JP2018087354A - Biodegradable resin composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable resin composition which maintains high biodegradability and high mechanical strength, and achieves commercialization with adding price competitiveness with oil based synthetic resins by cost reduction.SOLUTION: A biodegradable resin composition is formed of a vegetable material (A), a binding agent (B) and a polylactic acid (C), where a content of the vegetable material (A) is 95-51 mass%, a content of the binding material (B) is 17-2 mass% and a content of the polylactic acid (C) is 35-3 mass% (total of (A) to (C) is 100 mass%), the content of the binding agent (B) is less than the content of the polylactic acid (C), the binding agent (B) is formed of one or more combinations of casein, soybean protein, gluten, devil's tongue yam powder, starch, dry starch, corn starch and tapioca, and the vegetable material (A) is a flake.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biodegradable composition used as a raw material for a molded article or the like that retains high biodegradability, suppresses an increase in price, and has a high mechanical strength comparable to petroleum synthetic resin. It relates to the manufacturing method.

In the modern society, a large variety of molded products or molded products made of synthetic resin are used in a wide range of fields. However, most of these molded products are made of synthetic resin made from petroleum. When they are no longer needed and disposed of, for example, when buried in the ground, they remain almost semi-permanent. in will remain in the ground, and as such when incinerating hazardous substances and CO _2, such as dioxins occur, they induce problems such as adverse effects on the environmental destruction or human body. Therefore, in recent years, biodegradable resins that can be decomposed in the natural environment have been proposed as one of the measures for solving such problems, and some of them have been put into practical use.

  For example, Patent Document 1 (Japanese Patent No. 3793783) discloses a bamboo powder plastic-like molded body formed by using bamboo from various plant fiber materials and molding the bamboo into a powder, and a method for manufacturing the same. Proposed. This manufacturing method includes the following steps (a) to (b). That is, (a) a preparation step of preparing bamboo powder having a water content of 20% by weight or less and a particle size of 10 mesh pass or less or 400 mesh pass or more, (b) filling the bamboo powder in a predetermined mold, A molding step of pressing at a heating temperature of 80 ° C. to 200 ° C. and a pressure of 20 MPa or more, and (c) a cooling step of cooling and solidifying in the molding die to obtain a molded body.

  According to this technology, it is possible to produce a plastic-like molded body using only bamboo powder without using an adhesive, etc., and a plastic-like molded body at a sufficiently low temperature and low pressure compared to a molded body using conventional wood powder. It is said that can be obtained.

Patent Document 2 (Patent No. 4149987) proposes a composite biodegradable molded product produced using a small amount of biodegradable resin and a large amount of plant-based granular material. This molded article is composed of 60 to 90% by weight of plant-based material and 40 to 10% by weight of hydroxycarboxylic acid resin (total of both is 100% by weight). The hydroxycarboxylic acid resin is composed of polylactic acid and polycaprolactone. The weight ratio of these polylactic acid / polycaprolactone is set in the range of 5/95 to 95/5.
According to this technology, a small amount of biodegradable resin is used for a large amount of plant-based granule, and it is excellent in mechanical properties and moisture resistance. When used in air, mechanical properties and moisture resistance are excellent. It is said that it is excellent in biodegradability, that is, it is possible to obtain a molded product that decomposes or collapses when left in soil.

  However, the molded articles (articles) described in Patent Documents 1 and 2 are all small in particle size, that is, manufactured using fine powder, and various problems are latent in these. For example, the molded body described in Patent Document 1 uses bamboo powder having a moisture content of 20% by weight or less and 10 mesh path or less or 400 mesh path or more, and the molding described in Patent Document 2 The product is obtained by using plant material such as wood powder or bamboo powder having a particle size of 20 mesh or less, preferably 50 mesh or less, more preferably 100 mesh or less.

  However, in order to pulverize the particle size of these bamboo powder and wood powder until the above mesh pass or mesh value is obtained, their production is difficult and troublesome. When used, it is limited to the use of bamboo itself, branches, stems and leaves cannot be used. In addition, it is extremely difficult to handle these fine powders, and depending on how they are handled, there is a risk of inadvertent accidents. On the other hand, there are many problems such as causing high costs. That is, in order to produce the fine powder as described above, a high-precision pulverizer is required, and the processing time required for the pulverization is increased. Therefore, it is essential to dry these materials, and usually the fine powder as described above cannot be produced unless it is dried below a predetermined water content. In the bamboo powder preparation process of Patent Document 1, the moisture content must be 20% by weight or less, so the moisture content of raw bamboo is usually about twice that, and this amount of moisture is reduced to half or less. Therefore, a drying apparatus and a drying process for that purpose are necessary, and considerable equipment costs and processing costs are required. In addition, similar problems exist in the manufacture of the molded article of Patent Document 2.

  In addition, the handling of fine powders as described above requires high-temperature treatment, so that water vapor tends to stay inside during molding, and so-called puncture (breakage) occurs, which sometimes causes unexpected accidents. In addition, there are many cases where molding defects are caused. As a result, it is extremely difficult to actually manufacture and handle such fine powder as described above, and it is extremely difficult to manufacture a molded body (article) using such a fine powder. The cause of this puncture has not been clarified yet, but when the powder having a predetermined water content is compacted and molded under heat and pressure, the water vapor generated inside is compressed and formed inside the molded body under pressure. This may be due to stagnation, which may be caused by a small explosion due to heating and exposure to the molding surface, or by generating an internal thermal decomposition product.

  Therefore, the compacts (articles) of Patent Documents 1 and 2 both require a high-accuracy pulverizer and a drying device, which increases the equipment costs and the like, leading to high costs for the compacts (articles). Become. In addition, since the danger exists in the handling of the fine powder when manufacturing these molded objects (articles), measures for that are also indispensable.

  In addition, Patent Document 2 uses polylactic acid, but it is difficult to directly bond the polylactic acid and the plant material, and the affinity or familiarity between them tends to be insufficient. In the solidified state, it is difficult to obtain a desired mechanical strength due to insufficient bonding force. On the other hand, this polylactic acid is extremely slow to crystallize and is almost in an amorphous state under normal molding conditions, and there is a problem that the shape becomes difficult to maintain at a glass transition temperature of 60 ° C. or higher.

Japanese Patent No. 3793783 Japanese Patent No. 4149887

  From the above, the compacts (articles) of Patent Documents 1 and 2 both require a high-precision crusher and a drying device for production, resulting in high equipment costs and processing costs. As a result, the price competitiveness with conventional molded articles (articles) made of synthetic resin made of petroleum has been lost, and until practical use of such molded articles (articles) is still in widespread use. It has not reached.

  Therefore, the inventor of the present invention, among these problems, firstly, the increase in cost is achieved by using flakes having a particle size larger than that of the conventional powder and classified into a different category. This eliminates the need for a pulverizer and dryer, eliminates the risk of handling fine powders, and even with such flakes, the use of a binder ensures a strong bond with polylactic acid. As a result, the inventors have found that the desired mechanical strength can be obtained, and that the problems of polylactic acid can be solved by setting the content to a predetermined amount, thereby completing the present invention.

  Therefore, an object of the present invention is to maintain high biodegradability, have high mechanical strength comparable to that of petroleum synthetic resins, and further reduce cost, An object is to provide a biodegradable resin composition that has been commercialized with price competitiveness, a method for producing the resin composition, and a molded product.

  The present invention can be achieved by the following configurations. That is, the biodegradable resin composition according to the first aspect of the present invention is a biodegradable resin composition comprising a plant material (A), a binder (B), and polylactic acid (C). The content of the plant material (A) is 95 to 51% by mass, the content of the binder (B) is 17 to 2% by mass, and the content of the polylactic acid (C) is 35 to 3% by mass ( The total of these (A) to (C) is 100% by mass), and the content of the binder (B) is less than the content of the polylactic acid (C), and the binder (B) is , Casein, soy protein, gluten, konjac potato powder, starch, dry starch, corn starch, or a combination of two or more of tapioca, and the plant material (A) is made of flakes And

  Furthermore, the manufacturing method of the biodegradable resin composition in the second aspect includes a material preparation step for crushing the plant material (A) to make flakes, and the plant material 95 to 51 made into the flakes (A). In the binder mixing step of mixing 17 to 2% by mass of binder (B) with mass%, and in the mixture mixed in the binder mixing step, polylactic acid (C) is in the range of 35 to 3% by mass, A polylactic acid kneading step of mixing and kneading the amount of the binder (B) less than the content (the total of these (A) to (C) is 100% by mass), and a biodegradable resin composition A manufacturing method, wherein the binder (B) is composed of one or a combination of casein, soy protein, gluten, konjac potato powder, starch, dry starch, corn starch, tapioca. Features.

  According to the biodegradable resin composition of the first aspect, high biodegradability is maintained, cost increase is suppressed, cost reduction is achieved, and mechanical strength is comparable to that of petroleum synthetic resin. The biodegradable composition used as the raw material of the molded object which has can be provided. Specifically, a plant-based material (A) by applying one or a combination of two or more of casein, soy protein, gluten, konjac potato powder, starch, dry starch, corn starch and tapioca as the binder (B). ) Can be increased, and the bond with polylactic acid (C) becomes firm, resulting in high mechanical strength comparable to that of petroleum synthetic resin. It can be solved by setting it to a predetermined amount. And what is particularly characteristic is that the cost can be reduced and the price competitiveness with the synthetic resin made of petroleum can be obtained, so that it can be used in a wider range of fields.

  Moreover, according to the biodegradable composition of the first aspect, it is possible to solve the problems that occur when the powder of the prior art is used, and to improve the design. In addition, casein, soy protein, gluten, konjac potato powder, starch, dry starch, corn starch, and tapioca as binders are familiar and can be obtained easily and inexpensively, making them more biodegradable resin compositions. Cost reduction of goods can be realized.

  Furthermore, according to the method for producing the biodegradable resin composition of the second aspect, high biodegradability is maintained, cost increase is suppressed and cost reduction is realized, and further, comparable to petroleum synthetic resin. A biodegradable composition as a raw material for a molded article having high mechanical strength can be produced. In particular, the cost reduction can counter the price competitiveness with conventional synthetic resins, and this resin composition can be used in a wide range of fields.

  Specifically, a plant material is obtained by using one or a combination of two or more of casein, soy protein, gluten, konjac potato powder, starch, dry starch, corn starch and tapioca as the binder (B). The amount of (A) can be increased, and the bond with polylactic acid (C) becomes firm, and a high mechanical strength comparable to petroleum synthetic resin can be obtained. In addition, since this binder (B) is made smaller than the amount of polylactic acid (C), the amount of polylactic acid is not reduced, and its properties are not impaired. That is, the problem of polylactic acid can be solved by setting this amount to a predetermined amount. And, what is particularly characteristic is that cost reduction can be realized and price competitiveness with petroleum synthetic resin can be achieved, so that a wide variety of molded products or molded products can be manufactured. It is possible.

It is a block diagram which shows the manufacturing process of the manufacturing method of the biodegradable resin composition which concerns on this invention. It is a schematic plan view of the kneader used in the examples and comparative examples of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment shown below exemplifies a biodegradable resin composition for embodying the technical idea of the present invention, and does not specify the present invention. It is equally applicable to the other embodiments included.

With reference to FIG. 1, the manufacturing method of the biodegradable resin composition which concerns on embodiment of this invention is demonstrated.
The manufacturing method of the biodegradable resin composition which concerns on embodiment of this invention includes the following processes.
Material preparation step 1 for preparing flakes of a predetermined size made of plant material (A)
Binder mixing step 2, in which a predetermined amount of binder (B) is mixed with a predetermined amount of flakes
Polylactic acid that is kneaded by mixing polylactic acid (C) into the mixture in a predetermined amount range and containing less than the amount of binder (B) (the total of these (A) to (C) is 100% by mass) Kneading process 3,
A composition molding step 4 for molding a material having an arbitrary shape from the kneaded product, and a molded product production step 5 for producing various molded products using the composition molded in the step.

  Hereinafter, each process will be described in detail.

Oh, preparation process 1 of plant material (A)
The plant material (A) is not particularly limited, but is wood, bamboo, rice husk, hemp or the like. Hereinafter, an example using bamboo will be described. In particular, the use of bamboo has the following advantages.
Bamboo has traditionally been widely used for building materials, vegetable cultivation materials, clothespins, fishing rods, and other materials. However, in recent years, these have been replaced by synthetic resins, and their demand has decreased significantly. , Bamboo continues to grow because of its strong vitality and fertility, and the satoyama has turned into bamboo, hindering the growth of other plants and causing environmental degradation. In addition, the propagation of this bamboo causes a natural disaster such as a landslide due to heavy rain, because the bamboo roots stretch over the shallow surface and do not penetrate deep into the ground. Under these circumstances, finding out the use of bamboo can solve the above problems and has great social significance. In addition, when bamboo is used, the mechanical strength (static strength and impact strength) is excellent and the amount of lignin is small compared to wood, etc. (if this amount is large, it adheres to the kneader and the equipment maintenance is troublesome). Therefore, it is possible to obtain a high-strength molded product by reducing the labor required for equipment maintenance.

  The embodiment of the present invention uses bamboo having the above-mentioned advantages, but this bamboo is not limited to the type of bamboo, and all types of bamboo can be used. These bamboos include the whole bamboo, that is, underground stems, stems, branches, and leaves (hereinafter collectively referred to as bamboo materials), and one or more of these are used in combination. In addition to this bamboo, it may be firewood, or a mixture of this firewood and bamboo.

This bamboo material is made into flakes by crushing or the like. In other words, when bamboo is crushed, it breaks into large pieces or thin pieces, which are roughly similar to cubes, rectangular parallelepipeds, polygonal cylinders, polygonal pyramids, etc. Also called flake. ]. These flakes can be used as they are, but if the size is large, the fluidity will deteriorate during the production or molding of the composition and it will not be uniformly dispersed, and it will not be sufficiently mixed or kneaded with other materials as desired. On the other hand, it becomes difficult to obtain a molded body, etc. On the other hand, if the size is reduced, it is close to the powder particle size of the prior art and the problems of the prior art may become obvious, so it cannot be too small.
Therefore, it is preferable to use flakes having a size of 2 to 5 mm on one side and 5 mm or less on the other side. Moreover, it is preferable that the flakes of this size are within a predetermined amount and exceed 50% by mass. When these flake sizes are expressed in JIS standard mesh (number of meshes / inch), 2 to 5 mm is in the range of 8.60 mesh (2000 μm) to 3.85 mesh (5000 μm).

  The flakes are made by crushing bamboo using a crusher. Since this crushing is possible by rough crushing if the size is as described above, a high-precision crusher as in the prior art becomes unnecessary. This can reduce equipment costs and processing costs. In addition, it is better to roughly crush by putting the whole into a crusher without separating the type and part of the bamboo. That is, the whole bamboo, that is, the underground stem, stem, branch, leaf, etc. are crushed together. According to this crushing, the flakes of the above size are 2 mm or less, that is, powder is also generated. However, this powder is not discarded, but is mixed with the above-mentioned size flakes if it is a predetermined small amount. By this mixing, gaps between large-sized flakes can be filled, and at the time of formation, the gaps in the mold can be entered, and the design of the molded product can be improved. Such powder is generated when the bamboo is crushed, and is also generated in the subsequent binder mixing step 2 and polylactic acid kneading step 3 even if individual flakes rub against each other.

  However, as the amount of such powder increases, the problems of the powders of the prior art may occur, so the ratio of flakes and powders of the above size increases the flakes while reducing the powders. In the final step, the ratio is such that the flake exceeds 50% by mass and less than 80% by mass, and the powder has a mass of 50% or less. Most preferred is 80 wt% flakes and 20 wt% powder. With these ratios, the problems of the prior art can be avoided even with the former ratio, and no problem occurs with the latter ratio. In addition, flakes of 5 mm or more may be used if they are in a small amount. In addition, these bamboo materials may be used without being dried, and when this bamboo is used, each process, that is, material preparation process 1, binder mixing process 2 and polylactic acid kneading process. 3 is dried by frictional heat.

  Therefore, in this material preparation step 1, it is not necessary to install a drying device. Of course, the dried material is not excluded from the material, and if a drying material is used, the processing time in each process can be shortened. The flakes of the above size are selected with a sieve, and those that do not pass through the sieve are put into a crusher again and crushed.

Step 2 for mixing binder (B)
In this mixing step 2, a predetermined amount of a mixture is mixed with a predetermined amount of flakes prepared in the previous step. The flakes are in the range of 95 to 51% by mass, and this is 17% by mass or less (however, the lower limit is 2% by mass, this amount is within the mass% of the above range and the mass% of polylactic acid described later is Mix the binder in an amount not exceeding. That is, if the amount of this mixture increases, the fluidity deteriorates and the productivity decreases, so the amount of polylactic acid should not be exceeded.

  As the binder, vegetable proteins such as casein, soy protein, gluten, konjac potato powder, starch, lignin, matsuyani, tannin, dry starch, corn starch, tabioca and the like are effective. These are all familiar and can be obtained easily and cheaply.

This binder is mixed with stirring using a mixer. This mixing may be performed while further crushing the flakes in a crusher. In this mixing step 2, temperature management is important. That is, during mixing / crushing, the individual flakes rub against each other to generate heat, and this heat reduces moisture, while the adsorbed gas is released to raise the temperature of the flakes. At this time, if the temperature rises to a high temperature, the flakes are burnt and the quality is deteriorated. If the temperature is too low, the bonding force is reduced due to insufficient release of moisture and adsorbed gas. Therefore, the crushing tank of the crusher should have a jacket made of oil. An appropriate temperature increase range is 140 to 220 ° C, preferably 150 to 180 ° C.
On the other hand, moisture adjustment is also necessary. This mixture is agitated / crushed until a predetermined amount of water is obtained. The water content after the stirring / crushing treatment is 7% or less, desirably 5% or less. Bamboo wood just after cutting has a lot of moisture, so adjust the moisture by extending the crushing time. In this mixing step 2, the binder adheres to the crushed surface of the flakes in a powdered or molten state. By mixing this binder, in the next step, the binding force between flakes and polylactic acid can be increased and uneven distribution can be suppressed.

  Specifically, the mixing of the binder makes it possible to increase the mixing ratio of flakes and to sufficiently extract the high strength of bamboo. In other words, since bamboo is denser and superior in mechanical strength than wood and the like, the resin composition of flakes should have this characteristic. However, this flake is difficult to disperse evenly, and a partial distribution difference, that is, uneven distribution occurs, resulting in destruction of the molded body and the like, and the high strength characteristics of bamboo cannot be fully utilized. Further, when the mixing ratio of this bamboo is increased, uneven distribution becomes more prominent, and even pellets cannot be obtained normally, or even if they are obtained, they are easily crushed, but these can be eliminated. In particular, the application of the binder (B) makes it possible to increase the amount of the plant-based material (A) and to firmly bind the polylactic acid, so that a mechanical strength comparable to that of a petroleum synthetic resin can be obtained. , This makes it possible to use in a wider range of fields with price competitiveness with petroleum synthetic resin.

C. Polylactic acid kneading process 3
In this polylactic acid kneading step 3, 35% by mass or less (however, the lower limit is 3% by mass and the amount is within this range and exceeds the mass% of the binder) is added to the mixture produced in the previous step. Knead. Polylactic acid (C) is one of the bioplastics synthesized from plant-derived materials. It is hydrolyzed by water in the environment to be reduced in molecular weight, and finally decomposed into carbon dioxide and water by microorganisms. This polylactic acid is finally decomposed into carbon dioxide by microorganisms and released into the atmosphere. However, since plants absorb starch in the atmosphere and synthesize starch, There is no increase in the amount of carbon dioxide that is the cause of chemical conversion. This property is generally referred to as “carbon neutral”. However, on the other hand, this polylactic acid has a problem that it is very slow to crystallize and is almost in an amorphous state under normal molding conditions, and softens so that it is difficult to maintain its shape at a glass transition temperature of 60 ° C. or higher.

  Polylactic acid having such characteristics is added to the mixture and kneaded. The kneaded material is preferably repeatedly spread many times between a pair of rolls that rotate in close proximity to each other in parallel. Specifically, the kneaded material is expanded by repeating high-pressure pressurization with strong viscous flow at the roll inlet and a pressure release cycle at the roll outlet many times. As a result, moisture and other adsorbed gases are released from the fracture surface of the flakes, this gas is transferred and diffused into polylactic acid, and the surface is purified, thereby improving the affinity and familiarity with polylactic acid and binders. Strengthening the bonding strength between polylactic acid and flakes is achieved, and furthermore, the kneaded product is spread into a thin film between rolls that have been approached many times, thereby suppressing the occurrence of uneven distribution. In addition, viscosity unevenness caused by a temperature difference between the polylactic acid and the mixture, that is, the high-viscosity part and the low-viscosity part are spread to an equal thickness, and the occurrence of uneven distribution is suppressed. The kneaded material is in a state of being pressed thinly between the rolls, and is in a state similar to rolling metal, etc., but the roll exit side remains attached to the roll surface and reaches the inlet side again due to the rotation of the roll. The term was improper and unfolding. By this kneading method, even when the mixing ratio of flakes is increased, the occurrence of uneven distribution can be suppressed and a high-strength molded body such as pellets can be obtained.

  Moreover, the problem which polylactic acid has can be suppressed by increasing the amount of flakes. That is, when the flake content exceeds 50% by mass, the average distance between the flakes is reduced, and the decrease in shape retention ability such as viscous deformation or flow and sagging due to the low heat resistance of polylactic acid is suppressed. In addition, since the amount of polylactic acid component is relatively small, the heat resistance problem of polylactic acid is limited.

D. Addition of colorant This biodegradable resin composition made of bamboo becomes reddish brown and changes over time depending on the flake conditions and mixing ratio. In order to avoid this, pigments of various colors such as inorganic and organic colors can be mixed as the colorant, and if necessary, the paint can be colored with a paint kneaded with the color extender. Further, the flakes can be dyed before kneading with polylactic acid or the like, preferably at a stage after coarse crushing. Various function improvers such as foaming agent and rubber powder can be added in addition to the colorant. When these additives are mixed, the mixture of polylactic acid, binder and bamboo is used as a kneading process after the addition. It is good.

Composition composition process 4
The kneaded product generated in the previous step 3 is formed into an arbitrary shape, for example, a pellet molded product, using a molding machine. In this step, a molded product may be directly produced. These molded articles and molded articles are composed of 95 to 51% by mass of flakes (A), 17 to 2% by mass of binder (B) and 35 to 3% by mass of polylactic acid (C) (of these (A) to (C). The total is 100% by mass), the main component is flakes having 2 to 5 mm on one side and 5 mm or less on the other side, and the mass% of the binder (B) is less than the mass% of polylactic acid (C). Become.

Molded product production process 5
In this step 5, the molded product (pellet) produced in the previous step 4 is used, and using a molding machine such as an extrusion molding machine or an injection molding machine, an arbitrary molded product such as a furniture material, a building material, or an automobile. , Interior materials such as home appliances, information and communication equipment, further exterior materials, housing materials, and also agricultural / fishery / horticultural supplies such as flower pots, fences, baskets, nursery pots, golf tees, floats, outdoor chairs, etc. We make leisure items such as tables, and disposable items such as films, sheets, and trays. In addition, the equipment to be used does not require any special equipment, and can be handled by a conventional extrusion molding machine, injection molding machine, etc., and the mold used can also be handled by a conventional mold for synthetic resin.

(Examples and Comparative Examples)
Examples of the present invention will be described below in comparison with comparative examples. In this embodiment, the flake is made of only bamboo material and a mixture of this bamboo material and straw material.
Table 1 shows the blending ratio (mass%) of each raw material of Examples 1 to 14 and Comparative Examples 21 to 23 and the moldability of the pellets. However, the mixing ratio of bamboo and straw is a value that assumes that the water content is reduced to 5%. Marugoto means that all the leaves and stems are made of bamboo, and that all the underground stems, stems, branches and leaves are roughly crushed (bamboo is mixed with 5% of the whole).

In both Examples and Comparative Examples, the moisture ratio of flakes (size: about 2 to 3 mm) was measured, and the amount when the moisture was assumed to be 5% was added to the crushing / mixer device together with the binder. The crushing / mixing apparatus used has two stages of high-speed rotating blades at the bottom of the vertical pot type tank, and has a heat insulating layer and a heating jacket at the bottom, outer periphery and shoulder of the tank.
As a representative example, the situation of No. 5 is shown below. 21.7 kg of flakes of mushroom stem with a moisture content of 16.8% and 1.58 kg of corn starch (binder) were put into a crushing / mixer device, and the treatment times were 19.5 minutes, 20.2 minutes, C. Each was crushed and mixed for 22 minutes. The temperatures after the treatment were a. 146 ° C., b. 149 ° C., and c.

Next, the situation when polylactic acid is kneaded into the mixture of the flakes and the binder will be described. First, the used kneader will be described.
FIG. 2 is a schematic plan view of the kneader. Of the pair of rolls each having a heating jacket, one roll 10 has a number of shallow axial grooves b and a number of shallow spiral grooves a on the surface. The other roll 20 was a roll having a spiral groove a in the examples and comparative examples. These rolls are arranged horizontally with a minute gap, and are driven to rotate in a direction in which the facing portions face downward. Among the materials to be kneaded, polylactic acid is supplied in powder form through a hopper (not shown) provided above the left portion c of the two rolls. One mixture to be kneaded is supplied through a hopper (not shown) provided above the central portion d in the axial direction of the two rolls.

  The material to be kneaded forms a bank (bulk pool) at the upper part at the valley part between the two rolls, and after being squeezed by a minute gap at the lower part, it remains on the roll surface and is mixed into the bank again by roll rotation. While being repeated many times, the spiral groove a moves to the right in the axial direction. At the right end in the axial direction, one roll 10 and the right end thereof are pressed against each other at the surface, and a plurality of small holes are formed in the radial direction from the small holes of the ring-shaped granulation roll 30 to the inner diameter. Extruded to the side and cut into pieces by a scraper.

The powdered polylactic acid charged into the hopper provided above the portion c in FIG. 2 is compressed while repeating the compression between the two rolls, and the air accompanying the powder particles is discharged while the spiral groove. It is sent to the right side by the action of a, heated and melted by the heat from the heating jackets of both rolls and the heat generated by the kneading power, and reaches the center in the length direction of the rolls. The molten polylactic acid that has reached the central part d of the roll passes through a hopper (not shown) provided above the part d while continuously feeding and moving, and the mixture supplied from the above-mentioned pulverization / mixer device that is operated synchronously, They are continuously added at the same temperature (as much as possible) and kneaded and mixed while repeating the expansion.
As a result, polylactic acid achieves a close bond with the mixture while preventing uneven distribution, and is finally formed into pellets with a granulation roll.

The situation at the time of kneading of each test of A, B, and C described in Example No. 5 described above is that the gap between the rolls 10 and 30 is 0.5 mm, the inlet side of the roll 10; The outlet side: 110 ° C., and between the rolls 20, both the inlet side and the outlet side were slightly lower than the roll 10, and both roll temperatures were changed variously. As a result, it was possible to obtain good pellets in which uneven distribution was not observed even when the temperature changed for each of A, B, and C.
Each example other than Example No. 5 in Table 1 is the same as No. 5 except that the blending ratio and the type of binder are different. Addition of binder, further crushing, kneading with polylactic acid and pellets The process proceeded to molding. In each example, normal pellets with no uneven distribution were obtained.
In Example No. 12, 5% of carbon black was added as a colorant, and black pellets were obtained. And even if you rub in the palm, the palm never turned black.
In Example 13, 5% of zeolite was added as an attempt to reduce the specific gravity of the product, and a decrease in specific gravity was confirmed.
Example 14 was an addition of 5% rubber powder as an attempt to improve the impact strength of the product, and the effect was seen. In the present invention, not only the above three points but also various additives can be added to improve the function.

  In Comparative Example No. 21, normal pellets could not be obtained due to excessive bamboo material. Comparative Example No. 22 was able to retain the shape as a pellet, but as a result of longitudinal section observation, uneven distribution was observed. Comparative Example No. 23 was normal as a pellet.

A dumbbell test method and a Charpy impact test method were prepared by an injection shaping machine using the pellets manufactured from the above samples. The molding temperature was 170 ° C and the mold temperature was 40 ° C.
Table 2 shows the results of No. 5 (B) and No. 3 in comparison with the respective values of polypropylene resin (hereinafter referred to as PP).
From Table 2, tensile strength No. 5 (b) is slightly inferior to general PP, but it is superior to impact resistant PP, and No. 3 is superior to impact resistant PP. I understand.
In addition, in terms of bending strength, it can be seen that both No. 5 (b) and No. 3 outperform the impact resistant PP.
From the above, it can be said that these compositions have high mechanical strength comparable to PP. As a result of producing and testing a tensile test method under the same conditions as No. 5 and No. 3 using the pellets of Comparative Examples No. 22 and No. 23, both exceeded the values obtained by the production / test only with polylactic acid. It never happened.

  The method for producing a biodegradable composition using bamboo and the molded product have been described above. However, these are also the same biodegradable when other materials are used, that is, wood, rice husks, or a combination of these materials. It becomes the manufacturing method and molded article of a composition.

  Since the biodegradable composition and the molded product of the present invention are all made from plant-derived raw materials, they are carbon neutral, earth-friendly, and have both mechanical strength comparable to PP and excellent productivity. . Most importantly, further cost reduction can be realized, which makes it possible to use in a wider range of fields with price competitiveness with petroleum synthetic resin.

DESCRIPTION OF SYMBOLS 1 Material preparation process 2 Mixing process 3 Kneading process 4 Composition shaping | molding process 5 Product preparation processes 10 and 20 Kneading roll 30 Granulation roll
a spiral groove
b Axial groove
c Position of hopper supplying polylactic acid
d Location of the hopper that supplied the mixture of bamboo and straw derived material and binder

Claims (2)

A biodegradable resin composition comprising a plant material (A), a binder (B), and polylactic acid (C),
The content of the plant material (A) is 95 to 51% by mass, the content of the binder (B) is 17 to 2% by mass, and the content of the polylactic acid (C) is 35 to 3% by mass (these (A) to (C) total is 100% by mass), and the content of the binder (B) is less than the content of the polylactic acid (C),
The binder (B) comprises one or a combination of casein, soy protein, gluten, konjac potato powder, starch, dry starch, corn starch, tapioca,
The biodegradable resin composition characterized in that the plant material (A) is made of flakes. A material preparation step for crushing plant material (A) into flakes;
A binder mixing step of mixing the binder (B) 17-2% by mass with 95-51% by mass of the plant-based material made into the flakes (A);
In the mixture mixed in the binder mixing step, polylactic acid (C) is in the range of 35 to 3% by mass, and is less than the content of the binder (B) (the total of these (A) to (C) is A polylactic acid kneading step in which an amount of 100% by mass) is mixed and kneaded;
A method for producing a biodegradable resin composition comprising
Biodegradation characterized by using one or a combination of two or more of casein, soybean protein, gluten, konjac potato powder, starch, dry starch, corn starch, tapioca as the binder (B) For producing a conductive resin composition.

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