JP2001253964A - Biodegradable polylactic foam board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable foam board which holds biodegradability, has a light weight, can reduce the use of the polylactate of raw material, has dense cells, excellent elasticity, excellent recovering force, sufficient flexibility, and sufficient secondary processability, and can be processed into a secondary formed article having excellent impact resistance, good dimensional stability, and so on. SOLUTION: This biodegradable polylactic foam board 10 having a density of 0.5 to 1.05 g/cm3 and a thickness of 1 to 8 mm. The foam board can be produced by a method of producing the biodegradable polylactate foam board, characterized by dry-blending biodegradable polylactate pellets especially dried at a temp. of 45 to 60 deg.C with a foaming agent, a lubricant and a nucleating agent, subjecting the mixture to an extrusion foaming molding in a cylinder temperature condition of 120 to 210 deg.C and in a die temperature condition of 110 to 170 deg.C to form the long molded article, subjecting the obtained long molded article to a wave-removing treatment, and then pressing the product with forming rolls kept ate a temp. of <=50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable polylactic acid foam board method, and more particularly, to a biodegradable polylactic acid foam board method which has a substantially uniform wall thickness even when subjected to deep drawing while maintaining biodegradability. The present invention relates to a biodegradable polylactic acid foam board which is excellent in dimensional stability and the like and can be formed into a secondary processed product having a moderate stiffness.

[0002]

2. Description of the Related Art Recently, a foam board made of plastic,
In particular, foamed boards made of extruders include foamed polystyrene, foamed polyethylene, foamed polypropylene, etc., which are widely used in a wide variety of fields because they have excellent secondary moldability in addition to light weight, heat insulation, soundproofing, cushioning, etc. Have been. However, they are hardly decomposed in the natural environment, and are accumulated in the natural world, causing serious environmental and ecological problems such as shortage of landfills, soil, river and ocean pollution. On the other hand, even if an attempt is made to recover and reuse the material, it is bulky and the recovery cost is high. Further, there are problems such as damage to the incinerator at the time of incineration, generation of toxic gas, etc., so that recovery and regeneration are extremely difficult.

[0003] As one of such environmental load suppressing means, there is a demand for the development of a biodegradable polymer which is decomposed by microorganisms in the soil or water, incorporated into a natural material circulation system, and does not pollute the environment. As these biodegradable polymers, various synthetic and natural polymers are known, including polyhydroxybutyrate, polylactic acid, polycaprolactone, cellulose, chitosan, starch and the like. Further, there are those which use polyvinyl alcohol, polyethylene, ethylene / vinyl acetate copolymer and the like as improvers for cellulose, starch and the like which are difficult to process.
No. 7 discloses a technology relating to a foam such as a natural product mainly comprising a polysaccharide such as corn starch or a derivative thereof.

On the other hand, lactic acid-based polymers have attracted attention as environmentally-friendly polymers because of their high stability and low calories burned during incineration, and lactic acid polymers such as copolymers of polylactic acid and ε-caprolactone. Regarding the foam of the polyester, for example, JP-A-4-304244, JP-A-5-140361, JP-A-6-287347
And Japanese Patent Publication No. 5-508669.

[0005] However, the conventional polylactic acid foam is excellent in biodegradability, but poor in elasticity and restoring force.
It has the drawback of being brittle against mechanical shock, and the copolymer of lactic acid and ε-caprolactone is relatively flexible, but has poor heat resistance, so a stable molded product can be obtained during secondary molding. There is a problem that it is difficult to use it for a limited purpose.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to achieve, in particular, while maintaining biodegradability,
In addition, it has sufficient flexibility, excellent impact resistance and secondary molding processability, and has good dimensional stability of secondary molded products, and aims to provide a polylactic acid foam board useful for various applications. Things.

[0007]

The gist of the means adopted by the present invention to achieve the above object is as set forth in the appended claims.

According to the biodegradable polylactic acid foam board according to the first aspect of the present invention, a lightweight and lightweight polylactic acid raw material can be reduced while maintaining biodegradability. The biodegradable foam board has sufficient flexibility and secondary molding processability, and can be used to form secondary molded products with excellent impact resistance and good dimensional stability. It can be used for various applications.

According to the biodegradable polylactic acid foam board according to the second aspect of the present invention, in addition to the effect obtained by the biodegradable polylactic acid foam board according to the first aspect of the present invention, particularly, immediately after extrusion, Even if the high-temperature foam board is rapidly cooled to the glass transition temperature or lower, uneven cooling and insufficient cooling hardly occur, so that wrinkles and tears hardly occur due to variations in expansion ratio and crystallinity, and It can be provided as a cleanly finished biodegradable foam board having deep drawing secondary formability.

According to the biodegradable polylactic acid foam board according to the third aspect of the present invention, in addition to the action of the biodegradable polylactic acid resin pellet according to the first or second aspect of the present invention, in particular, polylactic acid The moisture content of the pellets is 75 to 250
If it is ppm, it can be provided as a biodegradable foam board having a deep drawing secondary formability formed into a clean flat surface. Further, the water content of the polylactic acid pellets is 20 to
When it is about 75 ppm, it can be provided as a biodegradable foam board having an embossed surface shape, and the embossed surface shape can be maintained as it is even after deep drawing secondary forming.

According to the biodegradable polylactic acid foam board according to the fourth aspect of the present invention, the biodegradable polylactic acid resin pellet according to any one of the first to third aspects of the present invention has an effect, especially The cell can be provided as a biodegradable foam board having dense cells and excellent elasticity and restoring force.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below in detail.

First, the biodegradable polylactic acid foam board of the present invention comprises: (1) a step of dry blending a foaming agent, a lubricant and a nucleating agent with biodegradable polylactic acid pellets dried at 45 to 60 ° C. (2) The obtained mixture was subjected to a cylinder temperature condition of 120 to 190 ° C. and a die temperature condition of 110 to 17
Extrusion foam molding into a long shape at 0 ° C., a wave-removing process, (3) a step of pressing with a forming roll maintained at 50 ° C. or lower, and (4) a continuous take-up device. It can be manufactured by a method having a step of drawing out and cutting to an appropriate length.

The biodegradable polylactic acid pellets are heated in a hot air dryer at about 40 ° C. for about 5 to 6 hours, and at 60 ° C. for about 1.3 to about 1.3 hours.
Drying is performed for about 5 hours. When the drying temperature is 40 ° C. or lower, the drying state of the polylactic acid pellets becomes insufficient even after continuous drying for a long time (because the moisture content is too high). Streaks,
Furthermore, the resulting foam board itself tends to be brittle. On the other hand, when the drying temperature is 60 ° C. or higher, the polylactic acid pellets tend to stick together in the hopper to form a lump and cannot be subjected to extrusion foaming, or the foam board itself tends to be hard and brittle. is there.

Further, the polylactic acid pellets must be dried so that the water content thereof is in the range of 10 to 250 ppm. When the water content is 10 ppm or less, so-called "measuring" tends to occur on the surface of the foam board, and when the water content is 250 ppm or more, as described above, water bubbles and vertical Streaks are formed, and the resulting foam board itself tends to be brittle.

The water content of the polylactic acid pellets tends to affect the surface shape of the foamed board obtained by foaming. Water content of polylactic acid pellets is 75-250pp
When it is m, a biodegradable foam board having a deep drawing secondary formability formed into a flat surface with a beautiful surface is obtained.

In particular, the polylactic acid pellets have a water content of 20 to
When it is about 75 ppm, a biodegradable foam board having a surface shape as if embossed can be molded with good reproducibility, and the embossed surface shape is maintained as it is even after deep drawing secondary molding. This is suitable because a secondary molded product can be molded.

More specifically, the foaming agents include sodium bicarbonate, ammonium bicarbonate, and inorganic foaming agents.
Examples thereof include ammonium carbonate, sodium borohydride, and azide compounds. Organic blowing agents include azo compounds represented by azodicarbonamide and azobisisobutyronitrile, sulfonyl hydrazide compounds represented by oxysbenzenesulfonyl hydrazide, and nitroso compounds represented by dinitrosopentamethylenetetramine. , Etc. can be exemplified. These foaming agents may be used alone or in combination of two or more, but when an azo compound-based foaming agent is used, the cells are dense and have excellent elasticity and resilience. It becomes a biodegradable foam board.

The mixing ratio of the foaming agent is 100
The ratio is 0.2 to 2.0 parts by weight, preferably 0.5 to 1.2 parts by weight based on parts by weight. It goes without saying that the amount of the foaming agent used is an amount necessary for obtaining a desired expansion ratio.

Next, the dried polylactic acid pellets are melted in a cylinder in the step (2), and then extruded and foamed into a long shape from a die. Upon exiting the die, the plate-shaped extrudate expands to a certain magnification according to the resin temperature, the die shape, and the like. Suitable temperature conditions for the cylinder are 130-190 ° C, die temperatures are 110-170 ° C, preferably 140-170 ° C.
° C. As the dice, for example, a T-die, a circular die, or the like can be used.

Since the surface of the foamed board obtained by opening to the atmosphere from the die has a tendency to generate corrugation (corrugation), the foamed board immediately after extrusion is subjected to a corrugating treatment and the resin itself is treated. It is preferable to mold the foamed board while pressing with a cooling roll because of its adhesiveness. While being cooled by a plurality of cooling rolls, it is continuously formed by a take-off device and cut into a desired size and shape by a suitable cutting means having, for example, a blade. Can be manufactured. It is also possible to adopt a configuration in which the foam board immediately after extrusion is subjected to a wave-removing process, pressed with a cooling roll to finish the surface neatly, and then passed through a water tank to be cooled.

The density of the biodegradable polylactic acid foam board thus produced is preferably 0.5 to 1.05 g / cm.
³ If the density exceeds 1.05 g / cm ³ , there are few bubbles in the foamed board, and the excellent properties of the foamed board, such as heat insulation and weight reduction, are not sufficiently exhibited. 0.5g density
If it is lower than / cm ³ , the foam content in the foamed board is too large, so that the formability in secondary processing tends to decrease.

The thickness of the foam board is preferably 1 to 8 mm. A plate-like foam thinner than 1 mm is extremely difficult to produce, and even if it can be produced, there are few bubbles in the foam, and the excellent properties of the foam such as heat insulation and weight reduction often do not appear sufficiently. Further, it is difficult to extrude and foam a foam having a thickness of more than 8 mm so that the thickness becomes uniform.

The foamed board can be formed by a known method such as a vacuum molding method or a compressed air molding method without causing drawdown (without losing excellent properties as a foamed board) and biodegradable properties. Without losing
It can be formed into various secondary products.

It should be noted that, in the present invention, anti-measuring agent, pigment, antioxidant,
It goes without saying that a weather resistance improver, an antistatic agent and the like can be contained.

[0026]

EXAMPLES The present invention will be described more specifically below with reference to examples, but the present invention is not limited thereto.

Polylactic acid virgin pellets purchased from Kanebo Gosen Co., Ltd. (trade name “Lactron 700D”)
A)) Regenerated 100 parts by weight "Lactron 700DA" 2
The mixed pellets obtained by mixing 0 parts by weight, with a hot air drier,
After drying at 60 ° C. for 3.0 hours, 100 parts by weight of the obtained dried pellets was added with “DS # 2” as a foaming agent.
5 ") 0.8 parts by weight of drive and 0.5 parts by weight of talc as a nucleating agent are drive-blended, and the resulting mixture is extruded into an extruder having a diameter of 1
A T-die 2 with a clearance of 0.9 mm was attached to 30φ, and extruded and foamed into a long shape at a cylinder temperature condition of 130 to 190 ° C and a die temperature of 145 to 155 ° C. "DS # 25" used as a foaming agent is manufactured by Eiwa Chemical Co., Ltd. and is an azo compound-based composite foaming agent composed of azodicarbonamide and oxybisbenzenesulfonylhydrazide.

Since the surface of the obtained foam board 10 tends to generate corrugation (corrugation), the foam is immediately subjected to a corrugating treatment and then pressed by the cooling roll 3 cooled to 35 ° C. While being processed, it is processed into a plate-like foam molded board, and if necessary, passed through a water bath to be cooled. And
When continuously formed by the take-off device 4 while being cooled by the plurality of cooling rolls 5 and 5, and cut into a desired size and shape by the cutter 6, a biodegradable polylactic acid foam board as a final product can be manufactured. (FIG. 1).

The density of the foam board thus produced is preferably 0.5 to 1.05 g / cm ³ . If the density is more than 1.05 g / cm ³ , the foamed board tends to have insufficient heat insulation and light weight, which are the excellent properties, because the air bubbles in the foamed board are small. Those lower than 0.5 g / cm ³
Probably because the foam content in the foam board is too large, the formability in secondary processing tends to be remarkably reduced.

It is also possible to adopt a configuration in which the foaming board immediately after extrusion is subjected to a wave-removing process, pressed with a cooling roll to finish the surface neatly, and further cooled while being pressed with a cooling roll. Thus, a long foam board having a beautiful surface could be manufactured.

The foam board thus obtained was formed into a lunch box shape by a vacuum and pressure forming method, and a secondary molded product having a clean surface and a unique texture without drawdown was obtained. Could be formed.

When this polylactic acid foamed lunch box was pulverized with a hammer and composted, the form did not remain within 1 to 2 months, and good biodegradability was exhibited.

[0033]

As described above, according to the polylactic acid foam board of the present invention, it is possible to reduce the amount of polylactic acid used as a raw material while maintaining biodegradability, and reduce the amount of polylactic acid used as a raw material. Biodegradable foam board that has excellent elasticity, restoring force, sufficient flexibility and secondary moldability, and can be molded into secondary molded products with excellent impact resistance and good dimensional stability. Can be provided extremely stably.

By appropriately adjusting the water content of the polylactic acid pellets, a foam board having an embossed surface can be manufactured. It can maintain the embossed shape, can be used for various applications, and can reuse damaged or unnecessary final products and non-standard products at the time of molding. It is also advantageous from the viewpoint of the present invention, and an extremely effective action and effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart schematically showing a manufacturing method for manufacturing an elongated foam board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hopper 2 ... T-die 3 ... Forming roll 4 ... Take-up device 5 ... Forming roll 6 ... Cutter 10 ... Foam board

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 B29L 7:00 C08L 67:04 C08L 67:04 (72) Inventor Yukio Uesaka Takefu-shi, Fukui Shinji Hayashi, 3 characters, 1 Oppushi-cho Kogyo Kogyo Co., Ltd. (72) Inventor: Shinji Hayashi 3rd, 1st character, 1 Oppachi-cho, Happo Chemical Co., Ltd., Takefu-shi, Fukui Prefecture (72) Eiji Kageyama, Mino City, Gifu Prefecture 648 Jindo 1 Tokai Kaseinai Co., Ltd. (72) Inventor Kenji Tanaka 4045 Noda Nitta, Hozumi-cho, Motosu-gun, Gifu Prefecture Inside Pearl Mannequin Co., Ltd. (72) Inventor Saburo Morita 4045 Noda Nitta, Hozumi-cho, Motosu-gun, Gifu Prefecture F-term (reference) in Pearl Mannequin Co., Ltd. 4F074 AA68 AF05 BA03 BA04 BA08 BA13 BA14 BA16 BA18 CA22 CC22X CC28X CC32Y CC34Z DA02 DA23 DA24 DA33 4F2 07 AA01 AA24 AB02 AB07 AB08 AC01 AE10 AG02 AG20 AH55 AH56 AH58 AR06 KA01 KA11 KF01 KL84 KM14 KM15 KW23 KW26 KW41 KW45

Claims (5)

[Claims] 1. A mixture obtained by dry-blending a foaming agent, a lubricant and a nucleating agent on biodegradable polylactic acid pellets dried at 45 to 60 ° C. is subjected to a cylinder temperature condition of 12.
0-210, die temperature conditions 110-170 ° C, extruded and foamed into a long shape at a temperature of 110-170 ° C, and after a wave removal treatment, a biodegradable polylactic acid foam board pressed by a forming roll held at 50 ° C or less. The density of the biodegradable polylactic acid foam board is 0.5-1.
A biodegradable polylactic acid foam board having a weight within a range of 05 g / cm ³ . 2. The biodegradable polylactic acid foam according to claim 1, wherein the biodegradable polylactic acid resin pellet contains 1% by weight or more of amorphous biodegradable polylactic acid. board. 3. The method for producing a biodegradable polylactic acid foam board according to claim 1, wherein the water content of the biodegradable polylactic acid pellets is from 20 to 250 ppm. 4. The method according to claim 1, wherein the foaming agent is an azo compound, and 0.2 to 2 parts by weight per 100 parts by weight of the biodegradable polylactic acid pellets.
The composition according to claim 1, which is blended at a ratio of 0 parts by weight.
4. The biodegradable polylactic acid foam board according to any one of 3. 5. The biodegradable polylactic acid foam according to claim 1, wherein the thickness of the biodegradable polylactic acid foam board is in the range of 0.5 to 8 mm. board.