JP2000044659A - Block copolymer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a block copolymer useful as a sanitary product and capable of suppressing a reduction of a molecular weight by hydrolysis, providing a high durable molded product and improving a hydrolysis-resistance by incorporating a specific segment into a polylactic acid-based polymer. SOLUTION: This copolymer comprises (A) 100 pts.wt. of a segment comprising a polymer having >=10 mol.% of a repeating unit of the formula and (B) 0.1 to 50 pts.wt. of a segment derived from polyhydrocarbon. The copolymer is pref. obtained by polymerizing any one lactic acid-based compound selected from the group consisting of lactide, lactic acid and a lower alkyl lactate or by polymerizing the lactic acid-based compound with a compound capable of copolymerizing with the lactic acid-based compound, in the presence of a polymerization catalyst and a component B comprising at least one hydroxy group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a plastic material compatible with a recycling system. In particular,
The present invention relates to a polylactic acid-based plastic material excellent in chemical recycling (monomer reduction) and biorecycling (biodegradation), and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, biodegradable plastics decomposed by enzymes and microorganisms have been actively developed due to environmental destruction caused by plastic waste. Recently, Applied and Environmental
Microbiology [H. Pranamuda et al., Applied
and Environmental Microbiology, 63 , 1637-1640 (19
97)], it has been found that polylactic acid is also degraded by microorganisms, and the application of polylactic acid as a biodegradable plastic material is expected. By the way, it is known that a polylactic acid-based polymer containing polylactic acid as a main component has a property of being easily hydrolyzed and absorbed in a living body, and, combined with its extremely high safety, a surgical suture. It is already widely used as a material.

Polylactic acid is a plastic material having excellent chemical recyclability, which is not only absorbable in a living body but also easily reduced to lactide as a cyclic monomer when heated to a certain temperature or higher. -3
No. 09863.

[0004] However, the polylactic acid and the polylactic acid-based polymer are easily hydrolyzed, which is an excellent feature in the above specific applications. When applied to general-purpose applications that require a certain degree of durability as a material, this causes a reduction in the durability of the product, and rather causes a problem.

For example, sanitary articles such as disposable diapers, body fluid-absorbing pads, sanitary napkins, panty liners, and the like are commonly used in the form of disposables in order to enhance their sanitary properties. The use of biodegradable plastic materials as raw materials for its structural members has been studied in order to enable composting. Regarding the use of polylactic acid and polylactic acid-based polymers for sanitary articles, Japanese Patent Application Laid-Open No.
No. 136982 and JP-A-9-291163. However, the polylactic acid and the polylactic acid-based polymer have not yet been put to practical use because of their rigidity or hydrolyzability.

Conventionally, as seen in the above-mentioned surgical sutures, the ease of hydrolysis of polylactic acid-based polymers has been regarded as a feature thereof, and the mechanism of hydrolysis of fibrous polylactic acid-based polymers has been considered. Is a journal of controlled release [CG Pittet al., Journal of Contro
lled Release, 4 , 283-292 (1987)], it is speculated that autocatalytic random decomposition in the amorphous phase proceeds.

For stabilizing the hydrolysis of polylactic acid-based polymers, Japanese Patent Application Laid-Open No. Hei 5-103825 discloses a hygroscopic polyhydroxy compound and calcium lactate. It is intended to stabilize the hydrolysis by the selective moisture absorption effect in the medium, and at present, the stabilization of the hydrolysis in the open system has not yet been sufficiently stabilized.

[0008]

As described above, in order to develop a polylactic acid-based polymer as a chemically recyclable and biorecyclable plastic material, the durability (stability) of the molded product (product) is high. Must be practical. That is, the technical problem of the present invention is:
It is an object of the present invention to improve the hydrolysis resistance of a polylactic acid-based polymer, and to provide a polylactic acid-based polymer having an improved hydrolysis resistance to give a molded article having high durability, and molding the same. To provide a molded member and a sanitary article.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by incorporating a specific segment into a polylactic acid-based polymer, a decrease in molecular weight due to hydrolysis is suppressed. They have found that they can do this and have completed the present invention.

That is, the present invention provides the following repeating unit

[0011]

Embedded image

A block copolymer comprising a segment comprising a polymer having at least 10 mol% and a segment derived from a polyhydrocarbon, wherein the polyhydrocarbon-derived segment is contained in 100 parts by weight of the segment having the repeating unit. Is a block copolymer comprising 0.1 to 50 parts by weight of a segment.

In the present invention, by introducing a segment derived from polyhydrocarbons into a polymer having the above-mentioned repeating unit, a decrease in molecular weight due to hydrolysis is suppressed while maintaining its properties.

[0014] The mechanism of action that produces such effects is not always clear, but is presumed to be generally as follows. That is, a segment comprising a polymer having the above repeating unit (hereinafter, also simply referred to as polylactic acid segment) and a segment derived from polyhydrocarbons (hereinafter, also simply referred to as polyhydrocarbon segment) are generally incompatible. It is. Therefore, the segments perform microscopic phase separation. At this time, a polylactic acid segment having a large intermolecular cohesive force due to having a polar group easily forms an aggregate phase such as a crystal phase, and a polyhydrocarbon segment having a small intermolecular cohesive force forms an amorphous phase as a matrix. Cheap. When the block copolymer of the present invention has such a higher-order structure, the amorphous polyhydrocarbon segment, which is the site of the initial hydrolysis, has an initial hydrolysis due to its hydrolysis resistance and hydrophobicity. It is assumed that decomposition is suppressed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer having the repeating unit, which is a segment constituting the block copolymer of the present invention, is, as apparent from its structure, D-lactide and L-lactide.
-Lactide and DL-lactide (hereinafter collectively also referred to simply as lactide), and dehydration weight of L-lactic acid and D-lactic acid (hereinafter collectively referred to simply as lactic acid). A polymer having a basic structure of a condensate or a dealcoholized polycondensate of a lactic acid ester such as ethyl lactate, methyl lactate, or isopropyl lactate. Among these, a ring-opening addition polymer of L-lactide is preferably used because the mechanical properties of the polymer are particularly good. Further, the polylactic acid segment has a repeating unit derived from a compound copolymerizable with any one of lactide, lactic acid, and lactic acid ester in the segment, as long as the polymer has a plurality of repeating units. May be.

In order for the polylactic acid segment to exhibit a biodegradable function or the like, it is necessary that the repeating unit represented by the above structural formula contains at least 10 mol%. Therefore, the compound copolymerizable with lactide or the compound copolymerizable with lactic acid or lactic acid ester may contain less than 90 mol% as a repeating unit. Further, in order to improve the hydrolysis resistance of the polylactic acid segment itself, in order to form a partial crystalline phase by a plurality of continuous polylactic acid segments of the repeating unit, the above copolymerizable compound is repeated. It is preferable that the content is 50 mol% or less as a unit. Further, in order to exhibit a high degree of crystallinity by the polylactic acid segment and further improve the hydrolysis resistance, it is preferable to contain the copolymerizable compound in a content of 10 mol% or less as a repeating unit.

Examples of the compound copolymerizable with the lactic acid compound include β-propiolactone, β-butyrolactone, diketene, pivalolactone, δ-valerolactone, ε-caprolactone, glycolide, and 1,4-dioxepane-2. Cyclic ester compounds such as -one and 1,3-dioxan-2-one; cyclic ether compounds such as ethylene oxide and propylene oxide; hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; Examples thereof include alkyl esters of acids such as methyl, ethyl and isopropyl.

Although the molecular weight of the polylactic acid segment of the present invention is not particularly limited, it must be at least a molecular weight sufficient for forming an aggregate phase. Generally, the molecular weight is 10,000 to
It is appropriately selected from the range of 800,000, more preferably from 20,000 to 500,000.

The method for producing the polylactic acid segment in the present invention is not particularly limited. As described above, ring-opening addition polymerization of lactide alone or a mixture of lactide and a compound copolymerizable with lactide, Such methods as dehydration polycondensation with hydroxycarboxylic acids or lactic acid ester alone or dealcoholization polycondensation of lactic acid esters with esters of hydroxycarboxylic acids are preferably employed. The dehydration polycondensation reaction and the dealcoholization polycondensation reaction are usually carried out independently, but they can be carried out simultaneously if the conditions are adjusted.

These polymerizations are carried out by heating in the presence of a generally known initiator or a polymerization catalyst as described below.

The segment derived from polyhydrocarbons used in the present invention is not particularly limited as long as it is a polymer segment of a compound consisting essentially of carbon and hydrogen.

Examples of the polymer segment composed of carbon and hydrogen include a polymer segment of an olefin compound such as ethylene, propylene, 1-butene, 1-hexene, 4-methylpentene and isobutylene; and a polymer segment of a diene compound such as butadiene and isoprene. Merging segment; copolymer segment of olefin compound and diene compound; hydrogenation of part or all of unsaturated bonds of polymer segment of diene compound or copolymer segment of olefin compound and diene compound And the like. Among these polyhydrocarbon segments, a polymer segment of a diene compound is more preferably used in view of the biodegradability characteristics described below.

The polyhydrocarbon segment in the present invention needs to have at least one reactive group in the segment in order to bond with the polylactic acid segment. Examples of the reactive group include a hydroxyl group, a carboxyl group, an amino group, a thiol group, an unsaturated bond, an isocyanate group, an acid anhydride structure, and an epoxy group. These reactive groups can be easily introduced by using an initiator, a comonomer, a chain transfer agent, or a polymerization terminator capable of deriving these reactive groups during the production of polyhydrocarbons.

The segment derived from such polyhydrocarbons, that is, the polyhydrocarbon segment is
Expression of hydrolysis resistance based on its hydrophobicity is an important function. The segment molecular weight is 5 in terms of the effect of inhibiting hydrolysis.
It is desirably at least 00, preferably at least 1,000. Further, it is desirable that the segment molecular weight is 1,000,000 or less, preferably 100,000 or less, from the viewpoint of ease of handling at the time of production and processing and molding. When the molecular weight of the polyhydrocarbon segment is less than 500,
When the polylactic acid segment is drawn into the aggregate phase to reduce its crystallinity, or when the hydrophobicity of the amorphous phase based on the aggregation of the polyhydrocarbon segment and the resulting hydrolysis inhibition effect are insufficient. There is.

The polyhydrocarbon segment in the copolymer of the present invention is known to be biodegradable.
For example, it is known that polyisoprene has the same structure as natural rubber. Polybutadiene having a molecular weight of 2350 can be decomposed by microorganisms.
Doi, Suzuki, Fukuoka, Agricultur reported to Agricultural and Biological Chemistry
al and Biological Chemistry, 48 (3), 621-625 (198
Four)}. Regarding the biodegradability of polyolefin,
It has been reported in the Report of the Fermentation Research Institute that a polyethylene model compound having a molecular weight of about 800 is degraded by microorganisms. A. Tsuchii, T. Suzuki, and S. Fukuoka, R
eport of the Fermentation Research Institute, No. 5
5 , 35-40 (1980)｝.

From the viewpoint of such a biodegradable function, when a molded member or sanitary article comprising the block copolymer of the present invention is used for an application suitable for biorecycling (biodegradation), polyhydrocarbon is used. The molecular weight of the segment is
The molecular weight range according to each molecular structure is appropriately selected. For example, in the case of polybutadiene, its segment molecular weight is 500 to 20,000, more preferably 1,000.
The range is from 10,000 to 10,000. In the case of a saturated hydrocarbon, 500 to 10,000, more preferably 800 to 5
000.

The block copolymer of the present invention is a so-called block and / or graft copolymer in which the polylactic acid segment and the polyhydrocarbon segment are combined. Polylactic acid resin and polyhydrocarbons are mixed as independent molecules without binding
When blended, the mechanical strength is not developed, the blooming of polyhydrocarbons after molding occurs, and the polyhydrocarbons completely separated from the polylactic acid resin are macroscopically impaired. Uniformity is likely to be apparent.

In the block copolymer of the present invention, the composition ratio of the polylactic acid segment and the polyhydrocarbon segment can be any composition ratio depending on the application, but the formation of the polylactic acid segment crystal phase and the development of mechanical strength For 100 parts by weight of the polylactic acid segment, 0.1 to 50 parts by weight, preferably 0.2 to 20 parts by weight, more preferably 0.5 to 10 parts by weight of the polyhydrocarbon segment is suitable. . If the polyhydrocarbon segment exceeds 50 parts by weight, it tends to be difficult to form a crystal phase of the polylactic acid segment and to exhibit mechanical strength, and if the polyhydrocarbon segment is less than 0.1 part by weight, the effect of inhibiting hydrolyzability will be reduced. Not always enough.

The polylactic acid segment and the polyhydrocarbon segment are bonded to each other by a covalent bond via a bonding group. A typical structure of the block copolymer of the present invention in which the polylactic acid segment, the polyhydrocarbon segment and the bonding group for bonding both segments are combined is shown below.

[0030]

Embedded image

(Where D is a polylactic acid segment, H is a polyhydrocarbon segment, and L ₁ and L ₂ are 2 to 2)
A hexavalent linking group, 1 is 1 to 10, m is 1 to 10, n
Is an integer of 0 to 10; p, q and r are integers of 0 to 2;
Are at least one. The bonding groups L ₁ and L ₂ in the above structural formula are used not only as bonding groups between the polylactic acid segment and the polyhydrocarbon segment but also as bonding groups between the polyhydrocarbon segments.

As the divalent to hexavalent linking group, a known linking group can be used without any particular limitation, but a linking group which suppresses the hydrolysis of the polylactic acid segment and promotes the development of hydrophobicity of the polyhydrocarbon segment. A group is more preferably used.

Specific examples of the preferably used bonding groups include ether-based bonding groups, thioether-based bonding groups, ester-based bonding groups, thioester-based bonding groups, amide-based bonding groups, urethane-based bonding groups, and carbonate-based bonding groups. And a bonding group containing a silicon atom, and an aliphatic or aromatic hydrocarbon group having 2 to 6 of these bonding groups alone or as a mixture. Among these bonding groups, an ether-based bonding group, an ester-based bonding group, and a urethane-based bonding group are particularly preferably used because of ease of synthesis and the like. In the present invention, these bonding groups are generic terms including not only the specified bond itself but also a group containing one or more specified bonds as specifically shown below.

The bonding group is formed by a method using a low molecular weight bonding agent having an appropriate reactive group as described later, or by using a polylactic acid segment precursor and / or polyhydrocarbons before bonding. There is a method of forming directly by a reactive group already contained in the polymer.

Examples of the ether-based linking group include oxygen atoms alone, and divalent ether-based groups such as oxyethyleneoxy, oxypropyleneoxy, oxytrimethyleneoxy, oxytetramethyleneoxy, oxyethyleneoxyethyleneoxy, and oxyhexamethyleneoxy. Linking group: a tri- to hexa-valent ether-based binding group derived from a tri- to hexahydric alcoholic binder such as glycerin, trimethylolpropane, trimethylolethane, pentaerythritol and various sugars.

Examples of the ester-based linking group include divalent ester-based linking groups such as succinate, adipate and sebacate derived from a binder such as an acid chloride compound; 1,3,5-pentanetricarboxylate;
1,3,5-benzenetricarboxylate, 1,2,2
Examples thereof include a trivalent to hexavalent ester-based bonding group such as 3,4-butanetetracarboxylate.

Examples of the urethane-based binding group include divalent to hexavalent urethane-based binding groups derived from isocyanate binders such as hexamethylene diisocyanate and tolylene diisocyanate.

As represented by the above structural formula, the block copolymer of the present invention is not a random copolymer in which polymer chains are mixed in monomer units, but a block copolymer or a graft in which polymer chains are bonded in segment units. It is a copolymer or a copolymer in which a block structure and a graft structure coexist. In the present invention, these are collectively simply referred to as a block copolymer.

The method for producing the block copolymer of the present invention is not particularly limited, and a generally known production method can be used.

A preferred production method is to polymerize lactide or lactide and a compound copolymerizable with the lactide in the presence of a polyhydrocarbon having a polymerization reactive group such as a hydroxyl group or an epoxy group. A method of directly bonding, a method of directly bonding a polyhydrocarbon having a hydroxyl group and a polylactic acid segment precursor having a terminal carboxyl group by an ester bond,
Polyhydrocarbons having a hydroxyl group and a polylactic acid segment precursor having a terminal hydroxyl group, for example, using a binder having a plurality of acid chloride groups, isocyanate groups, halogens, or a binder having a cyclic acid anhydride structure Ester-based bonding group, urethane-based bonding group, method of bonding via an ether-based bonding group, a polyhydrocarbon having a carboxyl group and a polylactic acid segment precursor having a terminal carboxyl group, for example, a bond having a plurality of hydroxyl groups A hydroxyl group or a carboxyl group is introduced into polyhydrocarbons having a double bond by hydrosilylation, and then a silicon atom is bonded to the polyhydrocarbons having a double bond by using the above method. Via a linked bonding group, an ester-based bonding group or a urethane-based bonding group How to bind Te, methods and the like to perform the dealcoholization polycondensation of dehydrating polycondensation or lactate lactate in the presence of poly hydrocarbon compound having a hydroxyl group or a carboxyl group.

Among these production methods, lactide or lactide and a compound copolymerizable with the lactide are directly polymerized in the presence of a polyhydrocarbon having a polymerization-reactive group such as a hydroxyl group or an epoxy group. A method of bonding and a method of performing dehydration polycondensation of lactic acid or dealcoholization polycondensation of a lactic acid ester in the presence of a polyhydrocarbon having a hydroxyl group or a carboxyl group are more preferably used in terms of ease of synthesis. More preferably, the above-described production method is particularly preferably used in terms of ease of adjusting the molecular weight. Here, the polymerization reactive group includes a hydroxyl group, an epoxy group, a carboxyl group, a double bond and the like. For example, when lactide is polymerized in the presence of a polyhydrocarbon having a hydroxyl group and directly bonded as a polylactic acid segment, the bonding group becomes an ester group.

As described above, in the production of the block copolymer of the present invention, as one of the segments, a polyhydrocarbon having at least one hydroxyl group, a carboxyl group, a double bond, or the like in the molecule, Derivatives thereof synthesized by reacting hydrocarbons with a binder are preferably used. Polyhydrocarbons having at least one hydroxyl group, carboxyl group, or double bond in such a molecule are commercially available,
It is readily available. In addition, commercially available polyhydrocarbons can also be produced by a generally known synthesis method.

Examples of generally available polyhydrocarbons having at least one hydroxyl group, carboxyl group, or double bond in the molecule include hydroxyl-containing polybutadiene, hydroxyl-containing polyisoprene, hydroxyl-containing styrene-butadiene rubber, Examples include heavy bond-containing polyisobutylene, terminal double bond poly (isobutylene-co-isoprene), and hydroxyl group-containing polyhydroxypolyolefin obtained by hydrogenating hydroxyl group-containing polybutadiene.

Those obtained by further introducing a small amount of a different atom, such as a nitrogen atom, an oxygen atom or a chlorine atom, into these polyhydrocarbons can also be used as the polyhydrocarbons of the present invention. Examples of the heteroatom-containing polyhydrocarbons include hydroxyl group-containing acrylonitrile butadiene rubber, carboxyl group-containing acrylonitrile butadiene rubber, double bond-containing acrylonitrile butadiene rubber, amino group-containing acrylonitrile butadiene rubber, and halogen-containing chloroprene rubber.

Among the above polyhydrocarbons,
Hydroxy group-containing polybutadiene, hydroxyl group-containing polyisoprene, hydroxyl group-containing polyhydroxypolyolefin, and the like are more preferably used in terms of availability and ease of synthesis.

Hereinafter, lactide in the presence of a polyhydrocarbon having a polymerization reactive group such as a hydroxyl group or an epoxy group, or a copolymer of lactide and the lactide, which is a preferred method for producing the block copolymer of the present invention, will be described. A method of polymerizing a possible compound (hereinafter referred to as lactide or the like) and directly bonding the same will be described in detail.

The polymerization is carried out, if necessary, in the presence of a polymerization catalyst. As the polymerization catalyst, a known polymerization catalyst is used without any particular limitation. Usually, periodic table IA group, IVA group, IV
The catalyst comprises at least one metal or metal compound selected from the group consisting of Group B and Group VA. Suitable polymerization catalysts include tin (II) octoate,
Organic tin compounds such as tin lactate, tin dilaurate and tin dioleate; titanium compounds such as tetrapropyl titanate; zirconium compounds such as zirconium isopropoxide; antimony compounds such as antimony trioxide are preferred. used.

Among these polymerization catalysts, organotin compounds are preferred catalysts from the viewpoint of catalytic activity.
Regarding the ring-opening polymerization catalysis of L-lactide using a compound having a hydroxyl group as an initiator, Macromolecules [A.
J. Nijenhuis et al., Macromolecules, 25,6419-6424
(1992)], and is preferably used in the case where lactide or the like is polymerized in the presence of a polyhydrocarbon having at least one hydroxyl group and directly bonded.

A technique for polymerizing lactide using an organic compound having a hydroxyl group as an initiator in the presence of an esterification catalyst or a transesterification catalyst such as tin (II) octylate is disclosed in Japanese Patent Application Laid-Open No. 3-139361. ing.
However, the technology disclosed herein utilizes the function of an organic compound having a hydroxyl group as an initiator, and the compound having a hydroxyl group used is also ethylene glycol,
It is a hydrophilic low molecular weight compound such as diethylene glycol and glycerin. The polymer produced is also at room temperature (25 ° C)
Liquid or waxy low molecular weight polymer, intended to improve tactile smoothness and tightness as a coating for surgical filaments. There is no disclosure about the block copolymer of the present invention, and no suggestion or disclosure about suppression of hydrolysis. After all, sufficient high molecular weight and mechanical properties for the purpose of developing as a chemical recyclable and biorecyclable plastic material of the present invention,
It is completely different from a block copolymer for expressing durability (stability).

The polymerization conditions for polymerizing lactide and the like in the presence of the above-mentioned polyhydrocarbons having a polymerization reactive group differ depending on the type of polymerization catalyst. The amount is 0.001 to 1 mol%, preferably 0.01 to 1 mol%, based on lactide or the like.
0.3 mol%, the polymerization temperature is 120 ° C. to 250 ° C., preferably 140 ° C. to 180 ° C., 140 ° C. to 160 ° C. to suppress racemization and decomposition and coloring of lactide, and the polymerization reaction time is
It is appropriately selected within a range of 100 hours.

The polymerization time is appropriately selected according to the polymerization temperature and the type of the polymerization catalyst. In general, the higher the temperature, the shorter the polymerization reaches an equilibrium state. The pressure at the time of the polymerization may be any mode from a reduced pressure to a pressurized state, but the incorporation of water and the like into the polymerization system is not preferable because it leads to a decrease in molecular weight. In general, a polymerization reaction is performed under a pressurized state by filling with an inert gas such as nitrogen gas, and after the polymerization reaches an equilibrium, the pressure is reduced to distill off unreacted lactide and the like. Remove the polymer.

The above polymerization can be carried out without a solvent, but a solvent may be used if necessary. Hydrocarbon solvents such as dimethylbenzyl ether, benzylphenyl ether and diphenyl ether are preferably used as the solvent. A preferred embodiment of the solvent-free polymerization is a polymerization method in an extruder cylinder. If the preferred embodiment is specifically illustrated, in an extruder, a polyhydrocarbon having a hydroxyl group, a polymerization catalyst, lactide, and the like are supplied, and polymerization is performed by heating while slowly rotating a screw, thereby forming a vent port. After the unreacted lactide and the like are distilled off under reduced pressure, the block copolymer of the present invention is extruded from a die.

The molecular weight of the block copolymer of the present invention is such that the weight average molecular weight is 2 to 150 as the sum of the polylactic acid segment, the polyhydrocarbon segment and the bonding group.
10,000, preferably 50,000 to 1,000,000, more preferably 1
The range of from 100,000 to 800,000 is preferable from the viewpoint of easiness of synthesis, moldability, physical properties of a molded article, and the like. If the weight average molecular weight is less than 20,000, molding is difficult in many cases, and the strength of the molded body is not often exhibited.

The structure of the block copolymer of the present invention can be confirmed by analytical means such as size exclusion chromatography (GPC), nuclear magnetic resonance spectrum (NMR), and differential scanning calorimetry (DSC). The GPC analyzes whether the copolymer is a copolymer or a blend from a weight average molecular weight, a number average molecular weight, and a GPC profile. From NMR, the composition ratio of the polylactic acid segment and the polyhydrocarbon segment is quantitatively evaluated.In addition, based on the splitting or shifting of the characteristic peak of each segment, whether the copolymer is a random copolymer, a block copolymer, or a blend. Can be evaluated. By combining these analytical means, the structure of the block copolymer of the present invention can be confirmed.

The evaluation of the hydrolyzability of the block copolymer of the present invention is generally carried out by evaluating the decrease in molecular weight using GPC. Can be In the case of the block copolymer of the present invention, the hydrolysis proceeds inside the polylactic acid segment.
The decomposition is catalyzed by a carboxyl group generated by hydrolysis and proceeds autocatalytically. In particular, in the range where the composition ratio of the polylactic acid segment is high, for example, 90 wt% or more, using the value of the weight average molecular weight determined by GPC, the rate constant (kd) of reduction of the molecular weight by the autocatalytic hydrolysis is calculated as follows. Obtained from the formula.

[0056]

(Equation 1)

(Where Mwt is the weight average molecular weight after t time, and Mw0 is the initial weight average molecular weight.) The rate constant (kd) for decreasing the molecular weight in the above equation is:
The smaller the molecular weight, the slower the molecular weight decreases, and thus the better the durability. When the hydrolysis rate is evaluated using the equation, it is generally more efficient to perform the accelerated test in a heated and humidified state.

By adding an alkaline earth metal carbonate to the block copolymer of the present invention, the hydrolysis resistance is further improved and the stability is improved.

The alkaline earth metal carbonate used in the present invention is not particularly limited, and magnesium carbonate, calcium carbonate, barium carbonate, strontium carbonate and the like are preferably used. Among these alkaline earth metal carbonates, magnesium carbonate or calcium carbonate which is easily available and has low toxicity is particularly preferably used.

The above-mentioned calcium carbonate includes boraxite,
Examples include heavy calcium carbonate obtained by pulverizing natural ores such as leopardite, aragonite, limestone, marble, and whitening, and light calcium carbonate produced by blowing carbon dioxide into lime milk. The above magnesium carbonate is produced by heating magnesium carbonate crystals such as anhydrous magnesium carbonate, magnesium carbonate monohydrate, magnesium carbonate trihydrate, magnesium carbonate pentahydrate, or a suspension of magnesium carbonate. And a basic salt having the composition represented by the following formula, that is, magnesium hydroxycarbonate and the like.

[0061]

Embedded image

(In the formula, x is an integer of 3 to 5 and y is an integer of 3 to 7.) The above alkaline earth metal carbonates may be used alone or in combination.

The amount of the alkaline earth metal carbonate added to the block copolymer is not particularly limited, and the processability of the block copolymer composition after the addition, the mechanical properties of the molded product after the process, and the What is necessary is just to determine suitably in consideration of a use etc. The effect of stabilizing the block copolymer in the present invention increases with an increase in the amount of alkaline earth metal carbonate added to a certain extent, and then saturates. Therefore, even if the alkaline earth metal carbonate is added in a large amount, the effect corresponding to the added amount is not always obtained. Since the alkaline earth metal carbonate also acts as a filler, it is a matter of course that a large amount of the alkaline earth metal carbonate may be added when such an effect is expected. However, when the effect as a filler is not required, from the viewpoint of a stabilizing effect and prevention of excessive use of the alkaline earth metal carbonate, 0.1 parts of the alkaline earth metal carbonate is added to 100 parts by weight of the block copolymer. It is preferable to add in an amount of from 50 to 50 parts by weight, more preferably from 0.1 to 10 parts by weight.

In the present invention, in order to improve the photodegradability of the block copolymer, it is preferable to add an ultraviolet absorber.

If the UV absorber is specifically exemplified, 2
-(3,5-di-t-butyl-4-hydroxybenzyl)
Bis-n-butylmalonate (1,2,2,6,6-
Pentamethyl-4-piperidyl), 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, 2- (3,5-di-tert-butyl-2-)
Hydroxyphenyl) benzotriazole, 2- (2 ′
Phenol derivatives such as -hydroxy-5'-t-octylphenyl) benzotriazole, 2- (2-hydroxy-3-t-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2-hydroxybenzophenone; bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-
(Hydroxyethyl) -4-hydroxy-2,2,6,6
-Tetramethylpiperidine polycondensate, bis-succinic acid (2,2,6,6-tetramethyl-4-piperidinyl)
Ester, 1- [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} ethyl] -4- {3- (3,5-di-t-butyl-4- (Hydroxyphenyl) propionyloxy} -2,2,6
Piperidine derivatives such as 6-tetramethylpiperidine; Among them, phenol derivatives are more preferably used because of their high photodegradation suppressing effect.

The amount of the ultraviolet absorber to be added varies depending on the type of the member formed by molding the block copolymer composition, but is in the range of about 0.01 to 10 parts by weight per 100 parts by weight of the block copolymer. Is typical, and a range of about 0.05 to 5 parts by weight is more preferable.

In the present invention, in addition to the alkaline earth metal carbonate, a neutral saccharide and / or an inorganic compound having a dehydrating ability are added in order to suppress the decomposition of the block copolymer during heating such as melt molding. Is preferably added.

The neutral saccharide used is not particularly limited, but monosaccharides, oligosaccharides such as disaccharides, trisaccharides and the like, and derivatives thereof are preferably used because of their easy handling.

Specific examples of suitably used neutral sugars include pentoses such as arabinose, xylose, ribose, lyxose, ribulose and xylulose; glucose, galactose, mannose, talose, fructose, sorbose, tagatose, psicose, Hexoses such as fucose and rhamnose; kojibiose,
Nigerose, maltose, isomaltose, sophorose, laminaribiose, cellobiose, gentiobiose, melibiose, turanose, trehalose, isotrehalose, and other disaccharides; maltotriose, cellotriose, manninotriose, panose, gentianose, raffinose, meletitose Trisaccharides such as ose; tetrasaccharides such as stachyose, cellotetraose and scorodose; and sorbitol, mannitol,
And sugar alcohols such as dulcitol and ribitol. Among these neutral sugars, monosaccharides, disaccharides, and sugar alcohols of pentoses and hexoses are more preferably used from the viewpoint of easy availability.

The amount of the neutral saccharide to be added to the block copolymer is not particularly limited. However, considering the stabilizing effect, processability, physical properties of the final molded product, and the like, the block copolymer 10
It is preferable to add 0.1 to 10 parts by weight with respect to 0 parts by weight.

The inorganic compound having dehydration ability used in the present invention is not particularly limited as long as it does not decompose itself to the block copolymer. The compounds are used without any restrictions.

Examples of the inorganic compounds preferably used include molecular sieves such as molecular sieves 3A, molecular sieves 4A and molecular sieves 5A; sulfates such as sodium sulfate, magnesium sulfate and calcium sulfate; activated alumina; Oxides such as calcium oxide and magnesium oxide; and chlorides such as calcium chloride and ammonium chloride. Among these, molecular sieves, sulfates, and activated alumina are preferably used from the viewpoints of effects and ease of handling.

The amount of the inorganic compound having dehydration ability to be added to the block copolymer is not particularly limited. However, the processability of the block copolymer composition after the addition, the mechanical properties of the molded product after the process, and the In consideration of the use and the like, the amount is preferably in the range of 0.1 to 50 parts by weight based on 100 parts by weight of the block copolymer.

When the above-mentioned alkaline earth metal carbonates, ultraviolet absorbers, or neutral sugars and / or inorganic compounds having a dehydrating ability are added, they may be used alone or in combination. good. Hereinafter, alkaline earth metal carbonates, ultraviolet absorbers, neutral saccharides, and inorganic compounds having a dehydrating ability are collectively referred to simply as additives.

In the present invention, the method of adding the above additives to the block copolymer is not particularly limited. However, from the viewpoint of the effect, it is desirable that the above-mentioned additive is finally substantially uniformly dispersed microscopically in the block copolymer.
As a method for achieving such dispersion, for example, a known addition method generally used for adding various additives to a thermoplastic resin can be adopted.

That is, the above-mentioned additives are dry-blended to a powdery or pelletized block copolymer using a mixer such as a super mixer, and the blended product is melt-kneaded using a Banbury mixer, an extruder or the like. Melt-kneading method, after copolymerization of lactide, etc., heat removal of unreacted monomer, etc., method of directly adding and mixing additives to molten block copolymer, dissolving block copolymer in solvent For example, a method in which an additive is added to the obtained solution and mixed, and then the solvent is removed can be adopted. Among them, it is preferable to adopt the above method and the above method from the viewpoint of simplicity of operation. In addition, when adding the above additives, it is preferable to dry the additives in advance by a method such as heating under reduced pressure in order to minimize a decrease in the molecular weight of the block copolymer during addition and mixing. .

In addition to the above additives, the block copolymer composition of the present invention may further comprise a processing aid, a heat stabilizer, an antioxidant, a release agent, a weathering agent, depending on the purpose and application. , Antistatic agents, coloring agents, reinforcing agents, surfactants, inorganic fillers,
Auxiliary components such as lubricants and foaming agents can also be added.

The molded member of the present invention is a molded member obtained by melt-molding a block copolymer composition. Specific forms of the molded member include, for example, films, sheets, fibers, nonwoven fabrics, etc., as well as various shapes of injection molded products, extruded molded products, foam molded products, and blow molded products, and pellets before secondary processing. , Strands and the like.

As a method for producing the molded member of the present invention, a melt molding method generally used for molding a thermoplastic resin is used without any limitation. That is, extrusion molding, injection molding, blow molding, calender molding, etc. can be adopted. Further, with respect to film molding, uniaxial and biaxial stretching methods by a roll stretching method, a tenter method, and an inflation method can also be adopted. It is. Regarding the molding of the nonwoven fabric, a molding method such as a chemical bond type, a needle punch type, a spun bond type, and a melt blow type is used without any limitation.

When the block copolymer composition of the present invention is melt-molded, appropriate molding conditions may be selected depending on the molding method and the type of molded article. The molding temperature is
Usually, it is performed in a temperature range of 150 to 250 ° C., but it is preferable that the temperature range is 160 to 220 ° C. in order to prevent excessive heating and elongation of the residence time and to perform efficient molding.

Since the molded member of the present invention has better hydrolysis resistance than a molded member using a conventional polylactic acid-based polymer, it can be used for general purposes. Specifically, in the case of fibers and non-woven fabrics, sanitary goods such as flat sheets and bants-type disposable diapers top sheets and back sheets, fishing lines, fish nets, non-woven cloths for planting roots, non-woven cloths for nursery beds, mulching materials, weeding sheets, etc. Non-woven fabrics for agricultural and horticultural use, and films and sheets for sanitary products such as flat-type and bunt-type disposable diapers, sanitary napkins, panty liners, and urine-absorbing pads, packaging films, agricultural and horticultural multi-films, shopping bags, garbage bags, For molded products such as tapes and fertilizer bags, bottles for beverages and cosmetics,
Disposable cups, trays, knives, forks,
The block copolymer of the present invention can also be used for agricultural materials such as Western dishes such as spoons, flowerpots, nurseries, and the like.

[0082]

According to the block copolymer of the present invention, a decrease in molecular weight due to a hydrolysis reaction, which is a problem of the conventional polylactic acid-based polymer, is suppressed, and as a result, the block copolymer is formed from the block copolymer. The effect of improving the stability and durability of the molded member or the molded body is obtained. For this reason, the molded member made of the block copolymer of the present invention is applicable to various general-purpose applications where chemical recyclability or biorecyclability is required and some durability is required. Can be. As described above, the present invention expands practical uses of the lactic acid-based resin, and its significance is great.

[0083]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 [Synthesis of copolymer] L-L was placed in a sample bottle having a capacity of 10 ml.
2.00 g (13.89 mmol) of lactide and polybutadiene having hydroxyl groups at both terminals (number average molecular weight 2410,
Trans-1,4 structure 60%, cis-1,4 structure 20
%, Vinyl-1,2 structure 20%) 0.10 g (0.04
15 mmol) (5 parts by weight based on 100 parts by weight of L-lactide) were charged under a nitrogen gas atmosphere. Next, after sealing with a butyl rubber stopper, 5 μl of a toluene solution of tin (II) 2-ethylhexanoate (concentration 1 mol / l) was added to each.
Was added. The sample bottle was subsequently heated and polymerized in a 120 ° C. oil bath with magnetic stirring. The polymerization was carried out for 15 hours. After the polymerization, the sample bottle was broken to take out the polymer inside, and subjected to a dissolution / precipitation purification treatment with a chloroform / methanol system and then with a chloroform / hexane system. The amount of the polymer dried after purification was 0.863 g, as measured by weight, and the total recovery was 41%.

[Measurement of molecular weight] GPC apparatus (manufactured by Tosoh Corporation)
HLC-8120) and using TSK-
2 GEL Super HM-H, chloroform as a developing solvent, flow rate 0.6 ml / min, column temperature 40 ° C.
The molecular weight was determined in terms of polystyrene using standard polystyrene. As a result, the obtained polymer had a weight average molecular weight of 65,000 and a number average molecular weight of 42,000. In order to judge blockability and blendability, GPC
The profile is shown in FIG. FIG. 1 also shows the GPC profile of polybutadiene having a hydroxyl group at both ends used as a raw material.

The GPC profile shown in FIG. 1 shows that almost no unreacted polybutadiene having hydroxyl groups at both ends remains in the obtained polymer.

[Composition analysis] 1 H-NMR at 500 MHz
Using a device (JEOL model JNM-LA500)
The spectrum was measured using deuterated chloroform as a solvent. The composition was evaluated from the integrated values of characteristic peaks of polybutadiene and poly (L-lactide). As a result, 5.45% by weight (5.77 parts by weight, based on 100 parts by weight of the polylactic acid segment, the same applies hereinafter) in the obtained polymer is a segment derived from polybutadiene having hydroxyl groups at both ends, and The rate of introduction into the polymer is 47
%, While the polymerization rate of L-lactide was confirmed to be 40.8%. That is, the introduction ratio of the polybutadiene having hydroxyl groups at both ends is a value higher than the ratio of the charged composition, and the introduction ratio is a value higher than the polymerization ratio of L-lactide.
Further, in the 1H-NMR spectrum, no change such as shift of each characteristic peak was observed, and it was confirmed that the obtained polymer was a block copolymer comprising a polylactic acid segment and a polyhydrocarbon segment.

[Melting point] DSC apparatus (Seiko Ins)
The measurement was performed at a heating rate of 10 ° C./min. The peak of the obtained endothermic peak was evaluated as the melting point. As a result, the melting point was 17
The temperature was 3.3 ° C., and the presence of a crystal phase based on the polylactic acid segment was confirmed.

[Evaluation of Hydrolysis Property]
5 g was dissolved in 19.5 ml of chloroform. The solution was poured into a flat petri dish of about 80 mmφ. The flat petri dish was allowed to stand on a horizontal surface, and chloroform was vaporized at room temperature in an atmosphere in which a small amount of nitrogen gas flowed to form a cast film. Further, in order to completely remove the solvent, drying was performed under reduced pressure with a vacuum pump at room temperature for 5 hours. The dried film was a translucent film having a thickness of about 50μ. 1cm each of this film
It was cut into evaluation samples of x3 cm. The evaluation sample was subjected to an accelerated hydrolysis test in a constant temperature and humidity chamber at 50 ° C. and 80% humidity. After the test for a predetermined time, the sample was taken out of the chamber, and dried under reduced pressure with a vacuum pump at room temperature for 5 hours. The molecular weight of the dried sample was measured using the above-described GPC apparatus. The accelerated hydrolysis test was performed for up to 38 days. The weight average molecular weight decreased linearly with time. Therefore, the evaluation of the hydrolyzability is based on the above equation, and the hydrolysis rate constant “k”
d ”(unit: / day). The result was kd =
0.0086 (/ day).

Comparative Example 1 A homopolymer of L-lactide was synthesized in the same manner as in Example 1 except that polybutadiene having a hydroxyl group at both ends was not added, and its hydrolyzability was evaluated. The result was kd = 0.0107 (/ day).

As a result of the accelerated hydrolysis test, the block copolymer of Example 1 of the present invention showed a lower kd value than the kd value of the homopolymer of L-lactide, indicating that the hydrolyzability was low. This shows a significant improvement.

Example 2 [Synthesis of copolymer] In a sample bottle having a capacity of 10 ml, L-
1.50 g (10.42 mmol) of lactide, 2.5 g (21.93 mmol) of ε-caprolactone, and 0.10 g (0.04 g) of the polybutadiene used in Example 1.
415 mmol) (2.5 parts by weight with respect to 100 parts by weight of L-lactide) were charged under a nitrogen gas atmosphere. Next, the solution was sealed with a butyl rubber stopper, and then each was dissolved in a toluene solution of tin (II) 2-ethylhexanoate (concentration: 1 mol / mol)
l) 10 μl was added. The sample bottle is subsequently
Polymerization was carried out by heating in an oil bath at 0 ° C. with magnetic stirring. The polymerization was carried out for 18 hours. After the polymerization, the sample bottle was broken to take out the polymer inside, and subjected to a dissolution / precipitation purification treatment with a chloroform / methanol system and then with a chloroform / hexane system. The amount of the polymer dried after the purification was measured to be 2.607 g, and the total recovery was 64%.

[Measurement of Molecular Weight] The molecular weight was determined in the same manner as in Example 1. As a result, the obtained polymer had a weight average molecular weight of 134,000 and a number average molecular weight of 74,000.
In order to determine the blockability and blending property, GP
The C profile is shown in FIG. FIG. 2 also shows the GPC profile of polybutadiene having a hydroxyl group at both ends used as a raw material.

The GPC profile in FIG. 2 shows that almost no unreacted polybutadiene having hydroxyl groups at both ends remains in the obtained polymer.

[Composition analysis] In the same manner as in Example 1, 1H-
The NMR spectrum was measured to evaluate the composition. As a result, 2.64% by weight (2.71 parts by weight) of the resulting polymer was a segment derived from polybutadiene having hydroxyl groups at both ends, and the introduction ratio of the polybutadiene into the polymer was 69%, while , The polymerization rate of L-lactide is 70.1%,
It was confirmed that the polymerization rate of ε-caprolactone was 59.6%. That is, the introduction ratio of the polybutadiene having hydroxyl groups at both ends is higher than the ratio of the charged composition, and the introduction ratio is equal to the polymerization ratio of L-lactide and higher than the polymerization ratio of ε-caprolactone. Further, in the 1H-NMR spectrum, no change such as shift of the characteristic peak of the polybutadiene segment was observed, and it was confirmed that the obtained polymer was a block copolymer.

[Melting Point] In the same manner as in Example 1, the melting point was measured using a DSC apparatus. The peak of the obtained endothermic peak was evaluated as the melting point. As a result, the melting point was 44.
At 6 ° C., the presence of an aggregated phase based on a random copolymerized segment of L-lactide and ε-caprolactone was confirmed.

[Evaluation of Hydrolysis Property] An accelerated hydrolysis test was conducted in the same manner as in Example 1. As a result, the hydrolysis rate constant was kd = 0.0081 (/ day).

Comparative Example 2 L-lactide and ε were used in exactly the same manner as in Example 2 except that polybutadiene having hydroxyl groups at both ends was not added.
-A copolymer with caprolactone was synthesized, and its hydrolyzability was evaluated. The result is kd = 0.0100 (/ da
y).

The results of the accelerated hydrolysis test show that the kd value of the copolymer of L-lactide and ε-caprolactone is
The block copolymer of the present invention of Example 2 shows a lower kd value, indicating that the hydrolyzability was significantly improved.

Examples 3 to 5 Instead of polybutadiene having hydroxyl groups at both ends,
A copolymer was synthesized in the same manner as in Example 1 except that the polyhydrocarbons having hydroxyl groups at both ends shown in Table 1 were used in the amounts shown in Table 1, and the weight of the copolymer was measured,
Molecular weight measurement by NMR, composition analysis by NMR, melting point measurement by DSC, and accelerated hydrolysis test. The obtained results are also shown in Table 1.

[0101]

[Table 1]

Comparative Example 3 A polymer was synthesized in exactly the same manner as in Examples 3 to 5 except that no polyhydrocarbons were added, and the weight of the polymer was measured, the molecular weight was measured by GPC, the composition was analyzed by NMR, and the DSC was measured. And the accelerated hydrolysis test. The obtained results are also shown in Table 1.

The results in Table 1 clearly show that the block copolymer of the present invention has a lower kd value, indicating that the hydrolyzability has been significantly improved.

Examples 6 to 8 In the same manner as in Example 2 except that lactide and the like shown in Table 2 were used in place of L-lactide and ε-caprolactone in Example 2 in amounts shown in Table 2. To synthesize a copolymer, determine the weight of the copolymer, measure the molecular weight by GPC,
A composition analysis by NMR and an accelerated hydrolysis test were performed. The obtained results are also shown in Table 2.

[0105]

[Table 2]

Comparative Examples 4 to 6 Polymers were synthesized in exactly the same manner as in Examples 6 to 8 except that no polyhydrocarbons were added, and the polymer was measured for weight, measured for molecular weight by GPC, and analyzed for composition by NMR. , And accelerated hydrolysis tests. The obtained results are also shown in Table 2.

The results in Table 2 clearly show that the block copolymer of the present invention has a lower kd value, indicating that the hydrolyzability has been significantly improved.

Examples 9 to 12 [Synthesis of Polyhydrocarbon] In a 2000 ml three-necked flask, 500 ml of dry toluene, polybutadiene having hydroxyl groups at both ends (number average molecular weight 2410, trans-
60% 1,4 structure, 20% cis-1,4 structure, vinyl-
50 g (20.7 mmol) of 1,2 structure 20%) and 5 g (50 mmol) of triethylamine were charged, and stirred under an ice bath under a nitrogen atmosphere while stirring 1.83 g (10 mmol) of adipic acid dichloride in a toluene solution of 50 m.
1 was added dropwise. 20 hours on ice bath followed by 24 hours at room temperature
Stirred for hours. The reaction solution was filtered, and the filtrate was concentrated to remove the solvent, unreacted triethylamine and adipic dichloride. The viscous liquid after concentration was further extracted with a mixed solution of toluene / hexane, and impurities such as salts were separated and purified. According to GPC measurement, the obtained reaction product had a number average molecular weight in terms of polystyrene of 7300, which was about twice that of polybutadiene having a hydroxyl group at both ends of the raw material (number average molecular weight in terms of polystyrene; 3430). Also, from NMR and infrared absorption spectrum analysis,
It was confirmed that the polybutadiene had an ester bond of a hydroxyl group and an adipoyl group as a bonding group in the molecule. The recovered amount was 43 g.

[Synthesis of Copolymer] In a 500 ml polyethylene bottle, 10 g of synthesized polybutadiene having a hydroxyl group (number average molecular weight in terms of polystyrene; 7300).
And 300 g of lactide were charged under a nitrogen gas atmosphere.
Next, 0.5 ml of a toluene solution of tin (II) 2-ethylhexanoate (concentration: 1 mol / l) was added. After sealing, the mixture was heated in a 120 ° C. oil bath with magnetic stirring to carry out polymerization. The polymerization was performed for 30 hours. After the polymerization, the polyethylene bottle was broken to take out the polymer inside, and a pellet of 2 mm square was formed using a cutter. A portion of the pellet was purified by dissolution precipitation in a chloroform / methanol system.
The recovery of the polymer after purification was about 85%. The molecular weight of the purified polymer measured using a GPC apparatus was a number average molecular weight of 142,000 and a weight average molecular weight of 299000 in terms of polystyrene. From the GPC profile,
No peak or shoulder due to the polybutadiene having a hydroxyl group used was observed. As a result of performing composition analysis using a 1H-NMR apparatus, the composition ratio of polybutadiene to 100 parts by weight of the polylactic acid segment was:
3.7 parts by weight. Melting point by DSC measurement was 17
2.9 ° C. From the above results, it was confirmed that the polymer synthesized here was a block copolymer composed of a polylactic acid segment and a polyhydrocarbon segment.

[Preparation of Film] The additives shown in Table 6 were added to 10 g of the synthesized block copolymer, melt-kneaded using a mixing extruder, and extruded from a T-die to form a para-dioxanone-based copolymer. Sheet-like film (width 50 mm, length 50 mm, thickness 0.5 m
m).

[Evaluation of Hydrolysis Property] Each of the sheet-like films was cut into evaluation samples of 1 cm × 3 cm. The evaluation sample was subjected to an accelerated hydrolysis test in the same manner as in the evaluation of the hydrolyzability of Example 1. The results are shown in Table 3.

[0112]

[Table 3]

Comparative Example 7 An L-lactide homopolymer (L-lactide homopolymer) was prepared in the same manner as in [Synthesis of copolymer] in Examples 9 to 12, except that the polybutadiene having a hydroxyl group synthesized in Examples 9 to 12 was not added. Number average molecular weight: 173000, weight average molecular weight: 34
5000) was synthesized. Using this polylactic acid, except that no additives were added, [Preparation of film] of Examples 9 to 12
A sheet film was prepared in the same manner as described above. Furthermore, the evaluation of the hydrolyzability of this film was performed in the same manner as the evaluation of the hydrolyzability of Examples 9 to 12. The results are shown in Table 3.

The results in Table 3 show that the introduction of polyhydrocarbon segments and the addition of various additives significantly improved the hydrolyzability.

[Brief description of the drawings]

FIG. 1 is a GPC profile of a block copolymer of the present invention synthesized in Example 1 and polybutadiene having a hydroxyl group at both ends used as a raw material.

FIG. 2 is a GPC profile of a block copolymer of the present invention synthesized in Example 2 and a polybutadiene having a hydroxyl group at both ends used as a raw material.

Continued on the front page F-term (reference) 4J029 AA02 AB01 AB04 AC03 AD01 AE01 AE02 AE03 BA01 EA03 EA05 EG02 EG03 EG04 EG05 EG06 EG07 EG08 EG09 EH03 GA02 HA01 JA123 JE013 JE022

Claims (4)

[Claims] 1. The following repeating unit: Is a block copolymer comprising a segment comprising a polymer having at least 10 mol% and a segment derived from a polyhydrocarbon, wherein 100 parts by weight of the segment having the above repeating unit has a segment 0 derived from a polyhydrocarbon. A block copolymer characterized by being composed of 1 to 50 parts by weight. 2. A polymer of a polyhydrocarbon having at least one hydroxyl group and a lactic acid-based compound selected from lactide, lactic acid and a lower alkyl lactic acid ester, or a mixture of these lactic acid-based compounds and the lactic acid-based compound 2. The block copolymer according to claim 1, wherein the block copolymer is formed by bonding with a copolymer of a compound and a copolymerizable compound via oxygen of a hydroxyl group of polyhydrocarbons. 3. A lactic acid-based compound selected from lactide, lactic acid and a lower alkyl lactic acid ester in the presence of a polyhydrocarbon having at least one hydroxyl group and a polymerization catalyst; A method for producing a block copolymer, comprising polymerizing a lactic acid-based compound and a copolymerizable compound. 4. The block copolymer according to claim 1 or 2, and at least one addition selected from the group consisting of alkaline earth carbonates, ultraviolet absorbers, neutral sugars, and inorganic compounds having dehydration ability. A block copolymer composition comprising an agent.