JPH052415B2 - - Google Patents
Info
- Publication number
- JPH052415B2 JPH052415B2 JP60038512A JP3851285A JPH052415B2 JP H052415 B2 JPH052415 B2 JP H052415B2 JP 60038512 A JP60038512 A JP 60038512A JP 3851285 A JP3851285 A JP 3851285A JP H052415 B2 JPH052415 B2 JP H052415B2
- Authority
- JP
- Japan
- Prior art keywords
- foam
- casting
- mold
- resin
- polypropylene resin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 229920005989 resin Polymers 0.000 claims description 34
- 239000011347 resin Substances 0.000 claims description 34
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 31
- 239000006260 foam Substances 0.000 claims description 28
- 238000005266 casting Methods 0.000 claims description 25
- 239000004743 Polypropylene Substances 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 18
- -1 polypropylene Polymers 0.000 claims description 18
- 229920001155 polypropylene Polymers 0.000 claims description 18
- 238000000605 extraction Methods 0.000 claims description 11
- 238000009835 boiling Methods 0.000 claims description 7
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 5
- 239000005977 Ethylene Substances 0.000 claims description 5
- 229920005674 ethylene-propylene random copolymer Polymers 0.000 claims description 5
- 239000004088 foaming agent Substances 0.000 claims description 4
- 239000012778 molding material Substances 0.000 claims description 3
- 238000001938 differential scanning calorimetry curve Methods 0.000 description 21
- 239000002245 particle Substances 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 238000010521 absorption reaction Methods 0.000 description 9
- 210000004027 cell Anatomy 0.000 description 9
- 239000013078 crystal Substances 0.000 description 9
- 238000005520 cutting process Methods 0.000 description 9
- 238000005187 foaming Methods 0.000 description 9
- 239000002023 wood Substances 0.000 description 8
- 230000006835 compression Effects 0.000 description 6
- 238000007906 compression Methods 0.000 description 6
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 239000004604 Blowing Agent Substances 0.000 description 4
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000000113 differential scanning calorimetry Methods 0.000 description 2
- 239000006261 foam material Substances 0.000 description 2
- 238000010097 foam moulding Methods 0.000 description 2
- 229920005604 random copolymer Polymers 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 241000218645 Cedrus Species 0.000 description 1
- 239000004338 Dichlorodifluoromethane Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- FMRLDPWIRHBCCC-UHFFFAOYSA-L Zinc carbonate Chemical compound [Zn+2].[O-]C([O-])=O FMRLDPWIRHBCCC-UHFFFAOYSA-L 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 210000000170 cell membrane Anatomy 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- PXBRQCKWGAHEHS-UHFFFAOYSA-N dichlorodifluoromethane Chemical compound FC(F)(Cl)Cl PXBRQCKWGAHEHS-UHFFFAOYSA-N 0.000 description 1
- 235000019404 dichlorodifluoromethane Nutrition 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229920005676 ethylene-propylene block copolymer Polymers 0.000 description 1
- 229920006248 expandable polystyrene Polymers 0.000 description 1
- 239000004794 expanded polystyrene Substances 0.000 description 1
- 229910001872 inorganic gas Inorganic materials 0.000 description 1
- 238000005495 investment casting Methods 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- UOURRHZRLGCVDA-UHFFFAOYSA-D pentazinc;dicarbonate;hexahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Zn+2].[Zn+2].[Zn+2].[Zn+2].[Zn+2].[O-]C([O-])=O.[O-]C([O-])=O UOURRHZRLGCVDA-UHFFFAOYSA-D 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920005672 polyolefin resin Polymers 0.000 description 1
- 229920005673 polypropylene based resin Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 229920006327 polystyrene foam Polymers 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 229920001384 propylene homopolymer Polymers 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- CYRMSUTZVYGINF-UHFFFAOYSA-N trichlorofluoromethane Chemical compound FC(Cl)(Cl)Cl CYRMSUTZVYGINF-UHFFFAOYSA-N 0.000 description 1
- 229940029284 trichlorofluoromethane Drugs 0.000 description 1
- 239000011667 zinc carbonate Substances 0.000 description 1
- 229910000010 zinc carbonate Inorganic materials 0.000 description 1
- 235000004416 zinc carbonate Nutrition 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
- B22C7/02—Lost patterns
- B22C7/023—Patterns made from expanded plastic materials
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Description
〔技術分野〕
本発明は、無架橋ポリプロピレン系樹脂型内発
泡成形体を主原料とした鋳造原型材料に関し、さ
らに詳しくは、微細な気泡径とすぐれた表面硬度
を有する無架橋ポリプロピレン系樹脂型内発泡成
形体を主原料とした鋳造用原型材料に関するもの
である。
〔従来技術〕
従来から鋳造用原型材料としては木材が主材料
として使用され、現在でも慣習的に杉等の木材が
使われている。木材は表面硬度が大きく、鋳型成
型時の寸法安定性がすぐれる等の特性を備えてい
るが、その反面、価格が高いこと、乾燥が必要な
こと、節や木目があるため加工に非常な熟練を要
すること、木材では重量が大きいため運搬に不便
であること、保存時に変形が生じた場合、使用の
都度修正をほどこす必要があることなどの欠点を
有している。
鋳造用木材原型材料に見られる以上のような欠
点から、近年では、ポリスチレンの型内発泡成形
体を鋳造用原型材料に用いる試みがなされてい
る。しかし、ポリスチレン発泡成形体は前述した
木材の欠点は解決するものの、逆に、発泡ポリス
チレンの本来の性質上、脆いという欠点を有する
ことから、木工用工具による加工において、引つ
かきキズがつき易い等の加工上の問題点を有して
いる。
特公昭47−43404号公報には、前記木材に見ら
れる欠点を解消するものとして、特定の方法で架
橋発泡して得られたゲル分率30〜90％、カサ密度
0.5〜0.05ｇ／cm3、平均気泡径が400μ以下の結晶
性ポリオレフイン樹脂架橋発泡体からなる鋳造用
原型材料が示されている。しかしながら、この鋳
造用原型材料は、発泡剤として熱分解型のアミド
類を使用する為に精密な鋳物の生産には使用でき
なく、しかも、いまだに吸水率が多いという欠点
を有し、そのため砂との離型性が悪く実際に使わ
れていないのが現実である。
〔目的〕
本発明は、従来の鋳造用発泡体原型材料に見ら
れる前記欠点を克服し、寸法精度の良好な鋳造物
を与える吸水率の小さな模型保管時変形がない鋳
造用発泡体原型材料を提供することを目的とす
る。
〔構成〕
本発明は、40％以下の沸騰ｎ−ヘプタン抽出残
渣割合を示すポリプロピレン系樹脂を基材樹脂と
する密度0.025超〜0.2以下ｇ／cm3で平均気泡径が
70μｍ〜1000μｍの非熱分解型発泡剤を用いて形
成された無架橋ポリプロピレン系樹脂型内発泡成
形体からなる鋳造用原型材料を要旨とする。
本発明において鋳造用原型材料として用いる発
泡体は、40％以下の沸騰ｎ−ヘプタン抽出残渣割
合を示すポリプロピレン系樹脂を基材樹脂とし、
このものを非熱分解型発泡剤を用いて形成した無
架橋ポリプロピレン系樹脂型内発泡体からなるも
ので、その密度（カサ密度）は0.025超〜0.2以下
ｇ／cm3の範囲に規定され、かつその平均気泡径は
70μｍ〜1000μｍの範囲に規定される。発泡体の
密度が前記範囲より大きくなると、機械的強度が
高く、寸法安定性は増すものの、逆に加工性が悪
化し、また重量も重くなるので好ましくなく、一
方、前記範囲より小さくなると、軽量化の点では
すぐれるものの、発泡体が柔軟になり、寸法安定
性に劣るようになるので好ましくない。本発明の
場合、発泡体の圧縮硬さ（JIS Ｋ−6767）は、一
般的には、0.7Kg／cm2以上に規定するのがよい。
また、発泡体の平均気泡径が前記範囲より小さく
なると、発泡体の切断加工が難かしくなると共
に、切断品の表面状態がセル膜の破れにより悪く
なるので好ましくなく、一方、前記範囲より大き
くなると、この場合も切断面の表面状態に荒れが
生じたり、また吸水率が高くなる等の難点が生じ
るので好ましくない。本発明の鋳造用原型材料樹
脂として用いるポリプロピレン系樹脂としては、
エチレン−プロピレンランダム共重合体、エチレ
ン−プロピレンブロツク共重合体、プロピレン単
独重合体、プロピレン−１−ブテンランダム共重
合体などが挙げられる。特に、これらの重合体の
中で、エチレン含有量0.5重量％〜10重量％、好
ましくは１重量％〜５重量％のエチレン−プロピ
レンランダム共重合体の使用が好ましい。
この場合、エチレン−プロピレンランダム共重
合体中のエチレン含有量が0.5重量％未満では、
発泡粒子が型内成形時に二次発泡しにくくなり、
得られる成形体の表面はボイドとよばれるくぼみ
が形成されやすくなる。一方、エチレン含有量が
10重量％を越えると得られる成形体は柔らかくな
り、場合によつては所望の形状の鋳造物が得られ
にくくなる。
また、ポリプロピレン系樹脂は、剛性ある発泡
体を得る点から40％以下の沸騰ｎ−ヘプタン抽出
残渣割合を示すものを使用する。この場合、ｎ−
ヘプタン抽出残渣割合は、立体規則性成分を意味
し、次の式で表わされる。
Ｒ（％）＝Ｌ／Ｍ×100
Ｒ：ｎ−ヘプタン抽出残渣割合（％）
Ｌ：ｎ−ヘプタン８時間抽出後の不溶分の重量
Ｍ：ｎ−ヘプタン抽出前の重量
40％を越える沸騰ｎ−ヘプタン抽出残渣割合を
示すポリプロピレン系樹脂は得られる鋳造用原型
材料が柔軟となり、時によつては鋳造砂の重量に
より鋳造用原型材料が変形してしまい、所望形状
の鋳造物が得られなくなるので好ましくない。
本発明において、前記のポリプロピレン系樹脂
はそれぞれ単独でも用いられる他、複数をブレン
ドして使用しても良く、ブレンドの場合、そのブ
レンド比率は任意である。
本発明の鋳造用原型材料は、前記樹脂粒子を発
泡させて形成したいわゆる無架橋予備発泡粒子か
ら形成した型内無架橋発泡成形体からなるもので
あるが、この場合、予備発泡粒子は、オートクレ
ーブに樹脂粒子、水、融着防止剤、発泡剤を配合
し、加圧下、発泡温度まで昇温し、容器の一端を
開放して内容物を低圧帯域に放出させることによ
つて得ることができる。この場合、融着防止剤と
しては、例えば、酸化アルミニウム、酸化チタ
ン、水酸化アルミニウム、塩基性炭酸マグネシウ
ム、塩基性炭酸亜鉛、炭酸亜鉛等が挙げられ、発
泡剤としては、非熱分解型発泡剤であるプロパ
ン、ブタン、ペンタン、トリクロロフロロメタ
ン、ジクロロジフロロメタン等の揮発性有機発泡
剤の他、二酸化炭素、窒素、空気等の無機系ガス
が挙げられる。
前記のようにして得られた予備発泡粒子は、こ
れを耐圧容器中で空気で加圧し、粒子内に0.5〜
３Kg／cm2Ｇ程度の粒子内圧を持たせた後、成形用
金型内に入れ、加熱発泡させて、発泡成形体とな
し、次いで冷却して金型から取出す。このように
して得た無架橋ポリプロピレン系樹脂型内発泡成
形体を乾燥し、鋳造用原型材料として使用する。
本発明においては、発泡成形体を構成する樹脂
は、二次結晶構造を有するのが好ましい。二次結
晶構造を有する発泡成形体は、圧縮硬さ、圧縮永
久歪率、吸水率等の諸特性にすぐれ、有利な鋳造
用原型を与える。このような二次結晶構造を有す
る発泡成形体は、樹脂粒子を予備発泡させる場
合、発泡温度として、樹脂の融点以上、融解終了
温度未満の温度を用いることによつて、二次結晶
構造を有する予備発泡粒子を作り、この予備発泡
粒子を成形用金型に入れ、発泡成形することによ
つて得ることができる。樹脂の融解終了温度以上
の発泡温度を用いて予備発泡粒子を得る場合、二
次結晶構造を有するものを得るには、樹脂をその
融解終了温度未満の温度に充分保持し、その二次
結晶化を充分起させた後、発泡温度に昇温し、発
泡を行うことが必要である。
なお、発泡体樹脂中における二次結晶の存在
は、発泡樹脂の示差走査熱量測定によつて得られ
たDSC曲線によつて判定することができる。こ
の場合、発泡樹脂の示差走査熱量測定によつて得
られるDSC曲線とは、ポリプロピレン系樹脂発
泡粒子又は成形体１〜３mgを示差走査熱量計によ
つて10℃／分の昇温速度で220℃まで昇温したと
きに得られるDSC曲線である。このDSC曲線を
用いて二次結晶構造の有無を判定するには、例え
ば、試料を室温から220℃まで10℃／分の昇温速
度で昇温した時に得られるDSC曲線を第１回目
のDSC曲線とし、次いで220℃から10℃／分の降
温速度で40℃付近まで降温し、再度10℃／分の昇
温速度で220℃まで昇温した時に得られるDSC曲
線を第２回目のDSC曲線とし、これらのDSC曲
線から固有ピーク、高温ピークを求める。この場
合、固有ピークとは、発泡樹脂を構成するポリプ
ロピレン系樹脂固有の吸熱ピークであり、ポリプ
ロピレン系樹脂のいわゆる融解時の吸熱によるも
のであると考えられる。この固有ピークは第１回
目のDSC曲線にも第２回目のDSC曲線にも現わ
れ、ピークの頂点の温度は第１回目と第２回目で
多少異なる場合があるが、その差は５℃未満、通
常は２℃未満である。一方、高温ピークとは、第
１回目のDSC曲線で上記固有ピークより高温側
に現われる吸熱ピークである。発泡樹脂中におけ
る二次結晶の存在は、DSC曲線にこの高温ピー
クが現われるか否かで判定され、実質的な高温ピ
ークが現われない場合には、樹脂中には二次結晶
が存在しないものと判定される。二次結晶構造を
有する好ましい発泡体を得るには、前記第２回目
のDSC曲線に現われる固有ピークの温度と第１
回目のDSC曲線に現われる高温ピークの温度と
の差を大きくすることが望ましく、第２回目の
DSC曲線の固有ピークの頂点の温度との差は５
℃以上、好ましくは10℃以上である。
図面に、前記したDSC曲線の代表的なものを
示す。この図において、曲線−１は第１回目の
DSC曲線を示し、曲線−２は第２回目のDSC曲
線を示し、また吸熱ピークａ及びa′は固有ピーク
を示し、ｂは高温ピークを示す。
〔効果〕
本発明の鋳造用原型材料は、前記した特定の発
泡体からなるもので、従来の木材や、発泡体から
なるものと同様に使用されるが、本発明で用いる
発泡体は、切断加工性にすぐれるため、従来の木
型模型を製造する場合に用いた工具がそのまま使
用できる利点がある上、表面平滑でかつ高い圧縮
硬さを有し、さらに有利なことには、吸水率の著
しく小さなものであることから、寸法安定性にす
ぐれた鋳造用原型材料を与える。また、本発明の
鋳造用原型材料は、圧縮硬さが高くかつ吸水率の
小さなものであることから、離型性に著しくすぐ
れたものである。
〔実施例〕
次に本発明を実施例によりさらに詳細に説明す
る。
実施例１〜２、比較例１〜５
エチレン−プロピレンランダム共重合体（エチ
レン含有率：2.7重量％、沸騰ｎ−ヘプタン抽出
残渣割合：15％）から得られた嵩密度0.15〜
0.019ｇ／cm3、平均気泡径25μｍ〜2000μｍの種々
の予備発泡粒子を用いて、これを成形金型内で加
熱して、型内発泡成形体を得た。次に、得られた
成形体の密度、平均気泡径を測定すると共に、そ
の圧縮カタさ、吸水率、切断加工難易度、切断表
面状態をそれぞれ下記に示す基準で評価し、その
結果を第１表に示す。なお、切断加工難易度は、
型内成形体をバンドソーにより厚さ10mmに切断加
工を行ない、その際の切断加工の難易度にて評価
し、また切断品の表面状態は、その際に得られる
切断品の表面状態を目視観察により評価した。
(1) 切断加工の難易度：
○……切断時に抵抗が少なくスムースに切断で
きる。
△……切断時に抵抗はあるが一応切断できる。
×……切断時に抵抗が大きく振動を発生する。
(2) 切断品の表面状態：
○……表面が滑らか。
△……表面に若干荒れがある。
×……表面が荒れかつもげる粒子がある。
(3) 圧縮カタサ（JIS−Ｋ−6767に準拠）：
○……0.7Kg／cm2以上
△……0.7Kg／cm2〜0.4Kg／cm2
×……0.4Kg／cm2以下
(4) 吸水率（JIS−Ｋ−6767B法）：
○……0.003ｇ／cm3未満
△……0.03〜0.003ｇ／cm3
×……0.03ｇ／cm3以上
(5) 寸法変化率（１ケ月間室温放置）
○……１％以下
△……１％超〜２％未満
×……２％以上
[Technical Field] The present invention relates to a casting mold material whose main raw material is a non-crosslinked polypropylene resin in-mold foam molded product, and more specifically, the present invention relates to a casting material made from a non-crosslinked polypropylene resin in-mold foam molded product, and more specifically, it relates to a non-crosslinked polypropylene resin in-mold foam molded product having a fine cell diameter and excellent surface hardness. This invention relates to a mold material for casting whose main raw material is a foam molded body. [Prior Art] Wood has traditionally been used as the main material for casting molds, and wood such as cedar is still customarily used today. Wood has characteristics such as high surface hardness and excellent dimensional stability when molded, but on the other hand, it is expensive, requires drying, and has knots and grain, making it extremely difficult to process. Disadvantages include that it requires skill, that wood is inconvenient to transport due to its large weight, and that if deformation occurs during storage, it must be corrected each time it is used. Due to the above-mentioned drawbacks found in wood casting materials, attempts have been made in recent years to use in-mold foam molded bodies of polystyrene as casting materials. However, although polystyrene foam moldings solve the above-mentioned drawbacks of wood, they also have the drawback of being brittle due to the inherent nature of foamed polystyrene, so they tend to get stuck and scratched when processed with woodworking tools. It has processing problems such as. Japanese Patent Publication No. 47-43404 describes a product with a gel fraction of 30 to 90% and a bulk density obtained by crosslinking and foaming using a specific method, as a method to eliminate the defects found in the wood.
A casting master material made of a crosslinked crystalline polyolefin resin foam having a weight of 0.5 to 0.05 g/cm 3 and an average cell diameter of 400 μm or less is shown. However, because this casting material uses pyrolytic amides as a blowing agent, it cannot be used to produce precision castings, and it still has the disadvantage of high water absorption, so it is not compatible with sand. The reality is that it has poor mold releasability and is not actually used. [Objective] The present invention overcomes the above-mentioned drawbacks found in conventional foam material for casting, and provides a foam material for casting that has a low water absorption rate and does not deform during storage of models, giving castings with good dimensional accuracy. The purpose is to provide. [Structure] The present invention is based on a polypropylene resin having a boiling n-heptane extraction residue ratio of 40% or less, with a density of more than 0.025 to less than 0.2 g/cm 3 and an average cell diameter of 40% or less.
The gist of the present invention is a mold material for casting consisting of a non-crosslinked polypropylene resin in-mold foam molded product formed using a non-pyrolyzable foaming agent with a diameter of 70 μm to 1000 μm. The foam used as the casting material in the present invention has a base resin of polypropylene resin having a boiling n-heptane extraction residue ratio of 40% or less,
This product is made of a non-crosslinked polypropylene resin in-mold foam formed using a non-pyrolytic foaming agent, and its density (bulk density) is defined in the range of more than 0.025 to less than 0.2 g/cm 3 , And the average bubble diameter is
It is defined in the range of 70 μm to 1000 μm. If the density of the foam is larger than the above range, the mechanical strength will be high and the dimensional stability will increase, but workability will deteriorate and the weight will also increase, which is undesirable. On the other hand, if the density is smaller than the above range, the weight will increase Although this method is excellent in terms of flexibility, it is not preferable because the foam becomes flexible and has poor dimensional stability. In the case of the present invention, the compression hardness (JIS K-6767) of the foam is generally preferably set to 0.7 kg/cm 2 or more.
Furthermore, if the average cell diameter of the foam is smaller than the above range, it becomes difficult to cut the foam and the surface condition of the cut product deteriorates due to tearing of the cell membrane, which is undesirable. In this case as well, problems such as roughness of the cut surface and increased water absorption occur, which is not preferable. The polypropylene resin used as the mold material resin for casting of the present invention includes:
Examples include ethylene-propylene random copolymer, ethylene-propylene block copolymer, propylene homopolymer, and propylene-1-butene random copolymer. Among these polymers, it is particularly preferred to use ethylene-propylene random copolymers having an ethylene content of 0.5% to 10% by weight, preferably 1% to 5% by weight. In this case, if the ethylene content in the ethylene-propylene random copolymer is less than 0.5% by weight,
The foamed particles are less likely to undergo secondary foaming during in-mold molding,
The surface of the resulting molded product tends to have depressions called voids. On the other hand, the ethylene content
When the amount exceeds 10% by weight, the resulting molded product becomes soft, and in some cases, it becomes difficult to obtain a cast product with a desired shape. Further, the polypropylene resin used has a boiling n-heptane extraction residue ratio of 40% or less in order to obtain a rigid foam. In this case, n-
The heptane extraction residue ratio means a stereoregular component and is expressed by the following formula. R (%) = L/M x 100 R: n-heptane extraction residue ratio (%) L: weight of insoluble matter after 8 hours of n-heptane extraction M: weight before n-heptane extraction Boiling n exceeding 40% -Polypropylene-based resins with a heptane extraction residue ratio make the resulting casting material flexible, and sometimes the weight of the casting sand deforms the casting material, making it impossible to obtain a cast product of the desired shape. Undesirable. In the present invention, the polypropylene resins described above may be used alone or in a blend of two or more, and in the case of a blend, the blend ratio is arbitrary. The molding material for casting of the present invention consists of an in-mold non-crosslinked foamed molded product formed from so-called non-crosslinked pre-foamed particles formed by foaming the resin particles. In this case, the pre-foamed particles are It can be obtained by blending resin particles, water, an anti-fusing agent, and a foaming agent into a foam, raising the temperature to the foaming temperature under pressure, and opening one end of the container to release the contents into a low-pressure zone. . In this case, the anti-fusing agent includes, for example, aluminum oxide, titanium oxide, aluminum hydroxide, basic magnesium carbonate, basic zinc carbonate, zinc carbonate, etc., and the blowing agent includes a non-pyrolytic blowing agent. Examples include volatile organic blowing agents such as propane, butane, pentane, trichlorofluoromethane, and dichlorodifluoromethane, as well as inorganic gases such as carbon dioxide, nitrogen, and air. The pre-expanded particles obtained as described above are pressurized with air in a pressure-resistant container to form particles with a concentration of 0.5 to
After giving the particles an internal pressure of about 3 kg/cm 2 G, they are placed in a mold, heated and foamed to form a foam molded product, and then cooled and taken out from the mold. The non-crosslinked polypropylene resin in-mold foamed molded product thus obtained is dried and used as a mold material for casting. In the present invention, the resin constituting the foamed molded product preferably has a secondary crystal structure. A foam molded article having a secondary crystal structure has excellent properties such as compression hardness, compression set rate, and water absorption rate, and provides an advantageous mold for casting. A foam molded product having such a secondary crystal structure can be obtained by using a temperature higher than the melting point of the resin and lower than the melting end temperature as the foaming temperature when pre-foaming the resin particles. It can be obtained by preparing pre-expanded particles, placing the pre-expanded particles into a mold and performing foam molding. When obtaining pre-expanded particles using a foaming temperature higher than the melting end temperature of the resin, in order to obtain particles with a secondary crystal structure, the resin must be sufficiently maintained at a temperature below its melting end temperature to prevent its secondary crystallization. After sufficiently raising the temperature, it is necessary to raise the temperature to the foaming temperature and perform foaming. The presence of secondary crystals in the foam resin can be determined based on a DSC curve obtained by differential scanning calorimetry of the foam resin. In this case, the DSC curve obtained by differential scanning calorimetry of the foamed resin means that 1 to 3 mg of expanded polypropylene resin particles or molded products are measured at a heating rate of 10°C/min to 220°C using a differential scanning calorimeter. This is a DSC curve obtained when the temperature is raised to . To determine the presence or absence of a secondary crystal structure using this DSC curve, for example, the DSC curve obtained when the sample is heated from room temperature to 220°C at a heating rate of 10°C/min is used for the first DSC curve. The second DSC curve is the DSC curve obtained when the temperature is lowered from 220°C to around 40°C at a cooling rate of 10°C/min, and then raised again to 220°C at a heating rate of 10°C/min. Then, find the unique peak and high temperature peak from these DSC curves. In this case, the characteristic peak is an endothermic peak unique to the polypropylene resin constituting the foamed resin, and is considered to be due to the so-called endotherm of the polypropylene resin during melting. This unique peak appears in both the first DSC curve and the second DSC curve, and the temperature at the top of the peak may be slightly different between the first and second times, but the difference is less than 5 degrees Celsius. Usually below 2°C. On the other hand, the high temperature peak is an endothermic peak that appears on the higher temperature side than the above-mentioned characteristic peak in the first DSC curve. The presence of secondary crystals in the foamed resin is determined by whether or not this high temperature peak appears in the DSC curve. If no substantial high temperature peak appears, it is assumed that there are no secondary crystals in the resin. It will be judged. In order to obtain a preferable foam having a secondary crystal structure, the temperature of the characteristic peak appearing in the second DSC curve and the temperature of the characteristic peak appearing in the second DSC curve and the first
It is desirable to increase the difference between the temperature of the high temperature peak that appears in the DSC curve of the second
The difference between the temperature at the top of the characteristic peak of the DSC curve is 5
℃ or higher, preferably 10℃ or higher. The drawing shows a typical DSC curve described above. In this figure, curve-1 is the first
The DSC curves are shown, curve-2 is the second DSC curve, endothermic peaks a and a' are characteristic peaks, and b is the high temperature peak. [Effects] The molding material for casting of the present invention is made of the above-mentioned specific foam and is used in the same way as conventional materials made of wood or foam. Because it has excellent workability, it has the advantage that the tools used for manufacturing conventional wooden models can be used as is, and it has a smooth surface and high compressive hardness, and even more advantageously, it has a low water absorption rate. Because of its extremely small size, it provides a casting material with excellent dimensional stability. Further, the casting mold material of the present invention has high compressive hardness and low water absorption, so it has extremely excellent mold releasability. [Example] Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 2, Comparative Examples 1 to 5 Bulk density 0.15 to 5 obtained from ethylene-propylene random copolymer (ethylene content: 2.7% by weight, boiling n-heptane extraction residue ratio: 15%)
Various pre-expanded particles having a weight of 0.019 g/cm 3 and an average cell diameter of 25 μm to 2000 μm were used and heated in a mold to obtain an in-mold foamed molded product. Next, the density and average cell diameter of the obtained molded body were measured, and its compression shape, water absorption rate, cutting difficulty, and cutting surface condition were evaluated using the criteria shown below. Shown in the table. In addition, the difficulty of cutting process is as follows:
The molded body in the mold was cut to a thickness of 10 mm using a band saw, and the difficulty of the cutting process was evaluated.The surface condition of the cut product was visually observed. Evaluated by. (1) Difficulty of cutting process: ○...There is little resistance during cutting and it can be cut smoothly. △...There is some resistance when cutting, but it is possible to cut. ×...The resistance is large and vibrations occur during cutting. (2) Surface condition of cut product: ○...The surface is smooth. △...The surface is slightly rough. ×...There are particles with rough and peeling surfaces. (3) Compression flatness (according to JIS-K-6767): ○...0.7Kg/cm 2 or more △...0.7Kg/cm 2 ~ 0.4Kg/cm 2 ×...0.4Kg/cm 2 or less (4) Water absorption rate (JIS-K-6767B method): ○...Less than 0.003g/ cm3 △...0.03~0.003g/cm3 × ...0.03g/cm3 or more (5) Dimensional change rate (1 month at room temperature Left unattended) ○...1% or less △...More than 1% to less than 2% ×...2% or more
【表】
＊ 発泡体として、発泡ポリスチレンを使用した。
実施例 ３
プロピレン・１−プテンランダム共重合体（１
−ブテン含有量6.0重量％、沸騰ｎ−ヘプタン抽
出残渣割合：１％）から得られた嵩密度0.03ｇ／
cm3、平均気泡径800μｍの予備発泡粒子を用いた
以外は実施例１〜２及び比較例１〜５と同様に成
形体を得、同様に種々の加工等を行なつた。その
結果を以下に示す。
発泡体密度（ｇ／cm3） 0.03
平均気泡径（μｍ） 800
圧縮硬さ（Kg／cm2） ○
切断加工の難易度 ○
切断品の表面状態 ○
吸水率 ○
寸法変化率 ○[Table] * Expanded polystyrene was used as the foam.
Example 3 Propylene/1-butene random copolymer (1
-Bulk density 0.03g/- obtained from (butene content 6.0% by weight, boiling n-heptane extraction residue ratio: 1%)
A molded article was obtained in the same manner as in Examples 1 to 2 and Comparative Examples 1 to 5, except that pre-expanded particles having a cell diameter of 800 μm and an average cell diameter of 800 μm were used, and various treatments were carried out in the same manner. The results are shown below. Foam density (g/cm 3 ) 0.03 Average cell diameter (μm) 800 Compression hardness (Kg/cm 2 ) ○ Difficulty of cutting ○ Surface condition of cut product ○ Water absorption rate ○ Dimensional change rate ○
図面は無架橋ポリプロピレン系樹脂発泡体の
DSC曲線を示す。
The drawing shows non-crosslinked polypropylene resin foam.
A DSC curve is shown.
Claims (1)
示すポリプロピレン系樹脂を基材樹脂とする密度
0.025超〜0.2以下ｇ／cm3で平均気泡径が70μｍ〜
1000μｍの非熱分解型発泡剤を用いて形成された
無架橋ポリプロピレン系樹脂型内発泡成形体から
なる鋳造用原型材料。 ２ ポリプロピレン系樹脂がエチレン成分0.5〜
10重量％のエチレン−プロピレンランダム共重合
体よりなる特許請求の範囲第１項記載の鋳造用原
型材料。[Claims] 1. Density using a polypropylene resin as a base resin showing a boiling n-heptane extraction residue ratio of 40% or less
More than 0.025 to less than 0.2 g/cm 3 and average bubble diameter of 70 μm or more
A molding material for casting consisting of a non-crosslinked polypropylene resin in-mold foam molded product formed using a 1000μm non-pyrolytic foaming agent. 2 Polypropylene resin has an ethylene content of 0.5~
The casting material according to claim 1, comprising 10% by weight of an ethylene-propylene random copolymer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3851285A JPS61199544A (en) | 1985-02-27 | 1985-02-27 | Material for master mold for casting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3851285A JPS61199544A (en) | 1985-02-27 | 1985-02-27 | Material for master mold for casting |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61199544A JPS61199544A (en) | 1986-09-04 |
| JPH052415B2 true JPH052415B2 (en) | 1993-01-12 |
Family
ID=12527320
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3851285A Granted JPS61199544A (en) | 1985-02-27 | 1985-02-27 | Material for master mold for casting |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61199544A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53131227A (en) * | 1977-04-22 | 1978-11-15 | Hitachi Ltd | Model for casting |
| JPS57165156A (en) * | 1981-03-16 | 1982-10-12 | Union Giken Kk | Investment casting method |
-
1985
- 1985-02-27 JP JP3851285A patent/JPS61199544A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53131227A (en) * | 1977-04-22 | 1978-11-15 | Hitachi Ltd | Model for casting |
| JPS57165156A (en) * | 1981-03-16 | 1982-10-12 | Union Giken Kk | Investment casting method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61199544A (en) | 1986-09-04 |
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