JPH1180522A - Biodegradable plastic composition and control of biodegradation rate of biodegradable plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable plastic composition having a stably controlled biodegradation rate and useful as a material for agriculture, forestry and fisheries, such as a film and a planting pot, and earthwork such as a water- retaining sheet and a plant net by allowing a biodegradable plastic to include a carbodiimide compound. SOLUTION: This biodegradable plastic composition comprises (A) 100 pts.wt. biodegradable plastic such as an aliphatic polyester resin (e.g. a polybutylene succinate/adipate and a polylactic acid) and (B) a carbodiimide compound having one or more carbodiimide groups in one molecule, such as 4,4'- dicyclohexylmethanecarbodiimide preferably in an amount of 0.01-10 pts.wt. The mixing method is exemplified by the method of melt-kneading by an extruder. The component B is obtained by a decarbonation condensation reaction or the like of an organic diisocyanate in the presence of a catalyst such as an organic phosphorus-based compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable plastic composition and a method for controlling the biodegradation rate of a biodegradable plastic. More specifically, the present invention relates to a biodegradable plastic composition in which the biodegradation rate is controlled by adding a carbodiimide compound. The present invention relates to a degradable plastic composition and a method for controlling the biodegradation rate of a biodegradable plastic.

[0002]

2. Description of the Related Art In recent years, while problems such as environmental pollution due to plastic waste have been highlighted, research and development of biodegradable plastics have been promoted due to the growing need and significance for environmental conservation.

[0003] Biodegradable plastics can be broadly classified into three types: those having an aliphatic polyester resin, polyvinyl alcohol or polysaccharide in the molecular skeleton. Among them, the aliphatic polyester resins are generally It has not been used as a biodegradable plastic because it has a low melting point, poor thermal stability during production, and a sufficient molecular weight to obtain physical properties suitable for practical molded articles. With the development of technology to overcome this problem, high molecular weight aliphatic polyester resin appeared,
Agriculture, forestry and fisheries materials (films, planting pots, fishing lines, fish nets, etc.), civil engineering materials (water retention sheets, plant nets, sandbags, etc.), packaging and container fields (soils that are difficult to recycle due to soil, food, etc.) Has begun to be used.

[0004] Biodegradable plastics such as the above aliphatic polyester resins have the same level of function (eg, strength, water resistance, etc.) as conventional plastics during use.
Moldability and heat resistance), and must be rapidly decomposed by microorganisms generally present in nature at the time of disposal.

[0005] Under such circumstances, there have been several proposals concerning the control of the biodegradation rate of biodegradable plastics, for example, with the aim of shortening the decomposition time by adding a hydrolase. (Japanese Patent Laid-Open No. 4-16)
No. 8149) or, conversely, to reduce unreacted monomers and impurities, low molecular weight compounds such as linear and cyclic oligomers in the polymer, and to extend the decomposition time (Japanese Patent Application Laid-Open No. Hei 9-1997). No. 12688).

[0006]

However, at present, the biodegradable plastics according to the above-mentioned prior art are used in a process of producing pellets as a raw material of a plastic product or producing a product from the pellets. Exposure to moisture in the atmosphere or application of heat causes a hydrolysis reaction in the biodegradable plastic,
There are problems that the initial physical properties of the molded article are degraded or varied, and that the biodegradability of the product is unstable, and the adjustment of the biodegradability is not yet sufficient.

An object of the present invention is to provide a biodegradable plastic composition and a method for controlling the biodegradable rate of a biodegradable plastic in which the rate of biodegradation is stably adjusted by solving the problems of the prior art. Was.

[0008]

According to the present invention, there is provided a biodegradable plastic composition comprising a carbodiimide compound mixed with a biodegradable plastic. In addition, the configuration of the method for controlling the biodegradation rate of a biodegradable plastic employed in the present invention to achieve the above object is characterized in that a carbodiimide compound is added to the biodegradable plastic.

That is, the inventors of the present invention have conducted intensive studies to obtain a plastic composition having good biodegradability. As a result, one or more carbodiimide groups were added to the biodegradable plastic in the molecule. With respect to the biodegradable plastic composition obtained by blending a carbodiimide compound (including a polycarbodiimide compound), the hydrolysis resistance is improved, and further, the hydrolysis resistance depends on the type and the amount of the carbodiimide compound. Of the biodegradability of the biodegradable plastic by adding a carbodiimide compound to the biodegradable plastic having biodegradability based on the hydrolysis reaction. Have been found to be able to regulate the present invention, and have completed the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

Examples of the biodegradable plastic used in the present invention include polyester-based plastics which are metabolized by microorganisms. Among them, aliphatic polyester resins which are easily metabolized by microorganisms are preferred.

As the aliphatic polyester resin,
First, an aliphatic glycol / polybasic acid polyester resin obtained by reacting an aliphatic glycol with an aliphatic polybasic acid (or an anhydride thereof) in the presence of a catalyst; A high-molecular-weight aliphatic glycol / polybasic acid polyester resin obtained by reacting using a small amount of a coupling agent as appropriate can be exemplified.

The biodegradable plastic used in the present invention (aliphatic glycol / polybasic polyester resin)
Examples of the aliphatic glycols for the production of ethylene glycol, 1,4-butanediol,
Examples thereof include 6-hexanediol, decamethylene glycol, neopentyl glycol, and 1,4-cyclohexanedimethanol, and ethylene oxide can also be used. Incidentally, these glycols may be used in combination of two or more thereof.

The aliphatic polybasic acids which form biodegradable plastics (aliphatic glycol / polybasic acid polyester resin) by reacting with the above-mentioned aliphatic glycols and their acid anhydrides include succinic acid and adipic acid. And commercially available ones such as suberic acid, sebacic acid, dodecanoic acid, succinic anhydride and adipic anhydride can be used. Incidentally, two or more of these polybasic acids and / or acid anhydrides thereof may be used in combination.

The glycols and polybasic acids are aliphatic ones, but a small amount of other components such as aromatic glycols and aromatic polybasic acids such as trimellitic anhydride and pyromellitic anhydride. They can be used together. However, when these aromatic components are introduced, the biodegradability deteriorates. Therefore, the blending amount of the aromatic glycols and the aromatic polybasic acid is 20 parts by weight or less based on 100 parts by weight of the aliphatic glycol. It is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

The catalyst for producing the aliphatic glycol / polybasic acid polyester resin includes titanium, tin, antimony, cerium, zinc, cobalt, and the like.
Examples thereof include organic acid salts, alkoxides and oxides of metals such as iron, lead, manganese, aluminum, magnesium, and germanium. Of these, tin-based or aluminum-based compounds are preferable.

To produce the above-mentioned aliphatic glycol / polybasic acid polyester resin, equivalent amounts of aliphatic glycols and aliphatic polybasic acids and a catalyst are appropriately selected according to the starting compounds, if necessary. The reaction may be carried out by heating using the solvent thus prepared, and by suppressing the progress of the reaction, a prepolymer having a low degree of polymerization can be produced.

In the production of the aliphatic glycol / polybasic acid polyester resin as described above, in order to further increase the number average molecular weight, a coupling agent may be used for a prepolymer having a low polymerization degree. As the coupling agent, for example, diisocyanate, oxazoline, diepoxy compound, acid anhydride and the like can be mentioned, but use of diisocyanate is particularly preferable.

The type of the diisocyanate as the coupling agent is not particularly limited.
2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5
-Naphthalene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like. It is preferable from the viewpoint of the hue of the group-based glycol / polybasic acid polyester resin and the reactivity at the time of blending with the prepolymer.

The amount of the coupling agent is, for example, 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the prepolymer. The ring reaction is insufficient, and gelling easily occurs at 5 parts by weight or more.

The aliphatic glycol / polybasic acid polyester resin has a terminal hydroxyl group sealed with another compound via a double bond, urethane bond, urea bond or the like, or has been modified. It may be an aliphatic glycol / polybasic acid polyester resin.

As the aliphatic polyester resin,
Second, polylactic acid-based aliphatic polyester resin, specifically, lactic acid, malic acid, polymers of oxyacids such as glycolic acid or copolymers thereof, especially hydroxycarboxylic acid represented by polylactic acid Aliphatic polyester resins can be mentioned.

The above-mentioned polylactic acid-based aliphatic polyester resin is usually prepared by a so-called lactide method by a ring-opening polymerization of lactide as a cyclic diester and the corresponding lactone. It can be obtained by a synthetic method or a polycondensation method of formalin and carbon dioxide gas.

The catalyst for producing the polylactic acid-based aliphatic polyester resin includes tin, antimony,
Examples thereof include zinc, titanium, iron and aluminum compounds. Among them, tin catalysts and aluminum catalysts are preferable, and tin octylate and aluminum acetylacetonate are particularly preferable.

Among the above polylactic acid-based aliphatic polyester resins, poly-L-lactic acid obtained by lactide ring-opening polymerization is preferred because it is hydrolyzed to L-lactic acid and its safety has been confirmed. The polylactic acid-based aliphatic polyester resin used in the present invention is not limited to this, and the lactide used for the production is not limited to the L-form.

On the other hand, as the carbodiimide compound having one or more carbodiimide groups in a molecule (including a polycarbodiimide compound) used in the present invention, a compound synthesized by a generally well-known method is used. For example, it can be synthesized by subjecting various polyisocyanates to a decarboxylation condensation reaction in a solvent or an inert solvent at a temperature of about 70 ° C. or higher at a temperature of about 70 ° C. or higher, using an organic phosphorus compound or an organic metal compound as a catalyst. What can be done can be mentioned.

The monocarbodiimide compound contained in the carbodiimide compound includes dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-tert-butylcarbodiimide, di-β- Examples thereof include naphthylcarbodiimide, and among these, dicyclohexylcarbodiimide or diisopropylcarbodiimide is preferable, particularly from the viewpoint of industrial availability.

As the polycarbodiimide compound contained in the carbodiimide compound, those produced by various methods can be used. Basically, a conventional method for producing a polycarbodiimide (US Pat. No. 29419)
No. 56, JP-B-47-33279, J.P. 0
rg. Chem. 28, 2069-2075 (196
3), Chemical Review 1981, V
ol. 81 No. 4, p619-621).

Examples of the organic diisocyanate which is a synthetic raw material in the production of the polycarbodiimide compound include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and mixtures thereof. -Naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-
Phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,
A mixture of 4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate, tetracyclohexane diisocyanate Methyl xylylene diisocyanate, 2,6-diisopropylphenyl isocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate and the like can be exemplified.

In the case of the above-mentioned polycarbodiimide compound, a suitable degree of polymerization can be controlled by using a compound which reacts with the terminal isocyanate of the polycarbodiimide compound, such as monoisocyanate.

Examples of the monoisocyanate for blocking the terminal of such a polycarbodiimide compound and controlling the degree of polymerization thereof include phenyl isocyanate, tolyl isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, naphthyl isocyanate and the like. Can be exemplified.

The terminal blocking agent for blocking the terminal of the polycarbodiimide compound and controlling the degree of polymerization thereof is not limited to the above-mentioned monoisocyanate, but may be an active hydrogen compound capable of reacting with isocyanate, for example, Aliphatic,
An aromatic or alicyclic compound having an -OH group, methanol, ethanol, phenol, cyclohexanol, N-methylethanolamine, polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether; = diethylamine having an NH group;
Dicyclohexylamine; butylamine having an -NH ₂ group, cyclohexylamine; succinic acid, benzoic acid, cyclohexanoic acid having a -COOH group; ethyl mercaptan, allyl mercaptan, thiophenol having an -SH group; and a compound having an epoxy group. can do.

The decarboxylation condensation reaction of the organic diisocyanate is carried out in the presence of a suitable carbodiimidization catalyst. Examples of usable carbodiimidation catalysts include organic phosphorus compounds and organometallic compounds (general formula M- ( OR)
₄ [M is titanium (Ti), sodium (Na), potassium (K), vanadium (V), tungsten (W), hafnium (Hf), zirconium (Zr), lead (P
b), manganese (Mn), nickel (Ni), calcium (Ca), barium (Ba) or the like;
Represents up to 0 alkyl or aryl groups. Is preferable, and from the viewpoint of activity, in particular, organophosphorus compounds are preferably phosphorene oxides, and organometallic compounds are preferably alkoxides of titanium, hafnium, and zirconium.

As the above-mentioned phosphorene oxides,
Specifically, 3-methyl-1-phenyl-2-phospholene-1-oxide, 3-methyl-1-ethyl-2-oxide
Phosphorene-1-oxide, 1,3-dimethyl-2
-Phospholene-1-oxide, 1-phenyl-2-
Examples thereof include phospholen-1-oxide, 1-ethyl-2-phospholene-1-oxide, 1-methyl-2-phospholene-1-oxide, and double bond isomers thereof. Facile 3-methyl-1-phenyl-2-phospholene-1-oxide is particularly preferred.

The amount of the carbodiimide compound in the biodegradable plastic is 0.01 to 10 parts by weight, especially 0.1 to 10 parts by weight, per 100 parts of the biodegradable plastic.
When the amount is less than 0.01 part by weight, the effect of controlling the biodegradation rate is not observed, and the amount is preferably 10 parts by weight.
Exceeding the weight part may impair the properties of the biodegradable plastic.

In the present invention, the carbodiimide compound can be mixed with the biodegradable plastic by dissolving both in an organic solvent and then distilling off the organic solvent. In addition to dissolving the decomposable plastic, it is desirable to use an organic solvent which is non-polymerizable and has no active hydrogen, and specific examples thereof include chloroform and tetrahydrofuran (THF).

The mixing of the carbodiimide compound with the biodegradable plastic can be carried out by a method of melt-kneading with an extruder or a method of mixing the carbodiimide compound after the synthesis of the biodegradable plastic is completed.

The delay of the biodegradation rate of the biodegradable plastic of the present invention can be adjusted by the kind and amount of the carbodiimide compound to be compounded. The type and the amount may be determined.

The obtained biodegradable plastic composition of the present invention may further contain, if necessary, a lubricant, an inorganic or organic filler, an antioxidant, a heat stabilizer, an ultraviolet absorber, etc. Waxes, coloring agents, crystallization promoters, degradable organic substances such as starch, and the like can be used in combination.

[0040]

The present invention will be described in more detail with reference to the following examples.

Synthesis Example 1 of carbodiimide compound 4,4'-dicyclohexylmethane diisocyanate 5
90 g, cyclohexyl isocyanate 62.6 g and a carbodiimidation catalyst (3-methyl-1-phenyl-2)
-Phospholene-1-oxide) at 180 ° C.
For 48 hours to obtain 4,4′-dicyclohexylmethanecarbodiimide (degree of polymerization = 10).

Synthesis Example 2 of Carbodiimide Compound 549 g of tetramethylxylylene diisocyanate and n
-Butyl isocyanate (49.5 g) and a carbodiimidation catalyst (3-methyl-1-phenyl-2-phospholene-
5.99 g of 1-oxide) was reacted at 180 ° C. for 48 hours, and tetramethylxylylenecarbodiimide (degree of polymerization =
10) was obtained.

Synthesis Example 3 of carbodiimide compound 4,4'-dicyclohexylmethane diisocyanate 5
After reacting 00 g with 5.0 g of a carbodiimidation catalyst (tetrabutyl titanate) at 180 ° C. for 12 hours,
0.0 g of polyethylene glycol monomethyl ether was blended and reacted at 120 ° C. for 3 hours to urethanize the terminal isocyanate groups, thereby obtaining 4,4′-dicyclohexylmethanecarbodiimide-terminated polyethylene glycol (degree of polymerization = 5.5). .

Examples 1 to 3 As a biodegradable plastic, an aliphatic polyester resin whose main component is polybutylene succinate / adipate was used. The carbodiimide compound synthesized in Synthesis Examples 1 to 3 was replaced with an aliphatic polyester resin. , And kneaded with a twin-screw extruder to form a film having a thickness of 200 µm using a T-die. A JIS No. 4 dumbbell was punched from this film and used as a test piece. The test piece was placed in a 50 ° C., 90% thermo-hygrostat, and subjected to a tensile test at predetermined time intervals (tensile speed: 1).
(0 mm / min, distance between fulcrums: 55 mm), and the elongation until breaking was measured. The results are shown in Table 1 below.

Comparative Example 1 Example 1 except that no carbodiimide compound was added.
The same operation was performed. The results are shown in Table 1 below.

[0046]

[Table 1]

Examples 4 to 6 Using an aliphatic polyester resin whose main component is polylactic acid as a biodegradable plastic, the carbodiimide compound synthesized in Synthesis Examples 1 to 3 was added to the aliphatic polyester resin in a proportion of 1%. % By dry blending and kneading with a twin screw extruder, and then using a T-die to obtain a thickness of 200%.
A μm film was prepared. JIS4 from this film
No. dumbbell was punched out and used as a test piece. The test piece was placed in a 70 ° C., 70% constant temperature and humidity machine, and a tensile test was performed at predetermined time intervals to measure the tensile strength until breaking.
The results are shown in Table 2 below.

Comparative Example 2 Example 4 except that no carbodiimide compound was added.
The same operation was performed. The results are shown in Table 2 below. Note that the blank column in Table 2 indicates that the mechanical strength of the test piece has decreased to a level at which measurement is impossible.

[0049]

[Table 2]

Examples 7 to 9 The same operation as in Example 1 except that the carbodiimide synthesized in Synthesis Example 1 was dry-blended to be 0.1, 0.5 and 5% by weight based on the aliphatic polyester resin. Was done. The results are shown in Table 3 below.

[0051]

[Table 3]

Examples 10 to 12 The carbodiimide synthesized in Synthesis Example 3 was added to an aliphatic polyester whose main component was polylactic acid in an amount of 0.25 to 0.1%.
5, 0.75, and 1.0% by weight, and then kneaded with a twin screw extruder to a thickness of 20 mm from the T-die.
A 0 μm film was made. JIS from this film
No. 4 dumbbell was punched out to obtain a test piece. This test piece was
The sample was placed in a thermo-hygrostat at 0 ° C. and 90%, and a tensile test was performed at predetermined time intervals to measure the strength up to breaking. The results are shown in Table 4 below. Note that a blank column in Table 4 indicates that the mechanical strength of the test piece has decreased to a level at which measurement is impossible.

[0053]

[Table 4]

[0054]

As is clear from the above examples, the biodegradable plastic composition of the present invention comprising a biodegradable plastic and a carbodiimide compound is compared with a biodegradable plastic not containing a carbodiimide compound. As a result, its hydrolysis resistance, that is, its resistance to biodegradation due to hydrolysis is significantly improved.

Further, in the biodegradable plastic composition of the present invention, depending on the type and the amount of the carbodiimide compound,
Their hydrolysis resistance, ie the rate of biodegradation due to hydrolysis, differs.

That is, in the present invention, by blending the carbodiimide compound, the rate of biodegradation based on hydrolysis in the biodegradable plastic can be reduced, and the degree of the reduction depends on the type and amount of the carbodiimide compound. Can be adjusted.

Continued on the front page (72) Inventor Shigeichi Suzuki 1-18-1 Nishiarai Sakamachi, Adachi-ku, Tokyo Nisshin Spinning Co., Ltd. Tokyo Research Center

Claims (4)

[Claims] 1. A biodegradable plastic composition comprising a biodegradable plastic and a carbodiimide compound. 2. The compounding amount of the carbodiimide compound is 0.1%.
The biodegradable plastic composition according to claim 1, wherein the amount is from 01% to 10 parts by weight. 3. A method for controlling the biodegradation rate of a biodegradable plastic, which comprises mixing a carbodiimide compound with the biodegradable plastic. 4. A carbodiimide compound having a compounding amount of 0.1%.
The method for controlling the biodegradation rate of a biodegradable plastic according to claim 3, wherein the amount is from 0.01% to 10 parts by weight.