JPH11140214A - Biodegradable cellulose acetate foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject foam capable of expressing an excellent antimicrobial property and capable of being easily molded into various kinds of molded products by using cellulose acetate and combining specific foam characteristic with the antimicrobial characteristic of acetic acid. SOLUTION: This biodegradable cellulose acetate foam is produced from cellulose acetate as a biodegradable raw material, has foam characteristics comprising a foam cell diameter of 0.001-0.8 mm and an apparent density of 0.01-0.27 g/cm<3> without relating to the shape of the foam, and contains acetic acid released from the cellulose acetate. It is preferable that the content of the acetic acid released from the cellulose acetate and remaining in the foam is >=3 ppm, when 10 g of a foam sample is sealed in a closed vessel having a volume of 500 cc, left at a temperature of 20 deg.C in a relative humidity of 65% for 24 hr and subsequently measured to determine the amount of the acetic acid in air in the vessel. The foam has excellent biodegradability, an excellent antimicrobial property and an easy incineration property, and can sanitarily be used also after molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cellulose acetate biodegradable foam and a method for producing the same. More specifically, the present invention relates to a cellulose acetate biodegradable foam having excellent antibacterial properties suitable for various uses such as a heat insulating material, a cushioning material, and a food packaging material, and a method for stably obtaining the foam.

[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 heat insulating materials, cushioning materials, and food packaging containers. In recent years, the demand for these synthetic resin foams has been increasing year by year, and as a result, the amount discarded has also been increasing year by year, and has been greatly highlighted as an environmental problem and a pollution problem. However, recycling of waste synthetic resin foams requires various measures on a social scale, while incineration involves a lot of prevention of toxic gas generation and prevention of deterioration of thermal incinerators due to high heat generation. There are many problems, and development of a foam which can be easily disposed of has been strongly desired.

In response to such demands, various foams have been proposed in which these synthetic resins (for example, polystyrene) are replaced with biodegradable resins. For example, JP-A-6-13
No. 6,168, JP-B 5-65536, JP-A-6-335919, JP-A-8-151469, JP-A-8-59892, and the like. Are disclosed. Also, Japanese Patent Application Laid-Open No. HEI 6-15753 discloses a method in which foamed beads containing pulp as a main raw material are filled in a molding frame and fused to obtain a molded product. Further, Japanese Patent Application Laid-Open No. 5-320405 discloses a method of obtaining a molded body mainly by in-mold molding using expandable wood-based resin particles obtained by adding a foaming agent to non-solution chemically modified wood. . JP-A-6-32928 discloses a method of obtaining a foamed sheet from a foamable wood-based resin obtained by impregnating a non-solution-based chemically modified wood with a foaming agent to obtain a container-shaped molded product. . Further, in JP-A-8-3357, a biodegradable resin composed of acetate or a substance containing the same and at least substantial water are charged as raw materials, and after being heated and pressurized, rapidly released and foamed, After that, a method of forming into a predetermined shape by a forming die is disclosed. However, when the foamed molded article obtained by these methods is used as a heat insulating material or a cushioning material, since natural materials and derivatives thereof are used as raw materials, bacteria and small organisms are generated, which adversely affects products. In particular, when used for food applications, there is a problem in terms of hygiene.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to easily form various molded articles such as a heat insulating material, a cushioning material, and a food packaging material. And a biodegradable cellulose acetate foam with excellent antibacterial properties that does not generate bacteria or small organisms even when used in various applications, is hygienic, and does not adversely affect the enclosed product. It is to provide a manufacturing method thereof.

[0005]

Means for Solving the Problems The present inventors have used cellulose acetate as a biodegradable material,
As a result of trying to solve the above-mentioned problems, it has been found that the above-mentioned problems can be achieved only by combining a specific foam property and an antibacterial property with acetic acid.

That is, according to the present invention, there is provided the following cellulose acetate biodegradable foam.

(1) A biodegradable cellulose acetate foam having a foam cell diameter of 0.001 to 0.8 mm,
A cellulose acetate biodegradable foam, which has a foam property having an apparent density of 0.01 to 0.27 g / cm ³ and contains acetic acid released from cellulose acetate.

(2) 10 g of a foam sample is sealed in a 500 cc capacity closed container, and the temperature is 20 ° C. and the relative humidity is 6
The cellulose acetate biodegradable foam according to the above (1), wherein the amount of acetic acid in the air in the container after standing for 24 hours at 5% is 3 ppm or more.

(3) The foam is foamed particles having a diameter of 3 to 200 mm, and has a total surface area and a foam cell diameter of 0.1 m.
The cellulose acetate biodegradable foam according to the above (1), wherein the ratio of the surface area of a portion where the foam cells of m or more are exposed to the surface of the particle satisfies the following expression. (Surface area of exposed part of foam cell / total surface area) ≦ 1 / (2 + 4 ×
(Long axis / short axis))

(4) The foam is a wrinkled foam sheet having a thickness of 1 to 50 mm and a wrinkle height h of 2 to 10
(1) The cellulose acetate biodegradable foam according to the above (1), wherein the distance between w and w is 2 to 10 mm.

(5) The foam has a thickness of 0.5 to 25 mm
And a foamed sheet having no wrinkles on the surface and having tensile strengths of 110 to 900 g / c in the vertical and horizontal directions, respectively.
m, a cellulose acetate biodegradable foam according to the above (1) having a weight of 30 to 220 g / cm.

(6) A cellulose acetate biodegradable foam integrally formed by bonding the foamed particles according to (3) with a binder.

(7) A biodegradable cellulose acetate foam obtained by thermally shaping the foamed sheet according to (4) or (5). Further, according to the present invention, there is provided the following method for producing a cellulose acetate biodegradable foam.

(8) Consisting of cellulose acetate (A), plasticizer (B) and foam nucleating agent (C), (A):
The compounding weight ratio of (B) :( C) is (100) :( 0-8
0): Water (E) as a foaming agent was mixed with the mixed raw material (D) of (2 to 50) at a blending weight ratio of 2 to 100 with respect to (D), and the mixture (F) was melted. In producing a foam by extrusion, after melting at a temperature of 150 to 250 ° C., weighing at a temperature of 120 to 220 ° C., and then shearing at a rate of 1000 to 1000
A method for producing a cellulose acetate biodegradable foam, comprising extruding at 20,000 sec ^-1 .

(9) Cellulose acetate (A), plasticizer (B) and foam nucleating agent (C), (A):
The compounding weight ratio of (B) :( C) is (100) :( 0-8
0): Water (E) as a foaming agent was mixed with the mixed raw material (D) of (2 to 50) at a blending weight ratio of 2 to 100 with respect to (D), and the mixture (F) was melted. Extrusion, then
A method for producing a cellulose acetate biodegradable foam, which comprises heat-treating at a temperature of 100 to 150 ° C. and a surface pressure of 5 to 40 kgf / cm ² .

(10) The process for producing a biodegradable cellulose acetate foam according to the above (8) or (9), wherein the plasticizer is a polyalkylene glycol.

(11) The plasticizer has a molecular weight of 200 to 200
The method for producing a cellulose acetate biodegradable foam according to the above (10), which is a polyalkylene glycol of 00.

(12) The method for producing a biodegradable cellulose acetate foam according to any one of the above (8) to (11), wherein the foam nucleating agent is talc.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the foam of the present invention, cellulose acetate is used as a biodegradable material. That cellulose acetate has biodegradability,
It has been reported and demonstrated in various studies (CM Buchanan
et al., J. Appl. Polym. Sci., 47, 1709 (1993); ibid., 5
0, 1739 (1993); Ji-Dong Gu et al., J. Environ.Polym.De
gradation, 1 (2), 143 (1993)). Regarding the foam of the biodegradable cellulose acetate of the present invention, the foam has a foam cell diameter of 0.001 to 0.8 mm and an apparent density of 0.01 to 0.27 g / cm ³ regardless of the shape of the foam. It is necessary to have Here, the foam cell diameter and the apparent density are measured as follows.

Foam Cell Diameter The foam obtained was cut with a razor, and the cut surface was taken with a microscope to take an enlarged photograph. The cell diameters at 10 points were measured at random, and the average value was calculated.

Apparent density The foam obtained in the form of a strand was cut into a column having a length of 1 cm, the diameter was measured to determine the volume, and the weight was divided to determine the density.

Only when the foam cell diameter is 0.001 to 0.8 mm and the apparent density is 0.01 to 0.27 g / cm ^3, preferably 0.014 to 0.064 g / cm ³ , Not only the mechanical properties (tensile strength, tear strength, compressive strength, etc.) but also hardness and rigidity suitable for various uses such as cushioning materials, heat insulating materials and fillers. In addition, the above-mentioned properties of the foam are important for retaining the released acetic acid described below in the foam to maintain the antibacterial action.

More importantly, in the cellulose acetate biodegradable foam of the present invention, acetic acid liberated from cellulose acetate remains in the foam.

Here, the amount of liberated acetic acid is measured as follows.・ Amount of released acetic acid 10 g of a foam sample is sealed in a 500 cc closed container and left for 24 hours at a temperature of 20 ° C. and a relative humidity of 65%, and the amount of acetic acid in the air in the container is detected. Was measured by

The amount of acetic acid released from the cellulose acetate remaining in the foam is preferably 3 ppm or more in the above-mentioned measuring method, from the viewpoint of antibacterial action.

The generated acetic acid is present in the foam, but is discharged outside without staying inside the cell because the cells of the obtained foam are open cells. Also, because the foam cell diameter is as small as 0.001 to 0.8 mm as described above,
Without releasing at once, gradually release a moderate amount,
Long lasting antibacterial effect.

The acetic acid released in the foam remains.
The method for producing the foam will be described later in detail, under the following conditions. That is, acetyl groups remain in the cellulose acetate molecule, but when performing melt extrusion with water as a foaming agent, pressurization in a melt extruder,
Under heating conditions, cellulose acetate and water are kneaded,
Hydrolysis occurs, and some acetyl groups in the cellulose acetate molecule are cleaved to produce acetic acid. However, the amount of acetic acid generated is on the order of ppm, does not affect the degree of acetylation of the original cellulose acetate, and does not change its properties. For that purpose, the blending ratio of the foaming agent, the melting temperature and the discharge shear rate are important.

[0028] The cellulose acetate biodegradable foam of the present invention may be in any form as long as it has the above-mentioned properties, but is preferably in the form of particles, sheets, or a molded article thereof. In the case of particulate foam, the diameter of the foam is 3-200
In mm, the ratio (exposure rate) of the total surface area to the surface area of the portion where the expanded cell having an expanded cell diameter of 0.1 mm or more is exposed on the surface of the expanded particle preferably satisfies the following expression. . Foam cell exposed part surface area / total surface area ≦ 1 / (2 + 4 (long axis / short axis)) Here, the exposure ratio is measured as follows.

Exposure ratio With respect to the foam particles cut by the cutting device, the area of the portion where the foam cell having a diameter of 0.1 mm or more is exposed is determined with a microscope, and the area is divided by the total surface area of the foam particles. Calculated.

When the particle diameter of the particulate foam is smaller than 3 mm, it takes time and effort to form a molded article from the foam.
Not only is it costly, but the resulting molded article is inferior in buffer characteristics, which is not preferable. On the other hand, if the particle diameter is larger than 200 m, the handleability is poor, which is not preferable.

Further, if the exposure ratio is larger than the above formula, the proportion of the cut portion of the foamed cell becomes too large, so that fine powder falls off and adversely affects the enclosed product. The foam particles themselves can be used as a buffer, a thermal insulator, a filler. In addition, the foam particles can be used as a molded product by being packed in a mold having an arbitrary shape and shaped. There is no particular limitation on the method of packing and shaping in a mold, and any method can be adopted. For example, the foam particles may be shaped by heat fusion, or the foam particles may be adhered to each other using a binder and shaped. When a binder is used, a solution obtained by dissolving the binder in an appropriate solvent such as water or alcohol is attached to the surface to such an extent that the solution does not penetrate into the interior of the foam particles, and then the solvent is evaporated to form a solution between the foam particles. May be adhered. Alternatively, a heat-fusible resin may be adhered and adhered by heat treatment during shaping. When a solvent is used, water is more preferable in consideration of the environment.

When the cellulose acetate biodegradable foam of the present invention is a sheet-like foam, it is a wrinkled foam sheet having a thickness t of 1 to 50 mm and a wrinkle height h of 2 to 1
It is preferable that 0 mm and wrinkle interval w be 2 to 10 mm. FIG. 1 is an enlarged partial view of a wrinkled foam sheet and is a schematic diagram of a vertical cross section. T, h, w in the figure are the thickness of the sheet,
Indicates the height and spacing of wrinkles.

If the thickness of the sheet is smaller than 1 mm, it is not preferable because it takes time and cost to prepare a molded article from the foam, and also the obtained molded article has poor buffer characteristics. Further, if the thickness of the sheet is larger than 50 mm, it is not preferable because the handleability is poor.

When the height h of the wrinkles is smaller than 2 mm, the elongation at the time of molding becomes small, and tearing occurs. Also, 10
If it is larger than mm, the gap is too large to be absorbed during vacuum forming, and even in the case of press forming, a plurality of wrinkles are not uniformly expanded but only a specific portion is expanded, so that breakage is likely to occur.

When the wrinkle interval w is smaller than 2 mm, the bent portion is weakened, and it is easy to break during molding. On the other hand, if it exceeds 10 mm, the number of wrinkles contributing to elongation decreases, and tearing is likely to occur.

The shape of the wrinkles can be adjusted by appropriately setting the amount of water added to the raw material, the amount of resin discharged from the die, and the width of the discharge opening of the die. However, water can be used as a foaming agent. is important. That is, the foamed sheet discharged from the die is rapidly cooled and solidified by the latent heat of vaporization of water, so that the spread of the sheet in the width direction due to foaming is suppressed, and wrinkles can be formed. The formed wrinkles are extremely useful in forming a sheet.
That is, the sheet obtained by extrusion foaming has insufficient flexibility to be formed into a deep drawn cup shape as it is, but by forming wrinkles, the wrinkles are elongated at the time of molding, and the flexibility is increased. And a deep drawn cup-shaped molded product can be obtained.

By treating the wrinkled foam sheet with a heating roller, it is possible to obtain a cellulose acetate foam sheet having no wrinkles, improved appearance, dimensional stability, and improved tensile strength. . This sheet has a thickness of 0.5 to 25 mm and a tensile strength of 110 to 900 in the longitudinal and transverse directions, respectively.
g / cm, preferably 30 to 220 g / cm. Such characteristics can be obtained by subjecting the wrinkled foam sheet to a heat treatment at a temperature of 100 to 150 ° C. and a surface pressure of 5 to 40 kgf / cm ² .

In the above-mentioned method of forming a sheet having wrinkles or a sheet having no wrinkles, a method of forming a sheet can be generally used, that is, vacuum forming, pressure forming, press forming, etc. In some cases, it is preferable that the sheet be formed by press molding because air leakage easily occurs and the sheet itself easily transmits air.

Hereinafter, the method for producing the cellulose acetate biodegradable foam of the present invention will be described in detail. FIG. 2 shows a schematic production flow sheet. In the cellulose acetate constituting the foam of the present invention, the degree of acetic acid esterification is 45% or more in terms of the degree of acetylation expressed by the weight ratio of acetic acid bonded to cellulose, and particularly, the degree of acetylation is 47 to 60%. (The number of bound acetyl groups per unit of cellulose is 1.9 to 2.
8) is preferred. If the acetylation degree is less than 45%, the melting temperature is too high, and it is difficult to stably melt-mold the foam particles.

The above-mentioned cellulose acetate may be blended with other substances as long as the object of the present invention is not impaired, and examples thereof include a plasticizer, a heat stabilizer, a foam nucleating agent and a foaming aid. Among them, plasticizers include polyhydric alcohols such as polyethylene glycol, polymethylene glycol and glycerin; dimethyl phthalate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, diamine phthalate,
Phthalates such as dimethoxyethyl phthalate; Phosphates such as tributyl phosphate, triphenyl phosphate and tricresyl phosphate; Sebacates such as diethyl sebacate, dibutyl sebacate and sebacin dioctyl; dioctyl adipate and adipic acid Adipates such as butyloctyl and butylbenzyl adipate; citrates such as tributyl citrate, 2-ethylhexyl citrate, acetyltributyl citrate and acetyltrioctyl citrate; diisobutyl tartrate, butyl stearate and butyl oleate , Soybean oil,
Castor oil, camphor and the like can be exemplified, but it is particularly preferable to use a polyalkylene glycol having a molecular weight of 20,000 or less. When a polyalkylene glycol having a molecular weight of more than 20,000 is used, plasticization is not sufficiently performed. These plasticizers may be used alone or in combination of two or more such as polyalkylene glycol and glycerin.

When these plasticizers are added, the amount is not more than 80 parts by weight based on the weight of cellulose acetate.
Preferably, it is 50 parts by weight or less. When the amount exceeds 80 parts by weight, the shrinkage after extrusion foaming becomes large, and the foam does not foam to a desired density.

On the other hand, as the foaming nucleating agent, inorganic fine particles such as talc, silicon oxide, titanium oxide, magnesium oxide, aluminum oxide and calcium silicate, and organic powders such as cellulose powder, chitin, chitosan, wood powder and metal stearate. Fine particles and the like can be added. Particularly, talc can impart suitable foaming properties to the cellulose acetate, so that uniform and highly foamed foam particles can be easily obtained. Such foam nucleating agents may be used alone or in combination of two or more.

The amount of the foaming nucleating agent, foaming aid and the like to be added to cellulose acetate is appropriately in the range of 2 to 50 parts by weight, preferably 5 to 30 parts by weight, based on the weight of cellulose acetate. If the amount is less than 2 parts by weight, the effect of adding these additives will not be exhibited. For example, if the amount of the foam nucleating agent is small, uneven and coarse foam cells are likely to be formed.
If the amount is more than 0 parts by weight, secondary aggregation of these additives is liable to occur, so that uneven and coarse foamed cells are likely to be formed, and the fraction of cellulose acetate is reduced, so that foamability is also reduced.

As a raw material form, a chip in which cellulose acetate and various additives and further a water as a foaming agent are mixed, chips are first produced by melt extrusion from a mixed raw material of cellulose acetate and various additives, Any form using chips as a raw material is possible. In the case of mixed raw materials, cellulose acetate may be in the form of flakes or powder, but in the case of flakes, measures such as installing a dalmage on an extruder screw or using a twin-screw extruder to improve kneadability. It is preferable to improve it.

In order to produce a foam from the raw materials adjusted as described above, the raw materials may be extruded from a nozzle and a die using an extruder. At this time, 2 to 100 parts by weight, preferably 5 to 50 parts by weight of water as a foaming agent is added to 100 parts by weight of cellulose acetate or a mixture of cellulose acetate and additives.

As for the method of addition, a method of impregnating the raw material or a method of injecting the raw material with a pump from a vent portion between the raw material supply port and the discharge port of the extruder can be disclosed.

In the present invention, if the added amount of water is less than 2 parts by weight with respect to the raw material, the expansion ratio cannot be sufficiently increased, and the characteristics as a foam cannot be sufficiently exhibited. In addition, when the amount exceeds 100 parts by weight, when the raw material is impregnated, lumps are formed, and when the raw material is supplied from the hopper port of the extruder, a bridge is formed, so that the raw material cannot be charged properly. In addition, even if it is supplied from the vent portion, there is no effect of greatly improving the expansion ratio, but rather, a problem such as unstable discharge is likely to occur.

In the production of the foam of the present invention, it is extremely important to use water as a blowing agent. That is, since the discharged foam is rapidly cooled and solidified by the latent heat of evaporation of water, the foamed form can be maintained without shrinking. In addition, since water is used as a foaming agent, the cellulose acetate is heated and kneaded with water of the foaming agent until it is extruded, and is partially hydrolyzed to form a foam having acetic acid released from the cellulose acetate. It can be manufactured.

The extruder used for melt-kneading is as follows.
Any type of extruder capable of heating and melting and kneading cellulose acetate to which water has been added under high temperature and high pressure may be used, but a single-screw or twin-screw extruder is usually used.

In the present invention, the temperature at which the cellulose acetate foam is melt-extruded is set at 1 in the compression section.
The temperature is preferably 50 to 250 ° C, more preferably 180 to 220 ° C. When the temperature is lower than 150 ° C., the cellulose acetate does not melt. When the temperature is higher than 250 ° C., the cellulose acetate tends to be carbonized. On the other hand, in the measuring section, 120 to 220 ° C., preferably 140 to 20 ° C.
The temperature is preferably set to 0 ° C. When the temperature is lower than 120 ° C., the viscosity of the resin in the extruder becomes too high, and the ejection tends to be unstable, and the obtained foam does not liberate acetic acid sufficiently. Also, 2
If the temperature exceeds 20 ° C., the cooling of the resin by the latent heat of evaporation becomes insufficient after discharge, causing shrinkage, and lowering the foaming ratio of the finally obtained foam.

Further, the shape of the pore nozzle at the time of extrusion is round,
It may be triangular, square, rectangular, star-shaped, hollow or the like, and a sheet-like foam can be obtained by extruding it from a film or sheet manufacturing die. The melt-kneading time cannot be unconditionally set because it varies depending on the discharge amount per unit time, the melt-kneading temperature, and the like, but it is sufficient that the mixture has sufficient time to be uniformly melt-kneaded. The die temperature of the discharge section may be the same as the melt-kneading temperature, but may be lower than the temperature within a range where discharge is possible.

In the present invention, the foam cell diameter is set to 0.001.
To achieve a range of 0.8 mm to 0.8 mm, the shear rate of the discharge should be 10
It is necessary to keep it at 00 to 20000 sec ^-1 . 1
When the cell diameter is less than 000 sec ^-1 , the cell diameter exceeds 0.8 mm. When the cell diameter exceeds 20,000 sec ^-1 , clogging tends to occur at the discharge port, and a foam cannot be stably obtained.

In the present invention, when the foamed material extruded and foamed using a pore nozzle is formed into particles, when the foam is extruded from a die portion having pores, its tip comes into contact with the die discharge surface. It is preferable to cut the flat blade group rotating while using a foam cutting device arranged radially so that the blade surface is orthogonal to the rotation surface on which the flat blade group rotates. .

On the other hand, in order to produce a foamed sheet, the raw material may be extruded from a die for producing a sheet by using an extruder. In this case, the discharge opening width is preferably 0.1 to 1 mm.

In the present invention, when a wrinkled foam sheet is treated with a heating roller, the conditions are as follows:
To 150 ° C. and a surface pressure of 5 to 40 kgf / cm ² . When the temperature is lower than 100 ° C or when the surface pressure is 5k
When it is lower than gf / cm ^2, the effect of the heating roller treatment is not obtained, and when it exceeds 150 ° C. or when the surface pressure is 40 kgf / c
If it exceeds m ² , the sheet will fuse to the rollers during processing.

Further, when performing the heating roller treatment, a plurality of sheets can be stacked and processed, pressed and used as one sheet, but the number of sheets that can be stacked is 10 sheets. Up to. If the number exceeds 10, heat is not sufficiently transmitted to the inside during processing, and the sheets cannot be pressed. There is no particular limitation on the processing speed, but in consideration of the ease of handling the sheet after the heat treatment in the process, 1 to 10 m / min, preferably 2 to 5 m / min.
Good minutes.

[0057]

According to the present invention, it is possible to provide a cellulose acetate foam having excellent biodegradability and antibacterial properties and also having easy incineration. Therefore, this foam can provide a biodegradable foam that can be used hygienically in applications such as heat insulating materials, cushioning materials, wall materials, sound absorbing materials, and various packaging materials, not only in a single form but also in a molded shape. Therefore it is extremely industrially valuable.

[0058]

The present invention will be described in more detail with reference to the following examples. Each evaluation item in the examples was measured according to the following method.

<Apparent Density> The foam obtained in the form of a strand was cut into a column having a length of 1 cm, the diameter was measured to determine the volume, and the weight was divided to determine the density.

<Foam Cell Diameter> The obtained foam was cut with a razor, and the cut surface was photographed with a microscope to obtain an enlarged photograph. Ten cell diameters were measured at random and the average value was calculated. .

<Amount of acetic acid> 10 g of a foam sample was sealed in a closed container having a capacity of 500 cc and the amount of acetic acid in the air in the container after leaving the container at a temperature of 20 ° C and a relative humidity of 65% for 24 hours was determined. It was measured with a detector tube.

<Exposure ratio> With respect to the foam particles cut by the cutting device, the area of the portion where the foam cell having a diameter of 0.1 mm or more is exposed is determined by a microscope, and the area is divided by the total surface area of the foam particles. Was calculated.

<Expansion Ratio> The obtained sheet was cut into 5 cm squares, its thickness and weight were measured to calculate the density, and the resulting value was divided by the density of the raw material to obtain the expansion ratio.

<Formability> Using a mold having a diameter of 5 cm and a depth of 10 cm, a foam sheet previously heated in an atmosphere at 100 ° C. was press-molded. The same test was repeated 30 times, and when the rate of occurrence of tear was less than 20%, 、, 20%
The case of not less than 50% was evaluated as Δ, and the case of 50% or more was evaluated as x.

[Examples 1 to 25, Comparative Examples 1 to 11] Cellulose acetate (acetone acetate flakes manufactured by Teijin), polyethylene glycol (PEG manufactured by NOF Corporation), talc (LMR-200 manufactured by Fuji Talc Kogyo), and water were added to Table 1.
Was melted and kneaded using a twin-screw extruder (BT-30-S2 manufactured by Plastics Engineering Laboratory) and extruded from a nozzle having a diameter of 1.5 mm. At that time, a cutting device was installed at the nozzle discharge port, and the discharged foam was cut to obtain a particulate foam. The cutting device is composed of 36 blades of 0.3 mm in thickness, which are made of spring steel plate, are arranged on the holder at equal pitches, and the tip is drawn with a locus of φ220 mm.
800r. p. m. The obtained results are summarized in Tables 1 and 2.

[0066]

[Table 1]

[0067]

[Table 2]

Note) The crosses in Tables 1 and 2 indicate components outside the scope of the present invention.

[Examples 26 to 32, Comparative Examples 12 to 17]
Using the cellulose acetate, polyethylene glycol and talc in Example 4, mixed with water at the ratio shown in Table 3, and a twin screw extruder (OTE57-II manufactured by Osaka Seiki Co., Ltd.)
Melt and plasticize at 210 ° C. with a width of 5 at 200 ° C.
An extruded foam sheet was obtained from a 00 mm die. The moldability of the obtained foamed sheet was evaluated. Table 3 summarizes the obtained results.

[0070]

[Table 3]

Examples 33 to 46, Comparative Examples 18 to 21
The cellulose acetate foam sheet of Example 28 was replaced with 40
1 with a square dot pattern of mesh and 120 μm depth
A 50 mmφ metal roller and an NBR roller having a hardness of A 75 degrees were pressed together to obtain a high-strength foam sheet. Table 4 summarizes the obtained results.

[0072]

[Table 4]

[Brief description of the drawings]

FIG. 1 is an enlarged partial view of a foam sheet, which is an embodiment of a foam of the present invention, and is a schematic diagram of a longitudinal section.

FIG. 2 is a schematic flow sheet showing a method for producing a foam of the present invention.

[Explanation of symbols]

 t Foam sheet thickness h Foam sheet wrinkle height w Foam sheet wrinkle spacing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Torukei Matsui 3-4-1, Amihara, Ibaraki-shi, Osaka Teijin Limited Osaka Research Center (72) Inventor Trunkiku Nakanishi 789, Miyakazo, Shimizu-shi, Shizuoka Address Suzuki Sogyo Co., Ltd.

Claims (12)

[Claims] 1. A cellulose acetate biodegradable foam having a foam cell diameter of 0.001 to 0.8 mm, an apparent density of 0.01 to 0.27 g / cm ³ , and a cellulose acetate. A cellulose acetate biodegradable foam comprising more liberated acetic acid. 2. A 10 g foam sample is sealed in a closed container having a capacity of 500 cc and left for 24 hours at a temperature of 20 ° C. and a relative humidity of 65%, after which the amount of acetic acid in the air in the container is 3 ppm. The cellulose acetate biodegradable foam according to claim 1, which is the above. 3. The ratio of the total surface area of the foam to foamed particles having a diameter of 3 to 200 mm and the surface area of a portion where the foamed cells having a diameter of 0.1 mm or more are exposed on the surface of the particles. The cellulose acetate biodegradable foam according to claim 1, wherein the following formula is satisfied. (Surface area of exposed part of foam cell / total surface area) ≦ 1 / (2 + 4 × (long axis / short axis)) 4. The foam is a wrinkled foam sheet having a thickness of 1 to 50 mm and a wrinkle height h of 2 to 10 mm,
The cellulose acetate biodegradable foam according to claim 1, wherein a wrinkle interval w is 2 to 10 mm. 5. A foamed sheet having a thickness of 0.5 to 25 mm and having no wrinkles on its surface, and has tensile strengths of 110 to 900 g / cm and 30 to 300 g / cm, respectively in a longitudinal direction and a transverse direction.
The cellulose acetate biodegradable foam according to claim 1, which has a weight of from 220 g / cm to 220 g / cm. 6. A cellulose acetate biodegradable foam formed by integrally forming the foamed particles according to claim 3 with a binder. 7. A cellulose acetate biodegradable foam obtained by thermally shaping the foam sheet according to claim 4. 8. A composition comprising a cellulose acetate (A), a plasticizer (B) and a foam nucleating agent (C), wherein (A):
The compounding weight ratio of (B) :( C) is (100) :( 0-8
0): Water (E) as a foaming agent was mixed with the mixed raw material (D) of (2 to 50) at a blending weight ratio of 2 to 100 with respect to (D), and the mixture (F) was melted. In producing a foam by extrusion, after melting at a temperature of 150 to 250 ° C., weighing at a temperature of 120 to 220 ° C., and then shearing at a rate of 1000 to 1000
A method for producing a cellulose acetate biodegradable foam, comprising extruding at 20,000 sec ^-1 . 9. A composition comprising a cellulose acetate (A), a plasticizer (B) and a foam nucleating agent (C), wherein (A):
The compounding weight ratio of (B) :( C) is (100) :( 0-8
0): Water (E) as a foaming agent was mixed with the mixed raw material (D) of (2 to 50) at a blending weight ratio of 2 to 100 with respect to (D), and the mixture (F) was melted. Extrusion, then
A method for producing a cellulose acetate biodegradable foam, which comprises heat-treating at a temperature of 100 to 150 ° C. and a surface pressure of 5 to 40 kgf / cm ² . 10. The method for producing a cellulose acetate biodegradable foam according to claim 8, wherein the plasticizer is a polyalkylene glycol. 11. The method for producing a cellulose acetate biodegradable foam according to claim 10, wherein the plasticizer is a polyalkylene glycol having a molecular weight of 200 to 20,000. 12. The foam nucleating agent is talc.
The method for producing a cellulose acetate biodegradable foam according to any one of the first to third aspects.