JP5253123B2 - Method for producing foamed molded article in polypropylene resin mold by compression filling method - Google Patents
Method for producing foamed molded article in polypropylene resin mold by compression filling method Download PDFInfo
- Publication number
- JP5253123B2 JP5253123B2 JP2008313332A JP2008313332A JP5253123B2 JP 5253123 B2 JP5253123 B2 JP 5253123B2 JP 2008313332 A JP2008313332 A JP 2008313332A JP 2008313332 A JP2008313332 A JP 2008313332A JP 5253123 B2 JP5253123 B2 JP 5253123B2
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- JP
- Japan
- Prior art keywords
- polypropylene resin
- particles
- mold
- foam
- weight
- 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.)
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- 229920005989 resin Polymers 0.000 title claims description 142
- 239000011347 resin Substances 0.000 title claims description 142
- -1 polypropylene Polymers 0.000 title claims description 136
- 239000004743 Polypropylene Substances 0.000 title claims description 123
- 229920001155 polypropylene Polymers 0.000 title claims description 123
- 238000000034 method Methods 0.000 title claims description 39
- 230000006835 compression Effects 0.000 title claims description 29
- 238000007906 compression Methods 0.000 title claims description 29
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 239000002245 particle Substances 0.000 claims description 205
- 239000006260 foam Substances 0.000 claims description 72
- 238000010438 heat treatment Methods 0.000 claims description 36
- 238000005187 foaming Methods 0.000 claims description 35
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 32
- 239000004088 foaming agent Substances 0.000 claims description 20
- 239000001569 carbon dioxide Substances 0.000 claims description 16
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 16
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 14
- 239000005977 Ethylene Substances 0.000 claims description 14
- 239000002612 dispersion medium Substances 0.000 claims description 5
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- 239000000463 material Substances 0.000 claims description 4
- 239000000126 substance Substances 0.000 description 31
- 230000004927 fusion Effects 0.000 description 23
- 238000002844 melting Methods 0.000 description 23
- 230000008018 melting Effects 0.000 description 23
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- 238000010097 foam moulding Methods 0.000 description 18
- 239000002667 nucleating agent Substances 0.000 description 13
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
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- 230000000052 comparative effect Effects 0.000 description 6
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- 239000003054 catalyst Substances 0.000 description 4
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- 229920001400 block copolymer Polymers 0.000 description 2
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- LPIQUOYDBNQMRZ-UHFFFAOYSA-N cyclopentene Chemical compound C1CC=CC1 LPIQUOYDBNQMRZ-UHFFFAOYSA-N 0.000 description 2
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- 229920005674 ethylene-propylene random copolymer Polymers 0.000 description 2
- 239000003063 flame retardant Substances 0.000 description 2
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- BIKXLKXABVUSMH-UHFFFAOYSA-N trizinc;diborate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]B([O-])[O-].[O-]B([O-])[O-] BIKXLKXABVUSMH-UHFFFAOYSA-N 0.000 description 2
- 239000004711 α-olefin Substances 0.000 description 2
- OJOWICOBYCXEKR-APPZFPTMSA-N (1S,4R)-5-ethylidenebicyclo[2.2.1]hept-2-ene Chemical compound CC=C1C[C@@H]2C[C@@H]1C=C2 OJOWICOBYCXEKR-APPZFPTMSA-N 0.000 description 1
- QEQBMZQFDDDTPN-UHFFFAOYSA-N (2-methylpropan-2-yl)oxy benzenecarboperoxoate Chemical compound CC(C)(C)OOOC(=O)C1=CC=CC=C1 QEQBMZQFDDDTPN-UHFFFAOYSA-N 0.000 description 1
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- RIPYNJLMMFGZSX-UHFFFAOYSA-N (5-benzoylperoxy-2,5-dimethylhexan-2-yl) benzenecarboperoxoate Chemical compound C=1C=CC=CC=1C(=O)OOC(C)(C)CCC(C)(C)OOC(=O)C1=CC=CC=C1 RIPYNJLMMFGZSX-UHFFFAOYSA-N 0.000 description 1
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- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
- B29C44/44—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length in solid form
- B29C44/445—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length in solid form in the form of expandable granules, particles or beads
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3442—Mixing, kneading or conveying the foamable material
- B29C44/3446—Feeding the blowing agent
- B29C44/3453—Feeding the blowing agent to solid plastic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3461—Making or treating expandable particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
- B29C44/3426—Heating by introducing steam in the mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/10—Polymers of propylene
- B29K2023/12—PP, i.e. polypropylene
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Molding Of Porous Articles (AREA)
Description
本発明はポリプロピレン系樹脂型内発泡成形体の製造方法に関する。特に圧縮充填法によるポリプロピレン系樹脂型内発泡成形体の製造方法に関する。 The present invention relates to a method for producing a foamed molded product in a polypropylene resin mold. In particular, the present invention relates to a method for producing a foamed molded product in a polypropylene resin mold by a compression filling method.
ポリプロピレン系樹脂発泡体は緩衝性、断熱性等の物性に優れることから、包装材、緩衝材、断熱材、建築部材など様々な用途に使用されている。特に図１に示すような成形機を用い、ポリプロピレン系樹脂発泡粒子を金型に充填し、水蒸気などで加熱して発泡粒子同士を融着せしめて所定形状の発泡体を得るビーズ法型内発泡成形法は、複雑な形状の製品を比較的容易に得ることができるため、多くの用途に用いられている。 Polypropylene-based resin foams are excellent in physical properties such as buffering properties and heat insulating properties, and are therefore used in various applications such as packaging materials, buffer materials, heat insulating materials, and building materials. In particular, using a molding machine as shown in FIG. 1, foaming with polypropylene resin foam particles in a mold and heating with steam or the like to fuse the foam particles together to obtain a foam with a predetermined shape is used. The molding method is used in many applications because a product having a complicated shape can be obtained relatively easily.
ビーズ法型内発泡成形法に使用するポリプロピレン系樹脂発泡粒子は、耐圧容器内にポリプロピレン系樹脂粒子を水系分散媒に分散剤を用いて分散させ、炭化水素等の発泡剤を添加し、ポリプロピレン系樹脂粒子の軟化温度以上の温度まで加熱し発泡剤をポリプロピレン系樹脂粒子に含浸させた後、耐圧容器の内圧よりも低い圧力域に放出することにより製造することができる。高発泡倍率の発泡粒子が必要な場合、得られた発泡粒子に加圧下に空気等を含浸させた後、常圧下で加熱することにより、さらに発泡させた発泡粒子を得ることもできる。 Polypropylene resin foam particles used in the bead method in-mold foam molding method, polypropylene resin particles are dispersed in a pressure-resistant container using a dispersant in an aqueous dispersion medium, and a foaming agent such as hydrocarbon is added. It can be manufactured by heating to a temperature equal to or higher than the softening temperature of the resin particles and impregnating the polypropylene-based resin particles with a foaming agent, and then releasing it into a pressure range lower than the internal pressure of the pressure vessel. When expanded particles with a high expansion ratio are required, the expanded particles thus obtained can be impregnated with air or the like under pressure, and then heated under normal pressure to obtain further expanded expanded particles.
ビーズ法型内発泡成形法においては、上記したように、ポリプロピレン系樹脂発泡粒子を金型の型窩内に充填し、水蒸気などで加熱して発泡粒子同士を融着せしめて所定形状の発泡体を製造する。金型の型窩内に充填する際、用いる発泡粒子に対しては、一般的にはイ）そのまま充填する、ロ）あらかじめポリプロピレン系樹脂発泡粒子中に空気等の無機ガスを圧入し、発泡能を付与してから充填する（以下、内圧付与法という）、ハ）ポリプロピレン系樹脂発泡粒子を圧縮状態で金型内に充填する（圧縮充填法）、等の処理がなされている。これらの中でも、圧縮充填法は発泡粒子に発泡能が付与されているので発泡粒子間の融着性や得られる型内発泡成形体の表面平滑性に優れている。また、圧縮充填法は内圧付与法に比較し、内圧付与のための設備が不要で成形サイクルも短いという利点がある。 In the bead method in-mold foam molding method, as described above, polypropylene-based resin foam particles are filled in the mold cavity of the mold and heated with water vapor or the like to fuse the foam particles with each other to obtain a foam having a predetermined shape. Manufacturing. When filling into the mold cavity of the mold, the foamed particles to be used are generally a) filled as it is, and b) by blowing an inorganic gas such as air into the polypropylene resin foamed particles in advance. And then filling (hereinafter, referred to as an internal pressure application method), c) processing such as filling polypropylene resin expanded particles into a mold in a compressed state (compression filling method), and the like. Among these, the compression filling method is excellent in the fusibility between the foamed particles and the surface smoothness of the in-mold foam molded product obtained because the foamed particles are given foaming ability. Further, the compression filling method has an advantage that an equipment for applying an internal pressure is not required and a molding cycle is short as compared with the internal pressure applying method.
ビーズ法型内発泡成形法においては、金型に取り付けられている充填機を使用して発泡粒子を金型の型窩内に充填する。図１に示すように、通常用いられる充填機１６では、空気の流れに発泡粒子を同伴させて型窩７内に発泡粒子を送り込む機構が採用される。金型は、発泡粒子を通さないが空気や蒸気を通すことができる通気口８を有する。発泡粒子が金型内に送り込まれると空気は通気口８を通って金型の型窩７外に排出され、発泡粒子は型窩７内に残留する。発泡粒子が型窩７内に十分充填されると空気が型窩７内に侵入せず発泡粒子圧縮タンク１に逆流する。このとき充填機１６内に存在する発泡粒子は押し戻され充填機１６は空になる。この工程は自然ブローバックと呼ばれている。充填機１６内の発泡粒子が除去された後、ピストンプラグ１９により、金型の発泡粒子充填口１８が閉塞され、引き続いて蒸気加熱により型内発泡成形がなされる。
In the bead method in-mold foam molding method, foam particles are filled into the mold cavity of the mold by using a filling machine attached to the mold. As shown in FIG. 1, the normally used
しかしながら、金型の発泡粒子充填口１８付近において型内発泡成形体の融着不良が生じやすいことが知られている。この様な欠陥の存在は、型内発泡成形体の商品価値を著しく損なうもので、好ましくない。特許文献１によれば金型の発泡粒子充填口付近において型内発泡成形体の融着不良が生じやすい理由について次のように説明されている。発泡粒子の金型への充填工程における自然ブローバックによって充填機内の発泡粒子が完全に除去されず一部が残存する。残存した発泡粒子はピストンプラグにより金型型窩内に押し込まれるが、これにより金型型窩の発泡粒子充填口付近に発泡粒子が過剰に充填される。この現象は過充填と呼ばれており、過充填が生じるとこの部分に加熱蒸気が通過しにくくなり、当該部位に部分的に融着不良を有する型内発泡成形体となる。過充填が生じない場合であっても金型の発泡粒子充填口付近は空気や蒸気の通気口が少ない場合があり、加熱蒸気が流通しにくくなって融着不良を生じる場合もある。
However, it is known that in-mold foam moldings are likely to have poor fusion in the vicinity of the foamed
特許文献１には、ブローバック時に金型内圧力を充填機内の圧力より高くなるように調整することにより、発泡粒子充填口付近の融着不良を防止できることが開示されている。また、特許文献２には発泡粒子充填口を閉塞するのにピストンプラグでなく充填口に設けたシャッターを用いて、充填機内に発泡粒子が残存しても、残存発泡粒子が金型内に押し込まれないようにして過充填を防止する方法が開示されている。特許文献１や特許文献２に開示された方法は、成形装置において発泡粒子充填口付近の融着不良を防止する方法である。しかし、発泡粒子の特性を特定することにより過充填を防止する方法は知られていない。
本発明の課題はビーズ法型内発泡成形法において、発泡粒子の特性を特定することによる金型の充填機取り付け部位付近の融着不良が発生しないポリプロピレン系樹脂型内発泡成形体の製造方法を提供することにある。 An object of the present invention is to provide a method for producing a foam-in-mold molded product in a polypropylene-based resin mold in which inadequate fusing failure occurs in the vicinity of a mold filling machine attachment site by specifying the characteristics of foamed particles in a bead method in-mold foam molding method. It is to provide.
本発明者らは、圧縮充填法を用いるビーズ法型内発泡成形法において、金型の充填機取り付け部位付近の融着不良を発生させない方法について検討した結果、特に、発泡剤としてブタン等の炭化水素を用いて得られたポリプロピレン系樹脂発泡粒子を使用し、圧縮充填法によって成形した型内発泡成形体における発泡粒子充填口付近の融着不良が多く発生することが判明した。 The inventors of the present invention have studied a method that does not cause poor fusion in the vicinity of a die filling machine attachment site in a bead method in-mold foam molding method using a compression filling method, and in particular, carbonization of butane or the like as a foaming agent. It has been found that there are many fusion defects near the foamed particle filling port in the in-mold foam molded product molded by the compression filling method using the polypropylene resin foamed particles obtained using hydrogen.
そこで、発泡剤として、発泡剤として二酸化炭素を含む発泡剤を使用し、さらに、基材樹脂として重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）の比（Ｍｗ／Ｍｎ）が３．６以上であるポリプロピレン系樹脂を使用し、得られた発泡粒子をさらに発泡させた多段発泡粒子を用いると、充填機付近の融着不良の発生を防止できることを見出し、本発明をなすに至った。 Therefore, a foaming agent containing carbon dioxide is used as the foaming agent, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3.6 or more as the base resin. It was found that the use of a polypropylene resin and the multistage foamed particles obtained by further foaming the obtained foamed particles can prevent the occurrence of poor fusion in the vicinity of the filling machine.
すなわち本発明は次のポリプロピレン系樹脂型内発泡成形体の製造方法に関する。
（１） 次の工程を経て得られるポリプロピレン系樹脂多段発泡粒子を用いる、圧縮充填法によるポリプロピレン系樹脂型内発泡成形体の製造方法。
重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）の比（Ｍｗ／Ｍｎ）が３．６以上であるポリプロピレン系樹脂を基材樹脂とするポリプロピレン系樹脂粒子を耐圧容器内で分散媒に分散させ、発泡剤として二酸化炭素を含む発泡剤を添加した後、ポリプロピレン系樹脂粒子の軟化温度以上の温度に加熱し、ポリプロピレン系樹脂粒子内に二酸化炭素を含む発泡剤を含浸させたのち、耐圧容器の一端を開放してポリプロピレン系樹脂粒子を耐圧容器内よりも低圧の雰囲気中に放出することによりポリプロピレン系樹脂発泡粒子を製造する工程、
得られたポリプロピレン系樹脂発泡粒子をさらに発泡させ、ポリプロピレン系樹脂多段発泡粒子を製造する工程。
（２）ポリプロピレン系樹脂粒子の基材となるポリプロピレン系樹脂が、エチレンを共重合単量体成分として含むランダム共重合体であることを特徴とする（１）に記載のポリプロピレン系樹脂型内発泡成形体の製造方法。
That is, this invention relates to the manufacturing method of the following polypropylene-type resin in-mold foaming molding.
(1) A method for producing a polypropylene resin-in-mold foam-molded product by a compression filling method using polypropylene resin multistage expanded particles obtained through the following steps.
A polypropylene resin particle having a base resin of a polypropylene resin having a ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.6 or more is dispersed in a dispersion medium in a pressure vessel. After adding a foaming agent containing carbon dioxide as a foaming agent, heating to a temperature equal to or higher than the softening temperature of the polypropylene resin particles, impregnating the polypropylene resin particles with a foaming agent containing carbon dioxide, A step of producing polypropylene resin expanded particles by releasing one end and releasing the polypropylene resin particles in a low-pressure atmosphere than in the pressure vessel;
The step of further foaming the obtained polypropylene resin expanded particles to produce polypropylene resin multistage expanded particles.
(2) The polypropylene resin in-mold foam according to (1), wherein the polypropylene resin as a base material for the polypropylene resin particles is a random copolymer containing ethylene as a comonomer component. Manufacturing method of a molded object.
本発明のポリプロピレン系樹脂型内発泡成形体の製造方法によれば金型の充填機取り付け部位付近の融着不良が発生しない型内発泡成形体を得ることができる。 According to the method for producing a polypropylene resin in-mold foam molded body of the present invention, an in-mold foam molded body that does not cause poor fusion in the vicinity of a mold filling machine attachment site can be obtained.
本発明に用いるポリプロピレン系樹脂発泡粒子を構成するポリプロピレン系樹脂としては、単量体成分として、プロピレンを含んでいれば特に限定はなく、たとえば、プロピレンホモポリマー、α−オレフィン−プロピレンランダム共重合体、α−オレフィン−プロピレンブロック共重合体などが挙げられる。これらは、単独で用いてもよく、２種以上併用してもよい。特に、α−オレフィンがエチレンである、エチレンを共重合単量体成分として含有するポリプロピレン系樹脂が好ましい。好ましいエチレン含量は１重量％以上１０重量％以下、さらには１重量％以上７重量％以下、さらには２重量％以上７重量％以下、さらには３重量％以上７重量％以下、さらには３．５重量％以上６重量％以下、特には３．５重量％以上５重量％以下である。なお、ポリプロピレン系樹脂中共重合単量体成分としてのエチレンの含有量は13Ｃ−ＮＭＲを用いて測定することができる。 The polypropylene resin constituting the expanded polypropylene resin particles used in the present invention is not particularly limited as long as it contains propylene as a monomer component. For example, propylene homopolymer, α-olefin-propylene random copolymer , Α-olefin-propylene block copolymer, and the like. These may be used alone or in combination of two or more. Particularly preferred is a polypropylene resin containing ethylene as a comonomer component, wherein the α-olefin is ethylene. The ethylene content is preferably 1 to 10% by weight, more preferably 1 to 7% by weight, further 2 to 7% by weight, further 3 to 7% by weight, and 5% by weight or more and 6% by weight or less, particularly 3.5% by weight or more and 5% by weight or less. In addition, content of ethylene as a comonomer component in a polypropylene resin can be measured using 13 C-NMR.
本発明に用いるポリプロピレン系樹脂はエチレン以外の共重合単量体成分として含んでいてもよい。また、エチレンを共重合単量体成分として含有するポリプロピレン系樹脂がエチレン以外の単量体を共重合単量体成分として含んでいてもよい。エチレン以外の共重合単量体成分としては、１−ブテン、イソブテン、１−ペンテン、３−メチル−１−ブテン、１−ヘキセン、４−メチル−１−ペンテン、３，４−ジメチル−１−ブテン、１−ヘプテン、３−メチル−１−ヘキセン、１−オクテン、１−デセンなどの炭素数４〜１２のα−オレフィン；シクロペンテン、ノルボルネン、テトラシクロ［６，２，１１，８，１３，６］−４−ドデセンなどの環状オレフィン；５−メチレン−２−ノルボルネン、５−エチリデン−２−ノルボルネン、１，４−ヘキサジエン、メチル−１，４−ヘキサジエン、７−メチル−１，６−オクタジエンなどのジエン；塩化ビニル、塩化ビニリデン、アクリロニトリル、酢酸ビニル、アクリル酸、メタクリル酸、マレイン酸、アクリル酸エチル、アクリル酸ブチル、メタクリル酸メチル、無水マレイン酸、スチレン、メチルスチレン、ビニルトルエン、ジビニルベンゼンなどのビニル単量体などが挙げられ、これらを一種または二種以上使用することが出来る。 The polypropylene resin used in the present invention may be contained as a comonomer component other than ethylene. Moreover, the polypropylene resin containing ethylene as a comonomer component may contain a monomer other than ethylene as a comonomer component. As comonomer components other than ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1- Α-olefins having 4 to 12 carbon atoms such as butene, 1-heptene, 3-methyl-1-hexene, 1-octene, 1-decene; cyclopentene, norbornene, tetracyclo [6,2,11,8,13,6 ] Cyclic olefins such as 4-dodecene; 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene, etc. Diene: vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, acrylic Butyl, methyl methacrylate, maleic anhydride, styrene, methyl styrene, vinyl toluene, vinyl monomers such as divinylbenzene and the like, may be used these one or two or more.
本発明に用いるポリプロピレン系樹脂は、ランダム共重合体、ブロック共重合体のどちらでも用いることができる。エチレンを共重合単量体成分として含有するランダム共重合体を用いることが好ましく、特に汎用性の高い、エチレン−プロピレンランダム共重合体あるいはエチレン−プロピレン−ブテンランダム３元共重合体を用いることがより好ましい。共重合単量体成分としてのエチレン含量が１重量％以上７重量％以下、さらには、３重量％以上７重量％以下、さらには３．５重量％以上６重量％以下、特には３．５重量％以上５重量％以下であるエチレン−プロピレンランダム共重合体、あるいは、エチレン−プロピレン−ブテンランダム３元共重合体が好ましい。 As the polypropylene resin used in the present invention, either a random copolymer or a block copolymer can be used. It is preferable to use a random copolymer containing ethylene as a comonomer component, and it is particularly preferable to use a highly versatile ethylene-propylene random copolymer or ethylene-propylene-butene random terpolymer. More preferred. The ethylene content as the comonomer component is 1% by weight to 7% by weight, more preferably 3% by weight to 7% by weight, further 3.5% by weight to 6% by weight, particularly 3.5%. An ethylene-propylene random copolymer or an ethylene-propylene-butene random terpolymer having a weight percentage of 5% by weight or less is preferred.
また、ポリプロピレン系樹脂以外に、他の熱可塑性樹脂、例えば、低密度ポリエチレン、直鎖状低密度ポリエチレン、ポリスチレン、ポリブテン、アイオノマー等をポリプロピレン系樹脂の特性が失われない範囲で混合使用してポリプロピレン系樹脂粒子としても良い。 In addition to polypropylene resins, other thermoplastic resins such as low density polyethylene, linear low density polyethylene, polystyrene, polybutene, ionomer, etc. are mixed and used within a range that does not lose the properties of the polypropylene resin. System resin particles may be used.
本発明で使用するポリプロピレン系樹脂の重量平均分子量（以下、Ｍｗと表記する場合がある）と数平均分子量（以下、Ｍｎと表記する場合がある）の比（Ｍｗ／Ｍｎ）は３．６以上である。３．６未満であると型内発泡成形体における充填機取り付け部位付近の融着不良が発生しやすい。Ｍｗ／Ｍｎが４．０以上、或いは５．０以上であっても充填機取り付け部位付近の融着不良の発生はない。本発明で使用するポリプロピレン系樹脂のＭｗ／Ｍｎは３．６以上６．０以下が好ましい。 The ratio (Mw / Mn) of the weight average molecular weight (hereinafter sometimes referred to as Mw) and the number average molecular weight (hereinafter sometimes referred to as Mn) of the polypropylene resin used in the present invention is 3.6 or more. It is. If it is less than 3.6, poor fusion is likely to occur near the filling machine attachment site in the in-mold foam molded article. Even if Mw / Mn is 4.0 or more, or 5.0 or more, there is no occurrence of poor fusion in the vicinity of the filling machine attachment site. The Mw / Mn of the polypropylene resin used in the present invention is preferably 3.6 or more and 6.0 or less.
Ｍｎ及びＭｗは以下の条件において測定される。
測定機器 ：Ｗａｔｅｒｓ社製Ａｌｌｉａｎｃｅ ＧＰＣ ２０００型 ゲルパーミエーションクロマトグラフィー（ＧＰＣ）
カラム ：ＴＳＫｇｅｌ ＧＭＨ６−ＨＴ ２本、
ＴＳＫｇｅｌ ＧＭＨ６−ＨＴＬ ２本（それぞれ、内径７．５ｍｍ×長さ３００ｍｍ、東ソー社製）
移動相 ：ｏ−ジクロロベンゼン（０．０２５％ＢＨＴ含有）
カラム温度：１４０℃
流速 ：１．０ｍＬ／ｍｉｎ
試料濃度 ：０．１５％（Ｗ／Ｖ）−ｏ−ジクロロベンゼン
注入量 ：５００μＬ
分子量較正：ポリスチレン換算（標準ポリスチレンによる較正）
Mn and Mw are measured under the following conditions.
Measuring instrument: Alliance GPC 2000 type gel permeation chromatography (GPC) manufactured by Waters
Column: 2 TSKgel GMH6-HT,
Two TSKgel GMH6-HTL (each inner diameter 7.5mm x length 300mm, manufactured by Tosoh Corporation)
Mobile phase: o-dichlorobenzene (containing 0.025% BHT)
Column temperature: 140 ° C
Flow rate: 1.0 mL / min
Sample concentration: 0.15% (W / V) -o-dichlorobenzene injection amount: 500 μL
Molecular weight calibration: Polystyrene conversion (calibration with standard polystyrene)
本発明で使用するポリプロピレン系樹脂は、チーグラー触媒、メタロセン触媒、ポストメタロセン触媒等の触媒を用いて得ることができる。チーグラー触媒を使用するとＭｗ／Ｍｎが大きいポリプロピレン系樹脂が得られる傾向にある。また、これらの触媒を使用して得られたポリプロピレン系樹脂を有機過酸化物で減成処理すると分子量やメルトインデックス等の特性を調整することができる。 The polypropylene resin used in the present invention can be obtained using a catalyst such as a Ziegler catalyst, a metallocene catalyst, or a post metallocene catalyst. When a Ziegler catalyst is used, a polypropylene resin having a large Mw / Mn tends to be obtained. Moreover, when a polypropylene resin obtained using these catalysts is subjected to a degeneration treatment with an organic peroxide, characteristics such as molecular weight and melt index can be adjusted.
使用しうる有機過酸化物としては、１，１−ビス（ｔ−ブチルパーオキシ）３，３，５−トリメチルシクロヘキサン、ｔ−ブチルパーオキシラウレート、２，５−ジメチル２，５−ジ（ベンゾイルパーオキシ）ヘキサン、ｔ−ブチルパーオキシベンゾエート、ジクミルパーオキサイド、１，３−ビス（ｔ−ブチルパーオキシイソプロピル）ベンゼン、ｔ−ブチルパーオキシイソプロピルモノカーボネート等が挙げられる。 Examples of the organic peroxide that can be used include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butylperoxylaurate, 2,5-dimethyl2,5-di ( Benzoylperoxy) hexane, t-butylperoxybenzoate, dicumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, t-butylperoxyisopropyl monocarbonate and the like.
有機過酸化物の使用量は、ポリプロピレン系樹脂１００重量部に対して、０．００１重量部以上０．１重量部以下であることが好ましい。ポリプロピレン樹脂を減成処理するには、例えば、有機過酸化物を添加したポリプロピレン系樹脂を押出機内で加熱溶融により行うことができる。 The amount of the organic peroxide used is preferably 0.001 part by weight or more and 0.1 part by weight or less with respect to 100 parts by weight of the polypropylene resin. In order to degrade the polypropylene resin, for example, a polypropylene resin to which an organic peroxide is added can be heated and melted in an extruder.
本発明で使用するポリプロピレン系樹脂は無架橋の状態が好ましいが、有機過酸化物や放射線等で処理することにより架橋反応を行っても良い。また、２以上のポリプロピレン系樹脂を混合しても良い。 The polypropylene resin used in the present invention is preferably in a non-crosslinked state, but may be subjected to a crosslinking reaction by treatment with an organic peroxide or radiation. Two or more polypropylene resins may be mixed.
本発明で用いるポリプロピレン系樹脂粒子の融点は、１３０℃以上１６５℃以下であることが好ましく、更には１３５℃以上１５５℃以下のものが好ましい。融点が１３０℃未満の場合、耐熱性、機械的強度が十分でない傾向がある。また、融点が１６５℃を超える場合、型内発泡成形時の融着を確保することが難しくなる傾向がある。ここで、前記融点とは、示差走査熱量計によってポリプロピレン系樹脂１〜１０ｍｇを４０℃から２２０℃まで１０℃／分の速度で昇温し、その後４０℃まで１０℃／分の速度で冷却し、再度２２０℃まで１０℃／分の速度で昇温した時に得られるＤＳＣ曲線における吸熱ピークのピーク温度をいう。 The melting point of the polypropylene resin particles used in the present invention is preferably 130 ° C. or higher and 165 ° C. or lower, and more preferably 135 ° C. or higher and 155 ° C. or lower. When the melting point is less than 130 ° C., heat resistance and mechanical strength tend to be insufficient. Moreover, when melting | fusing point exceeds 165 degreeC, there exists a tendency for it to become difficult to ensure the melt | fusion at the time of in-mold foam molding. Here, the melting point is a temperature of 10 to 10 ° C./min from 40 ° C. to 220 ° C., and then cooled to 40 ° C. at a rate of 10 ° C./min with a differential scanning calorimeter. The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is increased again to 220 ° C. at a rate of 10 ° C./min.
本発明で用いることが出来るポリプロピレン系樹脂粒子のメルトフローレート（以下、ＭＦＲ値）は、０．５ｇ／１０分以上３０ｇ／１０分以下であることが好ましく、更には２ｇ／１０分以上２０ｇ／１０分以下のものが好ましい。ＭＦＲ値が０．５ｇ／１０分未満の場合、高発泡倍率のポリプロピレン系樹脂発泡粒子が得られにくい場合があり、３０ｇ／１０分を超える場合、ポリプロピレン系樹脂発泡粒子の気泡が破泡し易く、ポリプロピレン系樹脂発泡粒子の連泡率が高くなる傾向にある。なお、ＭＦＲ値はＪＩＳ Ｋ７２１０に準拠し、温度２３０℃、荷重２．１６ｋｇで測定する。 The melt flow rate (hereinafter referred to as MFR value) of the polypropylene resin particles that can be used in the present invention is preferably 0.5 g / 10 min or more and 30 g / 10 min or less, and more preferably 2 g / 10 min or more and 20 g / min. The thing of 10 minutes or less is preferable. When the MFR value is less than 0.5 g / 10 minutes, it may be difficult to obtain polypropylene-based resin expanded particles having a high expansion ratio. When the MFR value exceeds 30 g / 10 minutes, the bubbles of the polypropylene-based resin expanded particles are likely to break. The open cell ratio of the polypropylene resin expanded particles tends to increase. The MFR value is measured according to JIS K7210 at a temperature of 230 ° C. and a load of 2.16 kg.
ポリプロピレン系樹脂は通常、発泡粒子を製造するために、押出機、ニーダー、バンバリーミキサー、ロール等を用いて溶融し、円柱状、楕円状、球状、立方体状、直方体状等の樹脂粒子形状に加工する。必要に応じて添加される他の樹脂や添加剤もこの工程で添加することができる。ポリプロピレン系樹脂粒子の大きさは、一粒の重量が０．１ｍｇ以上３０ｍｇ以下であることが好ましく、０．３ｍｇ以上１０ｍｇ以下がより好ましい。ポリプロピレン系樹脂粒子の一粒の重量は、ポリプロピレン系樹脂粒子をランダムに選んだ１００粒から得られる平均樹脂粒子重量であり、以下、ｍｇ／粒で表示する。 Polypropylene resins are usually melted using extruders, kneaders, Banbury mixers, rolls, etc. to produce expanded particles, and processed into resin particle shapes such as cylindrical, elliptical, spherical, cubic, and rectangular parallelepiped shapes. To do. Other resins and additives that are added as necessary can also be added in this step. As for the size of the polypropylene resin particles, the weight of one particle is preferably 0.1 mg or more and 30 mg or less, and more preferably 0.3 mg or more and 10 mg or less. The weight of one polypropylene resin particle is the average resin particle weight obtained from 100 randomly selected polypropylene resin particles, and is hereinafter expressed in mg / grain.
ポリプロピレン系樹脂粒子の製造の際、必要により発泡核剤、親水性物質、着色剤、帯電防止剤、酸化防止剤、リン系加工安定剤、ラクトン系加工安定剤、金属不活性剤、ベンゾトリアゾール系紫外線吸収剤、ベンゾエート系光安定剤、ヒンダードアミン系光安定剤、難燃剤、難燃助剤、酸中和剤、結晶核剤、アミド系添加剤等の添加剤を、ポリプロピレン系樹脂の特性を損なわない範囲内で添加することができる。樹脂に発泡核剤、親水性物質或いは他の添加剤を加える場合、上記ポリプロピレン系樹脂粒子の製造前にブレンダー等を用いポリプロピレン系樹脂と混合することが好ましい。また、溶融したポリプロピレン系樹脂中に添加剤を添加してもよい。 When producing polypropylene resin particles, if necessary, foam nucleating agent, hydrophilic substance, colorant, antistatic agent, antioxidant, phosphorus processing stabilizer, lactone processing stabilizer, metal deactivator, benzotriazole Additives such as ultraviolet absorbers, benzoate light stabilizers, hindered amine light stabilizers, flame retardants, flame retardant aids, acid neutralizers, crystal nucleating agents, amide additives, and other properties of polypropylene resins are impaired. It can be added within the range. When adding a foam nucleating agent, a hydrophilic substance, or other additives to the resin, it is preferable to mix with the polypropylene resin using a blender or the like before the production of the polypropylene resin particles. Moreover, you may add an additive in the molten polypropylene resin.
発泡核剤は、セル造核剤ともいい、発泡の時に気泡核の形成を促す物質である。発泡核剤の例としては、タルク、炭酸カルシウム、シリカ、カオリン、硫酸バリウム、水酸化カルシウム、水酸化アルミニウム、酸化アルミニウム、酸化チタン等の無機物質が挙げられる。これらの中でも、タルク、炭酸カルシウムがポリプロピレン系樹脂中への分散性が良好で均一な気泡を有する発泡粒子を得易くなるため好ましい。発泡核剤は、単独で用いてもよく、２種以上を併用しても良い。 The foam nucleating agent is also called a cell nucleating agent, and is a substance that promotes the formation of bubble nuclei during foaming. Examples of the foam nucleating agent include inorganic substances such as talc, calcium carbonate, silica, kaolin, barium sulfate, calcium hydroxide, aluminum hydroxide, aluminum oxide, and titanium oxide. Among these, talc and calcium carbonate are preferable because they are easy to obtain foamed particles having good dispersibility in a polypropylene resin and having uniform cells. A foam nucleating agent may be used independently and may use 2 or more types together.
発泡核剤の添加量は使用する発泡核剤によって異なり、一概には決めることが出来ないが、ポリプロピレン系樹脂１００重量部に対して、０．００５重量部以上２重量部以下であることが好ましく、０．０１重量部以上１重量部以下であることがより好ましい。発泡核剤の添加量が０．００５重量部より少ない場合は、ポリプロピレン系樹脂発泡粒子の発泡倍率を大きくすることができなかったり、気泡の均一性が低下してしまう場合がある。発泡核剤の添加量が２重量部より多い場合は、ポリプロピレン系樹脂発泡粒子の平均気泡径が小さくなり過ぎ、型内発泡成形性が不良となる傾向にある。 The addition amount of the foam nucleating agent varies depending on the foam nucleating agent to be used and cannot be generally determined, but is preferably 0.005 parts by weight or more and 2 parts by weight or less with respect to 100 parts by weight of the polypropylene resin. More preferably, the content is 0.01 parts by weight or more and 1 part by weight or less. When the addition amount of the foam nucleating agent is less than 0.005 parts by weight, the expansion ratio of the polypropylene resin foamed particles may not be increased or the uniformity of the bubbles may be deteriorated. When the amount of the foam nucleating agent added is more than 2 parts by weight, the average cell diameter of the polypropylene resin foamed particles tends to be too small and the in-mold foam moldability tends to be poor.
また、たとえば発泡核剤としてタルクを使用する場合、添加量はポリプロピレン系樹脂１００重量部に対して、０．００５重量部以上１重量部以下であることが好ましく、さらに好ましくは０．０１重量部以上０．５重量部以下、より好ましくは０．０２重量部以上０．２重量部以下である。 For example, when talc is used as the foam nucleating agent, the addition amount is preferably 0.005 parts by weight or more and 1 part by weight or less, more preferably 0.01 parts by weight, with respect to 100 parts by weight of the polypropylene resin. The amount is 0.5 part by weight or less and more preferably 0.02 part by weight or more and 0.2 part by weight or less.
ポリプロピレン系樹脂には、親水性物質を添加してもよい。親水性物質を添加すると発泡粒子の発泡倍率を向上させることができる。親水性物質として分子量６００以下の化合物が好ましい。親水性物質が無機塩などの場合は分子量に代えて式量を使用する。親水性物質の分子量が６００を越えると、分子量が６００以下の親水性物質を使用する場合に比較し、同じ発泡倍率の発泡粒子を得るためには多量の親水性物質が必要になり、さらに、得られる型内発泡成形体の低収縮性、表面性あるいは融着性が低下する傾向がある。親水性物質が重合体の場合、その平均分子量は、たとえば、サーモフィッシャーサイエンティフィック製ＬＣＱアドバンテージなどの液体クロマトグラフ質量分析装置を使用し測定できる。 A hydrophilic substance may be added to the polypropylene resin. When a hydrophilic substance is added, the expansion ratio of the expanded particles can be improved. A compound having a molecular weight of 600 or less is preferable as the hydrophilic substance. When the hydrophilic substance is an inorganic salt, the formula weight is used instead of the molecular weight. When the molecular weight of the hydrophilic substance exceeds 600, a larger amount of hydrophilic substance is required to obtain expanded particles having the same expansion ratio as compared with the case where a hydrophilic substance having a molecular weight of 600 or less is used. There is a tendency that the low shrinkage property, surface property, or fusing property of the obtained in-mold foam molded product is lowered. When the hydrophilic substance is a polymer, its average molecular weight can be measured using a liquid chromatograph mass spectrometer such as LCQ Advantage manufactured by Thermo Fisher Scientific.
本発明で用いる親水性物質は、発泡直後の発泡粒子が一定量以上の水を含有するようにできる物質であればよく、必ずしも室温で親水性でなくともよい。親水性物質の具体例としては、塩化ナトリウム、塩化カルシウム、塩化マグネシウム、硼砂、硼酸亜鉛等の無機物、グリセリン、メラミン、イソシアヌル酸、メラミン・イソシアヌル酸縮合物等の有機物、ポリエチレングリコール、ポリエチレンオキシド等のポリエーテル、ポリエーテルのポリプロピレン等への付加物やこれらのアロイ、エチレン（メタ）アクリル酸共重合体のアルカリ金属塩、ブタジエン（メタ）アクリル酸共重合体のアルカリ金属塩、カルボキシル化ニトリルゴムのアルカリ金属塩、イソブチレン−無水マレイン酸共重合体のアルカリ金属塩及びポリ（メタ）アクリル酸のアルカリ金属塩等の親水性重合体が挙げられる。国際公開ＷＯ９７／３８０４８号公報、特開平１０−３０６１７９号公報、特開平１１−９２５９９号公報、特開２００４−６７７６８号公報には親水性物質が詳細に記載されている。これら、無機物、有機物や親水性重合体を２種以上併用してもよい。これらの親水性物質のなかでは、ポリエチレングリコール等の有機重合体、グリセリン、メラミン等の有機物あるいは硼酸亜鉛が好ましく、有機重合体や有機物が特に好ましい。 The hydrophilic substance used in the present invention is not limited as long as it is a substance that allows foamed particles immediately after foaming to contain a certain amount or more of water, and is not necessarily hydrophilic at room temperature. Specific examples of the hydrophilic substance include inorganic substances such as sodium chloride, calcium chloride, magnesium chloride, borax and zinc borate, organic substances such as glycerin, melamine, isocyanuric acid, melamine / isocyanuric acid condensate, polyethylene glycol, polyethylene oxide and the like. Polyethers, addition products of polyethers to polypropylene, and alloys thereof, alkali metal salts of ethylene (meth) acrylic acid copolymers, alkali metal salts of butadiene (meth) acrylic acid copolymers, carboxylated nitrile rubber Examples thereof include hydrophilic polymers such as alkali metal salts, alkali metal salts of isobutylene-maleic anhydride copolymer and alkali metal salts of poly (meth) acrylic acid. International publications WO 97/38048, JP-A-10-306179, JP-A-11-92599, and JP-A-2004-67768 describe hydrophilic substances in detail. Two or more of these inorganic substances, organic substances and hydrophilic polymers may be used in combination. Among these hydrophilic substances, organic polymers such as polyethylene glycol, organic substances such as glycerin and melamine, or zinc borate are preferable, and organic polymers and organic substances are particularly preferable.
親水性物質の添加量は、ポリプロピレン系樹脂１００重量部に対して、０．００５重量部以上２重量部以下であることが好ましく、より好ましくは０．００５重量部以上１重量部以下、更に好ましくは０．０１重量部以上０．５重量部以下である。ここで親水性物質の添加量とは、吸水していない状態での親水性物質の重量を指す。親水性物質の添加量が０．００５重量部より少ないと、ポリプロピレン系樹脂発泡粒子の発泡倍率を向上させることができなかったり、気泡の均一化効果が低減する傾向がある。添加量が２重量部を超えると、ポリプロピレン系樹脂発泡粒子の収縮が生じ易くなったり、ポリプロピレン系樹脂中への親水性物質の分散が不十分となる傾向がある。なお、親水性物質が親水性重合体の場合、１００重量部に対して０．１重量部以上０．５重量部以下使用することが好ましい。 The addition amount of the hydrophilic substance is preferably 0.005 part by weight or more and 2 parts by weight or less, more preferably 0.005 part by weight or more and 1 part by weight or less, further preferably 100 parts by weight of polypropylene resin. Is 0.01 parts by weight or more and 0.5 parts by weight or less. Here, the addition amount of the hydrophilic substance refers to the weight of the hydrophilic substance in a state where water is not absorbed. When the addition amount of the hydrophilic substance is less than 0.005 parts by weight, the expansion ratio of the polypropylene resin expanded particles cannot be improved or the effect of uniforming the bubbles tends to be reduced. When the addition amount exceeds 2 parts by weight, shrinkage of the expanded polypropylene resin particles tends to occur, or the hydrophilic substance tends to be insufficiently dispersed in the polypropylene resin. In addition, when a hydrophilic substance is a hydrophilic polymer, it is preferable to use 0.1 to 0.5 weight part with respect to 100 weight part.
前記ポリプロピレン系樹脂粒子から除圧発泡法と呼ばれる方法を用いてポリプロピレン系樹脂発泡粒子を得る。具体的には、ポリプロピレン系樹脂粒子を耐圧容器内において分散媒に分散させ、発泡剤として二酸化炭素を含む発泡剤を添加した後、ポリプロピレン系樹脂粒子の軟化温度以上の温度に加熱し、ポリプロピレン系樹脂粒子内に二酸化炭素を含む発泡剤を含浸させたのち、耐圧容器の一端を開放してポリプロピレン系樹脂粒子を耐圧容器内よりも低圧の雰囲気中に放出することにより、ポリプロピレン系樹脂発泡粒子を製造する。除圧発泡法で得られた発泡粒子を一段発泡粒子と呼ぶ場合がある。ポリプロピレン系樹脂粒子の軟化温度はＪＩＳ Ｋ ２２０７に従って測定できる。通常、軟化温度は融点よりも低い。 Polypropylene resin foam particles are obtained from the polypropylene resin particles using a method called decompression foaming. Specifically, the polypropylene resin particles are dispersed in a dispersion medium in a pressure-resistant container, a foaming agent containing carbon dioxide is added as a foaming agent, and then heated to a temperature equal to or higher than the softening temperature of the polypropylene resin particles. After impregnating the foaming agent containing carbon dioxide into the resin particles, the polypropylene resin foam particles are released by opening one end of the pressure vessel and releasing the polypropylene resin particles in a lower pressure atmosphere than the pressure vessel. To manufacture. The expanded particles obtained by the pressure-reducing foaming method are sometimes referred to as single-stage expanded particles. The softening temperature of the polypropylene resin particles can be measured according to JIS K 2207. Usually, the softening temperature is lower than the melting point.
本発明においては、二酸化炭素を含む発泡剤を使用する。ブタン等の飽和炭化水素類を使用すると、得られる型内発泡成形体における充填機取り付け部位付近の融着不良が発生しやすい。二酸化炭素を含む発泡剤とは、発泡剤中、二酸化炭素の量が、好ましくは７０％以上であることを言う。 In the present invention, a blowing agent containing carbon dioxide is used. When saturated hydrocarbons such as butane are used, poor fusion is likely to occur in the vicinity of the filling machine attachment site in the in-mold foam molded product obtained. The blowing agent containing carbon dioxide means that the amount of carbon dioxide in the blowing agent is preferably 70% or more.
二酸化炭素を発泡剤として使用していれば、他の物理発泡剤を併用してもよい。他の物理発泡剤としては、プロパン、ブタン、ペンタン等の飽和炭化水素類、ジメチルエーテル等のエーテル類、メタノール、エタノール等のアルコール類、空気、窒素等の無機ガス、水等が挙げられる。中でも特に環境負荷が小さく、燃焼危険性も無いことから、水を併用することが望ましい。ポリプロピレン系樹脂粒子が親水性物質を含有していると、分散剤に水を含んでいる場合、分散媒中の水がポリプロピレン系樹脂粒子内に含有され、水が発泡剤として作用しやすくなる。二酸化炭素と水を併用することで、発泡力を大きくし易いことから、高発泡倍率を得る際においても、発泡核剤の添加量を少なくすることができ、結果として平均気泡径が大きい発泡粒子が得られ、二次発泡性も良好なものとなる傾向がある。 If carbon dioxide is used as a foaming agent, other physical foaming agents may be used in combination. Examples of other physical foaming agents include saturated hydrocarbons such as propane, butane, and pentane, ethers such as dimethyl ether, alcohols such as methanol and ethanol, inorganic gases such as air and nitrogen, water, and the like. Among them, it is desirable to use water in combination because it has a particularly low environmental load and no risk of combustion. When the polypropylene resin particles contain a hydrophilic substance, when the dispersant contains water, the water in the dispersion medium is contained in the polypropylene resin particles, and water easily acts as a foaming agent. The combined use of carbon dioxide and water makes it easy to increase the foaming power, so even when obtaining a high foaming ratio, the amount of foam nucleating agent added can be reduced, resulting in expanded particles having a large average cell diameter. And secondary foamability tends to be good.
発泡剤として水が作用しているかどうかは、二酸化炭素にかえて窒素を使用して、発泡温度や発泡圧力などの条件は二酸化炭素を使用した場合と同一になるようにして発泡粒子を製造し、発泡粒子内に含有されている水分量を測定することにより判断することができる。発泡粒子に含有される水分が発泡剤として作用する。発泡粒子内に含有されている水分量は、発泡直後の発泡粒子の重量とこれを乾燥し水分を揮発させた発泡粒子の重量との差から計算できる。また他の方法として、発泡直後の発泡粒子をポリマー用水分計、あるいはカールフィッシャー水分計などで測定することも可能である。 Whether or not water is acting as a blowing agent, nitrogen is used instead of carbon dioxide, and foamed particles are produced so that conditions such as foaming temperature and pressure are the same as when carbon dioxide is used. This can be determined by measuring the amount of water contained in the expanded particles. The moisture contained in the expanded particles acts as a foaming agent. The amount of water contained in the foamed particles can be calculated from the difference between the weight of the foamed particles immediately after foaming and the weight of the foamed particles obtained by drying and evaporating the water. As another method, it is also possible to measure the expanded particles immediately after expansion with a polymer moisture meter or a Karl Fischer moisture meter.
本発明においては、除圧発泡法によって得られたポリプロピレン系樹脂発泡粒子（一段発泡粒子）をさらに発泡させ、ポリプロピレン系樹脂多段発泡粒子を製造する。発泡方法としては、一段発泡粒子を耐圧容器内にて空気等の無機ガスにて加圧し、内圧を付与したのち、加熱することでさらに発泡させる方法が好ましい。さらに発泡させる工程を複数回行ってもよい。このような工程を「多段発泡」と称する。多段発泡の中でも、さらに発泡させる工程を一回だけ行う場合には、「二段発泡」と称す場合がある。 In the present invention, polypropylene-based resin expanded particles (single-stage expanded particles) obtained by the decompression foaming method are further expanded to produce polypropylene-based resin multistage expanded particles. As the foaming method, a method is preferred in which the single-stage foamed particles are pressurized with an inorganic gas such as air in a pressure-resistant container, and the internal pressure is applied, followed by heating to further foam. Further, the foaming step may be performed a plurality of times. Such a process is referred to as “multi-stage foaming”. Among the multistage foaming, when the foaming process is performed only once, it may be referred to as “two-stage foaming”.
また、多段発泡によって得られる発泡粒子を多段発泡粒子と称するが、一段発泡粒子を二段発泡によって得られる発泡粒子を二段発泡粒子と呼ぶ場合がある。 In addition, foamed particles obtained by multistage foaming are referred to as multistage foamed particles. However, foamed particles obtained by two-stage foaming of single-stage foamed particles may be referred to as two-stage foamed particles.
最終的に得られる、ポリプロピレン系樹脂多段発泡粒子の発泡倍率は２０倍以上、好ましくは３０倍以上、さらに好ましくは３２倍以上である。ポリプロピレン系樹脂多段発泡粒子の発泡倍率は６０倍以下が好ましい。発泡倍率が２０倍未満の場合は、軽量化のメリットが得られず、また得られる型内発泡成形体の柔軟性、緩衝特性などが不充分となる傾向があり、６０倍を越える場合は得られる型内発泡成形体の寸法精度、機械的強度、耐熱性などが不充分となる傾向がある。ポリプロピレン系樹脂発泡粒子の発泡倍率の測定法は後記する。 The expansion ratio of the finally obtained polypropylene resin multistage expanded particles is 20 times or more, preferably 30 times or more, and more preferably 32 times or more. The expansion ratio of the polypropylene resin multistage expanded particles is preferably 60 times or less. If the expansion ratio is less than 20 times, the advantage of weight reduction cannot be obtained, and the flexibility and buffering properties of the obtained in-mold foam molded product tend to be insufficient. There is a tendency that the dimensional accuracy, mechanical strength, heat resistance and the like of the in-mold foam-molded product are insufficient. A method for measuring the expansion ratio of the polypropylene resin expanded particles will be described later.
本発明で用いるポリプロピレン系樹脂発泡粒子、或いは、ポリプロピレン系樹脂多段発泡粒子の平均気泡径は５０μｍ以上８００μｍ以下であることが好ましく、より好ましくは１００μｍ以上６００μｍ以下、さらに好ましくは２００μｍ以上５００μｍ以下である。平均気泡径が５０μｍ未満の場合、得られる型内発泡成形体の形状が歪む、表面にしわが発生するなどの問題が生じる場合があり、８００μｍを越える場合、得られる型内発泡成形体の緩衝特性が低下する場合がある。平均気泡径は、ポリプロピレン系樹脂発泡粒子の切断面について、表層部を除く部分について、ＡＳＴＭ Ｄ３５７６に従い測定する。 The average cell diameter of the polypropylene resin expanded particles or polypropylene resin multistage expanded particles used in the present invention is preferably 50 μm or more and 800 μm or less, more preferably 100 μm or more and 600 μm or less, and further preferably 200 μm or more and 500 μm or less. . When the average cell diameter is less than 50 μm, there are cases where the shape of the obtained in-mold foam molded product is distorted and the surface is wrinkled. When the average cell diameter exceeds 800 μm, the buffer properties of the in-mold foam molded product to be obtained May decrease. The average cell diameter is measured according to ASTM D3576 with respect to the cut surface of the polypropylene-based resin expanded particles, except for the surface layer portion.
本発明で用いるポリプロピレン系樹脂発泡粒子、或いは、ポリプロピレン系樹脂多段発泡粒子の連泡率は０〜１２％であることが好ましく、より好ましくは０〜８％、さらに好ましくは０〜５％である。連泡率が１２％を超えると、型内発泡成形時に蒸気加熱による発泡性に劣り、得られた型内発泡成形体が収縮してしまう傾向にある。 The open cell ratio of the polypropylene resin expanded particles or polypropylene resin multistage expanded particles used in the present invention is preferably 0 to 12%, more preferably 0 to 8%, still more preferably 0 to 5%. . When the open cell ratio exceeds 12%, the foamability by steam heating is inferior at the time of in-mold foam molding, and the obtained in-mold foam molded product tends to shrink.
本発明で用いるポリプロピレン系樹脂多段発泡粒子は、示差走査熱量測定によって得られるＤＳＣ曲線において、２つ以上の融点を示す結晶構造を有することが好ましい。２つ以上の融点を示す結晶構造を有するポリプロピレン系樹脂多段発泡粒子の場合、型内発泡成形性が良く、機械的強度や耐熱性の良好な型内発泡成形体が得られる傾向にある。ここで、ポリプロピレン系樹脂多段発泡粒子の示差走査熱量測定によって得られるＤＳＣ曲線とは、ポリプロピレン系樹脂発泡粒子１〜１０ｍｇを示差走査熱量計によって１０℃／分の昇温速度で４０℃から２２０℃まで昇温したときに得られるＤＳＣ曲線のことである。このＤＳＣ曲線において、現れる融解ピークの示す温度が融点である。 The polypropylene resin multistage expanded particles used in the present invention preferably have a crystal structure showing two or more melting points in a DSC curve obtained by differential scanning calorimetry. In the case of a polypropylene resin multistage expanded particle having a crystal structure having two or more melting points, there is a tendency to obtain an in-mold foam molded article having good in-mold foam moldability and good mechanical strength and heat resistance. Here, the DSC curve obtained by differential scanning calorimetry of the polypropylene resin multistage expanded particles means that 1 to 10 mg of polypropylene resin expanded particles is 40 ° C. to 220 ° C. at a temperature increase rate of 10 ° C./min by a differential scanning calorimeter. DSC curve obtained when the temperature is raised to. In this DSC curve, the temperature indicated by the melting peak that appears is the melting point.
前記のごとく２つ以上の融点を示す結晶構造を有するポリプロピレン系樹脂多段発泡粒子は、除圧発泡時の耐圧容器内温度を適切に設定することにより容易に得られる。基材となるポリプロピレン系樹脂の軟化温度以上、好ましくは融点＋３℃以上、融解終了温度未満、好ましくは融解終了温度−２℃以下の温度から選定される。ここで、前記融解終了温度とは、示差走査熱量計によってポリオレフィン系樹脂粒子１〜１０ｍｇを４０℃から２２０℃まで１０℃／分の速度で昇温し、その後４０℃まで１０℃／分の速度で冷却し、再度２２０℃まで１０℃／分の速度で昇温した時に得られる融解ピーク曲線が高温側でベースラインの位置に戻ったときの温度である。 As described above, the polypropylene resin multistage expanded particles having a crystal structure exhibiting two or more melting points can be easily obtained by appropriately setting the temperature in the pressure resistant container during decompression foaming. The temperature is selected from the temperature of the softening temperature or higher of the polypropylene resin as the base material, preferably the melting point + 3 ° C. or higher and lower than the melting end temperature, preferably the melting end temperature −2 ° C. or lower. Here, the melting end temperature is 1 to 10 mg of polyolefin resin particles heated at a rate of 10 ° C./min from 40 ° C. to 220 ° C. with a differential scanning calorimeter, and then at a rate of 10 ° C./min to 40 ° C. This is the temperature at which the melting peak curve obtained when the temperature is cooled again at 220 ° C. at a rate of 10 ° C./min returns to the baseline position on the high temperature side.
以上のようにして得られるポリプロピレン系樹脂多段発泡粒子は、圧縮充填法を用いて型内発泡成形されポリプロピレン系樹脂型内発泡成形体が製造される。 The polypropylene resin multistage expanded particles obtained as described above are subjected to in-mold foam molding using a compression filling method to produce a polypropylene resin in-mold foam molded article.
すなわち、得られたポリプロピレン系樹脂多段発泡粒子を圧縮して、圧縮されたポリプロピレン系樹脂多段発泡粒子を製造し、圧縮されたポリプロピレン系樹脂多段発泡粒子を型内発泡成形機金型の型窩内に充填、金型内の圧力を解放し充填されている圧縮されたポリプロピレン系樹脂多段発泡粒子を膨張させ、膨張されたポリプロピレン系樹脂多段発泡粒子を加熱し、発泡粒子間を融着させ、ポリプロピレン系樹脂型内発泡成形体とする。 That is, the obtained polypropylene resin multi-stage expanded particles are compressed to produce compressed polypropylene resin multi-stage expanded particles, and the compressed polypropylene resin multi-stage expanded particles are injected into the mold cavity of the in-mold foam molding machine mold. The expanded polypropylene resin multistage expanded particles that are filled by releasing the pressure inside the mold are expanded, the expanded polypropylene resin multistage expanded particles are heated, and the expanded particles are fused to form polypropylene. It is set as an in-mold resin mold.
ポリプロピレン系樹脂多段発泡粒子は、該発泡粒子を圧縮タンク中で加圧ガスを用いて、好ましくは充填前の発泡粒子の嵩体積の２０〜８０％に圧縮し、圧縮された発泡粒子を閉鎖しうるが密閉しない金型の型窩内に充填し、金型内の圧力を開放した後、蒸気などによりポリプロピレン系樹脂多段発泡粒子を加熱、発泡粒子間を融着させて型内発泡成形体を製造する。 The polypropylene resin multistage expanded particles are compressed in a compression tank using a pressurized gas, preferably to 20 to 80% of the bulk volume of the expanded expanded particles, and the compressed expanded particles are closed. After filling the mold cavity of the mold that can be sealed but releasing the pressure in the mold, the polypropylene resin multistage expanded particles are heated with steam, etc., and the expanded particles are fused to form an in-mold expanded molded body. To manufacture.
次に圧縮充填法によるビーズ法型内発泡成形法の一例を、図面を参照しながら説明する。第１図において１は発泡粒子圧縮タンク、２は発泡粒子供給口、３は加圧ガス入口、４は金型、５は固定型、６は移動型、７は型窩、８は通気口、９はスチームチャンバー、１０は蒸気ライン、１１は蒸気弁、１２はドレン弁、１３は金型ガス圧力調整バルブ、１４は排気弁、１５は排気口、１６は充填機、１７は発泡粒子充填用加圧ガス入口、１８は発泡粒子充填口、１９はピストンプラグ、２０は均圧ラインである。 Next, an example of the bead method in-mold foam molding method by the compression filling method will be described with reference to the drawings. In FIG. 1, 1 is a foamed particle compression tank, 2 is a foamed particle supply port, 3 is a pressurized gas inlet, 4 is a mold, 5 is a fixed type, 6 is a movable type, 7 is a mold cavity, 8 is a vent, 9 is a steam chamber, 10 is a steam line, 11 is a steam valve, 12 is a drain valve, 13 is a mold gas pressure regulating valve, 14 is an exhaust valve, 15 is an exhaust port, 16 is a filling machine, and 17 is for filling expanded particles A pressurized gas inlet, 18 is a foamed particle filling port, 19 is a piston plug, and 20 is a pressure equalizing line.
第１図に示される装置においては、ポリプロピレン系樹脂多段発泡粒子は発泡粒子供給口２から発泡粒子圧縮タンク１に供給され、加圧ガスが加圧ガス入口３から供給される。このとき、均圧ライン２０によって閉鎖しうるが密閉できない金型内にも加圧ガスが供給される。
In the apparatus shown in FIG. 1, the polypropylene resin multistage expanded particles are supplied from the expanded
上記圧縮に用いる加圧ガスとしては、経済性、生産性、安全性、環境適合性等の点から、二酸化炭素、窒素、空気又はこれらを主体（通常、５０容量％以上が好ましく、７０容量％以上がより好ましい）とし、アルゴン、ヘリウム、キセノン等の不活性ガスや水蒸気、酸素、水素、オゾン等を更に少量（５０容量％以下が好ましく、３０容量％以下がより好ましい）含む無機ガス等を使用することが好ましく、圧縮設備の設備費の点から空気がより好ましい。 The pressurized gas used for the compression is mainly carbon dioxide, nitrogen, air, or these (usually preferably 50% by volume or more, preferably 70% by volume) from the viewpoints of economy, productivity, safety, environmental compatibility, and the like. And more preferably, an inert gas such as argon, helium, xenon, or an inorganic gas containing a smaller amount of water vapor, oxygen, hydrogen, ozone, etc. (preferably 50% by volume or less, more preferably 30% by volume or less). It is preferable to use it, and air is more preferable from the viewpoint of the equipment cost of the compression equipment.
発泡粒子圧縮タンク１内および金型４内の圧力は金型ガス圧力調整バルブ１３によって調整され、所定の圧力に昇圧される。このとき排気弁１４は閉じている。圧縮時の圧力は、通常、下限が好ましくは０．０４ＭＰａ（Ｇ）であり、より好ましくは０．０５ＭＰａ（Ｇ）であり、上限が好ましくは０．４０ＭＰａ（Ｇ）であり、より好ましくは０．３５ＭＰａ（Ｇ）である。発泡粒子圧縮タンク１の耐圧は、高い方がそれだけ発泡粒子に圧縮ガス圧を与えられるため圧縮充填成形が適用可能な嵩密度範囲が拡ってよいが、耐圧能力が高いと設備投資費が大きくなるため、通常用いられている耐圧０．４ＭＰａ（Ｇ）付近が好ましい。
The pressure in the foamed particle compression tank 1 and the mold 4 is adjusted by a mold gas
ついで、圧縮されたポリプロピレン系樹脂多段発泡粒子は、固定型５と移動型６とのあいだの型窩７に充填機１６によって充填される。なお、充填は通常のポリプロピレン系樹脂発泡粒子の型内発泡成形で行なわれているのと同様であり、発泡粒子充填用加圧ガス入口１７から加圧ガスが供給されている。このとき金型ガス圧力調整バルブ１３は所定の金型ガス圧力を維持するような開度で開いている。発泡粒子充填用加圧ガス入口１７から供給された加圧ガスに発泡粒子を同伴させて型窩７内に発泡粒子が送り込まれる。
Next, the compressed polypropylene resin multistage expanded particles are filled into the mold cavity 7 between the fixed mold 5 and the movable mold 6 by the filling
型窩７を構成する固定型５と移動型６は発泡粒子を通さないが空気や蒸気を通すことができる通気口８を有しており、発泡粒子が型窩７内に送り込まれると空気は通気口８を通って型窩７外に排出され、発泡粒子は型窩７内に残留する。発泡粒子が型窩７内に十分充填されると空気が型窩７内に侵入せず発泡粒子圧縮タンク１に逆流する。このとき充填機１６内に存在する発泡粒子は押し戻され充填機１６は空になる（自然ブローバック）。充填機１６内の発泡粒子が押し戻された後、ピストンプラグ１９により、金型の発泡粒子充填口１８が閉塞される。
The fixed mold 5 and the movable mold 6 constituting the mold cavity 7 have a
充填が終了したのち、発泡粒子圧縮タンク１および金型内の過剰の空気を排気弁１４より逃し、金型内の圧力を開放、好ましくは大気圧とし、充填されている圧縮されたポリプロピレン系樹脂多段発泡粒子を膨張させる。そののち、加熱用水蒸気が蒸気ライン１０から金型４内に供給され、型窩７に充填されたポリプロピレン系樹脂発泡粒子を加熱し、発泡粒子間を融着せしめる。該蒸気の圧力は通常０．１８ＭＰａ以上であるのが好ましい。また、金型の加熱温度および加熱時間は金型の大きさや発泡粒子の種類などに応じて適宜調整されるが、通常加熱温度は１１６〜１５２℃、なかでも１２０〜１４５℃、加熱時間は７〜３０秒間、なかでも８〜２０秒間であるのが好ましい。
After the filling is finished, excess air in the foamed particle compression tank 1 and the mold is released from the
実際には次のような加熱工程が採用されることが多い。
１）予備加熱工程：移動型、固定型の蒸気弁１１、ドレン弁１２及び排気弁１４を開いた状態で下記両面加熱時よりも低圧の蒸気を金型内に流す。加熱時間は１〜２０秒程度である。
２）一方加熱工程：移動型蒸気弁を閉、固定型蒸気弁を開、移動型ドレン弁を開、固定型ドレン弁を閉及び排気弁１４を開の状態で両面加熱時よりも低圧の蒸気を金型内に流す。加熱時間は１〜２０秒程度である。
３）逆一方加熱工程：移動型蒸気弁を開、固定型蒸気弁を閉、移動型ドレン弁を閉、固定型ドレン弁を開及び排気弁を開の状態で両面加熱時よりも低圧の蒸気を金型内に流す。加熱時間は１〜２０秒程度である。
４）両面加熱工程（本加熱工程）：移動型、固定型の蒸気弁を開、移動型、固定型のドレン弁を閉の状態で蒸気を金型内に流す。加熱時間は７〜３０秒程度である。両面加熱工程で型窩内は最も高い温度となる。このときの加熱温度が上記１１６〜１５２℃である。
In practice, the following heating process is often employed.
1) Preheating step: With the movable and fixed
2) One heating step: steam at a lower pressure than during double-sided heating with the mobile steam valve closed, the stationary steam valve opened, the mobile drain valve opened, the stationary drain valve closed and the
3) Reverse one-side heating process: open steam, close fixed steam valve, close mobile drain valve, open fixed drain valve and open exhaust valve, lower pressure steam than double-sided heating In a mold. The heating time is about 1 to 20 seconds.
4) Double-side heating step (main heating step): Steam is flown into the mold with the movable and fixed steam valves open and the movable and fixed drain valves closed. The heating time is about 7 to 30 seconds. The mold cavity has the highest temperature in the double-sided heating process. The heating temperature at this time is said 116-152 degreeC.
加熱工程の後、型内発泡成形体は水冷等により冷却され、つぎに金型を型開きにすることにより、ポリプロピレン系樹脂型内発泡成形体が取り出される。金型には通常、型内発泡成形体の面圧を測定する面圧計が取り付けられており、所定の面圧に低下したときに金型が型開きされる。 After the heating step, the in-mold foam-molded product is cooled by water cooling or the like, and then the polypropylene-based resin in-mold foam-molded product is taken out by opening the mold. Usually, a surface pressure gauge for measuring the surface pressure of the in-mold foam-molded product is attached to the mold, and the mold is opened when the surface pressure is reduced to a predetermined surface pressure.
本発明の製造方法により得られるポリプロピレン系樹脂型内発泡成形体は、断熱材、緩衝包装材、自動車内装部材、自動車バンパー用芯材などの用途に用いることができる。高発泡倍率の型内発泡成形体が使用されることが多い緩衝包装材に、本発明の製造方法を用いて得られる型内発泡成形体を使用することは、特に望ましい使用法である。 The polypropylene resin-in-mold foam-molded product obtained by the production method of the present invention can be used for applications such as a heat insulating material, a cushioning packaging material, an automobile interior member, and a core material for an automobile bumper. It is a particularly desirable usage method to use an in-mold foam molded product obtained by using the production method of the present invention for a buffer packaging material in which an in-mold foam molded product having a high expansion ratio is often used.
つぎに実施例および比較例をあげて本発明のポリプロピレン系樹脂型内発泡成形体の製造方法をさらに詳細に説明するが、本発明はかかる実施例のみに限定されるものではない。また、実施例及び比較例における評価は下記の方法で行った。 Next, examples and comparative examples will be given to describe the method for producing a polypropylene resin-in-mold foam-molded article of the present invention in more detail, but the present invention is not limited to such examples. Moreover, the evaluation in an Example and a comparative example was performed with the following method.
（ＤＳＣ比）
ＤＳＣ比は、示差走査熱量計を用いて、圧縮成形に供する前（多段発泡後）のポリプロピレン系樹脂多段発泡粒子５〜６ｍｇを１０℃／ｍｉｎの昇温速度で４０℃から２２０℃まで昇温する際に得られる、２つのピークを有する融解曲線にから求める。該融解ピークのうち低温側の融解ピーク熱量Ｑｌと、高温側の融解ピーク熱量Ｑｈから算出した、高温側の融解ピークの比率Ｑｈ／（Ｑｌ＋Ｑｈ）×１００で表されるパラメータである。
(DSC ratio)
The DSC ratio was raised from 40 ° C. to 220 ° C. at a rate of temperature increase of 10 ° C./min using 5 to 6 mg of polypropylene resin multi-stage expanded particles before being subjected to compression molding (after multi-stage expansion) using a differential scanning calorimeter. Obtained from a melting curve having two peaks obtained in the process. The melting peak is a parameter represented by the ratio Qh / (Ql + Qh) × 100 of the melting peak on the high temperature side calculated from the melting peak heat amount Ql on the low temperature side and the melting peak heat amount Qh on the high temperature side.
（嵩密度）
円筒状容器に発泡粒子を充填し、容器の開口部を越えた発泡粒子を取り除いて容器内の発泡粒子の重量を測定し、発泡粒子の重量を容器体積で除して嵩密度を求める。
(The bulk density)
The cylindrical container is filled with expanded particles, the expanded particles beyond the opening of the container are removed, the weight of the expanded particles in the container is measured, and the bulk density is obtained by dividing the weight of the expanded particles by the container volume.
（成形体発泡倍率）
型内発泡成形体の重量ｗ（ｇ）および水没体積ｖ（ｃｍ3）を求め、樹脂の密度ｄ（ｇ／ｃｍ3）から次式により求める。
発泡倍率＝ｄ×ｖ／ｗ
(Molded foam expansion ratio)
The weight w (g) and the submerged volume v (cm 3 ) of the in-mold foam-molded product are obtained, and obtained from the resin density d (g / cm 3 ) by the following equation.
Foaming ratio = d × v / w
（成形体における発泡粒子充填口付近の融着状態）
得られた型内発泡成形体を２５℃で２時間静置し、次いで７５℃に温調した恒温室内に１５時間静置した後、取り出し、２５℃で放冷した。該型内発泡成形体における発泡粒子充填口にある発泡粒子を軽く爪で引き掻き、発泡粒子が一粒でも剥がれた場合を融着状態が不良、剥がれない場合を融着状態が良好、であるとした。後記するように成形機は２カ所の発泡粒子充填口を有する。充填口付近融着状態の評価は４ショットの型内発泡成形を行い、４個の型内発泡成形体にある合計８カ所の充填口付近の融着状態を評価した。表１における充填口付近融着状態の評価の数字は８カ所の充填口付近の不良であった個数を示す。例えば、数字が０の場合は８カ所すべての発泡粒子充填口付近の融着状態が良好である場合である。数字が１の場合は８カ所中、１カ所の発泡粒子充填口付近の融着状態が不良であるが他の７カ所は良好である場合である。
(Fused state near the filler filling port in the molded product)
The obtained in-mold foamed molded product was allowed to stand at 25 ° C. for 2 hours, and then allowed to stand in a thermostatic chamber adjusted to 75 ° C. for 15 hours, then taken out and allowed to cool at 25 ° C. The foamed particles in the foamed particle filling port in the in-mold foam molded product are lightly scratched with a nail, and even if one of the foamed particles is peeled off, the fused state is poor, and the fused state is good when not peeled It was. As will be described later, the molding machine has two foamed particle filling ports. The evaluation of the fusion state near the filling port was performed by performing 4-shot in-mold foam molding, and evaluating the fusion state in the vicinity of the eight filling ports in the four in-mold foam moldings. The numbers in the evaluation of the fusion state near the filling port in Table 1 indicate the number of defects near the eight filling ports. For example, when the number is 0, the fused state in the vicinity of all 8 expanded particle filling ports is good. When the number is 1, the fused state in the vicinity of the expanded particle filling port at one place is poor among the eight places, but the other seven places are good.
（圧縮比）
得られた成形体密度（ｇ／Ｌ）を実重量と水没法による体積から算出し、これを、使用したポリプロピレン系樹脂多段発泡粒子の嵩密度（ｇ／Ｌ）で除した値を圧縮比とした。
(Compression ratio)
The density of the obtained molded body (g / L) was calculated from the actual weight and the volume by the submerging method, and the value obtained by dividing this by the bulk density (g / L) of the polypropylene resin multistage expanded particles used was the compression ratio. did.
（融着率）
得られた型内発泡成形体を２５℃で２時間静置し、次いで７５℃に温調した恒温室内に１５時間静置した後、取り出し、２５℃で放冷した。該型内発泡成形体を割った際に発泡粒子内で破断している粒子の割合を検査し、その割合を融着率とした。
(Fusion rate)
The obtained in-mold foamed molded product was allowed to stand at 25 ° C. for 2 hours, and then allowed to stand in a thermostatic chamber adjusted to 75 ° C. for 15 hours, then taken out and allowed to cool at 25 ° C. When the in-mold foam molded product was broken, the ratio of the broken particles in the expanded particles was examined, and the ratio was defined as the fusion rate.
（実施例１、実施例２および比較例１）
基材樹脂として、表１に示した特性を有するポリプロピレン系樹脂を使用した。樹脂１〜３はエチレンを共重合単量体成分として含有するポリプロピレン樹脂であり、樹脂２および３は減成処理によって得られたポリプロピレン樹脂である。この樹脂１００重量部に対し、親水性物質としてグリセリンを０．２重量部、発泡核剤としてタルクを０．０２重量部添加してドライブレンドし、押出機内で溶融混練した後、円形ダイよりストランド状に押出し、水冷後、カッターで切断し、一粒の重量が１．３ｍｇ／粒、ほぼ円柱形状の樹脂粒子を得た。得られた樹脂粒子１００重量部、水２００重量部、塩基性第三リン酸カルシウム０．５重量部、アルキルスルフォン酸ソーダ０．０１重量部を耐圧オートクレーブ中に仕込んだ。
(Example 1, Example 2 and Comparative Example 1)
A polypropylene resin having the characteristics shown in Table 1 was used as the base resin. Resins 1 to 3 are polypropylene resins containing ethylene as a comonomer component, and resins 2 and 3 are polypropylene resins obtained by degradation. To 100 parts by weight of this resin, 0.2 parts by weight of glycerin as a hydrophilic substance and 0.02 parts by weight of talc as a foam nucleating agent are added, dry blended, melt-kneaded in an extruder, and then a strand from a circular die. After being cooled in water and cooled with water, it was cut with a cutter to obtain approximately cylindrical resin particles having a weight of 1.3 mg / grain. 100 parts by weight of the obtained resin particles, 200 parts by weight of water, 0.5 parts by weight of basic tribasic calcium phosphate, and 0.01 parts by weight of sodium alkyl sulfonate were charged into a pressure-resistant autoclave.
表１に示す発泡温度において表１に示す圧力（発泡圧力）になるように二酸化炭素を添加し発泡温度まで加熱した。その後、オートクレーブ下部のバルブを開き、内容物を大気圧下に放出して一段発泡粒子を得た。得られた一段発泡粒子を耐圧容器中で空気により加圧し、一段発泡粒子に内圧を付与した後、水蒸気で加熱し二段発泡させた。得られた二段発泡粒子の発泡倍率およびＤＳＣ比を表１に示す。 Carbon dioxide was added and heated to the foaming temperature so that the pressure (foaming pressure) shown in Table 1 was reached at the foaming temperature shown in Table 1. Then, the valve | bulb of the autoclave lower part was opened, the content was discharge | released under atmospheric pressure, and the 1st stage | paragraph expanded particle was obtained. The obtained first-stage expanded particles were pressurized with air in a pressure-resistant container to give an internal pressure to the first-stage expanded particles, and then heated with water vapor to be two-stage expanded. Table 1 shows the expansion ratio and DSC ratio of the obtained two-stage expanded particles.
得られた二段発泡粒子を発泡粒子圧縮タンクに充填し表１に示す圧縮圧で表１に示す圧縮比とし、ほぼこの圧力下で成形機金型の型窩内に圧縮された二段発泡粒子を移送した。この後、金型内の圧力を大気圧に開放し、水蒸気による加熱により型内発泡成形した。成形機は３００ｍｍ×４００ｍｍ×５０ｍｍの寸法を有する直方体形状の型内成形機型窩を１個有しており、型窩の固定型側に直径１７ｍｍの円形充填口を有する充填機を２機有していた。充填口の取り付け位置は長さ方向中心線上である。 The obtained two-stage foamed particles are filled into a foamed particle compression tank, and the compression ratio shown in Table 1 is set to the compression ratio shown in Table 1. Under this pressure, the two-stage foam is compressed into the mold cavity of the molding machine mold. The particles were transferred. Thereafter, the pressure in the mold was released to atmospheric pressure, and in-mold foam molding was performed by heating with water vapor. The molding machine has one cuboid-shaped in-mold molding machine mold cavity with dimensions of 300 mm x 400 mm x 50 mm, and two filling machines with a circular filling port with a diameter of 17 mm on the fixed mold side of the mold cavity Was. The attachment position of the filling port is on the longitudinal center line.
加熱は予備加熱３秒（移動型、固定型のドレン弁を開いた状態）で行い、一方加熱５秒、逆一方加熱５秒、両面加熱１０秒（両面加熱時の蒸気圧力は表１に示した。）で行った。加熱工程を完了後、予冷（ドレン弁を閉じた状態で冷却）を１０秒行い、次に面圧が０．１ＭＰａになるまで水冷を行った後、離型し、発泡成形体を得た。 Heating is performed in 3 seconds of preheating (with the movable and fixed drain valves opened), while heating for 5 seconds, reverse heating for 5 seconds, double-sided heating for 10 seconds (vapor pressure during double-sided heating is shown in Table 1. ). After completing the heating step, pre-cooling (cooling with the drain valve closed) was performed for 10 seconds, and then water-cooling was performed until the surface pressure became 0.1 MPa, followed by release to obtain a foamed molded product.
得られた型内発泡成形体の発泡粒子充填口付近の粒子融着状態および成形体融着率を両面加熱時の蒸気圧力が０．３０、０．３３及び０．３６ＭＰａ（Ｇ）の場合について評価した。評価結果を表１に示す。 In the case of the vapor pressure of 0.30, 0.33 and 0.36 MPa (G) at the time of double-sided heating, the particle fusion state in the vicinity of the foamed particle filling port and the molding fusion rate of the obtained in-mold foam molded product evaluated. The evaluation results are shown in Table 1.
表１から明らかなようにＭｗ／Ｍｎが大きい樹脂１を使用した場合（実施例１）、樹脂の融点が高いにもかかわらず、型内発泡成形体の発泡粒子充填口付近の融着状態は良好であった。また、Ｍｗ／Ｍｎが大きい樹脂２を使用した場合（実施例２）、同じ樹脂の融点を有するがＭｗ／Ｍｎが小さい樹脂３を使用した場合（比較例１）に比較し型内発泡成形体の発泡粒子充填口付近の融着状態は良好であった。なお、表１から明らかなように実施例１〜２、比較例１における型内発泡成形体の融着率はほぼ樹脂融点に対応していた。
As is clear from Table 1, when the resin 1 having a large Mw / Mn was used (Example 1), the fusion state in the vicinity of the foamed particle filling port of the in-mold foam molded product was as follows, despite the high melting point of the resin. It was good. Further, when the
（比較例２）
発泡剤としてブタンを使用し、発泡条件として表１に記載の条件を使用し、二段発泡せず除圧発泡（一段発泡）によって一挙に嵩密度１８．８ｇ／Ｌの発泡粒子を得たほかは実施例１と同様にして発泡粒子を製造した。得られた発泡粒子を用い表１に示した型内発泡成形条件を用いたほかは実施例１と同様に型内発泡成形体を製造した。型内発泡成形体の評価結果を表１に示す。表１から明らかなように実施例１と同じ樹脂を使用し、発泡粒子の発泡倍率はほぼ同じであるにもかかわらず型内発泡成形体の発泡粒子充填口付近の粒子融着状態はよくなかった。
(Comparative Example 2)
In addition to using butane as a foaming agent and using the conditions shown in Table 1 as foaming conditions, expanded particles with a bulk density of 18.8 g / L were obtained all at once by decompression foaming (single-stage foaming) without two-stage foaming. Produced foamed particles in the same manner as in Example 1. An in-mold foam molded article was produced in the same manner as in Example 1 except that the obtained foamed particles were used and the in-mold foam molding conditions shown in Table 1 were used. Table 1 shows the evaluation results of the in-mold foam molding. As is clear from Table 1, the same resin as in Example 1 was used, and the expanded state of the particles in the vicinity of the expanded particle filling port of the in-mold expanded molded product was not good although the expansion ratio of the expanded particles was almost the same. It was.
１ 発泡粒子圧縮タンク
２ 発泡粒子供給口
３ 加圧ガス入口
４ 金型
５ 固定型
６ 移動型
７ 型窩
８ 通気口
９ スチームチャンバー
１０ 蒸気ライン
１１ 蒸気弁
１２ ドレン弁
１３ 金型ガス圧力調整バルブ
１４ 排気弁
１５ 排気口
１６ 充填機
１７ 発泡粒子充填用加圧ガス入口
１８ 発泡粒子充填口
１９ ピストンプラグ
２０ 均圧ライン
DESCRIPTION OF SYMBOLS 1 Expanded
Claims (2)
重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）の比（Ｍｗ／Ｍｎ）が３．６以上であるポリプロピレン系樹脂を基材樹脂とするポリプロピレン系樹脂粒子を耐圧容器内で分散媒に分散させ、発泡剤として二酸化炭素を含む発泡剤を添加した後、ポリプロピレン系樹脂粒子の軟化温度以上の温度に加熱し、ポリプロピレン系樹脂粒子内に二酸化炭素を含む発泡剤を含浸させたのち、耐圧容器の一端を開放してポリプロピレン系樹脂粒子を耐圧容器内よりも低圧の雰囲気中に放出することによりポリプロピレン系樹脂発泡粒子を製造する工程、
得られたポリプロピレン系樹脂発泡粒子をさらに発泡させ、ポリプロピレン系樹脂多段発泡粒子を製造する工程。 A method for producing an expanded foam in a polypropylene resin mold by a compression filling method using polypropylene resin multistage expanded particles obtained through the following steps.
A polypropylene resin particle having a base resin of a polypropylene resin having a ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.6 or more is dispersed in a dispersion medium in a pressure vessel. After adding a foaming agent containing carbon dioxide as a foaming agent, heating to a temperature equal to or higher than the softening temperature of the polypropylene resin particles, impregnating the polypropylene resin particles with a foaming agent containing carbon dioxide, A step of producing polypropylene resin expanded particles by releasing one end and releasing the polypropylene resin particles in a low-pressure atmosphere than in the pressure vessel;
The step of further foaming the obtained polypropylene resin expanded particles to produce polypropylene resin multistage expanded particles.
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