Method for producing polymer microparticle aggregate

Abstract

To provide a method for producing a polymer microparticle aggregate such as a film, having superior flexibility and mechanical characteristics and further having recyclability.SOLUTION: A polymer microparticle aggregate is obtained by annealing at 40-150°C, the aggregate comprising a copolymer of a rotaxane, which comprises a cyclic molecule and an axial molecule penetrating the cyclic molecule, the cyclic molecule or both the cyclic molecule and a linear molecule included therein having a group containing a polymerizable unsaturated group, and (meth)acrylate monomers comprising ethyl acrylate and a (meth)acrylic acid derivative other than ethyl acrylate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aggregate of polymeric fine particles, and more particularly to a method for producing an aggregate of polymeric fine particles that combines excellent mechanical properties with recyclability. [Background technology]

[0002] The present applicant has previously proposed polymeric particles made of a copolymer of a rotaxane having a cyclic molecule and an axial molecule passing through the cyclic molecule, and a (meth)acrylate (Patent Document 1, etc.).

[0003] Such polymer microparticle aggregates, for example, films made using polymer microparticles, have the advantage of being highly flexible. However, in recent years, with the trend toward higher performance in various components, there has been a demand for further improvements in mechanical properties, and from the perspective of preserving the global environment, there is also a demand for polymer microparticle aggregates that are also recyclable. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-91113 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing an aggregate of polymeric fine particles such as a film which is excellent in flexibility and mechanical properties and also has recyclability. [Means for solving the problem]

[0006] The object of the present invention is achieved by annealing at 40 to 150°C an aggregate of polymeric microparticles comprising a copolymer of a rotaxane, which is composed of a cyclic molecule and an axial molecule passing through the cyclic molecule, and in which either the cyclic molecule or the linear molecule enclosed therein both have a group containing a polymerizable unsaturated group, and a (meth)acrylate monomer composed of ethyl acrylate and a (meth)acrylic acid derivative other than ethyl acrylate. [Effects of the Invention]

[0007] In a method for producing a polymeric microparticle assembly consisting of a copolymer of a rotaxane having a cyclic molecule and an axial molecule passing through the cyclic molecule and a (meth)acrylate monomer, annealing the polymeric microparticle molding has the excellent effect of significantly improving the mechanical properties as well as flexibility.

[0008] Furthermore, such aggregates can be returned to the polymeric fine particle unit by using a polar solvent, and can therefore be recycled and reused as a material for polymeric fine particle moldings. DETAILED DESCRIPTION OF THE INVENTION

[0009] The rotaxane used is a rotaxane that is composed of a cyclic molecule, a linear molecule that encapsulates the cyclic molecule in a skewered manner, and a bulky end-blocking group that prevents the cyclic molecule from detaching from the linear molecule, and at least the cyclic molecule has a polymerizable unsaturated group or a group containing such a group.

[0010] The cyclic molecule constituting the rotaxane is a molecule in which a linear molecule is skewered and enclosed in its opening, and is not particularly limited as long as it has an OH group. It is preferably selected from, for example, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. The cyclic molecule may also be a crown ether or a crown ether derivative. The cyclic molecule may also have a group other than the active group, such as 2,6-dimethyl-β-cyclodextrin.

[0011] Examples of groups other than the active group include an acetyl group, a propionyl group, a hexanoyl group, a methyl group, an ethyl group, a propyl group, a 2-hydroxypropyl group, a 1,2-dihydroxypropyl group, a cyclohexyl group, a butylcarbamoyl group, a hexylcarbamoyl group, a phenyl group, a polycaprolactone group, an alkoxysilane group, a cinnamoyl group, a polymer chain (such as a polycaprolactone group or a polycarbonate group), or a derivative thereof. The active group may also be bonded to the cyclic molecule via a group other than the active group.

[0012] The linear molecule is not particularly limited as long as it can be included in the opening of the cyclic molecule in a skewered manner. Known linear molecules that are believed to form rotaxanes can be used. Polyethylene glycol, divalent aliphatic hydrocarbon groups, and more preferably alkylene groups are used. One or more carbon atoms constituting the divalent aliphatic hydrocarbon group may be replaced with -O-, -S-, -SO2-, -N(R)- (R: hydrogen atom or substituent), -CO-, -COO-, -CONR- (R: hydrogen atom or substituent), or a combination thereof. Hexafluorophosphate salts having an amino group are also preferred. Similar to the cyclic molecule, groups other than the active group may be directly bonded to the cyclic molecule.

[0013] From the viewpoint of improving mechanical properties, the linear molecule used has a carbon number of 4 to 12, preferably 6 to 10. Here, the carbon number of the linear molecule means the carbon number of the linear portion of the linear molecule, and does not include the carbon number of a terminal functional group or the carbon number of a substituent (for example, a polymerizable unsaturated group-containing group) that the linear molecule has.

[0014] The blocking groups are not particularly limited, as long as they are positioned at both ends of the linear molecule and act to prevent the cyclic molecules from being released. For example, the blocking group may be selected from the group consisting of dinitrophenyl groups, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, pyrenes, unsubstituted or substituted benzenes (substituents include, but are not limited to, alkyl, alkoxy, hydroxy, halogeno, cyano, sulfonyl, carboxyl, amino, phenyl, etc., and one or more substituents may be present), optionally substituted polynuclear aromatics (substituents include, but are not limited to, the same as those described above, and one or more substituents may be present), and steroids. Dinitrophenyl groups, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, or pyrenes are preferred, with adamantane groups or trityl groups being more preferred. Dimethylphenyl isocyanate is also preferred.

[0015] Commercially available rotaxanes can be used as they are, such as SH3400P manufactured by Advanced Soft Materials, and Selm Key Mixture SA2400C and Selm Key Mixture SM2400C, both of which are also manufactured by Advanced Soft Materials.

[0016] A polymerizable unsaturated group, which is a reactive functional group, or a group containing such a group is introduced into both the cyclic molecule or the cyclic molecule and the linear molecule enclosed therein. When a polymerizable unsaturated group or a group containing such a group is introduced into both the cyclic molecule and the linear molecule enclosed therein, even a single molecule of a cyclic molecule such as crown ether or cyclodextrin will exhibit the function (sliding effect) of a rotaxane copolymer, and further improvement in flexibility can be expected.

[0017] Examples of polymerizable unsaturated groups include vinyl groups, acrylic groups, acryloyl groups, methacrylic groups, methacryloyl groups, acryloyloxy groups, and methacryloyloxy groups, with acryloyloxy groups and methacryloyloxy groups being preferred. The introduction of the polymerizable unsaturated group is carried out using 2-isocyanatoethyl methacrylate or the like. Examples of groups containing polymerizable unsaturated groups include (=O)NHC2H4OC(=O)CH=CH2, -C(=O)NHC2H4OC(=O)C(CH3)=CH2, (=O)NHC6H4OC(=O)CH=CH2, and (=O)NHC6H4OC(=O)C(CH3)=CH2, which contain acryloyloxy and methacryloyloxy groups.

[0018] The introduction of a polymerizable unsaturated group or a group containing such a group into a cyclic molecule or a linear molecule to be included therein is carried out by mixing the cyclic molecule or the cyclic molecule with the linear molecule to be included in the cyclic molecule, and after the inclusion, introducing the polymerizable unsaturated group or a group containing such a group into a hydroxyl group or the like of the cyclic molecule (and the linear molecule) by an esterification reaction or the like, thereby obtaining a rotaxane having a polymerizable unsaturated group.

[0019] Rotaxanes having a polymerizable unsaturated group or a group containing a polymerizable unsaturated group are copolymerized with (meth)acrylate group-containing monomers consisting of ethyl acrylate and other (meth)acrylic acid (derivatives). The copolymerization of a rotaxane having a polymerizable unsaturated group or a group containing a polymerizable unsaturated group with a (meth)acrylate group-containing monomer is carried out using about 0.001 to 10 mol%, preferably about 0.01 to 1 mol%, of the former and about 99.999 to 90 mol%, preferably about 99.99 to 99 mol%, of the total amount of both. In other words, the rotaxane having a polymerizable unsaturated group or a group containing a polymerizable unsaturated group acts as a crosslinking group in the resulting rotaxane copolymer.

[0020] Examples of (meth)acrylic acid (derivatives) other than ethyl acrylate include ethyl methacrylate, acrylic acid or methacrylic acid, and alkyl or alkenyl esters of these having 50 or less carbon atoms, such as propyl, hexyl, 2-ethylhexyl, octyl, oleyl, palmityl, and stearyl, and preferably methoxyethyl (meth)acrylate. Ethyl acrylate and the (meth)acrylic acid (derivative) are used in a ratio of 5 to 95 mol %:95 to 5 mol %, preferably 20 to 80 mol %:80 to 20 mol %.

[0021] In addition to the above-mentioned essential components, rotaxane and acrylate group-containing monomer, other monomers may be used in an amount of less than 10 mol % of the total monomers, provided that the object of the present invention is not impaired.

[0022] The copolymerization reaction is carried out by any polymerization method, such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization, in the presence of a commonly used radical initiator, preferably emulsion polymerization. The radical initiator can be a redox system using tert-butyl hydroperoxide and sodium formaldehyde sulfoxylate, or ammonium persulfate and sodium hydrogen sulfite, preferably tert-butyl hydroperoxide and sodium formaldehyde sulfoxylate. In the case of emulsion polymerization, the polymerization reaction is carried out in the presence of various surfactants. A chain transfer agent can be used during the polymerization reaction.

[0023] Examples of surfactants that can be used include sodium lauryl sulfate, sodium oleate, sodium alkylsulfonate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, etc., or their corresponding potassium salts or calcium salts, polyoxyethylene lauryl ether, polyethylene glycol fatty acid esters, polyoxyethylene alkylaryl sodium, etc., and preferably sodium lauryl sulfate and polyoxyethylene lauryl ether are used.

[0024] As the chain transfer agent, n-dodecyl mercaptan, octyl mercaptan, α-methylstyrene dimer, 1,4-terpinolene, etc. are used, and preferably n-dodecyl mercaptan is used. When the amount of n-dodecyl mercaptan is increased, the molecular weight of the resulting copolymer decreases, and the breaking strength and Mooney viscosity ML 1+4 The chain transfer agent is used in an amount of about 0.001 to 0.05% by weight, preferably about 0.0035 to 0.01% by weight, based on the total amount of charged monomers.

[0025] The polymerization reaction is carried out by any method, such as a batch method or a continuous or intermittent addition method, at a temperature of about -10 to 100°C, preferably about 2 to 80°C. Separation of the copolymer after completion of the reaction is carried out in different ways depending on the polymerization method. For example, in the case of emulsion polymerization or suspension polymerization, it is carried out by adding a coagulant such as an acid or a polyvalent metal salt to the reaction mixture as necessary, and the separated copolymer is subjected to a washing and drying process. During the emulsion polymerization reaction, crosslinking by self-crosslinking also occurs simultaneously.

[0026] The resulting polymer microparticles are in the form of fine particles with a harmonic mean diameter Dh of about 2000 nm or less, preferably about 1500 to 50 nm, and more preferably 500 to 50 nm, and a molecular weight of about 300 to 100,000. The harmonic mean diameter Dh is the harmonic mean diameter in dimethylformamide measured by the cumulant method using a particle size analyzer (Zetasizer Nano S, a product of Malvern Instruments).

[0027] The obtained polymer microparticles can be dried for about 1 to 72 hours using, for example, a silicone sheet mold of the desired sheet shape to produce a polymer microparticle molded product such as a film. Further annealing at about 40 to 150°C, preferably 50 to 120°C, for about 1 to 240 hours, preferably 3 to 120 hours, can produce a polymer microparticle aggregate with improved mechanical properties. For example, a film of the annealed polymer microparticle aggregate with a thickness of 1 mm has a breaking energy of 18 KJ / m 2On the other hand, if no annealing is performed, the breaking energy of the resulting film is 8 KJ / m 2 This makes it difficult to achieve the object of the present invention, which is to ensure excellent mechanical properties such as flexibility and toughness.

[0028] The obtained film has excellent mechanical properties such as toughness, but the polymeric microparticles can be regenerated by immersing it in an organic solvent such as ethanol, methanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, ethylamine, or diethylamine at 70°C for about 1 hour, and the film can be recycled by using it to produce new films, etc. In this case, the amount of polar solvent used should be sufficient to fully immerse the film, and an amount about 2 to 100 times the volume of the film is generally used. [Example]

[0029] Next, the present invention will be described with reference to examples.

[0030] Example A solution consisting of 160 g of a mixed monomer consisting of 64.97 mol% ethyl acrylate, 34.98 mol% methyl methacrylate, and 0.05 mol% rotaxane A, 0.1 g of sodium dodecylbenzenesulfonate (surfactant; Tokyo Chemical Industry Co., Ltd.), 0.46 g of hexadecane (Kanto Chemical Hydrophobe), and 36 g of water was emulsified by ultrasonic irradiation at 375 W for 3 minutes using an ultrasonic homogenizer. 0.1 g of potassium persulfate (polymerization initiator) was then added to the resulting emulsion and polymerized at 70°C for 4 hours with a stirring speed of 200 rpm to obtain polymer microparticles. Rotaxane A was synthesized as follows.

[0031] -Synthesis of the axial portion precursor- 2.9 g of 6-amino-1-hexanol was added to a solution of 3.3 g of 3,5-dimethylbenzaldehyde in 250 ml of tetrahydrofuran and stirred overnight at room temperature. The solvent was then removed by distillation, and the residue was dissolved in 250 ml of methanol and added dropwise to 2.9 g of NaBH4. The resulting mixture was stirred at room temperature for 5 hours, and after distillation of the solvent, the residue was dissolved in 100 ml of chloroform. The organic phase was washed with distilled water. The resulting organic phase was dried over magnesium sulfate, and the organic solvent was removed by distillation to obtain 5.8 g of N-(3,5-dimethylbenzyl)-6-hydroxyhexylamine as a colorless oil.

[0032] Next, the obtained N-(3,5-dimethylbenzyl)-6-hydroxyhexylamine was dissolved in 100 ml of methanol, and 8 ml of 12N aqueous hydrochloric acid was added. This mixed solution was added dropwise to 1 L of diethyl ether, and the resulting precipitate was filtered to obtain a solid component. The obtained solid component was added to a saturated aqueous solution of hexafluorophosphate ammonium salt, and this solution was added dropwise to methanol to obtain a precipitate. After filtering the obtained precipitate, the solid component was washed with water and dried to obtain 1.4 g of N-(3,5-dimethylbenzyl)-6-hydroxyhexylammonium hexafluorophosphate salt as a white solid.

[0033] - Synthesis of cyclic molecules - To a solution of 1.9 g of hydroxymethyldibenzo-24-crown-8-ether in 45 ml of methylene chloride, 1.4 ml of 2-isocyanatoethyl methacrylate and 0.2 ml of dibutyltin dilaurate were added at 0°C and stirred at room temperature for 48 hours. The resulting mixture was concentrated to 10 ml and poured into hexane to obtain a precipitate. The precipitate was dissolved in an ethyl acetate / hexane mixture (volume ratio 2 / 3) and purified on a silica column to obtain 2.5 g of cyclic molecule A.

[0034] - Synthesis of Rotaxane A - 150 mg of N-(3,5-dimethylbenzyl)-6-hydroxyhexylammonium hexafluorophosphate salt and 260 mg of cyclic molecule A were dissolved in 1 mL of methylene chloride and irradiated with ultrasound at room temperature until the mixture became clear. 1 mg of dibutyltin dilaurate and 160 mg of 3,5-dimethylphenyl isocyanate were added to the solution and stirred at room temperature for 5 hours. Methanol was then added to the solution to deactivate unreacted isocyanate. After distilling off the volatile components, the residue was dissolved in 4 mL of tetrahydrofuran. 810 mg of triethylamine and 620 mg of 2-isocyanatoethyl methacrylate were added to the tetrahydrofuran solution and stirred at room temperature for 2.5 days. After distilling off the volatile components from the solution, the solution was purified using a column to obtain 290 mg of rotaxane A (MW 1171). TIFF2025133607000001.tif78153

[0035] A mixture solution (containing 99.95 mol% of a polymerizable unsaturated group-containing monomer (ethyl acrylate: methyl methacrylate 65:35 mol%) and 0.05 mol% of rotaxane A) (containing 100g of water, sodium dodecylbenzenesulfonate, and hexadecane) was emulsified by ultrasonic irradiation in an ultrasonic homogenizer at 375W for 3 minutes. 0.1g of potassium persulfate was added to the resulting emulsion, and the resulting emulsion was polymerized at 70°C for 4 hours with a stirring speed of 200 rpm. 2.30g of polymeric microparticles, a crosslinked copolymer of these copolymers, was obtained. The harmonic mean diameter (Dh) of the resulting microparticles was measured and found to be 103nm.

[0036] After centrifugal purification and dialysis of the polymer microparticles, 7 ml of a 5% by mass dispersion of the microparticles was poured into a silicone rubber mold with a 3.5 x 3.5 cm square cavity, and allowed to air dry at room temperature for 24 hours to produce a polymer microparticle film with a thickness of approximately 0.1 mm. The polymer microparticle film was then annealed in an oven at 70°C for 10 hours.

[0037] Comparative Example 1 In the example, a mixed monomer consisting of 65 mol % of ethyl acrylate and 35 mol % of methyl methacrylate was used, and polymeric microparticles with a harmonic mean diameter Dh of 92 nm were obtained without annealing the polymeric microparticle molded film.

[0038] Comparative Example 2 The polymeric microparticle molded film obtained in Comparative Example 1 was annealed in an oven at 70° C. for 10 hours to obtain polymeric microparticles having a harmonic mean diameter Dh of 92 nm.

[0039] Comparative Example 3 In the example, polymeric microparticles having a harmonic mean diameter Dh of 103 nm were obtained without annealing the polymeric microparticle molded body.

[0040] Comparative Example 4 In Comparative Example 2, a mixed monomer consisting of 65 mol % of n-butyl acrylate and 35 mol % of methyl methacrylate was used to obtain polymeric fine particles having a harmonic mean diameter Dh of 95 nm.

[0041] Comparative Example 5 In the examples, a mixed monomer consisting of 65 mol % of n-butyl acrylate, 35 mol % of methyl methacrylate, and 0.03 mol % of rotaxane A was used to obtain polymeric microparticles with a harmonic mean diameter Dh of 106 nm.

[0042] Four films measuring 1 x 3.5 cm were cut out from the films obtained in the above Examples and Comparative Examples to prepare test pieces, which were then evaluated for breaking strength, elongation at break, breaking energy, film tensile test, and recyclability. Breaking strength, elongation at break, breaking energy: The test piece was cut 2 mm into the center of the longitudinal direction using a diamond cutter. A Tensilon tensile tester was used to measure the load cell. The tensile test was carried out under the conditions of a tension of 50N, an elongation rate of 10mm / min, and a temperature of 25°C. The value of Comparative Example 1 was set to 100. The larger the value, the better, and the greater the toughness. Film tensile test: Under the conditions of JIS K 6250, the film was stretched at 300% and 500% elongation. Count the number of fissures Recyclability: After immersion in 80% ethanol at 70°C for 1 hour, the particle size was measured before and after decomposition. Since the difference in particle size is within 10%, it is evaluated as being recyclable. Price

[0043] The results obtained are shown in the following table. Note that the items shown as indices are converted with the value of Comparative Example 1 set at 100. table Comparative Example Measurement items Example 1 2 3 4 5 Breaking strength (index) 881 100 362 224 41 83 Elongation at break (index) 127 100 97 119 66 55 Breaking energy (index) 428 100 210 121 16 91 Film Tensile Test Number of cracks (elongation ratio 300%) 0 10 6 1 Fracture Fracture Number of cracks (elongation ratio 500%) 0 Break Break 10 Break Break Recyclability ○ ○ ○ ○ ○ ○

Claims

1. A method for producing polymer particle aggregates, in which a molded product of polymer particles consisting of a copolymer of a rotaxane, which consists of a cyclic molecule and an axial molecule that passes through the cyclic molecule, and in which either the cyclic molecule or the linear molecule enclosed by it both have a polymerizable unsaturated group or a group containing such a group, and a (meth)acrylate group-containing monomer consisting of ethyl acrylate and a (meth)acrylic acid (derivative) other than ethyl acrylate, is annealed at 40 to 150°C.

2. 2. The method for producing polymeric fine particle aggregates according to claim 1, wherein the polymerizable unsaturated group is a vinyl group, an acrylic group, a methacrylic group or a methacryloyl group.

3. 2. The method for producing polymeric microparticle aggregates according to claim 1, wherein the axial molecule has 4 to 12 carbon atoms.

4. 2. The method for producing polymeric particle aggregates according to claim 1, wherein a rotaxane is used in which both the cyclic molecule and the axial molecule have a polymerizable unsaturated group or a group containing such a group.

5. The method for producing polymeric microparticle aggregates according to claim 1, wherein the rotaxane having a polymerizable unsaturated group or a group containing the same is used in an amount of 0.001 to 10 mol % based on the total amount of ethyl acrylate and the (meth)acrylic acid (derivative) other than ethyl acrylate.

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