JPH07268112A - Biodegradable film - Google Patents

Abstract

PURPOSE:To obtain a biodegradable film which is a film made of a polyethylene-based synthetic resin, having especially high biodegradability and readily disintegrable in a degradation medium such as soil, a wet refuse or a compost in discarding or embedding thereof. CONSTITUTION:This biodegradable film is obtained by forming a polyethylene- based synthetic resin containing 1-20wt.% organic substance having the biodegradability into a film having 10-150mum thickness and then forming uneven wrinkles or small holes on the surface of the film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is a polyethylene-based synthetic resin film, which has a particularly high biodegradability and readily disintegrates rapidly in a degrading medium such as soil, garbage, or compost during disposal or burial. It relates to a biodegradable film.

[0002]

2. Description of the Related Art Conventionally, polyethylene-based synthetic resin films have been used for various types of packaging, packaging, curing, bags, etc. due to their excellent durability as molded articles, good productivity, and low cost of raw materials. It is widely used in a large amount in all fields. However, by conversely disposing of these after use, environmental impacts on the ocean, rivers, and small animals such as birds are not small, and in recent years, there is a tendency to promote environmental conservation measures.

Therefore, a large number of so-called biodegradable resin compositions which are disintegrated by microorganisms have been announced since the early 1970s, and these resin components contain a predetermined amount of a filler which is disintegrated by microorganisms. A resin composition in which an organic substance such as starches, polysaccharides and vegetable proteins is mixed as a filler is generally used. In particular, starches have been used as suitable for imparting biodegradability to synthetic resins. For example, in JP-A-49-55740, thermoplastic synthetic resins or thermosetting elastomer resins containing starch granules. ,
JP-B-52-42187 discloses a synthetic resin containing natural starch granules and unsaturated fatty acid or its derivative.
No. 60-41089 discloses a synthetic resin in which the surface of starch granules is made to be hydrophobic, and the like.

[0004]

The above-mentioned biodegradable resin composition is molded by various methods such as extrusion molding, injection molding, calender molding, blow molding and rotational molding. As a biodegradable film, a known resin composition is used to investigate and provide a film form capable of accelerating decomposition and disintegration over time while maintaining initial strength.

[0005]

Means for Solving the Problems The first means of the present invention is, after forming a polyethylene synthetic resin containing 1 to 20% by weight of a biodegradable organic substance in a thickness of 10 to 150 μm. The biodegradable film is characterized in that uneven wrinkles are formed on the film surface. It is convenient to apply wrinkles on the surface by embossing or pressing.

As the second means, a polyethylene synthetic resin containing 1 to 20% by weight of a biodegradable organic substance was formed into a film having a thickness of 10 to 150 μm, and then a small hole penetrating the film surface was formed. It is a biodegradable film characterized by the following. It is convenient to make small holes on the film surface by punching or punching.

The polyethylene synthetic resin used in the present invention is a homopolymer of ethylene, or ethylene and propylene 1-butene, 1-hexene, which are main monomers,
It also includes those consisting of copolymers of α-olefin comonomers such as 1-octene and 4-methyl-1-pentene. High / medium density polyethylene, linear low density polyethylene by high / medium / low pressure method, super Examples thereof include low density polyethylene and low density polyethylene produced by high pressure radical polymerization.

Polyethylene synthetic resin has a melt flow rate (MFR) of 0.03 to 10 (g / 10 min.) As a basic property.
However, if the MFR is too low, high temperature moldability is required and the organic substance to be blended is liable to be poorly dispersed. On the contrary, if the MFR is too high, the film becomes thin during film formation. This is because it causes lumps and lacks rigidity.

The biodegradable organic substance to be incorporated into the polyethylene-based synthetic resin is a substance which is preferably ingested by microorganisms, and is typically starches, such as rice, corn, potato, sweet potato, wheat and the like. Obtained starch, those obtained by grafting a polymerizable monomer such as styrene to the starch, those coated with silicon, etc., and further lactose, glucose, sugars such as cellulose, sugar alcohols such as mannitol, proteins such as casein, Wood flour is also included.

It is necessary that the content of the organic substance in the polyethylene synthetic resin is 1 to 20% by weight, preferably 3 to 15% by weight. When the content is less than 1% by weight, disintegration and decomposability become insufficient. When it is more than 1% by weight, disintegration and decomposability increase as the amount increases, but when it exceeds 20% by weight, the physical properties of the film are increased. The decrease tends to be large, and at the same time, a foaming phenomenon is likely to occur and tends to be impractical in terms of both productivity and quality. Further, it is disclosed in JP-A-5-65420 and JP-A-5-345836 that the degradability is further improved by adding and blending an oxidizing oil or a metal compound in addition to the organic substance, and promoting the decomposition of these. It does not prevent the addition of the agent.

In the present invention, the thickness of the biodegradable polyethylene-based synthetic resin film is set to 10 to 150 μm, preferably 30 to 80 μm, but a film thinner than 10 μm is remarkably inferior in quality and productivity and practically used. Not the target
A film with a thickness of 10 μm or more is versatile, and by incorporating an organic substance having biodegradability, microorganisms are attracted, and the generation of cavities due to the erosion removal of the organic substance expands the decomposition reaction area, but 150 μm When it exceeds the above range, although there is erosion on the surface, it is difficult to reach the inside and the strength reduction due to deterioration does not proceed rapidly, so it can be said that the practical effect is poor.

Although it is possible to melt the polyethylene-based synthetic resin and the organic substance simply by blending them to form a film, in order to uniformly disperse the organic substance in the film, a mixing roll, a Banbury mixer, a uniaxial After melt-kneading with a known kneading device such as an extruder, a twin-screw extruder, or a kneader, it is formed into a film form by an inflation method, a T-die flat method, a calender molding method or the like. Here, in order not to make it difficult for the organic substance itself to be altered or deteriorated to induce biodegradability,
It is desirable to perform low temperature molding below ℃, preferably 200 ℃
The molding temperatures are as follows.

In addition to the above, additives such as a plasticizer, a lubricant, an ultraviolet absorber, a foaming agent, a cross-linking agent, an antistatic agent, a flame retardant, a colorant, a filler, etc. may be added without departing from the scope of the present invention. A fixed amount can be added.

The polyethylene synthetic resin film thus obtained has a large number of wrinkles or small holes formed on its entire surface by, for example, embossing or perforating. Wrinkles with a large number of irregularities, after forming a film, a metal embossing roll and a metal as a receiving roll, paper,
What is formed by pressing with a rubber roll etc. on the film surface to form irregularities in a round shape, a long shape, or a continuous pattern of these, or stripes obtained by subjecting the die lip to unevenness in advance during extrusion molding of the film It may be uneven.

Further, the embossing may be perforated by strong pressing at a point or by applying heat, or a large number of small holes may be formed by forcibly perforating with a cloth or needle. The small holes referred to here mean a state in which about 1 to 20 through holes of about 0.1 to ² mmφ are provided,
Since the deterioration rate can be adjusted by the aperture ratio, it can be an effective means, and it is preferable that a large number of small pores are distributed to secure an appropriate aperture ratio, which effectively acts to promote the deterioration. . Of course, both uneven wrinkles and small holes may be provided on the film.

[0016]

With such a structure, by placing the biodegradable film of the present invention in a decomposition medium such as soil, garbage, or compost, it is present in the decomposition medium as compared with a film having a flat surface. The film has a large surface area that enables direct and intimate contact with microorganisms, and acts to promote early disintegration as a synthetic resin film or to control the deterioration rate.

[0017]

[Examples] Descriptions will be added to the following examples.

Low density polyethylene (MFR = 2.0g /
10 min., Density = 0.923 g / cm ³ ), 45% by weight of modified starch obtained by treating the surface of cornstarch with a silane coupling agent, 6% by weight of rapeseed oil oxidised by boiling at 180 ° C. for 12 hours and aluminum sulfate 5 wt% was blended and mixed by dry blending using a Hensyl mixer. This mixture was melt-mixed by an extruder at 190 ° C. to obtain high-concentration master batch pellets.

Example 1 This masterbatch pellet was mixed with 10 wt% of low-density polyethylene (MFR = 2.0 g / 10 min., Density = 0.923 g / cm ³ ) without addition, and dry mixed, and then the screw diameter was 40 mmφ. Melt temperature by inflation method using extruder
When forming a film at 190 ° C, it is pressed at room temperature with a metal embossing roll and a rubber roll at a linear pressure of 7 kg / cm to cover the entire surface of the film surface 1 as shown in Figs.
A film having a thickness of 30 μm, in which 35 wrinkles 2 having a circular shape with a diameter of 0.3 mm were formed at 35 pieces / cm ^2, was produced, and a test piece of Example 1 was obtained. Here, the test piece of Comparative Example 1 was obtained from a similar film that was not embossed. The amount of each component in the test piece was 4.5% by weight of corn modified starch, 0.6% by weight of oxidized rapeseed oil, and 0.5% by weight of aluminum sulfate.

Example 2 Masterbatch pellets were mixed with 20 wt% of high density polyethylene (MFR = 0.03 g / 10 min., Density = 0.954 g / cm ³ ) without any additives and dry mixed, and then screw diameter 40 mmφ Melt temperature by inflation method using extruder
When forming a film at 200 ° C, use a die with circular streaks with irregularities in the die slip, as shown in Figures 2 (a) and (b).
As shown in, the entire surface of film 1 is 0.3mm with 2mm intervals.
A 50 μm-thick film having stripe-shaped wrinkles 2 having a width was produced to obtain a test piece of Example 2. Here, the test piece of Comparative Example 2 was obtained from a similar film that did not form striped wrinkles. The amount of each component in the test piece was 9% by weight of corn modified starch, 1.2% by weight of oxidized rapeseed oil, and 1% by weight of aluminum sulfate.

Example 3 This masterbatch pellet was added to an additive-free linear low density polyethylene (MFR = 1.0 g / 10 min., Density = 0.925 g / cm ³ ).
After mixing by weight and dry mixing, screw diameter 40mmφ
In forming a film having a thickness of 80 μm at a melting temperature of 200 ° C. by the T-die flat method using the extruder of FIG.
As shown in FIG. 5, Example 3-1 was one in which small holes 3 having a diameter of 0.5 mm were formed at a rate of 1 hole / cm ² . In addition, a small hole with a diameter of 0.5 mm
Formed at a rate of 10 pieces / cm ² as Example 3-2, 0.5 mm
Example 3-3 in which small holes having a diameter of 20 pieces / cm ² were formed
In Example 3-4, 0.8 mm diameter small holes were formed at a rate of 4 holes / cm ² , and in Example 3-4 1.6 mm diameter small holes were formed at a rate of 1 hole / cm ^2. A test piece was obtained as -5. Example 3-1
The aperture ratios of Examples 3-5 are shown in Table 1. Here, the test piece of Comparative Example 3 was obtained from the same film that was not perforated. The amount of each component in the test piece was 13.5% by weight of corn modified starch, 1.8% by weight of oxidized rapeseed oil, and 1.5% by weight of aluminum sulfate.

[0022]

[Table 1]

Example 4 The film having a thickness of 50 μm and having the striped wrinkles 2 obtained in Example 2 was perforated with the clothing cloth roll used in Example 3-1 to form a small hole having a diameter of 0.5 mm. A test piece was obtained as Example 4 in which 3 was formed at a rate of 1 piece / cm ² .

Evaluation of degradability Each of these test pieces was buried in forest soil, excavated 12 months later, and the oxidation start temperature was measured for each.
The test was conducted under the items of microscope FT-IR measurement and tensile strength measurement, and the results are shown below.

Measurement of Oxidation Start Temperature The measurement results of the oxidation start temperature are summarized in Table 2 as measured by DSC (differential scanning calorimeter) under the following conditions.

Measuring instrument: METTLER TA-400
0, DSC-25 Temperature rising rate: 10 ° C / min. Atmosphere: 80 ml / min. In Air

[0027]

[Table 2]

The oxidation initiation temperature is a temperature at which the oxidation of a polymer is rapidly caused, and it is known that a polymer having a low oxidation initiation temperature tends to have high decomposability. From Table 2,
It was confirmed that the degree of decrease of each test piece increased after the burying period and that the oxidative deterioration proceeded.

Microscope FT-IR measurement DIGILAB FTS-60 manufactured by Japan Bio-Rad Co., Ltd.
Absorbance at 1715 cm- ¹ (peak height) as absorption by carbonyl group produced by oxidative degradation and decomposition
Are collectively shown in Table 3 as the results of the microscope FT-IR measurement.

[0030]

[Table 3]

From Table 3, the height of the peak at 1715 cm ^-1 is increased in each test piece, and the formation of carbonyl groups is recognized, and each example shows that the deterioration progressing speed is faster than the corresponding comparative example. A remarkable effect was confirmed.

Tensile Strength Measurement Using a JIS No. 3 dumbbell as a test piece, a load cell type tensile tester was used to pull at a speed of 100 mm / min.
Tensile strength was measured under the condition of a marked line distance of 20 mm, and the residual strength ratio after the lapse of the period is shown in Table 4 as a result.

[0033]

[Table 4]

From Table 4, it can be seen that the smaller the strength residual rate is, the more the test pieces are deteriorated. Therefore, each Example is in a state in which the deterioration is further advanced by about 15 to 25% as compared with the corresponding Comparative Example. It was confirmed. Further, as compared with Examples 3-1, 3-2 and 3-3, the strength residual rate is decreased as the aperture ratio due to the small holes is increased, and further, Examples 3-2, 3-4 and 3 -5, even if the aperture ratio is the same, the strength residual ratio is lower when a large number of pores are provided. In Example 4, the film in which both the wrinkles having irregularities and the small holes are provided is The reduction rate of the strength residual rate was larger than that of the single processing, and it was confirmed that such a configuration contributes to the function of adjusting the deterioration rate.

[0035]

INDUSTRIAL APPLICABILITY As described above, the biodegradable film of the present invention has a large surface area that can be contacted with microorganisms in the decomposition medium by forming a large number of uneven wrinkles or small holes on the film surface. In comparison with the original decomposable resin composition, it has a structure more effective in promoting the reactions of disintegration, fragmentation, decomposition and reduction.

In the case where the through-holes are formed, the deterioration rate is higher when the aperture ratio occupied by the small holes having a predetermined hole diameter is larger, and when the aperture ratio is the same, the deterioration rate is higher when the hole density is larger. The resin film collapses,
This is effective in that the decomposition level can be adjusted.

Therefore, the biodegradable film of the present invention is effective in preventing environmental pollution due to its early decomposition after use, in the form of a film, tube or bag, and used in all fields such as construction, civil engineering, agriculture and daily necessities. Can be useful as a material used in.

[Brief description of drawings]

FIG. 1 shows a biodegradable film, where (a) is a plan view and (b) is an enlarged sectional view.

FIG. 2 shows another example biodegradable film,
(a) is a plan view and (b) is an enlarged sectional view.

FIG. 3 shows another example biodegradable film,
(a) is a plan view and (b) is an enlarged sectional view.

[Explanation of symbols]

 1 Film surface 2 Wrinkles 3 Small holes

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08L 3:00 89:00 97:02) (72) Inventor Takeshi Doenaga Chuo-ku, Osaka City, Osaka Prefecture 4-11 Hommachi Takenaka Corporation (72) Inventor Swim Kawaguchi 481-7 Hiyoshi-cho, Kurashiki-shi, Okayama (72) Inventor Takaaki Miyake 136-2 Hachioji-cho, Kurashiki-shi, Okayama (72) Inventor Kawashima Kiyo Osaka Prefecture Kawanishi City 2-22-3 Udaidai (72) Inventor Yoshiki Nagasawa 707-8 Kamishiro-cho, Izumi City, Osaka Prefecture

Claims (2)

[Claims] 1. An organism characterized in that a polyethylene-based synthetic resin containing 1 to 20% by weight of a biodegradable organic substance is formed into a film having a thickness of 10 to 150 μm, and then uneven wrinkles are formed on the film surface. Degradable film. 2. A polyethylene synthetic resin containing 1 to 20% by weight of a biodegradable organic substance is formed into a film having a thickness of 10 to 150 μm, and then a small hole penetrating the film surface is formed. Biodegradable film.