JP4116015B2 - Plasticizer for biodegradable resin - Google Patents

Description

  The present invention relates to a biodegradable resin plasticizer and a biodegradable resin composition excellent in flexibility, transparency and bleed resistance.

  General-purpose resins made from petroleum, such as polyethylene, polypropylene, polyvinyl chloride, and polystyrene, are lightweight and have good processability, physical properties, and durability. Used in various fields such as building materials and food packaging. However, these resin products have a disadvantage of good durability at the stage of finishing and discarding their functions, and are inferior in degradability in nature, and thus may affect the ecosystem.

  In order to solve such problems, polylactic acid and copolymers of lactic acid and other aliphatic hydroxycarboxylic acids, aliphatic polyhydric alcohols and aliphatic polycarboxylic acids are used as thermoplastic resins and biodegradable polymers. Biodegradable resins such as aliphatic polyesters derived from styrene and copolymers containing these units have been developed.

  When these biodegradable resins are placed in soil, seawater, or in the body of an animal, they start to degrade in a few weeks due to the action of enzymes produced by naturally occurring microorganisms. Disappears in between. Furthermore, the decomposition products become lactic acid, carbon dioxide, water, etc., which are harmless to the human body. Among the aliphatic polyesters, polylactic acid resin is made from a sugar that can be taken from corn, straw, etc., and L-lactic acid has been made in large quantities by fermentation. In addition, because the obtained polymer has the characteristics of high rigidity and transparency, it is expected to be used at present, such as the field of agricultural civil engineering materials such as flat yarns, nets, gardening materials, seedling pots, envelopes with windows. Used for shopping bags, compost bags, stationery, miscellaneous goods, etc. However, in the case of polylactic acid resin, it is fragile, hard, and lacks flexibility, all of which are limited to the field of hard molded products. When molded into a film or the like, it becomes inflexible or whitens when bent. The current situation is that it is not used in the soft or semi-rigid field. Various methods of adding a plasticizer have been proposed as a technique applied to the soft and semi-rigid fields. For example, a technique using a dibasic acid alkyl polyalkylene glycol ether ester in a lactic acid-based polymer as a plasticizer (Patent Document 1) is disclosed, but dibutyl diglycol listed in Examples of this Patent Document 1 Adipate has a drawback that it easily bleeds when blended with a polylactic acid resin containing crystalline polylactic acid.

Patent Document 2 discloses an injection-molded body using a resin composition containing a lactic acid resin, and describes that the molten resin temperature at the time of injection molding of the lactic acid resin is preferably 170 to 210 ° C. Patent Document 3 discloses a lactic acid resin composition in which a plasticizer is mixed, and the boiling point of the plasticizer when the lactic acid resin is melt-extruded is preferably 220 ° C. or higher at normal pressure, more preferably 250. It is described that the temperature is not lower than ° C. However, the plasticizers described in these cited documents are not sufficiently satisfactory in terms of volatility resistance, and transparency, flexibility and bleed resistance when blended with a biodegradable resin.
JP 2002-146170 A JP 2005-60691 A JP 2003-231798 A

  An object of the present invention is to bleed a polylactic acid resin containing crystalline polylactic acid that has excellent volatility resistance, can impart flexibility without impairing the transparency of the biodegradable resin, and has excellent moldability. An object of the present invention is to provide a biodegradable resin plasticizer that can be blended without causing odor, and a biodegradable resin composition that is excellent in flexibility, transparency, and bleed resistance.

  The present invention relates to a biodegradable resin plasticizer containing a compound represented by the general formula (1) (hereinafter referred to as compound (1)), a biodegradable resin, and a biodegradable resin containing this plasticizer. A resin composition is provided.

_{^{R 1 O (EO) m -CORCOO-}} (EO) n R 2 (1)
(Wherein R ¹ and R ² represent a linear or branched alkyl group having 1 to 4 carbon atoms, R represents a linear or branched alkylene group having 1 to 3 carbon atoms, and R ¹ and R ² represent EO is an oxyethylene group, m and n are the average number of moles of ethylene oxide added, and are 0 ≦ m ≦ 5, 0 ≦ n ≦ 5, and 1 ≦ m + n ≦ 8. )

  The plasticizer of the present invention has excellent volatility resistance, can impart flexibility without impairing the transparency of the biodegradable resin, and is a polylactic acid resin containing crystalline polylactic acid with excellent moldability. In addition, the biodegradable resin composition of the present invention is excellent in flexibility, transparency and bleed resistance.

[Plasticizer]
In the compound (1), R ¹ and R ² represent a linear or branched alkyl group having 1 to 4 carbon atoms which may be the same or different. From the viewpoint of bleed resistance, the alkyl having 1 to 2 carbon atoms Groups are preferred. R represents a linear or branched alkylene group having 1 to 3 carbon atoms, and an alkylene group having 2 to 3 carbon atoms is preferable from the viewpoint of flexibility. EO represents an oxyethylene group. m and n represent the average number of moles of ethylene oxide added, and 0 ≦ m ≦ 5, 0 ≦ n ≦ 5, and 1 ≦ m + n ≦ 8, but 4 ≦ m + n ≦ 8 is preferable, and volatile resistance viewpoint Therefore, 6 ≦ m + n ≦ 8 is more preferable, and m and n are each particularly preferably 3 from the viewpoints of flexibility and volatility resistance.

When R ¹ and R ² have 4 or less carbon atoms and R has 3 or less carbon atoms, the compatibility with the resin is good, and it is preferable from the viewpoint that bleeding does not easily occur even when heat treatment is performed. Moreover, if R does not contain an unsaturated bond, the elastic modulus of the resin is preferably lowered. When the total number of added moles m + n of ethylene oxide is 1 or more, preferably 6 or more, volatile resistance is good, volatilization during processing is small, good workability is obtained, and when it is 8 or less, bleeding is unlikely to occur. It is preferable from the viewpoint. The distribution of ethylene oxide is preferably narrow.

  The average molecular weight of the compound (1) is preferably 250 or more, more preferably 250 to 700, particularly preferably 300 to 600, and most preferably 330 to 500 from the viewpoints of flexibility, transparency, bleed resistance and volatile resistance. . The average molecular weight can be obtained by calculating the saponification value by the method described in JIS K0070 and calculating from the following formula.

  Average molecular weight = 56108 × 2 / saponification value

Preferred specific examples of compound (1) include dibasic acid selected from malonic acid, succinic acid or glutaric acid, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tetraethylene. Examples include esters with polyethylene glycol monoalkyl ethers such as glycol monomethyl ether, and particularly preferred examples include esters of succinic acid and triethylene glycol monomethyl ether from the viewpoint of flexibility and volatility resistance. .
These compounds can be used alone or in combination.

  In order to knead plasticizers and other additives into polylactic acid and to process the composition, it is necessary to have a temperature higher than the melting point of polylactic acid crystals, and the plasticizer must also have volatility resistance corresponding to that. is there. The volatilization of the plasticizer at the time of processing is not preferable because the quality of the processed product varies and the working environment deteriorates. As a plasticizer having excellent volatility resistance, a 10% weight loss temperature in thermogravimetric analysis is preferably 220 ° C. or higher, more preferably 230 ° C. or higher, and particularly preferably 250 ° C. or higher. Here, the 10% weight loss temperature in the thermogravimetric analysis of the plasticizer is a value determined by the measurement method described in the Examples.

  The production method of the compound (1) of the present invention is not particularly limited. For example, in the presence of an acid catalyst such as paratoluenesulfonic acid monohydrate and sulfuric acid, and a metal catalyst such as dibutyltin oxide, the number of carbon atoms is 3 to 5. By directly reacting a saturated dibasic acid or anhydride thereof with polyethylene glycol monoalkyl ether, or transesterifying a lower alkyl ester of a saturated dibasic acid having 3 to 5 carbon atoms with polyethylene glycol monoalkyl ether. can get. Specifically, for example, polyethylene glycol monoalkyl ether, saturated dibasic acid, and paratoluenesulfonic acid monohydrate as a catalyst, polyethylene glycol monoalkyl ether / saturated dibasic acid / paratoluenesulfonic acid monohydrate. (Molar ratio) = 2 to 4/1 / 0.001 to 0.05, charged in a reaction vessel, in the presence or absence of a solvent such as toluene, at normal pressure or reduced pressure, temperature 100 to 130 Compound (1) is obtained by performing dehydration at ° C. A method of performing the reaction under reduced pressure without using a solvent is preferred.

  In addition to the compound (1), the plasticizer of the present invention can contain an unreacted component in the production of the compound (1), a plasticizer other than the compound (1), and the like.

  Examples of the plasticizer other than the compound (1) include acetylated monoglyceride and acetylated tributyl citrate.

  The content of the compound (1) in the plasticizer of the present invention is preferably 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% from the viewpoint of achieving the object of the present invention. % By weight or more.

[Biodegradable resin]
The biodegradable resin used in the present invention has a biodegradability based on JIS K6953 (ISO 14855) “Aerobic and ultimate biodegradability and disintegration test under controlled aerobic compost conditions”. The polyester resin which has is preferable.

  The biodegradable resin used in the present invention is not particularly limited as long as it has a biodegradability capable of being decomposed into a low molecular weight compound with the participation of microorganisms in nature. For example, aliphatic polyesters such as polyhydroxybutyrate, polycaprolactone, polybutylene succinate, polybutylene succinate / adipate, polyethylene succinate, polylactic acid resin, polymalic acid, polyglycolic acid, polydioxanone, poly (2-oxetanone) Aliphatic aliphatic copolyesters such as polybutylene succinate / terephthalate, polybutylene adipate / terephthalate, polytetramethylene adipate / terephthalate; starch, cellulose, chitin, chitosan, gluten, gelatin, zein, soy protein, collagen, keratin, etc. And a mixture of the above natural polymer and the above aliphatic polyester or aliphatic aromatic copolyester.

  Of these, aliphatic polyesters are preferable from the viewpoint of processability, economy, and availability in large quantities, and polylactic acid resins are more preferable from the viewpoint of physical properties. Here, the polylactic acid resin is polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid and the like, and glycolic acid and hydroxycaproic acid are preferable. The molecular structure of polylactic acid is preferably composed of 20 to 100 mol% of either L-lactic acid or D-lactic acid and 0 to 80 mol% of each enantiomer. The copolymer of lactic acid and hydroxycarboxylic acid is composed of 85 to 100 mol% of either L-lactic acid or D-lactic acid and 0 to 15 mol% of hydroxycarboxylic acid units. These polylactic acid resins can be obtained by dehydrating polycondensation using L-lactic acid, D-lactic acid and hydroxycarboxylic acid as a raw material by selecting those having the required structure. Preferably, it can be obtained by ring-opening polymerization by selecting a desired structure from lactide, which is a cyclic dimer of lactic acid, glycolide, which is a cyclic dimer of glycolic acid, and caprolactone. Lactide includes L-lactide which is a cyclic dimer of L-lactic acid, D-lactide which is a cyclic dimer of D-lactic acid, meso-lactide obtained by cyclic dimerization of D-lactic acid and L-lactic acid, and D-lactide. There is DL-lactide, which is a racemic mixture of lactide and L-lactide. Any lactide can be used in the present invention. However, the main raw material is preferably D-lactide or L-lactide.

  Among the polylactic acid resins, from the viewpoint of heat resistance, a crystal having an optical purity of 90% or more and a ratio of crystalline polylactic acid having an optical purity of 90% or more and polylactic acid having an optical purity of less than 90% by weight is preferable. Polylactic acid / polylactic acid with an optical purity of less than 90% = 100/0 to 10/90, preferably 100/0 to 25/75, more preferably 100/0 to 50/50, particularly preferably 100/0 to 90 / 10 polylactic acid resin.

  Examples of commercially available biodegradable resins include DuPont, trade name Biomax; BASF, trade name Ecoflex; Eastman Chemicals, trade name EsterBio, Showa Polymer Co., Ltd., trade name Bionore; Nippon Synthetic Chemical Industry Co., Ltd., trade name: Matterby; Mitsui Chemicals, Inc., trade name: Lacia; Nippon Shokubai Co., Ltd., trade name: Lunare; Chisso Corporation, trade name: Novon; Cargill Dow Polymers Product name, Nature Works, etc.

  Among these, preferably a polylactic acid resin (for example, trade name Lacia H-100, H-280, H-400, H-440, manufactured by Mitsui Chemicals, Inc .; trade name, Nature Works, manufactured by Cargill Dow Polymers). ), Aliphatic polyesters such as polybutylene succinate (product name Bionore, manufactured by Showa Polymer Co., Ltd.), aliphatic aromatic copolyesters such as poly (butylene succinate / terephthalate) (trade name Bio, manufactured by DuPont) Max).

  From the viewpoint of heat resistance, a crystalline biodegradable resin having a high L-lactic acid purity is preferable, and orientation crystallization is preferably performed by stretching. Examples of the crystalline biodegradable resin include Lacia H-100, H-400, and H-440 manufactured by Mitsui Chemicals.

[Biodegradable resin composition]
The biodegradable resin composition of the present invention contains the plasticizer of the present invention and a biodegradable resin. The content of the plasticizer of the present invention is preferably 1 to 70 parts by weight, more preferably 3 to 50 parts, from the viewpoints of flexibility, transparency, bleed resistance and economy with respect to 100 parts by weight of the biodegradable resin. Part by weight, particularly preferably 5 to 30 parts by weight.

  The content of the biodegradable resin in the biodegradable resin composition of the present invention is preferably 50% by weight or more, more preferably 70% by weight or more from the viewpoint of achieving the object of the present invention.

The elastic modulus of the biodegradable resin composition of the present invention is preferably 1700 MPa or less, and more preferably 1300 MPa or less.
The elongation at break of the biodegradable resin composition of the present invention is preferably 180% or more, and more preferably 200% or more.
The haze value of the biodegradable resin composition of the present invention is preferably 4% or less, and more preferably 3% or less.

  The composition of the present invention can contain other components such as a lubricant and a crystal nucleating agent in addition to the plasticizer. Examples of the lubricant include hydrocarbon waxes such as polyethylene wax, fatty acids such as stearic acid, fatty acid esters such as glycerol ester, metal soaps such as calcium stearate, ester waxes such as montanic acid wax, and alkylbenzene sulfone. Anionic surfactants having an aromatic ring such as acid salts, anionic surfactants having an alkylene oxide addition moiety such as polyoxyethylene alkyl ether sulfate, and the like. The content of these lubricants is preferably 0.05 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and particularly preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the biodegradable resin.

  Examples of the crystal nucleating agent include natural or synthetic silicate compounds, titanium oxide, barium sulfate, tricalcium phosphate, calcium carbonate, sodium phosphate, etc., and silicate compounds include kaolinite, halloysite, talc, smectite, Vermulite, mica, etc. can be exemplified. The content of these crystal nucleating agents is preferably 0.05 to 5 parts by weight and more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the biodegradable resin.

  The composition of the present invention includes an antistatic agent, an antifogging agent, a light stabilizer, an ultraviolet absorber, a pigment, an inorganic filler, an antifungal agent, an antibacterial agent, a foaming agent, a flame retardant, Plasticizers other than the plasticizer of the present invention can be contained as long as the object of the present invention is not hindered.

  Since the composition of the present invention has good processability and can be processed at a low temperature such as 160 to 190 ° C., it can be calendered and the plasticizer is hardly decomposed. The composition of the present invention can be formed into a film or sheet and used for various applications. Sheets and films made of the biodegradable resin composition of the present invention are preferred because they do not whiten when folded.

Synthesis example 1
A 1 L flask equipped with a stirrer, a thermometer and a dehydrating tube was charged with 75.2 g of succinic acid, 251 g of triethylene glycol monomethyl ether, and 1.59 g of dibutyltin oxide, and reacted at 185 ° C. for 12 hours. After completion of the reaction, 1.2 g of 85% phosphoric acid was added, and the mixture was heated and stirred at 70 ° C. for 30 minutes, and then Kyoward 600S (manufactured by Kyowa Chemical Industry Co., Ltd.) was added for adsorption treatment, followed by pressure filtration. Further, excess triethylene glycol monomethyl ether was distilled off under reduced pressure, followed by pressure filtration, and plasticizer 1 (in formula (1), R ¹ and R ² are methyl groups, R is an ethylene group, m = n = 3).

Synthesis example 2
A 1 L flask equipped with a stirrer, thermometer, dehydration tube and reflux tube was charged with 118 g of succinic acid, 361 g of diethylene glycol monomethyl ether, 250 mL of toluene, and 2.0 g of paratoluenesulfonic acid monohydrate, and reacted at 120 ° C. for 9 hours. . After cooling, 350 mL of ethyl acetate was added, washed with an aqueous sodium carbonate solution and further with a saturated aqueous sodium chloride solution, and dried over anhydrous sodium sulfate. Ethyl acetate and toluene are removed with an evaporator, and low-boiling components are distilled off under reduced pressure. Plasticizer 2 (in formula (1), R ¹ and R ² are methyl groups, R is an ethylene group, m = n = 2 Compound) was obtained.

Synthesis example 3
A 1 L flask equipped with a stirrer, thermometer, dehydration tube and reflux tube was charged with 90.1 g of succinic anhydride, 562.3 g of tetraethylene glycol monomethyl ether, 200 mL of toluene, and 2.0 g of paratoluenesulfonic acid monohydrate, and 120 The reaction was carried out at 0 ° C. for 9 hours. After cooling, Kyoward 500SH (manufactured by Kyowa Chemical Industry Co., Ltd.) was added for adsorption treatment, followed by pressure filtration. Excess tetraethylene glycol monomethyl ether was distilled off under reduced pressure, followed by pressure filtration to perform plasticizer 3 (compound (1) wherein R ¹ and R ² are methyl groups, R is an ethylene group, and m = n = 4) )

Synthesis example 4
In the same manner as in Synthesis Example 3, a plasticizer 4 (a compound in which R ¹ and R ² are methyl groups, R is a methylene group, and m = n = 3 in formula (1)) is obtained from malonic acid and triethylene glycol monomethyl ether. It was.

Synthesis example 5
In the same manner as in Synthesis Example 2, a plasticizer 5 (a compound in which R ¹ and R ² are methyl groups, R is a trimethylene group, and m = n = 2) was obtained from glutaric acid and diethylene glycol monomethyl ether.

Comparative Synthesis Example 1
Comparative plasticizer 1 from adipic acid and triethylene glycol monomethyl ether in the same manner as in Synthesis Example 1 (in the formula (1), R ¹ and R ² are methyl groups, R is a tetramethylene group, and m = n = 3) )

Comparative Synthesis Example 2
Comparative plasticizer 2 from fumaric acid and diethylene glycol monomethyl ether in the same manner as in Synthesis Example 2 (in formula (1), R ¹ and R ² are methyl groups, R is —CH═CH— group, m = n = 2 Compound) was obtained.

Comparative Synthesis Example 3
Comparative plasticizer 3 (compound of formula (1) where R ¹ and R ² are butyl groups, R is a tetramethylene group, m = n = 2) is obtained from adipic acid and diethylene glycol monobutyl ether in the same manner as in Synthesis Example 2. It was.

Examples 1-5 and Comparative Examples 1-3
Table 1 shows the molecular weights of the plasticizers obtained in Synthesis Examples 1 to 5 and Comparative Synthesis Examples 1 to 3, and the volatile resistance results evaluated by the following method.
In addition, a crystalline polylactic acid resin (LACEA H-400 manufactured by Mitsui Chemicals, Inc.) was vacuum-dried at 50 ° C. for 24 hours using the plasticizers obtained in Synthesis Examples 1-5 and Comparative Synthesis Examples 1-3. ) A composition consisting of 100 parts by weight and 15 parts by weight of a plasticizer was kneaded for 10 minutes in a 180 ° C. kneader (Toyo Seiki Co., Ltd., “Lab Plast Mill”), and the thickness was measured using a 190 ° C. press molding machine. A test piece of 0.5 mm was prepared. The obtained test pieces were evaluated for flexibility, transparency and bleed resistance by the following methods. These results are also shown in Table 1.
Examples 2 and 5 are reference examples.

<Evaluation method for volatility>
Using a thermogravimetric analyzer, the plasticizer was heated from 25 ° C. to 300 ° C. (5 ° C./min) in a nitrogen atmosphere, and the temperature at which the weight was reduced by 10% was measured. The higher the temperature, the better the volatility resistance.

<Flexibility evaluation method>
The test piece was punched with a No. 3 dumbbell, left in a temperature-controlled room at a temperature of 23 ° C. and a humidity of 50% RH for 24 hours, a tensile test was performed at a tensile speed of 50 mm / min, and the flexibility was expressed in terms of elastic modulus and breaking elongation%. . The lower the elastic modulus value, the higher the breaking elongation% value, the higher the flexibility.

<Transparency evaluation method>
The haze value of the test piece was measured using an integrating sphere light transmittance measuring device (haze meter) defined in JIS-K7105. Smaller numbers indicate better transparency.

<Bleed resistance (with or without bleed)>
A test piece (length 100 mm × width 100 mm × thickness 0.5 mm) was left in a thermostatic chamber at 70 ° C. for 72 hours, and the presence or absence of a plasticizer bleed on the surface was observed with the naked eye. Evaluation of bleed resistance is an indispensable item for evaluating the performance of plasticizers because bleed impairs not only the surface quality of the resin but also the flexibility of the resin itself.

  As is clear from Table 1, the plasticizers 1 to 5 used in Examples 1 to 5 are excellent in volatility, can impart flexibility without hindering the transparency of the biodegradable resin, and have moldability. Can be blended without causing bleeding in a polylactic acid resin containing crystalline polylactic acid. From the viewpoint of volatility resistance, it can be seen that plasticizers 1 and 3 to 5 are particularly excellent.

Claims (4)

A plasticizer for a biodegradable resin containing a compound represented by the general formula (1).
_{^{R 1 O (EO) m -CORCOO-}} (EO) n R 2 (1)
(Wherein R ¹ and R ² represent a linear alkyl group having 1 to ² carbon atoms, R represents a linear or branched alkylene group having 1 to 3 carbon atoms, and R ¹ and R ² may be the same or different. EO is an oxyethylene group, m and n are the average number of moles of ethylene oxide added, and 3 ≦ m ≦ 5, 3 ≦ n ≦ 5, and 6 ≦ m + n ≦ 8.)
  The plasticizer for a biodegradable resin according to claim 1, wherein the compound represented by the general formula (1) has an average molecular weight of 250 or more.   A biodegradable resin composition comprising a biodegradable resin and the plasticizer according to claim 1. The biodegradable resin composition according to claim 3, wherein the biodegradable resin is a polylactic acid resin.