JPH11240942A - Production of lactic acid-based copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject copolymer, transparent, colorless, good in color phase and easily controllable for its plasticity by ring-opening copolymerization of a lactide with a cellulosic ester or the like in the presence of a polymerization catalyst and plasticizer. SOLUTION: This copolymer is obtained by ring-opening copolymerization of (A) a lactide (e.g. L-lactide and D-lactide), (B) 100 pts.wt. of a cellulosic ester or ether (e.g. acetyl cellulose and methyl cellulose) in the presence of (C) preferably 0.001 to 0.5 pts.wt. of a polymerization catalyst (e.g. tin octylate) and (D) 10 to 100 pts.wt. of a plasticizer (e.g. dimethyl phthalate, ethyl phthalyl ethyl glycolate). It is preferable that the component A/component B wt. ratio is 99/1 to 70/30. It is also preferable that the ring-opening copolymerization is effected by adding the component C to the mixture of the component A and component B plasticized with the component D, prepared by melting these components at 100 to 180 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-molecular-weight lactic acid-based copolymer which has good transparency and hue and can be used in various molding methods.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protection of the natural environment, biodegradable polymers that can be decomposed in the natural environment and molded products thereof have been demanded. . In particular, the lactic acid-based polymer has a glass transition point of 60 ° C and a melting point of 170 to 180 ° C, and has high thermal stability and excellent transparency.・ It is expected to spread. On the other hand, cellulose and cellulose derivatives such as cellulose esters and cellulose ethers have long been used in filters and molded products as naturally-degradable resins derived from natural polymers, but they have been used as general-purpose resins with improved moldability. Research is also being actively conducted.

[0003] JP-A-59-86621 and JP-A-6-86621
JP-A-212422 describes a method for producing a copolymer in which acetyl cellulose and lactone are uniformly melt-mixed and then reacted using a polymerization catalyst in order to improve the processability of the cellulose derivative. . For example, when polycaprolactone is used as a lactone, the glass transition point of polycaprolactone is −60 ° C., which is an effective means as a soft segment used for rigid cellulose molecules. However, the melting point of polycaprolactone is 60 ° C., and it is difficult to achieve sufficient thermal stability and processing characteristics as a general-purpose resin.

Japanese Patent Application Laid-Open No. 4-275301 discloses Japanese Patent Application Laid-Open Nos. 59-86621 and 60-212422.
In the same production method as in the above publication, a copolymer of about 20% of caprolactone and acetylcellulose is produced, and the physical properties of the copolymer are described. This product was developed mainly for paint resins, and in addition to solution viscosity, solubility in solvents and compatibility with other resins have been investigated, but the resulting copolymer itself has been studied. The mechanical properties etc. are unknown. However, even in the case of the highest solution viscosity described in the comparative example, the solution viscosity in a 20% acetone solution was 1%.
Since it is only 500 cp / 25 ° C., it is presumed that its use as a general-purpose resin such as extrusion molding and injection molding is difficult.

Further, when this production method is used, it takes a long time to obtain a uniform melt-mixing, and it is colored pale yellow to brown to deteriorate the appearance as a resin. In addition, the resin after polymerization is isolated and purified using a solvent fractionation method to remove unreacted substances, and it is difficult to mass-produce the resin at low cost.

JP-A-6-287279 discloses that ring-opening copolymerization of lactide and a cellulose ester or cellulose ether is carried out in the presence of an esterification catalyst for the purpose of transparency, decomposability and thermoplastic properties. A manufacturing method is described. Since polylactic acid has a high thermal stability and a good moldability by itself, the addition reaction of lactide to cellulose chains is a very effective method.
However, the polylactic acid chain, which is a component of the obtained copolymer, is also a rather rigid molecular chain.In addition, although the polylactic acid alone has strength, it is characterized by being brittle. A sufficient plasticizing effect cannot be obtained. In fact,
JP-A-287279 discloses a method of further imparting thermoplasticity by adding a plasticizer during post-processing after polymerization or during molding.

Further, the copolymers obtained by the production method of Japanese Patent Application Laid-Open No. Hei 6-287279 were severely colored, and all of them were dry. As a cause of this coloring, when lactide is used, the above-mentioned JP-A-59-86621, JP-A-60-212422, and JP-A-6-28
Unlike the lactone used in US Pat. No. 7,279, the melting point of lactide is considered to be as high as 120 ° C. That is, in the copolymerization reaction, a higher temperature and longer time are required to obtain a uniform molten state with the cellulose derivative than in the case of using lactone. As a result, it is considered that coloring of the reaction product is inevitable.
In addition, in this production method, as illustrated, unreacted lactide monomer is also contained in an amount of 2 to 3%, and it is easily imagined that the post-processing, use, or storage causes deterioration of the molded article. You.

Further, Japanese Patent Application Laid-Open No. 9-143253 describes a production method for obtaining a copolymer of a polysaccharide such as a cellulose ester and a hydroxy acid such as lactic acid and an aliphatic polyester. The obtained resin is excellent in mechanical properties such as flexibility, but is substantially a production method by direct polymerization in a solvent using lactic acid as a starting material. Unlike the method for producing a copolymer using lactide described above, since the reaction proceeds in the dehydration reaction,
During the reaction process, advanced technology and large-scale equipment for removing water are required. Furthermore, the reaction is performed in a solvent, and when industrial production is performed, not only a large-scale processing apparatus is required for the copolymerization reaction itself for the solvent treatment used, but also for reuse of the used solvent. Requires extensive equipment.

As described above, a method for copolymerizing lactide at the hydroxyl terminal of cellulose molecules has been studied, but a method for easily producing a copolymer satisfactory as a general-purpose resin has not been developed. It is the current situation.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to make a copolymer of lactide and a cellulose ester or a cellulose ether react in a short period of time and uniformly, so that it is transparent, colorless and has a good hue. Provided is a method for easily producing a lactic acid-based copolymer capable of controlling plasticity.

[0011]

Means for Solving the Problems In order to solve such problems, the present inventors have made intensive studies and found that lactide and
By copolymerizing a cellulose ester or a cellulose ether and a plasticizer in the presence of a polymerization catalyst, a method for producing a copolymer that is transparent, has no coloration, has excellent hue, and can easily control plasticity has been found.

That is, the present invention is characterized in that lactide (A) and cellulose ester or cellulose ether (B) are subjected to ring-opening copolymerization in the presence of a polymerization catalyst (C) and a plasticizer (D). This is a method for producing a system copolymer.

In the present invention, the cellulose ester or the cellulose ether (B) is added with a plasticizer (D) in advance.
A method for producing a lactic acid-based copolymer, characterized by using a product plasticized in (1).

[0014] Lactide (A) and cellulose ester and / or cellulose ether (B) used in the present invention.
Is from 99/1 to 70/30.

The amount of the plasticizer (D) for plasticizing the cellulose ester and / or cellulose ether (B) is 10 to 100 parts by weight based on 100 parts by weight of the cellulose ester and / or cellulose ether (B). .

The plasticizer (D) used in the present invention includes phthalic acid ester, adipic acid ester, glycolic acid derivative,
It is a single or plural mixture selected from ether ester derivatives and glycerin derivatives.

The plasticizer (D) is dimethyl phthalate, diethyl phthalate, ethylphthalylethyl glycolate,
It is a single or plural mixture selected from triethylene glycol diacetate, ether ester, tributyl acetyl citrate, and triacetin.

The amount of the plasticizer (D) is 10 to 100 parts by weight of dimethyl phthalate and / or 10 to 100 parts by weight of diethyl phthalate based on 100 parts by weight of the cellulose ester and / or cellulose ether (B). is there.

Alternatively, the plasticizer (D) is 10 to 100 parts by weight of the ether ester based on 100 parts by weight of the cellulose ester and / or the cellulose ether (B).

The polymerization catalyst (C) used in the present invention is added in an amount of 0.001 to 0.5 with respect to 100 parts by weight of lactide.
Parts by weight.

In the present invention, the lactide (A) and the cellulose ester and / or cellulose ether (B) plasticized with the plasticizer (D) are melt-mixed at 100 to 180 ° C., and then the polymerization catalyst (C) is added. The present invention relates to a method for producing a lactic acid copolymer which is subjected to ring-opening copolymerization.

Further, the present invention relates to a degradable copolymer obtained by the production method of the present invention and a molded product thereof.

Hereinafter, the lactide (A), cellulose ester or cellulose ether (B), catalyst (C), and plasticizer (D) used in the present invention will be described in order.

Lactide (A) used in the present invention is a compound obtained by cyclic dimerization of lactic acid.
There are three kinds of lactides: L-lactide composed of lactic acid, D-lactide composed of D-lactic acid, and meso-lactide composed of L-lactic acid and D-lactic acid.

A copolymer containing only L-lactide or D-lactide can be crystallized to obtain a high melting point copolymer. In the copolymer of the present invention, even better properties can be obtained by combining these three lactides.

Among the cellulose ester or cellulose ether (B) used in the present invention, examples of the cellulose ester include acetyl cellulose, acetyl butyl cellulose, acetyl propionyl cellulose, propionyl cellulose, acetyl phthal cellulose, cellulose nitrate and the like. . Among these, acetylcellulose, acetylpropionylcellulose, or propionylcellulose is preferable as having good biodegradability and being industrially easily available. Further, acetylcellulose is preferable as the cellulose ester that is industrially available at low cost.

Since acetylcellulose is obtained by aging triacetylcellulose to obtain diacetylcellulose, any acetylcellulose can be industrially available with any degree of acetyl substitution. The substitution degree of the acetyl cellulose used in the present invention may be any one. In the present invention, since a material plasticized with a plasticizer in advance is used, it is not necessary to consider solubility in a solvent and the like. Even in triacetyl cellulose having a degree of substitution of 3.0, all hydroxyl groups of cellulose are completely substituted. However, it is considered that the acetyl group undergoes a substitution reaction during the reaction with lactide, and a high molecular weight copolymer can be obtained.

Although the molecular weight of acetyl cellulose is not particularly limited, it is preferable to use acetyl cellulose having an average degree of polymerization of 50 or more for the purpose of obtaining a high molecular weight copolymer. In particular, when an average degree of polymerization of 100 or more is used, a copolymer having excellent thermal stability can be obtained, and a copolymer having a higher glass transition point than a homopolymer of polylactic acid can be obtained. .

As the cellulose ether, methyl cellulose, ethyl cellulose, methyl ethyl cellulose, cyanoethyl cellulose, benzyl cellulose, hydroxypropyl cellulose and the like can be used.

These cellulose esters and cellulose ethers may be used alone or as a mixture of a plurality of celluloses.

The weight ratio of lactide to cellulose ester and / or cellulose ether is 99/1 to 7
0/30 is preferred. If the ratio is more than 99/1, the obtained lactic acid-based copolymer cannot exhibit the characteristics of introducing a cellulose derivative into a polylactic acid chain. If the ratio is less than 70/30, the rigidity of the cellulose chain will be emphasized too much and the moldability will be poor. A more preferred weight ratio is from 97/3 to 70/30.

Examples of the polymerization catalyst (C) used in the present invention include metals such as tin, zinc, lead, titanium, bismuth, zirconium, and germanium, which are generally known as ring-opening polymerization catalysts for cyclic esters, and derivatives thereof. , For these derivatives, especially metal compounds, carboxylate salts,
Carbonates, oxides and halides are preferred. Specific examples include tin chloride, tin octylate, zinc chloride, zinc acetate, lead oxide, lead carbonate, titanium chloride, alkoxytitanium, germanium oxide, zirconium oxide, and the like, and particularly obtain a high molecular weight copolymer. Is preferably tin octylate.

The amount of the polymerization catalyst (C) added is preferably 0.0001 to 0.5% by weight based on the weight of the lactide (A). Although the amount depends on the reaction temperature, if the amount is less than 0.0001% by weight based on the lactide (A), the reaction time is significantly increased, and the productivity is reduced. If the content is more than 0.5% by weight, the copolymerization reaction proceeds rapidly, but it is not preferable because it causes coloring.

The plasticizer (D) used in the present invention includes:
In general, a plasticizer used for plasticizing cellulose or a cellulose derivative, or plasticizing polylactic acid or a modified product of polylactic acid can be used. As examples of such plasticizers, many plasticizers widely used for vinyl chloride polymers can be used, but preferably selected from phthalic acid esters, adipic acid esters, glycolic acid derivatives, ether ester derivatives, and glycerin derivatives. Alternatively, a single or multiple mixtures can be used.

More specifically, the plasticizer (D) is selected from the group consisting of dimethyl phthalate, diethyl phthalate, ethyl phthalyl ethyl glycolate, triethylene glycol diacetate, ether ester, tributyl acetyl citrate and triacetin. Or a mixture of a plurality is preferred.

The amount of the plasticizer (D) is from 10 to 100 parts by weight, preferably from 20 to 8 parts by weight, per 100 parts by weight of the cellulose ester and / or cellulose ether (B).
0 parts by weight. If the amount of the plasticizer is less than 10 parts by weight, the softening temperature of the cellulose derivative cannot be sufficiently lowered, and as a result, a uniform copolymerization reaction with lactide (A) cannot be performed. If the amount is larger, the efficiency of the copolymerization reaction is reduced. Specifically, for example, as an example of a composition effective for plasticizing acetyl cellulose, 10 to 100 parts by weight of dimethyl phthalate and / or 10 to 100 parts by weight of diethyl phthalate are used with respect to 100 parts by weight of acetyl cellulose. Can be. Alternatively, similarly, triacetin and / or triethylene glycol diacetate may be used.
By using these plasticizers (D), it is possible to lower the softening temperature of acetyl cellulose while maintaining its transparency and hue. As a result, the color of the copolymer with lactide can be kept good, and a sufficient plastic effect can be imparted to the molded article.

Further, the plasticizer (D) was used as an ether ester with respect to 100 parts by weight of cellulose ester and / or cellulose ether (B) as RS10 manufactured by Asahi Denka Kogyo KK.
By using 10010 to 100 parts by weight, the softening temperature of acetylcellulose can be lowered, and at the same time, the color of the copolymer with lactide can be kept good, and the molded article can have a sufficient plasticizing effect.

Next, the manufacturing method will be described in order. A mixture of lactide (A) and cellulose ester or cellulose ether (B) previously plasticized with a plasticizer (D) is melt-mixed, and a polymerization catalyst (C) is added to carry out a copolymerization reaction.

As a method of plasticizing the cellulose ester or cellulose ether (B) with the plasticizer (D), a known method can be used. For example, dimethyl phthalate is added to 100 parts by weight of the cellulose ester or cellulose ether (B). 10 to 50 parts by weight and diethyl phthalate
It is obtained by adding 50 parts by weight, stirring and mixing at 90 ° C. for 6 hours under a nitrogen atmosphere, and then melt-mixing by extrusion at 200 ° C. The plasticized cellulose ester or cellulose ether is dried under reduced pressure at a temperature range in which the plasticizer does not evaporate, for example, at 70 ° C., and is dried to be used in a polymerization reaction.

Lactide (A) and cellulose ester or cellulose ether (B) are preliminarily mixed with a plasticizer (D).
When melt-mixing the plasticized material in the above, the mixing is performed in a dry nitrogen stream in order to prevent moisture from being mixed, for example, at 90 ° C. The melting temperature is preferably equal to or higher than the softening temperature of the plasticized cellulose ester or cellulose ether or the melting temperature of lactide (A). If the melting temperature is too high, the copolymerization reaction such as decomposition of lactide (A) is inactive. Since it becomes a cause of coloring of the obtained copolymer, specifically, it is preferable to carry out in the range of 80 to 180 ° C.

When the lactide (A) and the cellulose ester or cellulose ether (B) previously plasticized with the plasticizer (D) are melt-mixed, the polymerization catalyst (C) can be added at the same time. is there. For example,
When a biaxial horizontal reactor is used for the polymerization reaction, lactide (A), cellulose ester or cellulose ether (B) previously plasticized with a plasticizer (D), and a polymerization catalyst (C) are simultaneously charged. Alternatively, only the polymerization catalyst (C) may be charged from the middle of the reactor. In any case, cellulose ester or cellulose ether (B) is plasticized in advance, and lactide (A)
And a uniform polymerization reaction can be obtained.

The polymerization reaction is carried out at a temperature in the range of from 120 to 220 ° C. When the reaction temperature is lower than 120 ° C., the reaction does not proceed sufficiently, and the reaction at a temperature higher than 220 ° C. promotes the decomposition of lactide (A) to cause coloring, and many unreacted substances remain, and the copolymer is left unreacted. And the physical properties are also deteriorated. When a biaxial horizontal reactor is used, for example, when the reaction is carried out at 180 to 220 ° C., the residence time is 5 to 20 minutes, and the reaction proceeds sufficiently, depending on the relationship with the reaction temperature. A copolymer having a molecular weight can be obtained.

The obtained copolymer contains a plasticizer (D) used for plasticizing the cellulose ester or cellulose ether (B), and is a thermoplastic resin having flexibility. The molding temperature of this copolymer can be set lower than that of polylactic acid alone, and there is little molecular degradation during molding, and it is difficult to color, and a transparent molded article can be obtained. In addition, since the molding temperature can be set low, the cooling time after molding can be shortened, the releasability is improved by the contained plasticizer, and good moldability is exhibited.

The flexibility of the copolymer can be controlled by appropriately changing the composition and amount of the plasticizer (D) used.

Further, after the reaction is completed or after the reaction is completed, the unreacted lactide monomer remaining about 1 to 3% can be removed by exposing it to a molten state under reduced pressure, and the type of the plasticizer (D) is selected. Thereby, the plasticizer (D) can be removed simultaneously with the lactide monomer. Alternatively, a certain amount of plasticizer can be left to impart flexibility to the copolymer.

As a specific method of the decompression treatment, the latter half of the biaxial horizontal reactor is set at 200 to 220 ° C. and 1 to 50 ° C.
It is possible to maintain the pressure at Torr, and to retain and devolatilize for 3 to 15 minutes. The copolymer from which the lactide monomer and the plasticizer (D) have been removed in this way greatly reduces flexibility and appears brittle, but can be obtained with excellent pulverizability.

Polylactic acid alone is liable to be fused by heat generated during the pulverization process, and is inferior in pulverizability. However, since rigid cellulose molecules are introduced, the pulverizability is improved, and a finely pulverized product can be easily obtained. For example, using a commercially available ordinary plastic crusher, the diameter is easily 100 μm.
The following ground products can be obtained. Furthermore, diameter 1μm
The following ultra-fine pulverization is sufficiently possible without requiring a special cooling treatment.

This is also excellent in thermal stability and can be used for electrophotographic toners and the like. When it is used as a raw material for electrophotography, it can be used by being melt-blended with an existing plastic raw material. In this case, by treating the used electrophotographic raw material with an alkali, the copolymer is rapidly dissolved in an alkali solution, and can be easily separated and purified from an existing plastic raw material.

Further, it can be easily melt-blended with paper powder, wood powder, or other pulverized cellulosic products. The reason for this is that, by using the copolymer obtained in the present invention, unlike polylactic acid alone, the compatibility with paper powder, wood powder, or other pulverized cellulose products is greatly improved. It is considered that this contributes to the fact that the powders can be set in a uniform state in advance. Due to the nature of the blended raw materials, the resulting blends can be used for molded products such as trays that come into contact with food, as well as packaging and packing materials, as well as for outdoor use applications that are difficult to collect, such as road slope protection. It is effective.

The copolymer of the present invention can be prepared in a known reaction vessel in addition to the above-described two-axis horizontal reaction apparatus.
A vertical reaction vessel or a horizontal reaction vessel provided with a shaft or a plurality of shaft stirrers, a horizontal reaction vessel provided with a scraping blade of one or more shafts, or a kneader of one or more shafts, 1
A single or multiple-screw extruder or other reactor may be used alone, or a plurality of reactors may be connected in series or in parallel.

The copolymer prepared according to the present invention has good biodegradability as compared with polylactic acid. This is presumably because the cellulose component has excellent affinity for water, and hydrolysis proceeds more easily than polylactic acid. This contributes to waste reduction after use of the copolymer and in the production process. In particular, it has excellent decomposability in compost, and can be decomposed in several months until the external shape is not maintained.

Further, the copolymer of the present invention can be variously modified by adding a secondary additive. Examples of secondary additives include ultraviolet absorbers, pigments, colorants, various fillers, electrostatic agents, release agents, fragrances, antibacterial agents, nucleating agents, stabilizers such as antioxidants and regulators, and the like. , And other similar ones. Furthermore, it is also possible to add and use a plasticizer as a secondary plasticizer as needed.

In the present invention and the following Examples and Comparative Examples, the weight average molecular weight of the polymer is a value measured by GPC analysis in terms of polystyrene, and the melting point is a value measured by a scanning differential calorimeter (DSC).

[0054]

EXAMPLES (Plastified acetylcellulose A-1 to H-1)
Preparation) Diacetylcellulose (“Flakes” manufactured by Teijin Limited) or triacetylcellulose (“Triacetylcellulose” manufactured by Aldrich) was pre-dried at 120 ° C. for 3 hours, and 100 parts by weight of a plasticizer shown in Table 1 was added. And 90 to 11 under a nitrogen atmosphere using a biaxial kneader.
After mixing at 0 ° C. for 6 to 8 hours, the mixture was charged into a twin-screw extruder set at a temperature of 180 to 200 ° C. and allowed to stay there for 5 minutes, cooled with water, pelletized, and plasticized acetylcellulose A-1.
An H-1 pellet was obtained. These pellets are 70
It was preliminarily dried at 5 ° C. under reduced pressure for 5 hours and used in the following experiments.

[0055]

[Table 1] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. (Example 1) Lactide (L-lactide manufactured by Shimadzu Corporation)
1.9 kg plasticized acetylcellulose A-1 0.1
kg, 1.9 g of tin octylate as a polymerization catalyst was continuously charged into a twin-screw extruder, and retained at 190 ° C. for 10 minutes.
After the reaction, the strand was taken out as a strand, cooled with water, and pelletized to obtain 1.9 kg of a uniform copolymer A-2.
The pellets of the copolymer A-2 were transparent, and no coloring was observed.

After dissolving the copolymer A-2 in chloroform,
As a result of GPC analysis, the residual lactide monomer, and dimethyl phthalate and diethyl phthalate as plasticizers were not detected, the weight average molecular weight was 701,800, and a copolymerization reaction was performed. It has been found. As a result of DSC measurement, the glass transition point was 61.
The melting point was 2 ° C and 173 ° C.

Example 2 Lactide (L-Lide manufactured by Shimadzu Corporation)
Lactide) 1.7 kg plasticized acetylcellulose A
-1 0.3 kg, tin octylate as polymerization catalyst
8 g was reacted in the same manner as in Example 1 to obtain a copolymer A-3.
1.9 kg were obtained. The pellet of the copolymer A-3 was transparent and hardly colored.

The copolymer A-3 was prepared in the same manner as in Example 1.
As a result of GPC analysis after reprecipitation, residual lactide monomer and dimethyl phthalate and diethyl phthalate as plasticizers were not detected, and the weight average molecular weight was 434,800.
was. As a result of DSC measurement, the glass transition point was 58.2.
° C, melting point was 163 ° C.

Example 3 Lactide (L-Lide manufactured by Shimadzu Corporation)
Lactide) 1.6 kg plasticized acetylcellulose C
-1 0.4 kg, tin octylate as polymerization catalyst
Except that 6 g was used, the reaction was carried out in the same manner as in Example 1 to obtain 1.9 kg of a copolymer C-2, which was analyzed. The pellets of the copolymer C-2 were transparent and no coloring was observed.

The copolymer C-2 was similarly reprecipitated and subjected to GPC.
As a result of the analysis, the residual lactide monomer and the plasticizers dimethyl phthalate and diethyl phthalate were not detected, and the weight average molecular weight was 366,900. As a result of DSC measurement, the glass transition point was 55.9 ° C. and the melting point was 168 ° C.
was.

(Example 4) Plasticized acetylcellulose D
Other than using -1, the temperature of the reactor was set at 187 ° C,
The reaction was carried out in the same manner as in Example 3 to obtain copolymer D-2 1.9.
kg was obtained and analyzed.

The copolymer D-2 was similarly reprecipitated and subjected to GPC.
As a result of analysis, no residual lactide monomer or plasticizer was detected, and the weight average molecular weight was 483,200.
As a result of DSC measurement, the melting point was 168 ° C.

(Example 5) Plasticized acetylcellulose E
Except for using -1, the same reaction as in Example 4 was carried out to obtain a copolymer E-2, which was analyzed.

The copolymer E-2 was similarly reprecipitated and subjected to GPC.
As a result of the analysis, no residual lactide monomer or plasticizer was detected, and the weight average molecular weight was 471,900.
As a result of DSC measurement, the melting point was 167 ° C.

(Example 6) Plasticized acetylcellulose F
Except for using -1, the same reaction as in Example 4 was carried out to obtain a copolymer F-2, which was analyzed.

The copolymer F-2 was similarly reprecipitated and subjected to GPC.
As a result of the analysis, no residual lactide monomer or plasticizer was detected, and the weight average molecular weight was 454,200.
As a result of DSC measurement, the melting point was 163 ° C.

(Example 7) Plasticized acetylcellulose G
Except for using -1, the same reaction as in Example 4 was carried out to obtain a copolymer G-2, which was analyzed.

The copolymer G-2 was similarly reprecipitated and subjected to GPC.
As a result of analysis, no residual lactide monomer or plasticizer was detected, and the weight average molecular weight was 284,400.
As a result of DSC measurement, the melting point was 158 ° C.

(Example 8) Plasticized acetylcellulose H
Other than using -1, the temperature of the reactor was set at 185 ° C,
The reaction was carried out in the same manner as in Example 3 to obtain copolymer H-2 1.9.
kg was obtained and analyzed.

The copolymer H-2 was reprecipitated in the same manner and GPC
As a result of analysis, no residual lactide monomer and plasticizer were detected, and the weight average molecular weight was 327,100.
As a result of DSC measurement, the melting point was 164 ° C.

Example 9 Lactide (L-Lide manufactured by Shimadzu Corporation)
Lactide) 90 g of plasticized acetylcellulose B-1
10 g, 0.2 g of tin octylate as a polymerization catalyst
After adding to the shaft kneader and reacting at 190 ° C for 12 minutes,
Further, a two-axis kneader capable of reducing pressure is connected in series, and
At 0 ° C., the pressure was reduced to 3 Torr, and after a residence time of about 8 minutes,
It was recovered as a strand, and was cooled with water and pelletized to obtain an almost colorless and transparent copolymer B-2.

As a result of GPC analysis of the copolymer B-2, no residual lactide monomer and no dimethyl phthalate and diethyl phthalate as plasticizers were detected, and the weight average molecular weight was 675,400. Its melting point was 172 ° C.

The pulverizability of the copolymer B-2 was good, and the copolymer B-2 was crushed into pieces only by lightly picking with a nipper. This copolymer B
-2 Using about 30 g, the mixture was crushed in a commercially available small plastic crusher for about 2 minutes. As a result, a pulverized product having an average particle size of about 33 μm was obtained.

(Example 10) Lactide (L manufactured by Shimadzu Corporation)
-Lactide) 70 g of plasticized acetylcellulose B-
130 g, tin octylate 0.15 g as polymerization catalyst
Was used to carry out a copolymerization reaction and degassing under reduced pressure in the same manner as in Example 9 to obtain an almost colorless and transparent copolymer B-3.

As a result of a GPC analysis of the copolymer B-3, no residual lactide monomer and no dimethyl phthalate and diethyl phthalate as plasticizers were detected, and the weight average molecular weight was 228,600. As a result of DSC measurement, the melting point was 166 ° C.

The pulverizability of the copolymer B-3 was good, and the copolymer B-3 was crushed into pieces only by lightly picking with a nipper. This copolymer B
In the same manner as in Example 9, using -3, a fine pulverized product having an average particle size of about 18 μm was obtained.

(Example 11) A copolymerization reaction and a vacuum deaeration treatment were carried out in the same manner as in Example 9 except that plasticized acetylcellulose G-1 was used, and a completely colorless and transparent copolymer G was used.
-3 was obtained.

As a result of a GPC analysis of this copolymer G-3, no residual lactide monomer or plasticizer was detected, and the weight average molecular weight was 215,400. DSC
As a result of the measurement, the glass transition point was 54.8 ° C. and the melting point was 154.
° C.

The pulverizability of the copolymer F-3 was also good, and the copolymer F-3 was crushed into pieces only by lightly picking with a nipper. This copolymer F
In the same manner as in Example 9, using -3, a fine pulverized product having an average particle size of about 12 μm was obtained.

Comparative Example 1 Lactide (L-Lide manufactured by Shimadzu Corporation)
(Lactide) 15 g of triacetylcellulose ("Triacetylcellulose" manufactured by Aldrich) and 85 g of tin octylate as a polymerization catalyst were added to 85 g of a biaxial kneader, reacted at 190 ° C. for 10 minutes, and then cooled with water. Collected. As a result, although the strand was colorless and transparent, a strand containing a lump of residue apparently containing triacetylcellulose was recovered.

Comparative Example 2 Lactide (L-Lide manufactured by Shimadzu Corporation)
(Lactide) 15 g of diacetylcellulose ("Flakes" manufactured by Teijin Limited) and 85 g of tin octylate as a polymerization catalyst were added to 85 g of a biaxial kneader, and reacted at 230 ° C for 12 minutes. As a result, a strand in which fine residues that clearly seemed to contain diacetyl cellulose remained was recovered.
This strand was also strongly colored and brownish.

From the above Examples and Comparative Examples, the present invention is a production method for obtaining a flexible molded article of a lactic acid-based copolymer having good moldability and a uniform reaction, and depending on the purpose of use, may be a plasticizer. It has been clarified that a copolymer excellent in pulverizability can be obtained by removing the.

[0083]

According to the present invention, it is possible to produce a uniform lactic acid-based copolymer in a short time under mild temperature conditions in which the cellulose derivative is not colored.

Claims (6)

[Claims] 1. A lactic acid-based copolymer characterized in that a lactide (A) and a cellulose ester or a cellulose ether (B) are subjected to ring-opening copolymerization in the presence of a polymerization catalyst (C) and a plasticizer (D). Manufacturing method. 2. The method for producing a lactic acid-based copolymer according to claim 1, wherein the cellulose ester or cellulose ether (B) is plasticized with a plasticizer (D) in advance. 3. The weight ratio of lactide (A) to cellulose ester and / or cellulose ether (B) is 99 /
3. The method for producing a lactic acid-based copolymer according to claim 1, wherein the ratio is 1 to 70/30. 4. The amount of the plasticizer (D) for plasticizing the cellulose ester and / or cellulose ether (B) is 10 to 100 parts by weight based on 100 parts by weight of the cellulose ester and / or cellulose ether (B). The method for producing a lactic acid-based copolymer according to claim 1 or 2, wherein 5. A lactide (A) and a cellulose ester and / or a cellulose ether (B) plasticized with a plasticizer (D) are melt-mixed at 100 to 180 ° C., and a polymerization catalyst (C) is added. The method for producing a lactic acid-based copolymer according to claim 1 or 2, wherein ring-opening copolymerization is performed. 6. A biodegradable copolymer obtained by the production method according to claim 1, and a molded article thereof.