JPH07108941B2 - Polycaprolactone resin molded article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molded article made from a polycaprolactone resin having an excellent biodegradability and a method for producing the same.

[Prior arts and problems to be solved by the invention]

Conventionally, there are almost no processed molded products with excellent biodegradability, and for example, films, sheets, etc. that promote the shape collapse of the molded products by partially kneading natural polymers such as cornstarch have been put on the market. There is. However, these collapsible molded articles have a concern that environmental pollution may occur because the undecomposed portion remains in the ecosystem. Polycaprolactone is known as a polymer raw material that is completely decomposed by the ecosystem. Journal of Fermentation Technology, Volume 54, No. 8 (J. Ferment.
Technol., Vol. 54, No. 8, 609-613 (1976)). Polycaprolactone is being developed for various applications by taking advantage of its biodegradation function. However, at present, polycaprolactone and molded products containing it as a main component and having excellent biodegradability have not been put on the market. Regarding the molding method of the molded product, the conventional stability and productivity-oriented molding technology is merely followed. That is,
In the molding of polycaprolactone, a method of cooling the polycaprolactone melted at a temperature higher than its melting temperature at a temperature higher than room temperature or by a cooling device using water is adopted. The biodegradability of the thus obtained molded article still has room for improvement.

Due to the above situations, even polycaprolactone, which essentially has an excellent biodegradation function, has not been sufficiently exerted, and the development of a molding method for more effective biodegradation function expression and There is a demand for the development of molded products with excellent biodegradability.

[Means for solving problems]

In view of the above circumstances, the present inventors have earnestly studied, and as a result,
The crystallinity of the polycaprolactone of the polycaprolactone resin molded product is closely related to the biodegradability, and the fact that the biodegradability is remarkably improved at a certain crystallinity or less was found, and the present invention was completed. .

That is, according to the present invention, the crystallinity of polycaprolactone is 38%.
The present invention provides a polycaprolactone resin molded article having excellent biodegradability, which is characterized by the following.

In addition, the present invention provides a polycaprolactone resin having a crystallinity of 38% after being melt-molded and rapidly solidified.
Provided is a method for producing a polycaprolactone resin molded article having excellent biodegradability, which is characterized by obtaining the following molded article.

Here, polycaprolactone in the present specification means poly-epsilon-caprolactone.
one) a homopolymer and a copolymer having a poly-epsilon-caprolactone content of 50 wt% or more, preferably 80 wt% or more, more preferably 95 wt% or more. The polycaprolactone resin means a resin containing polycaprolactone, and includes not only the resin composed of polycaprolactone described above but also a blended product thereof. In the copolymer, when the content of poly-epsilon-caprolactone becomes low, its crystallinity tends to decrease, but depending on the type of comonomer, the effect of suppressing the biodegradation function may work, so that complete decomposition From the viewpoint of the property and environmental pollution,
Higher content of epsilon-caprolactone is preferred. As the comonomer to be introduced into the copolymer, a known compound that can be copolymerized can be used without any limitation. Examples of suitable comonomer are as follows. That is, lactones such as delta-valerolactone and gamma-butyrolactone, and alcohols such as ethylene glycol, hexamethylene glycol, trimethylolpropane and glycerin.

The crystallinity of the polycaprolactone resin molded product in the present invention can be generally confirmed by methods such as an X-ray diffraction method, an infrared spectrum method, a density method, and a heat of fusion method. For example, when the crystallinity is determined by the X-ray diffraction method, the following method can be used. That is, CuKα rays are used as X-rays, and the diffraction intensity at 2θ of 6 ° to 40 ° is measured by the reflection concentration method. The crystallinity is calculated from this diffraction intensity curve by the following calculation.

Here, the area of the diffuse scattering portion means the area under a straight line connecting two points where 2θ is 6 ° and 40 °. In the crystallinity measurement by this X-ray diffraction method, the crystal orientation has a great influence on the crystallinity, so the molded product used as a measurement sample should be a non-orientated product or a finely pulverized powder product. It is necessary to be. The crystallinity obtained by the above measurement method exceeds 40% in conventional molded products,
The molded article of the present invention has a characteristic of 38% or less.

The biodegradability in the present invention means that it is completely decomposed in a natural environment such as soil, and that it is also decomposed in a partial natural environment such as a landfill, and further, urban sludge and surplus sludge of a sewage treatment plant, It means that it is decomposed by rapid composting under aerobic conditions, which is known as a method for treating pig excrement, and that it is decomposed by lipase, lipase-producing bacteria, lipase-containing substances, and the like.

Various molding methods may be used in producing the molded article of the present invention. For example, various molding methods such as extrusion molding, injection molding, blow molding, casting, vacuum molding, melt spinning, calender molding, and foam molding are used.

In producing the molded article of the present invention using the above-mentioned molding method, the most important point is that the polycaprolactone resin is melt-molded and then rapidly solidified to have a polycaprolactone crystallinity of 38.
% Or less is obtained. The quenching method and quenching temperature in this case are arbitrary as long as they give a molded product having a crystallinity of polycaprolactone of 38% or less.

In order to obtain such a molded article, the inventors of the present invention have determined that the molded article after melt molding is generally 5 ° C. or lower, particularly 0 ° C. or lower, and more preferably at a glass transition temperature of poly-epsilon-caprolactone. It has been found that a cooling device set to a temperature of -60 ° C or less can be used for rapid cooling.

Here, as the cooling device, an appropriate cooling device must be used depending on each molding method. For example, in the case of molding a film or sheet in extrusion molding, a cooling medium of 5 ° C. or lower, preferably 0 ° C. or lower A pair of or more chilled rolls that have been flowed inside to cool the roll surface to 5 ° C. or less are attached near the exit of the T die of the extrusion molding machine to rapidly cool the melt extruded from the T die. The method can be adopted. Further, the injection molding is performed by flowing a coolant into the mold and keeping the mold temperature at 5 ° C. or lower.

It is desirable that the quenching time until the molded article after melt molding is rapidly cooled to the required temperature is as short as possible.
It is 30 seconds or less, preferably 10 seconds or less. The specific quenching temperature and quenching time of the molded product after melt-molding are appropriately determined in consideration of the properties of the caprolactone resin, which is a molding raw material, and the desired biodegradation of the molded product. The crystallinity of the polycaprolactone constituting the molded product is generally specified to be 38% or less, preferably 30 to 36%.

In the present invention, a transparent molded product can be obtained by rapidly cooling the molded product after melting to a temperature of about −60 ° C. or lower which is the glass transition temperature of poly-epsilon-caprolactone. The polycaprolactone resin molded product is usually opaque, but when it is rapidly cooled to about -60 ° C or lower, a transparent molded product is obtained. It is considered that this is because the crystal particles contained in the molded product exist as fine crystals having a wavelength of visible light or less.

The polycaprolactone resin molded article in the present invention is not limited as long as it is a molded article that can be molded by the above-mentioned molding method, but it is used in a field requiring a biodegradable function. Is desirable. The following is an example of a suitably used molded product.
That is, daily commodities such as fiber film, packing, cases, bottles, disposable packaging materials such as various foam containers, greenhouse greenhouse films, surface covering films, seedling pots, strings, fertilizer bags, controlled release pesticide materials, etc. Agricultural and forestry materials, fishing nets, fishing line and other fishing materials, leisure bags, fishing bag packaging materials and other leisure products, drug delivery system materials, sutures, bone bonding materials, sanitary products and other medical materials.

〔The invention's effect〕

The technique for improving biodegradability by reducing the crystallinity disclosed in the present invention is an unexpected new fact. Therefore, the polycaprolactone resin molded article excellent in biodegradability of the present invention has a good biodegradable function, as exemplified in Examples described later, and is distinguished from conventionally known polycaprolactone molded articles. It is clear that it is This indicates that the waste treatment after use can be carried out completely, with shorter cycles and with smaller treatment area. Furthermore, the method for producing a polycaprolactone resin molded article having excellent biodegradability of the present invention is a useful method that can be used as one means for controlling the biodegradation function.

〔Example〕

Hereinafter, the effects of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 and 2 and Comparative Examples 1 and 2 (1) Preparation of Polycaprolactone Resin Sheets with Different Crystallinity Pelletized polycaprolactone (trade name: Praxel H-7, manufactured by Daicel) was put into an extruder, and T-die A sheet-shaped molded product having a thickness of about 0.5 mm was prepared. Next, a test piece of about 5 × 4 cm was cut out from this sheet. The cut-out test piece was subjected to a treatment for preventing melt loss and then held in an oven at 180 ° C. for about 10 minutes to be melted. The melt was immediately and rapidly cooled by a predetermined cooling method.

(2) Measurement of crystallinity The crystallinity of each sample prepared in (1) was measured under the following measurement conditions.

Measurement method: Reflective focusing method X-ray: CuKα (wavelength 1.54056 angstrom) Tube voltage: 50KV Conductive current: 32mA Goniometer: Wide-angle goniometer 2θ: 6 ° -40 ° Scanning speed: 2.000 ° / min Divergence slit: 1 ° Scatter slit 1 ° Measurement temperature: room temperature The crystallinity of each sample was obtained from the above-mentioned calculation formula from the obtained diffraction curve intensity. The results are shown in Table-1.
The diffraction curves of Samples A and D are shown in FIGS. 1 and 2, respectively.

(3) Measurement of biodegradability 100 mg of the sample sheet prepared in (1) was weighed into a 100 ml Erlenmeyer flask, and then 0.2 mol phosphate buffer 3 ml, 0.1
0.2 ml of wt% surfactant solution and 124.7 units of lipase from Phizopus arrhizus were added, and the total amount was made up to 15 ml with distilled water. The decomposition reaction was carried out using a rotary shaker at 30 ° C. and 180 rpm for 16 hours. After the reaction was completed, the reaction solution was filtered with quantitative filter paper (Toyo No.2), and the amount of water-soluble total organic carbon (hereinafter abbreviated as TOC) in the filtrate was measured. The difference was taken as the TOC derived from the sample decomposed by the enzyme. The decomposition rate of the sample was calculated from the TOC derived from this sample by the following calculation. The results are also shown in Table-1.

Example 3 and Comparative Example 3 (1) Preparation of Polycaprolactone Resin Sheets with Different Crystallinity Pelletized polycaprolactone (trade name: Praxel H-7, manufactured by Daicel) was put into an extruder, and about T-die was used.
A sheet-like molded product having a thickness of 0.4 mm was prepared. Next, a test piece of about 5 × 4 cm was cut out from this sheet. The cut-out test piece was subjected to a treatment for preventing melt loss and then held in an oven at 180 ° C. for about 10 minutes to be melted. The melt was immediately cooled by the prescribed cooling method.

(2) Measurement of Crystallinity The crystallinity of each sample prepared in (1) was measured according to Example 1,
The measurement was performed under the same measurement conditions as in 2 and the crystallinity was calculated. The results are shown in Table-2.

(3) Measurement of biodegradability 100 mg of the sample sheet prepared in (1) was weighed in a 100 ml Erlenmeyer flask, and then 0.2 ml of phosphate buffer 2 ml, 0.1
Add 0.5 ml of wt% surfactant solution and 32.7 units of lipase from Phizopus arrhizus, and add distilled water to make the total volume.
It was 20 ml. The decomposition reaction was carried out using a rotary shaker at 30 ° C. and 180 rpm for 16 hours. After completion of the reaction, the reaction solution is quantitatively filtered, and the amount of water-soluble total organic carbon in the filtrate (hereinafter
TOC) is measured and TOC in a system that does not use enzyme
The difference between the
It was TOC. The degradation rate of the sample is T derived from this sample.
It was calculated from OC by the following calculation.

The results are also shown in Table 2.

Example 4, Comparative Example 4 (1) Preparation of polycaprolactone resin molded product (planting pot) with different crystallinity An injection molding machine using pelletized polycaprolactone resin (trade name: Praxel H-7, manufactured by Daicel) (Sanki 6S-150), cylinder temperature 195 to 205
A pot-shaped container (thickness: about 1 mm) was molded at ℃ and resin pressure of 98 kg. During molding, the mold was cooled at two temperatures, 30 ° C. and −10 ° C., and the holding time was 90 seconds.

(2) Measurement of crystallinity A part of each molded article prepared in (1) was cooled with liquid nitrogen and then made into fine powder using a pulverizer to obtain a crystallinity measurement sample. The crystallinity was measured under the same measurement conditions as in Examples 1 and 2, and the crystallinity was calculated. The results are shown in Table-3.

(3) Measurement of biodegradability 100 mg of the molded article prepared in (1) was weighed in a 100 ml Erlenmeyer flask, and then 2 ml of 0.2 mol phosphate buffer, 0.5 ml of 0.1 wt% surfactant solution and Phizopus arrhizus Lipase
153.6 units were added, and the total amount was adjusted to 20 ml with distilled water. For the decomposition reaction, use a rotary shaker at 30 ° C,
It was carried out at 180 rpm for 20 hours. After the reaction was completed, the reaction solution was filtered with quantitative filter paper (Toyo No.2), and the amount of water-soluble total organic carbon (hereinafter abbreviated as TOC) in the filtrate was measured. The difference was taken as the TOC derived from the sample decomposed by the enzyme. The decomposition rate of the sample was calculated from the TOC derived from this sample by the following calculation.

The results are also shown in Table-3.

[Brief description of drawings]

1 and 2 show the X-ray diffraction curves of Samples A and D shown in Example 1, respectively.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Haruo Nishida, Inventor Haruo Nishi, Examiner, Ryuichi Ide, No. 40 Wadai, Tsukuba City, Ibaraki Prefecture (56) Reference JP-A-3-157450 (JP, A)

Claims (2)

[Claims] 1. A polycaprolactone resin molded article, wherein the crystallinity of polycaprolactone is 38% or less. 2. A method for producing a polycaprolactone resin molded product, which comprises melt-molding polycaprolactone, followed by rapid solidification to obtain a molded product having a polycaprolactone crystallinity of 38% or less.