JP3336091B2 - Degradable synthetic resin sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a curing sheet used in agriculture, civil engineering, construction work, etc., and various sheets used for covering materials, leisure, etc.
Alternatively, the present invention relates to a synthetic resin sheet which rapidly disintegrates and decomposes in a decomposition medium such as compost or in air.

[0002]

2. Description of the Related Art Conventionally, a curing sheet used for agriculture, civil engineering, construction work, or the like is formed by slitting a polyolefin-based synthetic resin film into narrow widths, stretching them, arranging them densely as flat yarns, and weaving them. One or both sides of a woven fabric coated with a resin of the same material.

In recent years, as the amount of synthetic resin used has increased, the problem of environmental pollution caused by synthetic resin waste has rapidly increased, and its treatment method has become a problem. Conventionally, synthetic resin waste has been mainly incinerated and landfilled. However, in addition to problems such as deterioration of the environment due to combustion gas, reduction of landfills, and natural destruction due to scattering, social sentiment for recycling and public movement Rising, administrative intervention is occurring. Against this background, studies have been made on synthetic resins that can be destroyed and decomposed by microorganisms and light in the soil when synthetic resin wastes are buried or dumped in the soil, and synthetic resins that have already been blended with starch have been proposed. It has been put to practical use (for example, JP-A-4-173868, JP-A-5-65420).

[0004]

The above-mentioned decomposable synthetic resins include extrusion molding, injection molding, calender molding, blow molding,
It is molded into various films and containers by various molding methods such as rotational molding, but is generally limited to those that can be molded at low temperatures. It has 250 degradable organics
Heating above ℃ degrades or degrades itself, which makes it difficult to induce the decomposition of the synthetic resin, and the molding processability of the synthetic resin itself becomes inferior, such as foaming phenomenon due to gas generation and generation of eye repellent. It is. For example, if the melt extrusion temperature is as high as 280 to 320 ° C. as in the curing sheet laminating step, a sufficient decomposability effect will not be exhibited, and workability will be significantly reduced.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned drawbacks of the degradable synthetic resin. The synthetic resin is decomposed and fragmented when left for the purpose of use, and is decomposed and reduced to soil in a long period of time. Investigating the method of manufacturing the resin sheet. As a result, 1 to 15% by weight of degradable organic substances such as starch and modified starch are added to the polyolefin-based synthetic resin to obtain 18%.
A resin coating layer containing 50% by weight or more of a recycled resin material on at least one surface of a woven fabric woven using a flat yarn which is melted at a temperature of 0 to 250 ° C., preferably 200 to 230 ° C. and extruded and manufactured using warp yarns. The problem was solved by forming

The polyolefin synthetic resin used in the present invention is a homopolymer or a mutual copolymer of α-olefins such as ethylene, propylene, 1-butene and 4-methyl-1-pentene, or these α-olefins. And other comonomers, and is selected from the viewpoints of flat yarn formability, laminate processability, sufficient strength as a curing sheet, light weight, flexibility, and easy handling. Things.

The decomposable organic substance to be added to the above-mentioned polyolefin-based synthetic resin for the purpose of imparting decomposability to the flat yarn constituting the woven fabric is an organic substance that is preferably decomposed by microorganisms and is, for example, starch (cereal). Granular starch, root crop starch, and their modified starches), plant dry fine powder, and the like, to which unsaturated fatty acids and the like, which themselves are oxidatively decomposed in a natural environment and contribute to the decomposition of synthetic resins, are added. Includes things that have been added.

The amount of decomposable organic substances such as starch and modified starch added to the synthetic resin is preferably 1 to 15% by weight. 1%
If the addition amount is less, the effect of disintegration and decomposition by decomposition is extremely low and it is not suitable for this purpose.If the addition amount is more than 15%, the moldability of the flat yarn and the initial strength as a cured sheet base material are reduced. It becomes a problem.

The polyolefin-based synthetic resin and the decomposable organic compound thus compounded are formed into an amorphous film by an extruder by a T-die method or an inflation method, cooled, and slit into a width of about 10 to 20 mm. Thereafter, a flat yarn is obtained by stretching and orienting in the longitudinal direction and then heat-treating, but the melting temperature in the extrusion step needs to be 250 ° C. or lower. If the temperature is higher than this, the decomposable organic substance itself is decomposed or deteriorated, and it is difficult to induce the decomposition of the synthetic resin by microorganisms, and at the same time, the moldability deteriorates. On the other hand, when the temperature is 180 ° C. or lower, the melt viscosity generally increases, and the film-forming property is inferior. Preferred temperatures are between 200 and 230 ° C.

The decomposable flat yarn thus obtained is used as a warp yarn and woven with a sulzer loom or the like to give a woven fabric, which is subjected to resin lamination in order to impart waterproofness and strength. The melt extrusion temperature needs to be about 280 to 320 ° C. from the viewpoint of uniformity of coating and high-speed processability, and the decomposability effect due to the addition of decomposable organic substances is reduced. Therefore, in the present invention, the recycled resin raw material is used.
By forming a resin coating layer containing 50% by weight or more, the decomposability is further accelerated. Further, if necessary, 30% by weight or more of the recycled resin raw material is added to the synthetic resin used for the flat yarn to improve the decomposability.

The term "recycled resin raw material" as used herein means a resin raw material that has undergone several thermal histories at a high temperature, and includes, for example, scrap from the production, processing or assembly process of a used resin molded product or resin product And off-grade products,
After being crushed, washed, dried, passed through a screen vent type extruder and made into regenerated pellets with a pelletizer, which is a single or mixed virgin resin. Conventionally, the quality was low due to the mixing of different kinds of resins.However, for the purpose of recycling, separation and recovery of plastic waste by type has been instructed, and there is also a recycled resin raw material of relatively uniform quality. Preferably, the same or similar polyolefin-based synthetic resin is used as the main raw material.

[0012] The regenerated resin raw material becomes one in which an oxidative active site such as a carbonyl group is developed in the main chain of the polyolefin after several times of heating and cooling. This oxidation active site imparts hydrophilicity to low-density polyethylene, which is originally hydrophobic,
It not only absorbs water necessary for microbial activity, but also facilitates main chain breakage by microbial attack (oxygen reaction). In other words, the recycled resin raw material has already been added during the manufacturing process to the same effect as when an oxidizing oil agent is added as an oxidation accelerator to the resin composition. Here, unless the amount of the recycled resin material in the resin coating layer is 50% by weight or more, the effect of decomposition by microorganisms cannot be expected. When the degree of regeneration is good and the deterioration of the physical properties of the resin is small, 100% of the recycled resin can be used.

Further, if a metal salt is added to the recycled resin raw material, the decomposability is further improved. Examples of the metal salt include a metal salt of an inorganic acid and a metal salt of a higher fatty acid. Sulfuric acid, hydrochloric acid, carbonic acid, etc. as inorganic acids, carbon number as higher fatty acids
10-30 saturated or unsaturated fatty acids, iron as the metal,
Aluminum and the like are preferred. The addition amount of these metal salts is 0.
It is 1 to 30% by weight. If the addition amount of the metal salt is 0.1% by weight or more, the degradability increases as the amount increases, but if it exceeds 30% by weight, the deterioration of the moldability and the deterioration of the physical properties due to poor dispersion become extremely large, which is not practical.

In the present invention, 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, and a filler are used without departing from the gist of the present invention. Can be blended.

[0015]

The operation of the present invention has been described with the operation.
Here is a summary of the operation. Polyolefin-based synthetic resin has sufficient strength as a curing sheet, is excellent in moldability, processability, flexibility, and contains one decomposable organic material.
An appropriate decomposition time limit can be secured without lowering the initial strength by mixing up to 15%. In particular, at a melting / extrusion condition of 250 ° C. or less at the time of molding, the compound can be mixed without deterioration of the decomposable organic substance, thereby achieving the initial purpose.

The curing sheet of the present invention comprises a flat yarn cloth and a resin coating layer on at least one surface thereof. By incorporating 50% or more of a recycled resin raw material into the resin, the degradability is increased, and the physical properties are not significantly reduced. There can be no state. If necessary, a regenerated resin or a metal salt may be mixed into the flat yarn cloth or the resin coating layer to control the overall decomposability by light or microorganisms.

[0017]

[Embodiment] Hereinafter, an embodiment will be described.

High density polyethylene (HDPE, MI =
0.8 g / 10 min., Density = 0.962 g / cm ³ ), a recycled resin mainly composed of polyethylene, rice starch (particle diameter: about 1 μm) as a decomposable organic substance, and aluminum sulfate as a metal salt were mixed and mixed in predetermined amounts. Using the material as a raw material, a film is extruded from a circular die at a melting temperature of 230 ° C by the inflation method, cut into tapes, and stretched at 115 ° C, annealing temperature of 120 ° C by hot plate contact stretching method. It was stretched uniaxially at a magnification of 4.8 times to obtain a flat yarn with a fineness of 1,000 dr. Using this flat yarn as the warp yarn, a plain weaving fabric having a weaving density of 10 × 8 / inch was obtained with a sluser loom.

In forming the resin coating layer on the plain woven cloth, low density polyethylene (LDPE, MI = 8.0 g) was used as the synthetic resin.
/ 10 min., Density = 0.917 g / cm ³ ), a recycled resin mainly composed of polyethylene, and aluminum sulfate as a metal salt. 3 on each side of the sheet
A laminate coating having a thickness of 0 μm was applied to obtain a decomposable synthetic resin sheet of the present invention.

Here, the recycled resin used for the flat yarn and the laminate is manufactured as follows. Among the plastic waste such as molded products, films, sheets, and string-like materials, those containing polyethylene as the main component are sorted out, and crushed, washed, and dried by a known technique.
It is extruded from a nozzle at a melting temperature of 260 ° C. by a screen vent type extruder, cooled and formed into regenerated resin pellets by a pelletizer.

Table 1 shows the compounding ratios of the sheets NO.1, NO.2, NO.3, NO.4, and NO.5 having different compounding ratios of the raw materials and additives thus obtained. These specimens are approximately 24 in forest soil.
Buried for months.

[0022]

[Table 1]

Twenty-four months later, each test piece was dug out, and the appearance of each test piece was visually observed and observed by SEM, oxidation start temperature measurement, microscope FT-IR measurement, and tensile strength measurement. The results are shown below.

Table 2 summarizes the results of visual observation and SEM observation.

[0025]

[Table 2]

From Table 2, microcracks can be confirmed by SEM observation of sheets Nos. 1, 2, 3, 4, and 5 in which the recycled resin is mixed in the laminate at 50% by weight. Sheets Nos. 1 and 2, which had a large number of sheets, were visually observed to show a state in which the deterioration of the resin progressed due to whitening and the appearance of small holes.

Measurement of oxidation onset temperature Measured by a DSC (differential scanning calorimeter) under the following conditions,
Table 3 summarizes the measurement results of the oxidation start temperature.

Measuring machine: TA-4000, DSC-25 manufactured by Mettler Inc. Temperature rise rate: 10 ° C./min. Atmosphere: 80 ml / min. In air

[0029]

[Table 3]

The oxidation start temperature is a temperature at which oxidation of an organic material is rapidly caused, and it is known that those having a low oxidation start temperature tend to have high decomposability. From Table 3,
Since the oxidation start temperature of the low-density polyethylene single film used for lamination is 210 ° C, the oxidation start temperature of the mixture of regenerated resin with several thermal histories is low at the initial stage. After the burying period, the degree of decrease further increased, and it can be confirmed that oxidative deterioration was progressing. However, sheet No. 6 containing 30% by weight of the recycled resin was used.
No remarkable effect was observed.

Microscope FT-IR measurement DIGILAB FTS-60 manufactured by Biorad Japan
Table 4 summarizes the absorbance at 1715 cm -1 (peak height) as absorption by a carbonyl group generated by oxidative deterioration and decomposition, as a result of FT-IR microscopic measurement.

[0032]

[Table 4]

From Table 4, the height of the peak at 1715 cm- ¹ is
Each test piece increases, but a large effect is recognized when the regenerated resin is mixed at 50% by weight. Sheets Nos. 1 and 2 to which a large amount of metal salt was added were already found to have carbonyl groups formed by the melting and heating in the laminating step.

Tensile strength measurement In order to confirm whether or not the resin deterioration has progressed beyond the resin coating layer to the woven fabric, the woven fabric retains substantial strength. Using a load cell type tensile tester, measure the tensile strength under the conditions of a pulling speed of 100 mm / min., A gripping distance of 60 mm, and a marked line distance of 20 mm.
Table 5 summarizes the residual strength ratio after the lapse of the period.

[0035]

[Table 5]

From Table 5, it can be confirmed that in Nos. 1, 2, 3, and 4, the deterioration of the resin obviously extends to the inner woven fabric beyond the resin coating layer. On the other hand, in the case of No. 5, even if the resin coating layer deteriorates, the strength of the flat yarn forming the woven fabric is not reduced because the flat yarn forming the woven fabric has no decomposability. Since the strength was not significantly reduced in spite of being a sheet, it was confirmed that the inside was not affected unless the resin coating layer deteriorated.

[0037]

From the results of the above observations and measurements, the synthetic resin sheets of Nos. 1, 2, 3, and 4 satisfying the constitution of the present invention are surely deteriorating in resin, and eventually collapse and become fragments. Has been found to be a synthetic resin sheet that is decomposed and reduced in the soil, and has become a degradable synthetic resin sheet with little environmental pollution due to early decomposition after use.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-27109 (JP, A) JP-A-3-231836 (JP, A) JP-A-60-29743 (JP, A) JP-A-56-297 146754 (JP, A) JP-A-53-28643 (JP, A) JP-A-4-367455 (JP, A) JP-A-5-4311, JP-A-5-1411 (JP, A) JP-A-3-14179 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 D01F 6/46

Claims (2)

(57) [Claims] 1. A polyolefin-based synthetic resin is added with 1 to 15% by weight of a decomposable organic material such as starch or modified starch to obtain 180 to 2 parts by weight.
At least one surface of a woven fabric woven using a flat yarn, which is melted at a temperature of 50 ° C. or less and extruded and manufactured as a weft, has a carbonyl group added to a polyolefin main chain.
A degradable synthetic resin sheet comprising a resin coating layer containing 50% by weight or more of a raw polyolefin-based synthetic resin raw material . 2. A polyolefin-based synthetic resin used in the fabric woven using a flat yarn to the weft of, polyolefin
Regenerated polyolefin with carbonyl group added to the main chain
The decomposable synthetic resin sheet according to claim 1, wherein the resin is a resin containing 30% by weight or more of a synthetic resin material .