JP2002338796A - Biodegradable gas-barrier material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable polyester material showing an excellent gas-barrier property, especially a biodegradable polyester material showing a high gas-barrier property. SOLUTION: The biodegradable gas-barrier material is prepared by dispersing a swellable, layered silicate treated with organic onium ion in a polyester containing lactic acid as the main repeating unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biodegradable gas barrier material comprising a polyester having lactic acid as a main repeating unit.

[0002]

2. Description of the Related Art In recent years, biodegradable polymers have been actively studied in order to adapt to a recycling-oriented society. Among them, polylactic acid attracts attention not only from the viewpoint of biodegradation but also from the viewpoint of using renewable resources as a raw material in place of fossil resources such as petroleum, and from the viewpoint of comprehensive physical properties such as transparency, safety and stability. It is a new material being bathed (Plastics, Vol52, No.1, 20
01). However, polylactic acid is still insufficient in terms of gas barrier properties, which has been a technical problem common to biodegradable polymers (Plastic Age, Feb, 1999). As a method for improving the gas barrier property, there is a method of coating an organic layer containing an inorganic substance on the polymer surface (Japanese Patent Application Laid-Open No. 62-14853).
No. 2, JP-A-64-43554, JP-A-3-93542,
JP-A-7-247374). However, this method has a problem that the production process is multi-step and inefficient.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biodegradable material having excellent gas barrier properties, particularly a biodegradable polyester material having high gas barrier properties.

[0004]

Means for Solving the Problems The present inventors do not use a technique having a problem in productivity, such as coating an organic layer containing an inorganic substance on a polymer surface, and use a simple method excellent in productivity. Materials with the above properties were studied. As a result, it has been found that it is important to directly disperse an inorganic substance in polylactic acid.

Further, the present inventors have used a swellable layered silicate as such an inorganic substance and highly disperse it in a polyester having lactic acid as a main repeating component, thereby significantly improving the biodegradability and gas barrier properties of the polymer. And completed the present invention.

That is, the present invention is as follows. 1. A biodegradable gas barrier material comprising a polyester having lactic acid as a main repeating unit and a swellable layered silicate. 2. The above biodegradable gas barrier material, wherein the swellable layered silicate is treated with an organic onium ion. 3. The above biodegradable gas barrier material, wherein the organic onium ion is a quaternary ammonium ion. 4. The above biodegradable gas barrier material, wherein the quaternary ammonium ion is represented by the following formula (1).

[0007]

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(In the formula (1), R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group having 1 to 30 carbon atoms or a polyoxyalkylene oxide group.)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester having lactic acid as a main repeating unit used in the present invention means polylactic acid or a known dicarboxylic acid, diol, hydroxydicarboxylic acid or the like within a range not impairing the object of the present invention. Refers to a polyester into which a copolymer component is introduced. Polylactic acid which is a monomer of polylactic acid may contain either L-lactic acid or D-lactic acid. As the copolymer component, for example, terephthalic acid, orthophthalic acid, chlorophthalic acid,
Nitrophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid,
1,5-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenyl Sulfone dicarboxylic acid, 4,4'-diphenylisopropylidene dicarboxylic acid,
Aromatic dicarboxylic acids such as 1,2-bis (4-carboxyphenoxy) -ethane, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, suberic acid, Azelaic acid, sebacic acid, dodecanedioic acid, octadecanedicarboxylic acid, dimer acid, aliphatic dicarboxylic acids such as maleic acid and fumaric acid, dicarboxylic acids such as cycloaliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, ethylene glycol , Propylene glycol, 1,3-butanediol 1,4-butanediol, 2,2-dimethylpropanediol, neopentyl glycol, 1,5-pentadiol, 1,
6-hexanediol, 1,8-octanediol, 1,10-decanediol 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, trimethylene glycol, tetramethylene glycol, Diols such as pentamethylene glycol, octamethylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, hydroquinone, resorcinol, bisphenol A and 2,2-bis (2'-hydroxyethoxyphenyl) propane, p-hydroxybenzoic acid, p- Hydroxyethoxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4'-hydroxy-biphenyl-4-
Examples thereof include hydroxycarboxylic acids such as carboxylic acids. The amount of the copolymerized component to be introduced is not particularly limited, but is preferably small in order to maintain various physical properties of polylactic acid. It is preferably at most 0.2 mol, more preferably at most 0.1 mol, per 1 mol of the polylactic acid monomer component.

Although the degree of polymerization of the polyester is not particularly limited, it is preferable to use a polyester having a solution viscosity of 0.5 to 2.0. Although the terminal structure of the polyester is not particularly limited, chemical modification such as terminal capping may be performed as necessary. The catalyst for producing the polyester, the polymerization method, and the apparatus are not particularly limited, and known ones can be used.

[0011] The swellable layered silicate used in the present invention comprises:
It is a layered silicate having a cation exchange ability and exhibiting a property of swelling by taking in water between layers. Examples of the smectite-based clay mineral include hectorite, saponite, stevensite, beidellite, montmorillonite, natural or chemically synthesized ones thereof, and substituted, derivative, or mixtures thereof. Examples of the swellable mica include synthetic swellable mica having chemically-synthesized layers, for example, Li and Na ions, or a substituted body, a derivative or a mixture thereof.

In the present invention, it is preferable to use the swellable layered silicate treated with an organic onium ion. By this treatment, organic onium ions are inserted between the layers (planes) of the swellable layered silicate, and the distance between the layers is increased. As a method for confirming that this organic treatment has been performed, wide-angle X-ray analysis
Determining the interplanar value from the diffraction peak derived from the bottom reflection of the (001) plane may be mentioned. In addition, obtaining the organic content from the thermogravimetric change measurement is also mentioned.

Examples of the organic onium ion that can be used include a quaternary ammonium ion and an organic phosphonium ion. In this, the following formula (1)

[0014]

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A quaternary ammonium ion having the structure (1) is preferred. In the above formula (1), R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group having 1 to 30 carbon atoms or a polyalkylene oxide group. Here, the alkyl group having 1 to 30 carbon atoms is preferably an alkyl group having 1 to 18 carbon atoms. Examples of the alkylene group of the polyalkylene oxide group include an alkylene group having 2 to 4 carbon atoms such as an ethylene group.

The quaternary ammonium ion represented by the above formula (1) has three or two alkyl groups having 1 to 18 carbon atoms among R ₁ , R ₂ , R ₃ and R ₄ and is a polyalkylene. Those having one or two oxide groups are preferred in terms of dispersibility in polyester and the like. The chain length of the polyalkylene oxide group is 5 to 15 moles in terms of the number of moles added.

Specific examples of the quaternary ammonium ion include dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, oleyltrimethylammonium chloride, didodecyldimethylammonium chloride, Decyl dimethyl ammonium chloride, dihexadecyl dimethyl ammonium chloride, dioctadecyl dimethyl ammonium chloride, dioleyl dimethyl ammonium chloride dodecyl dimethyl benzyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, hexadecyl dimethyl benzyl ammonium chloride, octadecyl dimethyl chloride Jill ammonium chloride, oleyl dimethyl benzyl chloride, hydroxy polyoxyethylene dodecyl dimethyl ammonium chloride,
Hydroxy polyoxyethylene tetradecyl dimethyl ammonium chloride, hydroxy polyoxy ethylene hexadecyl dimethyl ammonium chloride, hydroxy polyoxy ethylene octadecyl dimethyl ammonium chloride, hydroxy polyoxy ethylene oleyl dimethyl ammonium chloride, dihydroxy polyoxy ethylene dodecyl methyl ammonium chloride,
Dihydroxypolyoxyethylenetetradecylmethylammonium chloride, dihydroxypolyoxyethylenehexadecylmethylammonium chloride, dihydroxypolyoxyethyleneoctadecylmethylammonium chloride, dihydroxypolyoxyethyleneoleylmethylammonium chloride, dihydroxypolyoxypropylenetetradecylmethylammonium chloride, dihydroxypoly Oxybutylenetetradecylmethylammonium chloride.

Examples of the quaternary phosphonium ion include tetraethylphosphonium bromide, triethylbenzylphosphonium chloride,
Tetra-n-butylphosphonium bromide, tetra-n-
Butylphosphonium chloride, tetra-n-butylphosphonium iodide, tetra-n-butylphosphonium-o, o-diethylphosphodithionate,
Tetra-n-butylphosphonium benzotriazolate, tri-n-butylmethylphosphonium iodide, tri-n-butyloctylphosphonium bromide, tri-n-butylhexadecylphosphonium bromide, tri- n-butylallylphosphonium bromide, tri-n-butylbenzylphosphonium chloride, tri-n-octylethylphosphonium bromide, and tetrakishydroxymethylphosphonium sulfonate.

In the method of treating the swellable phyllosilicate with organic onium ions, usually, 1 part by weight of the swellable phyllosilicate and 1 to 10 parts by weight of organic onium ions are mixed in water and then dried. The amount of water is 1 to 100 times that of the swellable phyllosilicate. The temperature at the time of mixing is 30 ° C to 70 ° C,
The mixing time is preferably 0.5 to 2 hours. As the drying conditions, drying under normal pressure at 70 to 100 ° C. for 3 days and vacuum drying for 2 days are preferable.

The thus obtained swellable phyllosilicate treated with organic onium ions has a weight ratio of organic onium ions to swellable phyllosilicate of 10: 9.
When the ratio is 0 to 40:60, the dispersibility in the polyester is good.

The proportion (content) of the swellable layered compound in the polyester in the present invention is preferably from 0.5 to 10% by weight, and particularly from 1 to 5% by weight, higher dispersibility can be obtained. Can be

As a method for dispersing the swellable layered compound in the polyester, for example, a swellable layered silicate is
Add or disperse uniformly at the time of polymerization of polyester, or melt kneading polyester, swellable layered silicate,
Alternatively, a method of dispersing by solution dispersion using a solvent can be adopted.

Whether or not these swellable layered compounds are dispersed is determined by the (00) of the swellable layered silicate measured by X-ray analysis.
1) The diffraction peak derived from the bottom reflection of the plane is shifted to a low angle of incidence, and the diffraction peak based on the plane spacing substantially disappears, that is, the state in which the plane distance is increased, the present invention. Is preferred in the sense of achieving the object of the invention.

The term "biodegradation" as used in the present invention means that it is decomposed by an aggregate (mixed state) of ordinary microorganisms represented by activated sludge and the like, and the solution viscosity of the polyester is significantly reduced. Those having a biodegradation rate of 10% or more in 3 weeks are preferred.

[0025]

According to the present invention, it is important to find that a polyester containing swellable layered silicate and containing lactic acid as a main repeating component exhibits high gas barrier properties. This is presumed to be because the swellable layered silicate is highly dispersed in the polyester having lactic acid as a main repeating component, thereby improving the gas barrier properties of the polyester. Surprisingly, the biodegradability of the polyester was also improved.

As described above, according to the present invention, a polyester composition comprising a polyester containing lactic acid as a main repeating component and a swellable layered silicate treated with an organic onium ion has high gas barrier properties and biodegradability. It is also expected to improve the mechanical strength without losing the transparency of the polyester, and thus is useful as a biodegradable gas barrier film and other materials. Examples of applications include agricultural films, seedling pots, agricultural and horticultural applications such as seed coating and horticultural ropes, sandbags and ropes,
Applications for industrial materials such as soil improvement materials, as well as food film and beverage bottles that require gas barrier properties are conceivable.

[0027]

The following examples further illustrate the details of the present invention. (1) Materials used Montmorillonite used in this example was Nanocor, and dihydroxypolyoxyethylene oleyl methyl ammonium chloride was Takemoto Yushi Co., Ltd., phenol, 1,1 ', 2,
2'-tetrachloroethane, methylene chloride, glucose,
Potassium dihydrogen phosphate and bactopeptone are from Kanto Chemical
The polylactic acid used was made by Mitsui Chemicals, Inc.

(2) Treatment of swellable phyllosilicate with quaternary ammonium ion 100 g of montmorillonite, 100 g of dihydroxypolyoxyethylene oleylmethylammonium chloride and 1 g of water
0 L was added, the mixture was stirred at room temperature for 2 hours, and a crude product was obtained by filtration. After washing three times with 10 L of water,
Drying with hot air at 3 ° C. for 3 days and vacuum drying for 2 days gave montmorillonite treated with quaternary ammonium ions. Confirmation was performed by X-ray analysis, and it was confirmed that the plane spacing changed from 12 mm to 34 mm.

The dihydroxypolyoxyethylene oleylmethylammonium chloride used had an addition mole number of 15 moles. This means that when two polyoxyethylenes are combined to form one polyoxyethylene, 15 oxyethylene units are repeated.

(3) Method of dispersing swellable layered silicate treated with quaternary ammonium ion in polylactic acid 970 g of polylactic acid, 42 g of montmorillonite (treated with quaternary ammonium ion) (3% by weight based on polylactic acid) Was melt-kneaded at 190 ° C. using a ruder (PCM-30, Ikegai Iron Works) to disperse montmorillonite in polylactic acid.

(4) Measurement of interlayer distance of swellable phyllosilicate The interlayer distance of swellable phyllosilicate was measured using a wide-angle X-ray analyzer (CN2155, Rigaku Corporation). It was determined from the diffraction peak derived from the bottom reflection of the (001) plane.

(5) Preparation of Activated Sludge Activated sludge was prepared according to the method for preparing an optimized test culture solution described in JIS K6950. This optimized test culture is highly buffered and contains many mineral nutrients. This is necessary to keep the pH of the system under test constant even at high test sample concentrations. This culture contains approximately 2,400 mg / l phosphorus and 50 mg / l nitrogen and is therefore suitable for test material concentrations up to 2000 mg / l organic carbon.

Specifically, solution A: inorganic potassium dihydrogen phosphate 37.5 g, disodium hydrogen phosphate dihydrate 8
7.3 g and ammonium chloride 2 g were dissolved in water to make a total amount of 1
Make up to 000 ml. Solution B: 22.5 g of magnesium sulfate heptahydrate is dissolved in water to make the total volume 1000 ml.
Solution C: Dissolve 36.4 g of calcium chloride dihydrate in water to make the total volume 1000 ml. D solution: iron chloride (II
I) 0.25 g of hexahydrate is dissolved in water, and the total amount is 1000
to ml. Then, 100 ml of solution A and solutions B to D
, 197 g of water, 8 g of water and 1 g of bactopeptone as a carbon source to prepare a test culture solution.

(6) Biodegradability test Polylactic acid was immersed in activated sludge at 50 ° C. for 3 weeks with aeration.

(7) Solution Viscosity Measurement Polylactic acid was dissolved in a phenol / 1,1 ', 2,2'-tetrachloroethane = 60/40 (weight ratio) solvent,
Measurements were made at ° C.

(8) Measurement of gas barrier properties According to the JIS K7129B method, the amount of water vapor permeation was measured at 40 ° C. and 90% RH. As a test device, PERMATRAN-W600
(MOCON) was used.

Example 1 3% by weight of montmorillonite
10 g of the dispersed polylactic acid was dissolved in 90 g of methylene chloride, and cast on a glass plate to a thickness of 100 μm. After casting, drying was performed at room temperature for 2 hours and at 40 ° C. for 8 hours under vacuum. Thereafter, the mixture was heat-set at 90 ° C. for 1 hour, and the dispersibility of montmorillonite in polylactic acid was evaluated by X-ray analysis. Also, 50 in activated sludge
The samples were immersed in aerated at 2 ° C for 2 weeks, subjected to a biodegradability test, and the biodegradability was evaluated based on the change in the solution viscosity of the polymer before and after immersion. Further, a water vapor permeability test was performed as a gas barrier property test.

Comparative Example 1 10 g of polylactic acid was dissolved in 90 g of methylene chloride and cast on a glass plate to a thickness of 100 μm. After casting, drying was performed at room temperature for 2 hours and at 40 ° C. for 8 hours under vacuum. Then heat set at 90 ° C for 1 hour, immerse in activated sludge at 50 ° C for 2 weeks while aerating, conduct biodegradability test, and evaluate the biodegradability by the change in polymer solution viscosity before and after immersion. went. Further, a water vapor permeability test was performed as a gas barrier property test.

[0039]

[Table 1]

[0040] * The biodegradation rate = - than (biodegradation previous η _{sp / c} η _{sp / c} after biodegradation) / (biodegradation previous eta _{sp / c)} Example 1 and Comparative Example 1, swellable layered The polylactic acid composite material obtained by dispersing silicate in polylactic acid was found to exhibit high biodegradability and gas barrier properties.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeyuki Kawaguchi 2-1 Hinode-cho, Iwakuni-shi, Yamaguchi F-term in the Teijin Iwakuni Research Center (reference) 4J002 CF181 CF191 DJ006 FA016 FB086 GA00 GA01 GA02 GG00 GG01 GG02 GL00

Claims (4)

[Claims] 1. A biodegradable gas barrier material comprising a polyester having lactic acid as a main repeating unit and a swellable phyllosilicate. 2. The biodegradable gas barrier material according to claim 1, wherein the swellable layered silicate has been treated with an organic onium ion. 3. The biodegradable gas barrier material according to claim 2, wherein the organic onium ion is a quaternary ammonium ion. 4. The biodegradable gas barrier material according to claim 3, wherein the quaternary ammonium ion is represented by the following formula (1). Embedded image (In the above formula (1), R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group having 1 to 30 carbon atoms or a polyalkylene oxide group.)