JPH09100345A - Polylactic acid copolymer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable resin composition having transparency and markedly excellent toughness and impact resistance. SOLUTION: This polylactic acid copolymer is a block copolymer prepared by bonding a polylactic acid segment (A) to an aromatic polyester segment (B) and a polyalkylene ether segment (C) in a weight ratio [A/(B+C)] of 99/1 to 50/50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a resin composition having biodegradability and transparency, and having extremely excellent toughness and impact resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyethylene has been used as a molding material.
Polypropylene, polyester, polyamide, etc. are used, and the consumption is increasing year by year. Accordingly, the amount of waste after use is increasing. These wastes are currently being incinerated or buried in the soil. But,
These are not biodegradable and remain for a long time when left to stand. Considering future consumption, current treatment methods have limitations, and the development of new treatment methods is urgently needed.

[0003] As one of new treatment methods, there is a method of collecting a recyclable resin, separating it, and reusing it. However, in reality, it is difficult to recover, and high technology and expensive equipment are required to separate the resin. In order to reuse them, there is a disadvantage that the use is limited. Therefore, recently, as another treatment method, a method of decomposing the resin by the action of microorganisms existing in soil or water has been proposed, and various biodegradable polymers suitable for this purpose have been developed. Among these biodegradable polymers, short-chain aliphatic polyesters represented by polylactic acid are mentioned as those having high strength and transparency. However, since these polymers have low toughness and impact resistance, molded products are easily broken and their use is limited.

[0004]

The present inventors have arrived at the present invention as a result of extensive studies on a resin composition having biodegradability and transparency and having improved toughness while maintaining strength.

[0005]

Means for Solving the Problems That is, the present invention provides a polylactic acid segment (A), an aromatic polyester segment (B) and a polyalkylene ether segment (C).
Is a block copolymer in which the polylactic acid segment (A) and the aromatic polyester segment (B) and the polyalkylene ether segment (C) have a weight ratio (A / B + C) of 99/1 to 50. / 50
Is achieved by a polylactic acid copolymer. Here, the segment means a portion of a polymer molecular chain.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The first component (segment) (A) constituting the block copolymer of the present invention is polylactic acid, which can be obtained by a known means such as a method of directly dehydrating and polycondensing lactic acid, or a method of ring-opening polymerization of lactide. You can For polylactic acid, L-form, D-form,
There are three types of DL (racemic) optical isomers, all of which are good, and a copolymer of these optical isomers is also used as a component of the copolymer of the present invention. However, from the viewpoint of physical properties, it is preferable that the content of L-form is 95% or more.

Second component of the block copolymer of the present invention
The component (segment) (B) is an aromatic polyester. Examples of the acid component of the aromatic polyester forming the segment (B) include terephthalic acid, isophthalic acid, 2,6
-Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid and the like.

Examples of the diol component of the aromatic polyester constituting the segment (B) include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanediol, cyclohexanedimethanol, octanediol,
Nonanediol, decanediol, dimerdiol,
Aliphatic and alicyclic compounds such as bis- (p-hydroxyphenyl) methane [bisphenol F], bis- (p-hydroxyphenyl) propane [bisphenol A], bis- (p-hydroxyphenyl) sulfone [bisphenol S] Aromatic diols may be mentioned.

Of these dicarboxylic acids and diols, the segment (B) of the copolymer of the present invention is formed by using one having an aromatic nucleus in one of the dicarboxylic acid and the diol. For example, examples of preferable diols to be combined with terephthalic acid include linear diols having 4 to 12 carbon atoms such as butanediol and hexanediol. Examples of preferable diols to be combined with isophthalic acid include linear diols having 2 to 12 carbon atoms such as ethylene glycol and butanediol.

The third component (segment) (C) of the block copolymer of the present invention is a polyalkylene ether. As the polyalkylene ether, those having an alkyl group having 2 to 12 carbon atoms such as polyethylene glycol, polypropylene glycol, polybutylene ether, polyhexane ether, and polyoctane ether and copolymers thereof are widely used, and particularly polyethylene glycol and Polybutylene ether is preferably used. The molecular weight of the polyalkylene ether used as a raw material is not particularly limited, but is usually 500 or more, preferably 1,
The range of 000 to 50,000, more preferably 2,000 to 20,000 is recommended.

The aromatic polyester segment (B)
And the polyalkylene ether segment (C) have a weight ratio (B / C) of 10/90 to 90/10, preferably 20/80 to 80/20, and more preferably 30/70 to 70. The range is / 30. The greater the amount of polyalkylene ether segment (C), the higher the impact resistance of the block copolymer of the present invention.

The block copolymer of the present invention is obtained by melt-polymerizing a block copolymer comprising an aromatic polyester segment (B) and a polyalkylene ether segment (C) having a melting point of 230 ° C. or less and lactide in the presence of a catalyst. Can be easily obtained. In this method, unless the molecular weight of the binary block copolymer comprising the aromatic polyester segment (B) and the polyalkylene ether segment (C) is higher than a certain level, the copolymer of the present invention (tertiary block) having a sufficient molecular weight is obtained. I can't get anything. That is, the binary block copolymer to be copolymerized with lactide has a molecular weight of 10,000 or more, preferably 20,000 or more, more preferably 30,000 to
It is better to use 150,000. By copolymerizing this binary block copolymer with lactide, the ternary block copolymer of the present invention can be obtained. The molecular weight is not particularly limited, but if the molecular weight is too large, the melt viscosity becomes too high, which makes manufacturing and molding difficult. Therefore, in general, it is recommended that the molecular weight is 50,000 to 500,000, preferably 80 to 300,000, and more preferably 100 to 250,000.

Further, a binary consisting of a polylactic acid segment (A) each having an active group such as a hydroxyl group or a carboxyl group at its terminal, an aromatic polyester segment (B) and a polyalkylene ether segment (C) having a melting point of 230 ° C. or less. The block copolymer is reacted with a polyfunctional compound such as dicarboxylic acid chloride, dicarboxylic acid anhydride, dicarboxylic acid, diamine, diisocyanate and the like, and each component is bonded to form the ternary block copolymer of the present invention. You can also get it. In this case, a joint, such as an aliphatic compound or a phthalic acid compound, should be selected such that a small amount of another component is contained in the joint of each segment, but essentially retains the excellent characteristics of the block copolymer of the present invention. Is desirable.

The weight ratio (A / B + C) of the three main components constituting the block copolymer of the present invention, namely the polylactic acid segment (A) and the aromatic polyester segment (B) and the polyalkylene ether segment (C), is
It is necessary to be 99/1 to 50/50. That is, the weight ratio of polylactic acid as the main component is 99 to 50%,
It is preferably 95 to 55%. That is, if the sum (B + C) of the weight ratios of the aromatic polyester segment (B) and the polyalkylene ether segment (C) is too small (less than 1%), the toughness and impact resistance improving effect is poor and too large ( If it exceeds 50%), problems such as a decrease in transparency occur.

If necessary, pigments, antioxidants, plasticizers, antistatic agents, matting agents, deterioration inhibitors, fluorescent whitening agents, ultraviolet absorbers, and ultraviolet stabilizers are added to the polylactic acid copolymer of the present invention. Agents, slip agents, nucleating agents, metal powders, inorganic fillers, carbon black, thickeners, viscosity stabilizers and the like can be added at any ratio. The addition method is arbitrary. Blended oils can also be added to increase the adhesion of the additive to the resin surface.

[0016]

INDUSTRIAL APPLICABILITY The polylactic acid copolymer of the present invention has excellent biodegradability and transparency, and has improved flexibility, toughness, and impact resistance, so that it can be used in containers, plates, tubes, and various types of products. Parts, other various molded products, fibers, ropes, monofilaments, knits, woven fabrics, non-woven fabrics, films, sheets, etc.
Very useful for a wide range of applications.

[0017]

EXAMPLES The present invention will be described below with reference to examples. Evaluation method of resin composition 1. Mechanical Properties Evaluation Tensile strength, tensile elongation, bending strength, and Izod impact strength are J
It measured by the method according to IS method. 2. Biodegradability evaluation Molded into film (stretching ratio 2.8 times, thickness about 10
μ), and this was buried in activated sludge, and the weight change rate (%) between before burying and after burying for 3 months was measured.

EXAMPLE 1 8.2 parts by weight of dimethyl terephthalate, 3.6 parts by weight of 1,4-butanediol, 27 parts by weight of polybutylene glycol having a molecular weight of 2000, and 1,3,5-as an antioxidant.
Trimethyl-2,4,6-tris (3,5-di-ter
t-dibutyl-4-hydroxybenzyl) benzene 0.
5 parts by weight of the mixture was placed in a reaction vessel equipped with a stirrer, 1
After dissolving under stirring at 60 ° C. under a nitrogen stream, 0.01 parts by weight of tetrabutoxy titanate was added to 170 to 2
After heating to 10 ° C. to distill off 90% or more of the theoretical amount of methanol, the temperature is set to 250 ° C. and the pressure is set to 0.5 mmHg over 1 hour to carry out polymerization for 3 hours to obtain a polycondensate (P1). It was

Next, 100 parts by weight of L-lactide and 10.0 parts by weight of the polycondensate (P1) obtained above were placed in a reaction vessel equipped with a stirrer and dissolved under stirring at 190 ° C. under a nitrogen stream. Then, 0.10 parts by weight of tin 2-ethylhexanoate was added and polymerized for 20 minutes to obtain polylactic acid segment (A).
And a ternary block copolymer (P2) consisting of an aromatic polyester segment (B) and a polybutylene glycol segment (C) was obtained. Then, this polymer (P2) was washed with methyl ethyl ketone to remove residual lactide (confirmed amount: 10%), and then its physical properties were measured.

Example 2 140 parts by weight of dimethyl terephthalate, 79 parts by weight of 1,4-butanediol, 150 parts by weight of polyethylene glycol having a number average molecular weight of 1500, and 1,1 as an antioxidant.
A mixture of 1.5 parts by weight of 3,5-trimethyl-2,4,6-tris (3,5-di-tert-dibutyl-4-hydroxybenzyl) benzene was placed in a reaction vessel equipped with a stirrer and heated to 160 ° C. After dissolving under nitrogen flow with stirring, add 0.03 parts by weight of tetrabutoxy titanate, 1
Heat to 70-210 ℃ and add 90% of theoretical amount of methanol.
After the above distillation, the temperature was set to 250 ° C. and the pressure was set to 0.5 mmHg over 1 hour to carry out polymerization for 3 hours to obtain a polycondensate (P3).

Next, 100 parts by weight of L-lactide and 10.0 parts by weight of the polycondensate (P3) obtained above were placed in a reaction vessel equipped with a stirrer and dissolved with stirring at 190 ° C. under a nitrogen stream. Then, 0.06 parts by weight of tin 2-ethylhexanoate was added and polymerized for 20 minutes to obtain polylactic acid segment (A).
And a ternary block copolymer (P4) consisting of an aromatic polyester segment (B) and a polyethylene glycol segment (C) was obtained. Then, this polymer (P4) was washed in the same manner as in Example 1 and its physical properties were measured.

Example 3 61.0 parts by weight of L-lactide and the polymer of Example 1 (P
45.0 parts by weight of 1) was placed in a reaction vessel equipped with a stirrer and dissolved under stirring in a nitrogen stream at 190 ° C., and then 2
-A ternary block composed of polylactic acid segment (A) and polycondensate of aromatic polyester segment (B) and polybutylene glycol (C) by adding 0.10 part by weight of tin ethylhexanoate and polymerizing for 20 minutes. A polymerized polymer (P5) was obtained. Then, this polymer (P5) was washed in the same manner as in Example 1 and its physical properties were measured.

Comparative Example 1 100 parts by weight of L-lactide was placed in a reaction vessel equipped with a stirrer, dissolved at 190 ° C. under a nitrogen stream with stirring, and then 0.06 parts by weight of tin 2-ethylhexanoate was added. And polymerized for 20 minutes to obtain a polylactic acid homopolymer (P6). Then, this polymer (P6) was washed in the same manner as in Example 1 and its physical properties were measured.

Comparative Example 2 44.0 parts by weight of L-lactide and the polymer of Example 1 (P
60.0 parts by weight of 1) was placed in a reaction vessel equipped with a stirrer, dissolved at 190 ° C. under a nitrogen stream with stirring, and then 2
-A ternary block composed of polylactic acid segment (A) and polycondensate of aromatic polyester segment (B) and polybutylene glycol (C) by adding 0.10 part by weight of tin ethylhexanoate and polymerizing for 20 minutes. A polymerized polymer (P7) was obtained. Then, this polymer (P7) was washed in the same manner as in Example 1 and its physical properties were measured.

Comparative Example 3 110 parts by weight of L-lactide and the polymer of Example 1 (P
0.50 part by weight of 1) was placed in a reaction vessel equipped with a stirrer, dissolved at 190 ° C. under a nitrogen stream with stirring, and then 2
-A ternary block composed of polylactic acid segment (A) and polycondensate of aromatic polyester segment (B) and polybutylene glycol (C) by adding 0.10 part by weight of tin ethylhexanoate and polymerizing for 20 minutes. A polymerized polymer (P8) was obtained. Then, this polymer (P8) was washed in the same manner as in Example 1 and its physical properties were measured.

Comparative Example 4 The physical properties of the polymer (P1) obtained in Example 1 were measured.

Comparative Example 5 The physical properties of the polymer (P3) obtained in Example 2 were measured.

The physical properties of the resins produced in the examples and comparative examples are summarized in Table 1.

[0029]

[Table 1]

The polylactic acid copolymers obtained in Examples 1 and 2 have improved toughness and impact resistance while maintaining the original transparency of polylactic acid, and have biodegradability.
Satisfactory results were obtained. The polylactic acid copolymer obtained in Example 3 was also slightly white, but the impact resistance was significantly improved, which was satisfactory.

Comparative Example 1 is polylactic acid, which has a low impact resistance and is extremely brittle. In Comparative Example 2 and Comparative Example 3, the weight ratio (A / B + C) of the polylactic acid segment (A), the aromatic polyester segment (B) and the polyalkylene ether segment (C) was 40, respectively.
A polylactic acid copolymer having a composition outside the scope of the present invention of 60/60 and 99.5 / 0.5. 40/60 has impact resistance but is white opaque and biodegradable. And that of 99.5 / 0.5 were both unsatisfactory with the characteristics that were not so different from those of the polylactic acid of Comparative Example 1.
Comparative Example 4 and Comparative Example 5 are binary copolymers composed of the aromatic polyester segment (B) and the polyalkylene ether segment (C) which compose the polylactic acid copolymer of the present invention. However, it has low tensile strength, is opaque, and is not biodegradable, making it unsuitable.

Front Page Continuation (72) Inventor Yasuhiro Fujii 1 Nishinokyo Kuwabaracho, Nakagyo-ku, Kyoto City Shimadzu Corporation Sanjo Factory

Claims (2)

[Claims] 1. A block copolymer comprising a polylactic acid segment (A), an aromatic polyester segment (B) and a polyalkylene ether segment (C) bonded to each other, and the polylactic acid segment (A) and the aromatic ring. The weight ratio (A / B + C) of the polyester segment (B) and the polyalkylene ether segment (C) is 99 /
The polylactic acid copolymer is characterized by being 1 to 50/50. 2. An aromatic polyester segment (B) and a polyalkylene ether segment (C) are bonded together, and the weight ratio (B / C) of these is from 10/90 to 90.
/ 10, the melting point of which is 230 ° C. or lower, and a block copolymer having a hydroxyl group at at least one molecular end is reacted with lactide in a molten state in the presence of a catalyst. Method for producing polymer.