之分子量介於22萬至32 萬之間。聚乙烯可包含低密度聚乙烯(LDPE)、高密度聚乙 烯（HDPE)或線性聚乙烯（LLDPE)，較佳為低密度聚乙烯 (LDPE)。步驟中之成核劑的量為0·lphr-2phr。填充劑的量 為0.1phr-2phr。發泡劑的量為0.5phr-3.0phr。此外，成核劑 可為硬脂酸、硬脂酸鈣、硬脂酸鋅或硬脂酸鋇，填充劑可 為碳酸鈣、碳黑、石墨、滑石粉、二氧化鈦、矽石或雲母 片。發泡劑可為化學發泡劑，較佳為偶氮化合物，更佳為 偶氮甲醯胺(ADCA)。 在一較佳實施例中，未發泡平板係以熱壓機於110至 130°C下壓製而成。其中前述步驟中所述之氣體包含氮氣或 二氧化碳或氮氣及二氧化碳之混合氣體，較佳為氣體為氮 氣及二氧化碳之混合氣體。步驟中之含浸壓力為 2000-5000psi、發泡溫度為125-145°C。進行發泡時包含一 洩壓過程，該洩壓過程為瞬間完全洩壓或先洩至低壓、留 置固定一段時間再完全洩壓。瞬間完全洩壓時’壓力為迅 速洩放至大氣壓力。洩壓過程為先洩至l〇〇〇-2000psi的低 壓，留置2-10分鐘再將壓力洩放至大氣壓力。 P02940027TW 体所案號 05PQ324) 9 1314940 再者，本發明提供一種高開孔率之發泡體，係由上述方 法所製備。此一發泡體之開孔率為99%至90%。其抗壓力 大於 lkg/cm2。 又，本發明提供一種真空保溫片之芯材，係以上述方法 製備。其抗壓力大於lkg/cm2。 ' 本發明提供改良習知技術之聚苯乙烯發泡體製造方 ； 法，結合物理發泡方法以及化學發泡方法，並利用聚苯乙 稀與聚乙烯之間不相容之特性，經加熱冷卻後，增加發泡 - 體之開孔率。本發明由於使用氮氣與二氧化碳作為物理發 • 泡氣體，因此更具有環保概念。綜上所述，本發明開發之 提升聚苯乙烯發泡體開孔率之方法及其應用，可有效改善 習知技術之缺失與弊端。 【實施方式】 本發明所沿用的現有技藝，在此謹作重點式的引用， 以助本發明之闡述。並且下述内文中相關圖式並未依比例 繪製，其作用僅在表現本發明之結構特徵。 φ 本發明係提供一種增加製造聚苯乙烯開孔發泡體加工 範圍的方法。其製備方法包括聚苯乙烯、聚乙烯、發泡成 核劑、填充物及放熱型化學發泡劑混鍊，將混鍊後混合物 壓製成為未發泡板材，再將板材放入批次式模頭内，在高 . 溫及高壓之下含浸二氧化碳和其他超臨界狀態氣體例如氮 氣或其他混合氣體。當板材含浸一段時間後，洩壓發泡得 ’ 到開孔及抗壓大於lkg/cm2的發泡材，可增加高開孔率的發 泡體加工範圍，此發泡材可應用於真空保溫片。 本發明所利用之物理發泡製程係為根據第一圖所示之 批次發泡製程及高壓氣體混合灌氣管路配置示意圖（該示 P02940027TW(本所案號 05P0324) 10 1314940 意圖並未揭露装置之全部結構，僅繪示說明書中需對應說 明之結構）’其中第一系統是c〇2氣體的灌氣系統，係包含 裝有C〇2氣體的高壓鋼瓶i及一壓力錶P1 ;冷凍機7用以 降低C〇2氣體的溫度，使C〇2氣體液化，可調控溫度介於 -20〜15°C ; C〇2氣體增壓機3及高壓c〇2氣體灌注機5，' 該氣體增壓機3係為提供氣體灌注機5有一穩定的氣體壓 力之用；以及高壓同流管路及連接另一高壓灌氣系統的管 路0 第二系統為&氣體的灌氣系統，係包含裝有％氣體的 高壓鋼瓶2及-壓力錶P2; %氣體增壓機4及高壓 /主機6，咼壓管路及連接c〇2系統的管路。 、、其高壓鋼瓶1及2分湘於儲存c〇2氣體及Μ:氣體。 冷束機7用以維持〇02氣體的低溫狀態，使其比重增大易 於增壓喊C02於氣/液態被私於系財，㈣移除增壓 ^注系統多餘的熱量。因高壓鋼瓶的氣體隨著氣體的使 ^ ^使鋼力會逐漸減小，增壓機3、4係用以穩定 f主機之氣體壓力。當❹氣體含浸樹料，通常含浸壓 力達2000Psi或3000psi以上，所以須吊、3又 壓機3、4内的氣體穩定灌人模子内，達騎須的操作壓= 如下備之操作方式之—具體實施態樣 ^下.在135 C之下_雙滚輪將聚苯乙烯和*同聚乙 烯樹脂先混合，再與其他添力添丨、日4 機在赃狀態下，壓製成之後利用模壓 式發泡實驗步驟，首先設進 —^ 又热壓含/叉拉具之上、下槿的溫 度’基本設定溫度為120°C 夕P弓/士 、 . λ ^ 4〇C之間。待溫度穩定後，再 將▲練的板材置入熱壓模内，關閉 氮氣灌注機，將氮氣灌人模内達到設定壓力，接^灌入 Π P02940027TW(本所案號 05P0324) 1314940 C〇2氣體’在模具内形成氮氣和co2混合氣體，其混合的 比例可以用壓力不同來顯示，最後含浸壓力值可為 2000~5000psi，同時計算含浸時間，待含浸時程達設定時間 時，可以瞬間開模使板材迅速自由發泡，或洩放到 2000~1000psi的低壓，留置一段時間（2〜10分)再開模，得到 • 不同發泡體。 - 以下實施例中所使用之批次式發泡模具設計為圓形模 具’係考慮配合熱壓機的活塞形狀以及平均的受力。此模 鲁 具設計尺寸’内徑為300 mm，深度為15 mm，分成上、下 模具’氮氣和C02注入口由下模具注入模内。然本發明所 使用之模具並不限於此，熟知此技藝之人可根據所需而調 整所使用之模具規格。 以下係提供利用本發明之實施例詳細說明書本發明之 技術及特點’然本實施例並非用以限定本發明，任何熟悉 此技藝者’在不脫離本發明之精神和範圍内，當可作各種 之更動與潤飾。 • 實施例 實施例一、以本發明之方法製造聚笨乙烯發泡體 本實施例係使用如第一圖所示之批次製程系統製備 - 本發明之聚苯乙烯發泡體。本實施例係製備各種不同配方 之發泡體，如下表一所示，其中配方一為純PS之對照組。 本實施例所使用之聚苯乙烯（ps)分子量為250 0〇〇Mw， 聚乙烯(PE)之分子量為260,000 Mw ’而化學發泡劑ADCA 為市售商品（商品型號：台新-250H)。將如表一所^之發泡 配方混鍊製成未發泡板材’再放入批次式模頭於不同發泡 P02940027TW(本所案號 05P0324) 12 1314940 (加工）溫度與加工壓力（33〇〇pSi)下含浸c〇2及Nz混合氣 體，混合氣體之比例C〇2/N2為50/50,含浸時間為90分鐘。 之後下降壓力至13〇〇psi留置1〇分鐘後再開模，可得到PS 發泡體或PS/PE發泡體。這些發泡體會顯現不同程度的開 孔率’基本上高開孔率的PS或ps/pe發泡體的熱傳導係數 較低。 表一：發泡體配方 配方 1 2 3 4 5 聚苯乙稀 100 98 95 93 ----—---- 90 聚乙烯 0 2 5 7 10 碳黑 0.3 0.3 0.3 0.3 —------- 0.3 硬脂酸約 1.0 1.0 1.0 1.0 1.0 化學發泡劑 2.0 2.0 2.0 2.0 2.0 ----* 宜皇:、以毛查乙烯發泡艚·柞霞穿保溫片 取由實施例一所製作之聚苯乙烯發泡體，裁切成正方 形如第二圖作為真^保溫㈣糾，之後將芯材放入多層 袋抽真技熱封形成如第三圖的真空保溫片。接著研究發 泡體内部結構並量測真空保溫片的熱傳導係數。 第四圖為測里PS (即表一之配方i對照組）或本發明 之PS/PE混合發泡體製成真空保溫片熱傳導係數結果。當 純ps的發泡體在發泡溫度12rc、123。〇、125。匚及i27C>c 時，其熱傳導係數變異性非常大且發泡溫度i2it^ 123〇c P02940027TW(本所案號 〇5P〇324) 13 1314940 所得ps發泡體，其開孔率非常低，因此其熱傳導係數也很 南。但是PS和LDPE混合後得到的PS/LDPE發泡體，其熱 傳導係數下降，代表開孔率增加，尤其PS/LDPE(7%)發泡 體的熱傳導係數’在4個發泡溫度的結果非常接近，這代 表發泡過程中，發泡體的開孔率不會因為溫度變化產生非 常大的改變’有助於生產過程中，得到穩定的產品。 第五圖係各種PS/PE發泡體為芯材的真空保溫片之熱 傳導係數。聚乙烯大致上可以分為三類：LDPE熔點約105 °C~115°C、線性聚乙烯(LLDPE)，熔點約115。〇125。(：和高 密度聚乙烯（HDPE)熔點約130°C〜135°C，PS可以和不同 比例的各種PE混合形成發泡體。本實施例所使用之發泡的 過程溫度為125°C。由本實施例結果發現以PS/LDPE發泡 體為芯材的真空保溫片熱傳導係數低於PS/LLDPE和 PS/HDPE發泡體的真空保溫片熱傳導係數。此結果顯示以 PS/LDPE發泡體為芯材的真空保溫片可以展現較佳的保溫 效果。 第六圖至第九圖係顯示熱傳導係數為0.027、0.02、0.01 φ 和0.0065 W/m.k發泡體之内部結構，由實驗結果顯示熱傳 導係數高之發泡體其發泡體開孔率較低，因此觀察熱傳導 係數為0.027 W/m.k之發泡體，可以發現其幾乎是閉孔結構 (如第六圖所示），而隨著開孔結構增加，發泡體之熱傳導係 數會隨之下降，因此熱傳導係數為0.0065 W/m.k的發泡體 具有非常高開孔結構。 " 綜上所述，本發明之方法所製作之聚苯乙烯發泡體， 確貫具有高開孔率以及低熱傳導係數之特性。相較於先前 技藝可提升發泡體之開放性開孔率，而且不使用氟氣與氯 氣而使用氮氣與二氧化碳作為物理發泡劑因此較為環保。 P02940027TW(本所案號 05P0324) 14 1314940 本發明之製作聚苯乙浠發泡體的方法，由於可大量提升發 泡體之開孔率而可廣泛應用於製作真空保溫芯材。 雖然本發明已以較佳實施例揭露如上，然其並非用以 限定本發明，任何熟悉此技藝者，在不脫離本發明之精神 和範圍内，當可作各種之更動與潤飾，因此，本發明之保 - 護範圍，當視後附之申請專利範圍所界定者為準。 其他實施態樣 Φ 本發明之實施方法已詳述於前述實施例中，任何熟悉 本技術領域之人士皆可依本發明之說明，在不背離本發明 之精神與範圍内視需要更動、修飾本發明，因此，其他實 施態樣亦包含在本發明之申請專利範圍中。 【圖式簡單說明】 第一圖係為本發明之批次發泡製程及高壓氣體混合灌 氣管路配置示意圖。 第二圖係為本發明實施例二之聚苯乙烯發泡體裁切實 • 體圖。 第三圖係為本發明實施例二之真空保溫片實體圖。 第四圖係為本發明實施例二中，PS或本發明之PS/PE 混合發泡體製成真空保溫片熱傳導係數結果。 , 第五圖係為本發明實施例二中，各種PS/ΡΕ發泡體為 芯材的真空保溫片之熱傳導係數。 / 第六圖係為本發明實施例二中，熱傳導係數為0.027 W/m.k發泡體之内部結構圖。 第七圖係為本發明實施例二中，熱傳導係數為0.02 W/m.k發泡體之内部結構圖。 P02940027TW(本所案號 05P0324) 15 1314940 第八圖係為本發明實施例二中，熱傳導係數為0.01 W/m.k發泡體之内部結構圖。 第九圖係為本發明實施例二中，熱傳導係數為0.0065 W/m.k發泡體之内部結構圖。 ^ 【主要元件符號對照說明】 ' 1高壓鋼瓶 2高壓鋼瓶 籲3C02氣體增壓機 4 N2氣體增壓機 5高壓C02氣體灌注機 6高壓N2灌注機 7冷凍機The heat transfer modes are conduction, convection and radiation. Conduction occurs when heat is transmitted through a solid medium. Convection is the flow of gas through which heat is transferred. As far as radiant heat transfer is required, it can be produced in a high temperature environment. In terms of conduction, the solid medium has a higher heat transfer coefficient than the gas medium, so under the same material, the porous plate (4) has lower heat conduction than the plate without holes, because the gas in the structure of the porous plate exists, but Gas exclusion in the porous sheet further enhances the insulation. The outer surface of the porous sheet is covered with a barrier bag (film), and the internal pressure of the heat insulating sheet is re-packaged by pumping, thereby generating a heat insulating product-vacuum heat insulating sheet, which uses vacuum insulation to reduce the heat transfer effect. And strengthen the purpose of thermal insulation. Therefore, the core material of the vacuum heat insulating sheet needs to have holes to allow the internal air to be withdrawn and to withstand the negative pressure. Polystyrene has considerable potential as a core material for vacuum insulation sheets. Due to its low price, it can maintain good melt strength and easy foaming at high temperatures, whether it is conventional foaming (average bubble size is more than 100 μm) or microcells. Foaming (average bubble size is less than 1 〇〇β m) is very easy to obtain closed-cell structure (each bubble is not connected independently) 'foaming material that is difficult to obtain open-cell structure, and has good compressive mechanical properties. The heat transfer coefficient of polystyrene (PS) is about 0.14 W/mk, and the heat transfer coefficient of PS foam is about P02940027TW (Our Office No. 05P0324) 5 1314940 0.03~0.035 W/mk. It can be seen that the gas greatly reduces the heat transfer coefficient. In order to further reduce the heat transfer coefficient of the foam material, it is necessary to remove the gas in the foam body as much as possible to reduce the convection effect of the gas. In the open-cell foaming material, the air bubbles and the air bubbles communicate with each other, and can be placed in a multi-layer bag, and the air is evacuated to form a vacuum heat-insulating sheet. The heat transfer coefficient is low and the ps foaming material is about 2 to 5 times. Therefore, the higher the opening ratio inside the PS foam, the more the gas is extracted from the foaming portion, which helps to reduce the effect of convective heat transfer. Since the processing range of the PS foam produced by the high opening ratio is generally narrow, the manufacturing conditions such as the foaming temperature and the foaming pressure are adjusted in addition to the control materials and the formulation in the foam manufacturing process. In the foaming process, the wider the foaming condition of the foam, the easier it is to obtain a stable product, which means that if the PS foaming formula has a wide range of foaming temperature and foaming pressure, it is easier to obtain a stable high opening. Rate of PS foam. A method for producing a porous foam is described in the literature. For example, U.S. Patent No. 5,679,718 is a method for producing a polyurethane open-cell foam, and another gas is mixed with HFC-134a as a main gas to carry out physical foaming. In addition, U.S. Patent Publication No. 5,693,687 (Dow, 1997) uses polystyrene as a raw material of φ, and a mixed gas such as H CFC-124b, HCFC-22, Etcl or C02... as a blowing agent. HCFC is the main gas, and other gases are mixed into it, and PS foaming is caused by physical foaming. Also, WO 96/34038 (Dow, 1996), and Dow Corporation, U.S. Patent Nos. 5,780,521 (1998), 5,863,960 (1999), 5,869,544 (1999) are also polystyrene open-cell foams, the focus of which is a foaming agent. It is HFC-134a (multiple amount) mixed with Etcl, 'HCFC-22, HCFC-22, C〇2 and N2, and is physically foamed to form a polystyrene open-cell foam with an open cell ratio of about 70% or more. The above method uses only one type of polymer as a raw material, and all of them are foamed by a physical method, but all must be carried out using a gas containing fluorine or chlorine, and P02940027TW (Our Office No. 05P0324) 6 1314940 is liable to cause environmental pollution. In addition, a non-fluorine or chlorine gas is also used for the foaming reaction, for example, EP 0849309 Al (Sirap-Gema SPA, 1998) and RE37780 Reissue, 6,093, 751 (Sirap-Gema SPA, 2002) are made of polystyrene. The material is a foaming agent with an aliphatic hydrocarbon (C4~C6) which is a hindrance of 4 to 6. a mixture of polystyrene (30~95wt%), hair; foaming agent (0~65wt%) and nucleating agent (0.2~10wt%) is placed in an extruder to form an open cell foaming plate at a high temperature, and the opening is formed The rate is about 50%, but the gas of the fat-abated hydrocarbon is easily burned to cause a fire. Further, there is a conventional technique in which two or more kinds of polymers are mixed as a raw material, and a foaming agent or the like is mixed to produce an open-cell foam. For example: WO 98/21252 (Sentinel products, 1998) is a mixed aromatic olefinic metal derivative of polyethylene (netallocebe PE, mPE) and other polyalkanes (polyolefins) such as LDPE, MDPE, LLDPE, HDPE and EVA, etc. After mixing, crosslinking with mPE, and a chemically foamed method was used to obtain an open-celled open-chain polyolefin foam. Further, for example, WO 98/56430 (Dow, 1998) is a mixture of polystyrene or polystyrene and SEBS copolymer (SEBS: Styrene/ethyl φ benzene/styrene). The foaming agent is a mixed gas of HFC-134a, Etcl and C02, and forms an open-cell foam by physical foaming. In addition, WO 99/47592 (Dow, 1999), U.S. Patent Nos. 6,093,752 (Dow, 2000) and 6,174,471 (Dow, 2001) are polystyrene and ethylene-styrene interpolymer (ESI). After mixing, carbon dioxide was used as a foaming agent to form an open-cell foam having a molecular weight of about '200,000 and an open cell ratio of 80%. In order to improve the above-described technique for producing a polystyrene foam, it has been a research subject to develop a polystyrene foam having a high opening ratio and a vacuum heat insulating core material. P02940027TW (Our Office No. 05P0324) 7 1314940 [Disclosed from the foregoing] It can be seen from the foregoing that the 'preparation of the polystyrene foam technology of the prior art' physical foaming method is liable to cause pollution and is difficult to achieve a high opening ratio. While the chemical foaming method tends to increase the opening ratio to a certain degree, but the problem is that the material is flammable, the object of the present invention is to provide a composition for preparing a foam, which can be Effectively increase the open porosity of polystyrene foam. Another object of the invention is to provide a method for preparing a foam by combining physical foaming and chemical foaming to prepare a foam of the present invention so as to achieve a high opening ratio. Still another object of the present invention is to provide a foam having a high opening ratio which has a high opening ratio and a low thermal conductivity, and the foam can withstand a pressure of lkg/cm 2 after drawing an internal vacuum. The above is suitable as a vacuum insulation sheet core material. To achieve the above object, the present invention provides a composition for preparing a foam comprising: 90 to 98% by weight of polystyrene; and 2 to 9% by weight of poly(ethylene). The composition may further comprise a nucleating agent, a filler, and a blowing agent. The polystyrene has a molecular weight of between 20,000 and 30,000 and the molecular weight of the polyethylene is between 220,000 and 320,000. The aforementioned polyethylene comprises low density polyethylene (LDPE), high density polyethylene (HDPE) or linear polyethylene (LLDPE)', preferably low density polyethylene (LDPE). The amount of nucleating agent in the composition is 〇lphr_2phr. The amount of the filler was 〇.lphr_2Phr. The amount of blowing agent is from 0.5 phr to 3.0 phr. Wherein the nucleating agent comprises stearic acid, calcium stearate, zinc stearate or barium stearate; the filler comprises calcium carbonate, carbon black, graphite, talc, titanium dioxide, vermiculite or mica flakes; It is a chemical blowing agent, preferably an azo compound, more preferably P02940027TW (Our Office No. 05P0324) 8 1314940 is an azo compound which is azomethanamine (ADCA). In another aspect, the present invention provides a method for preparing a foam comprising the steps of: mixing a polystyrene, a polyethylene, a nucleating agent, a filler, and a blowing agent to obtain an unfoamed mixture; The unfoamed mixture is pressed into an unexpanded flat plate; the unexpanded flat plate is impregnated with a gas in a supercritical state; and the unfoamed flat plate is foamed to obtain a foam having a high open porosity. In a preferred embodiment, the polystyrene content in the preceding step is 90 to 98% by weight, and the polyethylene content is 2 to 10% by weight. The molecular weight of polystyrene is between 200,000 and 300,000. The molecular weight of polyethylene is between 220,000 and 320,000. The polyethylene may comprise low density polyethylene (LDPE), high density polyethylene (HDPE) or linear polyethylene (LLDPE), preferably low density polyethylene (LDPE). The amount of nucleating agent in the step is from 0.1 phr to 2 phr. The amount of filler is from 0.1 phr to 2 phr. The amount of blowing agent is from 0.5 phr to 3.0 phr. Further, the nucleating agent may be stearic acid, calcium stearate, zinc stearate or barium stearate, and the filler may be calcium carbonate, carbon black, graphite, talc, titanium dioxide, vermiculite or mica flakes. The blowing agent may be a chemical blowing agent, preferably an azo compound, more preferably azomethine (ADCA). In a preferred embodiment, the unfoamed flat sheet is formed by pressing at 110 to 130 ° C with a hot press. The gas described in the foregoing step contains nitrogen or carbon dioxide or a mixed gas of nitrogen and carbon dioxide, and preferably the gas is a mixed gas of nitrogen and carbon dioxide. The impregnation pressure in the step is 2000-5000 psi and the foaming temperature is 125-145 °C. When the foaming is carried out, a pressure releasing process is included, and the pressure releasing process is a complete pressure relief in an instant or first to a low pressure, and the fixing is fixed for a certain period of time and then completely released. When the pressure is completely relieved in an instant, the pressure is quickly released to atmospheric pressure. The pressure relief process is to first vent to a low pressure of l〇〇〇-2000 psi, leave it for 2-10 minutes and then vent the pressure to atmospheric pressure. Further, the present invention provides a foam having a high open porosity, which is prepared by the above method. The opening ratio of this foam is from 99% to 90%. Its anti-stress is greater than lkg/cm2. Further, the present invention provides a core material of a vacuum heat insulating sheet which is prepared by the above method. Its anti-pressure is greater than lkg/cm2. The present invention provides a polystyrene foam manufacturing method which improves the prior art; a method, a physical foaming method and a chemical foaming method, and utilizes the incompatibility between polystyrene and polyethylene, and is heated After cooling, increase the opening ratio of the foaming body. The present invention is more environmentally friendly because it uses nitrogen and carbon dioxide as physical foaming gases. In summary, the method and application of the polystyrene foam opening ratio developed by the present invention can effectively improve the defects and drawbacks of the prior art. [Embodiment] The prior art of the present invention is hereby incorporated by reference. Further, the related drawings in the following texts are not drawn to scale, and their functions are only to show the structural features of the present invention. φ The present invention provides a method of increasing the processing range for producing polystyrene open-cell foams. The preparation method comprises a polystyrene, a polyethylene, a foaming nucleating agent, a filler and an exothermic chemical foaming agent mixed chain, and the mixed mixture is pressed into an unfoamed plate, and then the plate is placed in a batch mode. In the head, carbon dioxide and other supercritical gases such as nitrogen or other mixed gases are impregnated under high temperature and high pressure. When the plate is impregnated for a period of time, the pressure-relieving foaming is made into a foaming material with a hole opening and a pressure resistance greater than lkg/cm2, which can increase the processing range of the foam with a high opening ratio, and the foaming material can be applied to vacuum insulation. sheet. The physical foaming process utilized by the present invention is a schematic diagram of the batch foaming process and the high-pressure gas mixed gas filling pipeline according to the first drawing (the P02940027TW (the present invention, 05P0324) 10 1314940 is not intended to disclose the device. The whole structure is only shown in the specification. The first system is a gas filling system of c〇2 gas, which is a high-pressure steel cylinder i containing C〇2 gas and a pressure gauge P1; 7 to reduce the temperature of C〇2 gas, liquefy C〇2 gas, the temperature can be adjusted between -20~15 °C; C〇2 gas booster 3 and high pressure c〇2 gas perfusion machine 5, ' The gas booster 3 is for providing the gas perfusion machine 5 with a stable gas pressure; and the high pressure cocurrent flow line and the line connecting the other high pressure gas filling system. The second system is a gas filling system for & It consists of a high-pressure cylinder 2 with a % gas and a pressure gauge P2; a gas booster 4 and a high pressure/host 6, a pressure line and a line connecting the c〇2 system. 1, and its high-pressure cylinders 1 and 2 points in the storage of c〇2 gas and helium: gas. The cold beam machine 7 is used to maintain the low temperature state of the 〇02 gas, so that the specific gravity is increased, and it is easy to pressurize the C02 gas to be in a gas/liquid state, and (4) remove the excess heat of the booster system. Since the gas of the high-pressure cylinder is gradually reduced with the gas, the supercharger 3, 4 is used to stabilize the gas pressure of the f main engine. When the helium gas is impregnated with the tree material, the impregnation pressure is usually 2000Psi or more than 3000psi, so the gas in the 3 and 4 presses must be suspended in the mold, and the operating pressure of the rider must be as follows: The specific embodiment of the ^ below. Under 135 C _ double roller mixed polystyrene and * with polyethylene resin, and then with other additions, the day 4 machine in the 赃 state, after pressing into the molded The foaming test step is first set to -^ and the temperature of the upper and lower jaws of the hot-pressed/forked puller is 'the basic set temperature is 120 °C 夕P bow/士, . λ ^ 4〇C. After the temperature is stable, put the ▲ plate in the hot stamping mold, close the nitrogen filling machine, and set the pressure in the nitrogen filling mold to the set pressure, and then pour it into the Π P02940027TW (Our Office No. 05P0324) 1314940 C〇2 The gas 'forms a mixture of nitrogen and co2 in the mold. The mixing ratio can be displayed by different pressures. The final impregnation pressure can be 2000~5000 psi, and the impregnation time can be calculated. When the impregnation time reaches the set time, it can be opened instantly. The mold allows the sheet to be freely foamed, or vented to a low pressure of 2000 to 1000 psi, left for a period of time (2 to 10 minutes) and then opened to obtain different foams. - The batch type foaming mold used in the following examples is designed as a circular mold' which takes into consideration the shape of the piston of the heat press and the average force. The mold has a design size of 300 mm inside diameter and 15 mm in depth, divided into upper and lower molds. The nitrogen and C02 injection ports are injected into the mold from the lower mold. However, the mold used in the present invention is not limited thereto, and those skilled in the art can adjust the mold size to be used as needed. The present invention is not limited to the details of the present invention. The present invention is not intended to limit the invention, and any person skilled in the art can make various kinds without departing from the spirit and scope of the invention. Change and retouch. • EXAMPLES Example 1 Production of Polystyrene Foam by the Method of the Present Invention This example was prepared using a batch process system as shown in the first figure - the polystyrene foam of the present invention. In this example, foams of various formulations were prepared, as shown in Table 1 below, wherein Formulation 1 was a control group of pure PS. The polystyrene (ps) used in this example has a molecular weight of 250 Å Mw, the polyethylene (PE) has a molecular weight of 260,000 Mw Å, and the chemical foaming agent ADCA is a commercially available product (commodity model: Taishin-250H). Put the foamed formula blended as shown in Table 1 into unfoamed sheet' and put it into the batch die at different foaming P02940027TW (Our Office No. 05P0324) 12 1314940 (Processing) temperature and processing pressure (33 〇〇pSi) is impregnated with c〇2 and Nz mixed gas, the ratio of mixed gas C〇2/N2 is 50/50, and the impregnation time is 90 minutes. Thereafter, the pressure was lowered to 13 psi for 1 minute, and then the mold was opened to obtain a PS foam or a PS/PE foam. These foams exhibit varying degrees of open porosity. The heat transfer coefficient of PS or ps/pe foams having substantially high open porosity is low. Table 1: Foam Formulation Formula 1 2 3 4 5 Polystyrene 100 98 95 93 --------- 90 Polyethylene 0 2 5 7 10 Carbon Black 0.3 0.3 0.3 0.3 —----- -- 0.3 Stearic acid approx. 1.0 1.0 1.0 1.0 1.0 Chemical foaming agent 2.0 2.0 2.0 2.0 2.0 ----* Yihuang: Take Maochao Ethylene foaming 艚·柞霞 wear insulation sheet and take it from the first example The polystyrene foam is cut into squares as shown in the second figure as the true heat preservation (four) correction, and then the core material is placed in a multi-layer bag and the heat-sealing heat seal is formed as shown in the third figure. Next, the internal structure of the foam body was studied and the heat transfer coefficient of the vacuum heat insulating sheet was measured. The fourth figure shows the results of the heat transfer coefficient of the vacuum insulation sheet made by the measuring PS (i.e., the formula i control group of Table 1) or the PS/PE mixed foam of the present invention. When the pure ps foam is at the foaming temperature of 12rc, 123. 〇, 125.匚 and i27C>c, the heat transfer coefficient variability is very large and the foaming temperature i2it^123〇c P02940027TW (Optical Case No. 〇5P〇324) 13 1314940 The ps foam obtained has a very low opening ratio. Its heat transfer coefficient is also very south. However, the PS/LDPE foam obtained by mixing PS and LDPE has a lower heat transfer coefficient, which represents an increase in the open cell ratio, especially the heat transfer coefficient of the PS/LDPE (7%) foam is very high at 4 foaming temperatures. Close, this means that the foaming rate of the foam does not change very much due to temperature changes during the foaming process' to help the production process to obtain a stable product. The fifth figure shows the heat transfer coefficient of vacuum insulation sheets in which various PS/PE foams are core materials. Polyethylene can be roughly classified into three categories: LDPE melting point of about 105 ° C ~ 115 ° C, linear polyethylene (LLDPE), melting point of about 115. 〇125. (: and high-density polyethylene (HDPE) melting point of about 130 ° C ~ 135 ° C, PS can be mixed with various proportions of PE to form a foam. The foaming process temperature used in this example is 125 ° C. From the results of this example, it was found that the thermal conductivity of the vacuum insulation sheet with PS/LDPE foam as the core material is lower than that of the vacuum insulation sheet of PS/LLDPE and PS/HDPE foam. The result shows that the PS/LDPE foam is used. The vacuum insulation sheet for the core material can exhibit better insulation effect. The sixth to ninth diagrams show the internal structure of the foam with heat transfer coefficients of 0.027, 0.02, 0.01 φ and 0.0065 W/mk, and the experimental results show heat conduction. The foam with a high coefficient has a low opening ratio of the foam, so that a foam having a heat transfer coefficient of 0.027 W/mk is observed, and it can be found that it is almost a closed cell structure (as shown in Fig. 6), and As the pore structure increases, the thermal conductivity of the foam decreases, so that the foam having a heat transfer coefficient of 0.0065 W/mk has a very high open pore structure. Styrene foam, true high Porosity and low heat transfer coefficient. Compared with the prior art, the open porosity of the foam can be improved, and nitrogen and carbon dioxide are not used as the physical foaming agent without using fluorine gas and chlorine gas. Therefore, it is environmentally friendly. P02940027TW Case No. 05P0324) 14 1314940 The method for producing a polystyrene foam of the present invention can be widely applied to the production of a vacuum heat insulating core material because it can greatly increase the opening ratio of the foam. Although the present invention has been preferred The embodiments are disclosed above, but are not intended to limit the scope of the present invention, and the scope of the present invention can be varied and modified without departing from the spirit and scope of the present invention. The embodiment of the present invention has been described in detail in the foregoing embodiments, and anyone skilled in the art can follow the description of the present invention. The present invention may be modified and modified as needed within the spirit and scope of the present invention. Therefore, other embodiments are also included in the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The first figure is a schematic diagram of the configuration of the batch foaming process and the high-pressure gas mixed gas filling pipeline of the present invention. The second drawing is a practical and bulk diagram of the polystyrene foam of the second embodiment of the present invention. The figure is a physical diagram of the vacuum heat insulating sheet according to the second embodiment of the present invention. The fourth figure is the heat conduction coefficient result of the vacuum heat insulating sheet made of PS or the PS/PE mixed foam of the present invention in the second embodiment of the present invention. The fifth figure is the heat transfer coefficient of the vacuum heat insulating sheet in which the various PS/ΡΕ foams are core materials in the second embodiment of the present invention. The sixth figure is the heat transfer coefficient of 0.027 W/mk in the second embodiment of the present invention. The internal structure of the bubble. The seventh figure is an internal structure diagram of a foam having a heat transfer coefficient of 0.02 W/m.k in the second embodiment of the present invention. P02940027TW (Originary Case No. 05P0324) 15 1314940 The eighth figure is an internal structure diagram of a foam having a heat transfer coefficient of 0.01 W/m.k in the second embodiment of the present invention. The ninth figure is an internal structure diagram of a foam having a heat transfer coefficient of 0.0065 W/m.k in the second embodiment of the present invention. ^ [Main component symbol comparison description] '1 high pressure steel cylinder 2 high pressure steel cylinder 3C02 gas booster 4 N2 gas booster 5 high pressure C02 gas filling machine 6 high pressure N2 filling machine 7 freezer
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