JP4098284B2 - 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 of a large amount of L-lactic acid by a fermentation method from sugars obtained from corn, straw, etc., and has become inexpensive. 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, as a plasticizer, techniques (Patent Documents 1 and 2) using polyalkylene glycol diester in a lactic acid-based polymer have been disclosed. Triethylene glycol diacetate specifically described in Examples of these documents is It has poor volatility and triethylene glycol di (2-ethylhexanoate) or polyethylene glycol dibenzoate has low plasticization efficiency and also contains crystalline polylactic acid (optical purity of 90% or more). When blended with a polylactic acid resin (hereinafter referred to as a crystalline polylactic acid-containing system), there is a drawback that bleeding tends to occur.
JP-A-11-323113 JP 2003-147180 A

  The problem of the present invention is that it has excellent volatility resistance, can impart flexibility without hindering the transparency of the biodegradable resin, and does not cause bleeding in a crystalline polylactic acid-containing system having excellent moldability. It is an object of the present invention to provide a biodegradable resin plasticizer that can be blended and a biodegradable resin composition 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.

A- [O (EO) _p -R] ₂ (1)
(In the formula, A represents a residue obtained by removing two hydroxyl groups from a linear or branched dihydric alcohol having 2 to 8 carbon atoms, and R represents a linear or branched acyl group having 2 to 6 carbon atoms. The two Rs may be the same or different, EO represents an oxyethylene group, p represents the average number of moles added of ethylene oxide, and 3 ≦ 2p ≦ 20.

  The plasticizer of the present invention can provide flexibility without inhibiting the transparency of the biodegradable resin, and can be blended in a crystalline polylactic acid-containing system having excellent moldability without causing bleeding. The biodegradable resin composition of the present invention is excellent in flexibility, transparency and bleed resistance, and can also prevent whitening when a sheet or film comprising the biodegradable resin composition of the present invention is folded.

[Plasticizer]
In the compound (1), A represents a residue obtained by removing two hydroxyl groups from a linear or branched dihydric alcohol having 2 to 8 carbon atoms, and the residue of a dihydric alcohol having 2 to 4 carbon atoms is preferable. R represents a linear or branched acyl group having 2 to 6 carbon atoms, preferably an acyl group having 2 to 4 carbon atoms. Two Rs may be the same or different. EO represents an oxyethylene group, p represents the average number of moles of ethylene oxide added, and is a number of 3 ≦ 2p ≦ 20, but 4 ≦ 2p ≦ 10 is preferable.

  If the carbon number of A exceeds 8 or the carbon number of R exceeds 6, the compatibility with the resin decreases, and heat treatment or the like tends to cause bleeding, which is not preferable. When the average total number of added moles 2p of ethylene oxide is less than 3, the volatilization resistance is insufficient, the volatilization during processing is large, the workability is lowered, and when it exceeds 20, bleed tends to occur again.

  The average molecular weight of the compound (1) is preferably 250 or more, more preferably 250 to 800, and particularly preferably 300 to 800 from the viewpoints of flexibility, transparency, bleed resistance, and volatile resistance.

The molecular weight can be obtained by calculating the saponification value by the method described in JIS K0070 and calculating from the following formula.
Molecular weight = 56108 × 2 / saponification value

  The solubility parameter of the compound (1) is preferably from 9.1 to 9.8, more preferably from 9.3 to 9.6, from the viewpoint of bleed resistance and volatility resistance.

Preferred specific examples of the compound (1) include polyethylene glycol diacetate, polyethylene glycol dipropionate, polyethylene glycol dibutyrate, wherein the number of moles of ethylene oxide added to the corresponding dihydric alcohol is 3 to 20, preferably 4 to 10. Polyoxyethylene 1,2-propanediol ether diacetate, polyoxyethylene 1,2-propanediol ether dipropionate, polyoxyethylene 1,2-propanediol ether dibutyrate, polyoxyethylene 1,3-propanediol ether Diacetate, polyoxyethylene 1,3-propanediol ether dipropionate, polyoxyethylene 1,3-propanediol ether dibutyrate, polyoxyethylene 1,4-butanedio Ether diacetate, polyoxyethylene 1,4-butanediol ether dipropionate, polyoxyethylene 1,4-butanediol ether dibutyrate, polyoxyethylene 1,3-butanediol ether diacetate, polyoxyethylene 1,3 -Butanediol ether dipropionate, polyoxyethylene 1,3-butanediol ether dibutyrate, polyoxyethylene 1,5-pentanediol ether diacetate, polyoxyethylene 1,5-pentanediol ether dipropionate, polyoxy Ethylene 1,5-pentanediol ether dibutyrate, polyoxyethylene 1,2-pentanediol ether diacetate, polyoxyethylene 1,2-pentanediol ether dipropionate , Polyoxyethylene 1,2-pentanediol ether dibutyrate, polyoxyethylene 1,6-hexanediol ether diacetate, polyoxyethylene 1,6-hexanediol ether dipropionate, polyoxyethylene 1,6-hexanediol Ether dibutyrate, polyoxyethylene 1,2-hexanediol ether diacetate, polyoxyethylene 1,2-hexanediol ether dipropionate, polyoxyethylene 1,2-hexanediol ether dibutyrate, polyoxyethylene 1,8 -Octanediol ether diacetate, polyoxyethylene 1,8-octanediol ether dipropionate, polyoxyethylene 1,8-octanediol ether dibutyrate, polyoxyethylene Examples include tylene 1,2-octanediol ether diacetate, polyoxyethylene 1,2-octanediol ether dipropionate, and polyoxyethylene 1,2-octanediol ether dibutyrate.
These compounds can be used alone or in combination.

The production method of the compound (1) of the present invention is not particularly limited, and for example, the formula (2)
HO-A-OH (2)
(In the formula, A has the above-mentioned meaning.)
It is obtained by adding ethylene oxide to a dihydric alcohol represented by the following formula using KOH, NaOH or the like as a catalyst, followed by esterification with a fatty acid or fatty acid anhydride having 2 to 6 carbon atoms.

  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- 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 having an optical purity of less than 90% = 100/0 to 10/90, preferably 100/0 to 25/75.

  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 The product name Nature Works etc. is mentioned.

  Among these, polylactic acid resin (for example, Mitsui Chemical Co., Ltd., trade name Lacia H-100, H-280, H-400, H-440; Cargill Dow Polymers, trade name Nature Works) is preferable. ), 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 composition of the present invention can contain other components such as a lubricant 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 3 parts by weight, 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.

Synthesis example 1
200 g of PEG300 (manufactured by Kanto Chemical Co., Inc., average molecular weight 300) was charged into a 1 L flask equipped with a stirrer, a thermometer and a dropping funnel, and 204 g of acetic anhydride was added dropwise at 110 ° C. over 1 hour, and further at 120 ° C. for 2 hours. Aged. After completion of the reaction, unreacted acetic anhydride and by-produced acetic acid are distilled off at 100 ° C./2.5 kPa, and further steaming is performed at 100 ° C./1.3 kPa, and the desired plasticizer 1 (polyethylene glycol diacetate, An average total number of added moles of ethylene oxide of 6.4) was obtained.

Synthesis example 2
The target plasticizer 2 (polyethylene glycol diacetate) was used in the same manner as in Synthesis Example 1 except that 205 g of PEG 400 (manufactured by Sigma-Aldrich Japan, average molecular weight 400) was used instead of PEG 300, and the amount of acetic anhydride was changed to 157 g. The average total number of added moles of ethylene oxide was 8.7).

Synthesis example 3
A 10-liter stirring rotary autoclave equipped with a measuring tank for ethylene oxide was charged with 500 g of 1,4-butanediol (manufactured by Kanto Chemical Co., Ltd.) and 3.1 g of potassium hydroxide, followed by nitrogen substitution and 110 ° C. And dehydration was performed at 5.3 kPa for 1 hour. Next, the temperature was raised to 150 ° C., ethylene oxide was introduced into an autoclave at 1466 g at a pressure of 3.5 kg / cm ² , and the reaction was continued until the pressure decreased and became constant. After completion of the reaction, the synthesized sample was extracted at a reduced temperature. The extracted sample was transferred to a 3 L flask, 24 g of KYOWARD 600S (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the catalyst was adsorbed for 1 hour at 80 ° C. under slightly pressurized nitrogen. After the treatment, the adsorbent was filtered to obtain an intermediate polyoxyethylene 1,4-butanediol ether (average number of added moles of ethylene oxide 6).

  The target plasticizer 3 (polyoxyethylene 1,4) was used in the same manner as in Synthesis Example 1 except that 200 g of the above polyoxyethylene 1,4-butanediol ether was used instead of PEG300 and the amount of acetic anhydride was changed to 173 g. -The average total added mole number of butanediol ether diacetate and ethylene oxide was 6).

Comparative Synthesis Example 1
Comparative plasticizer 1 (triethylene glycol diacetate) was obtained in the same manner as in Synthesis Example 1 except that triethylene glycol (Wako Pure Chemical Industries, Ltd.) was used instead of PEG300.

Comparative Synthesis Example 2
A comparative plasticizer 2 (average total number of added moles of polyethylene glycol diacetate and ethylene oxide of 22.3) was obtained in the same manner as in Synthesis Example 1 except that PEG1000 (Wako Pure Chemical Industries, Ltd.) was used instead of PEG300. .

Examples 1-3 and Comparative Examples 1-4
The plasticizers obtained in Synthesis Examples 1 to 3 and Comparative Synthesis Examples 1 and 2 and the following comparative plasticizers 3 and 4 as comparative plasticizers were evaluated for volatility by the following method.
In addition, 100 parts by weight of an amorphous polylactic acid resin (manufactured by Mitsui Chemicals, Ltd., LACEA H-280) vacuum-dried at 50 ° C. for 24 hours using plasticizers 1 to 3 and comparative plasticizers 1 to 4 And the composition which consists of 20 weight part of plasticizers was knead | mixed for 15 minutes with a 130 degreeC 4 inch roll, and the test piece of thickness 0.5mm was created with the 160 degreeC press molding machine. The obtained test pieces were evaluated for flexibility, transparency and bleed resistance by the following methods. These results are shown in Table 1.

Comparative plasticizer 3: Tetraethylene glycol (2-ethylhexanoic acid ester) (manufactured by Sigma-Aldrich Japan)
Comparative plasticizer 4: Acetylated tributyl citrate (Taoka Chemical Co., Ltd.)

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

<Flexibility evaluation method>
The test piece was punched out with a No. 3 dumbbell, left in a constant temperature room at a temperature of 23 ° C. and a humidity of 50% RH for 24 hours, a tensile test was conducted at a tensile speed of 200 mm / min, and a 100% modulus was indicated.

<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)>
The test piece (length 100 mm × width 100 mm × thickness 0.5 mm) was left in a thermostatic chamber at 60 ° C. for 60 hours, and the presence or absence of plasticizer bleeding on the surface was observed with the naked eye.

Examples 4-6 and Comparative Examples 5-8
100 parts by weight of a crystalline polylactic acid resin (manufactured by Mitsui Chemicals, Lacia H-400) vacuum-dried at 50 ° C. for 24 hours using the above plasticizers 1 to 3 and comparative plasticizers 1 to 4, and a plasticizer 15 A composition consisting of parts by weight is kneaded for 10 minutes with a 180 ° C. kneader (Toyo Seiki Co., Ltd., “Labo Plast Mill”), and a test piece having a thickness of 0.5 mm with a 190 ° C. press molding machine. It was created. The obtained test pieces were evaluated for flexibility, transparency and bleed resistance in the same manner as in Examples 1 to 3. However, the bleed resistance evaluation was performed by leaving at 70 ° C. for 72 hours. The results are shown in Table 2.
In Comparative Examples 6 to 8, since the bleed was “present”, the flexibility and the transparency were not evaluated.

Claims (2)

A plasticizer for a polylactic acid resin containing a compound represented by the general formula (1).
A- [O (EO) _p -R] ₂ (1)
(In the formula, A represents a straight-chain or residue obtained by removing two hydroxyl groups from a dihydric alcohol branched, R represents a linear or branched chain acyl group having from 2 to 4 carbon atoms from 2 to 4 carbon atoms The two Rs may be the same or different, EO represents an oxyethylene group, p represents the average number of moles added of ethylene oxide, and 4 ≦ 2p ≦ 10. ) The plasticizer for polylactic acid resin according to claim 1, wherein the compound represented by the general formula (1) has an average molecular weight of 250 or more.