KR101144730B1 - Fabracating method of thermoplastic cellulose polyester - Google Patents

Abstract

Acetylating at least a portion of the hydroxyl groups of the cellulose in the ionic liquid to form cellulose acetate, and ring-opening of the cyclic acetate to the residual hydroxyl groups in a batch without separating the cellulose acetate from the ionic liquid Provided is a method for producing a thermoplastic cellulose ester comprising the step of continuously performing a graft polymerization reaction.

Description

Manufacturing method of thermoplastic cellulose ester {Fabracating method of thermoplastic cellulose polyester}

The technology disclosed herein relates to a method for producing a thermoplastic cellulose ester, and more particularly, to a method for producing a thermoplastic cellulose ester which is environmentally friendly and has an improved process.

Cellulose is the largest biomass produced on earth, and is a natural polymer that is biodegradable in the environment and has excellent physical properties. However, cellulose has very high crystallinity due to strong hydrogen bonding between molecular chains by hydroxyl groups in glucose, which is a monomer, and has a property of not being dissolved in a general organic solvent or water at all.

For this reason, in order to increase the processability of the cellulose, a cellulose derivative is used in which the hydroxyl group of the cellulose is blocked by a substituent to weaken the hydrogen bond, thereby lowering the crystallinity. Cellulose acetate propionate, cellulose acetate butyrate, cellulose phthalate, and the like, and are used in a wide range of fields such as fibers, plastics, filters, and paints.

However, these cellulose derivatives do not have sufficient thermoplastics and suffer from decomposition or coloring before they soften when melted by heating. Due to these problems, a technique of applying a plasticizer or grafting an aliphatic polyester to a hydroxyl group remaining in the cellulose derivative has been proposed in order to increase thermoforming of the cellulose derivative.

According to the above production method, the cellulose derivatives are subjected to a graft reaction based on cellulose acetate, and in order to prepare thermoplastic cellulose, preparation of cellulose acetate corresponding to a precursor is preceded. Traditionally, cellulose acetate is synthesized by adding an excess of acetic anhydride under a catalyst such as hydrochloric acid or sulfuric acid in a heterogeneous system. This reaction is an environmentally harmful process, and the degree of substitution cannot be controlled.

According to one embodiment, acetylating at least a portion of the hydroxyl groups of cellulose in the ionic liquid to form cellulose acetate, and remaining hydroxyl groups of the cellulose acetate in a batch without separating the cellulose acetate from the ionic liquid Provided is a method for preparing a thermoplastic cellulose ester comprising the step of continuously performing a ring-opening graft polymerization of a cyclic ester.

According to one embodiment of the technology disclosed herein, the thermoplastic cellulose mixed ester may be prepared by the following method.

First, at least a portion of the hydroxyl groups of the cellulose in the ionic liquid is acetylated to form cellulose acetate.

The ionic liquid refers to a liquid consisting only of ions, and is generally composed of a large cation containing nitrogen and a smaller anion. This structure reduces the lattice energy of the crystal structure and consequently has a low melting point. Ionic liquids are not only used as clean solvents and catalysts in various organic chemical reactions because of their unique properties different from conventional organic solvents. Can be utilized.

The ionic liquid can be 1-alkylpyridinium, alkyl or polyalkylpyridinium, phosphonium (PR ₄ ⁺ ), alkyl or polyalkylphosphonium, imidazolium, alkyl or polyalkylimidazolium, ammonium (NR ₄ ⁺ ), Alkyl or polyalkylammonium, alkyl or polyalkylpyrazolium, alkyl or polyalkylpyrrolidinium, alkyl or polyalkylazpinium, alkyloxonium or alkylsulfonium have.

At the same time, the ionic liquid is a halide, preferably chloride, bromide or iodide, nitrate, alkylsulfate or alkyl polyalkoxysulfates such as methanesulfonate, trifluoromethanesulfonate and hydrogensulfonate, metal Oxo anions, and anions selected from one or more of anions based on nitrogen, phosphorus, boron, silicon, selenium, tellurium and halogens.

Specifically, the ionic liquid is 1-butyl-3-methylimidazolium chloride, N-ethylpyridinium bis (trifluoromethanesulfonyl) amide, N-methyl-N'-butylimidazolium tetrafluoro Borate, N-methyl-N'-butylimidazolium bis (trifluoromethanesulfonyl) amide, trimethyl (2-hydroxyethyl) ammonium bis (trifluoromethanesulfonyl) amide, N-methyl-N ' -Ethylimidazolium 2-methoxyethylsulfonate, N-butyl-N-methylpyrrolidinium bis (trifluoromethanesulfonyl) amide, N-methyl-N'-butylimidazolium 2-methoxyethyl Sulfonate, N-methyl-N'-butylimidazolium bromide, N-methyl-N'-butylimidazolium 2-ethoxyethylsulfonate, N-methyl-N'-butylimidazolium 1- (1 -Methoxypropoxy) propylsulfonate, N-methyl-N'-butylimidazolium 1- (1-methoxyethoxy) ethylsulfonate, N-methyl-N'-butylimidazolium 1-methyl (Diethoxy) ethyl sulfone Agent, may be N- methyl -N- (tert-butyl-4-sulfonic acid) pyrrolidin pyridinium trifluoromethanesulfonate, or a mixture thereof.

By using the ionic liquid as a reaction medium, a homogeneous reaction due to the effective dissolution of cellulose is possible, and the degree of substitution for each hydroxyl group can be partially controlled.

The acetylation is carried out by substituting a hydroxyl group (the presence of three hydroxyl groups for each glucose) in the glucose which is a unit of the cellulose, in order to satisfy the optimum thermoforming and heat resistance necessary for processing. When the ring-opening graft reaction is performed alone without performing the acetylation, it may have a low degree of substitution as a whole. In this case, it is difficult to obtain effective thermoforming due to an increase in crystallinity due to hydrogen bonding between hydroxyl groups. On the other hand, when the acetylation is carried out to have a high degree of substitution, the flow of aliphatic polyester occurs at a low temperature has a problem that the heat resistance is lowered. Therefore, in order to have adequate heat resistance and thermoforming, the acetylation is preferably performed so as to be 1.0 to 2.9 per glucose unit of the cellulose.

Next, the ring-opening graft polymerization of the cyclic ester of the cellulose acetate to the residual hydroxyl group is continuously performed in a batch without separating the cellulose acetate from the ionic liquid.

Introduction of the polyester side chain into the cellulose acetate can be carried out by ring-opening graft polymerization using cyclic diesters or cyclic monoesters as monomers. The ring-opening graft polymerization reaction by using a monomer having a ring structure, unlike the graft polymerization reaction using a monomer having a general chain structure, has an advantage of suppressing the production of a single polymer corresponding to a side reaction.

As a specific example of the monomer used for the graft polymerization reaction, lactide, glycolide, pripiolactone, pivalolactone and the like can be used alone or in combination. For example, in order to obtain cellulose acetate having a graft side chain composed of D-lactic acid and / or L-lactic acid, graft ring-opening polymerization of cellulose using D-lactide and / or L-lactide as monomers, like D Graft ring-opening polymerization of L-lactide as monomer, graft ring-opening polymerization of D-lactide and / or L-lactide and D, L-lactide as monomer can be exemplified. It is also possible to use other known methods.

In addition, when performing the said ring-opening graft polymerization reaction, it is preferable to use a well-known ring-opening polymerization catalyst. Examples of catalysts that can be used include metals such as tin, zinc, titanium, bismuth, zirconium, germanium, antimony, sodium, potassium, aluminum, and derivatives thereof, and in particular, the organic compounds, carbonates, and carbonates thereof. And halides are preferred. Specifically, tin octanoate, tin chloride, zinc chloride, titanium chloride, alkoxytitanium, germanium oxide, zirconium oxide, antimony trioxide, alkylaluminum, and the like can be exemplified.

According to the above-described method for preparing a thermoplastic cellulose ester, in contrast to the prior art, which is synthesized by adding an excess acetic anhydride under a catalyst such as hydrochloric acid or sulfuric acid in a heterogeneous system, which is environmentally harmful and cannot control the degree of substitution, one-step acetylation By continuously carrying out the reaction and the two-stage ring-opening graft polymerization in one batch, it is carried out in a series of single processes without undergoing the separation and drying of cellulose acetate, thereby making it possible to produce thermoplastic cellulose esters with excellent process stability and economical.

In addition, by appropriately adjusting the acetylation ratio, it is expected that the production of cellulose esters having various thermal properties satisfying the heat resistance of the final product is possible.

The cellulose ester obtained by the above-described method can be applied in various fields of high value-added through the application to medical plastics, films, fibers and the like.

Hereinafter, the technology disclosed herein will be described in more detail with reference to specific comparative examples and examples, but the spirit of the disclosed technology is not limited thereto.

≪ Example 1 >

Cellulose and L-lactide were used in a dry state by vacuum drying at 60 ° C. for 24 hours. To a 150 ml three-necked flask equipped with a nitrogen inlet, a condenser and a stirrer, 20 ml of ionic liquid 1-butyl-3-methylimidazolium chloride, 1 g of cellulose and 2 g of L-lactide were added. The system was completely dissolved while immersed in an oil bath and stirring at 100 ° C. Thereafter, 0.6 ml of acetic anhydride was added for acetylation, and reacted for 1 hour. Subsequently, 0.02 g of tin octanoate was added as a ring-opening polymerization catalyst, and graft ring-opening polymerization was performed for 24 hours. After completion of the reaction, the flask was removed from the oil bath and precipitated in a large amount of ethanol to obtain a precipitate. The precipitate was collected by filtration and dried, and then stirred in methylene chloride for 72 hours to completely dissolve the single polylactide produced during the reaction, followed by filtration, drying and analysis.

1 is a ¹ H-NMR chart of the cellulose ester obtained by the method of Example 1. FIG.

Comparative Example 1

The same procedure as in Example 1 was carried out, but the cellulose ester substituted with only aliphatic polyester was synthesized by performing only the graft ring-opening polymerization reaction of L-lactide without undergoing an acetylation reaction.

2 is a ¹ H-NMR chart of the cellulose ester obtained by the method of Comparative Example 1. FIG.

Experimental Example 1

In order to determine the thermoformability of the cellulose ester synthesized by the method of Example 1 and Comparative Example 1, a disk-type film was prepared using a thermocompressor. The upper and lower temperatures of the thermocompressor were fixed at 180 ° C., and the pressing time was carried out for 5 minutes.

3 is a photograph of a cellulose ester film prepared by the method of Experimental Example 1. Referring to FIG. 3, in contrast to the cellulose ester prepared in Comparative Example 1, in the case of the cellulose composite ester prepared by the method of Example 1, a transparent disk having a smooth surface and no defects was prepared, and it was confirmed that the thermal characteristics were improved. .

1 is a ¹ H-NMR chart of the cellulose ester obtained by the method of Example 1. FIG.

2 is a ¹ H-NMR chart of the cellulose ester obtained by the method of Comparative Example 1. FIG.

3 is a photograph of a cellulose ester film prepared by the method of Experimental Example 1.

Claims (4)

Acetylating at least a portion of the hydroxyl groups of the cellulose in the ionic liquid to form cellulose acetate; And continuously performing ring-opening graft polymerization of the cyclic ester of the cellulose acetate to the residual hydroxyl group in a batch without separating the cellulose acetate from the ionic liquid, The acetylation is a method for producing a thermoplastic cellulose ester to be 1.0 to 2.9 per glucose unit of the cellulose. delete The method of claim 1, The cyclic ester is a method for producing a thermoplastic cellulose ester of at least one selected from the group consisting of lactide, glycolide, pripiolactone, and pivalolactone. The method of claim 1, A method for producing a thermoplastic cellulose ester having an aliphatic polyester side chain by the ring-opening graft polymerization.

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