JPH0517590A - Resin-molded structure and its production - Google Patents

Abstract

PURPOSE:To provide a resin-molded structure having a new distributed multi- layer structure and excellent biodegradability, gas-shielding property, mechanical strength, melt-formability, etc., and to provide a process for producing the molded structure. CONSTITUTION:(A) A saturated polyester resin composed mainly of a hydroxyalkanoate unit (e.g. aliphatic polylactone, poly-omega-hydroxyalkanoate and poly-epsilon-hydroxyalkanoate) is compounded with (B) a thermoformable hydroxyl-containing resin containing a vinyl alcohol unit (e.g. a polyvinyl alcohol having a saponification degree of 40-80% or an ethylene-vinyl alcohol copolymer having an ethylene content of 5-40mol% and a saponification degree of >=90%) at a weight ratio (A:B) of 95:5 to 50:50 and the obtained composition is molded by extrusion or injection molding. The melt-viscosity of the hydroxylcontaining resin B is at least lower than that of the saturated polyester resin A at a melt temperature of 200 deg.C and a shearing rate of 1X10<3> to 6X10<3>sec-<1>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable resin molding structure and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the amount of solid waste discharged by cities has become huge, and the capacity of waste disposal is approaching its limit. Plastic is always 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 have been attracting attention. Degradable plastics include photodegradable plastics in which the molecular chain of the polymer is cleaved by ultraviolet rays, and biodegradable plastics that are destroyed by the action of enzymes released by bacteria and fungi outside the body.

However, in the case of photodegradable plastics, the effect of burying in the soil cannot be expected, and there is also a fear of environmental pollution due to decomposition products, so that great expectations are placed on biodegradable plastics.

Conventional biodegradable plastics include polyhydroxybutyrate (PHA), 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3H).
Random copolymers with V) are known.

[0006]

Known biodegradable plastics are stable in the air, and decompose in soil in which bacteria are active and in water, and the decomposition products are carbon dioxide gas. Although it has the advantage of being water, it still has problems to be solved in terms of container manufacture, which is the main use of plastics.

That is, in a known biodegradable plastic, for example, biopol in which 10% of hydroxyvalerate manufactured by ICI is copolymerized, the decomposition temperature and the molding temperature are 170 ° C.
Since the above is close to 160 ° C to 171 ° C,
Even if a molded product can be manufactured by the casting method using a solvent such as chloroform, there is a problem that the melt molding is difficult.

For this reason, when a hollow molded article such as a bottle is to be produced, a large amount of plasticizer must be contained in the resin to improve the melt extrusion performance. There is an unfavorable effect that the plasticizer is extracted into the). In addition, the present situation is that this container has a lower strength than the conventional polyethylene container and the like, and has a required thickness by increasing its thickness.

The present inventors have found that when a blended product of a saturated polyester resin mainly containing a hydroxyalkanoate unit and a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit is melt-molded under a certain condition, A molded product having a multi-layered distribution structure in which the contained resin is preferentially distributed in the central portion as compared with the inner and outer surfaces is formed, and this molded product has many biodegradability, gas barrier properties, mechanical strength, melt moldability, etc. It has been found to have advantages.

That is, the object of the present invention is to have excellent biodegradability,
Another object of the present invention is to provide a resin molded structure having a novel multi-layer distribution structure which is excellent in gas barrier property, mechanical strength, melt moldability and the like, and a manufacturing method thereof.

Another object of the present invention is to provide a resin composition for producing the above resin molding structure.

[0012]

According to the present invention,
It is formed from a blend of (A) a saturated polyester resin mainly containing a hydroxyalkanoate unit and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit. And a resin molding structure having a multi-layered distribution structure preferentially distributed in the central portion.

According to the present invention, further, (A) a saturated polyester resin mainly containing a hydroxyalkanoate unit and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, A: B = 95: A resin composition containing a weight ratio of 5 to 50:50 is provided.

According to the present invention, further, (A) a saturated polyester resin containing a hydroxyalkanoate unit as a main component and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, A: B = 95 : 5 to 50:50 by weight, melting temperature 200 ° C., shear rate 1 × 1
0 ³ to 6 × 10 ³ sec ^- preparation of at least (A) a lower melt viscosity than the resin ¹ in the range (B) multilayer distributed resin molded structure characterized by extruding or injecting resin is provided.

[0015]

In the resin molding structure of the present invention, the saturated polyester resin (A) is mainly composed of a hydroxyalkanoate unit (hereinafter may be simply referred to as a saturated polyester resin).
And (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit (hereinafter sometimes simply referred to as a hydroxyl group-containing resin) are used in the form of a blend.

As mentioned above, the saturated polyester resin (A) is a resin known as a biodegradable plastic, but according to the present invention, a hydroxyl group-containing resin (B) is blended with the saturated polyester resin. Achieves a novel and unexpected effect of promoting microbial ester degradation.

Further, the hydroxyl group-containing resin (B) containing a vinyl alcohol unit is superior in gas barrier property to oxygen gas and aroma components as compared with the saturated polyester resin. It is possible to remarkably improve the oxygen gas barrier property of the molded product.
Further, the hydroxyl group-containing resin is excellent in mechanical properties such as strength as compared with the saturated polyester resin, and by blending the resin, the mechanical strength of the resin molded product can be improved.

It has been found that a blend of the saturated polyester resin (A) and the hydroxyl group-containing resin (B) gives a resin molded product having a multilayer distribution structure under certain conditions. That is, the resin molded structure of the present invention comprises a hydroxyl group-containing resin (B).
The second feature is that it has a multi-layered distribution structure in which it is preferentially distributed in the central portion compared to the inner and outer surfaces.

In this resin molding structure, the hydroxyl group-containing resin is preferentially distributed in the central portion and the saturated polyester resin is preferentially distributed on the inner and outer surfaces, so that in addition to the above-mentioned decomposition promoting action, The bacteria have an excellent effect that the saturated polyester resin in the inner and outer layers is decomposed, and the hydroxyl group-containing resin in the intermediate layer is eluted into water, whereby the disintegration of the molded product is remarkably accelerated. Moreover, even if the hydroxyl group-containing resin of the intermediate layer does not elute in water and only absorbs and swells,
It has an effect of promoting decomposition of saturated polyester resin preferentially distributed on the inner and outer surfaces by enzymes and bacteria.

Further, since the hydroxyl group-containing resin having an excellent gas barrier property is concentrated in the central portion, the gas barrier property against oxygen gas and aroma components is higher than that of the resin composition in which the hydroxyl group-containing resin is uniformly distributed. The effect of further significantly improving is also obtained. Moreover, since the saturated polyester resin is preferentially distributed in the inner and outer surface layers, the water resistance of the molded product is remarkably improved, and as a result that the moisture absorption of the hydroxyl group-containing resin is suppressed, the hydroxyl group content by the moisture absorption is reduced. The remarkable advantage that the deterioration of the gas barrier property of the resin is suppressed is also achieved.

In the resin composition of the present invention, (A) a saturated polyester resin containing a hydroxyalkanoate unit as a main component and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, A: B = 95. : 5 to 50:50 In particular, it is also important to contain it in a weight ratio of 90:10 to 70:30.

When the content of the saturated polyester resin is less than the above range, the composition tends to have unsatisfactory biodegradability, and it tends to be difficult to form the multilayer distribution structure intended in the present invention. is there. Also, the moisture resistance is likely to decrease. On the other hand, when the content of the hydroxyl group-containing resin is less than the above range, this composition cannot obtain the effect of promoting the biodegradability intended by the present invention, and it is difficult to form the multilayer distribution structure intended by the present invention. Tends to be one.

In the production of the resin molded structure, the melting temperature is 200 ° C. and the shear rate is 1 × 10 ^{3 to} 6 × 10 ³ se.
c ^- and it is important at least to a saturated polyester resin than extruding or injecting a low melt viscosity hydroxyl-containing resin ^1, and this is an additional feature of the present invention.

In the present invention, the above-mentioned blend is subjected to melt extrusion, injection molding or the like so that the hydroxyl group-containing resin is substantially continuous, or distributed in layers, mainly in the center of the formed structure. The unexpected advantage of gaining is achieved. This is because under a molding condition such as melt extrusion or injection, a considerably large shearing force within the above-mentioned range acts on the molten blend when passing through a die, a nozzle or a gate, and the shearing force causes the hydroxyl group-containing resin to highly flow-orientate. It is considered that this flow oriented material has a distribution structure in which it is arranged or coordinated in the central portion of the resin flow. As a natural result of the arrangement and distribution of the hydroxyl group-containing resin, saturated polyester resin is mainly present on both surface portions of the molded structure. As described above, according to the present invention, a biodegradable resin molding structure having a multilayer distribution structure can be produced with high productivity using a single extruder or injection machine.

[0025]

Preferred Embodiment of the Invention

(Molded Structure) The molded structure of the present invention comprises a blend of (A) a saturated polyester resin mainly containing a hydroxyalkanoate unit and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit. It has a multilayer distribution structure in which the formed hydroxyl group-containing resin is preferentially distributed in the central portion as compared with the inner and outer surfaces. As a natural result of this, the saturated polyester resin is preferentially distributed on the inner and outer surfaces.

In this molded structure, the fact that the hydroxyl group-containing resin is preferentially distributed in the central portion as compared with the inner and outer surfaces can be confirmed by various methods. The hydroxyl group-containing resin can be dyed with a certain type of dye, so by dyeing the cross section of the molded structure with a dye and observing the cross section with a microscope, etc., it is confirmed that the resin is preferentially distributed in the center. it can.

The hydroxyl group-containing resin has a wave number of 3300c.
Since the m ^{- 1} has a characteristic absorption, while the saturated polyester resin has a characteristic absorption at a wave number of 725 cm ^{- 1} , the infrared absorption spectrum (IR) of the entire molded structure and the infrared absorption spectrum (IR) of the central part , The infrared absorption spectrum (IR) of the inner and outer surfaces is obtained, the concentration of the hydroxyl group-containing resin is obtained from the absorbance of the characteristic absorption, and the distribution ratio of the hydroxyl group-containing resin in the central portion can be obtained.

In the present invention, the distribution ratio (Dh) of the hydroxyl group-containing resin determined by the method described below is 70% or more, particularly 90% or more at the central portion in terms of gas barrier property and moisture resistance.

The distribution orientation state of the hydroxyl group-containing resin may be variously changed, but it may be changed from a complete layer state to a dispersed state or continuous state of particles, fibers and flakes. Generally, it is preferable that the intermediate layer is substantially continuous when seen through in the thickness direction of the container wall. This state means that (I) the intermediate layer is present in the form of a continuous film, and (II) the intermediate layer. Although the layers are not in the form of a continuous film, they are in the form of a large number of flakes, and these flakes overlap at least at their edges in the thickness direction, and when seen through, they are continuous in the plane direction. And (III) above (I) and (I
The case where it exists in the intermediate state with I) or the combination of the above (I) and (II) is included.

FIG. 1 showing the cross-sectional structure of the molded structure of the present invention.
In, the molded structure 1 comprises an inner layer 2 and an outer layer 3 in which a saturated polyester resin is mainly distributed, and an intermediate layer 4 of a hydroxyl group-containing resin distributed in the center so as to be sandwiched between these inner and outer layers. The hydroxyl group-containing resin forming the intermediate layer exists in a layered form. 1A shows the case where the hydroxyl group-containing resin exists as a film 11 continuous in the plane direction, and FIG. 1B shows the case where the hydroxyl group-containing resin is a thin piece 12.
1C shows a case in which a large number of the thin pieces 12 are arranged in the plane direction and at least the edge portions thereof are overlapped in the thickness direction of the container wall.
Shows a state in which the continuous film 11 and the thin piece 12 coexist, and more specifically, a state in which the continuous film 11 is distributed in the center of the intermediate layer and the thin pieces 12 are distributed on both sides thereof. Of course, in the multilayer distributed molding structure of the present invention, the hydroxyl group-containing resin may be present as a continuous film 11 in a certain portion, and the hydroxyl group-containing resin may be present as an integrated array of thin pieces 12 in another portion.

(Saturated Polyester Resin) As the saturated polyester resin, any biodegradable saturated polyester resin mainly containing a hydroxyalkanoate unit is used. This saturated polyester resin should have at least a molecular weight capable of forming a film, and generally its number average molecular weight is preferably in the range of 50,000 to 120,000, particularly 60,000 to 110,000. Examples of suitable saturated polyester resins are poly-β-hydroxyalkanoates, or aliphatic polylactones to poly-ω-hydroxyalkanoates or copolymers thereof.

The poly-β-hydroxyalkanoate has the following formula:

[Chemical 1] In the formula, R is a linear or branched alkyl group, and a repeating unit represented by, for example, 3-hydroxybutyrate [R = -CH ₃ , 3HB],
3-hydroxyvalerate [R = -CH ₂ CH _3, 3H
V], 3-hydroxycaproate [R =-(CH ₂ ).
₂ CH _3], 3-hydroxy heptanoate [R = -
(CH _{2) 3} CH _3], 3-hydroxy octanoate _{[R = - (CH 2) 4} CH 3 ] 3-hydroxy nonanoate _{[R = - (CH 2) 5} CH 3 ] 3-hydroxy deca Noeto _{[R = - (CH 2) 6} CH 3 ], one or of two or more polymers and the like.

Suitable resins of this type are 3-hydroxybutyrate and other 3-hydroxyalkanoates,
In particular, it is a copolymer obtained by copolymerizing with 3-hydroxyvalerate, and these are 95: 5 to 85:15, particularly 9:
It is a copolymer containing a weight ratio of 2: 8 to 88:12.

The aliphatic polylactone or poly-ω-hydroxyalkanoate has the following formula:

[Chemical 2] In the formula, R1 is a linear or branched alkylene group,
A repeating unit represented by, for example, γ-butyrolactone, δ
-A polymer composed of one type or two or more types of repeating units such as parerolactone and ε-caprolactone.

Suitable examples of this type of resin are polycaprolactone or copolymers of caprolactone with other lactones.

In the present invention, it is also possible to use a copolymer comprising a repeating unit of "Chemical formula 1" and a repeating unit of "Chemical formula 2". 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 may be used.

(Hydroxyl group-containing resin) As the hydroxyl group-containing resin used in the present invention, any resin can be used as long as it has a hydroxyl group and can be thermoformed. This resin has a repeating unit having a hydroxyl group in its molecular chain and a unit that imparts thermoformability to the resin. The hydroxyl group-containing repeating unit may be a vinyl alcohol unit or a hydroxyalkyl (meth) acrylate unit, but a vinyl alcohol unit is preferable from the viewpoint of biodegradability. Other units contained in this hydroxyl group-containing resin are olefin units such as ethylene and propylene, vinyl ester units such as vinyl acetate; alkyl (meth) acrylate units and the like. These hydroxyl-containing resins should also have at least a molecular weight sufficient to form a film.

A suitable hydroxyl group-containing resin is represented by the following formula

[Chemical 3] The vinyl alcohol unit represented by

[Chemical 4] In the formula, R2 is a hydrogen atom or an alkyl group, and an olefin unit represented by

[Chemical 5] In the formula, R3 is an alkyl group and is composed of at least one vinyl ester unit represented by.

A hydroxyl group-containing resin particularly suitable for the purpose of the present invention is polyvinyl alcohol having a saponification degree of 40 to 80%, particularly 60 to 70%. Polyvinyl alcohol having a saponification degree in this range is thermoformable, and when blended with a saturated polyester resin, it has excellent ability to form a multi-layer distribution structure and high mechanical strength. This polyvinyl alcohol is generally 300 to 800, especially 400 to 60.
It should have an average degree of polymerization of 0.

Another hydroxyl group-containing resin particularly suitable for the purpose of the present invention is an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 40 mol%, particularly 10 to 30 mol% and a saponification degree of 90% or more. is there. In this ethylene-vinyl alcohol copolymer, even if there are ethylene segments in which ethylene units are bonded to each other, the molecular weight of the segment is preferably 2000 or less, particularly 500 or less from the viewpoint of biodegradability. On the other hand, it is preferable that there are also segments in which vinyl alcohol units are bonded to each other. It is said that in a segment in which a plurality of vinyl alcohols, particularly three, are bonded, one secondary hydroxyl group becomes a keto group and the decomposition proceeds rapidly.

(Composition) According to the present invention, (A) a saturated polyester resin mainly containing a hydroxyalkanoate unit and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, = 95: 5 to 50:50 In particular, the mixture is used in a weight ratio of 90:10 to 70:30, but the melting temperature is 200.
° C., a shear rate of 1 × 10 ³ to 6 × 10 ³ sec ^- in the range of ¹ (A) low melt viscosity than the resin (B) to combine resin may in terms of forming a layered distribution structure. When a branched channel or the like is not used, the hydroxyl group-containing resin (B) is used as compared with the melt viscosity of the saturated polyester resin (A).
To lower the melt viscosity of.

The molding composition of the present invention contains various coloring agents, fillers, inorganic or organic reinforcing agents, lubricants, plasticizers, leveling agents, surfactants and thickeners, depending on the use. , A viscosity reducing agent, a stabilizer, an antioxidant, an ultraviolet absorber, an anticorrosive agent and the like can be added.

(Production Method) According to the present invention, (A) a saturated polyester resin having a hydroxyalkanoate unit as a main component and (B) a thermoformable hydroxyl group-containing resin having a vinyl alcohol unit as A: B = 95: 5 to 50:50 in a polymerization ratio, the melting temperature is 200 ° C., and the shear rate is 1 × 1.
0 ³ to 6 × 10 ³ sec ^- by ¹ in the range (A) extruding or injecting a lower melt viscosity (B) resin resin to produce a molded structure.

During the production of the molded structure, the saturated polyester resin and the hydroxyl group-containing resin are supplied in the form of a mixture to the hopper of an extruder or an injection machine. This mixture may be a dry blend or a melt blend of both. Dry blending can be performed using various mixers such as ribbon blender, conical blender, and Henschel mixer, while melt blending is performed using a single-screw or twin-screw extruder, kneader, Banbury mixer, roll, etc. You can Generally, it is recommended to use a dry blend because of the ease of operation and the ease of expression of a multi-layer distribution structure.

In molding the multilayer distributed structure, the mixture is melt extruded through a die having a shear rate within the above range at a temperature that gives a predetermined melt viscosity difference, or the shear rate within the above range. Melt injection into a cooled injection mold through such sprue and nozzle.

As the extruder, an extruder equipped with a screw having a low degree of mixing of the resin flow, for example, a metalling screw is preferably used so that the layered distribution structure can be easily expressed. As the die, a flat die or a ring die can be used, and for example, a T die method or an inflation film forming method is used for forming a film.
Further, by hollow-molding the extruded parison, hollow-molded containers such as bottles, tubes, and tanks are molded.

As the injection machine, one known per se equipped with 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 above-described multilayer distribution structure is formed in the resin flow, flows into the injection mold cavity, and is cooled and solidified to form the multilayer distribution molding structure of the present invention.

(Use) The molded structure having a multi-layered distribution structure of the present invention can be used as various plastic packaging containers such as bottles, cups, tubes, plastic cans, pouches, caps, and as packaging materials for films, trays, and the like. It is useful as a distribution container such as a container, a tank and a box, and as a structure such as a pipe and a case.

[0049]

EXAMPLES Next, the method of the present invention will be described with reference to examples. Measurement method 1) Polycaprolactone H-7, H-4 manufactured by Daicel Chemical Industries, Ltd. was used as a poly-ω-hydroxyalkanoate in a sample saturated polyester, and ICI was used as a poly-β-hydroxyalkanoate. Polyhydroxybutyrate having a hydroxyvalerate copolymer composition of 10% was used. In addition, thermoformable partially saponified polyvinyl alcohol is used for HM series manufactured by Kuraray Co., Ltd., HMN-04,
HMN-03, HM-05, HM-04 and HM-03 were used.

2) Molding method 2-1) Sheet molding Using a Labo Plastomill C type molding machine, a D-20-20 type extruder, and a sheet take-off machine manufactured by Toyo Seiki Seisakusho Co., Ltd., a molding temperature of 180. A sheet having a thickness of 1 mm and a width of 120 mm was formed at a screw rotation speed of 50 rpm at 200 ° C.

2-2) Bottle Molding TEM-35B, manufactured by Toshiba Machine Co., Ltd., using a twin-screw extruder, extrusion temperature 160 ° C., screw rotation speed 1
Melt blending was performed at 00 rpm to form pellets. Furthermore, this pellet was manufactured by Ikegai Co., Ltd., ES65
Direct blow molding was performed using a mold and an extruder at an extrusion temperature of 160 ° C., a screw rotation speed of 300 rpm, a mold temperature of 16 ° C., and a blow air pressure of 6 kg / cm ² .

3) Layer observation of sheet cross section Using an Ultramicrotome 2550 supercut for optical microscope manufactured by Reichert-Junk, slice sections having a thickness of 8 to 10 μm were obtained in the extrusion direction of the sheet cross section. This sample was used for low magnification microscopic observation and FT-IR analysis.

3-1) Microscope observation 104 type polarizing microscope OPTIPHO, manufactured by Nikon Corporation
It was observed with transmitted light using T2-POL without using a polarizing plate. 3-2) FT-IR analysis JIR-100, FT-IR, manufactured by JEOL Ltd., using a micro ATR method for the inner and outer surfaces of the sheet, and transmitting a minute point of 50 μm light diameter at the central portion in the thickness direction. It was measured by the method. Both spectra were integrated 500 times.

Next, in order to quantitatively handle the obtained spectrum, the absorption ratio method was calculated using the characteristic absorption peaks of the saturated polyester and partially saponified polyvinyl alcohol used. 725 for the characteristic absorption of poly-ω-hydroxyalkanoate used as saturated polyester
The stretching vibration of methylene at cm ^{- 1} and the stretching vibration of -OH group at 3300 cm ^{- 1} were used for the characteristic absorption of partially saponified polyvinyl alcohol. The absorbance ratio (D) was calculated from the respective peak intensities (I) using the formula [Equation 1].

[Number 1] _{D = I 3 0 0 0 cm} - 1 / I 7 2 5 cm - 1 the formula I shows a peak intensity.

Further, the distribution ratio (Dh) is calculated by the formula [Formula 2] using the absorbance ratio (D) obtained by the formula [Formula 1] for the uneven distribution of the partially saponified polyvinyl alcohol which is unevenly distributed in the central portion in the sheet thickness direction. Was calculated.

[Equation 2]

4) Measurement of mechanical strength Using a UCT-5T type, Tensilon, manufactured by ORIENTEC Co., Ltd., 500 mm / in a 100 kg load cell.
It was measured at a pulling speed of min. The shape of the measurement sample is A
STM, D-1822 type was used. The obtained strength was converted into the strength per unit cross-sectional area.

5) The sheet molded product obtained by the sheet molding method of the water resistance test 2) is 2c.
It was cut into m squares and immersed in a beaker containing 100 ml of distilled water. The cumulative immersion time was 312 hours, and the immersion was performed for 13 days in terms of days. Take out this immersion sample at appropriate times,
JK wiper, 150-, manufactured by Tojo Kimberley Co., Ltd.
Water droplets were wiped off using S, left at room temperature for 10 minutes, and then weighed with an analytical balance. The sample soaked for 312 hours was dried at room temperature, then dried under reduced pressure for 20 hours, and weighed with an analytical balance. This value was defined as the absolute dry weight.

6) Procurement of lipase enzyme solution Ester-degrading enzyme lipase was used. 1.010 unit / produced by Sigma Co., Ltd. and produced by Candita cylindria
mg solid, lipase, Na ₂ PO ₄ , KH ₂ PO ₄ 1
Dissolve 5 g in 1 liter of 100/100 normal solution,
It was a lipase enzyme solution.

Example 1 Poly-ω-hydroxyalkanoate (A) having a number average molecular weight of 70,000 to 100,000 and 60% partially saponified polyvinyl alcohol (B) having a degree of polymerization of 500 (A) :( B) = 100: 0
A sheet was prepared by extrusion molding at a blend weight ratio range of 30 to 70:70. The thickness of the obtained sheet is about 1 m
It was m. This sheet was used for measurement of mechanical strength, water resistance test, and layer observation of sheet cross section, which will be described later. In addition, this sheet has a bottom diameter of 32 mm, a mouth diameter of 38 mm, and a height of 39 mm.
It was thermoformed into a cup having a size of 40 mm and a volume of 40 ml, and used for the test of gas barrier property and enzymatic decomposition.

1) Evaluation of degradability by lipase enzyme solution Poly-ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) were each (A):
(B) = 100: 0, 90:10, 70:30 The weight ratio of the cup molding used. Each of these cups was immersed in a lipase enzyme solution. As for the dipping method, a cup and 100 ml of the lipase enzyme solution were placed in a weighing bottle with a lid having a volume of 100 ml and stored at 35 ° C. The lipase enzyme solution was changed at a fixed time every day. The immersed cup was taken out at appropriate time, dried under reduced pressure for 10 hours, and then weighed with an analytical balance. The results are shown in Fig. 2. In FIG. 2, the horizontal axis shows the number of days of immersion, and the vertical axis shows the weight residual ratio of the sample. The weight residual ratio was determined by (W ₁ / W ₀ ) × 100 from the initial weight W ₀ and the weight W ₁ at the time of lipase enzyme treatment.

From FIG. 2, it is clear that the saturated polyester poly-
Compared to the ω-hydroxyalkanoate alone molded cup,
The weight loss of the cup containing partially saponified polyvinyl alcohol when treated with the lipase enzyme solution was larger. Considering the water resistance derived from the multilayered layer structure of the molded body, which will be described later in the section 2) Layer observation of sheet cross section and 3) Water resistance test, this tendency of weight reduction is unevenly distributed in the inner and outer surface layers. It was considered that the -ω-hydroxyalkanoate resin was eroded by the lipase, and then the partially saponified polyvinyl alcohol unevenly distributed inside was eluted in water. Therefore, it was obtained that the decomposition by the treatment with the enzyme solution of lipase leads to the decomposition through a decomposition process depending on the shape of the multilayer structure of poly-ω-hydroxyalkanoate and partially saponified polyvinyl alcohol.

2) Layer observation of cross section of sheet Poly-ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) respectively (A):
(B) = 90:10, 50:50, 30:70 The weight ratio of the sheet molded product was sliced in the sheet extrusion direction, and low magnification microscope observation and FT-IR analysis were performed. A low-magnification microscopic observation clearly confirmed a semi-transparent layer in the central portion in the sheet thickness direction, and from the FT-IR analysis, absorption of hydroxyl groups was observed only in the layered material at the central portion. Among the resins used, the poly-ω-hydroxyalkanoate resin has no hydroxyl groups in its molecular structure, so the semi-transparent layer in the central part in the sheet thickness direction confirmed by visual observation shows uneven distribution of partially saponified polyvinyl alcohol. Recognized as a layer. Next, the distribution of the partially saponified alcohol in the sheet thickness direction was calculated by the distribution rate (Dh). As a result,
The weight ratio of ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) is (A) :( B) = 9.
In the case of 0:10 to 50:50, the value of Dh = 70% or more was exhibited and the shape of the multilayer structure was retained.

3) Water resistance test Poly-ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) were each (A):
A sheet having a weight ratio of (B) = 80: 20, 50:50, 30:70 was cut into 2 cm squares and immersed in distilled water. The results are shown in Fig. 3. In FIG. 3, the horizontal axis shows the immersion time and the vertical axis shows the weight retention of the sample. The weight retention rate was expressed as W ₁ / W ₀ from the initial weight W ₀ and the weight W ₁ at the time of immersion in distilled water.

As shown in FIG. 3, the weight of the sample increased as the immersion time increased, showing that the sample absorbed water. 312
In the sample with the weight ratio (A) :( B) = 80: 20 after the lapse of time, the weight retention in an absolutely dry state was 96%, and the sample had water resistance. Further, in the case of the sheet piece having the weight ratio (A) :( B) = 50: 50, the solubility was recognized in the minute region of the surface layer, but the visually observable change in the surface shape did not occur. on the other hand,
In the sheet piece having a weight ratio (A) :( B) = 30: 70, the surface layer was remarkably dissolved. Therefore, the range of the weight ratio of the blend of the poly-ω-hydroxyalkanoate (A) and the partially saponified polyvinyl alcohol (B) satisfying the water resistance is (A) :( B) = 100: 0 to 50: It was determined to be 50.

4) Mechanical Strength Poly-ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) are each (A):
(B) = 100: 0, 90:10, 80:20, 70:
A sheet formed by blend molding in a weight ratio of 30 is ASTM D
The test piece was punched out into a -1822 type dumbbell and the yield strength of this test piece was examined. The results are shown in Fig. 4. In FIG. 4, the horizontal axis shows the composition ratio of the dry blend, and the vertical axis shows the yield strength of the test piece. For comparison, Showlex D50 Shalex S50
The yield point strength of the dumbbell cut out from the HDPE bottle for commercial household detergent using 0 was shown by a dotted line. If the strength is higher than the dotted line in FIG. 4, the practical bottle strength will be satisfied. From FIG. 4, it can be seen that a blend of poly-ω-hydroxyalkanoate and partially saponified polyvinyl alcohol
Those containing at least wt% partially saponified polyvinyl alcohol satisfy the strength. However, if the content of the partially saponified polyvinyl alcohol is too large, the obtained sheet piece reflects the physical properties of the partially saponified polyvinyl alcohol and has a rigid and brittle property, so that the suitability for a container is impaired in terms of brittleness. Therefore, if the weight ratio of poly-ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) is (A) :( B) = 95: 5 to 50:50, the container suitability is satisfied. I decided it was.

5) Gas barrier poly-ω-hydroxyalkanoate (A) and partially saponified polyvinyl alcohol (B) are each (A):
A sheet having a weight ratio of (B) = 100: 0, 90:10, 70:30 was formed into a cup having a bottom diameter of 32 mm, a mouth diameter of 38 mm, a height of 39 mm and a volume of 40 ml. The cup was sealed with a polyester sealant-coated aluminum thin film in a nitrogen atmosphere. This test product was stored under a routine laboratory atmosphere, and the oxygen gas concentration inside the cup was examined by gas chromatography. The results are shown in Fig. 5. In FIG. 5, the horizontal axis shows the number of storage days and the vertical axis shows the oxygen gas concentration. The oxygen gas permeability coefficient of poly -ω- hydroxyalkanoate is 1.3 × 10 ^- a ^{1 0 cm 3 / cm 2 seccmHg} . From FIG. 5, the oxygen gas permeation amount decreased as the partially saponified polyvinyl alcohol content increased. 2)
Considering the multilayer structure shown in the section of layer observation of the sheet cross section, an increase in the composition ratio of partially saponified polyvinyl alcohol is considered to increase the thickness of the intermediate layer of the sheet cross section, and therefore the gas barrier property is improved. I decided it was.

The above results are summarized in Table 1. In conclusion, when a poly- [omega] -hydroxyalkanoate (A) is used as the saturated polyester to form a blended molded product with the partially saponified polyvinyl alcohol (B), the resin composition has a weight ratio of (A) :( B ) = 95: 5 to 50:
A range of 50 was judged to be good.

[0068]

[Table 1]

Example 2 Hydroxyl valerate 10% copolymer poly-β-hydroxyalkanoate (A) manufactured by ICI Co., Ltd. and a polymerization degree of 50
A sheet having 60% partially saponified polyvinyl alcohol (B) of 0 in a weight ratio of (A) :( B) = 80: 20 was prepared. As a result of slicing this sheet piece in the sheet extrusion direction and observing it with a low-magnification microscope, a semitransparent layer which can be clearly judged to be an intermediate layer also existed in this sheet piece. Therefore,
Similar to poly-ω-hydroxyalkanoate, a multi-layer structure was obtained also in a dry blend molding of partially saponified polyvinyl alcohol using saturated polyester and poly-β-hydroxyalkanoate.

Example 3 Poly-ω-hydroxyalkanoate (A) having a number average molecular weight of 70,000 to 100,000 and 60% partially saponified polyvinyl alcohol (B) having a degree of polymerization of 500 (A) :( B) = 80: 20
After dry blending at a weight ratio of 1, the melt blending was performed using a twin-screw extruder. The pellets of the melt blend were directly blown by the molding method described in the section of Measurement method 2-2) to obtain a bottle-shaped molded article. As a result of taking out the parison before blow molding and observing the layer cross section, a concentric multi-layer structure was also confirmed in this parison. Therefore, even in the bottle-formed product of the melt blend, the same effects of water resistance, gas barrier property, mechanical strength, and enzyme decomposability as in the case of sheet forming were obtained.

[0071]

According to the present invention, (A) a saturated polyester resin containing a hydroxyalkanoate unit as a main component,
(B) By using a blend with a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, and molding this under specific conditions, the hydroxyl group-containing resin is given priority over the central portion over the inner and outer surfaces. A resin molding structure having a novel multi-layered distributed structure obtained is obtained. The molding structure is particularly excellent in biodegradability, and is also excellent in gas barrier property, mechanical strength, melt moldability and the like. Has the advantage.

[Brief description of drawings]

FIG. 1 is a view showing a sectional structure of a molded structure of the present invention.

FIG. 2 is a graph showing a change in weight of a blend of a saturated polyester resin and a hydroxyl group-containing resin in Example 1 when treated with a lipase enzyme solution.

FIG. 3 is a diagram showing a weight change of the above blend in Example 1 when immersed in distilled water.

FIG. 4 is a diagram showing the relationship between the blending ratio of the blended product and the strength of the molded sheet in Example 1.

FIG. 5 is a graph showing the relationship between the blend ratio of the blend of Example 1 and the gas barrier property of the molding container.

[Explanation of symbols]

1 Molded structure 2 inner layer 3 outer layers 4 Intermediate layer of hydroxyl group-containing resin distributed on the center side 11 A continuous film of hydroxyl group-containing resin in the plane direction 12 Thin pieces of hydroxyl group-containing resin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // B29C 45/00 7344-4F C08L 67:04

Claims (10)

[Claims] 1. A blended product of (A) a saturated polyester resin mainly containing a hydroxyalkanoate unit and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, wherein the hydroxyl group-containing resin is A resin molding structure having a multi-layered distribution structure in which distribution is preferentially distributed in a central portion as compared with inner and outer surfaces. 2. The molding structure according to claim 1, wherein the saturated polyester resin (A) and the hydroxyl group-containing resin (B) are present in a weight ratio of A: B = 95: 5 to 50:50. 3. The molded structure according to claim 1, wherein the saturated polyester resin (A) is an aliphatic polylactone or poly-ω-hydroxyalkanoate. 4. The saturated polyester resin (A) is poly-β.
Molded structure according to claim 1, which is a hydroxyalkanoate. 5. The molded structure according to claim 1, wherein the hydroxyl group-containing resin (B) is polyvinyl alcohol having a saponification degree of 40 to 80%. 6. The hydroxyl group-containing resin (B) is ethylene having an ethylene content of 5 to 40 mol% and a saponification degree of 90% or more.
The molded structure according to claim 1, which is a vinyl alcohol copolymer. 7. Molded structure according to claim 1, wherein the hydroxyl group-containing polymer is present as at least one continuous intermediate layer. 8. The polymer according to claim 1, wherein the hydroxyl group-containing polymer is in the form of a large number of flakes, and these flakes are present as an intermediate layer which overlaps in the thickness direction at least at their edges when seen through in the thickness direction. Molded structure. 9. A: (A) a saturated polyester resin mainly containing a hydroxyalkanoate unit and (B) a thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit, wherein A: B = 95: 5 to 50:50. A resin composition containing the same in a weight ratio of 10. A melting temperature of 200 ° C. and a shear rate of 1 × 10.
³ to 6 × 10 ³ sec ^- at least ^one of the range (A)
A thermoformable hydroxyl group-containing resin containing a vinyl alcohol unit (B) having a lower melt viscosity than a saturated polyester resin mainly containing a hydroxyalkanoate unit is used, and A: B = 95: 5 to 50:50 in a weight ratio. A method for producing a multi-layer distribution resin molded structure, which comprises containing and extruding or injecting.