JP2010222482A - Plant-derived biodegradable synthetic resin sheet and container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable synthetic resin sheet made from a plant-derived raw material in which weatherability of a polyolefin resin is changed into biodegradability, and other strong points of the polyolefin resin are held as they are, and to provide a biodegradable container made from such a sheet. <P>SOLUTION: A mixture is obtained by adding, to 100 wt.pts. of a plant-derived polyolefin resin, 10-100 pts.wt. of a terpolymer obtained by polycondensation of a plant-derived succinic acid, a plant-derived 1,4-butanediol, and a plant-derived lactic acid. The mixture is then subjected to heat kneading to form a sheet, which is then molded to form a plant-derived container. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plant-derived biodegradable synthetic resin sheet and a container. In particular, the present invention relates to a plant-derived synthetic resin sheet and container that will not decompose and retain their original shape when left for a period of time under natural conditions.

  Sheets made of polyolefin resin are currently widely used as sheets for forming containers for food and the like, and as sheets for waterproofing and heat retention. The polyolefin resin is harmless, impervious to water, strong and flexible, and can be easily formed into a sheet or container. This is because it has many advantages such as excellent dimensional stability and weather resistance.

  However, the excellent weather resistance of polyolefin resins has recently been regarded as a drawback. The reason is that sheets and containers made of polyolefin resin are used for a long time after they are no longer useful and are kept in their original form because of their excellent weather resistance. For this reason, sheets and containers are deposited as garbage, which makes the environment worse.

  In order to dispose of such sheets and containers, they must be incinerated. However, incineration requires not only large-scale incineration equipment, but a large amount of carbon dioxide is generated during incineration. The generation of carbon dioxide promotes global warming and harms the environment. If the incineration is poor, other harmful gases are generated, which directly damage human livestock. Therefore, the use of sheets and containers made of polyolefin-based resins has been limited.

  On the other hand, some synthetic resins have biodegradability. When the biodegradable synthetic resin is left for a while under natural conditions, it is decomposed naturally by the action of sunlight, rain, or bacteria, and becomes harmless like water and carbon dioxide. As synthetic resins having such properties, polylactic acid resins and aliphatic polyester resins are known.

  The polylactic acid resin is a thermoplastic resin obtained by polymerizing lactic acid. Since lactic acid contains asymmetric carbon atoms, not only is it complicated to produce two optical isomers, levorotatory and dextrorotatory, but there are various polymerization methods, so polylactic acid covers a wide range. The physical properties will change. However, generally speaking, polylactic acid is a crystalline hard resin and lacks flexibility. Therefore, a sheet made of a polylactic acid resin is easily cracked when subjected to an impact, is not easily bent, and cracks when bent forcibly.

  The aliphatic polyester resin is a thermoplastic resin obtained by condensing a dibasic acid and a divalent alcohol. Therefore, the physical properties of the polyester resin vary greatly depending on what is used for the dibasic acid and the dihydric alcohol. Generally speaking, aliphatic polyester resins are more flexible than polylactic acid resins.

  Therefore, an attempt has been made to improve the impact resistance of polylactic acid by adding an aliphatic polyester resin to polylactic acid. Japanese Patent Application Laid-Open No. 2006-206670 provides a biodegradable synthetic resin sheet in which polybutylene succinate is blended with polylactic acid and is not easily broken even under impact. However, the sheet lacks flexibility and is not as flexible as polyolefin resin.

  In general, it is known that two types of thermoplastic resins having different physical properties are mixed to make a composition, and that the drawbacks of one resin are compensated by the advantages of other resins to make an improved resin composition. Yes. In making the composition, it is said that the resins to be mixed must have good compatibility. If the compatibility is not good, the two resins in the composition are separated to form separate phases, and in extreme cases, the resin is separated into two layers and cannot be a proper product.

  Since the polyolefin resin is composed of molecules having no polarity, and the aliphatic polyester resin is composed of molecules having polarity, the polyolefin resin and the aliphatic polyester resin are not inherently compatible. Therefore, it has not been attempted so much to mix an aliphatic polyester resin with a polyolefin resin to form a composition.

  JP-A-6-263892 describes that an aliphatic polyester resin is added to a polyolefin resin to produce a biodegradable synthetic resin film. As described above, since the two resins are not compatible with each other, this publication proposes that a compatibilizing agent is further added thereto. The compatibilizer must be a “graft polymer having a comb-type structure synthesized by a macromonomer method having a compatible group of an acid or epoxy-modified functional group and a polyolefin resin”. Has been. Since such a graft polymer is a complex compound, its implementation is not easy.

JP 2006-206670 A JP-A-6-263892

  The present invention provides a biodegradable sheet made of a plant-derived raw material that leaves most of the advantages of a polyolefin-based resin, but only weakens the weather resistance and imparts some biodegradability, thereby providing a polyolefin This is to improve the hesitation in using the resin-based resin sheet.

  In order to solve the above problems, the inventor blended various thermoplastic resins with a polyolefin resin to form a composition, molded the composition into a sheet, and measured the physical properties of the obtained sheet. As a result, when a specific aliphatic polyester resin is blended with a polyolefin-based resin, the resulting composition is well compatible with each other and does not need to be added as a compatibilizing agent to form a uniform composition. I found. It was also found that the obtained composition can be easily formed into a sheet, and the obtained sheet retains the advantages of the polyolefin resin sheet and has biodegradability. The present invention has been completed based on such knowledge.

  The specific aliphatic polyester resin to be blended with the polyolefin resin is a copolymer obtained by copolymerizing a small amount of lactic acid with polobutylene succinate. That is, this polyester resin was made into polybutylene succinate using succinic acid as a dibasic fatty acid and 1,4-butanediol as a divalent aliphatic alcohol, and lactic acid was copolymerized therewith. Is. Since this polyester resin is a polycondensation of succinic acid, 1,4-butanediol and lactic acid, it will be referred to as a terpolymer below.

  In blending the terpolymer with the polyolefin resin, the latter is 10 to 100 parts by weight with respect to the former 100 parts. The reason is that if the terpolymer is less than 10 parts, the resulting sheet is not sufficiently biodegradable, and conversely if it exceeds 100 parts, both resins are compatible. This is because it becomes difficult to obtain a uniform composition. However, when the number of terpolymers is further increased to 9 or more times that of polyolefin resin, both resins form a uniform composition, but such a composition loses the properties of polyolefin resin. So it does not fit the purpose.

This invention was obtained by adding 10 to 100 parts of a terpolymer formed by polycondensation of succinic acid, 1,4-butanediol, and lactic acid to 100 parts of a polyolefin resin by weight. The present invention provides a biodegradable synthetic resin sheet obtained by kneading a mixture under heating and forming it into a sheet shape.
The above terpolymer is a composition obtained by polycondensation of 47 to 49.5 mol% succinic acid, succinic acid and equimolar% 1,4-butanediol, and 1 to 6 mol% lactic acid. It is preferable that.

  In this invention, both the polyolefin-based resin and the ternary copolymer are derived from plants. Plants contain starch, sugar and fibrin. These break down into glucose. Glucose can be fermented into lactic acid or succinic acid. Further, succinic acid can be hydrogenated to 1,4-butanediol. It is also possible to make ethylene from glucose and polymerize ethylene to make polyethylene. Therefore, in this invention, all raw materials can be derived from plants.

A mixture obtained by mixing a polyolefin-based resin and a ternary copolymer in the above-described proportions becomes a uniform composition by itself when heated and kneaded. An extruder is preferably used for heating and kneading, but a normal resin processing apparatus such as a heating roll can also be used.
In order to form this composition into a sheet, it is preferable to use an extruder, but an apparatus such as a heating roll can also be used.

  In this invention, it is preferable that the thickness of the sheet made from the composition is in the range of 0.05 to 2.2 mm. This is because if the thickness is smaller than 0.05 mm, a thick portion and a thin portion extending in the width direction of the sheet are generated and scattered in the longitudinal direction, so that a high-quality sheet cannot be obtained. On the other hand, if the thickness exceeds 2.2 mm, the sheet surface becomes unsmooth, and a sheet with good arrow tension cannot be obtained.

  The polyolefin resin that can be used in the present invention is a homopolymer of ethylene, propylene, and butene, and a copolymer thereof. Examples include low density polyethylene, high density polyethylene, polypropylene, propylene-ethylene copolymer, propylene-butene copolymer, and the like.

  According to the present invention, three parts obtained by polycondensing three parts of plant-derived succinic acid, plant-derived 1,4-butanediol, and plant-derived lactic acid to 100 parts of a plant-derived polyolefin resin by weight. Since a mixture to which 10 to 100 parts of the original copolymer is added is used, when this mixture is heated and kneaded, it becomes a uniform composition easily by itself without adding a special compatibilizer. Moreover, the obtained composition can be easily formed into a sheet, the formed sheet is harmless and does not allow water to pass through, and retains the advantages of polyolefin resin such as flexibility and dimensional stability. Only the weather resistance is weakened and it has biodegradability. Therefore, it meets all recent requirements.

In particular, as a terpolymer, succinic acid is 47 to 49.5 mol%, 1,4-butanediol is equimolar to succinic acid, and lactic acid is 1 to 6 mol%. Can be used to more reliably obtain the above sheet, and the obtained sheet not only has the same advantages as the polyolefin resin sheet but also has biodegradability, and the polyolefin resin sheet. It is even more glossy.
Moreover, by setting the thickness of the sheet within the range of 0.05 to 2.2 mm, it is possible to easily and reliably obtain a sheet having no uneven thickness and a smooth surface.

  Moreover, since the obtained sheet | seat has the physical property similar to the sheet | seat made from polyolefin resin derived from petroleum, it can be used as a waterproof and heat insulation sheet | seat. Further, the sheet can be easily formed into a desired container shape by vacuum forming, vacuum pressure forming or the like. Since the container thus obtained is harmless like a polyolefin resin container, it is suitable for storing personal items such as food and cosmetics. In addition, the sheets and containers are left to stand after use, so that they cannot be naturally decomposed and remain in their molded shapes. Finally, they are decomposed and become harmless, so the environment is not polluted.

  In the biodegradation of the sheet according to the present invention, the terpolymer contained therein is only decomposed by sunlight, rain, or bacteria, and the other polyolefin resin is not decomposed. However, since the ternary copolymer and the polyolefin resin are mixed in the sheet to form a uniform composition, when the terpolymer is decomposed, the polyolefin resin falls apart or has pores. The original sheet shape cannot be retained. As a result, the sheet is in the same state as when the sheet is completely disassembled.

In the present invention, the raw materials used are all plant-derived as described above. Since plant-derived materials are used, the carbon dioxide generated by incineration originates from the carbon originally contained in the plant, so there is no change in the total amount of carbon dioxide in the atmosphere. Will not be generated. Carbon dioxide generated by incineration is again absorbed by the plant by photosynthesis and becomes a component of the plant. Thus, since what became the component of the plant is utilized as a polyolefin and a terpolymer in the present invention, carbon dioxide is completely circulated. Therefore, environmental pollution is eliminated.
The present invention provides such an effect.

It is the model which showed the process of manufacturing a sheet | seat by this invention.

  The polyolefin-based resin that can be used in the present invention is a homopolymer or copolymer of ethylene, propylene, and butene as described above. Polyethylene has a melt flow rate (MFR) in the range of 0.5 to 10 under the conditions of a temperature of 190 ° C. and a load of 2160 g, a melting point of 90 to 135 ° C., and a number average molecular weight (Mn) of 40000 to 400,000. Those having a weight average molecular weight (Mw) in the range of 100,000 to 1,000,000 can be used.

  In addition, polypropylene has an MFR of 0.5 to 15 under the conditions of a temperature of 230 ° C. and a load of 2160 g, a melting point of 110 to 150 ° C., an Mn of 250,000 to 2500,000, and an Mw of 100,000 to 1,000,000. Those within the range can be used.

  As described above, typical terpolymers used in the present invention are 47 to 49.5 mol% of succinic acid, equimolar% of 1,4-butanediol and succinic acid, and 1 to 4 of lactic acid. It is a copolymer formed by polycondensation of 6 mol%. The MFR of such a terpolymer is 0.5 to 20 under the conditions of a temperature of 190 ° C. and a load of 2160 g, a melting point is 80 to 120 ° C., a glass transition point is −70 to 0 ° C., and Mw is It is in the range of 10,000 to 1,000,000. In particular, Mw is preferably from 30,000 to 800,000, most preferably from 50,000 to 600,000.

  In the present invention, a mixture obtained by mixing 10 to 100 parts by weight of a terpolymer with 100 parts by weight of a polyolefin resin is heated and kneaded to obtain a sheet. Of these, the terpolymer is preferably 30 to 80 parts by weight.

In order to make the composition uniform, the above mixture is put into an extruder and heated to 130 to 150 ° C., and once formed into pellets. The pellets thus obtained are put into the extruder again, and the cylinder temperature is set to 180 to 200 ° C., the die temperature is set to 170 to 210 ° C., and the sheet is extruded from the T die to form a sheet. FIG. 1 shows the state when a sheet is formed.
In FIG. 1, the extruded sheet is first cooled by coming into contact with the cooling roll unit, and then taken up by the take-up roll unit and taken up by a winder.

  As described above, the sheet thus obtained is different in that the weather resistance is improved to biodegradability, and other than that, the advantages of the polyolefin resin are substantially maintained. In other words, it is harmless, flexible, tough, water resistant, translucent, but slightly glossier than polyolefin resin sheets, and can be easily heated to form a container, resulting in improved results. It has degradability.

  Therefore, this sheet can be used temporarily for the purpose of waterproofing and heat insulation. For example, it can be laid as a multi-seat for agriculture on a field and left to be disassembled after use. In addition, the sheet can be secondarily formed by a vacuum forming method or the like to form a container, filled with food, etc., and left to stand for natural decomposition after use. Therefore, it is not necessary to incinerate and the environment is prevented from being polluted.

This sheet can be easily secondarily formed into a container by a known vacuum forming method or the like. For example, the sheet is heated from both sides by a sheathed heater to soften the sheet, then the sheet is moved onto the mold, the plug is lowered from above, and a part of the sheet is forced into the mold, The sheet around the mold is brought into close contact with the mold, and the air in the mold is sucked to bring the sheet into close contact with the inner surface of the mold. Next, the plug is removed, the sheet is transferred onto another mold, cooled in another mold and solidified, and then the sheet is removed from the mold and the edge is cut out to form a container.
The container thus obtained can be used to contain food such as curry roux, miso, soup roux, and instant food.

Next, examples and comparative examples will be described to explain the excellent effects of the present invention, but the present invention is not limited to the examples.
Examples 1-6 and Comparative Examples 1-4
1. Details of raw materials used 1) Polypropylene (PP)
A random polymer was used as PP. The MFR (210 ° C. load 2160 g) was 10.7, the melting point was 137.4 ° C., the crystallization temperature was 94.1 ° C., Mn was 79200, Mw was 206300, and Mw / Mn was 2.60.
2) Polyethylene (PE)
As the PE, low density polyethylene was used. The MFR (180 ° C. load 2160 g) was 3.0, the melting point was 113 ° C., Mn was 32000, Mw was 72000, and Mw / Mn was 2.25.
3) Ternary copolymer As the ternary copolymer, a polycondensate was used at a ratio of 48.5 mol% succinic acid, 48.5 mol% 1,4-butanediol, and 3 mol% lactic acid. The MFR (180 ° C. load 2160 g) was 4.2, the melting point was 110 ° C., the glass transition point was 24 ° C., and the Mw was 10,000 or more.

2. Extrusion sheet molding 1) Equipment used L / D was 25 in a single screw extruder. This was a T-die type sheet molding machine, and the die width was 200 mm.
2) Heater temperature The cylinder was 180 ° C on the hopper side, 200 ° C at the center and tip of the cylinder, and 200 ° C at the die.
3) Sheet molding method The ternary copolymer was dried at 80 ° C for 24 hours using a shelf-type hot air dryer.
After drying, the ternary copolymer was mixed with PP or PE at a mixing ratio described in Table 1 using a mixer. First, pellets were prepared, and then the pellets were again charged into the extruder.

The temperature of the extruder was set as described above, and the mixed resin was extruded from the T-die outlet. The extruded resin was cooled and solidified while being shaped into a sheet by a cooling roll unit. Thereafter, the solidified resin sheet was taken up by a take-up roll unit and taken up in a roll shape by a winder.
4) Evaluation of resin dispersibility and sheet surface condition By visually observing the appearance of the resin sheet obtained in 3), the dispersibility of the resin and the smoothness of the sheet surface were evaluated. The evaluation results are shown in Table 1.
In Table 1, o indicates that the dispersibility of the resin or the smoothness of the sheet surface was good. On the other hand, x indicates that the dispersibility of the resin or the smoothness of the sheet surface is not good.

5) Consideration According to Table 1, when the terpolymer is more than 100 parts by weight with respect to 100 parts by weight of PP or PE, the surface state of the resin sheet becomes unsmooth, and the resin dispersion becomes poor and uneven. Appeared. On the other hand, when the terpolymer was 10 to 100 parts by weight, both the dispersibility of the resin and the smoothness of the sheet surface were good. Although not shown in Table 1, both the dispersibility of the resin and the gloss of the sheet surface were even better especially when the terpolymer was in the range of 30 to 80 parts by weight.

3. Vacuum processing molding 1) Equipment used Vacuum molding testing machine 2) Mold used Cuboid container Vertical 35mm x Horizontal 65mm x Height 18mm Recessed plug Assist use 3) Cooling method Air pressure air cooling 4) Extruded sheet described in method 2 The resin sheet obtained by molding was vacuum-formed as follows into a container.
Specifically, first, using a sheathed heater, the resin sheet was electrically heated for 10 to 20 seconds to be softened (sheet surface temperature of about 130 to 150 ° C.). Next, the softened resin sheet was set on a mold, the plug was lowered from above the sheet, and the resin sheet was pushed into the mold together with the sheet, and the pushed sheet was adsorbed to the mold by vacuum force. Next, the sheet was cooled and solidified by blowing cooling air onto the resin sheet adsorbed on the mold. And the container was obtained by removing the solidified molded article from a metal mold | die.

5) Evaluation of vacuum forming appearance By visually observing the appearance of the container obtained in 4), the workability of vacuum forming was evaluated. The evaluation results are shown in Table 1.
“◯” shown in the column of vacuum forming in Table 1 indicates that the container had no holes, no uneven thickness, no resin wrinkles, and the like, and the appearance was good. On the other hand, x indicates that there was some defect as described above in the appearance as a container.

6) Consideration As shown in Table 1, the resin sheet with poor sheet surface condition or resin dispersion cannot be used as a product because the container obtained by vacuum forming has some disadvantages as described above. there were. On the other hand, in the resin sheet in which the sheet surface state and the resin dispersion were good, the container obtained by vacuum forming maintained a good appearance.
From the above, a resin sheet excellent in molding processability and a good quality secondary processed product can be obtained by setting the terpolymer to a ratio of 10 to 100 parts by weight with respect to 100 parts by weight of PP or PE. It could be confirmed.

4). Relationship between Sheet Thickness and Sheet Appearance 1) Resin sheets having different thicknesses were prepared by the extrusion sheet forming method described in 2 above using a resin in which 100 parts by weight of PP and 100 parts by weight of terpolymer were mixed. Kinds were made. The appearance of the sheet was evaluated by visually observing seven types of resin sheets. The evaluation results are shown in Table 2.
In Table 2, ◯ indicates that the sheet state (sheet appearance), surface state (sheet surface smoothness), and thickness stability (there is no variation in sheet thickness) are good. On the other hand, x indicates that the state is not good.

2) Consideration When the thickness of the sheet was less than 0.05 mm, uneven elongation of the resin occurred in the sheet extrusion direction, and the variation in sheet thickness was confirmed.
Further, when the sheet thickness exceeded 2.2 mm, the smoothness of the sheet surface was lost, and unevenness was confirmed as a whole. Moreover, since the sheet was too thick, the cooling in the cooling roll unit 2 (see FIG. 1) was insufficient, resulting in variations in sheet thickness.
On the other hand, in the resin sheet having a sheet thickness of 0.05 mm to 2.2 mm, it was confirmed that the sheet state, the surface state, and the thickness stability were all good.

5). Confirmation of biodegradability Resin sheets (Examples 1 to 6 and Comparative Examples 1 to 4) obtained by extrusion sheet molding according to 2, and a separately prepared PP resin sheet (Comparative Example 5) and PE resin sheet (Comparison) Example 6) and polybutylene succinate resin sheet (Comparative Example 7) were buried in soil, the weight after 12 months of burial was measured, the weight reduction rate was calculated, and the biodegradability of the resin sheet was evaluated with this did. The evaluation results are shown in Table 3.

  As shown in Table 3, all of the resin sheets according to the present invention had a weight reduction rate of 30% or more, and the original sheet was not retained. Note that the PP resin sheet (PP 100 wt%) and the PE resin sheet (PE 100 wt%) prepared for comparison were not decomposed even after one year. On the other hand, it was confirmed that the resin sheet consisting only of the ternary copolymer does not retain the shape of the sheet in one year and is completely decomposed.

Claims (6)

  A ternary copolymer formed by polycondensation of succinic acid derived from a plant, 1,4-butanediol derived from a plant, and lactic acid derived from a plant on 100 parts of a polyolefin resin derived from a plant by weight. A biodegradable synthetic resin sheet made of a plant-derived raw material obtained by adding 10 to 100 parts and heating and kneading the resulting mixture to form a sheet.   The terpolymer is composed of 47 to 49.5 mol% succinic acid, succinic acid and equimolar% 1,4-butanediol, and 1 to 6 mol% lactic acid. The biodegradable synthetic resin sheet according to claim 1.   The biodegradable synthetic resin sheet according to claim 1 or 2, wherein the thickness of the sheet is in the range of 0.05 to 2.2 mm.   The polyolefin-based resin is produced by using glucose obtained by decomposing a plant as a raw material, further converting ethanol obtained by decomposing it into ethylene, and polymerizing the ethylene. The biodegradable synthetic resin sheet according to any one of 1-3.   Glycol obtained by decomposing a plant by a ternary copolymer is used as a raw material, and this is fermented to produce lactic acid and succinic acid, and succinic acid is hydrogenated to 1,4-butanediol. These succinic acids, The biodegradable synthetic resin sheet according to any one of claims 1 to 4, which is obtained by polycondensation of 1,4-butanediol and lactic acid.   A biodegradable synthetic resin container obtained by heating and softening the biodegradable synthetic resin sheet according to any one of claims 1 to 5 to form a container.

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