JP2010275336A - Process for preparing polyvinyl alcohol-based foam utilizing freeze-gelling of polyvinyl alcohol - Google Patents
Process for preparing polyvinyl alcohol-based foam utilizing freeze-gelling of polyvinyl alcohol Download PDFInfo
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- JP2010275336A JP2010275336A JP2009126118A JP2009126118A JP2010275336A JP 2010275336 A JP2010275336 A JP 2010275336A JP 2009126118 A JP2009126118 A JP 2009126118A JP 2009126118 A JP2009126118 A JP 2009126118A JP 2010275336 A JP2010275336 A JP 2010275336A
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- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 81
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 81
- 239000006260 foam Substances 0.000 title claims abstract description 56
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 29
- 239000000843 powder Substances 0.000 claims abstract description 21
- 239000007864 aqueous solution Substances 0.000 claims abstract description 19
- 239000000919 ceramic Substances 0.000 claims abstract description 12
- 229910052751 metal Inorganic materials 0.000 claims abstract description 11
- 239000002184 metal Substances 0.000 claims abstract description 11
- 238000005187 foaming Methods 0.000 claims description 26
- 239000004088 foaming agent Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 10
- 239000000835 fiber Substances 0.000 claims description 8
- 229920005989 resin Polymers 0.000 claims description 7
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- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 6
- 244000005700 microbiome Species 0.000 claims description 6
- 238000010257 thawing Methods 0.000 claims description 6
- 229920002554 vinyl polymer Polymers 0.000 claims description 6
- 229920002472 Starch Polymers 0.000 claims description 5
- 230000008018 melting Effects 0.000 claims description 5
- 238000002844 melting Methods 0.000 claims description 5
- 235000019698 starch Nutrition 0.000 claims description 5
- 229920002261 Corn starch Polymers 0.000 claims description 4
- 239000006061 abrasive grain Substances 0.000 claims description 4
- 239000008120 corn starch Substances 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 239000008107 starch Substances 0.000 claims description 4
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 239000012784 inorganic fiber Substances 0.000 claims description 3
- 239000000243 solution Substances 0.000 abstract description 9
- 238000002347 injection Methods 0.000 abstract description 7
- 239000007924 injection Substances 0.000 abstract description 7
- 238000001125 extrusion Methods 0.000 abstract description 6
- 238000005245 sintering Methods 0.000 abstract description 6
- 239000004604 Blowing Agent Substances 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 11
- 239000004094 surface-active agent Substances 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 239000000463 material Substances 0.000 description 10
- 239000011148 porous material Substances 0.000 description 10
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 9
- 239000000499 gel Substances 0.000 description 9
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical class CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 8
- 230000008014 freezing Effects 0.000 description 8
- 238000007710 freezing Methods 0.000 description 8
- 238000002156 mixing Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 238000004132 cross linking Methods 0.000 description 5
- 238000001879 gelation Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 238000006359 acetalization reaction Methods 0.000 description 4
- -1 alkylbenzene sulfonate Chemical class 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 4
- 230000008025 crystallization Effects 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000005909 Kieselgur Substances 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 239000003431 cross linking reagent Substances 0.000 description 3
- 239000000017 hydrogel Substances 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical class CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 239000011342 resin composition Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000007127 saponification reaction Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical class CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000003599 detergent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 229920002994 synthetic fiber Polymers 0.000 description 2
- 229920003002 synthetic resin Polymers 0.000 description 2
- 239000000057 synthetic resin Substances 0.000 description 2
- 238000004065 wastewater treatment Methods 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 241000233866 Fungi Species 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000003945 anionic surfactant Substances 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 150000001555 benzenes Chemical class 0.000 description 1
- 238000006065 biodegradation reaction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000007809 chemical reaction catalyst Substances 0.000 description 1
- 230000001112 coagulating effect Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229920006248 expandable polystyrene Polymers 0.000 description 1
- 230000003631 expected effect Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000010097 foam moulding Methods 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 150000002334 glycols Chemical class 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000002736 nonionic surfactant Substances 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920002959 polymer blend Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 150000003613 toluenes Chemical class 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000004711 α-olefin Substances 0.000 description 1
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Biological Depolymerization Polymers (AREA)
Abstract
Description
本発明は、ポリビニルアルコールの凍結ゲル化を利用したポリビニルアルコール系発泡体の作製方法に関するものである。 The present invention relates to a method for producing a polyvinyl alcohol foam using freeze-gelation of polyvinyl alcohol.
従来の合成樹脂の多孔体には、比較的空隙率が高い発泡体をはじめとして、多種多様のものが存在する。このような合成樹脂の多孔体のなかで大きなウエートを占める発泡体としては、発泡スチロール（ＥＰＳ）、ポリウレタン等が存在し、緩衝材、断熱材、軽量構造物等に広く利用されている。さらには、様々な高分子の発泡体も作製され、その特徴に応じた利用が行われている。しかし、現在、その多くはリサイクル、廃棄物としての問題を抱えており、梱包材として利用されるとき特にその問題は大きい。その中で注目を集めるのが、生分解性材料による発泡体である。現在、パルプ、天然繊維、澱粉類等の天然資源を利用した様々な発泡体が作製されており、その利用が図られている。
一方、ポリビニルアルコールは合成素材であり、安定な大量合成が可能な素材でありながら生分解性であるという特徴を持つ。そのため、このポリビニルアルコールより発泡体を始めとする多孔体を作製すれば、合成素材でありながら生分解性を持つ発泡体、緩衝材等が作製できることとなる。
このようなポリビニルアルコール製の発泡体、多孔体の作製方法には、従来、次のようなものが知られている。
（１）ポリビニルアルコール、発泡剤等を含むポリビニルアルコール系樹脂組成物を押出装置、射出装置等で加熱溶融し、その溶融組成物を押出し発泡、射出発泡等により発泡させて発泡体を作製する方法（特許文献１）。
（２）ポリビニルアルコール水溶液と多孔化剤とを含む混合液を成形し、ポリビニルアルコールを凝析する塩を含む水溶液中で処理し、ポリビニルアルコールの結晶化を促進してポリビニルアルコールを凝析させるとともに、澱粉等の多孔化剤を酸条件下で取り除きスポンジ化して多孔体を作製する方法（特許文献２）。
（３）ポリビニルアルコール水溶液を凍結し、ポリビニルアルコールと氷との相分離による多孔質のポリビニルアルコールゲルを形成した後、氷が融解しかつ該ゲルが融解しない温度でホルムアルデヒド等を加え、ホルマール化等のアセタール化による架橋反応を開始させて不溶化し、その後、余剰の薬剤を洗い出してスポンジを作製する方法（特許文献３）。
（４）ポリビニルアルコール系水溶液に架橋剤及び反応触媒を添加混合し、凍結乾燥した後、熱処理して架橋、不溶化する多孔体の作成方法（特許文献４）。
There are a wide variety of conventional synthetic resin porous bodies, including foams having a relatively high porosity. Among such synthetic resin porous bodies, foams that occupy a large weight include foamed polystyrene (EPS), polyurethane, and the like, which are widely used for cushioning materials, heat insulating materials, lightweight structures, and the like. Furthermore, various polymer foams are also produced and used according to their characteristics. However, many of them currently have problems as recycling and waste, and the problems are particularly serious when used as packaging materials. Among them, a foam made of a biodegradable material attracts attention. Currently, various foams using natural resources such as pulp, natural fibers, and starches have been produced and are being used.
On the other hand, polyvinyl alcohol is a synthetic material, and is characterized by being biodegradable while being a material capable of stable mass synthesis. Therefore, if a porous body such as a foam is produced from this polyvinyl alcohol, a foam, a buffer material, etc. having a biodegradability can be produced while being a synthetic material.
As a method for producing such a polyvinyl alcohol foam or porous body, the following has been conventionally known.
(1) A method of producing a foam by heating and melting a polyvinyl alcohol-based resin composition containing polyvinyl alcohol, a foaming agent and the like with an extrusion apparatus, an injection apparatus, and the like, and foaming the molten composition by extrusion foaming, injection foaming, or the like. (Patent Document 1).
(2) A liquid mixture containing an aqueous polyvinyl alcohol solution and a porosifying agent is formed, treated in an aqueous solution containing a salt that coagulates polyvinyl alcohol, accelerates crystallization of polyvinyl alcohol, and coagulates polyvinyl alcohol. A method of producing a porous body by removing a porous agent such as starch under an acid condition to form a sponge (Patent Document 2).
(3) Freezing a polyvinyl alcohol aqueous solution to form a porous polyvinyl alcohol gel by phase separation between polyvinyl alcohol and ice, and then adding formaldehyde or the like at a temperature at which the ice melts and the gel does not melt, etc. A method of starting a cross-linking reaction by acetalization to insolubilize, and then washing out excess chemicals to produce a sponge (Patent Document 3).
(4) A method for producing a porous body in which a crosslinking agent and a reaction catalyst are added to and mixed with a polyvinyl alcohol aqueous solution, freeze-dried, and then cross-linked and insolubilized by heat treatment (Patent Document 4).
しかしながら、このような従来のポリビニルアルコール製の発泡体、多孔体の作製方法には、それぞれ、以下のような問題点が存在している。
上記（１）の作製方法では、空隙率が高く、空孔も比較的大きくしうる発泡体を大量生産することができ、しかも、架橋しない限り、生分解性も保持しうるが、押出装置や射出装置のような高価な装置を必要とするデメリットがある。また、ポリビニルアルコール系樹脂組成物を加熱溶融するため、予め微生物を混入させた組成物等、高温の処理を避けなければならない混入物を含む組成物に適用することはできないという問題点が存在する。
However, such conventional methods for producing a polyvinyl alcohol foam and porous body have the following problems.
In the production method of (1) above, it is possible to mass-produce a foam having a high porosity and relatively large pores, and it can maintain biodegradability as long as it is not crosslinked. There is a demerit that requires an expensive device such as an injection device. In addition, since the polyvinyl alcohol resin composition is heated and melted, there is a problem that it cannot be applied to a composition containing a contaminant that must avoid high-temperature treatment, such as a composition in which microorganisms are mixed. .
上記（２）の作製方法では、ポリビニルアルコールを溶融するような高温に加熱することなく、しかも、押出装置や射出装置等の高価な装置を用いることなく発泡体を作製できる。しかしながら、発泡剤により発泡させないため、高い空隙率のものや大きな空孔のものは作製しにくいという問題点があるし、また、水溶液を成形して凝析するため、正確な形状に成形しにくいという問題点がある。さらに、ポリビニルアルコールを凝析するための塩や多孔化剤を取り除くための酸を必要とするため、コスト高となる問題点が存在する。
なお、特許文献２には、多孔化剤として発泡剤も使用できる旨が記載されているが、その具体的な実施例が全く存在せず、結晶化促進による凝析と発泡剤による発泡成形との関連についても記載されていないから、ポリビニルアルコール製の発泡体を作製する方法については、当業者が容易に実施をすることができる程度に開示されていない。
In the production method (2), a foam can be produced without heating to a high temperature that melts polyvinyl alcohol and without using an expensive device such as an extrusion device or an injection device. However, since it is not foamed by a foaming agent, there is a problem that it is difficult to produce a product with a high porosity or a large pore, and it is difficult to form into an accurate shape because it forms and coagulates an aqueous solution. There is a problem. Furthermore, since a salt for coagulating polyvinyl alcohol and an acid for removing the porosifying agent are required, there is a problem that the cost is increased.
In addition, Patent Document 2 describes that a foaming agent can be used as a porosifying agent, but there is no specific example at all, such as coagulation by crystallization promotion and foam molding with a foaming agent. Since there is no description about the relationship, the method for producing a foam made of polyvinyl alcohol is not disclosed to the extent that a person skilled in the art can easily carry it out.
上記（３）の作製方法では、ポリビニルアルコールを溶融するような高温に加熱することなく、しかも、押出装置や射出装置等の高価な装置を用いることなく発泡体を作製できる。しかしながら、発泡剤により発泡させないため、高い空隙率のものや大きな空孔のものは作製しにくいという問題点がある。また、ホルムアルデヒド等を用いて架橋を行うため、作業環境の悪化、環境汚染等の問題点が存在するし、さらに、ポリビニルアルコールは、架橋されているため、その生分解性が充分に発揮できないという問題点が存在する。 In the production method (3), a foam can be produced without heating to a high temperature that melts polyvinyl alcohol and without using an expensive device such as an extrusion device or an injection device. However, since foaming is not performed by a foaming agent, there is a problem that it is difficult to produce a material having a high porosity or a large pore. In addition, since cross-linking is performed using formaldehyde and the like, there are problems such as deterioration of the working environment and environmental pollution, and furthermore, polyvinyl alcohol is cross-linked and thus cannot fully exhibit its biodegradability. There is a problem.
上記（４）の作製方法は、上記（３）の作製方法において、架橋にホルムアルデヒド等を用いる問題点を解消するものといえる。しかしながら、発泡剤により発泡させないため、高い空隙率のものや大きな空孔のものが作製しにくいという問題点は、上記（３）と同様であるし、また、ポリビニルアルコールが架橋されているため、その生分解性が充分に発揮できないという問題点が存在する点でも上記（３）と同様である。 It can be said that the production method (4) above solves the problem of using formaldehyde or the like for crosslinking in the production method (3). However, since it is not foamed by the foaming agent, the problem that it is difficult to produce a product with a high porosity or a large pore is the same as the above (3), and because polyvinyl alcohol is crosslinked, It is the same as (3) above in that there is a problem that the biodegradability cannot be sufficiently exhibited.
一方、発泡体そのものの作製を目的とするものではないが、従来から、廃水処理用担体、バイオリアクター用担体等に用いるポリビニルアルコール系含水ゲルの製造方法として、ポリビニルアルコールと微生物・生菌体等からなる懸濁水溶液を凍結、成形し、必要により架橋することが知られている。しかしながら、そのような含水ゲルの発泡について、従来、検討がなされていなかった。 On the other hand, it is not intended to produce a foam itself, but conventionally, as a method for producing a polyvinyl alcohol-based hydrogel used for a carrier for wastewater treatment, a carrier for a bioreactor, etc., polyvinyl alcohol and microorganisms / viable cells, etc. It is known that an aqueous suspension of However, the foaming of such a hydrogel has not been studied conventionally.
また、本発明者らは、金属又はセラミックスの発泡焼結体の製造方法において、焼結される金属粉末又はセラミックス粉末と、バインダーとしてのポリビニルアルコールと、発泡剤とを含む混合液を凍結ゲル化し、解凍後、このゲル化物を発泡・乾燥した後、焼結する技術を開発した（特許文献６）。しかし、この技術は、焼結される金属粉末又はセラミックス粉末の含有を前提とし、金属やセラミックス中に気泡を形成しようとするもので、バインダーとしてのポリビニルアルコール中に気泡を形成することを意図するものではない。しかも、発泡後で焼結前の中間体としての発泡体の物性については、焼結性の検討はなされていたものの、ポリビニルアルコール自体は焼結過程で分解してしまうため、最終製品としてのポリビニルアルコール系発泡体の強度、生分解性等の検討は、全くなされていなかった。 Further, the inventors of the present invention, in a method for producing a foamed sintered body of metal or ceramics, freeze-gelate a mixed solution containing a metal powder or ceramic powder to be sintered, polyvinyl alcohol as a binder, and a foaming agent. Then, after thawing, a technique was developed in which the gelled product was foamed, dried and then sintered (Patent Document 6). However, this technique is intended to form bubbles in metal or ceramics on the premise of containing sintered metal powder or ceramic powder, and is intended to form bubbles in polyvinyl alcohol as a binder. It is not a thing. Moreover, regarding the physical properties of the foam as an intermediate after foaming but before sintering, although sinterability has been studied, polyvinyl alcohol itself decomposes during the sintering process, so that polyvinyl as the final product The strength, biodegradability, etc. of the alcohol-based foam have not been studied at all.
このような背景から、押出装置、射出装置等の大がかりな装置を必要とすることなく、しかも、生分解性を失わせることなくポリビニルアルコールの発泡体を作製する作製方法を開発することを課題としている。 From such a background, an object is to develop a production method for producing a foam of polyvinyl alcohol without requiring a large-scale apparatus such as an extrusion apparatus or an injection apparatus and without losing biodegradability. Yes.
このような背景と課題のもと、生分解性を具備するポリビニルアルコール系発泡体の新たな作製方法を希求する過程で、本発明者は、発泡後で焼結前の中間製品としてのポリビニルアルコール系発泡体の物性について、新たに最終製品としての観点から見直し、該中間製品の製造プロセスが焼結とは無関係のポリビニルアルコール系発泡体の作製に応用できるとの知見を得て、本発明に至ったものである。 Under such background and problems, in the process of seeking a new method for producing a biodegradable polyvinyl alcohol foam, the present inventor made polyvinyl alcohol as an intermediate product after foaming and before sintering. The physical properties of the foam-based foam are newly reviewed from the viewpoint of the final product, and the knowledge that the production process of the intermediate product can be applied to the production of a polyvinyl alcohol-based foam unrelated to sintering has been obtained. It has come.
すなわち、この本発明は以下のことを特徴としている。
１．次の（Ａ）〜（Ｄ）の工程を含むことを特徴とするポリビニルアルコール系発泡体の作製方法。
（Ａ）ポリビニルアルコール単独又はポリビニルアルコールを主成分とする樹脂、及び、発泡剤を含み、焼結される金属粉末、焼結されるセラミックス粉末を含まない水溶液を準備する工程
（Ｂ）該水溶液を凍結ゲル化し、ゲル化物を得る工程
（Ｃ）凍結ゲル化したゲル化物を解凍する工程
（Ｄ）解凍したゲル化物を該ポリビニルアルコールの溶解温度未満の温度で発泡させる工程
２．さらに、次の（Ｅ）の工程を含むことを特徴とする上記１のポリビニルアルコール系発泡体の作製方法。
（Ｅ）発泡後のゲル化物を乾燥させる工程
３．上記水溶液が、上記焼結される金属粉末、焼結されるセラミックス粉末以外の液中に分散した固形成分を含むことを特徴とする上記１又は２のポリビニルアルコール系発泡体の作製方法。
４．上記固形成分が、有機繊維、無機繊維、澱粉、コーンスターチ、微生物、生菌体、研磨砥粒、炭酸カルシウムのいずれか１種又は２種以上であることを特徴とする上記３のポリビニルアルコール系発泡体の作製方法。
５．上記１〜４のいずれかに記載された作製方法により作製されたポリビニルアルコール系発泡体。
That is, the present invention is characterized by the following.
1. The manufacturing method of the polyvinyl alcohol-type foam characterized by including the process of following (A)-(D).
(A) A step of preparing an aqueous solution containing polyvinyl alcohol alone or a resin containing polyvinyl alcohol as a main component and a foaming agent and containing no sintered metal powder and no sintered ceramic powder (B) 1. Step of freezing into gel to obtain gelled product (C) Step of thawing freeze-gelled gelled product (D) Step of foaming thawed gelled product at a temperature lower than the melting temperature of the polyvinyl alcohol Furthermore, the manufacturing method of said 1 polyvinyl alcohol-type foam characterized by including the process of following (E).
(E) Step of drying the gelled product after foaming 3. 3. The method for producing a polyvinyl alcohol-based foam according to 1 or 2 above, wherein the aqueous solution contains a solid component dispersed in a liquid other than the metal powder to be sintered and the ceramic powder to be sintered.
4). 3. The polyvinyl alcohol-based foam according to 3 above, wherein the solid component is one or more of organic fibers, inorganic fibers, starch, corn starch, microorganisms, viable cells, abrasive grains, and calcium carbonate. How to make a body.
5). A polyvinyl alcohol-based foam produced by the production method described in any one of 1 to 4 above.
ポリビニルアルコール等を含む樹脂組成物を凍結ゲル化、解凍後のゲル化物を発泡させることにより、アセタール化（ホルマール化）等の架橋によらないポリビニルアルコール系発泡体の作製が可能である。このことにより、発泡体は生分解性を失わずに発泡体となる。また、この作製方法においては、焼結される金属粉末、焼結されるセラミックス粉末以外の様々な粉体、粒体、繊維等の分散物を含有させて発泡処理が可能であり、このことにより、発泡体の緩衝材等としての機能を一層向上させることも可能である。また、生分解性の緩衝材料は、ゴミ処理、リサイクルの問題から広く市場から求められている素材であり、本発明製品の需要は大きいと考えられる。 By freeze-gelating a resin composition containing polyvinyl alcohol or the like and foaming the gelled product after thawing, it is possible to produce a polyvinyl alcohol-based foam that does not depend on crosslinking such as acetalization (formalization). As a result, the foam becomes a foam without losing biodegradability. In addition, in this production method, it is possible to perform foaming treatment by adding dispersions of various powders, granules, fibers, etc. other than sintered metal powders and sintered ceramic powders. It is also possible to further improve the function of the foam as a cushioning material. In addition, the biodegradable buffer material is a material that is widely demanded from the market due to the problem of waste disposal and recycling, and it is considered that the demand for the product of the present invention is great.
本発明に用いる樹脂は、ポリビニルアルコール単独又はポリビニルアルコールを主成分とするものである。
ポリビニルアルコールとしては、水溶液の状態から凍結ゲル化し、該ゲル化物を解凍したときもゲル化状態を維持する凍結ゲル化能を具備するものであれば、使用することができる。そのような凍結ゲル化能を具備するポリビニルアルコールであれば、その重合度、分子量、ケン化度は、特に限定するものではないが、一般的には、平均重合度が1000以上、ケン化度95％以上が好ましく、分子量80000以上、ケン化度98%以上のものが特に好ましい。ポリビニルアルコールの水溶液としては、濃度が2ｗｔ%以上、25ｗｔ%以下のものが好適に使用できる。
本発明に用いる樹脂は、ポリビニルアルコールが具備する凍結ゲル化能を阻害しない範囲で、他の単量体を共重合したものでもよいし、また、他のポリマーを含有するポリマーブレンドであってもよい。
The resin used in the present invention contains polyvinyl alcohol alone or polyvinyl alcohol as a main component.
Any polyvinyl alcohol can be used as long as it has the ability to freeze and gelate from the state of an aqueous solution and maintain the gelled state even when the gelled product is thawed. If it is polyvinyl alcohol having such a freezing ability, its polymerization degree, molecular weight, saponification degree is not particularly limited, but generally, the average polymerization degree is 1000 or more, saponification degree It is preferably 95% or more, particularly preferably those having a molecular weight of 80,000 or more and a saponification degree of 98% or more. As an aqueous solution of polyvinyl alcohol, one having a concentration of 2 wt% or more and 25 wt% or less can be suitably used.
The resin used in the present invention may be a copolymer obtained by copolymerizing other monomers as long as it does not inhibit the freeze gelation ability of polyvinyl alcohol, or may be a polymer blend containing other polymers. Good.
本発明に用いる発泡剤は、凍結ゲル化物の解凍温度より高く、かつ、ポリビニルアルコールの溶解温度未満の温度、好ましくは30℃から80℃の間の温度で気化する液体あるいは固体で、ポリビニルアルコールに混入可能なものであればよい。例えば、水より沸点の低い炭素数５〜８の炭化水素系発泡剤が例示でき、ペンタン類、ヘキサン類、ヘプタン類、ベンゼン類、トルエン類などが好適に使用できる。このような炭化水素系発泡剤を用いる場合、ポリビニルアルコール水溶液の粘度が十分に高ければ強制攪拌により混入可能であるが、界面活性剤を用いることにより混入が一層容易となる。また、発泡剤を焼成珪藻土等の多孔粒子に含浸した後、該粒子をポリビニルアルコール水溶液に混入すれば、界面活性剤を用いることなく、発泡剤が容易に混入される。
界面活性剤としては様々なものが利用可能であるが、従来公知の何れもが使用でき、例えばアルキルベンゼンスルホン酸塩、α−オレフィンスルホン酸塩、アルキル硫酸エステル塩、アルキルエーテル硫酸エステル塩、アルカンスルホン酸塩等のアニオン系界面活性剤、ポリエチレングリコール誘導体、多価アルコール誘導体等の非イオン系界面活性剤等が挙げられる。
発泡剤の混入量は、一般的には、水溶液100体積部に対して1部から30体積部程度であるが、この混入割合は、必要とする発泡倍率や発泡剤の種類に応じて適宜変更することができる。
また、界面活性剤の使用量も0部から30部程度であるが、活性剤の種類、使用量に応じて適宜変更することができる。
このように調整した、ポリビニルアルコール水溶液を所定の容器に入れ凍結し、12時間以上凍結状態を保持する。必要であれば、凍結と解凍を数度繰り返すことによりより強度の高いゲルを調整する。解凍し、ゲル化したポリビニルアルコールを上記容器から出し、その溶解温度未満の温度で該発泡剤の発泡温度、気化温度以上の温度に保持することにより発泡体とする。詳しいメカニズムは明確ではないが、凍結ゲル化によりポリビニルアルコールの結晶化が促進され、その後の発泡剤による発泡の際に、気泡の発生、拡大、及び、生成した気泡の崩壊することのない存続に耐えうる結晶化、ゲル化がなされたと考えられる。
発泡体としてノルマルペンタンを用いた場合40〜60℃程度の発泡処理温度、ノルマルヘキサンを用いた場合65〜80℃の発泡処理温度が望ましい。また、ゲル化したポリビニルアルコールは80〜85℃程度で再溶解するため、発泡処理はその温度以下で行う必要がある。発泡処理は、必要な形状の発泡体を作製するため、そのような内部形状を有する型内で行っても良い。
発泡が終了した、ポリビニルアルコールのゲル化体は、発泡含水ゲルとして用いる場合は、そのまま使用できるし、乾燥させることによって含水量の小さい発泡体や水を含まない発泡体とすることもできる。本発明の親水性、吸水性に優れたポリビニルアルコール系発泡体は、常温の水中において溶解しないし、常温より昇温した60℃程度までの温度の水中においても溶解しないか、溶解してもその溶解速度は小さいから、その意味において耐水性も具備しているといえる。また、そのような耐水性は、発泡終了後の前記乾燥処理により、一層改善することができる。
本発明のポリビニルアルコール単独又はポリビニルアルコールを主成分とする樹脂、発泡剤を含む水溶液は、金属粉末やセラミックス粉末の焼結体の製造に使用するものではないから、焼結される金属粉末、焼結されるセラミックス粉末を含まないが、それ以外の粉体、粒体、繊維等の固形成分は、混入が可能である。このような固形成分の混入は、発泡体の強度や弾性の調整、燃焼時の燃焼カロリーの調整、増量効果による原料コストの低減、発泡剤をしみこませて混合することによりゲル中に発泡剤を分散させる効果、生分解性の向上、気泡の発生を制御して気孔径を制御する効果、などを期待しておこなう。そのような固形成分としては、パルプ繊維や樹脂繊維等の有機繊維、ガラス繊維やカーボン繊維等の無機繊維、澱粉、コーンスターチ、微生物、生菌体、研磨砥粒（アルミナ、SiC)、炭酸カルシウム等が挙げられ、前記期待される効果に応じて、それらの１種又は２種以上を混入することができる。
なお、本発明のポリビニルアルコール単独又はポリビニルアルコールを主成分とする樹脂は、生分解性の観点から、アセタール化（ホルマール化）やその他の架橋剤により架橋しない方が望ましいが、ゲル化状態を改善するため、生分解性を大幅に低下しない程度に架橋することは許容される。また、そのような架橋は、耐水性の改善を目的とした表面部だけの処理(表面処理)とすることもできる。
The foaming agent used in the present invention is a liquid or solid that evaporates at a temperature higher than the thawing temperature of the frozen gelled product and lower than the melting temperature of the polyvinyl alcohol, preferably between 30 ° C. and 80 ° C. Any material that can be mixed is acceptable. For example, a C5-C8 hydrocarbon blowing agent having a boiling point lower than that of water can be exemplified, and pentanes, hexanes, heptanes, benzenes, toluenes and the like can be suitably used. When such a hydrocarbon-based foaming agent is used, it can be mixed by forced stirring if the viscosity of the polyvinyl alcohol aqueous solution is sufficiently high, but mixing is further facilitated by using a surfactant. Moreover, after impregnating porous particles, such as baking diatomaceous earth, with a foaming agent, if this particle | grain is mixed in polyvinyl alcohol aqueous solution, a foaming agent will be easily mixed, without using surfactant.
Various surfactants can be used, and any conventionally known surfactant can be used, such as alkylbenzene sulfonate, α-olefin sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester salt, alkane sulfone. Anionic surfactants such as acid salts, and nonionic surfactants such as polyethylene glycol derivatives and polyhydric alcohol derivatives.
The mixing amount of the foaming agent is generally about 1 to 30 parts by volume with respect to 100 parts by volume of the aqueous solution, but this mixing ratio is appropriately changed according to the required expansion ratio and the type of the foaming agent. can do.
The amount of the surfactant used is about 0 to 30 parts, but can be appropriately changed according to the type and amount of the surfactant used.
The polyvinyl alcohol aqueous solution adjusted as described above is frozen in a predetermined container and kept in a frozen state for 12 hours or more. If necessary, a stronger gel is prepared by repeating freezing and thawing several times. The polyvinyl alcohol that has been thawed and gelled is taken out of the container and kept at a temperature lower than its melting temperature at a temperature equal to or higher than the foaming temperature and vaporization temperature of the foaming agent to obtain a foam. Although the detailed mechanism is not clear, crystallization of polyvinyl alcohol is promoted by freezing gelation, and when foaming with a subsequent foaming agent, bubbles are generated, expanded, and the generated bubbles do not collapse. It is thought that crystallization and gelation that could be tolerated were performed.
When normal pentane is used as the foam, a foaming temperature of about 40 to 60 ° C., and when normal hexane is used, a foaming temperature of 65 to 80 ° C. is desirable. Moreover, since the gelatinized polyvinyl alcohol is re-dissolved at about 80 to 85 ° C., the foaming treatment needs to be performed at the temperature or lower. The foaming treatment may be performed in a mold having such an internal shape in order to produce a foam having a necessary shape.
When the foamed polyvinyl alcohol gel is used as a foamed hydrogel, it can be used as it is, or it can be dried to form a foam with a low water content or a water-free foam. The polyvinyl alcohol-based foam excellent in hydrophilicity and water absorption of the present invention does not dissolve in water at room temperature, and does not dissolve in water at a temperature up to about 60 ° C. raised from room temperature or even if dissolved. Since the dissolution rate is small, it can be said that it also has water resistance. Further, such water resistance can be further improved by the drying treatment after completion of foaming.
Since the polyvinyl alcohol of the present invention alone or a resin containing a polyvinyl alcohol as a main component and an aqueous solution containing a foaming agent are not used for producing a sintered body of metal powder or ceramic powder, Although the ceramic powder to be bonded is not included, other solid components such as powder, granules, and fibers can be mixed. The mixing of such solid components is to adjust the strength and elasticity of the foam, adjust the calories burned at the time of combustion, reduce the raw material cost due to the increase effect, mix the foaming agent with the foaming agent, and mix the foaming agent in the gel. It is expected in view of the effect of dispersing, improving biodegradability, and controlling the pore size by controlling the generation of bubbles. Such solid components include organic fibers such as pulp fibers and resin fibers, inorganic fibers such as glass fibers and carbon fibers, starch, corn starch, microorganisms, viable cells, abrasive grains (alumina, SiC), calcium carbonate, etc. 1 type or 2 types or more thereof can be mixed according to the expected effect.
In addition, from the viewpoint of biodegradability, it is preferable that the polyvinyl alcohol of the present invention alone or a resin containing polyvinyl alcohol as a main component is not cross-linked by acetalization (formalization) or other cross-linking agents, but improves the gelation state. Therefore, it is allowed to crosslink to such an extent that the biodegradability is not significantly reduced. Such cross-linking can also be a treatment of only the surface portion (surface treatment) for the purpose of improving water resistance.
以下、本発明を実施例によりさらに具体的に説明するが、本発明はこの実施例によって何ら限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.
（実施例１）
ポリビニルアルコール（日本合成化学 NH-26）の８wt%水溶液を５℃に冷却し、発泡剤のノルマルペンタン、界面活性剤（サラヤ、ヤシノミ中性洗剤）と混合する。混合割合はポリビニルアルコール90mlに対してノルマルペンタン5ml、界面活性剤5mlとする。混合した溶液を、任意形状の容器にいれ、凍結庫で凍結する。凍結温度は-10℃とした。そのまま、凍結状態で24時間保持し、その後、室温で解凍する。溶液はゲル化し、凍結したときの形状を維持する。このゲル化した溶液を60℃の恒温槽で加熱し、発泡処理する。発泡時、ゲル化体は体積で8-15倍の発泡倍率で膨張するが、これを乾燥して発泡体を得る。発泡体の平均気孔径は0.5-1.0mm程度、かさ密度は0.05g/cm3程度となる。
Example 1
An 8 wt% aqueous solution of polyvinyl alcohol (Nippon Synthetic Chemical NH-26) is cooled to 5 ° C and mixed with a foaming agent, normal pentane, and a surfactant (Saraya, palm flea neutral detergent). The mixing ratio is 5 ml of normal pentane and 5 ml of surfactant for 90 ml of polyvinyl alcohol. The mixed solution is put into a container of any shape and frozen in a freezer. The freezing temperature was -10 ° C. Hold in the frozen state for 24 hours, and then thaw at room temperature. The solution gels and maintains its shape when frozen. This gelled solution is heated in a constant temperature bath at 60 ° C. and foamed. At the time of foaming, the gelled body expands at a foaming ratio of 8 to 15 times by volume, but this is dried to obtain a foamed body. The average pore diameter of the foam is about 0.5 to 1.0 mm, and the bulk density is about 0.05 g / cm 3 .
（実施例２）
ポリビニルアルコール（日本合成化学 NH-26）の８wt%水溶液を５℃に冷却し、発泡剤のノルマルペンタン、界面活性剤（サラヤ、ヤシノミ中性洗剤）と混合する。混合割合はポリビニルアルコール90mlに対してノルマルペンタン5ml、界面活性剤5mlとする。さらに、コーンスターチ5ｇを溶液に混合する。混合した溶液を、任意形状の容器にいれ、凍結庫で凍結する。凍結温度は-10℃とした。そのまま、凍結状態で24時間保持し、その後、室温で解凍する。溶液はゲル化し、凍結したときの形状を維持する。このゲル化した溶液を60℃の恒温槽で加熱し、発泡処理する。発泡時、ゲル化体は体積で12-20倍の発泡倍率で膨張するが、これを乾燥して発泡体を得る。発泡体の平均気孔径は0.3-0.5mm程度と実施例１と比較して細かくなり、かさ密度は0.03g/cm3程度となる。
(Example 2)
An 8 wt% aqueous solution of polyvinyl alcohol (Nippon Synthetic Chemical NH-26) is cooled to 5 ° C and mixed with a foaming agent, normal pentane, and a surfactant (Saraya, palm flea neutral detergent). The mixing ratio is 5 ml of normal pentane and 5 ml of surfactant for 90 ml of polyvinyl alcohol. Furthermore, 5 g of corn starch is mixed into the solution. The mixed solution is put into a container of any shape and frozen in a freezer. The freezing temperature was -10 ° C. Hold in the frozen state for 24 hours, and then thaw at room temperature. The solution gels and maintains its shape when frozen. This gelled solution is heated in a constant temperature bath at 60 ° C. and foamed. At the time of foaming, the gelled body expands at a foaming ratio of 12 to 20 times by volume, but is dried to obtain a foamed body. The average pore diameter of the foam is about 0.3-0.5 mm, which is finer than that of Example 1, and the bulk density is about 0.03 g / cm 3 .
（実施例３）
ポリビニルアルコール（日本合成化学 NH-26）の８wt%水溶液を５℃に冷却し、発泡剤のノルマルペンタンに3時間浸して置いた焼成珪藻土と混合する。混合割合はポリビニルアルコール100mlに対して珪藻土固形分20gとする。珪藻土は空隙を有しており、その中にノルマルペンタンがしみ込んでいる。混合した溶液を、任意形状の容器にいれ、凍結庫で凍結する。凍結温度は-10℃とした。そのまま、凍結状態で24時間保持し、その後、室温で解凍する。溶液はゲル化し、凍結したときの形状を維持する。このゲル化した溶液を60℃の恒温槽で加熱し、発泡処理する。発泡時、ゲル化体は体積で8-10倍の発泡倍率で膨張するが、これを乾燥して発泡体を得る。発泡体の平均気孔径は2-5mm程度、かさ密度は0.07g/cm3となり、実施例１と比較して粗い気孔径となるが、界面活性剤を使用しないで発泡体を得ることが可能である。
なお、アセタール化（ホルマール化）やその他の架橋剤により通常に架橋したポリビニルアルコール系発泡体は、80〜85℃程度での温水中で再溶解しないが、本発明の実施例の発泡体は、80〜85℃程度での温水中で再溶解するため、ポリビニルアルコールが本来的に具備する生分解性を依然として保持していると考えられる。
(Example 3)
An 8 wt% aqueous solution of polyvinyl alcohol (Nippon Synthetic Chemical NH-26) is cooled to 5 ° C and mixed with calcined diatomaceous earth soaked in foaming agent normal pentane for 3 hours. The mixing ratio is 20 g of diatomaceous earth solid content per 100 ml of polyvinyl alcohol. Diatomaceous earth has voids, and normal pentane is soaked in it. The mixed solution is put into a container of any shape and frozen in a freezer. The freezing temperature was -10 ° C. Hold in the frozen state for 24 hours, and then thaw at room temperature. The solution gels and maintains its shape when frozen. This gelled solution is heated in a constant temperature bath at 60 ° C. and foamed. At the time of foaming, the gelled body expands at a foaming ratio of 8 to 10 times by volume, but is dried to obtain a foamed body. The average pore diameter of the foam is about 2-5 mm and the bulk density is 0.07 g / cm 3 , which is a coarse pore diameter compared to Example 1, but it is possible to obtain a foam without using a surfactant. It is.
In addition, although the polyvinyl alcohol-type foam normally bridge | crosslinked with the acetalization (formalization) and other crosslinking agents does not re-dissolve in warm water at about 80-85 degreeC, the foam of the Example of this invention, It is considered that the biodegradability inherently possessed by polyvinyl alcohol is still retained because it is redissolved in warm water at about 80 to 85 ° C.
本発明の作製方法により作製されたポリビニルアルコール系発泡体は、生分解性を具備するものであり、緩衝材などに用いて、廃棄物処理の問題を解消することができる。また、ポリビニルアルコールを分解しうる微生物、菌体等を予め含有させておけば、生分解処理が一層促進されることが想定される。さらに、本発明のポリビニルアルコール系発泡体は、常温や60℃程度未満の温度において耐水性を具備するし、また、適度に空隙度を高め、適度に大きな空孔も形成できるので、含水ゲルの状態として廃水処理用担体、バイオリアクター用担体、フィルター等にも使用しうる。固形成分として研磨砥粒を混入させた発泡体については、そのままで研磨材とすることもできるし、また、シート状にスライスすることにより研磨布とすることもできる。 The polyvinyl alcohol-based foam produced by the production method of the present invention has biodegradability and can be used as a cushioning material to solve the problem of waste disposal. Moreover, it is assumed that the biodegradation process is further promoted by previously containing microorganisms, fungus bodies and the like that can decompose polyvinyl alcohol. Furthermore, the polyvinyl alcohol-based foam of the present invention has water resistance at room temperature or a temperature of less than about 60 ° C., and also has a moderately high porosity and can form moderately large pores. It can also be used as a wastewater treatment carrier, bioreactor carrier, filter and the like. The foam in which abrasive grains are mixed as a solid component can be used as an abrasive as it is, or can be made into a polishing cloth by slicing it into a sheet.
Claims (5)
（Ａ）ポリビニルアルコール単独又はポリビニルアルコールを主成分とする樹脂、及び、発泡剤を含み、焼結される金属粉末、焼結されるセラミックス粉末を含まない水溶液を準備する工程
（Ｂ）該水溶液を凍結ゲル化し、ゲル化物を得る工程
（Ｃ）凍結ゲル化したゲル化物を解凍する工程
（Ｄ）解凍したゲル化物を該ポリビニルアルコールの溶解温度未満の温度で発泡させる工程 The manufacturing method of the polyvinyl alcohol-type foam characterized by including the process of following (A)-(D).
(A) A step of preparing an aqueous solution containing polyvinyl alcohol alone or a resin containing polyvinyl alcohol as a main component and a foaming agent and containing no sintered metal powder and no sintered ceramic powder (B) Step of freeze-gelating to obtain gelled product (C) Step of thawing freeze-gelled gelled product (D) Step of foaming thawed gelled product at a temperature lower than the melting temperature of the polyvinyl alcohol
（Ｅ）発泡後のゲル化物を乾燥させる工程 Furthermore, the process of the following (E) is included, The manufacturing method of the polyvinyl alcohol-type foam of Claim 1 characterized by the above-mentioned.
(E) A step of drying the gelled product after foaming
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103030909A (en) * | 2012-12-28 | 2013-04-10 | 上海金树树脂粉末有限公司 | Expanded polyvinyl alcohol and preparation method thereof |
| CN110183804A (en) * | 2019-06-14 | 2019-08-30 | 西安工程大学 | A kind of polyvinyl alcohol foam material and preparation method thereof |
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| JP2003170183A (en) * | 2001-12-05 | 2003-06-17 | Takeda Chem Ind Ltd | Carrier for water treatment, method for manufacturing the same and apparatus for water treatment |
| JP3858096B2 (en) * | 2003-07-09 | 2006-12-13 | 独立行政法人産業技術総合研究所 | Method for producing foam sintered body containing metal or ceramics |
| JP2009102701A (en) * | 2007-10-24 | 2009-05-14 | Mitsubishi Materials Corp | Method for manufacturing porous sintered body of titanium and apparatus for manufacturing porous sintered body of titanium |
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| JPH06245874A (en) * | 1993-02-22 | 1994-09-06 | Wakayama Pref Gov | Washing tool |
| JP2003170183A (en) * | 2001-12-05 | 2003-06-17 | Takeda Chem Ind Ltd | Carrier for water treatment, method for manufacturing the same and apparatus for water treatment |
| JP3858096B2 (en) * | 2003-07-09 | 2006-12-13 | 独立行政法人産業技術総合研究所 | Method for producing foam sintered body containing metal or ceramics |
| JP2009102701A (en) * | 2007-10-24 | 2009-05-14 | Mitsubishi Materials Corp | Method for manufacturing porous sintered body of titanium and apparatus for manufacturing porous sintered body of titanium |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103030909A (en) * | 2012-12-28 | 2013-04-10 | 上海金树树脂粉末有限公司 | Expanded polyvinyl alcohol and preparation method thereof |
| CN110183804A (en) * | 2019-06-14 | 2019-08-30 | 西安工程大学 | A kind of polyvinyl alcohol foam material and preparation method thereof |
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