JP3802680B2 - Expandable resin composition having biodegradability - Google Patents

Description

【００４６】
実施例１〜１２、比較例１〜５
Ｐ１〜１０のポリ乳酸にポリスチレン樹脂を所定量とイソシアネート基２．７〜２．８当量／モルのイソシアネート化合物（「ミリオネートＭＲ−２００」日本ポリウレタン工業（株）製）をポリ乳酸に対して１．０重量％、タルク（「ＬＭＰ１００」富士タルク工業（株）製）１．０重量％を表２の組成になるように二軸混練機（ＰＣＭ３０、池貝鉄工（株）製）でシリンダー温度１８０℃で混練し、それぞれの樹脂組成物を得た。
【００４７】
これら樹脂組成物のＭＩを測定後、回転式の反応容器に樹脂組成物２０００部、発泡剤としてイソペンタン１２００部、メタノール２４０部を仕込み、密封した後、反応容器の回転数１０回／分、昇温速度２０℃／時間の割合で昇温し、７０℃に１時間保持した。その後、室温まで冷却し発泡剤含浸樹脂組成物を取りだし、風乾後、重量を測定し、含浸率を求めた。次いで得られた該樹脂組成物を水蒸気（９２℃、１分）で予備発泡させ、発泡倍率および生分解性を測定、評価した。
【００４８】
さらに、予備発泡粒子を１日熟成後、発泡成形機にて水蒸気圧０．５ｋｇ／ｃｍ²、加熱時間３０秒の条件にて３００×３００×３０ｍｍの発泡成形体を得、これら発泡成形体より試験片を切り出し、耐熱性及び圧縮応力を評価した。各々の評価の対照として市販の発泡スチレン「リューパール５５ＫＳＹ−３１７１」（大日本インキ工業（株）製）を用いた。評価を表２、表３に示した。
【００４９】
【表２】

【００５０】
【表３】

【００５１】
（評価結果）
ポリスチレン添加量が同一水準（添加量１０％）で、Ｌ／Ｄ比が９５／５〜５／９５の樹脂組成物の発泡倍率が優れており、Ｌ／Ｄ比が９０／１０〜１０／９０特に優れていた。Ｌ／Ｄが６０／４０未満〜４０／６０を超えないものは発泡体の耐熱性及び圧縮応力等の機械物性が低く、且つ発泡セルも大きいものであった。ポリスチレンの添加量１％以上で発泡セルは均一、微細となり、５％以上では現在使用されているポリスチレン発泡粒子と遜色のないレベルに達した。
【００５２】
実施例１１〜２０、比較例６〜８
Ｐ３のポリ乳酸にポリスチレン樹脂を所定量を配合し、ポリ乳酸に対してイソシアネート基が平均１．８当量／モル、平均２．０当量／モル（「ミリオネートＭＴ」日本ポリウレタン工業（株）製）、平均２．３当量／モル（「ミリオネートＭＴ」／「ミリオネートＭＲ−２００」日本ポリウレタン工業（株）製）、平均２．７当量／モル〜２．８当量／モル（「ミリオネートＭＲ−２００」日本ポリウレタン工業（株）製）、平均３．０当量／モル（「ＰＡＰＩ２０Ｊ」三菱化学（株）製）を所定量及びタルク（「ＬＭＰ１００」富士タルク工業（株）製）１．０重量％を表３に示す組成になるように二軸混練機（ＰＣＭ３０、池貝鉄工（株）製）でシリンダー温度１８０℃で混練し、それぞれの樹脂組成物を得た。以下、発泡剤の含浸、発泡テスト及び評価は実施例１〜１２、比較例１〜５と同様に行った。結果を表４、表５に示した。
【００５３】
【表４】

【００５４】
【表５】

【００５５】
実施例２１〜２３、比較例８〜１２
Ｐ３のポリ乳酸に表６に記載の樹脂を１０重量％配合してなる混合物に、ポリ乳酸に対してイソシアネート基２．７〜２．８当量／モルのイソシアネート化合物を２重量％添加し、二軸混練機（ＰＣＭ３０、池貝鉄工（株）製）を用いシリンダー温度１８０℃で混練し、それぞれの樹脂組成物を得た。
以下、発泡剤の含浸、発泡及び評価を実施例１〜１２、比較例１〜５と同様に行い、結果を表６、表７に示した。
【００５６】
【表６】

【００５７】
【表７】

【００５８】
【発明の効果】
以上、本発明の樹脂組成物は発泡性、耐熱性、機械物性は従来から用いられてきたポリスチレン（ＰＳ）に匹敵するものが得られ、生分解性も著しく優れており、地球環境保全に資する樹脂である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a foam resin composition used as a substantially biodegradable packaging material.
[0002]
[Prior art]
Plastic foam moldings that make use of lightness, shock-absorbing properties, and moldability are used in large quantities as packaging and packaging materials, and the materials used are chemical products made from petroleum such as polystyrene (PS) and polyolefin. Yes. For this reason, these products are difficult to dispose of after use, and if incinerated, the burned calories are high, and the incinerator is damaged. This is a major social problem.
[0003]
In addition, the influence on the natural state such as the pollution of rivers, oceans, etc., caused by the foamed moldings that have been discarded without being disposed of can no longer be ignored. Therefore, biodegradable resins that decompose in the ecosystem and have little impact on the global environment have been developed. For example, polyhydroxybutyrate resins synthesized in the body of microorganisms, polyesters composed of aliphatic glycols and aliphatic carboxylic acids, or polyester resins mainly composed of caprolactone have been proposed. However, since the former is produced by microorganisms, its purity is poor and its productivity is extremely poor and its use is restricted.
[0004]
The latter has good productivity because the raw materials are inexpensive and can be obtained in large quantities such as natural gas, but it is a crystalline resin and has a low glass transition point, so it is practical as a biodegradable foamed resin. Poor sex. Furthermore, since the raw material depends on petroleum and natural gas, if it is decomposed, carbon dioxide gas is newly added to the carbon dioxide gas system existing on the earth and does not contribute to the carbon dioxide suppression effect. Moreover, when it sees from a long term, since a raw material source is limited, it will become difficult to obtain in the end, and it cannot contribute to global environmental conservation in a true sense.
[0005]
Furthermore, glycolic acid and lactic acid are also obtained as biodegradable polymers by ring-opening polymerization of glycolide and lactide, and are used as medical fibers such as sutures. Therefore, as it is, it has not been used in large quantities for packaging purposes as a foamed molded product.
[0006]
[Problems to be solved by the invention]
The present invention is a foamable resin composition excellent in productivity while having biodegradability, i.e., it is almost decomposed by microorganisms and has a high productivity with little impact on the global environment when disposed after use. An object of the present invention is to provide a foamable resin composition that can withstand practical use. The present inventors have eagerly studied in detail about the indispensable conditions as a biodegradable resin having high foamability, that is, the types of base polymers, additives for adding high molecular weight and foaming, and addition conditions. As a result of repeated studies, a biodegradable foamed resin composition having practically sufficient productivity was found, and an invention proposal (Japanese Patent Application No. 9-314479) has already been made. However, the foamed resin obtained in the present invention has a slightly larger foam cell than the currently used foamed polystyrene, and is therefore somewhat insufficient in fields requiring heat insulation and compression characteristics.
[0007]
[Means for Solving the Problems]
As a result of diligent research to solve such problems, the present inventors blended a small amount of an amorphous resin having a high glass transition temperature with an amorphous resin into a biodegradable resin, so that the foam cell is small and heat insulating, The present inventors have found a resin composition excellent in compression characteristics and have reached the present invention.
[0008]
That is, in the present invention, polylactic acid (A) having a molar ratio of L-form to D-form of 95/5 to 60/40, or 40/60 to 5/95, polycarbonate, polystyrene, and glass transition temperature are 60 ° C. At least one amorphous resin (B) selected from the above group of copolymerized polyethylene terephthalate is blended at a ratio of A / B = 99/1 to 80/20, and isocyanate groups ≧ 2.0 equivalents / This is a resin composition containing 0.5 to 5% by weight of a polyisocyanate compound in a molar amount relative to the polylactic acid (A).
[0009]
DETAILED DESCRIPTION OF THE INVENTION
First, biodegradable resin, which is one of the basic conditions, minimizes the increase in carbon dioxide in the natural world, and considering the productivity and cost that can withstand practical use, cereal starch such as corn is used as the starting material. A polylactic acid resin using lactic acid as a raw material is preferable. However, what is usually used for fibers requires crystallinity, so that the optical isomer L form is almost 100%. On the other hand, in order to form a foam, at least the crystallinity needs to be as small as possible. The reason is that the crystalline resin progresses in crystallization in the step of impregnating the foaming agent, thereby inhibiting the foamability.
[0010]
In order to impart amorphousness to the polylactic acid used as the base polymer, the molar ratio of L-form to D-form needs to be 95/5 to 5/95. Although it is satisfactory that lactic acid is amorphous, the glass transition point is less than 50 ° C. and the practicality is lost.
[0011]
Therefore, the polylactic acid referred to in the present invention is a substantially amorphous polylactic acid resin obtained by ring-opening polymerization of lactide, and the molar ratio of L-form to D-form is 95/5 to 60/40, Alternatively, lactic acid in the range of 40/60 to 5/95 is used. When the molar ratio of L-form to D-form exceeds 95/5 or less than 5/95, the crystallinity is high, the foaming ratio does not increase, and foaming becomes uneven and cannot be used. The molar ratio of L-form to D-form is preferably 90/10 to 70/30, or 30/70 to 10/90.
[0012]
On the other hand, the resin used for foaming the beads needs to suppress as much as possible the volatilization of the foaming agent impregnated in advance during storage until the foam is molded. For this purpose, a resin having a glass transition temperature higher than normal temperature is selected. As long as polylactic acid is an L-form / D-form copolymer in the above-mentioned range, it has a glass transition temperature of 50 ° C. or higher, which is very advantageous compared to other biodegradable resins. A hydroxy acid other than lactic acid or a copolymer of glycol and dicarboxylic acid is not preferred because the glass transition point is lowered. Of course, in the production of an extruded foam sheet, a higher glass transition temperature is advantageous in order to reduce the volatilization of the foaming agent and increase the foamability.
[0013]
The polylactic acid used in the present invention is preferably a high molecular weight polylactic acid, and its melt viscosity is in the range of 1 to 10 in terms of melt index value according to JIS K 7201 (load 2.16 kgf), more preferably 1 to 1. The range is 5.
Polylactic acid having a melt viscosity of less than 1 is difficult to produce by the generally used method described below, and polylactic acid having a melt viscosity of more than 10 is not preferable because only a foam having a low expansion ratio can be obtained.
[0014]
The reason for this is that the reaction with the polyisocyanate compound described below uses the same high viscosity resin composition, a low melt viscosity (low molecular weight) resin, and a high melt viscosity (high molecular weight) resin. This is because the reaction (branch) density is different between the polymer and the polyisocyanate compound, and the low melt viscosity (low molecular weight) resin has a higher reaction (branch) density, and therefore, it is considered that it takes a crosslinked structure and inhibits foaming.
[0015]
As a means of obtaining poly (lactic acid) with high melt viscosity (high molecular weight), high pressure in a normal reaction kettle, melt polymerization with good stirring efficiency, melt polymerization with a biaxial kneading reactor, high vacuum It is possible to obtain polylactic acid having a high melt viscosity (high molecular weight) of 1 to 10 in terms of melt index by a combination of thin film polymerization method, melt polymerization and solid phase polymerization, but the reaction cycle becomes longer because of high viscosity. Therefore, it is necessary to pay sufficient attention to the decrease in productivity and the deterioration in quality due to thermal decomposition of the resin.
[0016]
On the other hand, the required properties of the amorphous resin used in the present invention include a high glass transition point, affinity with a foaming agent, and gas barrier properties in addition to amorphous properties. Amorphous and high glass transition points are necessary conditions for the foamable resin, and affinity with the foaming agent is a characteristic directly related to foamability. Crystalline resin is not preferable because crystallization proceeds in the impregnation step of the foaming agent, and the crystal inhibits foaming. The glass transition point is required to be equal to or higher than the glass transition point of polylactic acid in terms of gas barrier properties, and is 50 ° C. or higher, preferably 60 ° C. or higher. Furthermore, in order to impregnate the resin with the foaming agent, it is necessary to appropriately extend the intermolecular distance of the resin with the foaming aid, and the affinity between the amorphous resin and the foaming aid is important. As a result of extensive studies on these matters, the present inventors have found that amorphous resins such as polycarbonate, polystyrene, and copolymerized polyethylene terephthalate are preferable.
[0017]
All of these resins satisfy the requirements of amorphousness, high glass transition point, affinity with foaming agents, and gas barrier properties. For example, regarding the high glass transition point, there are polycarbonate 120 ° C., polystyrene 75 ° C., cyclohexanediol / polyethylene terephthalate copolymer 80 ° C., etc., and any resin swells in alcohols which are one of foaming aids. Therefore, even these resins alone have good foamability except for biodegradability.
[0018]
However, even if a foaming agent is impregnated and foamed into a resin composition in which polylactic acid and an amorphous resin having a certain degree of viscosity are kneaded, foaming ratio is low and it is difficult to withstand practical use as it is. In order to obtain a high expansion ratio, it is necessary to further increase the melt viscosity (high molecular weight).
[0019]
As a result of intensive studies, the present inventors have determined that the polyisocyanate compound having an isocyanate group ≧ 2.0 equivalents / mol is 0.5 to 5% by weight, preferably 1 to 3% by weight based on the polylactic acid having a melt index value of 1 to 10. % Was mixed and reacted in a molten state to obtain a desired high melt viscosity resin composition.
[0020]
If the polyisocyanate compound is less than 0.5% by weight, the melt viscosity of the resin composition does not increase so much. If the polyisocyanate compound exceeds 5% by weight, unreacted polyisocyanate compound remains or the branch density increases, resulting in a crosslinking reaction. Progresses to produce a large amount of gelled product, and foamability is reduced.
[0021]
Further, the number of isocyanate functional groups of the polyisocyanate compound is required to be 2.0 equivalent / mol or more, and preferably 2.3 equivalent / mol or more. By increasing the number of isocyanate functional groups of the polyisocyanate compound as much as possible, and increasing the viscosity without increasing the number of branch points, the formation of gelled products can be suppressed.
[0022]
The blending ratio of polylactic acid and amorphous resin is preferably 99/1 to 80/20, more preferably 99/5 to 90/10. If the blending ratio is smaller than this range, the size reduction, thermal insulation and compression characteristics of the foamed cell are hardly improved. If the blending ratio exceeds this range, foaming spots due to poor dispersion due to the compatibility of both resins are not preferable. Furthermore, the original purpose of the foamable resin having biodegradability is impaired.
[0023]
A known method can be used as a method of mixing and reacting polylactic acid and an amorphous resin with a polyisocyanate compound in a molten state to increase the molecular weight. For example, a method in which a polyisocyanate compound is added to pelletized polylactic acid and an amorphous resin and melt-mixed with a uniaxial or biaxial kneader or the like, or polylactic acid and amorphous resin are previously uniaxial or biaxial kneader or the like The purpose is to add a polyisocyanate compound after being melted in a melt, to produce polylactic acid by melt polymerization with a uniaxial or biaxial kneader or the like, or to add an amorphous resin and a polyisocyanate compound during production. A highly viscous resin composition can be obtained.
[0024]
The kneading of the polylactic acid and the amorphous resin is desirably a blend that does not substantially involve a reaction. Therefore, it is necessary to pay attention to deterioration of physical properties of the polycarbonate and copolymerized polyethylene terephthalate due to the transesterification reaction.
[0025]
There are various compounds such as acid anhydrides, acid chlorides, carbonates, epoxies, etc. in addition to isocyanate compounds as additives for further increasing the molecular weight of polylactic acid as a base polymer. However, other compounds cannot achieve a sufficiently high molecular weight and have insufficient foamability. The polyisocyanate compound is considered to be increased in molecular weight by the reaction with polylactic acid and the polyisocyanate compound is further increased in molecular weight by an allophanate bond, and this bond is once dissociated when melted. The melt fluidity is improved, which is very convenient. In addition, when the resin composition is cooled and solidified, the allohanate bond is formed again and increases to the desired viscosity.
[0026]
The polyisocyanate compound used includes aromatic, alicyclic, and aliphatic polyisocyanates. For example, the aromatic polyisocyanate has tolylene, diphenylmethane, naphthylene, tolidine, xylene, and triphenylmethane as a skeleton. Polyisocyanate compounds, alicyclic polyisocyanates include isophorone, polyisocyanate compounds having a hydrogenated diphenylmethane skeleton, and aliphatic polyisocyanates include polyisocyanate compounds having a skeleton of hexamethylene and lysine, both of which can be used. However, from the viewpoint of versatility, handleability, weather resistance, and the like, tolylene, diphenylmethane, particularly polyisocyanate of diphenylmethane is preferably used.
[0027]
After pre-foaming and secondary foam, very fine foam cells were formed, which were inferior to currently used polystyrene foam cells. The reason for this is that an amorphous resin, which is easy to foam, is microdispersed in polylactic acid, so that the number of foaming origins becomes extremely large and foams all at once from the foaming origin. It is done.
[0028]
The resin composition of the present invention is made into pellets or beads, and then impregnated with a foaming agent and a foaming aid. The impregnated particles are usually heated to primary foaming (pre-foaming) to form foamed particles having a foaming ratio of 30 to 50 times, and then filled into a mold and further heated to secondary foam, and the desired molding. Mold into the body.
[0029]
The size of the pellet or bead impregnated with the foaming agent and the foaming aid is appropriately selected according to the size, shape, etc. of the molded body. In the case of foamed polystyrene, the diameter is usually 0.5-2 mm. Used. In the case of a precise molded body, a diameter of 0.5 to 1 mm is common.
[0030]
Examples of the foaming agent and foaming aid used herein include hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, and hexane, and halogens such as methyl chloride, methylene chloride, and dichlorodifluoromethane. Hydrocarbons, ethers such as dimethyl ether and methyl ethyl ether, etc. are used as foaming agents, and alcohols having 1 to 4 carbon atoms, ketones, ethers, benzene, toluene and the like are used as foaming aids.
[0031]
The combination of the foaming agent and the foaming aid must be appropriately selected depending on the resin to be used. Butane, pentane or a mixture thereof is used as the foaming agent, and the foaming aid combined with this is one having 1 to 4 carbon atoms. Hydric alcohol is preferred. There are various other combinations and can be selected in view of the purpose and economy.
[0032]
The use ratio (volume ratio) of the foaming agent and the foaming aid can be foaming agent / foaming aid = 1/2 to 10/1, but varies depending on the combination of the foaming agent and the foaming aid. 1-5 / 1 is common. The impregnation amount of the foaming agent and the foaming aid varies depending on the target foaming ratio and the storage period of the pellets or beads, but the foaming agent is usually 5 to 15% by weight. Generally, a low foam product can be handled by reducing the impregnation amount, and a high foam product can be handled by increasing the impregnation amount.
[0033]
The pellets or beads impregnated with the foaming agent and the foaming aid are pre-foamed and then placed in a desired mold and further heated to foam, and the pellets or beads are fused together to form a strong molded body. Mold. This is basically the same as the molding method of polystyrene (PS) foam. That is, steam having a large heat capacity is used for both preliminary foaming and foam molding. Although foaming with hot air is possible, the foaming efficiency is not good because the heat capacity is small. Therefore, it is unsuitable for highly foamed products.
[0034]
In order to form a more uniform and fine foam cell, it is useful to add a foam nucleating agent. Examples of the foam nucleating agent to be used include solid particles such as talc, silica, kaolin, zeolite, mica. Inorganic particles such as alumina, carbonates or bicarbonates, salts such as alkali metal salts of carboxylic acids are preferably used. Among these, talc is particularly preferably used for the resin composition of the present invention.
[0035]
As the nucleating agent, those having a particle diameter of about 0.5 to 30 μm are preferable because the dispersion state with respect to the resin is good and stable bubbles are obtained. The amount to be added is usually 0.1% by weight or more, preferably 30% by weight at the most with respect to the resin composition. A more preferred range is 0.5 to 5% by weight. If less than 0.1% by weight, no effect is observed. If the added amount exceeds 30% by weight, the effect is limited, and the advantage is that it is lightweight due to a decrease in mechanical properties and an increase in specific gravity. Will be damaged.
[0036]
Further, other additives can be appropriately added according to the purpose, and examples thereof include a heat stabilizer, an antioxidant, an ultraviolet absorber, and a plasticizer. However, flame retardants are often halides such as chlorine and bromine, and should be kept to a minimum from the viewpoint of generation of harmful substances during biodegradation and incineration.
[0037]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The evaluation was performed by the following method.
[0038]
(Evaluation methods)
(1) MI: Polylactic acid: Measured by a method based on JIS K 7210. Measurement conditions: measurement temperature 190 ° C., orifice diameter 2 mm, load 2.16 kgf.
Resin composition: Measured by a method based on JIS K 7210. Measurement conditions: measurement temperature 190 ° C., orifice diameter 2 mm, load 21.6 kgf.
[0039]
(2) Foaming ratio (times): Using a graduated cylinder, the volume before foaming of the foaming agent impregnated pellets and the volume of the pre-foamed particles were measured, and the foaming ratio (times) was calculated by the following formula.
Expansion ratio (times) = volume of pre-expanded particles / volume before expansion of foaming agent impregnated pellets
(3) Foamed cell evaluation: Foaming agent-impregnated resin composition and foaming polystyrene particles ("Lyupearl 55KS Y-3171" manufactured by Dainippon Ink Industries, Ltd.) as a control were foamed 30 to 35 times by steam treatment, The states of the foamed cells cut and produced on the plane passing through the center point of the foamed particles were relatively compared.
A: The size of the expanded cell is similar to that of the expanded polystyrene. ○: The expanded cell size is slightly larger than the expanded polystyrene. X: The expanded cell size is clearly larger than the expanded polystyrene. That cannot be compared [0041]
(4) Biodegradability: Pre-expanded particles were placed in compost for 2 months and evaluated in the following manner in the appearance.
A: Almost completely decomposed and there is a very small amount of residue visually. ○: Most of the residue is decomposed and disappeared, but there is a residue that is not partially decomposed visually. Δ: A portion is decomposed and disappeared. Residues that do not substantially decompose visually: No change at all visually [0042]
(5) Heat resistance: A foam was molded from the pre-foamed particles, and a test piece of 100 × 100 × 30 mm was cut out from the foamed molded product and evaluated by dimensional change when treated in an oven at 100 ° C. for 2 hours.
◎: No change ○: Change less than 3% Δ: Change less than 3-10% ×: Change of 10% or more −: Foam molded article cannot be collected and compared
(6) Compressive stress ratio: A 30 × 30 × 30 mm test piece was cut out from the foam, measured at a load speed of 10 mm / min, and evaluated by a stress ratio with polystyrene (PS) at 50% compression.
[0044]
Production Example Polylactic acid: Commercially available L-lactide and D-lactide were purified by recrystallization using ethyl acetate. Purified L-lactide, D-lactide, and tin octylate as a catalyst were charged in a predetermined amount of autoclave with stirring, degassed under reduced pressure, and then subjected to a polymerization reaction at a predetermined temperature and for a predetermined time in a nitrogen gas atmosphere to obtain the results in Table 1. .
[0045]
[Table 1]

[0046]
Examples 1-12, Comparative Examples 1-5
A predetermined amount of polystyrene resin is added to polylactic acid of P1 to 10 and an isocyanate compound ("Millionate MR-200" manufactured by Nippon Polyurethane Industry Co., Ltd.) having an isocyanate group of 2.7 to 2.8 equivalents / mol is 1 per polylactic acid. A cylinder temperature of 180 wt.% And a talc (“LMP100” manufactured by Fuji Talc Kogyo Co., Ltd.) 1.0 wt. Each resin composition was obtained by kneading at ° C.
[0047]
After measuring the MI of these resin compositions, 2000 parts of the resin composition, 1200 parts of isopentane and 240 parts of methanol as a blowing agent were charged in a rotary reaction vessel and sealed, and then the reaction vessel was rotated at a rate of 10 revolutions / minute. The temperature was raised at a rate of 20 ° C./hour and held at 70 ° C. for 1 hour. Then, it cooled to room temperature, took out the foaming agent impregnation resin composition, air-dried, measured the weight, and calculated | required the impregnation rate. Next, the obtained resin composition was prefoamed with water vapor (92 ° C., 1 minute), and the expansion ratio and biodegradability were measured and evaluated.
[0048]
Further, after pre-expanded particles were aged for one day, a foam molded body of 300 × 300 × 30 mm was obtained with a foam molding machine under conditions of a water vapor pressure of 0.5 kg / cm ² and a heating time of 30 seconds. A test piece was cut out and evaluated for heat resistance and compressive stress. As a control for each evaluation, a commercially available foamed styrene “Lyupearl 55KSY-3171” (manufactured by Dainippon Ink Industries, Ltd.) was used. The evaluation is shown in Tables 2 and 3.
[0049]
[Table 2]

[0050]
[Table 3]

[0051]
(Evaluation results)
The foaming ratio of the resin composition having the same polystyrene level (added amount 10%) and L / D ratio of 95/5 to 5/95 is excellent, and the L / D ratio is 90/10 to 10/90. Especially excellent. When L / D was less than 60/40 to 40/60, the mechanical properties such as heat resistance and compressive stress of the foam were low, and the foamed cells were large. When the addition amount of polystyrene was 1% or more, the foamed cells became uniform and fine, and when the addition amount was 5% or more, it reached a level comparable to the polystyrene foam particles currently used.
[0052]
Examples 11-20, Comparative Examples 6-8
A predetermined amount of polystyrene resin is blended with P3 polylactic acid, and the average isocyanate group is 1.8 eq / mol, average 2.0 eq / mol with respect to polylactic acid ("Millionate MT" manufactured by Nippon Polyurethane Industry Co., Ltd.) 2.3 equivalents / mole on average ("Millionate MT" / "Millionate MR-200" manufactured by Nippon Polyurethane Industry Co., Ltd.), average 2.7 equivalents / mole to 2.8 equivalents / mole ("Millionate MR-200") Nippon Polyurethane Industry Co., Ltd.), an average of 3.0 equivalents / mol (“PAPI20J” manufactured by Mitsubishi Chemical Co., Ltd.) and 1.0% by weight of talc (“LMP100” manufactured by Fuji Talc Industry Co., Ltd.) Each resin composition was obtained by kneading at a cylinder temperature of 180 ° C. with a biaxial kneader (PCM30, manufactured by Ikekai Tekko Co., Ltd.) so as to have the composition shown in Table 3. Hereinafter, impregnation of the foaming agent, foaming test and evaluation were performed in the same manner as in Examples 1 to 12 and Comparative Examples 1 to 5. The results are shown in Tables 4 and 5.
[0053]
[Table 4]

[0054]
[Table 5]

[0055]
Examples 21-23, Comparative Examples 8-12
2% by weight of an isocyanate compound having an isocyanate group of 2.7 to 2.8 equivalents / mol based on polylactic acid is added to a mixture obtained by blending 10% by weight of the resin described in Table 6 with P3 polylactic acid. Each resin composition was obtained by kneading at a cylinder temperature of 180 ° C. using a shaft kneader (PCM30, manufactured by Ikekai Tekko Co., Ltd.).
Hereinafter, impregnation, foaming and evaluation of the foaming agent were performed in the same manner as in Examples 1 to 12 and Comparative Examples 1 to 5, and the results are shown in Tables 6 and 7.
[0056]
[Table 6]

[0057]
[Table 7]

[0058]
【The invention's effect】
As described above, the resin composition of the present invention has foamability, heat resistance, and mechanical properties comparable to those of polystyrene (PS) that has been conventionally used, and is extremely excellent in biodegradability, contributing to global environmental conservation. Resin.

Claims (7)

  Polylactic acid (A) having a molar ratio of L-form to D-form of 95/5 to 60/40, or 40/60 to 5/95, polycarbonate, polystyrene, and copolymer polyethylene terephthalate having a glass transition point of 60 ° C. or higher And an amorphous resin (B) selected from the group of A / B = 99/1 to 80/20, and a polyisocyanate compound having an isocyanate group ≧ 2.0 equivalents / mol is added to the polylactic acid. A resin composition containing 0.5 to 5% by weight.   The resin composition according to claim 1, wherein the polylactic acid has an L-form and D-form molar ratio of 90/10 to 70/30, or 30/70 to 10/90.   The resin composition according to claim 1, wherein the isocyanate compound has an isocyanate group ≧ 2.3 equivalent / mol.   The resin composition according to claim 1, wherein the amount of the isocyanate compound is 1 to 3% by weight.   The resin composition according to claim 1, wherein the blending ratio of polylactic acid and amorphous resin is 95/5 to 90/10.   The resin composition according to claim 1, wherein the amorphous resin is polystyrene. Expanded particles comprising the resin composition according to any one of claims 1 to 6.