GB2273458A

GB2273458A - Vegetable cellulose films

Info

Publication number: GB2273458A
Application number: GB9325981A
Authority: GB
Inventors: Taogen Jin; Shuixin Tong; Mingzhen Li; Hualin Zheng; Yongwei Yu; Jianzhong Xu; Hongzhen Luo
Original assignee: China Int Ass Science & Tech
Current assignee: China Int Ass Science & Tech
Priority date: 1992-12-18
Filing date: 1993-12-20
Publication date: 1994-06-22
Anticipated expiration: 2013-12-20
Also published as: JPH0770366A; GB9325981D0; DE4342723A1; CN1088225A; CA2111732A1; CN1036140C; GB2273458B; BR9305113A; AU5251393A; AU677243B2; KR940014563A

Description

2273458 60674.53 Vecretable Cellulose Films The present invention relates

to vegetable cellulose film products and a process of preparing the same. These cellulose films can be used as farming films and packages of goods, especially food, such as sausages, fruits, vegetables, candies and cakes, and pharmaceuticals. They can also be used as materials for making green carpets,. garbage bags and dialysis bags. The present invention also relates to decomposable cellulose farming films, decomposable cellulose farming films for weed-killing, decomposable cellulose farming films for insect/germ-killing, decomposable cellulose farming films with N,P,K, and rare-earth elements, decomposable cellulose farming films with trace elements and rare-earth elements, and a process of preparing the same.

It is well-known that there are various kinds of synthetic high molecular films and products in the world developed rapidly since the early sixties. Polyethylene farming films and products of other synthetic high molecular materials have been used in almost every industry. The volume of the raw material used in making farming films of polyethylene in early 90s in China exceeded 500,000 tons with a coverage of over 50,000,000 Mu with an annual increase rate of 15%-20%. The volume of the raw material used is expected to reach 700,000--- 1,000,000 tons with a coverage of 70,000,000---100,000,000 Mu by the year 1995.

With an increased awareness of the environment and more and more concerns of environmental pollution, scientists in each country in the world are paying serious attention to the adverse effects on the environment and the normal growth of crops caused by high molecular 2 synthetic plastic products and farming films of polyethylene that have been used in big volumes, are hard to retrieve, and do not decompose in the soil where they have been buried for a long time. Since the early 90s, statutory prohibitions and limitations have been made successively in some of the West-European countries, Japan and the U.S. with regard to using as packaging material various kinds of high molecular plastic products that do not decompose. As a result, these countries started to develop decomposable packaging materials and novel farming films that decompose by light.

It has long aroused people's interest how to replace is synthetic high polymer compounds with decomposable films. One way has been to blow at a certain temperature (170-200OC) a mixture of starch (20-150 gm) and polyethylene that contains over 30% of starch and is well mixed mechanically. As the particles of starch and the melt materials move at different speeds, an apertured film is formed, which is fragile and of low strength. Though this kind of starch film carries many hydroxy groups, is of good hydrophilicity, and can be decomposed by microorganisms, the polyethylene mixed with it cannot decompose. Moreover, its applicability is limited because of its thickness, low strength and transparency. Another way has been to introduce the starch particles into the chemical chain so as to promote the mixing of the synthetic polymers. Films so formed are disclosed in U.S. 4337181, GB 1487050 and GB 1485833. Though they can decompose, the method of preparing the film is complex and costly, and the films are low in tensile strength, great in thickness and cannot be stretched.

Light-decomposable films are synthetic high polymers where in a certain amount of photosensitizer is added during the filming process (EP230143) and the films are formed by blow- forming (calendering) under hot melt. This type of film can be decomposed under ultraviolet rays. However, such decomposition is not complete, i.e.

the synthetic high polymers cannot be completely decomposed into C02 and water, and what is more, when these high polymers are buried into the soil without any sunlight shining on them, they simply cannot be decomposed. In particular, when light-decomposable films are used as farming films, their decomposition and the season of growth of the crops are not simultaneous. In other words, the covering farming films should be decomposed when the crops do not need to be covered any longer; and vice versa, there should be no decomposition when the crops still need to be covered. However, the decomposition of the farming films made of lightdecomposable films developed by now is hard to control because various conditions have impact on the decomposition. This has many times resulted in the reduction of output of the crops (sometimes, because the decomposition period is not "synchronous" with the season of growth of the crops.) Thus, the decomposition of light-decomposable films must be "controllable", which, however, is quite difficult.

A decomposable film and a method of making it are described in the specification of CN90109135.9, wherein a biologically decomposable film is formed by using synthetic polymers (olefins such as polyethylene or polypropylene) and bio-decomposable polymers (such as starch or cellulose) as the basic material. However, as synthetic high polymers are also used in this kind of film, the filming process is rather complicated.

Moreover, even though the high polymers used may decompose, the time consumed in the decomposition is quite long (the longest is two years), and whether the remnants after the decomposition are toxic and harmful 4 to the farmland is yet to be tested.

The specification of W 90109250.9 describes a method of making regenerated cellulose films out of cotton straw and peanut shell. Though "agricultural by-products" are used instead of synthetic high polymers in this method, much pollution is caused by using a solution of copperammonia as a solvent to make the viscose, the treatment of the waste water is difficult, there are over 50% of the noncellulose in the raw materials and the yield is low.

In view of the problems coming up in preparing and developing decomposable films in and outside china, in is May of 1988 the inventors of the present invention started to study and develop farming and forest films made out of straw fibers that are cheap and decomposable, and filed with the Chinese Patent Office in June of 1990 a patent application entitled "A Farming/Forest Film of Straw Fibers and the Method of Making the Same", (Application No.90103061.9 and Publication No. CN10580284,) which is cited here for reference. The straw farming film of that invention overcame the problems met by researchers in developing decomposable films. It has, among other things, the following advantages: The raw materials used are rich in resources, the'film can be decomposed by microorganisms in the soil, and the film can preserve moisture and temperature in the soil, thus it can replace polyethylene farming films and other starch films and light-decomposable films available on the present market. Meanwhile, the film can also replace many plastic products on the market which are made of synthetic high polymers, there by solving the pollution problem caused by synthetic high polymers that cannot be decomposed. Despite this, problems remain to be overcome and we have now been able to develop a vegetable cellulose film which has substantial improvements, and is a prominent technological advance.

According to one aspect of the present invention we provide a vegetable cellulose film and a process for its preparation, which film can be used as farming films, packages of goods, especially packages of foods, green carpets, and materials for dialysis bags and garbage bags as well. A vegetable cellulose film of the invention comprises vegetable cellulose, modifier(s) and water, with a composition of (by weight) Vegetable cellulose 50-90% Modifier(s) 0.2-40% Water 5-20-0.

is The raw material for the vegetable cellulose used in the vegetable cellulose film of the present invention may be crop straw such as straw of rice, wheat, vegetable seeds, sunflower, maize, Chinese sorghum and soybean; crop shells such as the shells of peanut and sunflower seeds; natural vegetable cellulose such as cotton velvet and hemp; wood such as birch, China fir, pine and bush; plant pulp and residue such as wood pulp and bagasse; grass such as Chinese alpine rush (eulaliopsis binata) and reed; and bamboos.

According to the present invention, the vegetable cellulose film comprises preferably 55-85% by weight of vegetable cellulose, and most preferably 60-80%.

The types of modifiers that may be used in the vegetable cellulose film of the present invention are various, e.g. aromatic esters such as di-nbutyl phthalate, dicapryl phthalate, di-(2-ethyl hexyl) phthalate, diiso-nonyl phthalate, diheptyl phthalate, butyl benzyl phthalate, di-isononyl phthalate, butyodecyl phthalate, butyl phthalyl butyl glycollate, di-(2-ethylhexyl)4, 5- 6.

epoxy tetrahydro phthalate, butyldecyl terephthalate; aliphatic esters such as dimethyl glutarate, dibutyl glutarate, ethylene glycol di C5-C9 fatty acid esters, pentaerythritol fatty acid ester, diethyleneglycol di C7 C9 mixed acid esters, ethylene glycol butyrate, dioctyl sebacate, dicapryl sebacate, di-2-ethylhexyl maleate, butyl ester of epoxy fatty acids, 2-ethylhexyl ester of epoxy fatty acids, sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan monolaurate, sorbitan trioleate and the like; hydrocarbons and their substituted compounds such as emulsified paraffin, chlorinated paraffin, mixture of chlorinated alkyl benzene sulfonate and chlorinated paraffin and the like; phosphate esters 1-5 such as dibutyl phenyl phosphate, sodium hexametaphosphate, diphenyl octyl phosphate, tricresyt phosphates and the like; polyhydric alcohol and its derivatives such as glycol, diethylene glycol, triethylene glycol, glycerin, sorbitol and the like; ethanolamines such as ethanolamine, diethanolamine, triethanolamine and the like; vegetable oil such as soybean oil, peanut oil, rapeseed oil, palm oil, tung oil, castor oil, and the like; polyoxyethylene ethers such as alkyl phenyl polyoxyethylene, aliphatic alcohol polyoxyethylene ether, high aliphatic alcohol polyoxyethylene ether and the like; acrylic acid and its derivatives capolymers such as polyacrylic acid, polyacrylamide, poly methyl-pentyl acrylate, acrylic acid- acrylamide copolymer, acrylic acid-Cl-C5 acrylate copolymers; polyalkylacrylic acid, polyalkylacrylamide, poly Cl-C5 alkylacrylate, alkylacrylic acid-C l-CS alkylacrylate copolymers, polyvinyl alcohol and polyvinyl acetals such as polyvinyl alcohol, polyvinyl formal-butyral, polyvinyl acrylal and the like; polyvinyl acetate and vinyl acetate copolymers such as polyvinyl acetate, vinyl acetate-C2-C5 olefins copolymers, vinyl acetate -acrylic acid and its 7 derivative copolymers, vinyl actetate -- acryl olefin copolymers and the like; polyolefins and olefins copolymers such as polyethylene wax, oxide polyethylene, emulsified polyethylene, polyvinylidene chloride, vinyl chloride vinylidene chloride copolymer, polyvinyl perchloride and the like; poly acryl olefins and copolymers such as styrene -- butadiene copolymer, carboxylated styrene butadiene copolymer etc.; cellulose and starch such as carboxymethyl cellulose, hydroxyethyl cellulose, denatured.starch etc.; alkyd resins such as water soluble alkyd resins, and epoxy resins such as water soluble epoxy resins. Other modifiers comprise amino resins such as melamine -- formaldehyde resin, silicone, and sodium alginate and the like.

Out of the above modifiers, the following are preferred: aromatic esters such as di-n-butyl phthalate, dicapryl phthalate, di-(2-ethyl hexyl) phthalate, di-iso-nonyl phthalate, butyl benzyl phthalate, butyl phthalyl butyl glycollate, C4-Cl. terephthalate etc.; aliphatic esters such as di-butyl sebacate, di-octyl sebacate, di-capryl sebacate, ethylene glycol di-C 5-C 9 fatty acid ester, sorbitan monostearate, sorbitan monopalmitate, di- 2ethylhexyl maleate, 2-ethylhexyl ester of epoxy fatty acids; hydrocarbons and their sustitutes such as emulsified paraffin, chlorinated paraffin; phosphate esters such as dibutyl phenyl phosphate, sodium hexametaphosphate, di-phenyl octyl phosphate; polyhydric alcohol and its derivatives such as glycol, di-ethylene glycol, triethylene glycol, glycerin; vegetable oil such as castor oil; polyoxyethylene castor oil, polyoxyethylene ethers such as aliphatic alcohol polyoxyethylene ether; high aliphatic alcohol polyoxyethylene ether, copolymers such as polyacrylic esters and acrylate copolymers, vinyl acetate -acrylate copolymers, ethylene -- vinyl acetate copolymers, styrene -- acrylate copolymers; polyolefins p a and olefins copolymers such as polyethylene wax, styrene - butadiene copolymer, carboxylated styrene butadiene copolymer, polyvinylidene chloride, vinyl chloride -vinylidene chloride resins, and carboxymethyl cellulose, water soluble alkyd resins, water soluble epoxy resins, and melamine formaldehyde resins.

Each of the above modifiers can be used alone or together with others according to the property of the film to be made. The amount of the modifier used is, by weight, 0.2%-40%, based on the weight of the vegetable cellulose film, preferably 0.5t-20%, and most preferably 1-15%. The modes of use of the modifier are various, for instance, the relevant modifier from the above may be added into the viscose in a given ratio to form a film, or after the regenerated cellulose film has been formed. The film may be spun, coated or immersed with the modifier to form a complex film. The decomposable vegetable cellulose film formed may be 8-20 g thick.

The test results of its properties of biology, optics, mechanics and its experimental results obtained on experimental farmland plots (eleven plots) with regard to different crops, weather and soil show that the film is of good property.

I. Mechanical Property Longitudinal Tensile Strength 17.3-49.2 MPa Transverse Tensile Strength 13.3-30.4 MPa Il. Optical Property Transmittance 83.2-91.1% III. Biological Property 9 When buried in wet soil of 15cm deep, the film started to decompose slightly in 40 days and finished decomposing in 80 days. When covered on the soil, slight crackles appeared in 60 days and the film started splitting open and decomposed quickly in 100 days.

When the film was immersed in soil water for continuous decomposition for 15 days during the imitation experiment inside house, the rate of decomposition was totally 3-4.69%.

IV. Field Tests

Experiments on peanut, cotton, soybean, maize and water melon show that the production of these crops has all been greatly increased, the general increase rate being 20%, and the highest increase rate of maize being 50%.

According to a further aspect of the present invention we provide vegetable cellulose films that kill weeds, insects and germs and/or have compound fertilizing ingredients of N, P or K and trace elements / rare-earth elements. The methods of preparing these multifunctioned films may be the same as those for preparing the above vegetable cellulose films, except that chemical substances having these special functions are added by way of spinning, coating or immersing.

Weed - Killing Farming Film of Cellulose A weed-killing cellulose farming film may be prepared, which additionally comprises water soluble herbicides of 0.05-1g/m2. One or a mixture of more than one of the following herbicides may be used according to different crops and weeds: glufosinate, gramoxone (paraquat), difenzoquat, dalapon, bialaphos, alloxyelim-sadium, acifiuorfen sodium and sodium pentachlorophenate.

- Insect-Killing Cellulose Farming Film An insect-killing cellulose farming film may be prepared, which additionally comprises one or more insecticides that are water soluble. One or a mixture of more than one of the following insecticides are added to the film: monocrotophos, phosphamidon, mevinphos, omethoate, 2-dimethoxy phosphinyl imino-1, 3-dithiofive ring, methamidophos,-acephate soluble powder, 2(dimethoxy phosphimide)-1, 3 dithio five ring, insect grass, 2-N, N-dimethylamino-1, 3-bis (thiosulfato sodium) propane, thiocyclam soluble powder, bandane and cyhexatin. The amount of the insecticides used is controlled at 50-200OPPm/m2.

Germ-Killing Cellulose Farming Film This type of film additionally comprises one or more germicides that are water soluble and non-toxic. one or a mixture of more than one of the following germicides is used in this film, whose amount used is generally 50-200OPPm/m2: folpet-AM, Sodium P-amino bengensulfonate, phosethyl Al, and p-phthalic acid.

Vegetable Cellulose Farming Film With Compound Fertilizer containing N P K This film further comprises a single fertilizing ingredient like N, P or K, or compound fertilizers. A solution with the fertilizing ingredient is fixed onto the surface of the film by way of spinning, coating or immersing. The fertilizing ingredient goes into the soil when the film decomposes or the water vapor on the film surface drops into the soil so that the fertilizing ingredients for the nutrition of crops are increased. One preparation of such a film is to dissolve the solid fertilizers in water, then fix the solution onto the surface by spinning, coating or immersing. The fertilizing ingredient falls into the soil or onto the soil or onto the leaves of the crops together with the water vapor of the film during the decomposition process of the film or during the growth of the crops so that the nutrient for the crops is increased, which gives a possible increase of the production. Said fertilizing nutrient includes one or a mixture of more than one of the following: urea,-ammonium sulphate, ammonium hydrocarbonate, ammonium nitrate, ammonium chloride, single superphosphate, fused calcium- magnesium phosphate, calcium phosphate secondary, diammonium hydrogean phosphate, potassium chloride, potassium dihydrogen phosphate, potassium chloride, potassium dihydrogen phosphate, which are all water soluble. The effective concentration of the fertilizing nutrient on the film surface (N:P:K:=6:3:1) is generally 200100OppM/M2.

Vegetable Cellulose Farming Film with Trace/Rare Earth Elements A film may be prepared which further comprises one or more trace elements. It may be prepared by dissolving one or a mixture of salts of the following elements, iron, manganese, zinc, magnesium, nickel, cobalt, copper and tin, extracting the elements from the salts, making a solution with the elements and fixing the solution onto the surface of the film by way of immersing, coating or spinning. A film further comprising one or more rare-earth elements may be prepared by fixing mixed rare-earth elements onto the surface of the film in the same way as the above. The content of the trace elements and rare-earth elements used may be controlled 2 at 0.05-10PPin/m 12 - According to another aspect of the present invention, there is provided a process for preparing a vegetable cellulose farming film which comprises making a vegetable cellulose viscose from a vegetable cellulose raw material and forming a film.

Preferably the process includes the following steps:

1. the vegetable cellulose in the vegetable cellulose raw material is concentrated and purified into a dry pulp or wet pulp, which is immersed and stirred in a solution of alkali to dissolve hemi- cellulose, and the pressed alkali cellulose is shredded; 2. the alkali cellulose is warmed to promote its chain scission and degradation, 3. the degraded alkali cellulose is mixed, when being stirred under a vacuum of 600-70OmmHg, with CS 2 for sulfonation. After a solution of alkali is added, the cellulose is stirred until the cellulose is fully dissolved. Then a modifier is added and stirred to uniform the mixture and provide a light-yellow viscose.

4. the viscose is filtered to eliminate impurities, 5. the viscose is defoamed by suction and is then ripened, 6. the ripened viscose is spun, 7. the viscose is coagulated in a coagulating bath, 8. coagulated cellulose film is regenerated in a regenerating bath of sulphuric acid and washed with water, 13 9. the regenerated film is desulphurized in an alkali solution and washed with water, 10. the desulphurized film is bleached and washed with water, 11. the bleached film is plasticized to improve its plasticity, 12. the plasticized film is pressed to reduce the moisture content and the thickness and to increase the strength of the film, 13. the pressed film is dried e.g. in hot air, is 14. the dried film is coated on its surface with a surface modifier(s) to provide a vegetable cellulose film, and 15. the cellulose film is wound up.

Brief Description of the Drawings

Fig. 1 is a flow chart of the steps of one method for preparing and filming a vegetable cellulose viscose of the present invention.

Fig. 2 is a flow chart of the steps for preparing and filming another type of vegetable cellulose viscose of the present invention.

The following is a more detailed description of a method of the present invention given in connection with the above flow charts.

1 Preparation of Vegetable Cellulose Viscose 1) Alkali Immersing, Pressing and Shredding According to the type of the raw material used, first, the cellulose in the raw material is concentrated and purified to get a dry pulp (or pulp dregs) or wet pulp of cellulose. If a wet pulp is obtained, the moisture content should be controlled at e.g. 10-60%, the pulp is 10 immersed in alkali with a concentration of e.g. 14-25%, such as NaOH, and stirred, e. g. for 40-120 minutes at 40-140 r.p.m. After surplus alkali is pressed out, hemicellulose is extracted to make disposable containers, such as cups, food boxes and instant-meal 15 boxes, and the alkali solution is recycled after the extraction. The alkali cellulose, which has been pressed, is then degradated in an aging drum after it is shredded. 20 2) Degradating Alkali Cellulose at Controlled Temperature In the aging drum, the pressed and shredded alkali cellulose is warmed to for example 20- 1000'C, preferably 25 to 40-800C, and best to 45-650C, for 1-3 hour(s) to control the polymerization degree of the cellulose at about 200-600, and kept at 10-30'C for 0.5-2 hours to prevent the cellulose from further degrading under high temperature. 30 3) Sulfonating -- Dissolving After degradation, the alkali cellulose is put into a reaction tank where it is sealed and stirred. Under a vacuum of 600 mmHg, CS 2 of 15-45t (WT) by the weight of 35 the cellulose is added into the alkali cellulose to react for 1-2.5 hour(s). When the V value of the cellulose xanthate reaches 20-40, an alkali solution of 10-15% is added and stirred at a low speed for 1.5-4 hours. When the cellulose is completely dissolved, a modifier is added and stirred evenly to provide a lightyellow cellulose viscose, whose cellulose content is managed at 5-9%, alkali content 4-7.5%, and viscosity is 30-90 seconds measured by the falling ball method.

4) Filtering the Viscose The viscose may be filtered twice so as to prevent impurities from getting into the filming process and to increase the quality of the film.

5) Defoaming and Ripening the viscose is The viscose may be defoamed under vacuum. During the process of vacuum defoaming, hydrolysis saponification happens inside the viscose and xanthic acid is formed. The degree of the formation of the xanthic acid is measured with a salt solution. When the ripening degree reaches 4-8, film- forming may be performed. The ripening period is generally 30-80 hours and the temperature is 8-30'C.

In preparing the viscose of the present invention, the steps of the alkali immersing, shredding, chain scission and degradation, sulfonation, and dissolution of the vegetable cellulose may be combined into one step(see Fig.2) and the viscose is prepared by using a unified machine for viscose preparation. The composition of the viscose so prepared is the same with that by the above method, and the choice of the method is based upon the quality of the vegetable cellulose.

Film-forming Referring to Figs. 1 and 2, the film-forming of the 16 present vegetable cellulose viscose is continuously made on a casting machine whose linear velocity is 10-60M/sec, film thickness is 8-20 A, preferably 12-14 M, and film breadth is about 1.5m.

1) Spinning Spinning is important to the quality of film-forming. When operating, the crack should be 0.15-0.25 mm and the pressure of the cavity is 0.05-0.2MPa.

2) Coagulating The coagulating bath contains sulphuric acid of 90-180 g/1, sodium sulphate of 180-240 g/1 and some defoaming stabilizer of 20-80 g/1. The coagulating temperature is 40-600C.

3) Regenerating The regenerating bath is a solution of sulphuric acid of 50-130 g/1. The regenerating temperature is 40-70'C.

4) Desulphurizing The regenerated cellulose film is desulphurized under 60-90C in a desulphurizing tank that contains an alkali solution of 0.15-0.80 g/1.

5) Bleaching The desulphurized film is bleached under 20-300C in a bleaching tank that contains calcium hypochlorite, sodium hypochlorite or by using an ozone generator. The effectiveCl and 0 contained are 0.3-1.2g/1.

17 - 6) Plasticizing The bleached film is plasticized by using diethylene glycol or glycerin of 8-17% and silica sol of 0.5-2.0% to change the feel and plasticity of the film.

7) Pressing The plasticized cellulose film that contains much moisture is pressed by using two rollers that are of different hardness to reduce the moisture and thickness, and to increase the strength and intensity of the film so as to reduce the energy consumed in evaporating the moisture during the subsequent drying step.

During the above film-forming process, in order to prevent the mixing of the solution of upper step with the solution of subsequent step from regenerating to bleaching and to ensure that the concentration of the solution does not change greatly, a washing tank of 40-60'C is respectively arrarged between each processing step.

8) Drying The pressed film is dried by evaporating its moisture with the help of hot wind during the period when the film moves in the drying roller. The linear velocity of the drying roller is the same as that of the casting machine, and the temperature of the hot air is preferably not too high. The temperature of the drying should be like this: low-high-low-cool. After the film is dried, 5-20% of moisture should remain in the film body.

18 9) Modifying the Film Surface The surface of the dried film may be coated by a coating machine with 2-5 g of one or more than one of the following: surface modifier, insecticide, herbicide, and germicide, or with fertilizing nutrient of N,P or K, trace elements and rare-earth elements.

The following non-limiting examples illustrate the present invention..

Example 1 An absolutely dry pulp of rice straw of 1000g (having 70% of a cellulose) was pressed by a pressing machine to retain 35% of moisture, immersed and stirred in 70 liters of 20% of NaOH for 60 minutes, and pumped into a small-hole pressing machine by a slurry pump, with the NaOH content in the pressed alkali cellulose being about 14% and cellulose content being about 30%. After being shredded by a shredding machine, the alkali cellulose was added into an aging drum of 5000C to be aged for 1.5 hours. The temperature was maintained for 1 hour by using tap water. The alkali cellulose was sent into a sulfonating tank to be stirred at a low speed (12 r.p.m.), sealed and pumped into a vacuum of 60OmmHg, mixed with 160 ml of CS, (the amount was 30% of the cellulose) to react for 1.5 hours until the V value of the cellulose reached beyond 30. A NaOH solution of 11% was added to dissolve the cellulose xanthate formed, the rotational speed was quickened to 24 r.p.m. to make a cellulose viscose of over 5% of NaOH and 8% of cellulose, whose viscosity was 40 seconds (by falling ball method). Into the viscose, meanwhile, di-octyl terephthalat of 8% by the cellulose weight was added and stirred for about 2 hours. After it was substantially dissolved, the viscose was pumped by gear type pump into the post-dissolving tank and stirred for another 2 hours 19 at 150 r.p.m. The post-dissolving tank was cooled by a cooling water. When substantially no small particles of viscose were seen from the sample obtained, the viscosewas pumped by a gear type bump into the middle tank to be filtered. The filtered viscose was sent into a defoaming viscose storage tank to be defoamed, a vacuum of 60OmmHg was pumped and the viscose was aged at a constant temperature of 20'C. After 40 hours the ripening degrees were measured. The filming was carried out when the ripening degree was about 6.

The viscose was driven into the coagulating tank when the casting machine moved at a speed of 30m/sec and the crack of the spinner was 0.20mm, where the concentration of H 2 so 4 in the coagulating bath was about 145g/1, N2 S04 about 210g/1 and the temperature was 45'C. The viscose was coagulated quickly into a film in the tank and went into a regeneration tank having 80g/1 of H2S04 and a temperature of 55'C to be regenerated, washed with water and sent into a desulphurizing tank of 75'C and 0.5g/1 of NaOH to be desulphurized. After the film was washed on the surface, it was sent into a bleaching tank having sodium hypochlorite of 0.5g/1 to be bleached at 250C.

After being washed, the film went into a plasticizing tank of 12% of diethylene glycol and 1% of silica sol to be plasticized. After being pressed, the moisture of the film was 2.5 times the weight of the film. The film was then dried by a drying system with changing temperature from 50OC-90OC-50OC-room temperature until its moisture content was 9%. Finally, onto the surface of the film, triethylene glycol of 5% by the cellulose weight was coated, and a vegetable cellulose of 630g was obtained, whose yield was 87%, moisture content was 10%, thickness was 14.4 M, transparency was 86%, water vapour permeability was 3.50g/m 2 hour(20'C), longitudinal tensile strength was 19.5 MPa, and transverse tensile strength was 15.4 MPa.

Example 2

The operation was the same as that of Example 1, except that wheat straw replaced rice straw; a modifier of sorbitan monostearate replaced di-octyl terephthalate.

The film so prepared had a weight of 600g, a yield of 85.7%, a moisture content of 9%, a thickness of 13.60 a transparency of 86.3%, water vapour permeability of 3.6g/m2hour (20'C), a longitudinal tensile strength of 18.6 MPa and a transverse tensile strength of 16.2 MPa.

Example 3

The operation was the same as that of Example 1, except that wood pulp replaced rice straw; a modifier of di butyl phenyl phosphate replaced di-octyl terephthalate.

The film so prepared had a weight of 610g, a yield of 89.0%, a moisture content of 9%, a thickness of 12.80 g, a transparency of 90.2%, a water vapour permeability of 3.8g/m2hour, a longitudinal tensile strength of 23.9 MPa, and a transverse tensile strength of 18.5 MPa.

Example 4

First, a film was prepared according to the method of Example 1. Immersed and stirred in 10 litres of water for 15 minutes were 1000g of urea, 2000g of calcium dihydrogen 30 phosphate and 1000g of potassium dihydrogen phosphate. 20 litres of triethylene glycol was added into 2 litres of the solution. 2 liters of this mixture solution was applied onto the surface of 20m2 of the film, with the concentration of the N.P.K. coating being about 35 1000PPM/M2 and the ratio of N:P:K being 6:3:1. The film so obtained had a thickness of 16 g, a transparency of 85%, a longitudinal tensile strength of 19.2MPa and a 21 transverse tensile strength of 15.1MPa.

Example 5

First, a film was prepared according to the method of Example 1.

litres of a solution of effective monocrotophos of 200 PPm were prepared. Water soluble alkyd resins were added into 2 litres of that solution, and the mixture solution was applied onto the surface of 20m2 of the film. The film so obtained had 10OPPm/m2 of effective monocrotophos, a thickness of 16 g, a transparency of 85%, a longitudinal tensile strength of 18.4MPa and a is transverse tensile strength of 14.8MPa.

Example 6

The operation was the same as that of Example 1, except that the amount of di-octyl terephthalate added in the viscose was 10% of cellulose instead of 8%. 623g of film was obtained with a yield of 88.9%, a moisture content of 18%, a thickness of 18.3 g, a transparency of 91.6%, a water vapour permeability of 3.52g/m2hour (20'C), a longitudinal tensile strength of 20.3 MPa, a transverse tensile strength of 15.8 MPa.

Example 7

The operation was the same as that of Example 1, except that the amount of di-octyl terephthalate added in the viscose was 14% of cellulose instead of 8%. 604g of the film was obtained with a yield of 85.8%, a moisture content of 12%, a thickness of 15.1 g, a transparency of 35 87. 4%, a water vapour permeability of 3.76g/m2hour (20'C), a longitudinal tensil strength of 21.5 MPa, a transverse tensile strength of 16.9 MPa.

22 Example 8

The operation was the same as that of Example 1, except that the amount of di-octyl terephthalate added in the viscose was 20t of cellulose instead of 8t. 678g of the film was obtained with a yield of 86.3t, a water content of 6%, a thickness of 10.2 g, a transparency of 85.1t, a water vapour permeability of 3.84g/m2hour (20OC), a longitudinal tensile strength of 24.1 MPa, a transverse tensile strength 19.0 MPa.

1 23 - claims 1 A vegetable cellulose film comprising by weight:

vegetable cellulose 50-90% modifier 0.2-40% water 5-20% 2. A vegetable cellulose film according to claim 1, wherein said vegetable cellulose is obtained from one or more of the following: crop straw, shell of crop seed, natural vegetable cellulose, wood, plant pulp, plant residue, grass and bamboo.

3. A vegetable cellulose film according to claim 1 or

Claims

Claim 2, wherein said vegetable cellulose is obtained from one or more of

the following: rice straw, wheat straw, bagasse, Chinese alpine rush, wood pulp, cotton velvet, reed and bamboo.

4. A vegetable cellulose film according to any of claims 1 to 3, wherein said modifier is one or more of the following: aromatic esters, fatty acid esters, hydrocarbons and their derivatives, phosphate esters, polyhydric alcohol and its derivatives, vegetable oil, polyoxyethylene ethers, acrylic acid and its derivative copolymers, polyvinyl alcohol and polyvinyl acetals, polyolefins and olefins copolymers, cellulose and starch, alkyd resins, epoxy resins, amino resins, silicone, and sodium alginate.

5. A vegetable cellulose film according to any of claims 1 or 4, wherein said modifier is one or more of the following: di-n-butyl phthalate, dicapryl phthalate, di-(2-ethyl hexyl) phthalate, di-iso-nonyl phthalate, butyl benzyl phthalate, butyl phthalyl butyl glycollate, C4-cl. terephthalate, di-butyl sebacate, dioctyl 24 - sebacate, di-capryl sebacate, ethylene glycol di-C5-C9 fatty acid ester, sorbitan monostearate, sorbitan monopalmitate, di-2-ethylhexyl maleate, 2-ethylhexyl ester of epoxy fatty acids, emulsified paraffin, chlorinated paraffin, di-butyl phenyl phosphate, sodium hexametaphosphate, di-phenyl octyl phosphate, diethylene glycol, triethylene glycol, glycol, glycerin, castor oil, polyoxyethylene castor oil, aliphatic alcohol polyoxyethylene ether, high aliphatic alcohol polyoxyethylene ether, polyacrylic esters and acrylate copolymers, vinyl acetate-acrylate copolymers, ethylene--vinyl acetate copolymers, styrene-acrylate copolymers, polyethylene wax, styrene-butadiene copolymers, carboxylated styrene butadiene copolymers, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymers, carboxymethyl cellulose, water soluble alkyd resins, water soluble epoxy resins, and melamine formaldehyde resins.

6. A vegetable cellulose film according to any of claims 1 or 5, wherein the modifier present is in the range 0.5-20%, preferably in the range 1-15%.

7. A vegetable cellulose film according to any of claims 1 or 6, wherein the vegetable cellulose present is in the range 55-85%, preferably in the range 60-80%.

8. A vegetable cellulose film according to any of claims 1 to 7, wherein the longitudinal tensile strength is in the range 17.3-49.2 MPa and the transverse tensile strength is in the range 13.3-30.4 MPa.

9. A vegetable cellulose film according to any of claims 1 to 8 wherein the film further comprises a herbicide.

10. A vegetable cellulose film according to claim 9 A wherein the herbicide is one or more of the following:

glufosinate, gramoxone, difenzoquat, dalapon, bialaphos, alloxydim-sadium, acifiuorfen sodium, sodium pentachlorophenate.

11. A vegetable cellulose film according to claim 9 or claim 10 wherein the amount of herbicide present is in the range 0.05-1g/m 2 based on the area of the film.

12. A vegetable cellulose film according to any of claims 1 to 8, wherein the film further comprises an insecticide.

13. A vegetable cellulose film according to claim 12 wherein the insecticide is one or more of the following:

monocrotophos, phosphamidon, mevinphos, omethoate, 2 dimethoxy phosphinyl imino-1,3-dithio five ring, methamidophos, acephate soluble powder, 2(dimethoxy phosphimide)-1,3 dithio five ring, insect grass, 2-N, N dimethylamino-1,3-bis (thiosulfato sodium) propane, thiocyclam soluble powder, bandane, and cyhexatin.

14. A vegetable cellulose film according to claim 12 or claim 13 wherein the amount of herbicide present is in the range 50-2000 PPm/m 2 based on the area of the film.

15. A vegetable cellulose film according to any of claims 1 to 8, wherein the film further comprises a nontoxic germicide.

16. A vegetable cellulose film according to claim 15 wherein the germicide is one or more of the following: folpet-am, sodium p-amino bensensulfonate, phosethyl Al, and p-phthalic acid.

17. A vegetable cellulose film according to claim 15 or claim 16 wherein the amount of germicide present is in 26 the range 50-2000 PPm/m2 based on the area of the film.

18. A vegetable cellulose film according to any of claims 1 to 8, wherein the film further comprises fertilizing nutrient of N, P or K or a mixture of them, and preferably with a ratio of N:P:K=6:3:1.

19. A vegetable cellulose film according to claim 18 wherein the fertilizing nutrient is one or more of the following: urea, ammonium sulphate, ammonium hydrocarbonate, ammonium nitrate, ammonium chloride, single superphosphate, fused calcium-magnesium phosphate, calcium phosphate secondary, diammonium hydrogean phosphate, potassium chloride, and potassium dihydrogen phosphate.

20. A vegetable cellulose film according to claim 18 or claim 19 wherein the amount of fertilizing nutrient present is in the range 200-1000 PPm/m2. 20 21. A vegetable cellulose film according to any of claims 1 to 8, wherein the film further comprises a trace element and/or a rare-earth element.

22. A vegetable cellulose film according to claim 21 wherein the trace element is one or more of the following iron, manganese, zinc, magnesium, nickel, cobalt, copper and tin.

23. A vegetable cellulose film according to claim 21 or claim 22 wherein the amount of trace element and/or rare earth element present is in the range 0.05-10 PPm/m2 based on the area of the film.

24. A process for preparing a vegetable cellulose film as defined in claim 1 comprising making a vegetable cellulose viscose from a vegetable cellulose raw 27 material and thereafter forming a film.

25. A process according to claim 24 comprising the steps:

a) concentrating and purifying vegetable cellulose raw material into a dry pulp or wet pulp, immersing and stirring said pulp in a solution of alkali to dissolve hemicellulose, pressing said cellulose and shredding said pressed cellulose, b) warming the said alkali cellulose to promote its chain scission and degradation, c) adding CS 2 when said degraded alkali cellulose is stirred under a vacuum of 600-700 mmHg for sulfonation, adding a solution of alkali and stirring for full dissolution, and adding a modifier with stirring to get a light-yellow viscose, d) filtering said viscose to eliminate impurities, e) ripening said viscose after said viscose is defoamed under vacuum, 25 f) spinning said ripened viscose, coagulating said viscose in a coagulating bath, h) regenerating said coagulated film in a regenerating bath of sulphuric acid, i) desulphurizing said regenerated film in an alkali solution, 35 j) bleaching said desulphurized film, 28 - k) plasticizing said bleached film to change its plasticity, 1) pressing said plasticized film to reduce the moisture content and thickness and to increase the strength of the film, and m) drying said pressed film.

26. A process according to claim 24 or claim 25, wherein said process further comprises coating the surface of the pressed film with modifier by way of spinning, coating or immersing. 15 27. A process according to any of claims 24 to 26, wherein one or more of the following is coated onto the surface of said film: insecticides, herbicides, germicides, fertilizing nutrients of N, P or K, trace elements and rare-earth elements. 20 28. A process according to claim 26 or claim 27, wherein the coating on the surface of said film is 2-5 g thick. 25 29. A process according to claim 25, wherein in said step a) the moisture content of said wet pulp is 10-60% and the concentration of said solution of alkali is 1425%. 30 30. A process according to claim 251 wherein in step b) the warming temperature is 30-90C and the degree of polymerization of cellulose is 200-600. 31. A process according to claim 25, wherein in step c) 35 the amount of CS2 used is 15-45% (WT) by the weight of the cellulose,' the amount of the cellulose contained in said viscose is 5.0-9.0% and the viscosity is 30-90 29 - seconds.

32. A process according to claim 25, wherein in step e) the ripening temperature is 8-30'C and the ripening time is 30-80 hours.

33. A process according to claim 25, wherein in step f) the crack is 0.150.25 mm and the pressure of the cavity is 0.05-0.2 MPa.

34. A process according to claim 25, wherein in step g) the coagulating temperature is 40-600C.

35. A process according to claim 25, wherein in step h) the regenerating tempernture is 40-70'C.

36. A process according to claim 25, wherein in step i) the desulphurizing temperature is 60-90'C.

37. A process according to claim 25, wherein in step j) the bleaching temperature is 20-30'C.

38. A process according to claim 25, wherein in step m) 5-20% of moisture is kept in the film after said film is dried by hot air.

39. A vegetable cellulose film whenever prepared by a process according to any of claims 24 to 38.

40. A vegetable cellulose film according to any of claims 1 to 23 or 39 for use as a farming film, packaging material for goods, packaging material for food, drinks and pharmaceuticals packaging material for sausages, fruits, vegetables, candies and cakes, green carpet, packaging material for garbage, or a dialysis bag.

41. A vegetable cellulose film substantially as described herein with reference to the Examples.

42. A process for preparing a vegetable cellulose film substantially as described herein and with reference to the Examples and/or the Figures.