JP2000239508A - Biodegradable molding compound and its molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable molding compound having low warpage, excellent in mechanical properties and biodegradability by melting and mixing polyhydroxybutyric acid, polylactic acid, inorganic filler and crystal nuclearating agent. SOLUTION: This compound is obtained by melting and mixing (A) preferably 50-90 wt.% more preferably 70-85 wt.% poly-3-hydroxybutyric acid based on total weight of the component A and B, (B) polylactic acid, (C) 10-60 wt.% inorganic filler preferably having 0.1-50 μm particle diameter (e.g. calcium carbonate), (D) 0.3-5.0 wt.% crystal nuclearating agent (e.g. boron nitride) and (E), if necessary, a colorant, a plasticizer, a mold releasing agent, a lubricant or the like. The component A can be prepared by fermentation process using a bacteria belonging to the genus Alcaligenes, the genus Azotobacter, the genus Methylobacterium and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to poly-3-hydroxybutyric acid (hereinafter abbreviated as PHB), polylactic acid (hereinafter referred to as PLA)
The present invention relates to a biodegradable low warpage molding material comprising an inorganic filler and a crystal nucleating agent and a molding method thereof.

[0002]

2. Description of the Related Art Conventionally, many plastics have been used as molding materials for industrial materials, machine parts, automobile parts and the like. At the same time, from the standpoint of environmental protection, the recycling of plastics is called for, and the use of biodegradable resins, which degrade by the action of microorganisms or hydrolysis, is strongly used in applications where recycling is not possible. It has been requested. Generally, aliphatic polyesters are known to have biodegradability, and have different properties depending on their molecular compositions. For this reason, manufacturers and processing manufacturers are actively developing applications that take advantage of their respective characteristics. PHB and PLA are
It has high rigidity among biodegradable resins represented by aliphatic polyesters, and is expected to be applied to fields requiring high rigidity. Applications that require high rigidity include electrical parts such as plastic reels and fans, large panels, industrial articles such as housings, industrial members, and rigid molded articles such as building members.
In some cases, a flat surface without warpage may be required.

[0003] PHB is molded under conditions that accelerate crystallization because of a glass transition point of 5 ° C. When molding a molded article such as a flat plate, it takes several hours after the molded article is removed from a mold. Crystallization proceeds slowly over time, and warpage may occur. Further, in the case of PLA, since the glass transition point is about 60 ° C., the mold is often molded at a mold temperature of 60 ° C. or less.
If the temperature exceeds ℃, deformation may occur. Further, when molding is performed at a mold temperature at which crystallization of PLA proceeds, the molding cycle time becomes extremely long, which is not practical. Plus PLA
It is known that the rate of biodegradability in natural environments is low. Therefore, PHB and PLA have been developed to meet the demand for a high-rigidity material having a high biodegradability rate and no warpage.
The reality is that despite having the stiffness to respond, it has not been able to respond sufficiently.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and provides a biodegradable low-warping molding material having excellent mechanical performance and biodegradability, and a molding method therefor. The subject.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. That is, PHB and PL are added to the biodegradable resin.
A, and a biodegradable resin composition containing an appropriate amount of an inorganic filler typified by calcium carbonate and a crystal nucleating agent typified by boron nitride can be formed with a realistic molding cycle time and warpage. Generation was hardly observed, and it was found that it could be converted into a molded article having sufficiently practical strength, and the present invention was completed.

The gist of the present invention is (1) PHB, PLA,
A biodegradable low warpage molding material obtained by melting and mixing an inorganic filler and a crystal nucleating agent, (2) the weight of PHB is 50% to 90% based on the sum of the weights of PHB and PLA. (3) calcium carbonate is used as the inorganic filler, and the blending amount of the calcium carbonate with respect to the biodegradable low warpage molding material is 10 to 60% by weight. (4) Boron nitride is used as a crystal nucleating agent, and the compounding amount of the boron nitride with respect to the biodegradable low warpage molding material is 0.3 to 5.0% by weight. (1) to (3), a low-curable biodegradable molding material according to any one of (1) to (3), and (5)
(1) The biodegradable low-warp material is formed by molding the biodegradable low-warp molding material according to any one of (1) to (4) at a resin temperature of 130 to 250 ° C and a mold temperature of 0 to 70 ° C. Molding method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION PHB shown in the present invention is, for example, a genus Alcaligenes, a genus Azotobacter, a methylobacterium.
terium), Nocardia, Pseudomonas, etc. by a known fermentation method. PH obtained by fermentation method
Regarding the method for separating and purifying B, for example, US Pat. Nos. 3,036,959, 4,015,533, 3,275,610, and EP 15123.
Discloses a purification method using a solvent such as pyridine, methylene chloride, 1,2-propylene carbonate, chloroform, and 1,2-dichloroethane, and JP-A-7-177894 discloses a bacterial cell. Is crushed by a high-pressure homogenizer, PHB is separated, and the separated PHB is treated with an enzyme-based bleach. Recently, a method for producing PHB containing a 3-hydroxybutyric acid unit by chemical synthesis without using a fermentation method has been reported. Further, polylactic acid can be produced by using lactic acid obtained by a chemical synthesis method or a fermentation method as a raw material, for example, a method of ring-opening polymerization after forming lactide, or a method of directly polymerizing lactic acid.

The inorganic filler represented by the present invention can be calcium carbonate, calcium carbonate whisker, magnesium carbonate, talc, mica, mica, etc. Among them, calcium carbonate is expensive, and the performance of the obtained molded product is high. Is excellent in terms of The particle size of the inorganic filler is not particularly limited, but is preferably 0.1 to 50 μm, which is generally used. Further, the crystal nucleating agent can be boron nitride, talc having a specific particle size, or the like. Among them, boron nitride is preferable because it is excellent in the effect of increasing the crystallization rate.

In the present invention, the weight of PHB is preferably 50 to 90%, more preferably 70 to 85%, based on the sum of the weight of PHB and PLA. Because P
If the weight of HB is less than 50% and the weight of PLA is larger, the amorphous portion of PLA occupies a large amount in the molded product, resulting in poor heat resistance at 60 ° C. or higher. If it exceeds 90%, warpage due to crystallization after molding of PHB becomes noticeable, which is not preferable. Inorganic fillers such as calcium carbonate are 10 to 10
It is preferable to mix 60% by weight. The inorganic filler has an effect of suppressing the generation of burrs and further increasing the rigidity. However, if it is less than 10% by weight, there is a possibility that a sufficient effect of suppressing the generation of burrs may not be obtained. As the molded product becomes brittle, the specific gravity increases,
It is not preferable because the intended use may be limited. It is preferable that the nucleating agent is incorporated in an amount of 0.3 to 5.0% by weight. This is because if it is less than 0.3% by weight, the effect of accelerating the crystallization rate of PHB becomes insufficient, and PHB may be crystallized after the molded article is taken out from the mold, which may cause warpage. PHB over 5.0 wt%
The crystallization rate accelerating effect is hardly further improved, and the nucleating agent is relatively expensive.
It is preferred that the amount does not exceed weight%.

When molding the low warpage molding material of the present invention, the resin temperature is preferably from 130 to 250 ° C., more preferably from 180 to 220 ° C. Because 13
If the temperature is lower than 0 ° C., a sufficient molded product cannot be obtained because of insufficient plasticization. If the temperature exceeds 250 ° C., deterioration due to decomposition of the resin is extremely undesirable. Mold temperature is 0-70 ° C
And preferably 0 to 40 ° C.
If the temperature is lower than 0 ° C., equipment for maintaining the temperature during continuous molding becomes large, and the cost for the product may increase. On the other hand, if the temperature exceeds 70 ° C., the molding cycle time is undesirably long.

[0011] Substances other than PHB, PLA, inorganic fillers and nucleating agents, such as coloring agents, plasticizers, release agents, lubricants, etc., do not depart from the scope of the present invention and do not impair the objects of the present invention. Conventional additives such as an ultraviolet absorber, an antistatic agent, a flame retardant, and an antioxidant can be added according to the purpose.

[0012] The biodegradable molding material of the present invention can be used to obtain hard low warpage molded products such as industrial / civil engineering / agricultural / fishing materials, machine parts, medical members and the like. These molded products cannot be collected or reused after use and are expected to be used in landfills, for example, plastic reels,
It can be converted into fans, large panels, housings, various automobile parts, etc.

[0013]

According to the present invention, a low-warping molding material having excellent mechanical performance and biodegradability can be provided, and can be applied to various members.

[0014]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Various measurements were performed by the following methods. Specific gravity measurement: Underwater displacement method Tensile test: JIS K 7213 Bending test: JIS K 7203 Heat resistance evaluation: A tensile test piece is cantilevered and allowed to stand at 60 ° C. Evaluation was made based on the deformation amount after 2 hours. Warpage evaluation: A hat-shaped warpage evaluation molded article (collar part: thickness 1.5 mm, diameter 9 cm, projection part: height 1.4 mm, diameter 2.1 mm) was molded, and evaluated by the amount of deformation from the horizontal at the edge of the collar. .

Examples 1-4 A bacterium, Protomonas extorquens, deposited at the Institute of Biotechnology and Industrial Technology, National Institute of Advanced Industrial Science and Technology.
xtorquens) K (Accession number: FERM BP-354)
Using 8), continuous culture was performed aerobically using methanol as a carbon source. The culture conditions were a culture temperature of 32 ° C. and a culture pH of 6.
5. Continuous cultivation was performed so that the average residence time was 40 hours, and the nitrogen supply rate was the rate-determining rate of bacterial cell growth. According to recent literature, this bacterium is methylobacterium (Methylobac
terium) (IJBousfield and PNGr)
een; Int.J.Syst.Bacteriol., 35,209 (1985), T. Urakami
etal .; Int. J. Syst. Bcteriol., 43, 504-513 (1993)). The cells obtained by continuous culturing were subjected to the method described in JP-A-7-17789.
According to the method for separating and purifying PHB described in 4 above, after crushing with a high-pressure homogenizer, centrifugation, the separated PHB was first treated with a protease, and then treated with hydrogen peroxide to obtain high-purity PHB. The PHB and PLA (Lacty part number 1012, manufactured by Shimadzu Corporation), calcium carbonate (NS100, manufactured by Nitto Powder Chemical Co., Ltd.), and boron nitride (SP2, manufactured by Denki Kagaku Kogyo Co., Ltd.) are mixed in advance in the proportions shown in Table 1. The mixture was pelletized using a screw type twin screw extruder (screw diameter: 45 mm). The pellet obtained in this manner was subjected to a mold clamping pressure of 100 ton / cm ^2.
, A tensile test, a bending test, a test piece for evaluating heat resistance, and a test piece for evaluating warpage were performed. that time,
The resin temperature was 185 ° C and the mold temperature was 30 ° C. Various measurements were made, and the test results are shown in Table 1.

Comparative Example 1 0.5% by weight of boron nitride was added to PHB purified from cells by the same method as in Examples 1 and 2, and pelletized using a screw type twin screw extruder. The pellets thus obtained were subjected to a tensile test, a bending test, a test piece for heat resistance evaluation and a test piece for warpage evaluation in the same manner as in Examples 1 to 4.
At that time, the resin temperature was 185 ° C. and the mold temperature was 30 ° C. Various measurements were made, and Table 2 shows the test results. Comparative Examples 2 to 3 PLA (Shimadzu Corporation, Lacty part number 1012) was subjected to the same method as in Examples 1 to 4 to produce a tensile test, a bending test, a test piece for evaluating heat resistance, and a test piece for evaluating warpage. At that time, the resin temperature was 210 ° C., and the mold temperature was 30 ° C. and 100 ° C. Various measurements were made, and Table 2 shows the test results. Comparative Example 4 Examples 1-4 except that the mixing ratio of PHB and PLA was changed
In the same manner as above, a tensile test, a bending test, a test piece for evaluating heat resistance and a test piece for evaluating warpage were produced. At that time, the resin temperature was 185 ° C. and the mold temperature was 30 ° C. Various measurements were made, and Table 2 shows the test results.

Comparative Example 5 A tensile test, a bending test, a test piece for evaluating heat resistance, and a test piece for evaluating warpage were performed in the same manner as in Examples 1 to 4 except that calcium carbonate was not blended. At that time, the resin temperature is 1
The test was performed at 85 ° C. and a mold temperature of 30 ° C. Perform various measurements,
Table 2 shows the test results. Comparative Example 6 A tensile test, a bending test, a test piece for evaluating heat resistance, and a test piece for evaluating warpage were performed in the same manner as in Examples 1 to 4, except that boron nitride was not blended. At that time, the resin temperature was 185
C. and a mold temperature of 30.degree. After various measurements, Table 2
Shows the test results. Comparative Example 7 A tensile test, a bending test, a test piece for evaluating heat resistance, and a test piece for evaluating warpage were performed in the same manner as in Example 1 except that the resin temperature was set to 185 ° C. and the mold temperature was set to 80 ° C. At that time, various measurements were made, and Table 2 shows the above test results.

[0018]

Table 1 Example 1 Example Example Example Example Comparative Example 1 2 3 4 1 Composition (wt% ) PHB 61.5 51.0 56.0 36.0 99.5 PLA 20.0 17.0 12.0 12.0 Calcium carbonate 18.0 30.0 30.0 50.0 Boron nitride 0.5 2.0 2.0 2.0 0.5 Mold temperature (℃) 30 30 30 30 30 Molding cycle time (sec) * 40 40 40 40 50 Tensile strength (kgf / cm ² ) 360 375 340 290 330 330 Tensile modulus (tonf / cm ² ) 47 50 50 60 30 bending strength ^{(kgf / cm 2) 522 550} 510 430 550 flexural modulus ^{(tonf / cm 2) 47 53} 50 75 36 heat resistance evaluation ** ○ ○ ○ ○ ○ warp rating *** ○ ○ ○ ○ × * tensile test Molding cycle time when molding a piece ** ○ Almost no change △ Little change was observed × Large change *** ○ Almost no change △ Little change was observed × Large change

[0019]

Table 2 Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example 2 3 4 5 6 7 Composition (wt% ) PHB 19.5 61.5 61.5 61.5 PLA 100.0 100.0 56.0 38.0 20.0 20.0 Calcium carbonate 24.0 18.5 18.0 Boron nitride 0.5 0.5 0.5 Mold temperature (° C) 30 100 30 30 30 80 Molding cycle time (sec) * 70> 500 40 55 65 110 Tensile strength (kgf / cm ² ) 660 490 330 350 300 Tensile modulus (tonf / cm ² ) 36 52 31 45 47 Flexural strength (kgf / cm ² ) 1000 670 820 530 450 Flexural modulus (tonf / cm ² ) 35 46 36 42 40 Heat resistance evaluation ** × △ ○ △ ○ Warpage evaluation *** ○ ○ × △ × * Molding cycle time when molding tensile test pieces ** ○ Almost no change △ Slight change was observed × Large change *** ○ Almost no change △ Slight change was observed × Large change

Claims (5)

[Claims] 1. Poly-3-hydroxybutyric acid, polylactic acid,
A biodegradable low-warping molding material obtained by melting and mixing an inorganic filler and a crystal nucleating agent. 2. The biodegradable low warpage molding material according to claim 1, wherein the weight of poly-3-hydroxybutyric acid is 50% to 90% based on the sum of the weights of poly-3-hydroxybutyric acid and polylactic acid. . 3. The low biodegradable material according to claim 1, wherein calcium carbonate is used as the inorganic filler, and the compounding amount of the calcium carbonate with respect to the low biodegradable molding material is 10 to 60% by weight. Warpage molding material. 4. The method according to claim 1, wherein boron nitride is used as a crystal nucleating agent, and the compounding amount of the boron nitride with respect to the biodegradable low warpage molding material is 0.3 to 5.0% by weight. Low biodegradable molding material. 5. The resin material at the time of molding the biodegradable low-warpage molding material according to claim 1, wherein the resin temperature is 130 to 25.
A method for molding a biodegradable low warpage material, wherein the molding is performed at 0 ° C. and a mold temperature of 0 to 70 ° C.