WO2003093361A1 - Film entierement biodegrabable et son procede de preparation - Google Patents

Film entierement biodegrabable et son procede de preparation Download PDF

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Publication number
WO2003093361A1
WO2003093361A1 PCT/CN2003/000306 CN0300306W WO03093361A1 WO 2003093361 A1 WO2003093361 A1 WO 2003093361A1 CN 0300306 W CN0300306 W CN 0300306W WO 03093361 A1 WO03093361 A1 WO 03093361A1
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Prior art keywords
starch
hydrosol
water
hydrolysate
film
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PCT/CN2003/000306
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English (en)
French (fr)
Inventor
Yongping Liu
Huiwen Ma
Yong Fang
Original Assignee
Wuhan Jinbao Environmental Biotechnology Co., Ltd.
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Priority to AU2003236166A priority Critical patent/AU2003236166A1/en
Publication of WO2003093361A1 publication Critical patent/WO2003093361A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08L3/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
    • C08L29/02—Homopolymers or copolymers of unsaturated alcohols
    • C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2303/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08J2303/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2201/00—Properties
    • C08L2201/06—Biodegradable
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L5/00—Compositions of polysaccharides or of their derivatives not provided for in groups C08L1/00 or C08L3/00

Definitions

  • the present invention relates to a substitute for a chemical plastic film, in particular to a bio-degradable film and a preparation method thereof. Background technique
  • Some researchers have designed the use of polyethylene, modified starch, and photosensitive materials as fillers to produce semi-degradable films to take advantage of the biodegradable properties of components such as modified starch to accelerate film decay and decomposition.
  • the polyethylene in this film is not biodegradable, the white pollution caused by its residue cannot be eradicated, so the use of this semi-degradable film is also Has been greatly restricted.
  • Some scientific research units choose to mix modified starch with polyvinyl alcohol to produce a degradable film based on a mixture of modified starch and polyvinyl alcohol, but in the production process, the starch raw material and the polyvinyl alcohol raw material are easily separated.
  • the purpose of the present invention is to overcome the shortcomings in the prior art, and provide a biodegradable film and a preparation method thereof, so that the film prepared by the method not only has various excellent properties of chemical plastic films, but also can be used by the soil.
  • the microorganisms in it are completely decomposed and absorbed quickly, and the production cost is extremely low.
  • the biodegradable film of the present invention contains 5 to 80% starch hydrolysate, 0.2 to 3% natural gum hydrolysate, 8 to 85% polyvinyl alcohol, and 0.2 to 0.3% by weight.
  • Cross-linking agent and 8-14% water wherein the starch hydrolysate and natural gum hydrolysate are obtained by mixing starch, natural gum and water separately or mixing starch, natural gum and water together in polysaccharides.
  • Hydrolysis was performed under the action of enzymes until the viscosity of the hydrolysate was detected to be 24-26 Pa * S under the conditions of sampling, and an incomplete hydrolysate was obtained, wherein the ratio of starch and natural rubber was 5 to 80: 0.2 to 3.
  • the method for preparing the above biodegradable film includes the following steps:
  • the mixed sol is cast into a film by dry casting, and then dried, stretched, and heat-set, so that the final water content is 8 to 14% of the weight of the film.
  • starch hydrolysate in the present invention refers to an incomplete hydrolysate formed by incomplete hydrolysis of starch under the action of a polysaccharide enzyme.
  • the "incomplete hydrolysate” herein is an oligosaccharide as a main component, preferably 70 ⁇ 75% mixture.
  • various forms of plant-derived starches can be listed, such as corn starch, wheat starch, potato starch, cassava starch, and the like, and there is no particular limitation on them. From the viewpoint of cost reduction, corn or wheat starch is preferred.
  • the hydrolysis of the starch of the present invention is performed in the presence of a catalyst.
  • the catalysts here include acids, bases and biocatalysts, ie enzymes.
  • the catalyst is selected on the condition that it can act on ⁇ -1,4-glycosidic bonds on the main chain of polysaccharides, including starch, preferably enzymes, more preferably polysaccharide enzymes, and still more preferably various enzymes commonly used in the art for starch hydrolysis, such as ⁇ -amylase, ⁇ -glucoamylase, dextrose enzyme and saccharifying enzyme, etc.
  • the control of hydrolysis conditions is affected by factors such as the enzyme used, temperature, etc.
  • ⁇ -amylase is hydrolyzed at 95 ⁇ 100 ° C; p-glucoamylase and saccharifying enzyme are hydrolyzed at 60 ⁇ 65 ⁇ ; dextranase is 37-45 ° C hydrolysis.
  • the starch hydrolysate of the present invention has a much smaller molecular structure and a much higher molecular size equilibrium than the non-hydrolyzed high molecular weight starch, which is very conducive to cross-linking with the auxiliary material polyvinyl alcohol, and overcomes the direct film brittleness of starch Insufficient transparency.
  • the content of the starch hydrolysate in the biodegradable film of the present invention is 5 to 80%, preferably 50 to 80%, and more preferably 70 to 75%.
  • the "natural gum hydrolysate” of the present invention includes an incomplete hydrolysate obtained by incomplete hydrolysis using a natural gum as a raw material under the action of a polysaccharide enzyme.
  • the "incomplete hydrolysate” here is also a mixture of a series of oligosaccharides such as disaccharides.
  • Natural rubber as a raw material of the present invention It is a plant-derived natural polysaccharide, and is not particularly limited in the present invention.
  • Various products well known in the art can be used, such as carrageenan, sodium alginate, xanthan gum, and the like.
  • the "catalyst” used here can be the same catalyst used in the above hydrolysis of starch.
  • natural gum itself is hydrophilic, its hydrolysate is used as an additive to enhance water retention in the present invention.
  • the natural gum hydrolysate has a good synergy with the starch hydrolysate during the film formation process, and can also promote the improvement of the mechanical strength of the film formation
  • the content of the natural gum hydrolysate in the biodegradable film of the present invention is 0.2 to 3%, preferably 0.5 to 2.5%, and more preferably 1 to 2%.
  • the polyvinyl alcohol in the present invention has good hydrogel forming ability, and crosslinking with starch hydrolysate can enhance the mechanical strength of the film formation and improve the heat-sealing performance of the film formation. Because polyvinyl alcohol has good water solubility and is 100% biodegradable, it is an important main component in biodegradable films.
  • the degree of polymerization of polyvinyl alcohol in the present invention is not particularly limited. From the viewpoint of improving the strength of the film, polyvinyl alcohol having a polymerization degree of 1700 to 2200 is preferred, and polyvinyl alcohol having a polymerization degree of 2200 is more preferred.
  • the content of polyvinyl alcohol in the biodegradable film is 8 to 85%, preferably 17 to 37%.
  • the crosslinking agent in the present invention is a hydrocarbon compound containing two aldehyde groups or capable of being converted into two aldehyde groups under water environment conditions.
  • the crosslinking agent which can be used is preferably glutaraldehyde or glyoxal or propylene oxide.
  • the content of the cross-linking agent in the biodegradable film is 0.2 to 0.3%.
  • the cross-linking agent can firmly cross-link the starch hydrolysate and natural gum hydrolysate with polyvinyl alcohol to form a three-dimensional network structure, which avoids the defect of easy phase separation after mixing the above hydrolysate and polyvinyl alcohol, so that the formed
  • the thin film not only has a uniform material distribution, but also its mechanical strength can be greatly improved.
  • the bio-degradable film of the present invention must contain a certain amount of water, and generally 8 to 14% is suitable. When it is less than 8%, the formed film is easily brittle and aged. When it is higher than 14%, the breaking elongation of the resulting film is very large, the size is unstable, and it is difficult to meet the requirements for use.
  • total degradation in the present invention is that the composition of the film can be Utilized by microorganisms, it is finally decomposed into carbon dioxide and water.
  • the bio-degradable film of the present invention is prepared by the following method:
  • the above oligosaccharide hydrosol and polyvinyl alcohol aqueous solution are preferably mixed uniformly in a weight ratio of 2-3: 1-1.5, and an appropriate amount of a cross-linking agent is added to knead to form a mixed sol; wherein the preferred amount of the cross-linking agent is It is 2 to 3%.
  • the mixed sol is formed into a film by a casting method, preferably a dry casting method, and then dried, stretched, and heat-set, so that the final water content is 8 to 14% by weight of the film weight.
  • a polysaccharide enzyme preferably an ⁇ -amylase
  • hydrolysis In order to obtain the incomplete hydrolysis product required by the present invention, it is very important to control the hydrolysis conditions and thus the degree of hydrolysis. Generally speaking, the degree of hydrolysis is affected by conditions such as temperature and time. When the viscosity of the hydrolyzed solution was measured under the condition of 351 to measure 24 to 26 Pa'S, preferably 26 Pa-S, at this time, the polysaccharide was hydrolyzed to an oligosaccharide, and the hydrolysis reaction was terminated to obtain an incompletely hydrolyzed oligosaccharide hydrosol.
  • the film is rolled onto a reel, pressed into a roll, and packaged to obtain a finished product.
  • the endless stainless steel strip should be treated with a silicide before being put into use.
  • the specific processing method is as follows: After the endless stainless steel belt of the film forming machine is installed in the film forming machine, a commercially available silicidation liquid is horizontally painted on the surface of the steel belt with a plate brush having a width of 10 cm. 10 cm, ready to use after drying under 100. In this way, the thin film formed on the stainless steel strip can be used under certain stretching of the steel strip, and can be easily peeled off from it, which can optimize the film quality.
  • natural polysaccharides such as corn or wheat starch, which have a large output, are inexpensive, and are easily available, can be selected as the hydrolysis raw material, which can greatly reduce the production cost of the film.
  • the low-temperature and high-temperature-resistant ⁇ -amylase is used to incompletely hydrolyze the raw materials.
  • the hydrolysis process is easy to control, and it is easy to obtain a oligosaccharide hydrolysate with a relatively balanced molecular weight.
  • the film formation quality is intact, and the production cost is further reduced.
  • the choice of different cross-linking agents such as glutaraldehyde can meet the needs of different fields such as food packaging and agricultural mulch. detailed description
  • the mixed sol was degassed under reduced pressure, and then cast by a lip spray, and then coated on a siliconized smooth endless stainless steel film forming machine, and dried by hot air at 80 t! To form a film. After the film is removed, it is then subjected to a horizontal and vertical biaxial stretching treatment, and is rapidly and dry-set at a temperature of 1501 :, so that its final moisture content is about 12% of the weight of the film.
  • the biodegradable film thus obtained contained 69.703% of wheat starch hydrolysate, 0.871% of carrageenan hydrolysate, 0.232% of glutaridine, 17.425% of polyvinyl alcohol, and 11.769% of water by weight.
  • Example 1 Except that the raw material starch in Example 1 was changed to corn starch, the natural gum was changed to sodium alginate, and the cross-linking agent was changed to glyoxal. The operation was the same as that in Example 1. When drying, the water content of the film accounted for the weight of the film. 8%.
  • the obtained biodegradable film contained 70% of corn starch hydrolysate, 3% of sodium alginate hydrolysate, 0.245% of glyoxal, 18.755% of polyvinyl alcohol, and 8% of water by weight.
  • Example 1 Except that the natural rubber in Example 1 was changed to xanthan gum and the cross-linking agent was changed to propylene oxide, the rest of the raw materials and operations were the same as in Example 1, and the moisture content of the film was 10% of the film weight when dried.
  • the obtained biodegradable film contains 35% wheat starch hydrolysate, 0.75% xanthan gum hydrolysate, 0.235% propylene oxide, 54.015% polyvinyl alcohol, and 10% water by weight .
  • the mixed sol was degassed under reduced pressure, measured and sprayed through a lip, cast on a smooth and endless stainless steel film forming machine, and the hot air was blown to dry the film to control the water content of the film to 18%. After the film is removed, the film is stretched longitudinally and bidirectionally. After 150 minutes of heat setting, it is rapidly air-cooled to control its final moisture content to 11%.

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
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Description

生物全降解薄膜及其制备方法 技术领域
本发明涉及一种化学塑料薄膜的替代品，具体地指一种生物全降 解薄膜及其制备方法。 背景技术
化学塑料的诞生曾被誉为二十世纪的一次革命，但它的广泛应用 也形成了公认的白色污染。 研究表明： 化学塑料废弃物在自然环境 中经过七十年都难以降解， 这给江河湖泊和陆地造成了严重的污染， 对自然环境造成了极大的危害。 如废弃的农用化学塑料薄膜年复一 年地积累在田间， 可破坏农作物土壤的结构， 影响农作物根系的发 育， 造成农作物大幅减产。 经测试农田连续五年使用化学塑料地膜， 每亩农田中残留的地膜塑料废渣将达二十公斤以上， 可造成农作物 減产百分之十二左右。 为了解决上迷化学塑料薄膜的污染问题， 人 们一直在努力寻找能有效取代它的替代品。
有些科学工作者基于以纤维素为主要生产原料的纸制品在自然 界中可完全被微生物降解的原理， 曾设想用纸张制品来代替化学塑 料薄膜制品。 然而纸张的生产要消耗大量的木材， 导致森林大面积 被砍伐， 造成生态环境的恶化； 纸张的生产也会产生大量的有机废 水， 污染江河湖海。 而且纸张的强度低， 造价高， 特别是透光性太 差， 用其代替化学塑料薄膜满足不了用途和数量方面的要求。
也有些研究人员设计用聚乙烯、改性淀粉和光敏物质作填充料来 生产半降解薄膜， 以利用改性淀粉等組份的生物降解特性来加快薄 膜的腐烂和分解。 但由于这种薄膜中的聚乙烯不会被生物降解， 其 残留所造成的白色污染仍不能根除， 因而这种半降解薄膜的使用也 受到了很大的限制。还有些科研单位选用改性淀粉与聚乙烯醇混炼， 制作出以改性淀粉和聚乙烯醇混合物为主料的可降解薄膜， 但在生 产过程中淀粉原料和聚乙烯醇原料两者易分相， 使得此类薄膜成品 率较低， 质量也很不稳定， 且其机械力学强度较差， 往往达不到实 用的要求。 而美、 欧等国家先利用人工培菌的方法生产高分子化合 物如黄原胶、 聚 β -羟基丁酸等， 再利用这些高分子化合物来小批 量生产生物全降解薄膜。 这种方法虽然可以做到根除白色污染， 但 其投资额巨大、 生产成本昂贵， 难以适应大规模生产的需求。 发明内容
本发明的目的就是要克服现有技术中存在的不足,提供一种生物 全降解薄膜及其制备方法， 使得用该方法制备出的薄膜既具有化学 塑料薄膜的各种优良性能， 又能被土壤中的微生物完全分解快速吸 收， 同时其制作成本极为低廉。
为实现此目的，本发明的生物全降解薄膜，按重量计算，含有 5 ~ 80 %的淀粉水解产物、 0.2 ~ 3 %的天然胶水解产物、 8 ~ 85%的聚乙 烯醇、 0.2 ~ 0.3%的交联剂以及 8 ~ 14%的水份， 其中所述淀粉水解 产物和天然胶水解产物是通过将淀粉、 天然胶分别和水混合后或者 淀粉、 天然胶和水三者一起混合后在多糖酶作用下进行水解直至当 取样在 的条件下检测水解液的粘度达 24〜26Pa*S, 得到不完全 水解产物， 其中淀粉、 天然胶的比例为 5 ~ 80： 0.2 ~ 3。
上述生物全降解薄膜的制备方法， 包括如下步骤：
1 )将淀粉、 天然胶和水混合均匀， 加入多糖酶进行水解， 得到 2-20残糖基组成的寡糖水溶胶；
2 )将聚合度为 500〜2200 的聚乙烯醇和水混合， 水浴溶解， 得 到聚乙烯醇水溶胶； 3 )将上述寡糖水溶胶和聚乙烯醇水溶液混合均勾， 加入交联剂 混炼， 形成混合溶胶；
4 )将上述混合溶胶通过干法流延成膜， 再经过干燥、 拉伸和热 定型处理， 使其最终含水量为膜重量的 8 ~ 14%。
下面对本发明的薄膜进行具体说明。
本发明的 "淀粉水解产物"是指淀粉在多糖酶作用下发生不完全 水解所形成的不完全水解产物， 在本发明中， 这里的 "不完全水解 产物"是以寡糖为主要成分， 优选 70〜75%的混合物。 作为原料的淀 粉， 可以列出各种形式的来源于植物的淀粉， 例如玉米淀粉， 小麦 淀粉， 马铃薯淀粉， 木薯淀粉等， 对其没有特别的限制。 从降低成 本的角度看， 优选玉米或小麦淀粉。 本发明的淀粉的水解在催化剂 存在下进行。 这里的催化剂包括酸， 碱以及生物催化剂即酶等。 催 化剂的选择以能作用于多糖包括淀粉主链上的 α - 1, 4 -糖苷键为 条件， 优选酶， 更优选多糖酶， 进一步更优选本领域中通常用于淀 粉水解的各种酶， 例如 α -淀粉酶， β -葡糖淀粉酶， 右旋糖香酶 和糖化酶等。 水解条件的控制受到所使用的酶， 温度等因素的影响， 例如， α -淀粉酶在 95〜100°C水解； p -葡糖淀粉酶和糖化酶在 60~65υ水解； 右旋糖苷酶在 37-45Ό水解。
本发明的淀粉水解产物具有比未经水解的高分子量淀粉小得多 的分子结构和高得多的分子大小均衡度， 非常有利于与辅料聚乙烯 醇交联， 克服了淀粉直接成膜脆性大、 透明度低的不足。
本发明的淀粉水解产物在生物全降解薄膜中的含量为 5 ~ 80% , 优选 50〜80%, 更优选 70~75%。
本发明的"天然胶水解产物"包括以天然胶为原料在多糖酶作用 下进行不完全水解得到的不完全水解产物。 这里的 "不完全水解产 物"也是一系列寡糖如二糖的混合物。 作为本发明的原料的天然胶， 是来自植物的天然多糖， 在本发明中没有特别的限制， 可以使用本 领域中熟知的各种产品， 例如卡拉胶， 海藻酸钠， 黄原胶等。 这里 的 "催化剂" 可以使用与上面淀粉水解使用的同样的催化剂。 由于 天然胶本身具有亲水性， 所以其水解产物在本发明中用作增强保水 性的添加剂。 另外， 天然胶水解产物在成膜过程中与淀粉水解产物 具有良好的协同作用， 也可促进成膜机械力学强度的提高
本发明的天然胶水解产物在生物全降解薄膜中的含量为 0.2 ~ 3 % , 优选 0.5〜2.5%, 更优选 1〜2%。
本发明中的聚乙烯醇具有良好的水成胶能力，与淀粉水解产物交 联可增强成膜的机械强度， 提高成膜的热封性能。 由于聚乙烯醇具 有良好的水溶性， 并且 100%生物降解，是生物全降解薄膜中很重要 的一种主体成分。 本发明中的聚乙烯醇的聚合度没有特别的限定， 从提高薄膜强度的角度看， 优选聚合度为 1700〜2200的聚乙烯醇， 更优选聚合度为 2200的聚乙烯醇。 聚乙烯醇在生物全降解薄膜中的 含量为 8 ~ 85 % , 优选 17〜37%。
本发明中的交联剂是含有两个醛基或在水环境条件下能转变成 两个醛基的碳氢化合物。 可以使用的交联剂优选戊二醛或乙二醛或 环氧丙烷。 交联剂在生物全降解薄膜中的含量为 0.2 ~ 0.3%。 交联剂 可将淀粉水解产物和天然胶水解产物与聚乙烯醇牢固地交联在一 起， 形成立体网状结构， 避免了上述水解产物与聚乙烯醇混合后易 分相的缺陷， 使得所形成的薄膜不仅材料分布均匀， 而且其机械力 学强度也可大幅提高。
本发明的生物全降解薄膜中必须含有一定量的水分，一般以 8 ~ 14 %为宜。 低于 8%时， 所成薄膜易脆裂老化。 高于 14%时， 所成 薄膜断裂伸长率很大， 尺寸不稳定， 难以符合使用要求。
本发明中的 "全降解"含义是薄膜的組成成分在自然条件下能被 微生物利用， 最终分解成二氧化碳和水。
下面详细描述本发明生物全降解薄膜的制备方法。
本发明的生物全降解薄膜用如下方法制备：
1 ) 按比例将淀粉、 天然胶和水混合均匀或者将淀粉、 天然 胶分别与水混合后， 加入多糖鲦进行水解， 得到寡糖水 溶胶； 其中， 所迷淀粉、 天然胶和水的比例优选为 10-40:0.2-3： 57-89.8, 更优选为 25〜35:1〜2： 67-74, 所 述多糖酶的用量优选为每千克淀粉 10000-15000酶活单 位。
2 )将聚乙烯醇和适量的水混合， 水浴溶解， 得到聚乙烯醇含量 优选为 15〜50%的聚乙烯醇水溶胶；
3 )将上述寡糖水溶胶和聚乙烯醇水溶液优选按 2-3： 1-1.5的重 量比混合均匀， 加入适量的交联剂混炼， 形成混合溶胶； 其中， 所 述交联剂的优选用量为 2〜3%。
4 )将上述混合溶胶通过流延法成膜， 优选干法流延成膜， 再经 过干燥、 拉伸和热定型处理， 使其最终含水量为膜重量的 8 ~ 14重 量％。
其中， 在步骤 1 ) 中使用多糖酶， 优选 α -淀粉酶进行水解。 为 了得到本发明所需的不完全水解产物 , 控制水解条件从而控制水解 程度非常重要的。 一般来讲， 水解程度受到温度， 时间等条件的影 响。 当取样在 351的条件下检测水解液的粘度达 24〜26Pa'S ， 优选 26Pa-S时， 此时， 多糖被水解成寡糖， 终止水解反应， 得到不完全 水解的寡糖水溶胶。
根据薄膜用途的差异，可以选择在薄膜上喷涂聚丁酸丁二酯或食 用蜡等方法进行表面处理， 以增加薄膜的防水防潮能力。 最后， 将 薄膜卷入卷轴上， 压辊， 包装即得成品。 为了使薄膜在干燥后容易从成膜机上的无端不锈钢带上剥离下 来， 无端不锈钢带在投入使用前应采用硅化剂处理。 具体处理方法 如下： 将成膜机的无端不锈钢带安装入成膜机后， 用宽度为 10厘米 的板刷将市售的硅化液横向涂刷在钢带表面， 涂刷方式为每 10厘米 宽间隔 10厘米， 在 lOO 下烘干即可使用。 这样不锈钢带上所形成 的薄膜既可受到钢带一定的拉伸使用， 又容易从其上剥离下来， 可 优化成膜质量。
根据本发明， 可以选择玉米或小麦淀粉等产量巨大、 价格低廉、 易于获得的天然多糖作为水解原料， 可以大幅降低薄膜的生产成本。 选择价格低廉而且耐高温的 α -淀粉酶对原料进行不完全水解， 水 解过程易于控制， 容易获得分子量大小较为均衡的寡糖水解产物 , 不会发生水解控制不当而形成单糖的问题， 可确保成膜质量完好， 生产成本进一步降低。 而选择戊二醛等不同的交联剂可以适应薄膜 用于食品包装、 农用地膜等不同领域的需要。 具体实施方式
以下结合具体实施例对本发明作进一步的详细描迷。
实施例 1
取小麦淀粉 5000克， 卡拉胶 60克， 与 10升的水混合均匀， 再 加入 4亳升 a -淀粉酶（活力单位为 20000u/ml ), 在 90~95" 的温 度下进行水解 75分钟左右。
当取样在 的条件下检测水解液的粘度达 26Pa.S时， 升温至 100X 中止水解反应， 并通过 200目网筛过滤， 得到不完全水解的寡 糖水溶胶。
将 1200克的聚乙烯醇（聚合度为 2200 )和 8升水混合， lOOt; 水浴溶解， 得到聚乙烯醇水溶胶。 将上述不完全水解的寡糖水溶胶和聚乙烯醇水溶胶混合均勾，加 入 16亳升戊二 溶液， 在 40°C的温度下保温交联 24小时， 形成混 合溶胶。
将上述混合溶胶减压脱泡后， 通过喷唇流延，涂布在经硅化处理 过的光洁无端不锈钢带成膜机上， 在 80t!的温度下热风干燥成膜。 脱膜后再经纵横双向拉伸处理， 在 1501：的温度下快速干热定型，使 其最终含水量约为膜重量的 12 %。
这样得到的生物全降解薄膜，按重量计算，含有 69.703 %的小麦 淀粉水解产物、 0.871%的卡拉胶水解产物、 0.232%的戊二窿、 17.425%的聚乙烯醇以及 11.769 %的水份。
实施例 2
除了将实施例 1中的原料淀粉改成玉米淀粉，天然胶改成海藻酸 钠， 交联剂改成乙二醛以外， 操作与实施例 1 同样， 干燥时使薄膜 的含水量占膜重的 8%。得到的生物全降解薄膜， 其按重量计算， 含 有 70 %的玉米淀粉水解产物、 3 %的海藻酸钠水解产物、 0.245%的 乙二醛、 18.755%的聚乙烯醇以及 8 %的水份。
实施例 3
除了将实施例 1中的天然胶改成黄原胶，交联剂改成环氧丙烷以 外， 其余原料及操作与实施例 1 同样， 干燥时使薄膜的含水量占膜 重的 10%。 得到的生物全降解薄膜， 其按重量计算， 含有 35%的小 麦淀粉水解产物、 0.75%的黄原胶水解产物、 0.235%的环氧丙烷、 54.015%的聚乙烯醇以及 10 %的水份组成。
实施例 4
在 1000克玉米淀粉中， 加入 50克卡拉胶， 混合均匀， 加入含有 8000活性单位的糖化酶水溶液 6500亳升， 搅拌混勾， 在 60"C的温 度下进行水解，控制水解时间为 90分钟，得到粘稠糖浆状胶体溶液。 该胶体溶液经 200目网筛过滤， 除去其中的杂质， 得到寡糖水溶胶。 其次在 450克聚乙烯醇中加入 3600亳升水， lOO 水浴， 直至聚 乙烯醇完全溶解， 得到辅料聚乙埽醇水溶胶。
然后将上述主料多糖水溶胶与辅料聚乙烯醇水溶胶充分混合,冷 却至 40 ，加入 8亳升重量体积比为 50 %的戊二酪溶液，混合均匀， 40 Ό保温 24小时， 得到混合溶胶。
再将混合溶胶減压脱泡， 经喷唇计量喷出， 流延在光洁的无端不 锈钢带成膜机上， 鼓入 的热风干燥成膜， 使成膜的含水量控制 在 18 %。 脱膜后经纵横双向拉伸， 150 热定型片刻后快速风冷， 使 其最终含水量控制在 11 %。
本发明的生物全降解薄膜的生物降解度的测定
按照 ASTM G21 - 70标准， 分别测定实施例 1-4得到的薄膜的 生物降解度， 结果表明， 薄膜的生物降解度均超过 98%。

Claims

权 利 要 求
1. 一种生物全降解薄膜，按重量计算，含有 5 ~ 80 %的淀粉水解产物、 0.2 ~ 3 %的天然胶水解产物、 8 ~ 85%的聚乙烯醇、 0·2 ~ 0·3%的交联剂以
8 ~ 14%的水份，其中所述淀粉水解产物和天然胶水解产物是通过将淀 粉、 天然胶分别和水混合后或者将淀粉、 天然胶和水三者一起混合后在 多糖酶作用下进行水解直至当取样在 35υ的条件下检测水解液的粘度达 24~26Pa S而得到的不完全水解产物，其中淀粉、天然胶的用量比例为 5 ~ 80: 0.2 ~ 3。
2. 根据权利要求 1所述的生物全降解薄膜， 其特征在于： 所说的多 糖酶是 α -淀粉酶。
3. 根据权利要求 1或 2所述的生物全降解薄膜， 其特征在于： 所说 的淀粉水解产物的原料选用玉米淀粉或小麦淀粉或马铃薯淀粉或木薯淀 粉， 所说的天然胶水解产物的原料选用卡拉胶或海藻酸钠或黄原胶。
4. 根据权利要求 1或 2所述的生物全降解薄膜， 其特征在于： 所说 的交联剂选用戊二醛或乙二醛或环氧丙烷。
5. 根据权利要求 3所述的生物全降解薄膜， 其特征在于： 所说的交 联剂选用戊二醛或乙二醛或环氧丙烷。
6. 一种权利要求 1所述生物全降解薄膜的制备方法， 包括如下步骤：
1 )将淀粉、 天然胶和水混合均匀或将淀粉、 天然胶分别和水混合后， 加入多糖皞进行水解， 得到寡糖水溶胶；
2 )将聚乙烯醇和水混合， 水浴溶解， 得到聚乙烯醇水溶胶；
3 )将上述寡糖水溶胶和聚乙烯醇水溶胶混合均匀 , 加入交联剂混炼， 形成混合溶胶；
4 )将上述混合溶胶通过流延法成膜， 再经过干燥、 拉伸和热定型处 理， 使其最终含水量为膜重量的 8 ~ 14%。
7. 根据权利要求 6所迷的生物全降解薄膜的制备方法， 其特征在于： 所说的步骤 1 ) 中选用 α -淀粉酶进行水解， 当取样在 35t;的条件下检 测水解液的粘度达 26Pa'S时终止水解反应， 得到不完全水解的多糖水溶 胶。
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CN101585932B (zh) * 2008-05-22 2013-04-17 深圳市环之源生物科技有限公司 全生物降解包装膜及其制备方法
CN101914223B (zh) * 2010-08-06 2012-01-25 西北师范大学 改性淀粉-聚乙烯醇基复合塑料薄膜的制备方法
CN103554553B (zh) * 2013-10-25 2016-01-13 中南林业科技大学 一种大米淀粉基可生物降解包装膜及其制备方法
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CN106084310A (zh) * 2016-06-22 2016-11-09 福州大学 基于海藻多糖的可生物降解塑料及其制备方法
CN108219330A (zh) * 2017-12-30 2018-06-29 姜向军 一种可降解地膜
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