JP2000086799A - Non-leachable biodegradable resin extrusion foam molding body, biodegradable resin foam molded product using the same and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable resin extrusion foam-molding body that can readily be molded by thermal forming to formed products having a variety of shapes, for example, food-packaging vessels a water-cleaning material, a heat insulator, a buffering agent and the like, inhibits water-soluble substance from leaching out from the inside of the formed product, even when it comes into contact with water because of its non-leachability and has excellent dimensional stability and mechanical properties, provide a biodegradable resin formed foam and their production process. SOLUTION: This objective formed foam product is produced by extrusion forming a biodegradable resin foaming composition and simultaneously foaming the composition with the moisture-expanding power. The objective biodegradable resin extrusion foaming body is thermally formed vacuum-formed or pressureformed to a desired shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-elutable extruded and molded biodegradable resin foam, a biodegradable resin foam molded article using the same, and a method for producing the same. Not only can it be easily formed into various forms such as food packaging containers, water purification materials, heat insulation materials, cushioning materials, etc. due to its shape, etc. There is no elution of water-soluble components from the inside of the body, and the obtained molded body has excellent dimensional stability and mechanical properties. And their production methods.

[0002]

2. Description of the Related Art Conventionally, a wide variety of foams made of synthetic resins have been manufactured and utilized in a wide range of fields such as food packaging containers, water purification materials, heat insulation materials, and cushioning materials. recent years,
The demand for these synthetic resin foams tends to increase year by year, and as a result, the amount discarded increases year by year.
As a pollution problem, it has been gaining much public attention. However, recycling of waste synthetic resin foam requires various measures on a social scale, while incineration involves the prevention of harmful gases and the deterioration of incinerators caused by high heat. Therefore, there is a strong demand for the development of a foam that can be easily disposed of.

To meet such demands, various foams have been proposed in which these synthetic resins are replaced with biodegradable resins. For example, JP-A-5-306349, JP-A-5-306349
Japanese Patent Application Laid-Open No. 269875/1992 discloses a method in which a biodegradable resin chip impregnated with water is heated with oil to form foamed beads or foamed pellets, and then molded into a mold for heat shaping. A method is disclosed in which a biodegradable resin impregnated with is packed in a mold, and the entire mold is heated with oil to foam the foam, thereby obtaining a foam molded article. However, with these methods,
There is a problem that the adhesion between particles is poor and the mechanical properties of the molded product are low. Furthermore, since oil is used as the heating medium, oil tends to remain between the foam particles, and there is a problem that the oil gradually exudes and contaminates.

In order to improve the adhesion between the foam particles,
A method of molding with an adhesive has also been proposed, but many adhesives do not have biodegradability, and when such adhesives cover foam particles, the biodegradability is inhibited. Will be. On the other hand, adhesives derived from natural products such as starch and glue are good in terms of biodegradability, but because they are hydrophilic, they are susceptible to humidity and have extremely poor adhesion due to moisture absorption and water absorption. Therefore, there is a problem that the use environment is restricted.

Further, JP-A-5-320405 and JP-A-6-32928 disclose a method for producing foam particles comprising a cellulose derivative such as penzylated cellulose or cellulose acetate. It is also disclosed that the particles are packed in a mold and fused between the foam particles by steam heating to form a molded body. However, when a plasticizer is not blended with the cellulose derivative,
It is difficult to sufficiently fuse the foam particles by steam heating. On the other hand, when a plasticizer is blended with the cellulose derivative, if a sufficient amount of the plasticizer is present for fusing between the foam particles, the entire foam particles are plasticized during the heat fusion treatment. Therefore, the dimensional stability of the molded article obtained by the foam particles shrinking in the opposite direction is deteriorated, the mechanical properties are also reduced, and when the plasticizer is a polyhydric alcohol, etc. On contact, there is a problem that the plasticizer is eluted and contaminated due to water solubility. Further, when the amount of the plasticizer is reduced, there is a problem that the plasticization of the cellulose derivative becomes difficult, and the fusion between the foam particles during the molding becomes difficult.

On the other hand, Japanese Patent Application Laid-Open No. Hei 7-126337 discloses a biodegradable resin comprising a biodegradable resin having a melting point of 100 ° C. or higher and a low melting point biodegradable resin having a melting point of 100 ° C. or lower such as polycaprolactone. A method for producing a biodegradable resin foam by foaming a water-soluble resin composition with water is disclosed. However, this method is based on injection molding, in which the low-melting-point biodegradable resin is distributed throughout the inside of the molded body, and is discharged and gathered from the nozzle so as to wind around the nozzle at the time of injection. It only acts on the adhesion between the bodies and helps to prevent the occurrence of discontinuous boundaries caused by cavities or nests in the resulting molded article, and there is a problem if the molded article lacks surface smoothness. In addition, if the plasticity of the biodegradable resin composition is insufficient with only the low melting point biodegradable resin, it is necessary to further add a plasticizer, but a water-soluble polyhydric alcohol or the like is used as the plasticizer. In this case, there is a problem of contamination due to the dissolution of the plasticizer as described above. In Japanese Patent Application Laid-Open No. Hei 10-100264, when a foam particle made of a cellulose derivative is filled in a mold and subjected to heat shaping, a plasticizer of the cellulose derivative is previously adhered to the surface of the foam particle. It is also disclosed that the surface of the foam particles is thermoplasticized and fused to form a molded body. However, in this case, there is a problem that a step of attaching a plasticizer to the surface of the foam particles in advance is required, and the step becomes complicated. As described above, many researches and developments have been made on biodegradable resin foam molded articles composed of cellulose derivatives, but they are still insufficient, molding of foams is easy, and dimensional stability and mechanical properties of molded articles are still small. The number of biodegradable foams having good was low. Therefore, there has been a strong demand for the technical development of a biodegradable foam that is biodegradable, easy to mold in a mold at the time of shaping into a molded product, and has good mechanical properties.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the above-mentioned conventional foam and to easily form food packaging containers, water purification materials, heat insulation materials, cushioning materials, etc. by heat shaping or the like. Not only can it be molded into molded products of various forms, but because it is non-eluting, there is no elution of water-soluble components from the inside of the molded article even when it comes into contact with water, and dimensional stability and mechanical properties It is an object of the present invention to provide a good extruded biodegradable resin molded article and a method for producing the same, and to provide a molded biodegradable resin foam using the extruded foam molded article and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the above problems, and as a result, have found that a cellulose acetate resin, a polycaprolactone having a melting point at a temperature lower than the softening point of the resin, and a blowing agent As a specific foamable biodegradable resin composition containing water and, by extrusion and foaming by the vaporization and expansion force of water at the same time, the surface is substantially covered with a layer made of polycaprolactone,
It is possible to obtain a biodegradable resin extruded foam molded article having a non-elutable and rich surface smoothness. Further, by using the biodegradable resin extruded foam molded article, a food packaging container, a water purification material, a heat insulating material can be obtained. It has been found that in-mold molding when forming into various molded products such as materials and cushioning materials is easy, and that dimensional stability and mechanical properties are good. The present invention has been completed based on these findings.

That is, according to the present invention, cellulose cellulose
Acetate-based resin, polycaprolactone having a melting point at a temperature lower than the softening point of the resin, and a foamable biodegradable resin composition containing water as a foaming agent, at the same time as extrusion molding, the vaporization and expansion of water A non-elutable biodegradable resin extruded foam molded article characterized by being produced by foaming is provided. Further, according to the present invention, the foamable biodegradable resin composition comprises a cellulose acetate resin, polycaprolactone, talc, and water, and the biodegradable resin foam, polycaprolactone The present invention provides the above-described biodegradable resin extruded foam molded article, wherein the biodegradable resin extruded foam molded article is unevenly distributed in the surface layer portion than the core portion of the extruded foam molded article and substantially covers the surface of the extruded foam molded article. .

Further, according to the present invention, the extruded and foamed biodegradable resin molded article is formed into a desired shape by heat shaping, vacuum forming or pressure forming. Is provided.

On the other hand, according to the present invention, a cellulose acetate resin and a polycaprolactone having a melting point lower than the softening point of the resin are provided in a cylindrical container having an extrusion nozzle or a die in front thereof. The foamable biodegradable resin composition containing water as a foaming agent is charged, and while the biodegradable resin composition is being pushed to the extrusion nozzle, the temperature is raised to a fluid heating and pressurized state. And then extruding from the extrusion nozzle or die, and foaming and molding the same. Further, according to the present invention, the foamable biodegradable resin composition is a cellulose acetate resin,
The above production method is provided, comprising polycaprolactone, talc, and moisture.

Further, according to the present invention, the extruded biodegradable resin molded article is cut into beads or pellets, and then packed in a desired mold and subjected to heat shaping. The method for producing the biodegradable resin foam molded article, and the biodegradable resin extruded foam molded article is extruded into a sheet, foamed, molded, and then vacuum-molded or air-pressure molded into a desired shape. The present invention provides a method for producing the above-mentioned biodegradable resin foam molded article.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

1. Cellulose-acetate-based resin The cellulose-acetate-based resin used in the biodegradable resin extruded and foamed molded article of the present invention (hereinafter, simply referred to as "biodegradable resin foam") contains cellulose acetate as a main component. . The biodegradable resin that may be blended as an auxiliary component is not particularly limited as long as it is not eluted by contact with moisture, and any one that is generally used as a water-insoluble biodegradable resin is used. Can be used. Those corresponding to these include, for example, starch-based, cellulose-based, and the like. Cellulose acetate contained as a main component in a cellulose acetate resin is usually produced by reacting acetic acid with linter obtained from cottonseed or cellulose of wood pulp. The cellulose acetate used in the biodegradable resin foam of the present invention may be any of those grades which are generally commercially available as `` cellulose acetate ''. The degree of acetylation expressed by the weight ratio of bound acetic acid is preferably 45% or more, particularly 47 to 60% (cellulose 1).
The number of bound acetyl groups per unit is preferably 1.9 to 2.8). If the degree of acetylation is less than 45%, the melting temperature is too high, so that it is difficult to stably melt-mold the foam. In terms of physical properties, cellulose acetate is preferably soft or medium-hard, and _preferably has a surface hardness of Rockwell hardness, H _R = 80 to 100, and an impact strength of 20 to 30 kg-cm / cm. Used. Furthermore, from the viewpoint of moldability, a material having a softening point (flow temperature) at which softening starts to flow (outflow temperature) of 150 to 170 ° C. and a load of 18.6 k as defined in ASTM D648.
Those having a heat deformation temperature of 44 to 55 ° C. under the condition of gf / cm ² are preferably used. On the other hand, with a hard material, it is difficult to stably melt-mold a foam. Also,
Cellulose used for the biodegradable resin foam of the present invention.
Acetate-based resins include cellulose acetate acetopropionate and cellulose acetobutyrate mixed with propionic acid or butyric acid in addition to acetate having only acetic acid groups, and have melting points, water absorption, and solubility in solvents. The mixing ratio of the acid can be appropriately selected and used from the viewpoint of properties and the like.

2. Polycaprolactone Component The polycaprolactone component used in the biodegradable resin foam of the present invention comprises polycaprolactone having a melting point lower than the softening point of the cellulose acetate resin. Examples of such polycaprolactone include aliphatic polyesters represented by the following general formula,
Commercial products of this aliphatic polyester include, for example, "Tone" (trade name) sold by Nippon Unicar Co., Ltd.

[0016]

Embedded image (In the formula, R represents an aliphatic moiety, and n is a positive integer.)

The polycaprolactone used in the present invention is not only biodegradable, but also water-insoluble, and, more advantageously, has the function of plasticizing the cellulose acetate resin by heating. Even without adding any plasticizer necessary for producing a biodegradable resin foam, a good biodegradable resin foam having a high surface smoothness can be obtained. Because no is used, it is possible to avoid the adverse effects such as the dissolution of the plasticizer due to contact with water. Moreover, surprisingly, the blended polycaprolactone has a lower melting point than the cellulose acetate resin, so it is not uniformly distributed inside the biodegradable resin foam but contains polycaprolactone. While the biodegradable resin composition is heated and melted and pushed into the extrusion nozzle or die, the biodegradable resin foam is unevenly distributed on the surface layer of the biodegradable resin foam by moving from the center to the periphery, that is, from the core to the surface layer. Tend to. Further, as described above, the polycaprolactone used in the present invention needs to have a melting point not higher than the softening point of the cellulose acetate resin. Among them, the preferred melting point is 100 ° C. or less, and the particularly preferred melting point is around 60 ° C. By using polycaprolactone having such a melting point, polycaprolactone can be unevenly distributed in the surface layer of the foam. This polycaprolactone has good compatibility with various resins, improves impact resistance, and improves dimensional stability of a heat-formed molded product. On the other hand, when polycaprolactone having a melting point equal to or higher than the softening point of the cellulose-acetate resin is used, even if it is biodegradable, it does not function to plasticize. I can't get my body.

In the present invention, the compounding amount of polycaprolactone is in the range of 5 to 70 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the cellulose acetate resin. When the compounding amount is less than 5 parts by weight, the proportion of polycaprolactone in the surface layer of the foam is small, and during the heat shaping, the effect of thermoplasticizing the foam surface becomes insufficient. On the other hand, if the strength exceeds 70 parts by weight, the effect of adding the polycaprolactone does not appear, and the uneven distribution of polycaprolactone to the surface layer of the foam becomes excessive, resulting in deterioration of the finished appearance and moldability.

3. Foamable biodegradable resin composition The foamable biodegradable resin composition used in the biodegradable resin foam of the present invention is, as described above, a cellulose acetate resin, a predetermined amount of polycaprolactone, and a foaming agent. It is prepared by blending moisture as The mixing ratio of water as a foaming agent is 100% of a biodegradable resin mixture of cellulose acetate resin and polycaprolactone.
3 to 100 parts by weight, preferably 5 to 5 parts by weight based on parts by weight
0 parts by weight. As described above, in the biodegradable resin composition of the present invention, since polycaprolactone functions to plasticize the cellulose acetate resin, even if no other plasticizer is added, good biodegradability is obtained. A resin foam can be obtained, but if necessary, another plasticizer may be added as long as it is a water-insoluble plasticizer within a range not to impair the object of the present invention.

Further, other additives and the like may be added to the above-mentioned biodegradable resin composition as long as the object of the present invention is not impaired. Examples of the additives include a heat stabilizer, a foam control agent and a foaming aid. ,
And the like. Among them, talc, silicon oxide,
Foaming regulators such as inorganic fine particles such as titanium oxide, magnesium oxide, aluminum oxide and calcium silicate, and organic fine particles such as cellulose powder, chitin, chitosan, wood flour, and metal stearate, particularly talc are biodegradable. Since a suitable foaming property can be imparted to the resin composition,
Uniform and highly foamed foams are easily obtained. Such foam regulators may be used alone, respectively.
Two or more types may be used in combination. Further, for the purpose of improving foamability, neutralizing acidic substances by-produced during foam production and generating gas, for example, inorganic hydrogen such as sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, calcium carbonate, etc. Fine particles may be used in combination.
In addition, okara, wood flour, fu (wheat skin),
Rice flour, waste paper and the like can also be added. As a preferred embodiment of the biodegradable resin composition of the present invention, a cellulose-acetate-based resin, polycaprolactone, talc as a foaming regulator, and a biodegradable resin composition comprising water as a foaming agent, The extender described above may be added to the biodegradable resin composition. The blending amount of talc as the foaming regulator with respect to the biodegradable resin composition is in the range of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the cellulose acetate resin. If the blending amount is less than 5 parts by weight, the effect of blending talc does not appear, and an uneven and coarse foam is easily formed. On the other hand, if it exceeds 50 parts by weight, secondary aggregation of talc tends to occur, Again, uneven and coarse foams are likely to be formed.

4. Biodegradable resin foam (extruded foam molded article) and method for producing the same The biodegradable resin foam of the present invention is obtained by foaming the foamable biodegradable resin composition by the vaporization and expansion of water simultaneously with the extrusion molding. It is manufactured by having Therefore, the biodegradable resin foam of the present invention has the following features. Foamed with water. Since all materials are biodegradable, they can deal with various disposal processes compared to general-purpose plastic foam. Since it is non-eluting, there is no problem of elution of the plasticizer or the like even when it comes into contact with moisture. Because the surface is covered with a layer of polycaprolactone,
Secondary forming such as heat shaping is easy. Compared to starch-based biodegradable resin foams, impact performance does not fluctuate due to atmospheric humidity, and strength is superior. Excellent surface smoothness. Further, as described above,
The biodegradable resin foam of the present invention is characterized in that polycaprolactone is unevenly distributed in the surface layer of the foam. Here, the foam surface layer portion refers to a portion within a few mm outside the diameter when the cut area of the foam in the minor axis direction is converted into a circle. When polycaprolactone is extruded from a foamable biodegradable resin composition, the polycaprolactone is heated and melted together with the cellulose-acetate resin, and tends to move from the center to the surface layer while being pushed to an extrusion nozzle or a die. Therefore, the polycaprolactone is relatively small in the central portion of the foam, that is, the core portion, and the polycaprolactone is relatively large in the outer surface layer portion. If polycaprolactone is unevenly distributed on the surface layer of the foam, as a result, if the surface is not substantially covered with a layer composed of polycaprolactone,
In secondary molding such as heat shaping, it is difficult to fuse and mutually fuse, and molding workability deteriorates. As described above, since polycaprolactone is unevenly distributed in the surface layer portion of the foam, a foam molded article having mechanical strength such as bending strength that does not hinder practical use can be obtained.

The biodegradable resin foam is, as described above,
The foamable biodegradable resin composition is manufactured by extrusion molding and foaming by the vaporization and expansion of water at the same time, and the production method is described in detail below. A foamable biodegradable resin composition containing a cellulose acetate resin, polycaprolactone, and water (a foaming agent) is prepared in a predetermined ratio, and then in a cylindrical container having an extrusion nozzle or a die in front (for example, , Kneading extruder)
It is thrown into. As a method of introducing water into the cylindrical container, a predetermined amount of water may be contained in the biodegradable resin composition for foaming in advance, or the biodegradable resin or polycaprolactone may be biodegradable. Water itself may be added directly to the hopper together with the resin composition, as long as the biodegradable resin composition and water are supplied together. Also,
As described above, it is desirable that the amount of water is 3 to 100 parts by weight, preferably 5 to 50 parts by weight based on 100 parts by weight of the biodegradable resin composition. Next, the biodegradable resin composition is heated at 120 to 250 ° C., preferably 180 to 22 ° C. before being pushed to the extrusion nozzle.
The mixture is heated, melted and kneaded at a temperature of 0 ° C., and as a result, is brought into a fluidized heating and pressurized state.
extruded from m nozzles or dies. The melt-kneading time cannot be determined unequivocally because it varies depending on the discharge amount per unit time, the melt-kneading temperature, and the like, but may be any time long enough to uniformly melt-knead the mixture. The temperature of the nozzle or the die of the discharge unit may be the same as the melting and kneading temperature, but may be lower than the temperature within a range where discharge is possible. Here, the extruder used for melt kneading is under high temperature and high pressure, as long as the water is forcibly dissolved in the cellulose acetate,
Although any type of extruder may be used, a single-screw or twin-screw extruder is usually used. Thereafter, the molten biodegradable resin composition discharged from the nozzle or die pores has a different foaming start position depending on the temperature and the amount of water, but is usually 0.1 m from the nozzle or die portion.
Foaming is started from a distance of m away, and after the foaming is completed, it is formed into a shape conforming to the shape of the extrusion port. The shape of the nozzle or die pore to be extruded is round, triangular, square, rectangular, star,
It may be hollow or the like, and may be appropriately selected depending on the purpose.

The obtained biodegradable resin foam is usually used after being cut into beads or pellets for secondary molding, and the cut is made of the biodegradable resin in the foaming process. Preferably, the resin foam is cut. The reason is,
By cutting in the melt-plasticized state before the cellulose acetate resin composition solidifies in this way, the newly formed cut surface becomes smoother in the process of further expanding after cutting, so that the surface becomes smoother. This is because a foam having a smooth and rounded corner can be obtained, and the filling property in the mold is improved. Therefore, the stage before the extrudate expands to more than three times the nozzle or die pore diameter, preferably 1.5
Cut before swelling more than twice. This cutting length is cut so that the ratio of the major axis to the minor axis (major axis / minor axis) of the obtained bead-like or pellet-like foam is in the range of 1 to 10, preferably 1 to 3. If the ratio of long axis / short axis exceeds 10, the rod or string is formed, so that it is difficult to uniformly fill the mold, and density irregularities are likely to occur in the obtained molded article. The major axis / minor axis ratio here is the ratio of the length of the foam in the longest axial direction to the shortest axial direction. The size of the bead-like or pellet-like foam preferably has a diameter in a range of 3 to 20 mm, preferably 5 to 10 mm, when the cut area in the minor axis direction is converted into a circle. If it is less than this range, the foam becomes too small and the handleability deteriorates, while if it is too large, a large cavity is easily formed in the molded product obtained by filling and heat shaping in a mold. .

5. Biodegradable resin foam molded article and method for producing the same As described above, the biodegradable resin foam obtained according to the present invention has various forms depending on the shape of the nozzle or die to be extruded. Except when the material is cut to a predetermined size and used as it is or when the plate-like foam is vacuum-formed into a desired shape, usually, the biodegradable resin foam is cut into beads or pellets. It is secondarily molded by heat shaping or the like into a form suitable for various uses, and is used as a biodegradable resin foam molded article. The secondary molding method of foam is
A conventionally known heat shaping method is suitable. This method includes, for example, a method by a hot press, a method of heating in a heating bath, a method of blowing hot air by a hot air drying treatment machine,
There are methods of introducing steam or heated steam into the mold, and secondary foaming can also be expected by selecting these methods and optimizing the heating conditions at that time. The optimum temperature for filling and heat shaping the foam in the mold varies depending on the amount of polycaprolactone unevenly distributed on the surface layer.If the temperature is too low, poor adhesion between foams is likely to occur. Conversely, if the temperature is too high, thermal degradation, coloration, shrinkage of the foam and the like of the polycaprolactone are likely to occur, so that the temperature is usually preferably in the range of 120 to 200 ° C. Further, when performing heat shaping, it is also possible to increase the adhesive strength between the foams by attaching a binder to the foams, if necessary. At that time, it is desirable for the purpose of the present invention that the binder be biodegradable and water-insoluble.

The foamed biodegradable resin article of the present invention has the above-mentioned features. That is, it is biodegradable,
Even with incineration, there is no problem of toxic gas or incinerator deterioration,
Moreover, since it is non-eluting, the water-soluble component is not eluted from the inside of the molded article even when it comes into contact with water, and further, it has excellent dimensional stability and mechanical properties. Therefore, it is used in various applications that take advantage of its features, and the application is not particularly limited, but specific applications include, for example, food packaging containers, water purification materials, heat insulating materials, cushioning materials, and the like. .

[0026]

The present invention will be described below in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 [Production of foam and processing and evaluation of molded article] As a biodegradable resin, a soft cellulose diacetate manufactured by Teijin Limited (surface hardness (H _R ): 85, impact strength:
25 kgf · cm / cm ² , outflow temperature: 155 ° C, heat deformation temperature: 48 ° C, degree of acetylation: 57% (reference: 100 parts by weight), and polycaprolactone (trade name: TONE polymer) sold by Nippon Unicar Co., Ltd. P-787, melting point: 6
0 ° C., density: 1.145 g / cm ³ , molecular weight: 80,000)
(15 parts by weight), and talc (14 parts by weight) was added as a foaming regulator to form a biodegradable resin compound.
To this, water (31 parts by weight) is added as a foaming agent, supplied to a hopper of a melt-kneading extruder, heated and kneaded at a temperature of 180 ° C., and then extruded from a nozzle having a diameter of 1.5 mm. The extrudate was cut at a stage before expanding to more than 1.5 times the nozzle diameter to obtain a foam of a biodegradable resin. The obtained biodegradable resin foam had a major axis / minor axis ratio of 1.5 and a cut area in the minor axis direction of about 10 mm in circle conversion. Next, the foam is filled in a mold, and is subjected to heat shaping at 150 ° C. for 20 minutes by a method of blowing hot air with a hot air drier to obtain a foam molded product having a size that can be subjected to an evaluation test. Was. The following evaluation tests were performed on the obtained molded products. Table 1 shows the results. Flexural strength : Dimensions, effective length: 200 m in accordance with JIS K7221 (Bending test method for rigid foamed plastic)
m, width: 50 mm, height: 40 mm
Measure the bending strength. A bending strength of 0.8 kg / cm ² or more was judged as acceptable. Dissolution: For molded products, dimensions, length: 60 mm, width:
A test piece having a size of 30 mm and a height of 10 mm is prepared, immersed in 1 L of water in a 2 L beaker, and allowed to stand at room temperature for 48 hours to conduct a plasticizer dissolution test. After the test, the test piece is dried, and a change in the weight of the test piece and a change in the water quality of the water in the beaker are measured and observed to evaluate whether or not the plasticizer is dissolved. Extrusion foaming : Extrusion, foaming, difficulty in workability and setting conditions, finish appearance, foaming degree, etc., during molding,
Assess whether there is any disadvantage and make a comprehensive judgment.

[0028]

[Table 1]

Examples 2 to 4 In the same manner as in Example 1, cellulose diacetate, polycaprolactone and a foaming regulator component (talc) shown in Table 1 were blended in the proportions shown in the same table. Was prepared. To this, as a foaming agent, water was added at the ratio shown in the same table, and in the same manner as in Example 1, a foam of a biodegradable resin was obtained, and the obtained foam was subjected to heat shaping. A foam molded product was obtained. An evaluation test was performed on the obtained molded product.
Table 1 shows the results.

Comparative Examples 1 and 2 In Comparative Example 1, polyethylene glycol (3) having an average molecular weight of 400 was used as a plasticizer instead of polycaprolactone.
5 parts by weight), except that the same was used.
A foam and a foam molded product were obtained. About the obtained molded product,
An evaluation test was performed. Table 1 shows the results. Comparative Example 2
The same procedure as in Example 1 was repeated except that cellulose diacetate, polycaprolactone, and a foaming regulator component (talc) were used and the amounts were as shown in Table 1. A foam molded product was obtained. An evaluation test was performed on the obtained molded product. Table 1 shows the results.

From these evaluation results, it was found that if the amount of polycaprolactone having a melting point lower than the softening point of the cellulose acetate resin was too small, the foam of the polycaprolactone could be substantially formed in the layer of polycaprolactone. It was found that the surface of the molded product did not cover the surface of the molded product, and that the subsequent molding processability was inferior and that the molded product had no mechanical strength and, of course, hindered the extrusion foaming itself. In addition, it was found that when polycaprolactone was used, the water-soluble component did not elute from the inside of the molded product even when it came into contact with water, which proved to be advantageous for applications such as food trays. On the other hand, when polyethylene glycol was used as the plasticizer, elution of polyethylene glycol from the inside of the molded product was observed. Furthermore, it was confirmed that adding an appropriate amount of talc as a foam adjusting material is more advantageous in obtaining extruded foaming properties, furthermore, moldability and mechanical strength of a molded product.

[0032]

The biodegradable resin foam of the present invention is obtained from a biodegradable resin composition comprising a cellulose acetate resin and a polycaprolactone having a melting point lower than the softening point of the resin. And by applying a special foam manufacturing method that uses moisture as a foaming agent, it has excellent biodegradability compared to conventional biodegradable resins and is environmentally friendly,
Even if the incineration treatment is performed, not only the problem of toxic gas and deterioration of the incinerator is small, but also since it is non-eluting, there is no problem that the water-soluble component elutes from the inside of the molded article even when it comes into contact with water.
Moreover, since the surface of the foam is substantially covered with a layer made of polycaprolactone, it has excellent surface smoothness, and can be easily fused between foams when performing secondary molding by heat shaping or the like. As a result, a foam molded article having excellent mechanical properties can be obtained. Therefore, the biodegradable resin foam of the present invention can be used in various fields such as food packaging containers, water purification materials, heat insulation materials, cushioning materials, etc. by utilizing its features.

Claims (9)

[Claims] An extrudable biodegradable resin composition containing a cellulose acetate resin, a polycaprolactone having a melting point lower than the softening point of the resin, and water as a foaming agent. A non-eluting biodegradable resin extruded and foamed product, which is produced by simultaneously foaming with the vaporization and expansion of water. 2. The foamable biodegradable resin composition comprises a cellulose acetate resin, polycaprolactone, talc,
2. The extruded and molded biodegradable resin article according to claim 1, wherein the extruded and formed article comprises water and water. 3. The biodegradable biodegradable product according to claim 1, wherein the polycaprolactone is unevenly distributed on the surface layer rather than the core of the extruded foamed molded article, and substantially covers the surface of the molded article. Extruded resin moldings. 4. A biodegradable product obtained by subjecting the extruded and foamed biodegradable resin molded product according to claim 1 to a desired shape by heat shaping, vacuum forming or pressure forming. Resin foam molding. 5. A cylindrical container having an extrusion nozzle or a die in front thereof contains a cellulose acetate resin, polycaprolactone having a melting point lower than the softening point of the resin, and water as a foaming agent. The foamable biodegradable resin composition to be charged, and while the biodegradable resin composition is being pushed to the extrusion nozzle, the temperature is raised to a fluid heating and pressurized state, and then from the extrusion nozzle or die. Extrude,
The method for producing a biodegradable resin extruded foam according to any one of claims 1 to 3, wherein the molded article is foamed and molded. 6. The foamable biodegradable resin composition comprises a cellulose acetate resin, polycaprolactone, talc,
6. The method for producing an extruded and molded biodegradable resin according to claim 5, comprising: water and water. 7. The biodegradable resin according to claim 4, wherein the extruded biodegradable resin molded article is cut into beads or pellets, then packed in a desired mold and subjected to heat shaping. Method for producing foamed resin foam. 8. The biodegradable resin according to claim 4, wherein the extruded biodegradable resin molded article is extruded into a sheet, foamed, molded, and then vacuum molded into a desired shape. Method for producing foamed resin foam. 9. The biodegradable resin extruded foam according to claim 4, wherein the extruded biodegradable resin molded article is extruded into a sheet, foamed and molded, and then pressure-molded into a desired shape. Manufacturing method for resin foam molded products.