KR19990012621A - Biodegradable modified pullulan and preparation method thereof - Google Patents

Abstract

The present invention relates to a method for producing biodegradable pullulan having enhanced hydrophobicity by introducing a carbamate group or an ether group in addition to an ester substituent.

An object of the present invention is to produce a new thermoplastic modified pullulan with excellent moldability and flexibility, and more specifically, without the use of a catalyst, the reaction occurs directly in the solvent and the heat transfer temperature (Tg) of the modified pullulan is low To facilitate the processing. The present invention relates to a method for producing a biodegradable thermoplastic modified pullulan having an appropriate degree of substitution by introducing an ether group and a carbamate group in addition to the ester group in pullulan, and further relates to a method for manufacturing films, plastics and the like.

The modified pullulan produced according to the present invention has a lower glass transition temperature than pullulan or pullulan ester, so that moldability is more excellent.

Description

Biodegradable modified pullulan and preparation method thereof

The present invention relates to a method for producing moldings using biodegradable thermoplastic modified pullulan with enhanced hydrophobicity and modified pullulan. More specifically, the present invention relates to a method for producing biodegradable pullulan having enhanced hydrophobicity by introducing a carbamate group or an ester group in addition to an ester substituent.

Plastics are very widely used in daily life and industry in the present industrial society, and their consumption is continuously increasing. Accordingly, the amount of waste is increasing exponentially, and landfilling or incineration is being processed, but in the case of landfilling, wastes are not biodegraded and form a sort of waste gravel, which causes serious problems at the environmental level. . Efforts are underway to produce materials such as plastics using biodegradable materials as part of the solution to the environmental problems of these wastes.

Natural polymers such as food and paper are biodegradable organics that are decomposed and used as compost. Research is underway to make plastics, films, etc. using these biodegradable natural polymers, and some of them are commercially available. Fibers such as rayon and tencel made of cellulose are typical degradable fibers, and furthermore, they can be mixed with biodegradable synthetic polymers to make pullulan / polyvinyl alcohol (PVA) blend resins to produce fully biodegradable plastics and films. (Kobunshi Ronbunshu, 50, 767 (1993)).

Thermoplastic natural / synthetic copolymers are well blended with natural and synthetic polymers and have biodegradable properties. However, there are problems in controlling the molecular weight and controlling the substitution degree of the polymer in preparing the copolymer. (U.S. Patent 4,891,404)

In general, cellulose is slow in decomposition, while pullulan is not only hydrophilic but also fast in biodegradation. By using the biodegradable properties of pullulan, the rate of biodegradation is often controlled by mixing pullulan at a certain ratio when manufacturing films, plastics, and fibers, and the use of biodegradable materials such as pullulan has been expanded to solve environmental problems. It is becoming a trend.

Although pullulan has excellent biodegradability, there are many changes in physical properties depending on the amount of moisture, and it is limited in use because of less thermoplasticity. In order to overcome the problems of pullulan, a modified pullulan production research has been conducted in which a substituent is introduced to pullulan to lower moisture content and impart thermoplasticity to pullulan. Modified pullulan includes pullulan esters such as acetic acid pullulan, pullulan ether, and the like.

US Patent 4, 863, 655 was used to prepare a water-soluble composition by reacting pullulan with propylene oxide to produce a water-soluble modified pullulan having a degree of substitution of about 0.19. Water-soluble moldings are environmentally friendly because they are readily biodegradable if washed off with water after use. In fact, many water-soluble modified pullulans have been developed and used. Most of them are low-substituted modified pullulans or low molecular weight modified pullulans obtained through hydrolysis, and are intended to lower the gelatinization temperature. These modified pullulans have been used in paper adhesives, food additives, and the like, and the types of modified pullulans include pullulan esters, pullulan ethers, pullulan sulfate, and pullulan nitrate.

Virtually commercially available modified pullulan is a low-substituted ester pullulan obtained by reacting with excess anhydride in water. Pullulan acetate having a substitution degree of 1 or less is water-soluble and used as a food additive when 0.1 or less. Succinate pullulan can be used up to 5% of the substitution degree of 0.07 is recognized by the FDA.

When the filter preparation is prepared by mixing the pullulan ester having a degree of substitution of 2.3 with cellulose acetate, it is cheaper and biodegradable due to the use of acetone, which can reduce environmental problems that may occur during disposal. 446, 140)

International patent WO 95/04083 prepared a biodegradable thermoplastic pullulan resin by reacting pullulan with anhydride under a base catalyst system under anhydrous conditions. Since the base catalyst used in this method is relatively expensive, the manufacturing cost increases and there is a limit of physical properties that can be obtained only in the form of pullulan ester.

An object of the present invention is to produce a new thermoplastic modified pullulan with improved moldability and flexibility, more specifically, without the use of a catalyst, such as a reaction occurs directly in the solvent and the heat transfer temperature (Tg) of the modified pullulan is low To facilitate the processing. The present invention relates to a method for producing a biodegradable thermoplastic modified pullulan having an appropriate degree of substitution by introducing an ether group and a carbamate group in addition to the ester group in pullulan, and further relates to a method for manufacturing films, plastics and the like.

The present invention can add a biodegradable plasticizer that can be mixed to facilitate the process in the production of films, plastics, and the like, and also enables the production of films and plastics by blending modified pullulans and biodegradable polymers.

The present invention provides a method for producing a hydrophobic and biodegradable thermoplastic modified pullulan, and more particularly, anhydrous, isocyanate, alkylhelides, acid chlorides of pullulan in anhydrous aprotic solvent and nitrogen conditions. Or a method for producing a modified pullulan having an ether or a carbamate group in addition to an ester group through pullulan through a reaction with an organic acid.

Modified pullulans can be obtained by reaction of pullulan with various kinds of anhydrides, ketenes, isocyanates, alkylhelides, acid chlorides, or organic acids. The modified pullulan of the present invention is a copolymer in which an ether group or a carbamate group is bonded to the pullulan ester. The pullulan ester moiety ranges from acetate to esters having 18 carbon atoms and can be combined with each other to form a copolymer. The types of anhydrides available include acetic-, propionic-, butyric-, maleic-, succinic-, phthalic-, and stearic anhydrides. As the acetate chlorides, acetic-, propionic-, benzoyl chloride and the like can be used.

The pullulan ether moiety of the invention is characterized by comprising up to 1-18 carbons of the ether and in particular comprising ethyl-, propyl-, benzyl. The pullulancarbamate moiety is obtained through the reaction of isocyanate with pullulan and the type of isocyanate includes phenyl-, cyclohexyl-, dodecyl-, octadecyl isocyanate and the like.

The modified pullulan of the present invention has an ester and carbamate molar ratio of 99: 1-30: 70, more preferably in the range of 90: 10-60: 40, and a total degree of substitution of 0.8-2.5 and more advantageously 0.8 -1.7 (DS). Since esters are more polar than carbamate, maintaining as much molar ratio as possible than carbamate is advantageous in terms of enhanced biodegradability and control of hydrophobicity. In addition, when the degree of substitution is more than 2.5, biodegradation is very slow, and the advantage of biodegradability is deteriorated. In the modified pullulan in the present invention, the ester and ether molar ratios are in the range of 99: 1-10: 90, more preferably in the range of 90: 10-20: 80, and the degree of substitution is 0.8-2.5 and more advantageously 0.8-1.7. (DS).

As anhydrous aprotic solvent, dimethyl sulfoxide, N-methylformaldehyde, dimethylacetimide, pyridine and the like can be used in the reaction. Pullulan turns into a homogeneous solution when heated in dimethylsulfoxide, while in pyridine it forms a heterogeneous solution even when heated. Pullulan in the solution was used in a 1-20% weight ratio, and more advantageously in a 5-15% weight ratio. Reaction of isocyanate with pullulan is carried out in anhydrous nitrogen after removing pullulan in pyridine solution to remove water through azeotropic species. Pullulan should be dried and all water should be removed as much as possible, since the isocyanate breaks when the isocyanate comes in contact with water. Isocyanate is reacted with pullulan to introduce carbamate followed by the addition of acetichydrolide to introduce ester groups to obtain a furfuran copolymer with ester and carbamate. An alkyl group is reacted with pullulan to introduce an ether group, followed by reaction with anhydrides to introduce an ester group, thereby obtaining a pullulan copolymer having an ester and an ether.

After the reaction is completed, the reaction mixture can be poured into ethanol, methanol, water, acetone, ether, etc. to obtain a precipitate of modified pullulan, of which, in the case of pyridine solution, the best precipitation solvent is ethanol, and in the case of dimethyl sulfoxide, This is a good precipitation solvent. Remove pyridine and dimethyl sulfoxide solvent as much as possible, filter, wash 2-3 times with ethanol, and dry to obtain dried denatured pullulan.

The modified pullulans prepared as described above are hydrophobic and thermoplastic, and thus can be used for manufacturing various biodegradable moldings and films.

In the modified pullulan of the present invention, the degree of swelling in water is high in pullulan, whereas the modified pullulan hardly swells. Furthermore, the modified pullulan of the present invention tends to have a lower glass transition temperature (Tg) than pullulan or pullulan ester. As the glass transition temperature is lowered, thermoplastics appear at a lower temperature, easier molding, and thermal decomposition is greatly reduced. Furthermore, by mixing the biodegradable plasticizer and additives in the modified pullulan of the present invention, the workability is improved and the flexibility of the molded product can be improved when manufacturing moldings and films.

Plasticizers include phthalate esters (dimethyl-, diethyl-, dipropyl-, dibutyl-, dihexyl-, diheptyl-, dioctyl-, etc.), dimethyl- and diethylsuccinate and related esters, and Cerrol triacetate, glycerol mono- and diacetate, glycerol mono-, di- and tripropionate, glycerol tributanoate (tributyrin), glycerol mono- and dibutanoate, glycerol mono Di- and tristearate, and other related glycerol esters, lactic acid esters, citric acid esters, adipic acid esters, stealic acid esters, and other biodegradable esters. Triacetin with a breaking point of 258 ° C. is advantageously used as a suitable plasticizer because it induces high flexibility and is commercially available at an affordable price. Organic and inorganic additives may be added to extend the physical properties of the moldings. Inorganic additives include talc, titanium dioxide, calcium carbonate, silicates, and the like, and biodegradable organic additives may include pullulan, cellulose, peccan fibers, and the like.

Example 1

9 g of dried pullulan was added to 150 ml pyridine and stirred for 1 hour at 100 ° C. in a three-necked flask equipped with a condenser. After 50 ml of pyridine was distilled off, 3.6 ml of phenyl isocyanate was added under nitrogen to 20 ° C. After reacting for a time, 5.6 ml of acetic anhydride was added to the mixture for further 3 hours at 100 ° C. Slowly pour the reaction mixture while rotating the 600 ml ethanol solution in a 1 l beaker to precipitate the modified pullulan, filter the precipitates, and rinse 2-3 times with ethanol and dry. The amount of modified pullulan obtained was 14.2 g, and the degree of substitution was carbamate 0.5, acetate 0.8, and the total degree of substitution was 1.3.

Example 2

9 g of dried pullulan was added to 150 ml pyridine and stirred for 1 hour at 100 ° C. in a three-necked flask equipped with a condenser. After 50 ml of pyridine was distilled off, 3.6 ml of phenyl isocyanate was added under nitrogen to 20 ° C. After reacting for a time, 5.4 ml of isetic anhydride is added to react for another 3 hours at 100 ° C. Slowly pour the reaction mixture while rotating the 600 ml ethanol solution in a 1 l beaker to precipitate the modified pullulan, filter the precipitates, and rinse 2-3 times with ethanol and dry. The amount of modified pullulan obtained was 14.1 g, the degree of substitution was carbamate 0.5, acetate 0,76, the total degree of substitution is 1.26.

Example 3

9 g of dried pullulan was added to 150 ml pyridine and stirred for 1 hour at 100 ° C. in a three-necked flask equipped with a condenser. After 50 ml of pyridine was distilled off, 3.6 ml of phenyl isocyanate was added under nitrogen to 100 ° C. After reacting for 20 hours, 5.6 ml of acetic anhydride is added, and further reacted at 100 ° C. for 3 hours. Slowly pour the reaction mixture while rotating the 600 ml ethanol solution in a 1 l beaker to precipitate the modified pullulan, filter the precipitates, and rinse 2-3 times with ethanol and dry. The amount of modified pullulan obtained was 13.8 g, and the degree of substitution was carbamate 0.46, acetate 0.7, and the total degree of substitution was 1.16.

Example 4

9 g of dried pullulan was added to 150 ml pyridine, pre-treated by stirring at 100 ° C. for 1 hour in a three-necked flask with a condenser, and 50 ml pyridine was distilled off and 13 ml octadecyl isocyanate was added under nitrogen to 100 After reacting for 20 hours, 6.1 ml propionic hydride is added and further reacted at 100 ° C. for 3 hours. Slowly pour the reaction mixture while rotating the 600 ml ethanol solution in a 1 l beaker to precipitate the modified pullulan, filter the precipitates, and rinse 2-3 times with ethanol and dry. The amount of modified pullulan obtained was 18 g, the degree of substitution is carbamate 0.4, acetate 1.0, the total degree of substitution is 1.4.

Example 5

9 g of dried pullulan was added to 100 ml of dimethyl sulfoxide and stirred for 20 minutes at 100 ° C. in a three-necked flask equipped with a condenser. The reaction was carried out at 60 ° C. for 24 hours by adding 15 ml pyridine and 5.2 ml benzyl chloride under nitrogen. After the addition, 6.2 ml of acetic anhydride was added and further reacted at 100 ° C. for 3 hours. Slowly pour the reaction mixture while rotating the 600 ml ethanol solution in a 1 l beaker to precipitate the modified pullulan, filter the precipitates, and rinse 2-3 times with ethanol and dry. The amount of modified pullulan obtained was 14.2 g, and the degree of substitution was carbamate 0.4 and acetate 0.9, and the total degree of substitution was 1.5.

Example 6

The swelling test of pullulan and denatured pullulan showed the result as shown in Figure 1. While pullulan swells a lot, denatured pullulans show that swelling is significantly reduced as the number of substitutions increases.

Example 7

The DSC results of the modified pullulans are compared and shown in Figure 3. Dried pullulan shows a glass transition temperature (Tg) near pyrolysis near 260 ° C, whereas denatured pullulan shows a glass transition temperature at lower temperatures, and the addition of plasticizer triacetin makes it easier to form at lower temperatures. It is possible to obtain moldings with possible and enhanced flexibility.

The present invention provides a copolymer having a carbamate or ether moiety in the form of pullulan ester, which has a lower glass transition temperature than that of pullulan or pullulan ester, thereby making biodegradable thermoplastic modified pullulan easier in molding. It relates to the manufacture of the moldings used. Formability can also be enhanced by adding biodegradable plasticizers or additives.

Claims (5)

A biodegradable modified pullulan having an improved hydrophobicity including a carbamate or an ether group in the pullulan ester. A method for producing a biodegradable modified pullulan copolymer having hydrophobicity including carbamate or ether group in pullulan ester. The method of claim 2, wherein the molar ratio of the ester portion and the carbamate portion of the pullulan copolymer is 99: 1-30: 70. The method of claim 2, wherein the molar ratio of the ester portion and the ether portion of the pullulan copolymer is 99: 1-10: 90 to prepare a biodegradable modified pullulan copolymer. The method for preparing a biodegradable modified pullulan copolymer according to claim 2, wherein the total substitution degree of the pullulan copolymer is 0.8-2.5.