JP2008248029A - Process for preparing block copolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for preparing a block copolymer of an aromatic polyester with polylactic acid which excels in the rate of crystallization. <P>SOLUTION: The process for preparing the block copolymer comprises ring-opening a lactide in the presence of an aromatic polyester. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to block copolymers. More specifically, the present invention relates to a block copolymer having a repeating unit from an aromatic polyester and polylactic acid. The present invention also relates to a composition containing the block copolymer.

Many petroleum-derived plastics are light and tough, have excellent durability, can be easily and arbitrarily molded, and have been mass-produced to support our lives. However, when these plastics are disposed in the environment, they accumulate without being easily decomposed. Incineration also releases a large amount of carbon dioxide, spurring global warming.
In view of the current situation, resins made from non-petroleum raw materials, so-called plant-derived resins, have been actively studied. Currently, polylactic acid, which is being actively studied, is obtained by fermenting corn and other grains to form lactic acid, and cyclic dimerizing it, followed by ring-opening polymerization. Polylactic acid has an aliphatic carboxylic acid ester unit and is easily degraded by microorganisms. On the other hand, thermal stability is poor, and molecular weight reduction or hue deterioration is serious in molding processes exposed to high temperatures such as melt spinning, injection molding, and melt film formation.
Polylactic acid is a plastic with excellent heat resistance and balanced hue and mechanical strength in the category of aliphatic polyesters, but it is more heat resistant than petrochemical polyesters typified by polyethylene terephthalate and polybutylene terephthalate. Inferior in resistance and hydrolysis resistance. In order to overcome this situation, studies have been made on improving the performance of polylactic acid. One example is a copolymer with a petroleum aromatic polyester.

For example, Patent Document 1 teaches that polybutylene terephthalate and polylactic acid are kneaded to obtain a copolymer imparted with biodegradability. In this method, a transesterification reaction between a lactic acid unit and a terephthalic acid unit is performed. Only a copolymer that progresses and has poor crystallinity is obtained.
Patent Document 2 teaches that a block copolymer is formed when polylactic acid and polybutylene terephthalate are mixed and solid-phase polymerized. However, solid-phase polymerization requires a long time, and the block chain length is long. It is difficult to control. In addition, the weight average molecular weight of the obtained block copolymer is 20,000 to 30,000 in total, and sufficient mechanical properties cannot be expected, so that it is substantially difficult to develop into processed products such as yarns and films. Further, as time passes, transesterification proceeds, and as a result, the crystal melting point is lowered and the crystallization rate is delayed as in the production method of Patent Document 1. Such a phenomenon reduces the cycle of injection molding and reduces the heat resistance of the product. As described above, a method for producing a copolymer of an aromatic polyester and polylactic acid that can be used for industrial use has not been proposed.
JP 2006-63199 A JP 2004-285151 A

  An object of the present invention is to provide a method for producing a block copolymer of an aromatic polyester and polylactic acid having an excellent crystallization rate. Moreover, the objective of this invention is providing the composition excellent in the heat resistance containing this block copolymer.

  The present inventors obtained ring-opening polymerization of lactide in the presence of aromatic polyester to obtain a block copolymer of aromatic polyester and polylactic acid, which is a rapid crystallization characteristic of aromatic polyester. It has been found that it has speed, and the present invention has been completed. Further, the inventors have found that a composition having a high melting point and excellent heat resistance can be obtained by melt-kneading a block copolymer derived from L-lactide and a block copolymer derived from D-lactide, and the present invention has been completed.

That is, the present invention is a method for producing a block copolymer, which comprises ring-opening polymerization of lactide in the presence of an aromatic polyester. The present invention includes a block copolymer having a crystal melting point of 160 to 230 ° C. obtained by the above method. Furthermore, the molded article which consists of this block copolymer is included.
The present invention relates to a block copolymer (i) obtained by ring-opening polymerization of L-lactide in the presence of an aromatic polyester, and a block obtained by ring-opening polymerization of D-lactide in the presence of an aromatic polyester. A method for producing a composition comprising melt-kneading a copolymer (ii). The present invention includes a composition having a crystal melting point of 190 to 230 ° C. obtained by the above method. Furthermore, this invention includes the molded article which consists of this composition.

  According to the present invention, a block copolymer having a rapid crystallization rate can be produced. Moreover, according to this invention, the composition excellent in heat resistance is obtained.

Hereinafter, the present invention will be described in detail.
<Method for producing block copolymer>
(Aromatic polyester)
The aromatic polyester substantially contains a repeating unit represented by the following formula. That is, the aromatic polyester preferably contains 90 to 100 mol%, more preferably 95 to 100 mol% of repeating units represented by the following formula.

  In the formula, Ar represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, and R represents an aliphatic hydrocarbon group having 2 to 6 carbon atoms. Examples of the aromatic hydrocarbon group include a phenylene group and a naphthalene-diyl group. The aromatic hydrocarbon group may be substituted with an alkyl group having 6 to 12 carbon atoms or a halogen atom. Examples of the alkyl group having 6 to 12 carbon atoms include a methyl group, an ethyl group, and a propyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

The aromatic polyester is obtained by a polycondensation reaction of an aromatic dicarboxylic acid and a diol. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and the like. As the diol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol 1,4-cyclohexanedimethanol and the like. A combination of terephthalic acid or 2,6-naphthalenedicarboxylic acid and 1,4-butanediol or 1,6-hexanediol gives particularly good results when taking into account the appropriateness of the crystallization rate and the crystalline melting point.
The other repeating units are Ar units of aliphatic hydrocarbon groups and R units of aromatic hydrocarbon groups.

  For the polycondensation reaction of the aromatic polyester, a transesterification method in which the dimethyl ester of the aromatic dicarboxylic acid and the diol unit are reacted at their melting points or higher is suitable. As the polymerization catalyst, titanium tetra-n-butoxide, calcium acetate / germanium oxide, calcium acetate / antimony oxide, manganese acetate / antimony oxide, etc. are used, but considering the reaction rate and hue of the aromatic polyester, titanium Tetra-n-butoxide and calcium acetate / germanium oxide are preferred. As the conditions for polycondensation, a method of starting transesterification from the temperature at which the raw materials are dissolved and waiting for the theoretical amount of methanol to distill and raising the temperature and the degree of vacuum in the reaction vessel is preferred. In order to increase the reaction rate at the time of transesterification, a method of increasing the reaction temperature stepwise is also a preferred form, but care must be taken not to sublime the raw material. Ultimately, when the reaction temperature is controlled to reach the crystalline melting point of the aromatic polyester plus 30 ° C. and the degree of vacuum reaches 1 mmHg or less, satisfactory hue and molecular weight can be obtained.

The weight average molecular weight of the aromatic polyester is preferably 5,000 to 100,000, more preferably 10,000 to 50,000. When the weight average molecular weight of the aromatic polyester is not more than the above range, the crystal melting point thereof is lowered and the crystal melting point of the whole composition is lowered. On the other hand, when the amount is more than the above range, the mobility of the molecule is lowered, so that the reaction with lactide does not proceed efficiently and the intended composition cannot be obtained.
The crystalline melting point of the aromatic polyester is preferably 160 to 230 ° C, more preferably 180 to 220 ° C. If the crystalline melting point of the aromatic polyester is less than this range, the crystal melting point of the final block copolymer is lowered, and if it exceeds this range, the melting temperature is too high and is not suitable for melt kneading with lactide. The hue of is extremely deteriorated.
The half crystallization time of the aromatic polyester at 100 ° C. is preferably 1 to 60 seconds, more preferably 5 to 30 seconds. When the half crystallization time is longer than 60 seconds, it does not contribute to the rapid crystallization of the block copolymer.

(Lactide)
Lactide is L-lactide or D-lactide. Lactide preferably has a low content of optical isomers. For example, the content of D-lactide and DL-lactide in L-lactide is preferably 0% or more and less than 1%, more preferably 0% or more and less than 0.5%, and even more preferably 0% or more and less than 0.1%.

(Ring-opening polymerization)
The block copolymer can be produced by ring-opening polymerization of lactide using the OH terminal of the aromatic polyester as an initiator. The ring-opening polymerization can be performed by heating the aromatic polyester and lactide in the reaction vessel in the presence of a metal catalyst.
The amount of lactide to be added is 5 to 300 parts by weight, preferably 20 to 250 parts by weight, more preferably 50 to 100 parts by weight, based on 10 parts by weight of the aromatic polyester. When the amount of lactide deviates from an appropriate amount, no block copolymer is produced, and only poly-L-lactic acid or poly-D-lactic acid is produced.
The proportion of polylactic acid units in the block copolymer is preferably 5 to 95%, more preferably 20 to 80%. When the polylactic acid unit is outside the above range, the substantial physical properties are not different from polylactic acid or the aromatic polyester itself.

The metal catalyst is preferably a compound containing at least one metal element selected from the group consisting of alkaline earth metals, rare earth metals, third-period transition metals, aluminum, germanium, tin and antimony. Examples of alkaline earth metals include magnesium, calcium, and strontium. Examples of rare earth elements include scandium, yttrium, lanthanum, and cerium. Examples of transition metals in the third period include iron, cobalt, nickel, zinc, and titanium.
Metal catalysts can be added as carboxylates, alkoxides, aryloxides or enolates of β-diketones of these metals. In view of polymerization activity and hue, tin octylate, titanium tetraisopropoxide, and aluminum triisopropoxide are particularly preferable. The amount of the catalyst is preferably 0.001 to 0.1 parts by weight, more preferably 0.003 to 0.01 parts by weight with respect to 100 parts by weight of lactide. The additive atmosphere is preferably an inert gas atmosphere such as nitrogen or argon.

The reaction time is preferably 30 minutes to 5 hours, preferably 1 hour to 3 hours. The reaction temperature is preferably 150 to 250 ° C, more preferably 170 to 230 ° C. When the reaction time and temperature are outside the above ranges, the reaction between the aromatic polyester and lactide does not proceed sufficiently, or the hue of the resulting block copolymer deteriorates.
The reaction can be carried out using a conventionally known production apparatus such as a vertical reaction vessel equipped with a high-viscosity stirring blade such as a helical ribbon blade. The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon. By adopting such a method, a block copolymer having a high crystallization speed and excellent heat resistance, which is an object of the present invention, can be obtained.
The crystal melting point of the block copolymer is preferably 160 to 230 ° C.

<Method for producing composition>
A composition having a high melting point can be obtained by melt-kneading the block copolymer derived from L-lactide obtained by the method of the present invention and the block copolymer derived from L-lactide.
That is, the present invention is obtained by ring-opening polymerization of block copolymer (i) obtained by ring-opening polymerization of L-lactide in the presence of aromatic polyester and D-lactide in the presence of aromatic polyester. And a block copolymer (ii), which is melt-kneaded.
The kneading temperature is preferably 200 to 260 ° C, more preferably 220 to 240 ° C. When the two are kneaded out of the above temperature range, the kneading becomes non-uniform or the molecular weight of the composition is extremely lowered.

The ratio of the block copolymer (i) to the block copolymer (ii) is preferably 30/70 to 70/30, more preferably 40/60 to 60/40, as the former / the latter. If it is out of this range, the composition may not be sufficiently crystallized or a stereocomplex crystal may not be completely formed. The composition contains stereocomplex crystals. The crystal melting point of the composition is preferably 190 to 230 ° C.
In the block copolymer or composition of the present invention, conventional additives such as a plasticizer, an antioxidant, a light stabilizer, an ultraviolet absorber, a heat stabilizer, a lubricant, Release agents, various fillers, antistatic agents, flame retardants, foaming agents, fillers, antibacterial / antifungal agents, nucleating agents, dyes, colorants including pigments, and the like can be included as desired.

  Using the block copolymer or composition of the present invention, an injection molded product, an extrusion molded product, a vacuum / pressure molded product, a blow molded product, a film, a sheet nonwoven fabric, a fiber, a cloth, a composite with other materials, an agricultural material, Fishery materials, civil engineering / architectural materials, stationery, medical supplies or other molded articles can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In the examples, physical properties were measured by the following methods.
(1) Weight average molecular weight (Mw):
For the weight average molecular weight (Mw), GPC-11 manufactured by Shodex was used, 50 mg of the composition was dissolved in 5 ml of chloroform, and developed with chloroform at 40 ° C. The weight average molecular weight (Mw) was calculated as a polystyrene equivalent value (2) Crystal melting point (Tm), Crystal melting enthalpy (ΔHm):
A sample piece of 5 mg was placed in a dedicated aluminum pan and measured using a differential scanning calorimeter (DSC2920) manufactured by TA Instruments. Tm was determined from a chart in which the temperature was raised from 20 to 250 ° C. at 20 ° C./min. The crystal melting enthalpy was calculated by the crystal melting point appearing at 150 ° C. or higher and lower than 190 ° C. appearing on the chart and the area of the region surrounded by the baseline.
(3) Half crystallization time:
The half crystallization time was measured using a half crystallization time measuring device manufactured by Kotaki Seisakusho, which has a crossed polarizer and an oil bath. Specifically, about 5 mg of a sample piece is sandwiched between cover glasses and melted at 250 ° C., and this is poured into an oil bath at 100 ° C. located between two orthogonal polarizing plates, and polarized light accompanying crystal growth. The time course of dissolution was recorded and the time required for it to reach its maximum multiplied by 0.5 was determined as the half crystallization time.
(4) Copolymer composition ratio:
Copolymerization composition ratio is JEOL nuclear magnetic resonance apparatus JNM-EX270 spectrometer in heavy chloroform, aromatic polyester-derived benzene ring peak (7-8.5 ppm), and polylactic acid-derived quadruple peak It calculated from the area ratio of (5.10-5.20 ppm).

[Example 1]
(Manufacture of aromatic polyester)
Under a nitrogen stream, 190 parts by weight of 1,4-butanediol and 194.2 parts by weight of dimethyl terephthalate were charged from a raw material charging port of a polymerization reaction vessel equipped with a cooling distillation pipe. This was melted at 190 ° C., and 2.5 × 10 ⁻⁴ parts by weight of tetrabutoxytitanium was added as a catalyst to conduct a transesterification reaction for 2 hours. Further, the reaction temperature was reduced stepwise to 250 ° C. over 2 hours and the inside of the reaction vessel was reduced to 0.5 mmHg to complete the polymerization reaction while distilling off 1,4-butanediol. Table 1 shows the Mw, semi-crystallization time, and crystal melting point of the resulting polybutylene terephthalate.
(Ring-opening polymerization)
10 parts by weight of polybutylene terephthalate was placed in another polymerization reaction vessel set at 220 ° C. and dissolved. Subsequently, 50 parts by weight of L-lactide and 0.01 part by weight of tin octylate were added to carry out copolymerization for 3 hours. After completion of the copolymerization, the inside of the reaction vessel was depressurized to 1.0 mmHg to remove excess L-lactide.
Finally, the block copolymer was discharged as an amorphous strand from the discharge port of the reaction vessel, and was cut into pellets while cooling with water. Table 2 shows the Mw, Tm, ΔHm and half-crystallization time of the block copolymer, and Table 3 shows the copolymer composition ratio.

[Example 2]
50 parts by weight of D-lactide and 0.01 parts by weight of tin octylate were added to 10 parts by weight of polybutylene terephthalate obtained in Example 1, and copolymerization was carried out for 3 hours under the same conditions as in Example 1. Table 2 shows the Mw, Tm, ΔHm and half-crystallization time of the block copolymer, and Table 3 shows the copolymer composition ratio.

[Example 3]
10 parts by weight of the block copolymer (1) obtained in Example 1 and 10 parts by weight of the block copolymer (2) obtained in Example 2 were put into a Toyo Koki Kneader Labo Plast Mill 50C150, 240 It knead | mixed for 10 minutes under nitrogen stream at ° C. Table 2 shows the Mw, Tm, ΔHm, and semi-crystallization time of the obtained composition.

[Example 4]
(Manufacture of aromatic polyester)
Polyhexamethylene terephthalate was produced in the same manner except that 190 parts by weight of 1,4-butanediol in Example 1 was changed to 250 parts by weight of 1,6-hexanediol. Table 1 shows Mw of polyhexamethylene terephthalate, semi-crystallization time, and crystal melting point.
(Ring-opening polymerization)
50 parts by weight of L-lactide and 0.01 parts by weight of tin octylate were added to 10 parts by weight of polyhexamethylene terephthalate, and copolymerization was performed for 3 hours under the same conditions as in Example 1 to obtain a block copolymer (4). Table 2 shows the Mw, Tm, ΔHm and half-crystallization time of the block copolymer (4), and Table 3 shows the copolymer composition ratio.

[Example 5]
Block copolymer (5) was prepared by adding 50 parts by weight of D-lactide and 0.01 parts by weight of tin octylate to 10 parts by weight of polyhexamethylene terephthalate obtained in Example 4 and copolymerizing for 3 hours under the same conditions as in Example 4. Got. Table 2 shows the Mw, Tm, ΔHm and half-crystallization time of the block copolymer (5), and Table 3 shows the copolymer composition ratio.

[Example 6]
10 parts by weight of the block copolymer (4) obtained in Example 4 and 10 parts by weight of the block copolymer (5) obtained in Example 5 were charged into a Toyo Koki Kneader Labo Plast Mill 50C150 at 240 ° C. It knead | mixed for 10 minutes under nitrogen stream. Table 2 shows the Mw, Tm, ΔHm, and semi-crystallization time of the obtained composition.

[Comparative Example 1]
100 parts by weight of L-lactide and 0.15 parts by weight of stearyl alcohol were charged from a raw material charging port of a polymerization reaction vessel equipped with a cooling distillation pipe under a nitrogen stream. Subsequently, the inside of the reaction vessel was purged with nitrogen five times, and L-lactide was melted at 190 ° C. When L-lactide was completely melted, 0.005 part by weight of tin 2-ethylhexanoate was added from the raw material charging port, and polymerized at 190 ° C. for 1 hour. Finally, excess L-lactide was devolatilized and poly-L-lactic acid was discharged from the reaction vessel. Table 2 shows the Mw, Tm, and semicrystallization time of the obtained poly-L-lactic acid.

  Since the block copolymer of the present invention has a high crystallization rate, it can be melt-molded into yarns, films and various molded articles.

Claims (11)

A method for producing a block copolymer, comprising ring-opening polymerization of lactide in the presence of an aromatic polyester. The method according to claim 1, wherein the lactide is L-lactide or D-lactide. The method according to claim 1, wherein the aromatic polyester has a crystal melting point of 160 to 230 ° C. The method according to claim 1, wherein the aromatic polyester has a semicrystallization time at 100 ° C of 1 to 60 seconds. The process according to claim 1, wherein the proportion of polylactic acid units in the block copolymer is 5 to 95%. The process according to claim 1, wherein the proportion of polylactic acid units in the block copolymer is 20 to 80%. A block copolymer having a crystal melting point of 160 to 230 ° C obtained by the method according to any one of claims 1 to 6. A block copolymer (i) obtained by ring-opening polymerization of L-lactide in the presence of an aromatic polyester, and a block copolymer (ii) obtained by ring-opening polymerization of D-lactide in the presence of an aromatic polyester And kneading and kneading the composition. A composition having a crystal melting point of 190 to 230 ° C. obtained by the method according to claim 8. A molded article comprising the block copolymer according to claim 7. A molded article comprising the composition according to claim 9.