JP2006131703A - Foam and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam comprising a biodegradable resin with excellent handing property of a foaming agent and free from remaining foaming agent in the foam. <P>SOLUTION: The invention relates to the foam obtained by foaming a mixed resin comprising 100 parts by mass of the biodegradable resin and 1.0-300 parts by mass of particles of moisture absorbing material, using a supercritical fluid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a foam using a biodegradable resin and a method for producing the same.

Conventionally, the foam which consists of biodegradable resin is manufactured using water, a chemical foaming agent, and a physical foaming agent (CFC, butane, a carbon dioxide, nitrogen, etc.) as a foaming agent (for example, the following patent documents 1-1). 5).
Japanese Patent Laid-Open No. 10-152572 Japanese Patent No. 3471810 Japanese Patent No. 2609795 JP 2003-327735 A Japanese Patent Laid-Open No. 11-147743

However, when these foaming agents are used, a residue of the foaming agent remains in the foam or, for example, butane is a flammable gas, so that the handling property of the foaming agent itself is a problem.
In addition, biodegradable resins are characterized by having a property that ultimately leads to degradation by hydrolytic action. However, when moisture absorption occurs, degradation is accelerated and physical properties deteriorate within a short period of time. There is an inconvenience that it is easy.

The present invention has been made in view of the above circumstances, and is a foam made of a biodegradable resin. The foam has good handleability of the foaming agent, and no foaming agent residue remains in the foam. It aims at providing the manufacturing method.
It is also desirable to provide a foam and a method for producing the same, in which deterioration of physical properties due to moisture absorption of the biodegradable resin can be suppressed.

In order to achieve the above object, the present invention foams a mixed resin containing 100 parts by mass of a biodegradable resin and 1.0 to 300 parts by mass of a particulate hygroscopic material using a supercritical fluid. A foam is provided.
The biodegradable resin preferably contains an aliphatic polyester and / or an aliphatic-aromatic copolyester.
The supercritical fluid is preferably either nitrogen or carbon dioxide.
It is preferable that the particulate hygroscopic material is made of an inorganic compound and has an average particle size of 0.1 μm to 50 μm.
In a preferred embodiment, the foam has an expansion ratio of 1.1 to 30.

  Moreover, this invention is the method of manufacturing the foam of this invention, Comprising: The state which heat-melted the mixed resin containing 100 mass parts of biodegradable resin and 1.0-300 mass parts of particulate hygroscopic materials A step of introducing a supercritical fluid into the mixed resin, a step of cooling the mixed resin into which the supercritical fluid has been introduced to a temperature range of a melting point to a melting point + 10 ° C., and the cooled mixed resin. There is provided a method for producing a foam, comprising a step of extruding.

The foam of the present invention is a foam made of a biodegradable resin and uses a supercritical fluid as a foaming agent. Therefore, the foaming agent is easy to handle, and a residue of the foaming agent remains in the foam. Absent.
Moreover, since the foam of this invention contains a particulate hygroscopic material, the physical property degradation by the moisture absorption of biodegradable resin is suppressed.
According to the method for producing a foam of the present invention, it is possible to produce a foam that is made of a biodegradable resin, has good handleability of the foaming agent, and does not leave a foaming agent residue in the foam.
Moreover, according to the manufacturing method of the foam of this invention, the foam which contains a particulate hygroscopic material and can suppress the physical-property deterioration by moisture absorption of biodegradable resin can be manufactured.

<Biodegradable resin>
The biodegradable resin composition in the present invention is selected from known biodegradable resins such as aliphatic polyester resins, aliphatic-aromatic copolyesters, polybutylene succinates, polybutylene adipates, polylactic acid, and polycaprolactone. 1 type (s) or 2 or more types can be used. These biodegradable resins are available as commercial products. Among them, it is preferable to contain at least an aliphatic polyester and / or an aliphatic-aromatic copolyester. In particular, aliphatic polyester resins, aliphatic-aromatic copolyesters, or mixtures of aliphatic polyester resins and aliphatic-aromatic copolyesters are suitable. Further, a polylactic acid-based resin (for example, Lacia H440, Lacia H100, Lacia H280, M-151SQ52, all manufactured by Mitsui Chemicals, Inc.) may be further contained with these mixtures as the main components.

Specific examples of the aliphatic polyester resin include Bionore # 1001, Bionore # 3001, Bionore # 1903, Bionore # 3903, Bionore 2001G, Bionore 5001G (all trade names, Showa Polymer Co., Ltd.) and the like.
Specific examples of the aliphatic-aromatic copolyester include ECOFLEX (trade name, manufactured by BASF).

<Particulate hygroscopic material>
As the particulate hygroscopic material in the present invention, a hygroscopic inorganic compound is preferably used. Specific examples include silica gel, allophane, bentonite, zeolite, alumina silica gel, calcium chloride, magnesium chloride, calcium oxide, magnesium oxide, strontium oxide, barium oxide, and a mixture of magnesium oxide and magnesium chloride.
Among these, silica gel, bentonite, calcium oxide, and magnesium oxide are preferable in terms of mixing and dispersibility in the biodegradable resin.
The average particle diameter of the particulate hygroscopic material is preferably 0.1 μm to 50 μm, and more preferably 0.5 to 20 μm. When the average particle diameter of the particulate hygroscopic material is within the above range, it is preferable in terms of foamability and physical properties of the foam.

In the present invention, the particulate hygroscopic material acts as a hygroscopic agent that suppresses deterioration of physical properties due to moisture absorption of the biodegradable resin by being present in the foam made of the biodegradable resin, and also foams a supercritical fluid. When forming a foam as an agent, it acts as a nucleating agent for forming foam cells.
The usage-amount of a particulate hygroscopic material is suitably set by the performance etc. which are requested | required in the range of 1.0-300 mass parts with respect to 100 mass parts of biodegradable resin. As the amount of the particulate hygroscopic material used increases, the hygroscopic performance improves, but if too much, the flexibility of the foam tends to decrease. Accordingly, the amount of the particulate hygroscopic material used with respect to 100 parts by mass of the biodegradable resin is preferably 1.0 part by mass or more and 50 parts by mass or less when importance is attached to the flexibility of the foam. About 2-30 mass parts is more preferable, More preferably, it is 2.0-20 mass parts. When the amount is less than the lower limit of the above range, a sufficient effect as a nucleating agent cannot be obtained, and the hygroscopic performance is inferior.
On the other hand, when emphasizing the hygroscopic performance of the foam, it is preferably more than 50 parts by mass and less than 300 parts by mass. The range of the more preferable usage-amount is 100-250 mass parts, More preferably, it is 150-200 mass parts. Exceeding the upper limit of the above range not only makes molding difficult, but also results in a relatively low content of the biodegradable resin, resulting in poor cushioning effect and flexibility as a foam.

<Manufacturing method>
FIG. 1 is a schematic configuration diagram showing an example of an extrusion molding machine suitably used in the method for producing a foam of the present invention. The extrusion molding machine in this example is configured so that a first stage extruder 1 and a second stage extruder 2 are connected, and a supercritical fluid is injected in the middle of the first stage extruder 1. ing. Reference numeral 3 in the figure indicates a supercritical fluid injection part. A die 6 is connected to the outlet of the second stage extruder 2. Although not shown, the second-stage extruder 2 is provided with a cooling means for cooling the inside. It is also possible to employ a configuration in which the second stage extruder is not provided and the first stage extruder is used for cooling.
Reference numeral 4 in the figure denotes a connecting portion (referred to as a first connecting portion) between the first-stage extruder 1 and the second-stage extruder 2, and 5 denotes a connecting portion between the second-stage extruder 2 and the die 6. (Referred to as a second connecting portion).

Hereinafter, as an embodiment of the method for producing a foam of the present invention, a method for producing a foam by an extrusion molding method using the extruder shown in FIG. 1 will be described.
First, a mixed resin containing a biodegradable resin and a particulate hygroscopic material is prepared. Preferably, a mixed resin obtained by mixing a biodegradable resin and a particulate hygroscopic material is previously formed into a pellet shape. The mixed resin can be prepared by uniformly mixing and dispersing the respective materials using a general mixing apparatus such as a biaxial kneader or a pressure kneader. The mixed resin may contain an appropriate additive as long as the effects of the present invention are not impaired.

Next, the mixed resin is charged into the first stage extruder 1 and melted by heating. Then, the supercritical fluid injection unit 3 injects the supercritical fluid into the mixed resin in the molten state.
The supercritical fluid used in the present invention is a fluid that has become a supercritical state by setting the temperature to a critical temperature or higher and a critical pressure or higher. Specifically, supercritical carbon dioxide or supercritical nitrogen is preferable.
The injection amount of the supercritical fluid can be appropriately set so as to obtain a foam having a desired expansion ratio in consideration of physical properties such as extensional viscosity and melt tension of the mixed resin.

The molten mixed resin into which the supercritical fluid has been injected is continuously sent to the second-stage extruder 2 via the first connecting portion 4, and a predetermined cooling temperature is passed through the extruder 2. Until cooled.
The cooling temperature of the mixed resin is preferably in the temperature range from the melting point to the melting point + 10 ° C., more preferably the melting point + 5 ° C. or more. By setting the cooling temperature of the mixed resin within the above range, the extension viscosity and melt tension of the mixed resin can be increased. The melting point of the mixed resin here is the melting point of the biodegradable resin used as a raw material, and when two or more kinds of biodegradable resins are used in combination, the melting point of the resin having the higher mixing ratio.
Thereafter, the cooled mixed resin is pushed out from the die 6, and the supercritical fluid in the mixed resin is decompressed to normal pressure and phase-changed to the gas phase, thereby generating foam and obtaining a foam.

The foam thus obtained has a structure in which a large number of hollow foam cells exist in the biodegradable resin layer, and at least a part of the surface of the particulate hygroscopic material is exposed in the foam cells. Have
The foam expansion ratio (specific gravity of the mixed resin before foaming / specific gravity of the foam) is preferably 1.1 or more, and more preferably 1.5 or more, since a good foamed state cannot be obtained if it is too low. The upper limit of the expansion ratio is not particularly limited, and can be appropriately set according to required characteristics such as mechanical strength. According to the present invention, a foam with a high expansion ratio of about 30 can be manufactured. it can. A more preferable range of the expansion ratio is, for example, about 1.5 to 30, and a more preferable range is about 3.0 to 20, although it depends on the use of the foam.
The shape of the foam is not particularly limited, and may be a shape that can be molded by a molding method used such as extrusion molding or injection molding. Specific examples include films, sheets, and other shaped molded bodies.

  According to the manufacturing method of the above embodiment, the supercritical fluid injected into the mixed resin containing the biodegradable resin and the particulate hygroscopic material acts as a plasticizer, and the fluidity of the mixed resin is improved. For this reason, mixing the particulate hygroscopic material prevents the fluidity of the resin from being lowered and the moldability from being deteriorated. Therefore, a foam in which deterioration of physical properties due to moisture absorption of the biodegradable resin is suppressed can be obtained by blending the particulate hygroscopic material.

In addition, since the fluidity of the mixed resin is improved by injecting the supercritical fluid as described above, even if the mixed resin before being extruded from the die 6 is cooled to the vicinity of the melting point in the second-stage extruder 2, it is good. Fluidity is obtained. That is, since the restriction of the cooling temperature of the mixed resin is relaxed, the extensional viscosity and the melt tension can be set to more preferable ranges by controlling the cooling temperature condition. Thereby, the foaming state of a foam can be controlled and the foam of a more favorable foaming state can be obtained. For example, a foam having fine foam cells, that is, a foam having a so-called micro cell, or a molded article or sheet having a large cell and a high cushioning effect by foaming can be produced.
Furthermore, the supercritical fluid used as the foaming agent has good handleability and has the advantage that no residue remains in the foam.

  The foam of the present invention can be applied to general foam materials such as cushioning materials (sheets, molded products), desiccant molded products, containers obtained by secondary processing of sheets, etc. It can be used as a desiccant. Further, since it is made of a biodegradable resin, it is biodegradable in, for example, soil or water, and can be disposed of without incineration, which is environmentally preferable.

(Examples 1-7)
A biodegradable resin and a particulate hygroscopic material were mixed with the composition shown in Table 1 to obtain a mixed resin, and the mixed resin was molded into a pellet.
-The following were used as biodegradable resins (1), (2), and (3) in Table 1, respectively.
Biodegradable resin (1): aliphatic polyester, product name: Bionore # 1903, manufactured by Showa Polymer Co., Ltd., melting point 116 ° C.
Biodegradable resin (2): Aliphatic polyester, product name: Bionore # 3903, Showa Polymer Co., Ltd., melting point 88 ° C.
Biodegradable resin (3): aliphatic-aromatic copolyester, product name: Ecoflex, manufactured by BASF, melting point 125 ° C.
The particulate hygroscopic material in the following Table 1 is calcium oxide (CaO) having an average particle diameter of 1 μm.

A sheet-like foam was formed using the mixed resin prepared above.
The molding was performed by using an extrusion molding machine having the configuration shown in FIG.
That is, the mixed resin formed into a pellet shape as described above was charged into the first-stage extruder 1 and sufficiently melted therein, and then the supercritical fluid was injected by the supercritical fluid injection unit 3. The molten mixed resin into which the supercritical fluid has been injected in the first-stage extruder 1 is continuously sent to the second-stage extruder 2 via the first connecting portion 4, cooled, and second It is extruded from the die 6 through the connecting portion 5. A foam was thus obtained.
The barrel inner diameter (portion) of the first stage extruder 1 was 65 mm, and the barrel inner diameter of the second stage extruder 2 was 75 mm.

The conditions in each example are shown in Table 1 below.
The supercritical fluid in the following Table 1 is supercritical nitrogen (described as N _{2 in the} table) or supercritical carbon dioxide (described as CO _{2 in the} table).
The resin discharge amount A in Table 1 below is a measurement result of the discharge amount (unit: kg / h) of the mixed resin discharged from the die 6 in a state where the supercritical fluid is not injected.
The supercritical fluid injection amount B in Table 1 below is a measurement result of the injection amount (unit: kg / h) of the supercritical fluid injected from the supercritical fluid injection part 3 into the first stage extruder 1.
-The injection | pouring ratio C in following Table 1 is a value (unit; mass%) calculated | required by said B / Ax100.
-As the die 6, a T die or a round die was used. The T die had a discharge port composed of a straight slit, and the discharge port had a length of 300 mm. On the other hand, the round die has a discharge port composed of an annular slit, and the discharge port has a diameter of 50 mm. When a round die was used, a cylindrical shaped product extruded from the round die was cut into a sheet shape along the length direction.
The temperature in Table 1 is a measurement result of the temperature of the mixed resin in the second connecting portion 5.

  About the obtained sheet-like foam, the thickness and expansion ratio of the sheet were measured. The results are shown in Table 1 below.

(Comparative Example 1)
In Example 2, the amount of CaO was changed to 310 parts by mass and a sheet-like foam was formed by the same extrusion molding method. However, the fluidity of the resin was too low to be molded.

(Comparative Example 2)
In Example 2, the amount of CaO was changed to 0.5 parts by mass, and a sheet-like foam was formed by the same extrusion molding method, but a good foamed state was not obtained.

It is the schematic block diagram which showed an example of the extruder suitably used for the manufacturing method of the foam of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... First stage extruder, 2 ... Second stage extruder, 3 ... Supercritical fluid injection part, 6 ... Die.

Claims (6)

  A foam obtained by foaming a mixed resin containing 100 parts by mass of a biodegradable resin and 1.0 to 300 parts by mass of a particulate hygroscopic material using a supercritical fluid.   The foam according to claim 1, wherein the biodegradable resin contains an aliphatic polyester and / or an aliphatic-aromatic copolyester.   The foam according to claim 1 or 2, wherein the supercritical fluid is either nitrogen or carbon dioxide.   The foam according to any one of claims 1 to 3, wherein the particulate hygroscopic material is made of an inorganic compound and has an average particle diameter of 0.1 µm to 50 µm.   The foam according to any one of claims 1 to 4, wherein the foam has a foaming ratio of 1.1 to 30. A method for producing the foam according to any one of claims 1 to 5,
Introducing a supercritical fluid into the mixed resin in a state where 100 parts by mass of the biodegradable resin and 1.0 to 300 parts by mass of the particulate hygroscopic material are heated and melted; A method for producing a foam, comprising: a step of cooling a mixed resin into which a fluid is introduced to a temperature range of a melting point or higher and a melting point + 10 ° C. or lower; and a step of extruding the cooled mixed resin.

Images