JP2694801B2 - Resin composition having improved mechanical properties and biodegradability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an aliphatic polyester having improved biodegradability and mechanical properties, particularly improved anisotropy in mechanical strength and heat shrinkability and improved biodegradability. System resin composition.

[0002]

2. Description of the Related Art In recent years, the amount of solid waste discharged from cities has become enormous, and is approaching the limit of waste disposal capacity. Plastic has always been pointed out as one of the causes of this solid waste.

As an ideal solution for plastic waste, degradable plastics that disappear in the natural environment are attracting attention. Degradable plastics include photodegradable plastics, in which the molecular chains of the polymer are cut by ultraviolet light, and biodegradable plastics, which are broken down by the action of enzymes released by bacteria and fungi outside the body.

[0004] However, in the case of photodegradable plastics, there is no expectation of an effect by burial treatment in the soil, and there is a risk of environmental pollution due to decomposition products.

Conventionally, biodegradable plastics include polyhydroxybutyrate (PHA), 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3H).
A random copolymer with V) is known. A resin composition in which a biodegradable plastic such as polycaprolactone (PCL) is blended with another resin is already known. For example, JP-A-4-139248 discloses ethylene-vinyl alcohol copolymers 5 to 99. A biodegradable resin composition is described, which comprises about 1% by weight and 95 to 1% by weight of an aliphatic polyester. Also, Japanese Patent Application Laid-Open No. Hei 5-8487
No. 6 discloses a biodegradable resin laminate composed of biodegradable polyester / polyvinyl alcohol / biodegradable polyester.

[0006]

Known biodegradable plastics are stable in the air, decompose in soil and water where bacteria are active, and the decomposition products are carbon dioxide. Although it has the advantage of being water, it still has problems that must be solved in terms of the properties and production of molded articles such as containers, which are the main uses of plastics.

That is, known biodegradable plastics have decomposition temperatures and molding temperatures of 180 to 190 ° C. and 170 to 1
Even if it is possible to manufacture a molded product by a casting method using a solvent such as chloroform because it is close to 75 ° C, there is a problem that melt molding is difficult. In order to improve the melt extrusion performance, it is necessary to add a large amount of a plasticizer to the container, and the container thus produced has an unfavorable effect that the plasticizer is extracted into water (internal article).

Further, the above-mentioned biodegradable plastics are expensive, and if they can be used by blending with other resins without impairing their biodegradability, both in terms of melt moldability and production cost. It is expected that significant advantages will be achieved. Conventionally, as another biodegradable polymer, a hydroxyl group-containing polymer has been known. However, since this polymer is water-soluble or poor in water resistance and has no melt moldability, it is used for this purpose. Can not be used.

The ethylene-vinyl alcohol copolymer found in the above-mentioned prior art has melt moldability and has an advantage that it is relatively excellent in water resistance among hydroxyl group-containing polymers. Similar to the hydroxyl group-containing polymer, the compatibility with the aliphatic polyester is not always sufficient, and when formed into a molded product, phase separation occurs, mechanical cracking occurs, and expected gas permeation resistance is obtained. It has the drawback of not having it.

That is, the conventional blend of the biodegradable saturated polyester resin and the hydroxyl group-containing resin has a lower mechanical strength in the transverse direction (TD) than that in the machine direction (MD) of the molded article. Although it has the anisotropy and thus tends to cause cracks in the MD direction, this defect has not yet been eliminated.

The same drawbacks also occur in the heat resistance of molded articles made of the above blends. That is, this molded product is
When immersed in warm water, the heat shrinkage in the transverse direction (TD) of the molded product is relatively small, but the heat shrinkage in the machine direction (MD) is remarkably large, resulting in anisotropic thermal deformation. This defect has not yet been resolved.

Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks in conventional biodegradable polyester compositions, and to eliminate the anisotropy of mechanical strength and the anisotropy of thermal properties of molded articles.
It is to provide a saturated polyester resin composition having a significantly improved biodegradability.

[0013]

According to the present invention, a saturated polyester resin mainly containing a hydroxyalkanoate unit, a thermoformable hydroxyl group-containing resin having a vinyl alcohol unit and an alkaline earth metal carbonate are contained. A resin composition having improved mechanical properties and biodegradability is provided. In the composition of the present invention, the saturated polyester resin is 25 to 8 based on 3 components.
5.5% by weight, hydroxyl group-containing resin is 2.5 to 45% by weight
And alkaline earth metal carbonate in an amount of 10 to 50% by weight.

[0014]

In the present invention, among various fillers, an alkaline earth metal carbonate is selected, which is used as a saturated polyester resin mainly containing a hydroxyalkanoate unit and a hydroxyl group-containing resin having a vinyl alcohol unit. Blend into the system. Thereby, the anisotropy of the mechanical strength and the anisotropy of the thermal property of the molded product can be eliminated, and the biodegradability can be remarkably improved.

FIG. 1 shows a molded article of a composition obtained by blending calcium carbonate in a blend of the saturated polyester resin and the hydroxyl group-containing resin according to the present invention, in terms of the number of blending parts of calcium carbonate, the machine direction (MD) and It is the graph which plotted the relationship with the yield point elongation% of a cross direction (TD).

The results show that, in the conventional blend, the elongation at yield in the transverse direction (TD) is
It is remarkably smaller than the elongation at yield point of D), and it is understood that this is a cause of easily causing cracks. On the contrary,
When calcium carbonate is incorporated into the blend according to the present invention, the yield point elongation in the transverse direction (TD) can be significantly improved without reducing the yield point elongation in the machine direction (MD). The elongation at yield point in the machine direction (MD) and transverse direction (TD) can be balanced at high values.

The above improvements according to the invention are unique to the combination of alkaline earth metal carbonate fillers with the above blends. For example, a composition containing 40 parts by weight of typical talc as a filler has a low elongation at yield point in the machine direction (MD) and transverse direction (TD) of 8% and 5%, respectively. Even in the case of mixing 40 parts by weight of a feldspar-based filler showing a high yield elongation among the fillers, the yield elongations in the machine direction (MD) and the transverse direction (TD) were 14% and 9%, All of them have cracks in the 180-degree bending test, as shown in Examples described later. Therefore, the unexpected effect of the present invention is clear.

When a molded product made of a blend of a saturated polyester resin and a hydroxyl group-containing resin is immersed in hot water at 70 ° C. for 60 minutes, the heat shrinkage in the machine direction (MD) is 25% and the transverse direction (TD). Has a thermal shrinkage of 0.4% and has a significantly large thermal shrinkage in the machine direction (MD) as compared with the transverse direction (TD) and is anisotropic. When 40 parts by weight of calcium carbonate is mixed in the product, the heat shrinkage ratio in the mechanical direction (TD) is 4.8.
%, The thermal shrinkage in the machine direction (MD) and the transverse direction (TD) can be balanced, and the thermal anisotropy can be eliminated.

FIG. 2 shows high density polyethylene (HDP
E) With reference to E), a biodegradable saturated polyester resin (PCL), a biodegradable saturated polyester resin (PCL / CaCO ₃ ) containing calcium carbonate, and a biodegradable saturated polyester resin containing calcium carbonate / hydroxyl group-containing resin for _{(PCL / PVA / CaCO 3)} , which is a graph plotting the relationship between the temperature and the storage modulus.

According to these results, the storage elastic modulus of the resin composition of the present invention shows that the biodegradable saturated polyester resin (PCL) or the biodegradable saturated polyester resin blended with calcium carbonate (PCL / CaCO) near room temperature. It is higher than that of ₃ ), and has an elastic modulus almost equal to that of high-density polyethylene (HDPE), and it can be seen that it has an excellent elastic modulus in a practical temperature range.

FIG. 3 shows high density polyethylene (HDP).
Biodegradable saturated polyester resin (PCL), blend of biodegradable saturated polyester resin and hydroxyl group-containing resin (PCL / PVA), and biodegradable saturated polyester resin blended with calcium carbonate / hydroxyl group About the containing resin (PCL / PVA / CaCO ₃ )
It is a plot of the relationship between the number of days elapsed and the residual weight ratio when buried in soil, and the slope indicates biodegradability.

According to these results, the resin composition of the present invention was compared with the biodegradable saturated polyester resin (PCL) and the blend of the biodegradable saturated polyester resin and the hydroxyl group-containing resin (PCL / PVA). It can be seen that it shows great biodegradability.

In the present invention, the effect of eliminating the anisotropy of the mechanical strength and the anisotropy of the thermal property of the molded product and remarkably improving the biodegradability is that a saturated polyester resin or a hydroxyl group-containing resin is used. And alkaline earth metal carbonate, which is not achieved even if either component is lacking. Although the explanation for this improvement is not necessarily restricted to this, the fact that anisotropy appears in the molded article made of the blend is considered to be related to the flow orientation of each resin component,
In the resin composition of the present invention, it is considered that the blended alkaline earth metal carbonate relaxes or homogenizes this flow orientation and forms a three-dimensionally stable and homogenized dispersion structure. The blend of the saturated polyester resin and the hydroxyl group-containing resin is excellent in biodegradability, but in the present invention, by dispersing the alkaline earth metal carbonate in the blended product, the alkaline earth metal carbonate The surface appears to be water absorbent, providing active sites for biodegradation.

In the resin composition of the present invention, of course, as in the known filler-containing resin composition, the addition of the alkaline earth metal carbonate filler reduces the cost of the molded product due to the increase in the amount.
The effects of improving the rigidity of the molded product and improving the dimensional stability of the molded product are naturally achieved.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(Saturated polyester resin) As the saturated polyester resin, any biodegradable saturated polyester resin mainly composed of hydroxyalkanoate units is used.
The saturated polyester resin should have at least a molecular weight capable of forming a film, and its number average molecular weight is generally 5 × 10 ^{4 to} 16 × 10 ⁴ , particularly 6 × 10 ⁴ .
^{It is} preferably in the range of ^{4 to} 15 × 10 ⁴ . Examples of suitable saturated polyester resins are poly-β-hydroxyalkanoates or aliphatic polylactones or poly-ω-hydroxyalkanoates or copolymers thereof.

The poly-β-hydroxyalkanoate has the following general formula (1):

Embedded image Wherein, R is a straight or a branched alkyl group, in represented by repeating units, for example, 3-hydroxybutyrate _{[R = -CH 3, 3HB]} , 3- hydroxyvalerate [R = -CH ₂ CH _3, 3HV], 3- hydroxy-caproate _{[R = - (CH 2)} 2 CH 3], 3- hydroxy-heptanoate _{[R = - (CH 2)} 3 CH 3], 3-
Hydroxyoctanoate [R =-(CH ₂ ) ₄ CH
_3], 3-hydroxy-nonanoate [R = - (CH _2)
5 CH ₃ ], 3-hydroxydecanoate [R =-(C
H ₂ ) ₆ CH ₃ ] and the like.

Suitable resins of this type include 3-hydroxybutyrate and other 3-hydroxyalkanoates,
Particularly, it is a copolymer obtained by copolymerizing with 3-hydroxyvalerate, and a copolymer containing these at a weight ratio of 95: 5 to 85:15, particularly 92: 8 to 88:12.

The aliphatic polylactone or poly-ω-hydroxyalkanoate is represented by the following general formula (2)

Embedded image In the formula, R is a linear or branched alkylene group, for example, γ-butyrolactone, δ-
One of repeating units such as valerolactone and ε-caprolactone
And a polymer composed of two or more species. Suitable examples of this type of resin are polycaprolactone or copolymers of caprolactone and other lactones.

In the present invention, a copolymer comprising a repeating unit of the formula (1) and a repeating unit of the formula (2) can be used. A suitable example of this copolymer is a copolymer of 3-hydroxybutyrate and γ-butyrolactone or ε-caprolactone. Also, a blend of two or more of the above-mentioned blends can be used.

(Hydroxyl group-containing resin) The hydroxyl group-containing resin used in the present invention has a vinyl alcohol unit in the molecular chain, that is, the following general formula (3).

Embedded image It contains a unit represented by the formula and is thermoformable.

The resin consisting only of the vinyl alcohol unit is difficult to thermoform, but an ethylene unit other than the above units in the molecular chain, that is, the following general formula (4)

Embedded image The unit represented by — [— CH ₂ —CH ₂ —] — ［(4) or a vinyl acetate unit, that is, the following general formula (5)

Embedded image By containing the unit represented by the formula, thermoforming becomes possible.

A suitable example of the hydroxyl group-containing resin is a partially saponified vinyl alcohol polymer, particularly a saponification degree of 40-8.
0% polyvinyl alcohol. The degree of polymerization of the vinyl alcohol polymer should be in the range of film formation, and is generally in the range of 300 to 800.

Another suitable example of a hydroxyl group-containing resin is an ethylene-vinyl alcohol copolymer. An ethylene-vinyl alcohol copolymer suitable in terms of melt moldability and gas barrier property has an ethylene content of 5 to 60 mol%, particularly 1
0 to 50 mol% and a saponification degree of 90% or more, especially 98
% Or more. The ethylene-vinyl alcohol copolymer used should have a molecular weight sufficient to form a film.

(Alkaline Earth Metal Carbonate) In the present invention, an alkaline earth metal carbonate is used among various fillers. Examples of the alkaline earth metal carbonate include carbonates such as calcium, magnesium, barium, and strontium. Of these, calcium carbonate and magnesium carbonate are preferred.

Calcium carbonate includes naturally occurring heavy calcium carbonate having a large specific gravity and light calcium carbonate which is synthetic and has a relatively small specific gravity. For the purpose of the present invention, the former is particularly preferable. The latter can of course be used. Similarly, magnesium carbonate includes naturally-occurring magnesium carbonate having a relatively large particle size and synthetically having a relatively small particle size and a homogeneous synthetic magnesium carbonate.
The former is particularly preferred, but of course the latter can also be used.

The particle size of the alkaline earth metal carbonate used is
There is no limitation as long as the dispersion is good, but in general, the median diameter is 0.5 to 10.0 μm, especially 1.0 to 2.0.
The range of μm is effective for eliminating anisotropy.
The alkaline earth metal carbonate-based filler may be an untreated ordinary one, but may be, for example, one treated with a surfactant, a fatty acid, a metal soap, or another dispersant. .

(Composition) In the composition of the present invention, the saturated polyester resin is 20 to 85.5% by weight, especially 2
The hydroxyl group-containing resin is preferably used in an amount of 5 to 60% by weight, and in an amount of 2.5 to 45% by weight, particularly 5 to 40% by weight. When the amount of the saturated polyester resin is smaller than the above range, or when the amount of the hydroxyl group-containing resin is larger than the above range, a problem occurs in compatibility or the biodegradability tends to decrease. Conversely, if the amount of the saturated polyester resin is larger than the above range, or if the amount of the vinyl alcohol polymer is smaller than the above range, the container is unsatisfactory in terms of gas permeability resistance and melt moldability. Becomes

On the other hand, the alkaline earth metal carbonate is preferably used in an amount of 5 to 50% by weight, particularly 10 to 40% by weight. If the amount of the alkaline earth metal carbonate is less than the above range, it is not effective for eliminating the anisotropy of the mechanical properties and the anisotropy of the thermal properties, and the biodegradability tends to decrease. There is. On the other hand, when the amount is more than the above range, the meltability tends to decrease, and the formed product tends to become brittle.

The resin composition of the present invention contains various colorants, fillers, inorganic or organic reinforcing agents, lubricants, plasticizers, leveling agents, surfactants, thickeners, depending on the application. A viscosity reducing agent, a stabilizer, an antioxidant, an ultraviolet absorber, a rust preventive and the like can be added. Further, in order to improve the dispersibility between resins, an ethylene-vinyl acetate copolymer may be blended.

In the resin composition of the present invention, there is no particular limitation on the method of blending the saturated polyester resin, the hydroxyl group-containing resin and the alkaline earth metal carbonate, but the saturated polyester resin and the hydroxyl group-containing resin may be mixed with the alkaline earth metal carbonate. It is convenient to prepare a salt-blended masterbatch and blend this masterbatch with the saturated polyester resin and the hydroxyl-containing resin.

According to the present invention, (A) a saturated polyester resin or (B) a vinyl alcohol-based polymer;
A masterbatch containing an alkaline earth metal carbonate is melted and kneaded as described above, blended with the remaining resin components, kneaded, and extruded or injected to form a packaging material or the like. Manufacture goods.

In the production of packaging materials and the like, one resin component blended with an ethylene-vinyl acetate copolymer,
It can also be fed to the extruder or the hopper of the extruder in the form of a mixture with the other resin component. This mixture may be a dry blend of the two or a melt blend. Dry blending can be performed using various mixers such as ribbon blender, conical blender, Henschel mixer, while melt blending is performed using a single or twin screw extruder, kneader, Banbury mixer, roll, etc. I can do it.

As the extruder, an extruder provided with an arbitrary screw is suitably used. As the die, a flat die or a ring die can be used. For example, a T-die method or an inflation film forming method is used for forming a film. In addition, by hollow-forming the extruded parison, a hollow-formed container such as a bottle, a tube, and a tank is formed.

As the injection machine, a known injection machine having an injection plunger or a screw is used, and the mixture is injected into an injection mold through a nozzle, a sprue, and a gate. As a result, the resin flows into the injection mold cavity and is cooled and solidified to obtain a molded product such as a packaging material.

(Uses) The composition of the present invention can be used as various plastic packaging containers, for example, bottles, cups, tubes, plastic cans, pouches, caps, etc., and as packaging materials for films, trays, etc., as well as containers, tanks and baskets. It is useful as a container for distribution, etc., and also as a structure, such as a pipe or a case.

[0046]

Next, the present invention will be described with reference to examples.

1) Sample Polycaprolactone H7S manufactured by Daicel Chemical Industries, Ltd. was used as a saturated polyester mainly composed of poly-ω-hydroxyalkanoate units, and as a thermoformable hydroxyl group-containing resin having vinyl alcohol units ( A partially saponified polyvinyl alcohol HMO5 manufactured by Kuraray Co., Ltd. was used. As an alkaline earth metal carbonate, Softon 1200 (Whiten SB (red)) manufactured by Shiraishi Calcium Co., Ltd.
It was used. Also, for comparison, as another inorganic filler,
FUJI-TALC PKP-80 and Shiraishi Kogyo MINEX10 were used. Further, a dispersant of metal stearate was also used as a dispersant of the above-mentioned inorganic filler.

2) Molding method 2-1) Manufacturing method of masterbatch Banbury mixer MIXTRON manufactured by Kobe Steel, Ltd.
BB-120 and Needex CM made by Color Metal
S-300-2250 (open roll extruder) was used. The rotation speed of the Banbury mixer was 30 rpm.
After kneading to a temperature range of 160 ° C. where the load of the rotary motor of the Banbury mixer was in a stable state, hot cutting was performed at 100 ° C. under air cooling using a Kneedex, and a supercooling treatment was performed to obtain a pellet master batch.

2-2) Sheet Molding An appropriate amount composition of polycaprolactone and partially saponified polyvinyl alcohol was dry blended to the above masterbatch, and Laboplast mill C molding machine (D-20-) manufactured by Toyo Seiki Seisakusho Co., Ltd. 20) and a sheet winder,
A sheet having a thickness of 1 mm and a width of 120 mm was prepared at a molding temperature of 170 ° C. and a screw rotation of 100 rpm.

2-3) Bottle Molding Using an ES65 type extruder (40φ) manufactured by Ikegai Co., Ltd., a molding temperature of 170 ° C., a screw rotation of 40 rpm, a mold temperature of 16 ° C. and a blow air pressure of 6 kg / cm ^{2 were used} . The columnar bottle was direct blow molded.

3) Measuring Method 3-1) Evaluation of Mechanical Properties A sheet piece dried under reduced pressure for 75 hours and a sheet piece left for 75 hours at 25 ° C. and 60% RH were bent at 180 ° and their cracking property was observed. Also, UCT manufactured by ORITEC
-5T type Tensilon 100kg load cell, chuck distance 30mm, pulling speed 500mm / min
The stress-strain curve was obtained at. The yield point elongation (%) was obtained from the obtained stress-strain curve results. ASTMD-1822 type was used as the shape of the measurement sample.

3-2) Evaluation of Decomposition and Degradation A 30 mm × 50 mm piece of the sheet molding was buried in soil. The sheet pieces were taken out 30 and 60 days after landfilling, washed with water, dried under reduced pressure for 75 hours, and precisely weighed using an analytical balance. The obtained results are from the initial weight ω ₀ and the weight after landfill ω ₁ (ω ₁
The weight residual ratio (%) was expressed as / ω ₀ ) × 100.

Example 1 Polycaprolactone (A) having a number average molecular weight of 130,000, 60% partially saponified polyvinyl alcohol (B) having a degree of polymerization of 500, and calcium carbonate (C) having an average particle size of 1.8 μm.
3 components of (A) :( B) :( C) = 12: 8: 80 were added to 3 kg of a dispersant mainly composed of calcium stearate per 1 kg of a weight ratio product, and they were kneaded with a Banbury mixer. After kneading with a Banbury mixer, pelletized master batch was continuously molded with Kneedex. Next, in the above masterbatch, the weight ratio (A) of two components of polycaprolactone (A) and partially saponified polyvinyl alcohol (B):
(B) = 60: 40 was added in an appropriate amount, and a sheet was formed by a Labo Plastomill sheet forming machine.

1) Mechanical Properties The mechanical properties of the above sheet molded product are shown in Table 1 and FIG. Table 1 shows the results of observation of cracks when bent 180 °, and FIG.
Is the yield point elongation (%) obtained from the stress-strain curve. From Table 1, polycaprolactone (A) and partially saponified polyvinyl alcohol (B) two component weight ratio is (A):
Cracks were observed in the sheet molded product of (B) = 60: 40. However, in the three-component system in which calcium carbonate (C) was mixed with the resin composition, no crack was observed in the sheet molded product. In Table 1 and FIG. 1, in the case of a sheet molded product composed of a two-component system in which the weight ratio of polycaprolactone (A) and partially saponified polyvinyl alcohol (B) is (A) :( B) = 60: 40, MD and TD are Anisotropy in yield point elongation was observed, but when calcium carbonate (C) was mixed with the resin composition, the anisotropy in yield point elongation was improved. Furthermore, this improved yield point elongation was characteristically constant with increasing calcium carbonate content.

2) Evaluation of Degradation and Degradation In addition to the sheet molded product of the above three-component composition, polycaprolactone (A) and partially saponified polyvinyl alcohol (B)
And a master batch having a calcium carbonate (C) three component weight ratio of (A) :( B) :( C) = 13: 7: 80 and (A) :( B) :( C) = 20: 0: 80. Then, an appropriate amount of a different mixed composition of polycaprolactone (A) and partially saponified polyvinyl alcohol (B) was added to this masterbatch to prepare a sheet molded product having different three-component composition ratios. These sheet moldings were used for the landfill test. Table 2 shows the three-component weight composition ratio of the sheet molding used in the landfill test and the weight residual ratio (%) after landfill.

From Table 2, the weight reduction amount of these sheet pieces is shown as a three-component system comprising polycaprolactone (A), partially saponified polyvinyl alcohol (B) and calcium carbonate (C)> polycaprolactone (A) and calcium carbonate. (C)
2 component system> polycaprolactone (A) and partially saponified polyvinyl alcohol (B) 2 component system> polycaprolactone simple substance (A). In particular, the two-component system consisting of polycaprolactone (A) and calcium carbonate (C) showed a weight loss independent of the calcium carbonate concentration, whereas polycaprolactone (A) and calcium carbonate (C) and partial ken The three-component system composed of the modified polyvinyl alcohol (B) showed a characteristic tendency of weight reduction that the weight reduction markedly increased as the concentration of calcium carbonate increased.

Example 2 Polycaprolactone (A) having a number average molecular weight of 130,000, 60% partially saponified polyvinyl alcohol (B) having a degree of polymerization of 500, and calcium carbonate (C) having an average particle size of 1.8 μm.
The weight ratio of the three components (A) :( B) :( C) = 13: 7: 80 3 g of a dispersant mainly composed of calcium stearate was added to 1 kg of the product, and the mixture was kneaded with a Banbury mixer. After kneading with a Banbury mixer, it was molded into a pellet-shaped master batch with Kneedex.

To this masterbatch was added polycaprolactone (A) and partially saponified polyvinyl alcohol (B) in a weight ratio of two components (A) :( B) = 65: 35, and a weight ratio of three components was (A). : (B) :( C) = 39: 21: 40
Direct blow molding of a 100 ml hollow bottle having a composition ratio was performed. The strength characteristics are the same as those in Example 1. By the way, after filling with white sand, it was tightly plugged and 10 pieces were dropped from a height of 1.2 m, but there were no objects to be broken.

Comparative Example 1 The same as Example 1 except that the inorganic filler was talc (PKP-80 manufactured by FUJI TALC Co., Ltd.) having an average particle size of 5.0 μm to 6.0 μm.

Comparative Example 2 MINEX (available from Minebea Co., Ltd.) having an average particle size of 2.3 μm was used as an inorganic filler.
Example 1 except that MINEX10 manufactured by Shiraishi Industry Co., Ltd. was used.
Is the same as

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

According to the present invention, among various fillers, an alkaline earth metal carbonate is selected, which has a saturated polyester resin mainly containing a hydroxyalkanoate unit and a vinyl alcohol unit. By blending with a system containing a hydroxyl group-containing resin, the anisotropy of mechanical strength and the anisotropy of thermal properties of molded products are eliminated, and the mechanical and thermal properties are significantly improved, and biodegradation is achieved. The property can also be significantly improved.

[Brief description of the drawings]

FIG. 1 shows a molded article of a composition obtained by blending calcium carbonate with a blend of a saturated polyester resin and a hydroxyl group-containing resin according to the present invention.
Yield point elongation% in machine direction (MD) and transverse direction (TD)
5 is a graph plotting the relationship with.

FIG. 2 Using a high-density polyethylene (HDPE) as a target standard, a biodegradable saturated polyester resin (PCL), a biodegradable saturated polyester resin (PCL / CaCO ₃ ) blended with calcium carbonate, and a biodegradable blended calcium carbonate Saturated polyester resin / Hydroxy group-containing resin (PC
6 is a graph plotting the relationship between temperature and storage modulus for L / PVA / CaCO ₃ ).

FIG. 3 A biodegradable saturated polyester resin (PCL), a blend of a biodegradable saturated polyester resin and a hydroxyl group-containing resin (PCL / PVA), and calcium carbonate were compounded with high density polyethylene (HDPE) as a target standard. Biodegradable saturated polyester resin / hydroxyl-containing resin (PC
₃ is a graph plotting the relationship between the number of aging days at the time of landfill in soil and the residual weight ratio for L / PVA / CaCO ₃ ).

Claims (7)

(57) [Claims] 1. Improved mechanical properties, characterized in that it contains a saturated polyester resin predominantly containing hydroxyalkanoate units, a thermoformable hydroxyl group-containing resin containing vinyl alcohol units and an alkaline earth metal carbonate. And a resin composition having biodegradability. 2. A saturated polyester resin of 20 to 85.5% by weight, a hydroxyl group-containing resin of 2.5 to 45% by weight, and an alkaline earth metal carbonate of 10 to 50, based on three components.
The resin composition according to claim 1, wherein the resin composition is contained in an amount of% by weight. 3. The resin composition according to claim 1, wherein the saturated polyester resin is an aliphatic polylactone or poly-ω-hydroxyalkanoate. 4. The saponification degree of the hydroxyl group-containing resin is 40 to 80%.
2. The resin composition according to claim 1, which is polyvinyl alcohol. 5. The hydroxyl group-containing resin has an ethylene content of 5 to 5.
The resin composition according to claim 1, which is an ethylene-vinyl alcohol copolymer having 0 mol% and a saponification degree of 90% or more. 6. The resin composition according to claim 1, wherein the alkaline earth metal carbonate is calcium carbonate. 7. The resin composition according to claim 1, wherein the alkaline earth metal carbonate is magnesium carbonate.