JP7825854B2 - Resin composition, method for producing resin composition molded article, and method for decomposing resin composition - Google Patents

Description

The present invention relates to a resin composition, a method for producing a resin composition molded article, and a method for decomposing a resin composition.

Japan's annual production of plastics and resins exceeds 12 million tons. However, the rate at which these materials are reused is approximately 20% (material recycling rate) and 4% (chemical recycling rate). Plastics and resins are primarily manufactured using melt molding methods such as extrusion and injection molding, which require energy for heating, melting, and cooling. In other words, the molding and processing of plastics and resins requires a large amount of energy. However, most plastics and resins are derived from fossil fuels, which contributes to the depletion of global resources. Furthermore, the carbon dioxide generated by the thermal recycling of plastics and resins is one of the serious causes of global warming.

Under these circumstances, polymeric multiphase systems that undergo a transition from a solid state to a molten state under pressure have attracted attention. Such plastics, called baroplastics, are being investigated for various applications.
Patent Document 1 discloses that a baroplastic that undergoes a photoreaction upon irradiation with light is applied to a toner or developer for developing electrostatic images.
Furthermore, Patent Document 2 discloses the use of biodegradable baroplastics as agricultural materials.

JP 2011-46914 A Japanese Patent Application Laid-Open No. 2020-59674

The baroplastic used in Patent Document 1 has a first resin having an ethylenically unsaturated group that is a photoreactive group and a first glass transition temperature (Tg), and a second resin having a second Tg that is 20°C or more lower than the first Tg. Specific examples of the baroplastic disclosed in Patent Document 1 include a copolymer of an amorphous polystyrene block (first resin) and an acrylic ester resin block (second resin), and a block copolymer of an amorphous polyester resin (first resin) and a crystalline polyester resin (second resin). Patent Document 1 does not mention biodegradable baroplastics.
Patent Document 2 discloses agricultural materials that utilize baroplastic, a block copolymer of poly(trimethylene carbonate)/poly(D-lactic acid).

The inventors' objective is to provide a resin composition containing biodegradable baroplastic that can be decomposed more effectively and has a smaller environmental impact, as well as a method for producing the same and a method for decomposing the same.

The present invention relates to a resin composition comprising a matrix resin containing a biodegradable baroplastic and an enzyme, wherein the enzyme is preferably selected from the group consisting of proteases, lipases, and mixtures or combinations thereof, and the enzyme is preferably contained in an amount of 5-30% by mass of the resin composition.
It is also preferred that the biodegradable baroplastic is a copolymer comprising a polymer segment containing units derived from substituted or unsubstituted caprolactone and/or a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing units derived from lactic acid.
Furthermore, the content ratio of the polymer segment containing a unit derived from substituted or unsubstituted caprolactone and/or the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate to the polymer segment containing a unit derived from lactic acid is preferably 70:30 to 30:70 by weight.
The polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate are preferably amorphous at room temperature and have a glass transition temperature of −30° C. or lower.

The present invention further relates to a method for producing a molded resin composition, which comprises molding a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme under a pressure of 10 to 50 MPa. In the method for producing a molded resin composition, the enzyme is preferably selected from the group consisting of proteases, lipases, and mixtures or combinations thereof, and the enzyme is preferably contained in an amount of 5 to 30% based on the mass of the resin composition.
It is also preferred that the biodegradable baroplastic is a copolymer comprising a polymer segment containing units derived from substituted or unsubstituted caprolactone and/or a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing units derived from lactic acid.
Furthermore, the content ratio of the polymer segment containing a unit derived from substituted or unsubstituted caprolactone and/or the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate to the polymer segment containing a unit derived from lactic acid is preferably 70:30 to 30:70 by weight.
The polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate are preferably amorphous at room temperature and have a glass transition temperature of −30° C. or lower.

The present invention relates to a method for decomposing a resin composition, which comprises the steps of contacting a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme with water and applying a pressure in the range of 10 to 50 MPa. In the method for decomposing a resin composition, the enzyme is preferably selected from the group consisting of proteases, lipases, and mixtures or combinations thereof, and the enzyme is preferably contained in an amount of 5 to 30% based on the mass of the resin composition.
It is also preferred that the biodegradable baroplastic is a copolymer comprising a polymer segment containing units derived from substituted or unsubstituted caprolactone and/or a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing units derived from lactic acid.
Furthermore, the content ratio of the polymer segment containing a unit derived from substituted or unsubstituted caprolactone and/or the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate to the polymer segment containing a unit derived from lactic acid is preferably 70:30 to 30:70 by weight.
The polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate are preferably amorphous at room temperature and have a glass transition temperature of −30° C. or lower.

The present invention can provide a resin composition containing a biodegradable baroplastic that places a small burden on the environment. The resin composition of the present invention can be molded using a method that places a smaller burden on the environment than conventional methods, and can also be decomposed using a method that places a smaller burden on the environment.

FIG. 1 shows chromatograms by GPC of the resin compositions of the examples and comparative examples.

Embodiments of the present invention will be described in more detail below, but the present invention is not limited to the following embodiments.

One embodiment of the present invention is a resin composition comprising a matrix resin containing a biodegradable baroplastic and an enzyme. In this specification, the term "resin composition" refers to a mixture containing a polymer compound and other components, and is used synonymously with terms such as "resin mixture," "polymer composition," and "polymer mixture."

In this specification, baroplastic refers to a multiphase polymer system that can transition between a solution and phase-separated state upon application of pressure, particularly one that transitions from a solid (phase-separated) state to a molten (solution) state under pressure. For example, a block copolymer consisting of poly(n-butyl acrylate) (PBA) and polystyrene (PS) (weight ratio 50:50) is solid at room temperature and pressure. In this solid, the PBA and PS phase-separate to form a lamellar structure. When pressure is applied to this two-phase polymer system at room temperature, the PBA and PS undergo a phase transition, becoming solution-like and fluid. When the pressure is returned to normal pressure, the system immediately returns to the phase-separated state, losing fluidity and becoming a solid. By utilizing this copolymer phenomenon, it is possible to mold the copolymer at room temperature.

In this specification, biodegradability refers to the property of a substance being broken down by the action of living organisms, including microorganisms. Biodegradable plastics are narrowly defined as "plastics that are decomposed in nature by microorganisms into low-molecular-weight compounds that do not adversely affect the environment." Therefore, biodegradable baroplastics generally refer to thermoplastic resins that have both the property of transitioning from a solid (phase-separated) state to a molten (miscible) state under pressure and the property of being decomposed by microorganisms.

In one embodiment, the biodegradable baroplastic is preferably a copolymer comprising a polymer segment comprising units derived from substituted or unsubstituted caprolactone and/or a polymer segment comprising units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment comprising units derived from lactic acid.
Here, the polymer segment containing a unit derived from substituted or unsubstituted caprolactone is represented by the following formula (1-1):


Or, the following formula (1-2):


(In formula 1-1 and formula 1-2, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are the same or different and are selected from the group consisting of H, halogen, an alkyl group having 1 to 4 carbon atoms, and a cycloalkyl group having 1 to 4 carbon atoms; X is C, CH, or O; and n is a positive number.)
On the other hand, the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate is represented by the following formula (2):

(wherein Y ₁ , Y ₂ , and Y ₃ are the same or different and are selected from the group consisting of H, halogen, an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 1 to 4 carbon atoms, and 1,3-dioxolane, and m is a positive number).
Furthermore, the polymer segment containing a unit derived from lactic acid may be represented by the following formula (3):

(wherein k is a positive number).

Compounds that provide polymer segments containing units derived from substituted or unsubstituted caprolactone include ε-caprolactone, 2-methyl-ε-caprolactone, 2-ethyl-ε-caprolactone, 2-butyl-ε-caprolactone, 3-methyl-ε-caprolactone, 3-ethyl-ε-caprolactone, 3-butyl-ε-caprolactone, 4-methyl-ε-caprolactone, 4-ethyl-ε-caprolactone, 4-butyl-ε-caprolactone, 2-chloro-ε-caprolactone, 2-bromo-ε-caprolactone, 3-chloro-ε-caprolactone, 3-bromo-ε-caprolactone, 4-chloro-ε-caprolactone, 4-bromo-ε-caprolactone, 1,5-dioxepan-2-one, and 1,4,8-trioxa[4,6]spiro-undecanone, and the like. Two or more of these compounds may be used. Polymer segments containing units derived from substituted or unsubstituted caprolactone can be obtained by ring-opening polymerization of compounds that provide them.

Compounds that yield polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate include trimethylene carbonates such as trimethylene carbonate (also known as "1,3-propylene carbonate"), 4-methyl-1,3-propylene carbonate, 4-ethyl-1,3-propylene carbonate, 5-methyl-1,3-propylene carbonate, 5-ethyl-1,3-propylene carbonate, 6-methyl-1,3-propylene carbonate, and 6-ethyl-1,3-propylene carbonate, and two or more of these compounds may be used. Polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate can be obtained by ring-opening polymerization of the compounds that yield them.

Compounds that yield polymer segments containing units derived from lactic acid include L-lactic acid, D-lactic acid, and D,L-lactic acid. Polymer segments containing units derived from lactic acid can be obtained by either the lactide method, in which L-lactic acid, D-lactic acid, or D,L-lactic acid is reacted to form lactide, and the resulting lactide is polymerized in the presence of a metal catalyst, or by the direct polymerization method, in which L-lactic acid, D-lactic acid, or D,L-lactic acid is heated in an organic solvent under reduced pressure to polymerize.

In one embodiment, the biodegradable baroplastic comprises, as an essential polymer segment, a polymer segment containing units derived from lactic acid. Furthermore, the biodegradable baroplastic comprises, as an essential polymer segment, either a polymer segment containing units derived from substituted or unsubstituted caprolactone or a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate. That is, the biodegradable baroplastic is a copolymer of a polymer segment containing units derived from substituted or unsubstituted caprolactone and a polymer segment containing units derived from lactic acid, or a copolymer of a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate and a polymer segment containing units derived from lactic acid. Furthermore, the biodegradable baroplastic may comprise both a polymer segment containing units derived from substituted or unsubstituted caprolactone and a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate. In this case, the biodegradable baroplastic is a copolymer of a polymer segment containing units derived from substituted or unsubstituted caprolactone, a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing units derived from lactic acid. These copolymers may be random copolymers, alternating copolymers, block copolymers, or graft copolymers, with block copolymers being particularly preferred. The polymer segments that make up the biodegradable baroplastic are linked by ester bonds. Ester bonds have the property of being hydrolyzed by the action of water. This gives the biodegradable baroplastic used in this embodiment its biodegradability.

In biodegradable baroplastics, the weight ratio of polymer segments containing units derived from substituted or unsubstituted caprolactone and/or polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate to polymer segments containing units derived from lactic acid is preferably 70:30-30:70. In order to maintain the physical and chemical properties of the biodegradable baroplastic resin within an appropriate range, it is preferable to keep the content ratio of polymer segments containing units derived from lactic acid within the above range.

The weight average molecular weight of the biodegradable baroplastic may be 10,000 or more, 15,000 or more, or 30,000 or more. The weight average molecular weight of the biodegradable baroplastic may be 100,000 or less, or 250,000 or less. Having the weight average molecular weight of the biodegradable baroplastic within the above ranges can further improve moldability and biodegradability. Note that the weight average molecular weight in this specification refers to a value measured by gel permeation chromatography and is expressed in terms of polystyrene.
The molecular weight of the biodegradable baroplastic may be 10 kDa or more, 15 kDa or more, or 30 kDa or more. The molecular weight of the biodegradable baroplastic may be 250 kDa or less, or 100 kDa or less. When the molecular weight of the biodegradable baroplastic is within the above range, moldability and biodegradability can be further improved.
In the biodegradable baroplastic, the weight average molecular weight of the polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate may be 3,000 to 75,000, 5,000 to 125,000, or 7,000 to 175,000. In the biodegradable baroplastic, the weight average molecular weight of the polymer segment containing units derived from lactic acid may be 3,000 to 75,000, 5,000 to 125,000, or 7,000 to 175,000.

In biodegradable baroplastics, it is particularly preferred that the polymer segments containing units derived from substituted or unsubstituted caprolactone and/or the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate are amorphous at room temperature. It is also particularly preferred that the polymer segments containing units derived from substituted or unsubstituted caprolactone and/or the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate are polymers with a glass transition temperature of -30°C or lower. Polymer segments containing units derived from lactic acid, an essential component of biodegradable baroplastics, are relatively prone to crystallization. Therefore, from the perspective of improving the moldability and biodegradability of biodegradable baroplastics, it is preferred to have, as copolymer components, polymer segments containing units derived from substituted or unsubstituted caprolactone and/or polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate that are amorphous at room temperature and have a glass transition temperature of -30°C or lower. The glass transition temperature of the polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate can be measured by differential scanning calorimetry (DSC).

In one embodiment, the resin composition contains the above-mentioned biodegradable baroplastic as a matrix resin. "Matrix resin" means that the biodegradable baroplastic is a component that forms the matrix (continuous phase) in the resin composition.

In one embodiment, the resin composition contains an enzyme. In one embodiment, the enzyme is primarily a proteinaceous catalyst produced in vivo. In one embodiment, the resin composition preferably contains an enzyme selected from the group consisting of proteases, lipases, and mixtures or combinations thereof. Proteases are enzymes that catalyze reactions that hydrolyze peptide bonds that form proteins and peptides. On the other hand, lipases are enzymes that catalyze reactions that hydrolyze ester bonds that constitute fats. In other words, in one embodiment, the resin composition preferably contains a hydrolase. The protease can be selected from the group consisting of serine proteases, cysteine proteases, threonine proteases, aspartic acid proteases, asparagine proteases, glutamic acid proteases, metalloproteases, and mixtures thereof.

A resin composition according to one embodiment, which includes a matrix resin containing a biodegradable baroplastic and an enzyme, is highly biodegradable, particularly in water, and can reduce the burden on the environment. The polymer segments containing units derived from substituted or unsubstituted caprolactone, the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate, and the polymer segments containing units derived from lactic acid, which are components of the biodegradable baroplastic, are all polymer segments that undergo hydrolysis to lower molecular weights due to the action of water in the environment. The action of the enzyme contained in the resin composition according to one embodiment accelerates the biodegradation of the matrix resin, particularly in water.
From the viewpoint of reducing the environmental impact of the resin composition of one embodiment, the enzyme is preferably contained in an amount of 5-30% by mass of the resin composition of one embodiment. If the enzyme content is too low, the function of supporting the biodegradation of the resin composition will be insufficient, and if the enzyme content is too high, it will be difficult to maintain the shape of the resin composition. Considering the function of the enzyme and the stability of the resin composition, the enzyme content is preferably approximately 10-20% by mass of the resin composition. The resin composition of one embodiment can be obtained by mixing a matrix resin containing a biodegradable baroplastic with an enzyme, and it is particularly preferable to obtain it by mixing the enzyme with a molten matrix resin. The resin composition of one embodiment obtained by mixing a matrix resin with an enzyme may be in any form, such as powder, granules, or pellets.

In one embodiment, the resin composition may further contain other resins in addition to the matrix resin and the enzyme. Examples of the other resins include biodegradable resins such as polylactic acid, polycaprolactone, and polyhydroxyalkanoate. When the matrix resin further contains other resins, the content of the other resins may be 10% by mass or less, or 5% by mass or less, based on the total mass of the matrix resin.
In addition to the matrix resin and the enzyme, the resin composition of one embodiment may contain other additives for resin compositions, such as antioxidants, ultraviolet absorbers, stabilizers, plasticizers, lubricants, viscosity modifiers, nucleating agents, reinforcing agents, and antibacterial agents.

A second embodiment of the present invention is a method for producing a resin composition molded article, which includes a step of molding a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme under a pressure of 10-50 MPa.

In a second embodiment, the biodegradable baroplastic is preferably a copolymer comprising a polymer segment comprising units derived from substituted or unsubstituted caprolactone and/or a polymer segment comprising units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment comprising units derived from lactic acid.
Here, the polymer segment containing a unit derived from substituted or unsubstituted caprolactone is represented by the following formula (1-1):


Or, the following formula (1-2):


(In formula 1-1 and formula 1-2, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are the same or different and are selected from the group consisting of H, halogen, an alkyl group having 1 to 4 carbon atoms, and a cycloalkyl group having 1 to 4 carbon atoms; X is C, CH, or O; and n is a positive number.)
On the other hand, the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate is represented by the following formula (2):

(wherein Y ₁ , Y ₂ , and Y ₃ are the same or different and are selected from the group consisting of H, halogen, an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 1 to 4 carbon atoms, and 1,3-dioxolane, and m is a positive number).
Furthermore, the polymer segment containing a unit derived from lactic acid may be represented by the following formula (3):

(wherein k is a positive number).

Compounds that provide polymer segments containing units derived from substituted or unsubstituted caprolactone include ε-caprolactone, 2-methyl-ε-caprolactone, 2-ethyl-ε-caprolactone, 2-butyl-ε-caprolactone, 3-methyl-ε-caprolactone, 3-ethyl-ε-caprolactone, 3-butyl-ε-caprolactone, 4-methyl-ε-caprolactone, 4-ethyl-ε-caprolactone, 4-butyl-ε-caprolactone, 2-chloro-ε-caprolactone, 2-bromo-ε-caprolactone, 3-chloro-ε-caprolactone, 3-bromo-ε-caprolactone, 4-chloro-ε-caprolactone, 4-bromo-ε-caprolactone, 1,5-dioxepan-2-one, and 1,4,8-trioxa[4,6]spiro-undecanone, and the like. Two or more of these compounds may be used. Polymer segments containing units derived from substituted or unsubstituted caprolactone can be obtained by ring-opening polymerization of compounds that provide them.

Compounds that yield polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate include trimethylene carbonate (also known as "1,3-propylene carbonate"), 4-methyl-1,3-propylene carbonate, 4-ethyl-1,3-propylene carbonate, 5-methyl-1,3-propylene carbonate, 5-ethyl-1,3-propylene carbonate, 6-methyl-1,3-propylene carbonate, and 6-ethyl-1,3-propylene carbonate, and two or more of these compounds may be used. Polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate can be obtained by ring-opening polymerization of the compounds that yield them.

Compounds that yield polymer segments containing units derived from lactic acid include L-lactic acid, D-lactic acid, and D,L-lactic acid. Polymer segments containing units derived from lactic acid can be obtained by either the lactide method, in which L-lactic acid, D-lactic acid, or D,L-lactic acid is reacted to form lactide, and the resulting lactide is polymerized in the presence of a metal catalyst, or by the direct polymerization method, in which L-lactic acid, D-lactic acid, or D,L-lactic acid is heated in an organic solvent under reduced pressure to polymerize.

In a second embodiment, the biodegradable baroplastic comprises, as an essential polymer segment, a polymer segment containing units derived from lactic acid. Furthermore, the biodegradable baroplastic comprises, as an essential polymer segment, either a polymer segment containing units derived from substituted or unsubstituted caprolactone or a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate. That is, the biodegradable baroplastic is a copolymer of a polymer segment containing units derived from substituted or unsubstituted caprolactone and a polymer segment containing units derived from lactic acid, or a copolymer of a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate and a polymer segment containing units derived from lactic acid. Furthermore, the biodegradable baroplastic may comprise both a polymer segment containing units derived from substituted or unsubstituted caprolactone and a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate. In this case, the biodegradable baroplastic is a copolymer of a polymer segment containing units derived from substituted or unsubstituted caprolactone, a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing units derived from lactic acid. These copolymers may be random copolymers, alternating copolymers, block copolymers, or graft copolymers, with block copolymers being particularly preferred. The polymer segments that make up the biodegradable baroplastic are linked by ester bonds. Ester bonds have the property of being hydrolyzed by the action of water. This gives the biodegradable baroplastic used in this embodiment its biodegradability.

In biodegradable baroplastics, the weight ratio of polymer segments containing units derived from substituted or unsubstituted caprolactone and/or polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate to polymer segments containing units derived from lactic acid is preferably 70:30-30:70. In order to maintain the physical and chemical properties of the biodegradable baroplastic resin within an appropriate range, it is preferable to keep the content ratio of polymer segments containing units derived from lactic acid within the above range.

The weight average molecular weight of the biodegradable baroplastic may be 10,000 or more, 15,000 or more, or 30,000 or more. The weight average molecular weight of the biodegradable baroplastic may be 100,000 or less, or 250,000 or less. When the weight average molecular weight of the biodegradable baroplastic is within the above range, moldability and biodegradability can be further improved.
The molecular weight of the biodegradable baroplastic may be 10 kDa or more, 15 kDa or more, or 30 kDa or more. The molecular weight of the biodegradable baroplastic may be 250 kDa or less, or 100 kDa or less. When the molecular weight of the biodegradable baroplastic is within the above range, moldability and biodegradability can be further improved.
In the biodegradable baroplastic, the weight average molecular weight of the polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate may be 3,000 to 75,000, 5,000 to 125,000, or 7,000 to 175,000. In the biodegradable baroplastic, the weight average molecular weight of the polymer segment containing units derived from lactic acid may be 3,000 to 75,000, 5,000 to 125,000, or 7,000 to 175,000.

In biodegradable baroplastics, it is particularly preferred that the polymer segments containing units derived from substituted or unsubstituted caprolactone and/or the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate are amorphous at room temperature. It is also particularly preferred that the polymer segments containing units derived from substituted or unsubstituted caprolactone and/or the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate are polymers with a glass transition temperature of -30°C or lower. Polymer segments containing units derived from lactic acid, an essential component of biodegradable baroplastics, are relatively prone to crystallization. Therefore, from the perspective of improving the moldability and biodegradability of biodegradable baroplastics, it is preferred to have, as copolymer components, polymer segments containing units derived from substituted or unsubstituted caprolactone and/or polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate that are amorphous at room temperature and have a glass transition temperature of -30°C or lower. The glass transition temperature of the polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate can be measured by differential scanning calorimetry (DSC).

The resin composition used in the second embodiment contains the above-mentioned biodegradable baroplastic as a matrix resin. "Matrix resin" means that the biodegradable baroplastic is a component that forms the matrix (continuous phase) in the resin composition.

The resin composition used in the second embodiment contains an enzyme. Enzymes are primarily proteinaceous catalysts produced in living organisms. In the second embodiment, the resin composition preferably contains an enzyme selected from the group consisting of proteases, lipases, and mixtures or combinations thereof. Proteases are enzymes that catalyze the reaction of hydrolyzing peptide bonds that form proteins and peptides. On the other hand, lipases are enzymes that catalyze the reaction of hydrolyzing ester bonds that make up fats. In other words, the resin composition used in the second embodiment preferably contains a hydrolase. The protease can be selected from the group consisting of serine proteases, cysteine proteases, threonine proteases, aspartic acid proteases, asparagine proteases, glutamic acid proteases, metalloproteases, and mixtures thereof.

From the viewpoint of reducing the environmental impact of the resin composition used in the second embodiment, the enzyme is preferably contained in an amount of 5-30% by mass of the resin composition of the second embodiment. If the enzyme content is too low, the function of supporting the biodegradation of the resin composition will be insufficient, and if the enzyme content is too high, it will be difficult to maintain the shape of the resin composition. Considering the function of the enzyme and the stability of the resin composition, the enzyme content is preferably approximately 10-20% by mass of the resin composition. The resin composition used in the second embodiment can be obtained by mixing a matrix resin containing a biodegradable baroplastic with an enzyme, and is particularly preferably obtained by mixing the enzyme with a molten matrix resin. The resin composition used in the second embodiment, obtained by mixing a matrix resin with an enzyme, may be in any form, such as powder, granules, or pellets.

The resin composition to be molded in the second embodiment may further contain other resins in addition to the matrix resin and enzyme. Examples of other resins include biodegradable resins such as polylactic acid, polycaprolactone, and polyhydroxyalkanoate. When the matrix resin further contains other resins, the content of the other resins may be 10% by mass or less, or 5% by mass or less, based on the total mass of the matrix resin.
The resin composition to be molded in the second embodiment may contain, in addition to the matrix resin and the enzyme, other additives for resin compositions, such as antioxidants, ultraviolet absorbers, stabilizers, plasticizers, lubricants, viscosity modifiers, nucleating agents, reinforcing agents, and antibacterial agents.

Molding of the resin composition is preferably carried out under a pressure of 10-50 MPa, and more preferably under a pressure of 15-45 MPa or 20-40 MPa. When molding the resin composition, it can be heated to room temperature or up to approximately 100°C if necessary, but from the perspective of reducing the energy consumed during molding, it is preferable to carry out molding at room temperature. However, if necessary, it is also possible to mold the resin composition by heating it to below 100°C, below 80°C, below 60°C, or below 40°C. Molding of the resin composition can be carried out by applying the desired pressure to the resin composition using known machines such as an autoclave, extruder, compression molding machine, injection molding machine, or vacuum molding machine. To simultaneously apply pressure to the resin composition and mold it into the desired shape, it is preferable to use an extruder, compression molding machine, or injection molding machine for molding. The time for which the resin composition is pressed depends on factors such as the size of the desired resin composition molded product, but can be 1 minute or more, 3 minutes or more, 5 minutes or more, or 10 minutes or more; the desired resin composition molded product can be produced by pressing for up to about 60 minutes.

The resin composition molded article produced in the second embodiment is formed from a resin composition containing a matrix resin containing a biodegradable baroplastic and an enzyme. Therefore, the resin composition molded article produced in the second embodiment is highly biodegradable, particularly in water, and can reduce the environmental impact. The polymer segments containing units derived from substituted or unsubstituted caprolactone, the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate, and the polymer segments containing units derived from lactic acid, which are components of biodegradable baroplastic, are all polymer segments that undergo hydrolysis to lower molecular weights due to the action of water in the environment. The action of the enzymes contained in the resin composition molded article produced in the second embodiment accelerates the biodegradation of the matrix resin, particularly in water. The resin composition molded article produced in the second embodiment can be used as any resin molded article to be used at room temperature and atmospheric pressure. The resin composition molded article produced in the second embodiment decomposes relatively quickly in water under high pressure (e.g., in the deep sea), thereby reducing the environmental impact.

The resin composition to be molded in the second embodiment may be the resin composition of the first embodiment described above. As described above, the resin composition of the first embodiment contains a biodegradable baroplastic as a matrix resin, and therefore has the property of transitioning from a solid state to a molten state under pressure, which is a characteristic of baroplastics. Therefore, the resin composition to be molded in the second embodiment can be molded by applying pressure at a temperature range near room temperature.

A third embodiment of the present invention is a method for decomposing a resin composition, comprising the steps of contacting a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme with water and applying a pressure in the range of 10-50 MPa.

In the third embodiment, the biodegradable baroplastic is preferably a copolymer comprising a polymer segment comprising units derived from substituted or unsubstituted caprolactone and/or a polymer segment comprising units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment comprising units derived from lactic acid.
Here, the polymer segment containing a unit derived from substituted or unsubstituted caprolactone is represented by the following formula (1-1):


Or, the following formula (1-2):


(In formula 1-1 and formula 1-2, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are the same or different and are selected from the group consisting of H, halogen, an alkyl group having 1 to 4 carbon atoms, and a cycloalkyl group having 1 to 4 carbon atoms; X is C, CH, or O; and n is a positive number.)
On the other hand, the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate is represented by the following formula (2):

(wherein Y ₁ , Y ₂ , and Y ₃ are the same or different and are selected from the group consisting of H, halogen, an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 1 to 4 carbon atoms, and 1,3-dioxolane, and m is a positive number).
Furthermore, the polymer segment containing a unit derived from lactic acid may be represented by the following formula (3):

(wherein k is a positive number).

Compounds that provide polymer segments containing units derived from substituted or unsubstituted caprolactone include ε-caprolactone, 2-methyl-ε-caprolactone, 2-ethyl-ε-caprolactone, 2-butyl-ε-caprolactone, 3-methyl-ε-caprolactone, 3-ethyl-ε-caprolactone, 3-butyl-ε-caprolactone, 4-methyl-ε-caprolactone, 4-ethyl-ε-caprolactone, 4-butyl-ε-caprolactone, 2-chloro-ε-caprolactone, 2-bromo-ε-caprolactone, 3-chloro-ε-caprolactone, 3-bromo-ε-caprolactone, 4-chloro-ε-caprolactone, 4-bromo-ε-caprolactone, 1,5-dioxepan-2-one, and 1,4,8-trioxa[4,6]spiro-undecanone, and the like. Two or more of these compounds may be used. Polymer segments containing units derived from substituted or unsubstituted caprolactone can be obtained by ring-opening polymerization of compounds that provide them.

Compounds that yield polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate include trimethylene carbonate (also known as "1,3-propylene carbonate"), 4-methyl-1,3-propylene carbonate, 4-ethyl-1,3-propylene carbonate, 5-methyl-1,3-propylene carbonate, 5-ethyl-1,3-propylene carbonate, 6-methyl-1,3-propylene carbonate, and 6-ethyl-1,3-propylene carbonate, and two or more of these compounds may be used. Polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate can be obtained by ring-opening polymerization of the compounds that yield them.

Compounds that yield polymer segments containing units derived from lactic acid include L-lactic acid, D-lactic acid, and D,L-lactic acid. Polymer segments containing units derived from lactic acid can be obtained by either the lactide method, in which L-lactic acid, D-lactic acid, or D,L-lactic acid is reacted to form lactide, and the resulting lactide is polymerized in the presence of a metal catalyst, or by the direct polymerization method, in which L-lactic acid, D-lactic acid, or D,L-lactic acid is heated in an organic solvent under reduced pressure to polymerize.

In a third embodiment, the biodegradable baroplastic comprises, as an essential polymer segment, a polymer segment containing units derived from lactic acid. Furthermore, the biodegradable baroplastic comprises, as an essential polymer segment, either a polymer segment containing units derived from substituted or unsubstituted caprolactone or a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate. That is, the biodegradable baroplastic is a copolymer of a polymer segment containing units derived from substituted or unsubstituted caprolactone and a polymer segment containing units derived from lactic acid, or a copolymer of a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate and a polymer segment containing units derived from lactic acid. Furthermore, the biodegradable baroplastic may comprise both a polymer segment containing units derived from substituted or unsubstituted caprolactone and a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate. In this case, the biodegradable baroplastic is a copolymer of a polymer segment containing units derived from substituted or unsubstituted caprolactone, a polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing units derived from lactic acid. These copolymers may be random copolymers, alternating copolymers, block copolymers, or graft copolymers, with block copolymers being particularly preferred. The polymer segments constituting the biodegradable baroplastic are linked by ester bonds. Ester bonds have the property of being hydrolyzed by the action of water. This imparts biodegradability to the biodegradable baroplastic in the resin composition that decomposes in the third embodiment.

In biodegradable baroplastics, the weight ratio of polymer segments containing units derived from substituted or unsubstituted caprolactone and/or polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate to polymer segments containing units derived from lactic acid is preferably 70:30-30:70. In order to maintain the physical and chemical properties of the biodegradable baroplastic resin within an appropriate range, it is preferable to keep the content ratio of polymer segments containing units derived from lactic acid within the above range.

The weight average molecular weight of the biodegradable baroplastic may be 10,000 or more, 15,000 or more, or 30,000 or more. The weight average molecular weight of the biodegradable baroplastic may be 100,000 or less, or 250,000 or less. When the weight average molecular weight of the biodegradable baroplastic is within the above range, moldability and biodegradability can be further improved.
The molecular weight of the biodegradable baroplastic may be 10 kDa or more, 15 kDa or more, or 30 kDa or more. The molecular weight of the biodegradable baroplastic may be 250 kDa or less, or 100 kDa or less. When the molecular weight of the biodegradable baroplastic is within the above range, moldability and biodegradability can be further improved.
In the biodegradable baroplastic, the weight average molecular weight of the polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate may be 3,000 to 75,000, 5,000 to 125,000, or 7,000 to 175,000. In the biodegradable baroplastic, the weight average molecular weight of the polymer segment containing units derived from lactic acid may be 3,000 to 75,000, 5,000 to 125,000, or 7,000 to 175,000.

In biodegradable baroplastics, it is particularly preferred that the polymer segments containing units derived from substituted or unsubstituted caprolactone and/or the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate are amorphous at room temperature. It is also particularly preferred that the polymer segments containing units derived from substituted or unsubstituted caprolactone and/or the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate are polymers with a glass transition temperature of -30°C or lower. Polymer segments containing units derived from lactic acid, an essential component of biodegradable baroplastics, are relatively prone to crystallization. Therefore, from the perspective of improving the moldability and biodegradability of biodegradable baroplastics, it is preferred to have, as copolymer components, polymer segments containing units derived from substituted or unsubstituted caprolactone and/or polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate that are amorphous at room temperature and have a glass transition temperature of -30°C or lower. The glass transition temperature of the polymer segment containing units derived from substituted or unsubstituted caprolactone and/or the polymer segment containing units derived from substituted or unsubstituted trimethylene carbonate can be measured by differential scanning calorimetry (DSC).

In the third embodiment, the degradable resin composition contains the above-mentioned biodegradable baroplastic as a matrix resin. "Matrix resin" means that the biodegradable baroplastic is a component that forms the matrix (continuous phase) in the resin composition.

In the third embodiment, the resin composition to be decomposed contains an enzyme. In the third embodiment, the enzyme is primarily a proteinaceous catalyst produced in vivo. In the third embodiment, the resin composition preferably contains an enzyme selected from the group consisting of proteases, lipases, and mixtures or combinations thereof. Proteases are enzymes that catalyze reactions that hydrolyze peptide bonds that form proteins and peptides. On the other hand, lipases are enzymes that catalyze reactions that hydrolyze ester bonds that constitute fats. In other words, in the third embodiment, the resin composition to be decomposed preferably contains a hydrolase. The protease can be selected from the group consisting of serine proteases, cysteine proteases, threonine proteases, aspartic acid proteases, asparagine proteases, glutamic acid proteases, metalloproteases, and mixtures thereof.

From the viewpoint of reducing the environmental burden caused by the resin composition decomposed in the third embodiment, the enzyme is preferably contained in an amount of 5-30% by mass of the resin composition decomposed in the third embodiment. If the enzyme content is too low, the function of supporting the biodegradation of the resin composition will be insufficient, and if the enzyme content is too high, it will be difficult to maintain the shape of the resin composition. Considering the function of the enzyme and the stability of the resin composition, the enzyme content is preferably approximately 10-20% by mass of the resin composition. The resin composition decomposed in the third embodiment can be obtained by mixing a matrix resin containing a biodegradable baroplastic with an enzyme, and it is particularly preferable to obtain it by mixing the enzyme with a molten matrix resin. The resin composition decomposed in the third embodiment obtained by mixing a matrix resin with an enzyme may be in any form, such as powder, granules, or pellets.
The degradable resin composition in the third embodiment may further contain other resins in addition to the matrix resin and enzyme. Examples of the other resins include biodegradable resins such as polylactic acid, polycaprolactone, and polyhydroxyalkanoate. When the matrix resin further contains other resins, the content of the other resins may be 10% by mass or less, or 5% by mass or less, based on the total mass of the matrix resin.
The resin composition to be decomposed in the third embodiment may contain, in addition to the matrix resin and the enzyme, other additives for resin compositions, such as antioxidants, ultraviolet absorbers, stabilizers, plasticizers, lubricants, viscosity modifiers, nucleating agents, reinforcing agents, and antibacterial agents.

In the third embodiment, contacting the resin composition with water can be accomplished by various methods, such as immersing the resin composition in water, applying water to the surface of the resin composition, or spraying water onto the surface of the resin composition. It is more preferable to conduct the decomposition under a pressure of 10-50 MPa, 15-45 MPa, or 20-40 MPa while the resin composition is in contact with water. When decomposing the resin composition, it can be heated to room temperature to approximately 100°C, if necessary. However, from the perspective of reducing the energy consumed during decomposition, decomposition at room temperature is preferred. However, if necessary, it is also possible to decompose the resin composition by heating to approximately 100°C or below, 80°C or below, 60°C or below, or 40°C or below. The decomposition of the resin composition can be carried out by applying the desired pressure to the resin composition while contacting it with water using a known machine such as an autoclave. For efficient decomposition of the resin composition, decomposition using an autoclave is preferred. The pressurization time for the resin composition depends on factors such as the amount of resin composition to be decomposed, but can be 1 minute or more, 3 minutes or more, 5 minutes or more, or 10 minutes or more; most resin compositions can be decomposed by applying pressure for up to about 60 minutes.

The resin composition degradable in the third embodiment is a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme. Therefore, the resin composition degradable in the third embodiment is biodegradable in water under pressure, for example, in the deep sea. The polymer segments containing units derived from substituted or unsubstituted caprolactone, the polymer segments containing units derived from substituted or unsubstituted trimethylene carbonate, and the polymer segments containing units derived from lactic acid, which are components of biodegradable baroplastic, are all polymer segments that undergo hydrolysis to lower molecular weights due to the action of water in the environment. The action of the enzymes contained in the resin composition degradable in the third embodiment accelerates the biodegradation of the matrix resin, particularly in water. The resin composition degradable in the third embodiment can be used as any resin molded product used at room temperature and pressure, but as described above, it degrades relatively quickly in water under high pressure (for example, in the deep sea), thereby reducing the environmental impact.

In the third embodiment, the resin composition that decomposes may be the resin composition of the first embodiment described above. As described above, the resin composition of the first embodiment contains a biodegradable baroplastic as a matrix and also contains an enzyme, and therefore can be decomposed by contacting it with water.

Embodiments of the present invention are described in detail below. The present invention is not limited to the following examples, as long as they do not depart from the gist of the invention.

[Production Example: Production of Resin Composition]

In a glove box, 40 mg (0.1 mmol) of tin(II) 2-ethylhexanoate and 4.6 mg (0.1 mmol) of ethanol were weighed and placed in a container. Next, 5.0 g (49 mmol) of trimethylene carbonate and 5 mL of toluene were added to the container through the septum using a syringe. Thereafter, a ring-opening polymerization reaction was carried out at 100°C for 24 hours with stirring. It was confirmed by ¹ H-NMR that the trimethylene carbonate contained in the solution in the container had been consumed. Thereafter, 5.0 g (35 mmol) of L-lactide, which is a dimer of L-lactic acid, was added, and the ring-opening polymerization reaction was further carried out at 110°C for 24 hours.

After the reaction was completed, the reaction solution was added dropwise to methanol for reprecipitation and purification, producing a poly(trimethylene carbonate)/poly(L-lactic acid) block copolymer (weight-average molecular weight: 40 kDa, weight-average molecular weight of poly(L-lactic acid) unit: 19 kDa).

The block copolymer thus obtained was mixed with proteinase K (Merck) at a concentration of 5% by weight of the mixture, and the mixture was extruded under a pressure of 50 MPa using a capillary rheometer (device name: CFT-500EX, Shimadzu Corporation) to obtain a resin composition.

Example: Decomposition of biodegradable baroplastics under pressure
1.0 gram of the resin composition was placed in a buffer (0.1 M phosphate buffer solution, pH 7.5), and a pressure of 40 MPa was created in a pressure vessel (Shin Corporation) and pressurized at room temperature for 4 days. The pressurized resin composition was separated by molecular weight using gel permeation chromatography (GPC, instrument name: LC-20AD, Shimadzu Corporation, column: TSKgel G3000H _xL , Tosoh Corporation) (Example 1). A chromatogram of the resin composition is shown in Figure 1.
As control experiments, the above block copolymer was stored under normal pressure for 4 days (Comparative Example 1), the above block copolymer was immersed in a buffer and stored under a pressurized environment of 40 MPa for 4 days (Comparative Example 2), and the above resin composition was immersed in a buffer and stored under normal pressure for 4 days (Comparative Example 3). These were also separated by GPC according to molecular weight in the same manner as in Example 1. Chromatograms for each comparative example are also shown in FIG. 1 .

As can be seen from the chromatogram in FIG. 1, by placing the resin composition of the present invention under pressure, the molecular weight peak shifts to the lower molecular weight side and the amount of low molecular weight components increases.
When the resin composition of the present invention containing proteinase K (an enzyme) is subjected to pressure, the block copolymer undergoes a phase transition from a phase-separated state to a miscible state, becoming a fluid. This is thought to be due to the increased mobility of the poly(L-lactic acid) moiety (a polymer segment containing a unit derived from lactic acid), which increases the frequency of collisions with the enzyme, thereby accelerating the decomposition of the resin composition.
Comparative Example 1 is an experimental example in which a block copolymer was placed under normal pressure; Comparative Example 2 is an experimental example in which an enzyme-free block copolymer was contacted with water and placed under pressure; and Comparative Example 3 is an experimental example in which an enzyme-containing resin composition was contacted with water and placed under normal pressure. Simply placing the block copolymer under pressure for four days did not result in accelerated decomposition of the block copolymer. However, it is expected that the decomposition of a biodegradable baroplastic block copolymer can be accelerated by placing it under pressure for a long period of time.

Claims (14)

A resin composition comprising a matrix resin including a biodegradable baroplastic and an enzyme selected from the group consisting of a protease, a lipase, and a mixture or combination thereof , wherein the enzyme is contained in an amount of 5-30% based on the mass of the resin composition . 2. The resin composition according to claim 1, wherein the biodegradable baroplastic is a copolymer comprising a polymer segment comprising units derived from substituted or unsubstituted caprolactone and/or a polymer segment comprising units derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment comprising units derived from lactic acid. 3. The resin composition according to claim 2, wherein a content ratio of the polymer segment containing the unit derived from substituted or unsubstituted caprolactone and/or the polymer segment containing the unit derived from substituted or unsubstituted trimethylene carbonate to the polymer segment containing the unit derived from lactic acid is 70:30 to 30:70 by weight. The resin composition according to claim 2 or 3, wherein the polymer segment containing a unit derived from substituted or unsubstituted caprolactone and /or the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate is amorphous at room temperature and has a glass transition temperature of −30° C. or lower. A method for producing a resin composition molded article, comprising a step of molding a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme selected from the group consisting of a protease, a lipase, and a mixture or combination thereof, under a pressure of 10-50 MPa. The method for producing a molded article of a resin composition according to claim 5 , wherein the enzyme is contained in an amount of 5 to 30% based on the mass of the resin composition. 7. The method for producing a resin composition molded article according to claim 5 or 6, wherein the biodegradable baroplastic is a copolymer comprising a polymer segment containing a unit derived from substituted or unsubstituted caprolactone and/ or a polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing a unit derived from lactic acid. The method for producing a resin composition molded product according to claim 7, wherein a content ratio of the polymer segment containing the unit derived from substituted or unsubstituted caprolactone and/or the polymer segment containing the unit derived from substituted or unsubstituted trimethylene carbonate to the polymer segment containing the unit derived from lactic acid is 70:30 to 30:70 by weight. The method for producing a resin composition molded product according to claim 7 or 8, wherein the polymer segment containing a unit derived from substituted or unsubstituted caprolactone and /or the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate is amorphous at room temperature and has a glass transition temperature of −30° C. or lower. A method for decomposing a resin composition, comprising the steps of contacting a resin composition containing a matrix resin including a biodegradable baroplastic and an enzyme selected from the group consisting of a protease, a lipase, and a mixture or combination thereof with water and applying a pressure in the range of 10-50 MPa. The method for decomposing a resin composition according to claim 10 , wherein the enzyme is contained in an amount of 5 to 30% based on the mass of the resin composition. The method for decomposing a resin composition according to claim 9 or 10, wherein the biodegradable baroplastic is a copolymer comprising a polymer segment containing a unit derived from substituted or unsubstituted caprolactone and/ or a polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment containing a unit derived from lactic acid. The method for decomposing a resin composition according to claim 12, wherein a content ratio of the polymer segment containing the unit derived from substituted or unsubstituted caprolactone and/or the polymer segment containing the unit derived from substituted or unsubstituted trimethylene carbonate to the polymer segment containing the unit derived from lactic acid is 70:30 to 30:70 by weight. The method for decomposing a resin composition according to claim 12 or 13, wherein the polymer segment containing a unit derived from substituted or unsubstituted caprolactone and /or the polymer segment containing a unit derived from substituted or unsubstituted trimethylene carbonate is amorphous at room temperature and has a glass transition temperature of −30° C. or lower.