CN1357563A - Prepn of biodegradable film of ternary starch-PVA-polyester system material - Google Patents

Abstract

The ternary biodegradable film is prepared by using the material including starch, PVA, polyester, mixed plasticizer, reinforcing agent and wet strength agent, and through mixing to react, pelletizing and blowing to film with the polyester being selected from polycarbonate, polycaprolactone, polyvinyl acrylate, poly-beta-hydroxy butyrate and ethylene-acrylic acid copolymer. The film has a tensile strength of 16-24 MPa, breaking elongation of 140-200% and Young's modulus of 130-400 MPa and may be degraded fastly. It is used in shopping bag, garbage bag and packing bag as well as mulching film.

Description

Preparation method of starch-polyvinyl alcohol-polyester ternary system biodegradable film

Technical Field: The present invention relates to a fully biodegradable film and a method for blowing it into a film using an electromagnetic dynamic extruder or a common blow molding machine.

Background technology: When people are looking for degradable mulch and packaging materials to save the increasingly serious "white pollution" caused by non-degradable plastic waste such as polyethylene, the initial attempt is to use biodegradable starch and organic acids or The esters are incorporated into conventional polyethylene films or by photo-oxidation for this purpose. Because no matter it is photodegradation, biodegradation or photo/biodegradation, it is an oxidation process, which eventually turns into acid or ester and decomposes into CO2 and water to return to nature. Therefore, polyethylene/starch type, starch-polyethylene acrylic acid-polyethylene type degradable film and photodegradable film have come out one after another. However, it was found that this type of film can only be degraded by starch and polyethylene cannot be decomposed by microorganisms. Therefore, this type of film has undergone a cooling process and replaced it with the research and development of a series of organic acids or esters, such as Biopol, which is Copolymers of hydroxybutyric acid and hydroxyvaleric acid, such as polylactic acid (PLA), polycaprolactone (PCL), polycarbonate, and polycondensed esters of aliphatic dicarboxylic acids and dihydric alcohols, such as Japan's 'Bionolle ' and so on have come out one after another, and they are indeed very effective. The only downside is that it is too expensive to use for general wrapping materials and mulches.

U.S. F, H, Otey etc. have developed a kind of film of polyvinyl alcohol-starch-polyvinyl chloride type (Ind, Eng, Chem, Prod, Res, Dev, 1980,19,592-595), and this film contains starch 60 %, about 15% polyvinyl alcohol, the polyvinyl chloride sol is coated on the polyvinyl alcohol-starch film to improve the water resistance of the film. The film has little wet strength without a PVC coating, and the introduction of PVC is detrimental to degradation. The biodegradable film (MPI 1991,100,9,P7) prepared by Italian Ferruxxi company using its relative amount of 70% starch and 30% denatured polyvinyl alcohol, called Mater-Bi, has the ability of complete degradation, and The price is relatively low, and it is listed as one of the three most well-known brands of fully biodegradable plastics in the world. The other two are Biopol from the British ICI and Novon from the United States (nearly full starch). However, one of the biggest weaknesses of Mater-Bi is that its temperature resistance, weather resistance and water resistance are not enough, which seriously limits its scope of use. Use under high temperature and high humidity environment.

Summary of the invention: The object of the present invention is to provide a method for preparing a starch-polyvinyl alcohol-polyester ternary system biodegradable film, which overcomes the defects of Mater-Bi in terms of weather resistance, temperature resistance and water resistance, so as to broaden the The scope of use of similar films, and films that can be completely biodegraded in a short period of time, are blown into films by using a new type of electromagnetic dynamic blow molding machine, so that the performance of the film is improved.

The formula of the present invention contains starch, polyvinyl alcohol, polyester, mainly selected polycarbonate, polycaprolactone, polyethylene acrylate, poly β-hydroxybutyrate or ethylene-acrylic acid copolymer, compound plasticizer, Reinforcing agent, wet strength agent, through blending reaction, granulation, blow molding to form film, can also be extruded into film through T-shaped head.

In the present invention, starch and polyvinyl alcohol are used as the main body of the film. Starch is an inducer of biodegradation, and its content in the film can control the degradation time and rate of the film. However, the film strength of pure starch is not enough, polyvinyl alcohol is biodegradable, and can be used as a soil conditioner, and the film strength is also good. However, the starch-polyvinyl alcohol film has poor wet strength and poor water resistance. The introduction of polycarbonate coating, polycaprolactone, polyethylene acrylate, poly-β-hydroxybutyrate or ethylene-acrylic acid copolymer is to improve the film Excellent water resistance, especially the performance of high temperature water resistance. For example, after coating polycarbonate on the starch-polyvinyl alcohol film, it can withstand hot water above 90°C. The ternary compound plasticizer system using ethylene glycol: glycerin: polyester polyol or hydroxyl-containing carboxylate has three major functions, one is plasticizing and lubricating; the other is to improve the weather resistance of the film. The third is to improve the compatibility of the introduced polyester and starch-polyvinyl alcohol system, so that it can accept other polyesters or ethylene-acrylic acid copolymers, polyethylene acrylates, etc. . At the same time, the introduction of reinforcing agent and wet strength agent greatly improves the tensile strength and wet strength of the film, and its tensile strength can reach up to 24Mpa, which is higher than Mater-Bi. The implementation of the above measures makes the starch-polymer Vinyl alcohol film is much improved than Mater-Bi in terms of weather resistance, temperature resistance and water resistance, making it close to the use range of polyethylene film.

The raw material that the present invention selects is by weight percentage:

Starch: 30-65%, Polyvinyl alcohol: 15-40%,

  Polyesters: 0-10%,   Plasticizers: 10-20%,

Reinforcement agent: ≤0.4%, Wet strength agent: 0.5-1.5%,

  Defoamer: ≤0.4%,

Wherein the starch is corn starch, potato starch, sweet potato starch or lotus root starch;

Polyvinyl alcohol is polyvinyl alcohol-1799 or polyvinyl alcohol-1999;

The polyester is polycarbonate, polycaprolactone, polyethylene-acrylate, poly-beta-hydroxybutyrate or ethylene-acrylic acid copolymer;

The plasticizer is ethylene glycol: glycerol: polyester polyol = 1-3: 9-15: 3-6 ternary composite system and water by weight; polyester polyol is ethylene glycol from succinic acid to sebacic acid Glycols, condensed esters of ethylene glycol or lauryl esters;

The reinforcing agent is aluminum potassium sulfate, basic alumina, borax or sodium silicate;

The wet strength agent is β-alkoxy ethyl carboxyl bis(dioctyl pyrophosphate) titanium, ethylene diethylene alkoxy phosphate dioctyl titanium or bisisopropoxy triethanolamine titanate;

The defoamer is tributyl phosphate or silicone oil;

The blow molding machine used in the present invention is a novel electromagnetic dynamic blow molding machine. It has the characteristics of short length-to-diameter ratio and uniform heating, which makes it more suitable for the processing of starch-degradable plastics, and the obtained film is uniform and bright. It can also be processed into film or sheet using T-shaped head.

The prepared film of the present invention has a mechanical property of tensile strength of 16MPa--24MPa, elongation at break of 140-200%; Young's modulus of 130-400MPa; when the starch content of this type of film is about 30%, According to the measurement method of carbon dioxide emission, the biodegradation rate can reach more than 85% in four months, and the film with a starch content of about 60% is tested in the field, and its surface has been completely covered by bacteria and microorganisms in two months. It was eroded and turned black, and it has basically degraded in about half a year.

Mater-Bi generally cannot be used in low temperature, high temperature and high humidity environments other than 0-50 °C and relative humidity outside 30-80%, and the film prepared by the present invention can generally be used on polycarbonate after coating polycarbonate. Vinyl film can be used under the environmental conditions that can be used, and its water resistance, temperature resistance and weather resistance are better than Mater-Bi. The film prepared by the invention can be mainly used as shopping bags, garbage bags and packaging bags, and can also be used as mulching film.

The specific implementation is as follows:

Embodiment 1: Weigh 350 parts of PVA and 500 parts of starch by weight, and stir them evenly in a mixer. Weigh 230 parts of water, add 3 parts of aluminum potassium sulfate, 10 parts of β-alkoxyethyl carboxyl bis(dioctyl pyrophosphate)titanium, and 3 parts of tributyl phosphate into the water, and add this aqueous solution to the mixer under stirring Mix well with starch and PVA. Then weigh 200 parts of a mixture of ethylene glycol, glycerin and dodecyl alcohol ester in a ratio of 2:15:3, add the above-mentioned materials into a mixer under stirring, stir evenly, and stir at high speed for 2 minutes. Pelletization was performed in a single-screw extruder type 45 with an aspect ratio of 25:1. Blow molding into film on electromagnetic dynamic extruder or ordinary blow molding machine. The resulting film was coated with a polycarbonate solution on a coating machine for bag making.

Example 2: Weigh 250 parts of PVA and 580 parts of starch, and stir them evenly in a mixer. Weigh 220 parts of water, add 3 parts of borax, 12 parts of β-alkoxyethyl carboxyl bis(dioctyl pyrophosphate)titanium, and 3 parts of tributyl phosphate into the water, add this aqueous solution into the mixer, and stir with the above materials evenly . Then weigh 180 parts of plasticizers whose ratio of ethylene glycol, glycerin and adipic acid ethylene glycol polyester is 2:12:4, add in the mixer, the material is fully mixed under stirring, and then granulated, Blown into film. Apply the polycarbonate solution on a coater. Its granulation, blow molding and coating process are roughly the same as Example 1. The obtained film is made into bags on a sealing machine with a pressure of 2Kg/ ^cm2 and a temperature of 150-160°C.

Embodiment 3: Weigh 250 parts of PVA and 580 parts of starch, and stir them evenly in a mixer. Then weigh 230 parts of water, add 3 parts of basic alumina, 10 parts of bisisopropoxy triethanolamine titanate, 2 parts of silicone oil into the water, and add the aqueous solution into the mixer. Weigh 180 parts of plasticizers whose ratio of ethylene glycol, glycerin and adipate glycol polyester is 3: 10: 5, add 30 parts of polycaprolactone to it, add in the mixer together, and Stir the material well. Granulation and blow molding process are the same as Example 2.

Example 4: Weigh 250 parts of PVA, 550 parts of starch, stir in a mixer, then weigh 220 parts of water, add 3 parts of borax, 10 parts of diisopropoxy triethanolamine titanate, phosphoric acid 2 parts of tributyl ester, add this aqueous solution into the mixer, weigh 180 parts of plasticizer with the ratio of ethylene glycol, glycerol: dodecyl alcohol of 2:11:5, add ethylene-acrylic acid copolymer 30 parts, add in the mixer together, the material is stirred evenly, granulation and blow molding process are the same as Example 1.

Example 5: Weigh 220 parts of polyvinyl alcohol, 580 parts of starch and place them in a mixer, stir well, weigh 220 parts of water, add 3 parts of alum, 10 parts of dioctyl ethylene glycol phosphate titanium, phosphoric acid Put 2 parts of tributyl ester in water, add it into the mixer under low-speed stirring, weigh 170 parts of the mixed solution of ethylene glycol, glycerin and adipic acid ethylene glycol polyester in a ratio of 3:10:4, Add 60 parts of polyethylene --- acrylate to this plasticizer system. Under stirring, it is added in the mixer, and after the material is stirred evenly, it is granulated and blow-molded. The granulation and blow-molding process is the same as Example 1.

Example 6: Weigh 280 parts of PVA, 520 parts of starch, put them in a mixer, weigh 240 parts of water, add 3 parts of sodium silicate, 12 parts of dioctyl ethylene glycol phosphate titanium, tributyl phosphate 2 parts in water, under low-speed stirring, this aqueous solution was added in the mixer, and ethylene glycol: glycerol: ethylene glycol sebacate ratio was weighed 160 parts of the plasticizer mixed liquid of 5: 6: 5, Add 30 parts of ethylene-acrylic acid copolymer to the plasticizer, put the plasticizer mixture with polyethylene-acrylic acid ester into the mixer, stir the materials evenly, and the granulation and blow molding process are the same as above.

Example 7: Weigh 200 parts of PVA, 620 parts of starch, put them in a mixer, stir well, weigh 220 parts of water, add 3 parts of borax, 10 parts of dioctyl ethylene glycol phosphate titanium, silicone oil 2 parts, add this aqueous solution into the mixer, stir well, weigh 160 parts of the mixed solution of glycerin: ethylene glycol: ethylene adipate glycol polyester ratio of 1: 10: 5, add EVA (VA content is 33%) 50 parts, under stirring, put this mixed solution into the mixer, stir the materials evenly, the process of granulation and film blowing is the same as above.

Example 8: Weigh 260 parts of PVA, 560 parts of starch, and 20 parts of PHB in a mixer, stir well, weigh 220 parts of water, add 3 parts of borax to the water, 12 parts of ethylene glycol dioctyl phosphate titanium, silicone oil 1 part, add this aqueous solution into the mixer, weigh 190 parts of the plasticizer mixed solution with the ratio of glycerin: ethylene glycol adipate: dodecyl alcohol of 12:4:3, and add the mixed solution under stirring. In the feeder, after the material is stirred evenly, the granulation and blow molding process is the same as above.

Example 9: Weigh 250 parts of PVA, 550 parts of starch, stir well in a mixer, add 230 parts of water, add 3 parts of borax to the water, 12 parts of dioctyl ethylene glycol phosphate titanium, tributyl phosphate 2 parts of ester, under stirring, add this aqueous solution in the mixer, stir evenly, weigh 180 parts of the mixed solution whose ratio of ethylene glycol: glycerol: succinic acid ethylene glycol polyester is 3: 9: 6, Add 60 parts of a mixture of polyethylene acrylate copolymer: ethylene-acrylic acid copolymer at a ratio of 2:1 to the plasticizer, and add the plasticizer mixture to the mixer under stirring, stir well, granulate and blow molding The process is the same as above.

Claims (8)

1. A preparation method of starch-polyvinyl alcohol-polyester ternary system biodegradable film, characterized in that the selected raw materials are by weight percentage: Starch: 30-65%, Polyvinyl alcohol: 15-40%,   Polyesters: 0-10%,   Plasticizers: 10-20%, Reinforcing agent: ≤0.4%, Wet strength agent: 0.5-1.5%,   Defoamer: ≤0.4%, Wherein the plasticizer is ethylene glycol: glycerol: polyester polyol = 1-3: 9-15: 3-6 ternary composite system and water in weight ratio. 2. The method according to claim 1, characterized in that the starch is cornstarch, potato starch, tapioca starch or lotus root starch. 3. The method according to claim 1, characterized in that the polyvinyl alcohol is polyvinyl alcohol-1799 or polyvinyl alcohol-1999. 4. The method of claim 1, wherein the polyester is polycaprolactone, polycarbonate, polyethylene-acrylate, poly-β-hydroxybutyrate or ethylene-acrylic acid copolymer. 5. The method as claimed in claim 1, characterized in that the polyester polyol is ethylene glycol from succinic acid to sebacic acid, polycondensation ester or dodecyl alcohol ester of ethylene glycol; 6. The method according to claim 1, wherein the reinforcing agent is potassium aluminum sulfate, basic alumina, borax or sodium silicate. 7. The method according to claim 1, characterized in that the wet strength agent is β-alkoxy ethyl carboxyl two (dioctyl pyrophosphate) titanium, ethylene diethylene alkoxy phosphate dioctyl titanium or diisopropoxy triethanolamine titanate. 8. The method according to claim 1, characterized in that the defoamer is tributyl phosphate or silicone oil.