JP2002338791A - Hydrolysis-resistant resin composition and molded part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrolysis-resistant resin composition showing an excellent strength, flexibility and resistance to hydrolysis, and a molded part. SOLUTION: The resin composition is prepared by adding 0.1 to 10 pts.wt. carbodiimide group-containing resin as an additive to a raw material wherein mainly a polylactic acid polymer (A) is mixed with an aliphatic polyester carbonate (B). The hydrolysis-resistant resin composition mainly comprises a polylactic acid polymer (A) mixed with an aliphatic polyester carbonate (B) at a mix ratio (weight ratio) of from 94/6 to 30/70, and further contains from 0.1 to 10 pts.wt. carbodiimide group-containing resin as an additive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrolysis-resistant resin composition containing a carbodiimide group-containing resin as an additive to a biodegradable resin mainly comprising polylactic acid and an aliphatic polyester carbonate, and which has particularly excellent strength and flexibility. It has excellent properties and excellent hydrolysis resistance.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protecting the natural environment, molded articles made of a biodegradable resin that decomposes in the natural environment have been demanded, and studies on naturally degradable resins such as aliphatic polyesters have been actively conducted. .

One example is polylactic acid. Since polylactic acid has a relatively high melting point of 150 to 180 ° C. and excellent transparency, it is expected as a molding material. However, polylactic acid has a drawback that, while having high strength due to its rigid molecular structure, is inferior in impact resistance and brittle.

[0004] Aliphatic polyesters other than polylactic acid are generally excellent in flexibility and impact resistance, but have a lower melting point of 60 to 110 ° C, a glass transition temperature below room temperature and a higher crystallinity than polylactic acid. It is opaque and has low strength. Thus, any biodegradable resin currently on the market,
At present, it is presently impossible to obtain a molded article having a disadvantage in terms of mechanical properties when used alone, and improvement is desired. In JP-A-9-272794, JP-A-9-111107, etc.,
It has been reported that blending polylactic acid with an aliphatic polyester other than polylactic acid can provide a material that is opaque and has excellent impact resistance.

[0005] However, these raw materials, polylactic acid and aliphatic polyester, both have low resistance to hydrolysis, and decompose more rapidly at higher temperatures and humidity, so that they cannot be used in many cases, such as products used in greenhouses. Was.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydrolysis-resistant resin composition which has both excellent strength and flexibility and excellent hydrolysis resistance.

[0007]

Means for Solving the Problems In order to solve such problems, the present inventors have conducted intensive studies and as a result, the polylactic acid-based polymer (A) and the aliphatic polyester carbonate (B) were mainly mixed. It has been found that the above object can be achieved when the raw material further contains 0.1 to 10 parts by weight of a carbodiimide group-containing resin as an additive.

That is, in the present invention, the polylactic acid-based polymer (A) and the aliphatic polyester carbonate (B) are mainly composed of (A) / (B) in a mixing ratio (weight ratio) of 94/6 to 30 /.
No. 70, and 0.1 to 10 parts by weight of a carbodiimide group-containing resin as an additive.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, polylactic acid, aliphatic polyester carbonate and the like used in the present invention will be described step by step.

[0010] In the present invention, polylactic acid is a polymer consisting essentially of monomer units derived from L-lactic acid and / or D-lactic acid. Here, “substantially” means
This means that other monomer units not derived from L-lactic acid or D-lactic acid may be contained as long as the effects of the present invention are not impaired.

As the method for producing polylactic acid, any known polymerization method can be employed. The most commonly known method is a method in which lactide which is an anhydrous cyclic dimer of lactic acid is subjected to ring-opening polymerization (lactide method). However, lactic acid may be directly subjected to condensation polymerization.

When the polylactic acid consists only of monomer units derived from L-lactic acid and / or D-lactic acid, the polymer is crystalline and has a high melting point. Furthermore, L-lactic acid, D-
Ratio of monomer units derived from lactic acid (abbreviated as L / D ratio)
By changing the crystallinity, the crystallinity and melting point can be freely adjusted, so that the practical characteristics can be controlled according to the application.

Further, to the extent that the properties of polylactic acid are not impaired,
Other hydroxycarboxylic acids may be copolymerized.

Further, for the purpose of increasing the molecular weight, a small amount of a chain extender, for example, a diisocyanate compound, an epoxy compound, an acid anhydride, a peroxide and the like can be used. The weight average molecular weight of the polymer is from 50,000 to 1,000,000
A range of 0 is preferred. If the ratio is less than the above range, mechanical properties and the like are not sufficiently exhibited, and if the ratio is higher than the range, processability is poor.

The aliphatic polyester carbonate (B) in the present invention is a number average molecular weight of 10,000 obtained by reacting an aliphatic dibasic acid and / or a derivative thereof, an aliphatic dihydroxy compound and / or a hydroxycarboxylic acid compound. A carbonate unit content obtained by reacting the following aliphatic polyester oligomer with a carbonate compound is at least 5 mol%, the weight average molecular weight is at least 100,000, and the temperature is 19
The melt viscosity at 0 ° C and a load of 60 kg is 2,000 to 5
It is characterized by having a melting point of 70 to 180 ° C. at 0000 poise.

The process for producing an aliphatic polyester carbonate according to the present invention comprises a first step of obtaining an aliphatic polyester oligomer from an aliphatic dibasic acid and / or a derivative thereof and an aliphatic dihydroxy compound and / or a hydroxycarboxylic acid compound; It comprises a second step of reacting an aliphatic polyester oligomer with a carbonate compound to obtain an aliphatic polyester carbonate.

The first step is carried out in the presence of a catalyst at a temperature of 100 to 100.
At 250 ° C., while removing water and excess dihydroxy compound produced as a by-product of the reaction, the number average molecular weight was 10,000.
This is a step of producing a polyester oligomer of 0 or less. It is preferable to reduce the pressure to 300 mmHg or less for the purpose of promoting the reaction.

The second step is a step in which the polyester oligomer obtained in the first step is reacted with an aliphatic carbonate compound to obtain a high molecular weight compound.
The reaction is carried out at 50 to 250 ° C., preferably 200 to 220 ° C., to remove by-product hydroxy compounds accompanying the reaction. At a temperature of 150 ° C. or lower, a sufficient reaction rate cannot be obtained. At a temperature of 250 ° C. or higher, the polymerization reaction can proceed rapidly, but the polymer may be colored, which is not preferable. Depending on the boiling point of the aliphatic carbonate compound used in the reaction, it is necessary to carry out the reaction under pressure at the initial stage of the reaction. In the latter half of the reaction, it is preferable to gradually adjust the degree of reduced pressure as needed to finally reduce the pressure to 3 mmHg or less.

The content of carbonate units in the aliphatic polyester carbonate can be controlled to a desired ratio by controlling the amount of terminal hydroxyl groups of the aliphatic polyester oligomer. If the carbonate unit content is too large,
The melting point of the aliphatic polyester carbonate obtained is low, and a polymer having practical heat resistance cannot be obtained. On the other hand, when the carbonate unit content increases, the degradability by microorganisms increases. Therefore, the carbonate unit content, it is preferable to have an appropriate biodegradability, and it is preferable to be an amount that can achieve practical heat resistance, in the present invention, the carbonate unit content in the aliphatic polyester carbonate, It is preferably at least 5 mol% or more, usually 5 to 30 mol%, and particularly preferably 7 to 25 mol%.

As the aliphatic dibasic acid used in the production of the aliphatic polyester carbonate of the present invention, succinic acid is used as an essential component, and in addition, for example, oxalic acid, malonic acid, glutaric acid, adipic acid, suberin acid,
Sebacic acid, dodecanoic acid, azelaic acid, etc. can be used in combination. The above aliphatic dibasic acids may be esters or acid anhydrides thereof.

The aliphatic dihydroxy compound used for producing the aliphatic polyester carbonate of the present invention is 1,1.
4-butanediol is used as an essential component, and for example, ethylene glycol, trimethylene glycol, propylene glycol, 1,3-butanediol, pentanediol, hexanediol, octanediol, neopentylglycol, cyclohexanediol, cyclohexane Dimethanol or the like can be used in combination as appropriate.

Examples of the hydroxycarboxylic acid compound used in the present invention include lactic acid, glycolic acid, β-hydroxybutyric acid, hydroxypivalic acid, hydroxyvaleric acid and the like. These can also be used as derivatives such as esters and cyclic esters. .

These aliphatic dibasic acids, aliphatic dihydroxy compounds and hydroxycarboxylic acid compounds can be used alone or as a mixture, and can be combined in any desired manner. And a melting point with a high degree of tightness that can realize practical heat resistance. Therefore, in the present invention,
It is necessary to contain 1,4-butanediol as an aliphatic dihydroxy compound and succinic acid as an aliphatic dibasic acid in an amount of 50 mol% or more.

Specific examples of the carbonate compound used for producing the aliphatic polyester carbonate of the present invention include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m
-Diaryl carbonates such as cresyl carbonate, and aliphatic carbonate compounds such as dimethyl carbonate, diethyl carbonate, diisopropyl carbonate, dibutyl carbonate, diamyl carbonate, and dioctyl carbonate, but are not limited thereto. . In addition to the above-mentioned carbonate compound composed of the same type of hydroxy compound, an asymmetric carbonate compound or a cyclic carbonate compound composed of a different type of hydroxy compound can also be used.

The mixing ratio of polylactic acid and aliphatic polyester carbonate needs to be 94/6 to 30/70 by weight. When the content of polylactic acid is 95% by weight or more, the obtained material is generally hard and brittle, and particularly under high temperature and high humidity, the crystallization of polylactic acid proceeds, so that the material is more vulnerable to impact. If the content of polylactic acid is less than 30% by weight, the resulting material is too soft and cannot be used for applications requiring rigidity.

The aliphatic polyester carbonate is superior in hydrolysis resistance to polylactic acid and other aliphatic polyesters. As the amount of the aliphatic polyester carbonate increases, a resin composition having excellent stability under high temperature and high humidity can be obtained. can get.

Further, by introducing a crosslinked structure mutually, the compatibility between the aliphatic polyester carbonate and the polylactic acid can be increased, and the appearance of the molded article can be beautiful. For example, it is possible to mutually introduce a crosslinked structure by adding about 0.001 to 10 parts by weight of an oxazoline group-containing compound, a peroxide, and a carbodiimide group-containing resin described below. In addition, as a method for introducing a crosslinked structure, a conventionally known method can be used.

By including 0.1 to 10 parts by weight of a carbodiimide group-containing resin as an additive, its hydrolysis resistance can be further improved, thereby suppressing a decrease in molecular weight and a change in physical properties under high temperature and high humidity. When the amount is less than 0.1 part by weight, the effect of inhibiting hydrolysis is low. When the amount is more than 10 parts by weight, not only the coloring of the resin is increased, but also the resin is easily gelated, which is not preferable.

Next, a method for producing the hydrolysis-resistant resin composition of the present invention will be described.

First, the method of mixing polylactic acid, aliphatic polyester carbonate, and a carbodiimide group-containing resin as an additive are not particularly limited, but those capable of continuous treatment are industrially advantageous and preferred. For example,
Two or more types of pellets may be mixed at a predetermined ratio, directly charged into a hopper of an extruder, melted, and immediately formed into various molded products. Alternatively, both components may be melt-mixed, then pelletized once, and then, if necessary, melt-molded.

Similarly, polylactic acid and aliphatic polyester carbonate are separately melted by an extruder or the like, and these are mixed at a predetermined ratio by a static mixer and / or a mechanical stirrer, and may be molded immediately. May be used. Mixing by mechanical stirring such as an extruder may be combined with a static mixer.

For uniform mixing, the method of once pelletizing is more preferable, but in the case of the melt mixing method, it is necessary to substantially prevent deterioration, alteration, and copolymerization of the polymer due to transesterification. Therefore, it is preferable to mix at a temperature as low as possible within a short time.

The melt extrusion temperature is appropriately selected in consideration of the melting point and the mixing ratio of the resin to be used.
The range is 0 to 250 ° C.

The hydrolysis-resistant composition according to the present invention may contain various modifiers, fillers such as calcium carbonate, lubricants, ultraviolet absorbers, antioxidants, stabilizers, pigments, colorants, In addition to various additives such as filler, antistatic agent, release agent, plasticizer, fragrance, antibacterial agent, transesterification catalyst,
It can be modified by adding various monomers, coupling agents, terminal treating agents, other resins, wood flour, starch and the like. Further, other general-purpose polymers and the like may be added as long as they do not care about biodegradability.

The hydrolysis-resistant resin composition of the present invention is most suitable as a raw material for agricultural materials for a house which is required to have stability especially at high temperature and high humidity, but is not limited thereto. Extruded products, vacuum molded products, compression molded products,
Blow molded products, films (sheets), fibers (multifilaments, monofilaments), nonwoven fabrics, nets, ropes,
It can be used for various applications such as laminates, containers, foams, and various parts.

[0036]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these contents.

In the following examples, the weight-average molecular weight (Mw) of the polymer was calculated in terms of polystyrene by GPC analysis, and the glass transition temperature and melting point were measured by a scanning differential calorimeter (DSC) at a heating rate of 10 ° C. It is a value measured in / min.

In this example, an experiment was conducted using the following raw materials. <Polylactic acid-based polymer (A1)> Poly-L-lactic acid Lacty # 9400 manufactured by Shimadzu Corporation Mw = 150,000, glass transition temperature 60 ° C, melting point 1
71 ° C. <Aliphatic polyester carbonate (B1)> Polybutylene succinate carbonate Eupec 350 Mw = 179,000 manufactured by Mitsubishi Gas Chemical, glass transition temperature −30 ° C., melting point 105 ° C. <Additive AD1> Carbodilite group-containing resin Nisshinbo Carbodilite T02

Example 1 A polylactic acid-based polymer (A1), an aliphatic polyester carbonate (B1), and a carbodiimide group-containing resin (AD1) were each made into an absolutely dry state by vacuum drying, and then a mixing ratio (A1) was obtained. / (B1) / (AD1)
= 70/30/1, and mixed with a V-type blender.
The raw material was continuously supplied to a 30 mm co-directional twin screw extruder kneader set at 10 ° C., melt-extruded, made into strands, and pelletized to prepare main raw materials.

After the main raw material was made absolutely dry by vacuum drying, it was put into an injection molding machine set at a temperature of 190 to 210 ° C. to produce a JIS tensile test piece. Thereafter, the obtained tensile test piece was stored in a thermo-hygrostat set at a temperature of 50 ° C. and a humidity of 95%, and was taken out with time to measure the strength and the molecular weight.

(Comparative Examples 1 and 2) Polylactic acid and aliphatic polyester carbonate were mixed at a predetermined ratio and evaluated in exactly the same manner as in Example 1.

Table 1 shows the results of comparative evaluation of strength and hydrolysis resistance. Table 2 shows the results of comparative evaluation of flexibility.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

As shown in Tables 1 and 2, the hydrolysis-resistant resin composition and the molded article according to the present invention have excellent strength and flexibility and also have excellent hydrolysis resistance. It has something to have.

Claims (1)

[Claims] 1. A polylactic acid-based polymer (A) and an aliphatic polyester carbonate (B) are mainly mixed in a mixing ratio (weight ratio) of (A) / (B) of 94/6 to 30/70. And a hydrolysis-resistant resin composition and a molded article further containing 0.1 to 10 parts by weight of a carbodiimide group-containing resin as an additive.