JP2000080294A - Biodegradable resin composition and foaming by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable resin composition capable of enabling a biodegradable resin to be foamed without using a special chemical foaming agent, and further capable of enabling the resin to be foamed so as to correspond to a low density foam, and to provide a foaming technology by using the composition. SOLUTION: This biodegradable resin composition is obtained by allowing a biodegradable resin 1 to include water 3. The method for foaming the biodegradable resin composition comprises a step for aggressively making the biodegradable resin 1 to include the water 3, and a step for making the water included in the biodegradable resin 1 to be boiled and vaporized by heating the biodegradable resin 1 to a temperature more than the boiling point of the water 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to Japanese Patent Application No. 4-108140 (Japanese Patent Application Laid-Open No. 5-306349), which is a prior application filed by the present applicant.
No.) A biodegradable resin composition which is a part of the invention disclosed in "Method of foaming biodegradable resin" and has recently come into the limelight as "earth-friendly" and "environment-friendly". In particular, the present invention relates to a novel composition and a foaming method capable of achieving such foaming without requiring a special chemical foaming agent.

[0002]

BACKGROUND OF THE INVENTION Synthetic resins are excellent in mass productivity, moldability, and durability, and have undergone technical development and the accompanying increase in consumption at a phenomenal rate this century. However, since the amount of these synthetic resins that have been discarded has become enormous, many synthetic resin products are present in the garbage that floats on the sea or rushes to the shoreline. Various problems have also been raised in incineration plants due to synthetic resin waste. That is, since the synthetic resin has a very strong intermolecular bonding force, it generates high heat during incineration and damages the furnace wall, and the combustion gas contains a large amount of harmful gas. In addition, even if it is bare, it does not rust or decompose with light or ozone, and it has no choice but to wait for it to be scraped off by mechanical energy such as wind, rain, and waves. In particular, high foamed and molded products such as packing cushioning material, heat insulating material, packaging tray, etc.
It required only a volume, and the separation and collection was not worth the cost, and it was noticeable and troublesome on the sea and on the coastline because it was white.

[0003] Under such circumstances, recycling campaigns have been carried out, and degradable resins have been put on the market. For degradable resins, technological development has been remarkable and consumption has gradually increased. There is a tendency. However, degradable resin, from the relationship between the softening or melting point and the foaming temperature of the foaming agent,
It is very difficult to achieve high foaming with a conventional chemical foaming agent, and there is now a need for a technique for highly foaming biodegradable resins.

In order to meet such technical requirements, the present applicant has already filed Japanese Patent Application No. 4-108140 (Japanese Unexamined Patent Application Publication No. 5-108140).
No. 306349) Although this technology is disclosed as "a method for foaming a biodegradable resin", the usefulness of the material as a "biodegradable resin composition" was particularly evaluated, and this prior application was divided. And "Biodegradable resin composition and foaming method using the same".

[0005]

SUMMARY OF THE INVENTION The present invention relates to a biodegradable resin composition which can cope with high foaming without having a special chemical foaming agent and which can be foamed. It is intended to provide an improved foaming technology.

[0006]

That is, the biodegradable resin composition according to claim 1 is characterized in that the biodegradable resin is made to contain water. In addition, the biodegradable resin composition according to claim 2 is characterized in that, in addition to the requirements described in claim 1, the water is positively added to the biodegradable resin, so that the water is more than the equilibrium moisture value of the biodegradable resin. It is characterized by being contained. Claim 3
The biodegradable resin composition according to the present invention is characterized in that the biodegradable resin is a cellulose ester compound in addition to the requirements described in claim 1 or 2.
Furthermore, the biodegradable resin composition according to claim 4 is characterized in that, in addition to the requirements described in claim 1, 2, or 3, the biodegradable resin has a starting state in a pellet form. is there. Furthermore, the method for foaming a biodegradable resin composition according to claim 5 includes a step of positively containing water in the biodegradable resin, and heating the biodegradable resin to a temperature higher than the boiling point of water. Boil-vaporizing water in the biodegradable resin. Furthermore, the method for foaming a biodegradable resin composition according to claim 6 is characterized in that the biodegradable resin is an ester compound of cellulose in addition to the requirements described in claim 5. Furthermore, in the foaming method for a biodegradable resin composition according to claim 7, the foamed biodegradable resin obtained by the foaming may be used as a cushioning material for packing, in addition to the requirements described in claim 5 or 6. It is characterized by being used.

In the present invention, when the water-containing water content of the biodegradable resin is exposed to a high-temperature atmosphere, it receives surrounding heat and evaporates. On the other hand, since the biodegradable resin is softened or melted by the surrounding high temperature atmosphere, the biodegradable resin expands, that is, foams due to the vapor pressure of boiling and vaporizing inside. By adjusting the water content and the temperature of the surrounding high temperature atmosphere at this time, the degree of softening or melting of the biodegradable resin and the timing of vaporization and water vapor pressure of the water content were changed, and the degree of foaming was also different. Become something. If this is performed in a continuous porous mold, the outermost shape of the foam is regulated at the time of foaming, so that a desired cavity shape is formed in the mold.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a biodegradable resin as a constituent element of the present invention will be described, and then a foaming method using the same will be specifically described. The biodegradable resin in the present invention means a resin material whose physical properties are deteriorated based on a biological action, which includes a type in which the resin itself is completely degraded, and a resin which is hardly decomposed and imparts disintegrability. There is a type that did. The former type includes microbial products, natural polymer-based products, and products derived from petroleum-based raw materials.The latter type includes blends with starch and blends with aliphatic polyesters. is there. These biodegradation mechanisms include various aspects such as degradation by enzymes such as lipase, amylase, cellulase, and protease; degradation by microorganisms in activated sludge; and degradation by soil in natural environments such as forests and cultivated lands. More specifically, polyhydroxybutyric acid and its derivatives, pullulan, cellulose-chitosan mixture, esterified products of cellulose, amylose and wood flour, polyester-nylon copolymer, polyester copolymer, blend of starch and polyethylene Examples include body, polyvinyl alcohol, polyether, polyurethane, polyamide and the like. These generally have a low melting point and are accelerated in the presence of water. The oil 5, which is an example of a high-temperature atmosphere heated above the boiling point of water, may be various oils such as animal oils, vegetable oils, mineral oils, and synthetic oils, but has high safety and low viscosity. Those which can be easily separated and recovered later are suitable.

In this embodiment, pellets of Mater-Bi "Mataby" (registered trademark) sold by Nippon Synthetic Chemical Industry Co., Ltd. are used as the biodegradable resin.
A commercially available edible salad oil was used. Here, Mater-Bi as a biodegradable resin is involved in the development of NOVAMONT, a company belonging to the Montedison group of Italy, and a purified substance from a plant and a synthetic polymer penetrate into each other at the molecular level, It is a thermoplastic biodegradable polymer formed by hydrogen bonding. Further, its melting point is about 140 ° C., and it is said that it absorbs water and swells to promote biodegradation, and exhibits biodegradability equivalent to that of paper in an environment where microorganisms can survive.

[0010] The biodegradable resin composition according to the present invention is provided by providing a water-containing step of positively immersing water in the biodegradable resin as described above for foaming. Specifically, as shown in FIG. 1, a sufficient amount of water 3 was poured into a container 2, and the pellet-like biodegradable resin 1 was immersed in the water 2 for 10 hours. Although not shown, after this, the hydrated biodegradable resin 1 was taken out and spread on water-absorbing paper to remove water droplets adhering to the surface.
In addition, this water-containing step may be immersed in hot or moderately heated water or left in a high-humidity atmosphere for a long time. By providing such a water-containing step, it is possible to contain more water than the equilibrium moisture in the atmosphere, so that it is possible to achieve a higher foaming.
Further, according to the well-calculated and controlled water-containing step, it is easy to obtain a biodegradable resin which is uniformly foamed with a uniform water content in the skin layer and the core. Of course, if the equilibrium moisture is necessary and sufficient for the required expansion ratio, there is no need to set up a process that is apparently a water-containing step, and the biodegradable resin that has been left in the atmosphere to contain the equilibrium moisture is left as it is. May be used. Also, in this case, it seems that the water-containing step does not seem to be provided, but it depends on the humidity condition in the atmosphere, the temperature condition, the ventilation condition, etc. When a variety of conditions are met and sufficient equilibrium moisture can be obtained, measures are taken to leave the biodegradable resin for water addition. This step is essentially a so-called active water-containing step. It is what becomes.

A process of placing the device in a high-temperature atmosphere following the water-containing process will be described. The biodegradable resin composition of the present invention comes into contact with a high-temperature oil 5 which is an example of an atmosphere heated to a temperature higher than the boiling point of water. In this embodiment, the normal temperature,
At atmospheric pressure of humidity, salad oil, which is an example of oil 5 filled in pan 4 as shown in FIG.
Heating was performed at about 30 to 180 ° C., and the water-containing biodegradable resin 1 obtained through the water-containing step was dispersed and dropped in the salad oil in the form of pellets.

[0012] The biodegradable resin 1 containing water is heated oil 5
When the biodegradable resin 1 is immersed, a large amount of heat of the oil 5 is transmitted to the biodegradable resin 1 from its surface, and the water-containing moisture is heated almost simultaneously with the biodegradable resin 1 itself, and the temperature rises rapidly. . Since the temperature rise reaches the boiling point of water or more, the water-containing water vaporizes in the biodegradable resin 1 by boiling. Since the biodegradable resin 1 has also reached the softening temperature or the melting point at the same time, the biodegradable resin 1 itself expands and foams due to the steam pressure that has been vaporized inside. This action is carried out sequentially from the skin layer, and in the case of small grains, the whole is performed almost instantaneously and almost instantaneously, but in the case of relatively large grains, the action is successively performed from the skin layer toward the core. The action is performed continuously, and soon the whole is almost uniformly expanded and foamed. Note that the biodegradable resins 1 adjacent to each other in the initial stage of the oil 5 immersion may be obtained as a cluster mass which is fused and foamed with each other. Use

In this embodiment, the temperature of the oil 5 is set to 160
When the temperature is raised to about 180 ° C., foaming can be performed with a foaming ratio of about 8 to 10 times, which is much higher than the foaming ratio of about 2 times obtained by adding a few percent of a commercially available chemical blowing agent. It could be foamed. The foamed biodegradable resin thus obtained is then centrifuged or washed,
By performing drying or the like, the adhered oil is separated and collected, and can be used as a foam for buffering or the like. That is, foams such as conventional styrofoam were used as a cushioning material or a filler when packing set goods, glass products, precision equipment, high-quality fruits, etc., or laminated with a separate plate material as a heat insulating material. It can be used for various applications. The oil separated and recovered may be used as the oil for the next process. When the temperature of the oil 5 in this step is low, the temperature of the oil 5 is relatively low because the biodegradable resin softens or melts slowly, and the steam pressure due to boiling vaporization is not used at once. Then, the vaporized steam is released at a stroke, so that a relatively highly foamed product can be obtained.

In the above embodiment, the foamed biodegradable resin is generally obtained as an independent mass of each granule. To further process this into a product such as a tray, In order to shape the biodegradable resin into a shape, it is necessary to separately apply heat and pressure. Next, an embodiment of a method for foaming a biodegradable resin also serving as the shaping step will be described. That is, in FIG. 3, the biodegradable resin composition of the present invention, which is in the form of pellets as an example of water hydrated through the hydration step, has an appropriate amount determined in consideration of a predetermined expansion ratio. Placed inside. The molding die 7 is formed by integrating upper and lower split dies 7a and 7b with bolts of their flanges 71, 71, and forms a cubic cavity 8 therein in this embodiment. Is. Although not shown in the drawing, the molding die 7 is not made of a solid metal material, but is made of a porous material having a large number of network-like holes communicating between the inside and the outside almost entirely. As this porous material, in addition to foamed metal, a filler formed capable of forming voids is added, and a sintered product such as a metal or ceramic formed by sintering, and further, a wire mesh, a punching metal, etc. are press-formed. And various forms such as those formed by laminating them.

In this embodiment, the biodegradable resin 1 is placed in the continuous porous mold 7 and then immersed in the oil 5 together with the mold 7 as in the above embodiment. As a result, the oil 5 heated above the boiling point of water heats the mold 7 and reaches the cavity 8 from the hole of the mold 7 and fills the cavity 8 to fill the cavity 8. The biodegradable resin 1 placed inside is heated together with water-containing moisture. The heated biodegradable resin 1 swells and foams due to the water vapor pressure since the water-containing moisture evaporates and evaporates and the biodegradable resin 1 itself softens or melts in the same manner as in the above embodiment. However, in this embodiment, since the periphery is limited to the cavity 8 in the molding die 7, foaming cannot be expanded freely, and the foamed lump interferes with each other, partially fuses, and the The parts are foamed while deforming so as to fill each other's space, and eventually have an overall shape that uniformly fills the cavity 8 of the mold 7. At this time, if the pores of the continuous porous mold 7 are relatively large, the contact between the biodegradable resin and the oil 5 is good, and foaming is easily performed. After finishing, the unevenness due to the holes tends to increase. In such a case, the surface can then be smoothed simply by pressing or heating and pressing with a solid and solid finishing mold. Conversely, when the hole is relatively small, a smooth one is easily obtained, but the exchange of the oil 5 into the cavity 8 of the mold 7 tends to be insufficient, and it is difficult to adjust the foaming. . At this time, it is also possible to take measures by sealing the pot 4 and then reducing the pressure inside.

Then, the molding die 7 is raised from the oil 5 and the molding die 7 is separated into upper and lower parts to take out a foamed mass.
Thereafter, if post-treatments such as separation and recovery, washing, and drying of the oil 5 are performed in the same manner as in the above embodiment, a biodegradable resin body shaped and foamed into the shape of the cavity 8 in the mold 7 is obtained. . Since the shaped and foamed biodegradable resin bodies enter each other intricately and are integrated, the entire shape is sufficiently maintained unless a special heavy load is applied. Used as a support buffer.
In order to be able to withstand heavy loads, it is preferable to add an adhesive component and the like in order to bond between the foamed structures, and then to strengthen the adhesive component. Also, a biodegradable resin is used for the adhesive component. Is preferred.

Therefore, according to the above embodiment, the biodegradable resin can be relatively easily foamed at a relatively high level, and is advantageously provided as a substitute for a particularly high foamed material which has recently been regarded as a problem. can do. Also, since no special chemical blowing agent is required, the manufacturing method itself is naturally gentle.
In the above embodiment, the biodegradable resin is made of Mater.
-Bi "Mataby" (registered trademark) was used, but other biodegradable resins can be applied. In particular, in the embodiment that also serves as a shaping step, it is not necessarily required to be in the form of a pellet, but in the form of a sheet, fibrous, or appropriately shaped,
Applicable. The oil 5 is not limited to salad oil, and other oils can be applied. Further, depending on the case, the heated oil 5 may be applied even when the heated oil 5 does not come into contact with the biodegradable resin in a gaseous and full atmosphere, instead of coming into contact with the biodegradable resin. In addition, the addition of water to the biodegradable resin by the water-containing step is indispensable, but processing steps such as centrifugation, washing, and drying in the foaming step are not necessarily required.
This is a process that can be added as appropriate.

[0018]

According to the present invention, a biodegradable resin composition which can cope with high foaming without requiring a special foaming agent and a foaming technique using the same can be obtained. It can be provided as a substitute for the conventional foam, and can now contribute to alleviating the garbage pollution which is an important issue.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state of a water-containing step as a pretreatment step in an embodiment of a method for foaming a biodegradable resin of the present invention.

FIG. 2 is a perspective view showing a state of a process in an embodiment of a method for foaming a biodegradable resin of the present invention.

FIG. 3 is a perspective view including a partial cross section of a continuous porous mold used in another embodiment of the method for foaming a biodegradable resin of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Biodegradable resin 2 Container 3 Water 4 Pot 5 Oil 6 Gas range 7 Mold 7a Split mold (above mold) 7b Split mold (below mold) 8 Cavity 71 Flange

Claims (7)

[Claims] 1. A biodegradable resin composition comprising water and a biodegradable resin. 2. The biodegradable resin composition according to claim 1, wherein the water is positively added to the biodegradable resin and is contained in the biodegradable resin at an equilibrium moisture value or more. object. 3. The biodegradable resin composition according to claim 1, wherein the biodegradable resin is an ester compound of cellulose. 4. The biodegradable resin composition according to claim 1, wherein the initial state of the biodegradable resin is a pellet. 5. A step of positively containing water in the biodegradable resin, and heating the biodegradable resin to a temperature equal to or higher than the boiling point of water.
Boil-vaporizing the water content in the biodegradable resin. 6. The method for foaming a biodegradable resin composition according to claim 5, wherein said biodegradable resin is an ester compound of cellulose. 7. The method for foaming a biodegradable resin composition according to claim 5, wherein the foamed biodegradable resin obtained by the foaming is used as a cushioning material for packing.