JP5765697B2 - Anti-adhesion material for aquatic organisms - Google Patents

Description

The present invention relates to an aquatic organism adhesion-preventing material characterized by preventing the attachment of aquatic organisms by releasing lactic acid in water.

Several methods have already been disclosed that utilize the sustained release of repellents to prevent the attachment of aquatic organisms. For example, as a method for preventing adhesion of shellfish or algae in seawater, Patent Document 1 discloses a technique for gradually releasing metal ions such as tin, zinc, and copper. There is concern that it will affect aquatic organisms. Patent Document 2 discloses a technique using a paint of an alkali preparation composition such as sodium hydroxide, but its harmfulness is a problem because of its strong alkalinity. Patent Document 3 discloses a technique using a paint containing hydrochloric acid. However, since it is a strong acid, it can affect not only other organisms such as shellfish and seaweed in seawater but also the marine environment. High nature. As described above, paints and coatings that prevent adhesion of aquatic organisms have been developed. However, the effect of controlling aquatic organisms by them is still not sufficient, and in addition, since many of these paints and coatings contain metal ions and chlorine atoms, the surrounding water due to the elution and diffusion of these paints and coatings. Contamination to the environment and general non-adherent aquatic organisms is also being pointed out.

A method using a lactic acid polymer (polylactic acid) is known as an aquatic organism adhesion preventing material that does not affect the aquatic environment and non-adherent aquatic organisms. Lactic acid polymers are known as hydrolyzable materials, and lactic acid liberated by hydrolysis is known to have antimicrobial activity. Patent Document 4 discloses a method in which a biodegradable polymer such as polylactic acid is applied as an emulsion paint to a marine product culture prop. Patent Document 5 discloses a technique for using a mixed woven yarn made of a fiber made of a lactic acid polymer composition and another synthetic fiber for an aquaculture net. Patent Document 6 discloses a technique in which an attached aquatic organism easy-release antifouling composition containing a lactic acid polymer is applied to various marine structures. However, the release rate of lactic acid from the lactic acid polymer responsible for the function of preventing adhesion has not been sufficient, and further functional improvement has been demanded.

In general, the amount of lactic acid released from high molecular weight polylactic acid is extremely small, and there is a limit to the development of antibacterial performance. In order to enhance antibacterial properties, it is necessary to release lactic acid at a high concentration. For this purpose, it is desired that the molecular weight of polylactic acid is small. On the other hand, in order to form a molded body and maintain it, it is indispensable that it is more than a specific molecular weight. In order to make such antibacterial properties and molded article maintenance characteristics compatible, for example, Patent Document 7 discloses an antibacterial composition containing 5 to 30% by weight of lactide and lactic acid oligomer up to 10-mer in high molecular weight polylactic acid. A food packaging material is disclosed. Moreover, in patent document 8, the antibacterial and antifungal fiber which contains an oligomer component 0.01 to 10weight% is proposed. However, up to now, the idea of using lactic acid oligomers that satisfy specific conditions as materials for preventing adhesion of aquatic organisms has not been proposed, focusing on lactic acid oligomers and the amount of lactic acid released.

JP 2006-247636 A JP 2006-117894 A JP 2003-96395 A JP 2002-142588 A JP 2005-273082 A JP 2005-132924 A JP 7-258526 A JP 2000-328422 A

An object of the present invention is to provide an aquatic organism adhesion-preventing material that can reduce the load of marine pollution and that can gradually release lactic acid at a concentration that provides a sufficiently excellent aquatic organism adhesion-preventing effect. is there.

The above object is achieved by each aspect of the present invention as set forth in claims 1 to 4.

The embodiment of the invention described in claim 1 is a molded body obtained from a mixture of a lactic acid oligomer having a weight average molecular weight of 50,000 or less and a thermoplastic resin, and is 168 hours (7 days) in 25 ° C. water. ) The amount of lactic acid released when immersed is in the range of 0.1 to 5.0 g / cm ² , and the thermoplastic resin is made of polyethylene, polypropylene, ethylene vinyl acetate resin, crosslinked polyethylene, and acrylonitrile butadiene styrene copolymer synthetic resin. It is an aquatic organism adhesion prevention material that is at least one selected from the group consisting of

The aspect of the invention described in claim 2 is that the mixture of the lactic acid oligomer and the thermoplastic resin contains 5 to 40 parts by weight of the lactic acid oligomer with respect to 100 parts by weight of the thermoplastic resin. The aquatic organism adhesion prevention material according to claim 1.

The aspect of the invention described in claim 3 is that the pre-lactic acid oligomer contains 90 mol% or more of L-lactic acid units, the weight average molecular weight is in the range of 2,500 to 50,000, and the melting point is 150 to 175 ° C. The aquatic organism adhesion prevention material according to claim 1 or 2, wherein the material is in a range.

The aspect of the invention described in claim 4 is that the lactic acid oligomer is produced by hydrolysis treatment of a polylactic acid (lactic acid polymer) composition. It is an anti-biological material.

According to the present invention, when a molded body obtained from a mixture of a lactic acid oligomer and a thermoplastic resin is immersed in water, an amount of lactic acid necessary for preventing adhesion of adhesive aquatic organisms is gradually released from the surface. By doing so, it is possible to avoid or prevent the adhesion of adherent aquatic organisms to the surface of the molded body without adversely affecting the environment.

The molded body in the present invention is obtained from a lactic acid oligomer having a weight average molecular weight of 50,000 or less or a mixture of the lactic acid oligomer and a thermoplastic resin, and is not limited to a molded body such as a rod or a sheet or a film. Including pellets and strands. Such a molded article of the present invention has a lactic acid release amount in the range of 0.1 to 5.0 g / cm ² when immersed in water at 25 ° C. for 168 hours (7 days). These are used alone or preferably as a mixture containing 5 to 40 parts by weight of a lactic acid oligomer with respect to 100 parts by weight of a thermoplastic resin, and molded into a molded body as an adhesion preventing material for various aquatic organisms. Is done.

The lactic acid oligomer used in the present invention has a lactic acid oligomer content of 5 to 40 parts by weight, preferably 20 to 40 parts by weight. Here, when the lactic acid oligomer content is less than 5 parts by weight, the sustained release function of the resin molded product is lowered. Further, the lactic acid oligomer preferably has a weight average molecular weight in the range of 2,000 to 50,000, and by making it within this range, a good sustained release function and mechanical properties are imparted to the resin composition. .

In the present invention, the lactic acid oligomer is an oligomer having a lactic acid ester structure as a basic unit, and in particular, the L-lactic acid ester structural unit is 90 mol% or more, preferably 95 mol% or more, more preferably 98 mol% of all units. The above polymer. Components other than L-lactic acid ester structural units include D-lactic acid ester units, lactones copolymerizable with lactide, cyclic ethers, cyclic amides, and cyclic acid anhydrides. Is possible. Suitable copolymerization components include lactones such as caprolactone, valerolactone, β-butyrolactone, and baradioxanone; cyclic ethers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, phenylglycidyl ether, oxetane, and tetrahydrofuran; cyclic amides such as ε-caprolactam; cyclic acid anhydrides such as succinic anhydride and adipic anhydride.

Furthermore, as initiator components, alcohols, glycols, glycerols, other polyhydric alcohols, carboxylic acids, polycarboxylic acids, phenols, etc. are used as units that can coexist in polylactic acid or its derivatives. It is done. Specific examples of suitably used initiator components include ethylhexyl alcohol, ethylene glycol, propylene glycol, butanediol, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, glycerin, octylic acid, lactic acid, glycolic acid and the like.

The lactic acid oligomer of the present invention preferably has a weight average molecular weight (Mw) in the range of 2,500 to 50,000, and more preferably 5,000 to 30,000. In terms of number average molecular weight (Mn), it is 1,000 to 25,000, and more preferably 2,000 to 15,000. In the case of such a range, physical properties with a balance between the release characteristics of lactic acid and moldability can be obtained. Here, the weight average molecular weight is a value obtained by multiplying each molecule by its molecular weight and taking a weighted average, and reflects the mechanical strength of the material. On the other hand, the number average molecular weight is a simple average value per molecule, and is reflected in the low molecular weight component, that is, the amount of lactic acid released. The weight average molecular weight can be determined by a method such as size exclusion chromatography (SEC (GPC)) or light scattering, and the number average molecular weight can be determined by GPC (SEC), terminal group titration, vapor pressure osmometry and osmotic pressure method. It can measure by well-known methods, such as.

In the lactic acid oligomer of the present invention, the crystallinity acts effectively in order to maintain a solid state and form a molded body. When the unit constituting the polymer has high optical purity, that is, when the L-lactic acid ester unit occupies 90 mol% or more, crystallization of the polymer is easy, but 90 mol% If it is below, crystallization may be difficult. The L-lactic acid ester unit is easily converted into a D-lactic acid ester unit which is an optical isomer by heating or the action of an alkali metal. This is an isomerization reaction called racemization. Methods for confirming the degree of racemization include nuclear magnetic resonance spectroscopy (NMR method), gas chromatography method (GC method) equipped with an optical isomer resolution column, high performance liquid chromatography method (HPLC method), thermal decomposition- Examples include gas chromatography-mass spectrometry (pyrolysis-GC / MS method). Conventionally known methods and conditions can be applied to the NMR method, GC method, HPLC method, pyrolysis-GC / MS method and the like.

In the lactic acid oligomer of the present invention, the high molecular weight polylactic acid has a melting point of about 175 ° C. and a glass transition temperature of 65 ° C., while its crystallinity and thermal transition temperature decrease with decreasing molecular weight. In particular, when the weight average molecular weight is less than 10,000, the melting point and glass transition temperature tend to decrease rapidly, the weight average molecular weight is 5,000, the melting point is about 165 ° C., the molecular weight is 2,500, and the temperature is about 150 to 155 ° C. When the molecular weight decreases, the clear melting point often disappears. Therefore, in order to maintain stable melt moldability, it is preferable to keep at least 2,500 or more in weight average molecular weight and 150 ° C. or more in melting point.

For the production of the lactic acid oligomer of the present invention, any of the conventionally known methods can be applied, but as a more suitably used method, a method of producing a high molecular weight polylactic acid by hydrolysis with water vapor is preferred. Used for To specifically illustrate this method, first, a high molecular weight polylactic acid having a weight average molecular weight of 50,000 or more is put into a heated steam reactor, and after reducing pressure and / or gas phase, steam is introduced. Since the gaseous water vapor can diffuse into any narrow space, the water vapor diffuses more effectively into the gaps between the polylactic acid molecules, and the hydrolysis proceeds quickly. It is preferable that the temperature in the container after being replaced with water vapor is 100 to 140 ° C., and the water vapor pressure is 0.10 to 0.37 MPa. In this stage, hydrolysis in a heated steam atmosphere is effective. Can be done. The molecular weight of the lactic acid oligomer produced by this heat steam decomposition can be appropriately controlled by the temperature and time of heat steam decomposition. Generally, it is carried out with a heating time of 30 minutes to 200 minutes. This lactic acid oligomer may be a recycled material. Lactic acid oligomers having different molecular weights may be mixed to have a molecular weight range.

The thermoplastic resin used in the present invention is not particularly limited, and examples thereof include polyethylene, polypropylene, ethylene vinyl acetate resin (EVA resin), crosslinked polyethylene, and acrylonitrile butadiene styrene copolymer synthetic resin (ABS resin).

Although the shaping | molding method of the molded object of this invention is not specifically limited, For example, it shape | molds by the following methods.

Under the coexistence of lactic acid oligomer and thermoplastic resin, the mixture is molded from a die, for example, as a strand, at a temperature of 140 to 180 ° C., and the molded product is cooled by air cooling. It is solidified and used as various molding materials.

The melt molding method is not particularly limited to the properties of the lactic acid oligomer, and the temperature, screw speed, amount of thermoplastic resin, and the like can be arbitrarily adjusted according to the properties of the lactic acid oligomer. Further, the batch reaction or the continuous method can be adopted for the melting reaction.

In melt molding, the temperature needs to be 140 to 180 ° C. When the molding temperature is higher than 180 ° C., the decomposition of the lactic acid oligomer is promoted and the moldability is lowered. On the other hand, when the molding temperature is lower than 140 ° C., the thermoplastic resin does not melt and molding becomes difficult.

About screw rotation speed, it carries out at 100-400 rpm. It is preferable to adjust at a screw rotational speed of 150 to 200 rpm which is not affected by local heat generation and does not decompose the lactic acid oligomer.

The melt molding time can be set arbitrarily depending on the screw rotation speed, throughput, the properties of the lactic acid oligomer, and the amount of thermoplastic resin used, but in a shorter time to prevent decomposition of the lactic acid oligomer. It is preferable to do.

Furthermore, the reaction apparatus used in the material production of the present invention is a continuous type, and a screw type extruder can be applied.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, these examples do not limit the scope of the present invention.

[Dissolution test]
As a sample for dissolution test, 100 g of pellets (diameter: 2.5 mm, length: 3 mm, single weight: 126 mg) were used. The dissolution test was performed by placing 1.0 g of a sample in 100 g of distilled water in an Erlenmeyer flask and setting the sample in a shaker at a temperature of 25 ° C. and a shaking speed of 100 rpm.

[How to find the elution amount of lactic acid (%)]
HPLC used CTO-10A to measure organic acids. Column conditions were measured at Mobil Phase (mobile phase): 0.005 NH ₂ SO ₄ , Temperature (oven temperature): 40 ° C., and 10 μl of Injection. For the calibration curve, 90 wt% lactic acid solution (Musashino Chemicals) is used, 0.01,0.02,0.04,0.08,0.10 wt% lactic acid solution is prepared, filtered using Millipore-Milliex-HP: PES 0.45 μm, and then 15 μl. Was measured by HPLC. The sample was filtered through a filter (MilliporeMilliex-HP: PES 0.45 μm), and then 15 μl of HPLC was washed with 1 ml of distilled water. Used and injected. A calibration curve was obtained from the area obtained as a result of the HPLC measurement and converted into the amount of lactic acid (wt%).

[How to find pH]
A pH meter (manufactured by HORIBA: model name = 9610) was used for measurement with a pH meter (manufactured by HORIBA: pH METER F-21). For the calibration, a phosphate buffer solution (pH 7: manufactured by Yokogawa) and an acetate buffer solution (pH 4: manufactured by Yokogawa) were used. For calibration, put about 70 ml of buffer solution in a 100 ml beaker and stir with a stirrer. In that state, insert a pH meter and let stand for about 10 minutes. After stabilization, calibrate the instrument. The above was performed at pH 7 and pH 4. For the measurement, 6 ml of a sample was collected, and 5 ml of the sample was used. A 5 ml sample was placed in a test tube and measured while stirring with a small rotor and stirrer. The indication of the end of measurement was judged using the Auto Stop function attached to the device.

[Example 1]
Pellets of lactic acid oligomer (L form = 99.1% ee, melting point = 150 to 165 ° C, Mw = 5,000) were prepared, and the amount of change in pH depending on the immersion time was shown in Table 1, and the amount of lactic acid eluted (wt%). It is shown in Table 2.

[Example 2]
Pellets of lactic acid oligomer (L-form = 99.1% ee, melting point = 150 to 165 ° C, Mw = 20,000) were prepared. The amount of pH change depending on the immersion time is shown in Table 1, and the amount of lactic acid eluted is shown in Table 2. It was.

Example 3
5 parts by weight of the same lactic acid oligomer as in Example 1 and 95 parts by weight of linear low-density polyethylene (Novatec UF840: MFI = 1.5, manufactured by Nippon Polyethylene Co., Ltd.) were put into an extruder hopper, and a twin screw was stirred at 150 rpm. And extruded as strands and cut to produce pellets. The amount of change in pH depending on the immersion time is shown in Table 1, and the amount of eluted lactic acid is shown in Table 2.

Example 4
20 parts by weight of the same lactic acid oligomer as in Example 1 and 80 parts by weight of the same linear low density polyethylene as in Example 3 were put into an extruder hopper, a twin screw was stirred at 150 rpm, extruded as a strand, cut and pelleted Was made. The amount of change in pH depending on the immersion time is shown in Table 1, and the amount of eluted lactic acid is shown in Table 2.

Example 5
20 parts by weight of the same lactic acid oligomer as in Example 2 and 80 parts by weight of the same linear low density polyethylene as in Example 3 were put into an extruder hopper, a twin screw was stirred at 150 rpm, extruded as a strand, cut and pelleted Was made. The amount of change in pH depending on the immersion time is shown in Table 1, and the amount of eluted lactic acid is shown in Table 2.

Example 6
40 parts by weight of the same lactic acid oligomer as in Example 2 and 60 parts by weight of the same linear low density polyethylene as in Example 3 were put into an extruder hopper, a twin screw was stirred at 150 rpm, extruded as a strand, cut and pelleted Was made. The amount of change in pH depending on the immersion time is shown in Table 1, and the amount of eluted lactic acid is shown in Table 2.

Example 7
20 parts by weight of the same lactic acid oligomer as in Example 2 and 80 parts by weight of EVA (ethylene vinyl acetate) resin (Mitsui DuPont Polychemical Co., Ltd. EVAFLEX EV560: MFI = 3.5) were kneaded at an open roll of 120 ° C. and then at 160 ° C. Press-molded to form a sheet.

Example 8
20 parts by weight of the same lactic acid oligomer as in Example 2 and 80 parts by weight of a linear low density polyethylene resin (Dow Chemical Japan Co., Ltd. NUCG-5130: MFI = 0.7) are kneaded at an open roll of 130 ° C. and then pressed at 160 ° C. Molded into a sheet.

[Comparative Example 1]
A pellet of lactic acid polymer (Mw = 12,000) alone was prepared. Table 1 shows the amount of change in pH depending on the immersion time using the pellets. The results of the marine immersion test used in the test of Example 9 are shown in Table 3.

From Table 1, it can be seen that in Examples 1 to 6, lactic acid was eluted immediately or at the latest by 24 hours, and the elution continued and gradually approached pH≈2 indicated by lactic acid. In the case of the lactic acid polymer of Comparative Example 1, since the pH decrease is small until at least 48 hours, it seems that the lactic acid elution amount is also suppressed, and the result is inferior in the marine immersion test of Table 3. It seems to have led to the result.

Example 9
In the marine immersion test, the samples used in the examples and comparative examples were hung with a string at the Ariake Sea Nori Farm at the Ariake Sea Research Center, Fukuoka Prefectural Fisheries and Marine Technology Center. . The period is one month. The pellet used as a sample was used by putting 100 g of each sample pelletized in a polyethylene mesh bag. The results of each immersion test are shown in Table 3.

In Examples 2, 4, and 6, no barnacles were attached. In Comparative Example 1, it was confirmed that 100 or more barnacles adhered. As a result, it can be said that the aquatic organism adhesion preventing material of the present invention is clearly superior to the material using polylactic acid.

The molded product of the present invention obtained from a mixture of a lactic acid oligomer and a thermoplastic resin generates and elutes lactic acid by a sustained release reaction that gradually releases from the surface when lactic acid is eluted by dipping. Adhesion can be avoided and prevented, and its industrial significance is great.

Claims (4)

A molded body obtained from a mixture of a lactic acid oligomer having a weight average molecular weight of 50,000 or less and a thermoplastic resin, and the amount of lactic acid released when immersed in water at 25 ° C. for 168 hours (7 days) is 0.00. 1 to 5.0 g / cm ² , and the thermoplastic resin is at least one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate resin, crosslinked polyethylene and acrylonitrile butadiene styrene copolymer synthetic resin. Anti-adhesion material. The aquatic organism adhesion prevention material according to claim 1, wherein the mixture contains 5 to 40 parts by weight of a lactic acid oligomer with respect to 100 parts by weight of the thermoplastic resin. The lactic acid oligomer contains 90 mol% or more of L-lactic acid units, has a weight average molecular weight in the range of 2,500 to 50,000, and a melting point in the range of 150 to 175 ° C. Anti-aquatic organism adhesion prevention material. The aquatic organism adhesion preventive material according to any one of claims 1 to 3, wherein the lactic acid oligomer is produced by a hydrolysis treatment of a polylactic acid composition.