JP3407519B2 - Aliphatic polyester composition and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high molecular weight aliphatic polyester copolymer which can be molded into a desired molded article by a general-purpose plastic molding method such as an injection molding method, a hollow molding method and an extrusion molding method, and a method for producing the same. It is about. More specifically, while having excellent biodegradability,
The present invention relates to an aliphatic polyester copolymer having a practically sufficient high molecular weight and satisfying product qualities such as thermal stability, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Since an aliphatic polyester copolymer obtained by polycondensing an aliphatic carboxylic acid and an aliphatic diol has biodegradability, its practical application as a general-purpose polymer substitute is attracting attention as environmental problems increase. ing. Particularly, an aliphatic polyester composed of succinic acid and 1,4-butanediol has relatively high strength and a melting point of 110 to 115 ° C.
Since it is relatively high, it can be put to practical use by increasing the number average molecular weight to 30,000 or more.

On the other hand, conventionally, it was industrially difficult to raise the number average molecular weight to 15,000 or more, but by copolymerizing an oxycarboxylic acid such as lactic acid, an aliphatic polyester copolymer having a number average molecular weight of 20,000 or more can be obtained. It has been found that a polymer can be easily obtained (JP-A-6-2070).
00). However, in order to use this aliphatic polyester copolymer as a general-purpose polymer substitute, it is necessary to set the number average molecular weight to 30,000 or more. However, in the above method, the number average molecular weight is increased and the biodegradability is increased. There was a problem that it decreased. Therefore, it is desired to further improve the biodegradability originally possessed by this aliphatic polyester copolymer.

[0004]

The object of the present invention is to maintain the physical properties of an aliphatic polyester copolymer obtained by copolymerizing an aliphatic carboxylic acid, an aliphatic diol and an aliphatic oxycarboxylic acid, while maintaining the original properties. It is to further improve the biodegradability of the copolymer.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have obtained an aliphatic carboxylic acid, an aliphatic diol and an aliphatic oxycarboxylic acid by copolymerization. The present inventors have found that the inclusion of fine particles having specific physical properties in the aliphatic polyester copolymer as a decomposition accelerator greatly improves the biodegradation rate of the obtained polyester composition, and has reached the present invention.

That is, the gist of the present invention is an aliphatic polyester copolymer obtained by copolymerizing an aliphatic carboxylic acid, an aliphatic diol, and an aliphatic oxycarboxylic acid, wherein the copolymerization copolymer is used as a decomposition accelerator. A biodegradable polyester composition having excellent degradability, which comprises 0.001 to 1% by weight of fine particles having a melting point higher than that of the coalescence and an average particle diameter of 20 μm or less with respect to the copolymer, and The manufacturing method is related.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The biodegradable polyester of the present invention is obtained by liquid phase polycondensation of an aliphatic dicarboxylic acid, an aliphatic diol and an aliphatic oxycarboxylic acid. The copolymer of the present invention is not particularly limited as long as it is such a three-component copolymer, but the copolymer of the present invention includes an aliphatic oxycarboxylic acid unit represented by the following formula (I) and an aliphatic diol unit represented by the following formula (II). And an aliphatic dicarboxylic acid unit represented by the following formula (III) is preferable.

[0008]

Embedded image (I) —O—R ¹ —CO— (II) —O—R ² —O— (III) —OC—R ³ —CO—

(Where R is¹, R²Is divalent aliphatic hydrocarbon water
Base, R³Is a direct bond or a divalent aliphatic hydrocarbon group) As an aliphatic dicarboxylic acid for obtaining such a copolymer
Is the formula, HOOC-R ³-COOH, (wherein R³Is straight
A bond or a divalent aliphatic hydrocarbon group, preferably
Is-(CH₂)_m-, Where m = an integer from 0 to 10,
It is preferable to use the one represented by (preferably an integer of 0 to 6).
You can

Specific examples thereof include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid and dodecanedioic acid. Succinic acid is particularly preferable from the viewpoint of physical properties of the resulting copolymer. Even if these are used alone,
You may use 2 or more types simultaneously. Preferred aliphatic diols in the present invention, wherein, HO-R ² -OH
(In the formula, R ² is a divalent aliphatic hydrocarbon group, preferably — (CH ₂ ) _n —, where n = an integer of 2 to 10,
Alternatively, a divalent alicyclic hydrocarbon group having 3 to 10 carbon atoms, preferably 4 to 6 carbon atoms can be used.

Specific examples thereof include ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol. From the viewpoint of physical properties of the obtained copolymer, 1,
4-Butanediol is particularly preferred. These may be used alone or in combination of two or more.

Preferred aliphatic oxycarboxylic acids in the present invention are represented by the formula: HO-R ¹ -COOH, (wherein
R ¹ is a divalent aliphatic hydrocarbon group, preferably a divalent chain aliphatic hydrocarbon group having 1 to 10 carbon atoms and optionally substituted with an alkyl group having 1 to 5 carbon atoms) There may be mentioned those represented. Specific examples thereof include ring-opened lactones such as lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, or caprolactone. When these optical isomers are present, they may be any of D-form, L-form and racemic form, and may be in the form of solid, liquid or aqueous solution.
Lactic acid is particularly preferred because of easy availability of raw materials. These may be used alone or in combination of two or more.

Further, another copolymerization component can be introduced into the aliphatic polyester copolymer of the present invention as long as the effects of the present invention are not impaired. Other copolymerization components include aromatic oxycarboxylic acids such as hydroxybenzoic acid, aromatic diols such as bisphenol A, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, or 3
Functional or higher aliphatic polyol, aliphatic polycarboxylic acid,
Aliphatic oxycarboxylic acid etc. are mentioned.

The amount of the aliphatic diol used is substantially equimolar with respect to the dicarboxylic acid content, but in general, there is distilling during the esterification reaction, so the amount used is 1 to 20 mol% in excess. It is desirable to do. The aliphatic oxycarboxylic acid is
Any of D-form, L-form and racemic form may be used, and the form is not particularly limited. The amount of the aliphatic oxycarboxylic acid is preferably 0.02 to 30 mol% with respect to the dicarboxylic acid component. It is particularly preferable to use lactic acid, and in this case,
An 85-92% aqueous lactic acid solution is preferred because of its ready availability. If the amount of lactic acid added is too small, the liquid phase polycondensation rate will decrease, and if it is too large, the mechanical strength of the resulting polymer will decrease, which is not preferable. The amount of lactic acid with respect to the dicarboxylic acid component is preferably 0.02 to 30 mol%, more preferably 0.5 to 20 mol%, and particularly preferably 1 to 10 mol%. The timing and method of adding lactic acid are not particularly limited as long as they are before the polycondensation reaction. For example, (1) a method of adding a catalyst in a state of being dissolved in an aliphatic oxycarboxylic acid solution in advance, (2) a catalyst when charging raw materials And the method of adding at the same time.

The production of the aliphatic polyester copolymer of the present invention comprising the aliphatic diol, the aliphatic carboxylic acid and a small amount of the aliphatic oxycarboxylic acid can be carried out by a known technique. The polymerization reaction at the time of producing the polyester copolymer can be set under appropriate conditions conventionally used, and is not particularly limited. In the aliphatic polyester copolymer of the present invention, the above raw materials are preferably used in the presence of a polymerization catalyst. As the type of catalyst, a catalyst used in ordinary polyester polymerization can be used, and among them, a germanium compound is preferable. The germanium compound is not particularly limited, and examples thereof include organic germanium compounds such as tetraalkoxy germanium and inorganic germanium compounds such as germanium oxide and germanium chloride. Because of price and availability
Germanium oxide, tetraethoxy germanium, tetrabutoxy germanium and the like are preferable.

The amount of this catalyst used is 0.001 to 3% by weight, more preferably 0.005% by weight, based on the amount of monomers used.
~ 1.5% by weight. The timing of adding the catalyst is not particularly limited as long as it is before polycondensation, but it may be added at the time of charging the raw materials or at the start of depressurization. It is particularly preferable that the catalyst is added at the same time as the aliphatic oxycarboxylic acid such as lactic acid when the raw materials are charged, or the catalyst is dissolved in the aliphatic oxycarboxylic acid and added.

Conditions such as temperature, time and pressure for producing the aliphatic polyester copolymer are set such that the temperature is 150 to 26.
The temperature is preferably 0 ° C, preferably 180 to 230 ° C, and the polymerization time is preferably 2 hours or longer, more preferably 4 to 15 hours. The degree of reduced pressure is 10 mmHg or less, preferably 2 mmHg or less. The composition ratio of the biodegradable polyester composition of the present invention requires that the molar ratio of the aliphatic diol unit of the formula (II) and the aliphatic dicarboxylic acid unit of the formula (III) be substantially equal. The aliphatic diol unit and the aliphatic dicarboxylic acid unit are each 35 to 4
It is good to select in the range of 9.99%, preferably 40 to 47.75%, and more preferably 45 to 49.5%.
The amount of the aliphatic oxycarboxylic acid unit of the formula (I) is 0.02.
It is preferable to select in the range of ˜30 mol%. If the aliphatic oxycarboxylic acid exceeds 30 mol%, the crystallinity will be lost, which is not preferable for molding, and if it is 0.02 mol% or less, the polymerization rate will decrease. The above range is preferably 0.5 to 20 mol%, and more preferably 1.0 to 10 mol%.

The number average molecular weight of the aliphatic polyester copolymer of the present invention is 10,000 to 200,000, preferably 30,000 to 1
It is 0,000. The present invention is characterized in that the above polyester copolymer contains fine particles having specific physical properties as a decomposition accelerator. The fine particles used as a decomposition accelerator in the present invention need to have no melting point at a temperature lower than the melting point of the aliphatic polyester copolymer as the main component. One of the reasons for this is as follows.

This type of aliphatic polyester copolymer is
First, since the surface is considered to be biodegraded by microorganisms and the like, the surface properties are expected to affect the biodegradation rate. Therefore, it is considered that when the aliphatic polyester copolymer is crystallized from the molten state in the presence of specific fine particles, the surface properties are different from those when no fine particles are used. For example, in the vicinity of the fine particles appearing on the surface, the crystal structure is different from that of the other portions, and it is easy for microorganisms involved in biodegradation to collect in that portion, and in the fine particles themselves present on the surface, It is also possible that the microorganisms involved in biodegradation are aggregated.

Therefore, if the melting point of the fine particles is lower than the melting point of the aliphatic polyester copolymer as the main component, the fine particles and the aliphatic polyester copolymer will be uniformly dispersed at the molecular level, resulting in the above surface. It is considered that local changes in structure may not appear. That is, in the present invention, the fine particles used as the decomposition accelerator are not completely dissolved and homogenized in the copolymer, but are uniformly dispersed in the aliphatic polyester copolymer in a fine particle state, It is possible to obtain a sufficient effect.

Based on the above idea, it is necessary that the fine particles used as the decomposition accelerator have a melting point higher than at least the melting point of the aliphatic polyester copolymer as the main component or do not melt. The melting point of the polyester copolymer to be used in the present invention is about 100 to 120 ° C., though it varies depending on the type of the copolymerization component and the ratio thereof.

In the present invention, the compound corresponding to the above fine particles may be either inorganic particles or organic particles, but inorganic particles are usually preferred. Specific examples of the inorganic particles include metal salts such as calcium carbonate, magnesium carbonate, calcium sulfate and barium sulfate, metal oxides such as titanium oxide, magnesium oxide and alumina, talc, kaolin, bentonite, mica and calcium silicate. Other examples include silicate compounds, such as glass fiber, boron nitride, asbestos, silica, quartz, carbon black, and other inorganic substances. Examples of the organic particles include tetrafluoroethylene, aromatic liquid crystal polyester, and polyethylene terephthalate having a melting point of 200 ° C. or higher. Among these, by using a silicate compound, especially talc,
The polyester composition obtained is excellent in biodegradability, and when added at the time of polycondensation, the rate of inhibiting the reaction is small and the adverse effect on mechanical properties is small, which is preferable.

The fine particles as the decomposition accelerator used in the present invention are required to have a particle size as small as possible because a large particle size causes a decrease in the mechanical strength of a molded article. The average particle size of the fine particles is 20 μm or less, preferably 10 μm, and more preferably 4 μm or less. The amount of fine particles added is 0.001 to 1% by weight, and more preferably 0.01 to 0.3% by weight. If the addition amount is too small, the effect of improving the biodegradation rate of the obtained polyester composition is lost, and if it is too large, the mechanical properties are deteriorated, or when the polycondensation reaction is carried out in the presence of fine particles, the reaction is inhibited. It is not preferable because it may occur.

In the present invention, generally, the biodegradation rate of the biodegradable polyester can be improved by mixing a smaller amount of the fine particles than the compounding amount of the filler with the synthetic resin. The method of incorporating the above-mentioned fine particles into the polyester copolymer is not particularly limited as long as the fine particles can be uniformly dispersed in the polymer, and specific methods include: A: aliphatic polyester copolymer And dry blend the particles. B: Compound the aliphatic polyester copolymer and the fine particles using a kneading machine or the like. C: Liquid phase polycondensation of the aliphatic polyester copolymer in the presence of fine particles. There is a method such as. In Method A, it is difficult to uniformly disperse the fine particles, and there is a high possibility that the fine particles will be separated from the pellets of the aliphatic polyester copolymer. In the method B, there is a concern that the manufacturing cost will increase due to the introduction of the compounding step and that the physical properties will deteriorate due to heat deterioration during the compounding. In C method,
Since the fine particles are present at the time of polycondensation, the fine particles are surely dispersed uniformly, and the aliphatic polyester copolymer is sufficiently adhered to the surface of the fine particles, so that improvement of mechanical properties can be expected. As a secondary effect, the presence of fine particles improves the crystallization rate of the aliphatic polyester copolymer,
It is possible to prevent pellet fusion problems in the pelletizing step after polycondensation and shorten the time required for the pelletizing step. Therefore, in order to uniformly disperse the fine particles, a method in which the aliphatic polyester copolymer is subjected to liquid phase polycondensation in the presence of the fine particles is preferable.

When the liquid phase polycondensation is carried out in the presence of the fine particles, the liquid phase polycondensation may be added at any time from the monomer preparation stage to the end of the liquid phase polycondensation, but the reaction system may be stirred during the polymerization reaction. Since the high shearing force generated has the effect of uniformly dispersing the fine particles, it is preferable to add the fine particles to the reaction system before the initiation of the polymerization reaction. Further, the fine particles may be added alone to the reaction system, but uniformly dispersed in at least one or more of the monomers used in the reaction,
It is preferably added as a slurry to the reaction system. In addition, ultrasonic treatment may be performed during uniform dispersion to improve the dispersibility of the fine particles.

As described above, the present invention provides an aliphatic diol,
A polymer composition obtained by copolymerizing an aliphatic dicarboxylic acid and an aliphatic oxycarboxylic acid and comprising a small amount of fine particles having a specific physical property value exhibits better biodegradability than the case of using an aliphatic polyester copolymer alone. It is based on that. The biodegradable polyester composition according to the present invention,
Films, laminate films, sheets, plates, stretched sheets, monofilaments, etc. are prepared by general-purpose plastic molding methods such as injection molding methods, blow molding methods and extrusion molding methods.
Multifilament, non-woven cloth, flat yarn, staple, streaked staple, split yarn, composite fiber,
It can be used for blow molded products such as blow bottles and foams.

Further, the polymer compound according to the present invention is
It is a polymer that has the property of being decomposed by bacteria in the soil and is extremely useful for environmental hygiene. Therefore, from now on, applications such as shopping bags, garbage bags, agricultural films, cosmetic containers, detergent containers, bleach containers, fishing lines, fishing nets, ropes, binding materials, surgical threads, sanitary cover stock materials, cold storage boxes, cushion materials, etc. Is expected to be used.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. The characteristic values in the following examples were measured by the following methods. (1) Number average molecular weight (Mn); measured by GPC method. Dissolve the sample in chloroform and use Tosoh GP
It was measured by polystyrene conversion using C HLC-8020. As the column, PLgel-10μ-MIX was used.

(2) Polymer composition: The composition was calculated by the ¹ H-NMR method from the area ratio of the obtained spectrum. (3) Thermal properties; DSC method (temperature rising temperature 20 ° C./min,
The melting point and the crystallization temperature were determined by maintaining the temperature at 180 ° C. for 5 minutes, cooling rate at 20 ° C./min, and measurement in a nitrogen atmosphere. (4) Biodegradability test: A field using soil in which mulch and compost were mixed at a ratio of 1: 1 was set outdoors, and a JIS No. 2 dumbbell piece punched out from a 1 mm thick sheet was embedded at a depth of about 7 cm. . After left in the field for a predetermined period from the start of burying, the test piece was taken out, the adhering soil was dropped, and the weight was measured to measure the weight remaining ratio. The water that was given to the field during the test was only natural rainfall, and no artificial water supply was performed.

Example 1 A succinic acid was added to a reaction vessel having a volume of 1 m ³ equipped with a stirrer, a nitrogen inlet tube, a heating device, a thermometer, and an auxiliary agent addition port.
8 kg, 119.3 kg of 1,4-butanediol, 90% of germanium oxide dissolved in 1% by weight in advance
7.67 kg of lactic acid aqueous solution, with an average particle size of 1.7 in advance
2.2 kg of 1,4-butanediol in which 220 g of μm talc was dispersed was charged. 1,4 for succinic acid
-Butanediol was 110 mol%, lactic acid was 6.4 mol%, and talc was 0.1 wt% with respect to the obtained polymer. While stirring the contents in a nitrogen sealed state,
The temperature was raised to 220 ° C. over 2 hours, and the reaction was carried out at this temperature for 30 minutes. After that, start depressurization and at the same time 230 ℃
The temperature was raised to 230 ° C., and polymerization was carried out at a temperature of 230 ° C. under a reduced pressure of 1.0 torr for 5 hours. After the completion of the polymerization, the obtained molten polymer was extracted in a strand shape, cooled in a cooling tank filled with cooling water at 30 ° C., and then pelletized by a strand cutter.

When the cooling time (the time for passing through the cooling water) was 8 seconds, the strands were completely crystallized and 0.8-1.0
It was possible to stably obtain g / 30 pellets, without fusion of the pellets, and 98% by weight of the pellets passed through a 4-mesh sieve. Mn of the obtained polymer was 4
The polymer composition by the 2,000, ¹ H-NMR method has a lactic acid unit of 4.6 mol%, a succinic acid unit of 47.7 mol%,
The 4-butanediol unit was 47.7 mol%, the melting point by DSC measurement was 108.2 ° C., and the crystallization temperature was 61.1 ° C. The results of the biodegradability test are shown in Table 1.

Comparative Example 1 1,4-Butanediol 121.5 without adding talc
The polymer was polycondensed in exactly the same manner as in Example 1 except that kg was charged, and the obtained molten polymer was extracted into strands, cooled in a cooling tank filled with cooling water at 30 ° C., and then a strand cutter. Pelletized.

Even when the cooling time was 8 seconds, the strands were not completely crystallized, 0.8 to 1.0 g / 30 pellets could not be stably obtained, and fusion of the pellets often occurred. . 65 wt% of the pellets passed through a 4 mesh screen. When the cooling time is 16 seconds, the strands are completely crystallized and the fusion of pellets is eliminated,
91 wt% of the pellets passed through a 4 mesh screen.

The Mn of the obtained polymer was 44,000,
^The polymer composition by ¹ H-NMR method was 4.5 mol% of lactic acid unit, 47.7 mol% of succinic acid unit, 47.8 mol% of 1,4-butanediol unit, and the melting point by DSC measurement was 1
The temperature was 08.4 ° C and the crystallization temperature was 48.0 ° C. The results of the biodegradability test are shown in Table 1. Control Example As a control example, a biodegradability test was performed using high-pressure low-density polyethylene. The results are shown in Table 1.

[0035]

[Table 1]

[0036]

INDUSTRIAL APPLICABILITY The present invention has the following effects and has an extremely high industrial utility value. 1. The biodegradation rate of the aliphatic polyester is improved without significantly impairing the physical properties. 2. The time required for the polymer extraction process is greatly reduced, and the deterioration of physical properties due to heat history is prevented. 3. It has the effect of stabilizing the pellet shape and drastically reduces troubles caused by fusion of pellets.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-3432 (JP, A) JP-A-5-70696 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 67/00-67/02

Claims (4)

(57) [Claims] 1. An aliphatic polyester copolymer obtained by copolymerizing an aliphatic carboxylic acid, an aliphatic diol, and an aliphatic oxycarboxylic acid, which has a melting point higher than the melting point of the copolymer as a decomposition accelerator. And has an average particle size of 2
Fine particles of 0 μm or less are added to the copolymer in an amount of 0.001
The biodegradable polyester composition having an excellent degradability of 1 to 1% by weight (provided that the content of fine particles in the composition is
Excludes cases where the amount is 0.5% by weight or more. ) . 2. The biodegradable polyester composition according to claim 1, wherein the fine particles used as a decomposition accelerator are inorganic powders. Wherein fine particles used as a decomposition accelerator Ru talc der 請 Motomeko 1 biodegradable polyester composition. 4. When copolymerizing an aliphatic carboxylic acid, an aliphatic diol, and an aliphatic oxycarboxylic acid, at any time from the monomer preparation stage to the end of liquid phase polycondensation,
As a decomposition accelerator, it was added the copolymer and the average particle size 20μm or less particulate polymer produced has a higher melting point than the melting point of the relative in a proportion of 0.001 wt%, the fine
Cormorant line liquid phase polycondensation in the presence of a child, a manufacturing method of a degradable excellent biodegradable polyester composition.