JP7825855B2 - Resin composition, method for producing molded article from resin composition, and method for lowering the melting point of a resin - Google Patents

Description

The present invention relates to a resin composition, a method for producing a resin composition molded article, and a method for lowering the melting point of a resin.

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 method for plasticizing a resin and lowering its melting point using biodegradable baroplastics, which are more effectively degradable and have a smaller environmental impact, as well as a resin composition with a lowered melting point, and a method for molding a resin composition with a lowered melting point to produce a resin composition molded article.

The present invention relates to a resin composition comprising a matrix resin and a biodegradable baroplastic.
Preferably, the matrix resin is selected from the group consisting of polyolefins, polyvinyl acetate, polyvinyl chloride, polystyrene, acrylic resins, polyester resins, polyurethanes, polycarbonates, phenolic resins, epoxy resins, polylactic acid (PLA resin), and mixtures or combinations thereof.
The biodegradable baroplastic is preferably contained in an amount of 10 to 50% 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 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 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 resin composition molded article, which comprises molding a resin composition containing a matrix resin and a biodegradable baroplastic under a pressure of 10-50 MPa, wherein the matrix resin is preferably selected from the group consisting of polyolefin, polyvinyl acetate, polyvinyl chloride, polystyrene, acrylic resin, polyester resin, polyurethane, polycarbonate, phenolic resin, epoxy resin, polylactic acid (PLA resin), and mixtures or combinations thereof.
The biodegradable baroplastic is preferably contained in an amount of 10 to 50% 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 lowering the melting point of a resin, which comprises the step of adding a biodegradable baroplastic to a matrix resin, preferably selected from the group consisting of polyolefins, polyvinyl acetate, polyvinyl chloride, polystyrene, acrylic resins, polyester resins, polyurethanes, polycarbonates, phenolic resins, epoxy resins, polylactic acid (PLA resin), and mixtures or combinations thereof.
The biodegradable baroplastic is preferably added in an amount of 10-50% by mass of the resin.
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 provides a resin composition in which a biodegradable baroplastic, which places a small burden on the environment, is mixed with a resin. The biodegradable baroplastic mixed with the resin can lower the melting point of the mixed resin. Furthermore, the resin composition of the present invention can be molded using a method that places a smaller burden on the environment than conventional methods. It 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 and a biodegradable baroplastic. 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 one embodiment, the resin composition contains a matrix resin. As used herein, the term "matrix resin" refers to a resin that is a component that forms the matrix (continuous phase) in the resin composition. In one embodiment, the matrix resin is preferably selected from the group consisting of polyolefins, polyvinyl acetate, polyvinyl chloride, polystyrene, acrylic resins, polyester resins, polyurethanes, polycarbonates, phenolic resins, epoxy resins, polylactic acid (PLA resin), and mixtures or combinations thereof.

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 resin composition is a matrix resin mixed with a biodegradable baroplastic. In one embodiment, the biodegradable baroplastic is preferably a copolymer including a polymer segment including a unit derived from substituted or unsubstituted caprolactone and/or a polymer segment including a unit derived from substituted or unsubstituted trimethylene carbonate, and a polymer segment including a unit 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).

A resin composition according to one embodiment, which includes a matrix resin and a biodegradable baroplastic, has a melting point lower than that of the matrix resin before the biodegradable baroplastic is mixed therein. This is due to the fact that the biodegradable baroplastic contained in the resin composition according to one embodiment has a plasticizing effect on the resin. The lowered melting point of the resin composition according to one embodiment enables molding and processing under milder conditions. 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 under the action of water in the environment to become lower molecular weight. The resin composition according to one embodiment contains a biodegradable baroplastic that is particularly highly biodegradable in water, which facilitates biodegradation in the environment and reduces the burden on the environment.
In order to lower the melting point of the resin composition of one embodiment, it is preferable to include as much biodegradable baroplastic as possible. However, from the viewpoint of maintaining the physical and chemical properties of the matrix resin itself, the content of biodegradable baroplastic is set to about 10-50%, preferably 15-45%, and more preferably 20-40% by mass of the resin composition.
In one embodiment, the resin composition can be obtained by mixing a matrix resin and a biodegradable baroplastic, and is preferably obtained by mixing a molten matrix resin with a biodegradable baroplastic. The molten matrix resin and the biodegradable baroplastic can be mixed using, for example, an extruder. The resin composition in one embodiment obtained by mixing a matrix resin and a biodegradable baroplastic 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 biodegradable baroplastic. 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 biodegradable baroplastic, 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, comprising the step of molding a resin composition containing a matrix resin and a biodegradable baroplastic under a pressure of 10-50 MPa. In the second embodiment, the matrix resin is preferably selected from the group consisting of polyolefins, polyvinyl acetate, polyvinyl chloride, polystyrene, acrylic resins, polyester resins, polyurethanes, polycarbonates, phenolic resins, epoxy resins, polylactic acid (PLA resin), and mixtures or combinations thereof.

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).

In the resin composition to be molded in the second embodiment, the content of the biodegradable baroplastic is about 10-50%, preferably 15-45%, and more preferably about 20-40%, based on the mass of the resin composition.
The resin composition molded in the second embodiment can be obtained by mixing a matrix resin and a biodegradable baroplastic, and is preferably obtained by mixing a molten matrix resin with a biodegradable baroplastic. The molten matrix resin and the biodegradable baroplastic can be mixed, for example, using an extruder. The resin composition of the first embodiment obtained by mixing a matrix resin and a biodegradable baroplastic may be in any form, such as powder, granules, or pellets.

The resin composition molded in the second embodiment may further contain other resins in addition to the matrix resin and the biodegradable baroplastic. 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 molded in the second embodiment may contain, in addition to the matrix resin and the biodegradable baroplastic, 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 and a biodegradable baroplastic. Of these, 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. Therefore, the resin composition molded article produced in the second embodiment is highly biodegradable, particularly in water, and can reduce the burden on 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 composition molded article usable 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 burden on the environment.

The resin composition 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 biodegradable baroplastic, 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 molded in the second embodiment can be molded by applying pressure at temperatures near room temperature. Furthermore, the resin composition molded by the method of the second embodiment has a lower melting point than the resin that forms the matrix before the biodegradable baroplastic is mixed in (details will be described later), and therefore can be molded under conditions with a lower environmental impact.

A third embodiment of the present invention is a method for lowering the melting point of a resin, comprising the step of adding a biodegradable baroplastic to a matrix resin. In this third embodiment, the matrix resin is a resin that serves as a component that forms the matrix (continuous phase) in a resin composition obtained by mixing the matrix resin with other components. The matrix resin is preferably selected from the group consisting of polyolefins, polyvinyl acetate, polyvinyl chloride, polystyrene, acrylic resins, polyester resins, polyurethanes, polycarbonates, phenolic resins, epoxy resins, polylactic acid (PLA resins), and mixtures or combinations thereof.

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 method involves mixing biodegradable baroplastic into a matrix resin, thereby lowering the melting point of the matrix resin. The biodegradable baroplastic can be said to have the effect of plasticizing the matrix resin.

In the third embodiment, from the viewpoint of lowering the melting point of the matrix resin, the amount of biodegradable baroplastic added is about 10-50%, preferably 15-45%, and more preferably about 20-40% based on the mass of the resin composition.
Other resins may be further added to the resin composition whose melting point has been lowered by the method of the third embodiment. Examples of other resins include biodegradable resins such as polylactic acid, polycaprolactone, and polyhydroxyalkanoate. When other resins are further added, the amount of the other resins added may be 10% by mass or less, or 5% by mass or less, based on the total mass of the resins that form the matrix.
The resin composition whose melting point has been lowered by the method of the third 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.

In the third embodiment, the process of adding the biodegradable baroplastic to the matrix resin can be carried out by mixing the molten matrix resin with the biodegradable baroplastic, for example, using an extruder. The process of adding the biodegradable baroplastic to the matrix resin can be carried out at a temperature ranging from 100 to 300°C, preferably 150 to 250°C, depending on the matrix resin used. It is particularly preferable to knead the molten matrix resin with the biodegradable baroplastic at a temperature approximately 10 to 100°C higher than the melting point of the matrix resin used.

The resin composition whose melting point has been lowered by the method of the third embodiment is a resin composition containing a matrix resin and a biodegradable baroplastic. 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. Therefore, the resin composition whose melting point has been lowered by the method of the third embodiment is biodegradable in water under pressure, for example, in the deep sea. The resin composition whose melting point has been lowered by the method of the third embodiment accelerates the biodegradation of the biodegradable baroplastic portion, particularly in water. The resin composition whose melting point has been lowered by the method of the third embodiment can be used as any resin composition used at room temperature and pressure, and its lower melting point in particular allows it to be used in a wider range of applications.

The resin composition whose melting point has been lowered by the method of the third embodiment may be the resin composition of the first embodiment described above. As described above, the resin composition of the first embodiment contains a matrix resin and a biodegradable baroplastic, and therefore can be decomposed by contacting the resin composition with water.

The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following examples as long as it does not depart from the gist of the present 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 carried out for a further 24 hours at 110°C.

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 obtained in this manner was mixed with polylactic acid (homemade, weight-average molecular weight: 50 kDa) as a matrix resin in a mass ratio of 50:50 to obtain a resin composition.

Example 1: Lowering the melting point of a resin by adding a biodegradable baroplastic
The obtained resin composition was extrusion molded at a resin pressure of 50 MPa using a capillary rheometer (device name: CFT-500EX, Shimadzu Corporation). The relationship between the temperature of the extruder and the moving distance of the cylinder is shown in the graph in Figure 1.
As a control, polylactic acid alone, which was the matrix resin without the addition of the block copolymer, was extruded in the same manner as above. The relationship between the temperature of the extruder and the travel distance of the cylinder is shown in the graph in Figure 1.

As can be seen from the graph in Figure 1, the melting point of the resin composition of the present invention is approximately 10°C lower than that of the control PLA resin. By mixing a biodegradable baroplastic into a matrix resin, the matrix resin can be plasticized and its melting point can be lowered. Under pressure, the baroplastic block copolymer undergoes a phase transition from a phase-separated state to a compatible state, becoming fluid. At this time, the mobility of the poly(L-lactic acid) moiety (polymer segments containing units derived from lactic acid) in the block copolymer is improved, and the poly(L-lactic acid) matrix resin also becomes more fluid. This is thought to be the reason for the lower melting point of the resin composition.

Claims (3)

A resin composition comprising a matrix resin selected from polylactic acid (PLA resin) and a biodegradable baroplastic which 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 ,
The biodegradable baroplastic is contained in an amount of 10 to 50% based on the mass of the resin composition,
the 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; and
The resin composition is characterized in that 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 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 selected from polylactic acid (PLA resin) and a biodegradable baroplastic which is a copolymer containing 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, under a pressure of 10 to 50 MPa,
The biodegradable baroplastic is contained in an amount of 10 to 50% based on the mass of the resin composition,
the 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; and
The method for producing a resin composition is characterized in that 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 lowering the melting point of a resin , comprising the step of adding a biodegradable baroplastic, which 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, to a matrix resin selected from polylactic acid (PLA resin),
The biodegradable baroplastic is added in an amount of 10 to 50% based on the mass of a resin composition containing the matrix resin and the biodegradable baroplastic;
the 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; and
The method for lowering the melting point of a resin is characterized in that 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 is amorphous at room temperature and has a glass transition temperature of −30° C. or lower .