JPH05209073A - Porous film - Google Patents

Abstract

PURPOSE:To provide a porous film which is flexible, hardly broken during molding and handling because of its high breaking strength and ultimate elongation, and highly degradable by microorganisms, etc., in the natural environment. CONSTITUTION:The objective film comprises 100 pts.wt. aliph. polyester resin, e.g. poly-epsilon-caprolactone, and 30-500 inorg. filler, e.g. barium sulfate dispersed therein, has an open-cell structure with the maximum cell diameter of 5mum or lower and a void content of 10-70%, and has been molecularly oriented by stretching.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a porous film which is easily decomposed by microorganisms under natural conditions.

[0002]

2. Description of the Related Art Plastics typified by polyolefin resins are chemically stable, and used plastics maintain their original shape for a long time in the natural world. Also, since the density of plastics is low, the weight of plastics is relatively low. Since it is a large volume waste, its treatment has become a big social problem.

[0003] In order to solve the problem of waste disposal of plastics, organic substances such as starch have been mixed. In this method, the shape of the plastic molding tends to collapse, but the decomposition of the resin itself requires a considerable amount of time.

For this reason, in the natural world, development of plastics in which the resin itself is easily decomposed by microorganisms such as bacteria and fungi has been developed. As such a plastic, a chemically synthesized polyester resin typified by poly ε-caprolactone, polyglycolide or polylactic acid, or a microbial-produced polyester resin typified by polyhydroxybutyrate or hydroxybutyrate-hydroxyvalerate copolymer. Etc. are known.

It is also known to make the above polyester resin porous. For example, a polyester resin which has been made porous by a crystal interface peeling method (JP-A-60-137402) and an extraction method of low molecular weight components (JP-A-62-164743) has been proposed.

[0006]

However, the porous film formed by the above-described crystal interface peeling method has a high crystallinity,
Since the crystals are oriented, the breaking strength in the lengthwise direction of the film is large, but the breaking strength in the direction perpendicular thereto is weak and the film has an unbalanced mechanical strength. Further, the film has a low breaking elongation and a high crystallinity, and thus is a film that is hard and pliable. Furthermore, since the above-mentioned porous film has a high degree of crystallinity, the biodegradability is hardly improved due to the porosity, and the decomposition rate is almost the same as that of the non-porous film.

The porous film obtained by the method of extracting low molecular weight components has improved biodegradability due to porosity, but since the elongation at break and the strength at break are not sufficient, during processing or during use of the product. There is a problem that it is easily damaged.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have sufficient strength during processing and use, and when discarded in the natural world, due to microorganisms such as bacteria and fungi As a result of repeated intensive studies to obtain a film that is easily decomposed into water and carbon dioxide and has a low impact on the environment, an aliphatic polyester resin is filled with an inorganic filler such as calcium carbonate or barium sulfate and stretched. By forming pores due to interfacial peeling between the aliphatic polyester resin and the inorganic filler, the inventors succeeded in obtaining a porous film having a high decomposition rate and excellent strength, and led to the present invention. ..

That is, the present invention relates to an aliphatic polyester resin 1
00 parts by weight and 30 to 500 parts by weight of the inorganic filler dispersed in the aliphatic polyester resin, and has a network structure composed of communicating pores having a maximum pore diameter of 5 μm or less and a porosity of 10 to 70%. And is a porous film that is molecularly oriented by stretching.

As the aliphatic polyester resin used in the present invention, known polyester resins containing no aromatic ring in the molecular chain can be used without any limitation. For example, a chemically synthesized aliphatic polyester resin, an aliphatic polyester resin fermentatively synthesized by a microorganism, or a mixture thereof can be used. Examples of the chemically synthesized aliphatic polyester resin include ring-opening polymers of lactones such as poly ε-caprolactone; saturated aliphatic polyester resins composed of dibasic acid and diol such as polyethylene adipate, polyethylene azelate and polytetramethylene succinate. Unsaturated fatty acid polyester resins such as polybutene sebacate; polymers of lactic acid or glycolic acid such as polylactide, polyglycolide and copolymers thereof; a part of ester bonds of the above aliphatic polyester resins, for example, 50% or less Examples thereof include aliphatic polyester resins substituted with amide bonds, ether bonds, urethane bonds and the like. On the other hand, examples of the aliphatic polyester resin produced by a microorganism include polyhydroxybutyrate and a copolymer of hydroxybutyrate and hydroxyvalerate.

Considering the moldability when molding these resins into a film, the processability into a porous film, and the mechanical strength of the porous film, the weight average molecular weight of the aliphatic polyester resin is 10,000 or more, Preferably 40,
000 or more is suitable.

The inorganic filler used in the present invention is
Known materials can be used without any restrictions. Examples thereof include oxides, hydroxides, carbonates and sulfates of one kind of metal selected from the group consisting of Group IIA, Group IIIA, Group IVA and Group IVB of the Periodic Table. .. Specific examples of these inorganic fillers include alkaline earth metals such as calcium, magnesium, and barium as the Group IIA metal of the periodic table, and boron as the Group IIIA metal.
A metal such as aluminum, a metal of Group IVA is silicon, and a metal of Group IVB is metal such as titanium, zirconium, or hafnium.
Oxides, hydroxides, carbonates or sulfates of these metals can be used without particular limitation. More specifically, inorganic fillers that are particularly preferably used include oxides of calcium oxide, magnesium oxide, barium oxide, aluminum oxide, boron oxide, silicon oxide, titanium oxide, zirconium oxide; calcium carbonate, carbonic acid. Carbonates such as magnesium and barium carbonate; hydroxides such as magnesium hydroxide, calcium hydroxide and aluminum hydroxide; sulfates such as calcium sulfate, barium sulfate and aluminum sulfate.

These inorganic fillers are preferably used after being surface-treated with a water-repellent surface-treating agent, if necessary. Particularly when the average particle size of the inorganic filler is small, it is difficult to uniformly disperse the inorganic filler in the aliphatic polyester resin, and therefore it is preferable to perform the surface treatment. As the water repellent surface treatment agent, a siloxane surface treatment agent, a silane surface treatment agent, or the like can be preferably used. As the siloxane-based surface treatment agent, modified polysiloxanes such as amino-modified, epoxy-modified, and carboxyl-modified polysiloxanes are preferably used. As the silane-based surface treatment agent, monoalkylsilane represented by the following general formula is preferably used.

SiRX ₃ (where R is a linear alkyl group having 1 to 30 carbon atoms, preferably an alkyl group in which a part of hydrogen atoms is replaced by fluorine, for example, CF ₃ (CH ₂ ) n- (N is 1 to 2
It is an integer of 9. ) And the like are preferable, and X is preferably a halogen atom such as chlorine or bromine, an alkoxy group, an amino group and the like. The average particle diameter of the inorganic filler used in the present invention is in the range of 0.01 to 10 μm, so that a porous film having uniform pore distribution can be obtained. It is suitable for obtaining
When an inorganic filler having an average particle size of 4 μm or more is used, the inorganic filler can be easily dispersed in the aliphatic polyester resin without using the surface treatment agent.

The blending ratio of the aliphatic polyester resin and the inorganic filler in the present invention is such that the aliphatic polyester resin 1
It is necessary to select 30 to 500 parts by weight of the inorganic filler with respect to 00 parts by weight, preferably 50 to 300 parts by weight. When the amount of the inorganic filler is less than 30 parts by weight, uniform interfacial peeling does not occur between the aliphatic polyester resin and the inorganic filler, and a porous film having a uniform thickness cannot be formed. In addition, the amount of inorganic filler is 5
If it exceeds 100 parts by weight, it becomes difficult to form a film using an extruder or the like, which is not preferable.

The porosity of the porous film of the present invention is 10 to 10.
Must be 70%. When the porosity is 10% or less, the voids formed around the inorganic filler are not connected to each other, and the communication holes connecting both sides of the film are not formed. Therefore, the surface area of the film does not increase and the decomposition rate does not increase. Further, the air permeability and moisture permeability which are the characteristics of the porous film are not sufficient. On the other hand, when the porosity exceeds 70%, the mechanical strength of the film is insufficient, and problems such as film breakage and breakage during use occur in the processing step. In particular, in order to satisfy both mechanical properties and decomposability of the porous film, the porosity is preferably 25 to 65%.

The porous film of the present invention has a network structure composed of continuous pores having a maximum pore diameter of 5 μm or less (hereinafter, also referred to as Dmax), which is interfacially separated by stretching between the aliphatic polyester resin and the inorganic filler. Have The aliphatic polyester resin portion is molecularly oriented by stretching.

The thickness of the porous film of the present invention is such that it exhibits sufficient mechanical strength and sufficient flexibility.
Generally, it is preferably 0.02 to 1.5 mm.

The porous film of the present invention has air permeability because it has a communicating hole that communicates from one surface of the film to the other surface. Breathability is usually 100 to 10,0
The range of 00 seconds / 100 cc is suitable when used for the purpose described later. The air permeability has a close relationship with the porosity, and when the porosity is large, the air permeability also becomes large.

The porous film of the present invention preferably has sufficient breaking strength and breaking elongation to prevent breakage during molding and use. Breaking strength is usually
It is preferably 0.8 to 1.5 kg / mm ² , and the breaking elongation is preferably 200 to 500%. In the conventional porous film obtained by the extraction method of low molecular weight substances, such high breaking strength and breaking elongation have not been obtained, in the porous film by the crystal interface peeling method, high breaking strength in the crystal orientation direction. However, the breaking strength in the direction perpendicular to the crystal orientation direction is low, and the breaking elongation is extremely low.

Further, when the porous film of the present invention is used for applications such as clothes and sanitary materials described later, it has a sufficient flexibility, for example, a bending hardness of 0.008-.
It preferably has a suppleness of 0.02 gf · cm ² / cm.

The porous film of the present invention can be preferably produced by the following method. That is, 100 parts by weight of the aliphatic polyester resin and 30 to 500 parts by weight of the inorganic filler are mixed, then melt-formed into a film, and then stretched in at least one direction by an area ratio of 1.5 to 20 times. It can be manufactured.

The aliphatic polyester resin and the inorganic filler are
It is mixed using a known method, for example, a Henschel mixer. Next, as a method for forming a sheet, generally, an inflation molding method or an extrusion molding method using a T-die is preferably used. In the subsequent stretching process, a tenter stretching machine, an air inflation stretching machine, a mandrel stretching machine or the like is used to stretch in at least one axial direction. When biaxial stretching is carried out, a biaxial stretching method is adopted in which biaxial stretching is carried out sequentially in the machine direction and the transverse direction, or simultaneously in the machine direction and the transverse direction. The stretching conditions are generally such that the stretching temperature is room temperature or higher and the melting point of the aliphatic polyester resin or lower, and the stretching ratio is 1.3 in the longitudinal and transverse directions, respectively.
It is preferable to set it to 3.0 times in order to obtain excellent strength characteristics, moisture permeability and water pressure resistance. Further, generally, after such stretching, heat treatment or surface treatment such as corona discharge treatment can be performed.

[0024]

EFFECT OF THE INVENTION The porous film of the present invention is remarkably excellent in biodegradability as compared with a non-porous film obtained from the same composition. Specifically, the porous film of the present invention had a weight reduction rate of about 1.5 times that of a non-porous film when immersed in a degrading enzyme solution. In addition, since the porous film of the present invention has high breaking strength and breaking elongation, it is hard to break during molding and handling, and has sufficient flexibility.

Since the porous sheet of the present invention has excellent decomposability by microorganisms in nature as described above, it can be disposed of by landfill. Further, it has good workability because it has the above-mentioned excellent mechanical properties. Therefore, the porous sheet of the present invention is useful as a disposable material such as an agricultural film, a back sheet for disposable diapers, various packaging materials, simple clothing, medical sheets, medical clothing, sanitary materials and the like.

[0026]

EXAMPLES Examples will be shown below to more specifically describe the present invention, but the present invention is not limited to these examples.

The physical properties shown in Examples and Comparative Examples were measured by the following methods.

(1) Porosity Measured by a specific gravity measuring method.

Porosity = (d ₀ −d ₁ ) / d ₀ d ₀ : Specific gravity of film before porosification d ₁ : Specific gravity of film after porosification (2) Maximum pore size Measured by the methanol bubble point method.

(3) Breaking strength / breaking elongation Measured according to ASTM-882. In Table 1, MD represents the film winding direction, and TD represents the direction perpendicular to the film winding direction.

(4) Air permeability Measured according to JIS-P-8117 (Gurley air permeability).

(5) Suppleness Kato Tech Co., Ltd. pure bending tester (KES-FB)
Measure the bending hardness using 2).

(6) Evaluation of decomposition rate 3 mg of lipase enzyme was dissolved in 1 liter of 0.04 N phosphate buffer solution. A 100 mg film was immersed in this aqueous solution, and the decomposition rate was evaluated by weight reduction of the film in an oven at 37 ° C. The decomposition rate was represented by the amount of decrease (mg) of the resin component 3 hours after the start of decomposition in consideration of the filler filling amount.

The aliphatic polyester resins and surface treatment agents used in the following examples and comparative examples are as follows.

Aliphatic polyester resin PCL: polycaprolactone P (HB-HV): hydroxybutyrate and hydroxyvalerate copolymer (copolymer composition (molar ratio) 8
0:20) PBS: polytetramethylene succinate surface treatment agent siloxane-based surface treatment agent: Shin-Etsu Silicone Co., Ltd. K
PN-3504 Silane-based surface treatment agent: Shin-Etsu Silicone Co., Ltd. KBM
-7803 The surface treatment agent is 0.5 with respect to 100 parts by weight of the filler.
Parts by weight was added.

Example 1 A composition of an aliphatic polyester resin and an inorganic filler as shown in Table 1 was mixed with a super mixer for 5 minutes, and then 1
The mixture was extruded into a strand at 80 ° C. using a twin-screw extruder and then cut into pellets.

The pellets obtained were screwed to a diameter of 30 m.
Lip opening of 0.m attached to the extruder of mφ, L / D = 24.
It was extruded at 180 ° C. using a T-die having a width of 8 mm and a width of 150 mm, brought into contact with a cooling roll having a diameter of 100 mmφ in which water having a temperature of 30 ° C. circulates, and a take-up sheet-like material was obtained at 0.8 m / min. This sheet material was uniaxially stretched at a stretching ratio of 2.0 times at 50 ° C. between two pairs of heating nip rolls having different rotation speeds. Further, the uniaxially stretched film was stretched in a direction perpendicular to the uniaxially stretched direction at a stretching temperature of 50 ° C. by a tenter stretching machine so as to have a stretching ratio of 2.0 times to obtain a porous film having a thickness of 40 μm. Each of the obtained porous films had a network structure composed of communicating pores having the maximum pore diameters shown in Table 1. Table 1 shows the physical properties and degradability of the obtained porous film.

Comparative Example 1 A porous film was manufactured by the crystal interface peeling method by the following method. 50 ° C from the melting point using a T-die with a lip opening of 4 mm in which a resin with a screw diameter of 30 mmφ and L / D = 24 was mounted on a roll with a roll surface temperature of 20 ° C.
The film was formed by extrusion at a high temperature and a take-up speed of 10 m / min. The film was heat treated at a temperature 10 ° C. below its melting point to promote crystallization. Next, this film was stretched 2.0 times in the length direction between two pairs of heating nip rolls having different rotation speeds to peel off the crystal interface, and the thickness 4
A 0 μm porous film was obtained. The physical properties and degradability of the obtained porous film are also shown in Table 1.

Comparative Example 2 A porous film was prepared by the extraction method according to the following method. The low molecular weight aliphatic polyether and the aliphatic polyester resin were mixed with a super mixer. Film formation was carried out in the same manner as in the example to obtain a film having a thickness of 40 μm. Next, low molecular weight polyether was extracted from this film with acetone to obtain a porous film. The physical properties and degradability of the obtained porous film are also shown in Table 1.

[0040]

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08L 67/02 KJR 8933-4J // C08L 67:02

Claims (1)

[Claims] 1. 100 parts by weight of an aliphatic polyester resin and an inorganic filler 30 dispersed in the aliphatic polyester resin.
.About.500 parts by weight, having a network structure composed of communicating pores having a maximum pore diameter of 5 .mu.m or less, and having a porosity of 10 to 70%.
And a porous film that is molecularly oriented by stretching.