JP2002173535A - Method for producing water dispersion of biodegradable polyester resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for readily inexpensively producing a water dispersion composition having excellent preservation stability and capable of forming a coated film having excellent biodegradability and water resistance without requiring special equipment and complex operation while extremely reducing the amount of a used organic solvent. SOLUTION: This method for producing the water dispersion of the biodegradable polyester resin comprising (A) the biodegradable polyester, (B) a basic compound, (C) an organic solvent and (D) water comprises a dispersing step, a heating step, an emulsifying step and a cooling step. The whole of the component A, and the whole or a part of the component B and C are roughly dispersed in an aqueous medium by stirring at the dispersing step. At the heating step and the emulsifying step, the remaining components are added thereto under stirring before the finish of the emulsifying step, and the resultant mixture is heated to the temperature not less than the higher temperature of 60 deg.C and the glass transition temperature of the component A. The heated mixture is continuously stirred until the content of coarse particles of the biodegradable polyester resin, having the particle diameter not less than 20 μm becomes <=1 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for producing an aqueous dispersion comprising a biodegradable polyester resin.

[0001]

2. Description of the Related Art Conventional solvent-based paints include organic solvents and therefore have the danger of ignition and the like, and also have problems such as environmental pollution. In recent years, regulations on volatile organic compounds (VOCs) have become particularly strict, and in the field of paints and coatings, the form is shifting to aqueous dispersions, powder paints, ultraviolet / electron beam curable paints, and the like. Among them, aqueous dispersions or aqueous emulsions have the advantage that they have little impact on the environment and are liquid like solvent-based paints, so that they have the advantage of being able to use the current paint production and painting lines almost as they are, and therefore have to use alternative technologies. The most promising of them.

In recent years, due to environmental considerations, biodegradable resins that do not rely on petroleum raw materials and have little environmental impact even at the time of disposal have attracted attention. Therefore, it is considered that the use of a biodegradable resin as the resin for an aqueous dispersion can provide an extremely environmentally friendly aqueous dispersion.

[0003] Some proposals have been made on aqueous dispersions of biodegradable resins. JP-A-9-77910
And the like, starch derivatives are described in Japanese Patent Application Laid-Open Publication No. 9-97036, polyhydroxyalkanoates are described in WO9704036, polycaprolactone is described in Colloid Polymer Journal, Vol. 273, p. Aliphatic polyesters composed of acids and glycols are each disclosed. However, these biodegradable resins have a low melting point or decomposition temperature, so that the usable temperature range is limited.

[0004] Among the biodegradable resins, polylactic acid has a relatively high melting point or softening point of about 100 to 170 ° C and is excellent in water resistance, so that it is suitable as a coating material and a coating material. Regarding this polylactic acid-based aqueous dispersion, research on microencapsulation for the purpose of sustained release of a drug has been actively conducted. For example, JP-A-63-1
Japanese Patent Application Laid-Open Nos. 22620, 5-58882, 6-72863, and 9-110678 disclose a microencapsulation technique using a lactic acid-based polymer. In these, a lactic acid-based polymer is dissolved in an organic solvent, and the drug is dissolved or dispersed therein. /
A method of forming a W) type emulsion is employed. Microcapsules obtained by these methods have no self-dispersibility because the constituent polymer does not have sufficient hydrophilicity, and it is essential to add an auxiliary agent such as a surfactant having a surfactant action. Was significantly reduced due to the addition of the compound. Further, there is a problem that a large amount of an organic solvent is required to once dissolve the resin.

[0005] Japanese Patent Application Laid-Open No. 10-101911 discloses a technique relating to a polylactic acid-based biodegradable aqueous dispersion using an anionic emulsifier. The decrease in water resistance was remarkable.

Japanese Unexamined Patent Publication No. 12-7789 discloses a technique relating to self-dispersing particles composed of biodegradable polyester such as polylactic acid and a method for producing the same. In this case, the production method is a phase inversion emulsification method. In the manufacturing process, it is necessary to use a large amount of an organic solvent such as methylene chloride or chloroform, which is not preferable in terms of working environment,
There were problems that it was difficult to completely remove these solvents from the obtained aqueous dispersion, and that the effects on the surrounding environment could not be ignored because the solvent distillation and recovery steps were not completely closed systems.

Further, a method has been found in which a uniform and stable aqueous dispersion is obtained from an aromatic polyester resin having a specific acid value while greatly reducing the amount of an organic solvent used (Japanese Patent Laid-Open No. 9-1997). No. -296100), no biodegradability was observed in these aromatic polyester resins.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to greatly reduce the amount of organic solvent used, without using special equipment and complicated operations. An object of the present invention is to provide a method for producing an aqueous dispersion composition that can easily and inexpensively form a coating film having excellent storage stability and excellent biodegradability and water resistance.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, when obtaining an aqueous dispersion from a biodegradable polyester resin mainly composed of polylactic acid, a small amount of a base is required. It has been found that a uniform and stable aqueous dispersion can be obtained by heating and stirring in the presence of an amphoteric compound and an amphipathic solvent without dissolving the resin in an organic solvent.

That is, the gist of the present invention is a method for producing an aqueous dispersion of a biodegradable polyester resin containing the following components (A) to (D) and having a total of 100% by mass. And a cooling step. In the dispersing step, all of the following components (A) and all or a part of the components (B) and (C) are coarsely dispersed in an aqueous medium with stirring.
In the heating step and the emulsifying step, before the emulsifying step is completed, the remaining components are added with stirring, and the mixture is heated to 60 ° C. or higher than the higher of the glass transition temperatures of the components (A). A method for producing an aqueous dispersion of a biodegradable polyester resin, comprising continuously stirring until the coarse particles of the biodegradable polyester resin having a diameter of 20 μm or more become 1% by mass or less. (A) The lactic acid unit contains 50 mol% or more, the D-form content in the lactic acid unit is 0.1 to 25 mol%, and the acid value is 5 to 50 KO.
Hmg / g biodegradable polyester resin 10-60
(B) a basic compound, (C) 0.1 to 30% by mass of an amphiphilic organic solvent having a plasticizing ability with respect to a biodegradable polyester resin, and (D) water.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Biodegradable polyester resin (A) used in the present invention
Is a lactic acid-based polymer containing a lactic acid unit as a main component, and is an essentially hydrophobic polymer that does not disperse or dissolve alone in water. Hereinafter, the components of the biodegradable polyester resin will be described.

The biodegradable polyester resin used in the present invention includes a homopolymer of lactic acid or lactic acid and another hydroxycarboxylic acid such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, and 4-hydroxybutyric acid. Copolymers of valeric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid, etc., or copolymers of lactic acid and aliphatic carboxylic acids and glycols, or polylactic acid and other polyhydroxycarboxylic acids, polycaprolactone Or a mixture with an aliphatic polyester or the like. The lactic acid unit in the biodegradable polyester resin must be at least 50 mol%, preferably at least 70 mol%, more preferably at least 90 mol%. Lactic acid unit is 50
If the amount is less than mol%, the heat resistance of the resin film obtained from the aqueous dispersion is low, which is not practical.

Further, the content of D-lactic acid in the lactic acid unit is as follows:
It is necessary to be 0.1 to 25 mol%, preferably 0.5 to 20 mol%, more preferably 2 to 15 mol%. When the content of D-lactic acid is less than 0.1%,
Since it is difficult to swell or dissolve in an amphiphilic organic solvent, it is difficult to disperse in water by the method of the present invention. When the content of D-lactic acid is 25% or more, the glass transition temperature tends to decrease, and the heat resistance of the resulting coating tends to decrease.

In the present invention, the acid value of the biodegradable polyester resin needs to be 5 to 50 mgKOH / g, and particularly preferably 10 to 40 mgKOH / g. If the acid value exceeds 50 mgKOH / g, the water resistance of the formed coating film may be poor. On the other hand, the acid value is 5 mgKOH
If it is less than / g, the amount of carboxyl groups contributing to emulsification is not sufficient, and a good aqueous dispersion composition cannot be obtained. Further, such a biodegradable polyester resin is GPC
(Number average molecular weight measured by gel permeation chromatography, polystyrene conversion) is 2,000 to 4
Must be in the range of 0000. And three
It is preferably in the range of 000 to 20,000. If it is less than 2,000, sufficient strength and workability cannot be imparted to the coating film formed from the aqueous dispersion composition. If it exceeds 40,000, the amount of carboxyl groups contributing to emulsification cannot be sufficiently imparted, and not only a good aqueous dispersion composition cannot be obtained, but also the viscosity becomes abnormally high, and The workability may be deteriorated.

The carboxyl group, whose content is expressed as the acid value of the biodegradable polyester resin, is a functional group necessary for forming (emulsifying) fine particles of the biodegradable polyester resin. It is more preferable that the carboxyl group be unevenly distributed at the terminal of the resin molecular chain than in the resin skeleton, from the viewpoint of the stability of the obtained aqueous dispersion composition and the water resistance of the formed coating film. As a method for introducing a specific amount of carboxyl group to the molecular chain terminal without side reaction or gelation, a method of depolymerizing a high molecular weight biodegradable polyester resin using a polybasic acid component, A method of adding a polybasic acid component after the start of the condensation reaction, a method of adding an acid anhydride of a polybasic acid immediately before the end of the polycondensation reaction, a low molecular weight polyester resin in which most of the molecular chain ends are carboxyl groups And a method of depolymerizing with a polybasic acid component, and a method of adding the polybasic acid component after the start of the polyester polycondensation reaction.

As the polybasic acid and its acid anhydride used for introducing a carboxyl group into the biodegradable polyester resin, known ones can be used. Specifically, succinic acid, succinic anhydride, adipic acid , Sebacic acid, terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, benzophenonetetracarboxylic acid, benzophenonetetracarboxylic anhydride, trimesic acid, ethylene glycol bis ( Anhydrotrimellitate), glycerol tris (anhydrotrimellitate), 1,2,2
Examples thereof include 3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, and among them, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 1,2,3- Propanetricarboxylic acid,
1,2,3,4-butanetetracarboxylic acid is preferably used.

In the present invention, the content of the biodegradable polyester resin in the aqueous dispersion composition should be appropriately selected depending on the use, dry film thickness, coating method and the like.
It is preferably 60% by mass, particularly preferably 20 to 50% by mass. When the content is less than 10% by mass, it takes a long time to dry the coating film. When the content exceeds 60% by mass, the viscosity of the aqueous dispersion composition becomes extremely high, and it may be difficult to mix and apply other components.

In the aqueous dispersion composition of the present invention, it is necessary to use a basic compound in order to prevent aggregation between resin fine particles. This basic compound neutralizes the carboxyl groups in the biodegradable polyester resin during emulsification, and by the electric repulsion between carboxy anions generated by the neutralization reaction, or with a small amount of a specific surfactant described later. Combination prevents aggregation between polyester resin particles,
It contributes to excellent storage stability as a water dispersion composition.
As the basic compound, a compound which volatilizes by heating at the time of forming a coating film is preferable, and ammonia and / or a boiling point of 2
Organic amine compounds having a temperature of 50 ° C. or lower can be suitably used.

Examples of the organic amine compound include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, n-butylamine, and
c-butylamine, tert-butylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N-methyl-N, N-diethanolamine, aminoethanolamine, 3- Examples thereof include methoxypropylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, methylaminopropylamine, dimethylaminopropylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Triethylamine can be suitably used because it is easily available.

The amount of the basic compound to be added is such that the carboxyl groups contained in the biodegradable polyester resin can be partially neutralized, that is, 0.5 to 0.5 with respect to the carboxyl groups.
It is preferable to add 1.5 equivalents. If the amount is less than 0.5 times equivalent, the effect of adding the basic compound is small, and if it exceeds 1.5 times equivalent, the aqueous dispersion composition may be significantly thickened or the storage stability may be reduced.

In the present invention, an amphiphilic and biodegradable polyester resin is used for the purpose of ensuring the stability of the resulting aqueous dispersion composition or for the purpose of accelerating the emulsification treatment speed described below. Requires an organic solvent having a chemical conversion ability. The organic solvent has a boiling point of 100 ° C. or lower and can be azeotropic with water, and has low toxicity, explosiveness and flammability.
General-purpose organic solvents are preferred. Those having a boiling point of 100 ° C. or higher or not azeotropic with water are difficult to sufficiently remove in a later step. In the present invention, an amphiphilic organic solvent is defined as having a solubility in water at 20 ° C. of 5
g / L or more. In particular, a solubility of 10
It is preferable to use one having g / L or more. When the solubility in water is less than 5 g / L, the effect of accelerating the emulsification treatment is poor, and the stability of the aqueous dispersion composition is liable to decrease.

The ability of the organic solvent to plasticize the biodegradable polyester resin can be evaluated as a degree of swelling or solubility by a simple test. That is,
The degree of swelling is as follows. A resin piece having a particle size of 1 to 5 mm is stirred at 60 ° C. for 1 hour in an organic solvent having a mass ratio of 10 times, then the resin piece is immediately taken out, and the organic solvent adhering to the surface is wiped to remove the mass. It is measured and expressed as a ratio to the dry mass. When a part or all of the resin pieces dissolve, the solubility can be measured and calculated from the dry mass of the residual resin or the dry mass of the dissolved component obtained by evaporating the organic solvent in which the resin is dissolved. . If the swelling degree thus evaluated is 1.02 or more or the solubility is 0.01 g / g or more, it is determined that the organic solvent has a plasticizing ability. An organic solvent judged to have no plasticizing ability is poor in the effect of accelerating the emulsification treatment speed and the effect of stabilizing the resin fine particles dispersed in the aqueous medium.

Examples of such amphiphilic organic solvents include alcohols such as ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol and tert-amyl alcohol, isopropyl ether, tetrahydrofuran and dioxane. Ethers, ketones such as methyl ethyl ketone, diethyl ketone, etc., esters such as ethyl acetate, n-propyl acetate, isopropyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, ethylene glycol dimethyl ether, propylene Glycol derivatives such as glycol dimethyl ether,
Acetonitrile and the like can be exemplified. These solvents may be used alone or in combination of two or more.
Among them, isopropanol, ethyl acetate and acetonitrile are preferable, and can be appropriately selected according to the crystallinity (D-form content) of the resin.

When emulsifying, the amphiphilic organic solvent must be contained in an amount of 0.1 to 30% by mass, preferably 1 to 20% by mass, based on the aqueous dispersion composition. When the amount is less than 0.1% by mass, the effect of accelerating the emulsification treatment is poor, and the stability, coating film forming property and adhesiveness of the aqueous dispersion composition are poor. On the other hand, when the content of the organic solvent with respect to the aqueous dispersion composition exceeds 30% by mass, not only the original purpose of the aqueous dispersion called “low organic solvent” is lost, but also the aqueous dispersion composition is abnormal. Liable to increase the viscosity or decrease the storage stability. Such amphiphilic organic solvents have a boiling point of 10
If the temperature is 0 ° C. or lower or if azeotropic with water, part or all of it can be easily removed (stripping) out of the system during or after the emulsification step described below, and finally the water dispersion It can be 0.01 to 20% by mass, more preferably 0.01 to 10% by mass, based on the body composition.

In the present invention, in the above-mentioned step of removing (stripping) the organic solvent out of the system, a surfactant is used for the purpose of ensuring the storage stability of the aqueous dispersion composition and the mixing stability with other components. It is preferred to use The surfactant referred to in the present invention has a function of adsorbing on the surface of resin fine particles in an aqueous medium, exhibiting a stabilizing effect, and preventing aggregation between resin fine particles. Such a surfactant is used in an amount of 2% by mass or less, preferably 1% by mass or less with respect to the biodegradable polyester resin, and remarkably enhances the above-mentioned various stability without deteriorating various properties of a formed coating film. Can be improved. Also, by using a surfactant,
There is also an effect that the acid value of the polyester resin and the content of the amphiphilic organic solvent can be reduced.

Specifically, fully or partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyvinyl alcohols such as α-olefin-vinyl alcohol copolymer, polyoxyethylene alkyl ether, polyoxyethylene Polyoxyethylenes such as fatty acid esters,
Carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, oxidized starch,
Examples include polysaccharides such as etherified starch and gum arabic, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, and a polymer of a vinyl monomer containing acrylic acid and / or methacrylic acid as one component.

In the present invention, the desired aqueous dispersion composition can be easily and inexpensively produced by using the above-mentioned components by the following method without using special equipment and complicated operations. Can be. That is, this production method comprises substantially four steps of a dispersing step, a heating step, an emulsifying step and a cooling step. In the dispersing step, all of the component (A) which is the biodegradable polyester resin is stirred under stirring. And all or part of the components (B) and (C) are coarsely dispersed in an aqueous medium, and in the heating step and the emulsifying step, before the emulsifying step is completed (under the conditions of the examples of the present invention, the emulsifying step 20 minutes before the end), after or while adding the remaining components with stirring, the mixture is heated to 60 ° C. or higher, which is the higher of the glass transition temperature of the polyester resin. % (At this temperature for 20 to 100 minutes under the conditions of the examples of the present invention), thereby achieving fine particles of the resin. In the cooling step, the obtained aqueous dispersion is obtained. With room temperature Up to is that to cool. All of these are indispensable steps and must be performed continuously in order to obtain the aqueous dispersion composition intended for the present invention.

As the treatment apparatus, any apparatus can be used as long as it can appropriately stir a mixture of an aqueous medium and a resin powder or a granular material and the like and can heat the inside of the tank to 60 ° C. or more. Devices widely known to those skilled in the art can be used as a stirring device or an emulsifying device. Examples of such a device include a uniaxial stirrer such as a propeller mixer and a turbine mixer, and a turbine / stator type high-speed rotary stirrer (TK Homo-Mixer, manufactured by Tokushu Kika Kogyo Co., Ltd.).
T. K. Homo-Jettor, IKA-MASCH
INENBAU (Ultra-Turrax), a compound stirrer equipped with a high-speed shearing type mixer and a low-speed sliding type kneading paddle with a scraper for scraping the tank wall and an anchor mixer (manufactured by TK. Agi-Homo
-Mixer, T .; K. Combimix). The processing apparatus may be of a batch type or a continuous production type in which the input of raw materials and the removal of the processed product are continuously performed. The treatment tank is preferably one that can be sealed. Examples of a method of charging the raw materials into such a processing apparatus include a method of charging all the raw materials collectively into a tank, and a method of charging a part of the raw materials first and sequentially charging the remaining raw materials at a certain stage.

In the production method of the present invention, the entire amount of the biodegradable polyester resin must be introduced during the dispersion step. When charged after the heating step, the powder is heated to a temperature equal to or higher than the glass transition temperature without stirring or with insufficient stirring speed, so that the biodegradable polyester resin in the form of powder, granules, or pellets is likely to cause blocking. Once blocked, complete emulsification is not achieved, no matter how fast stirring. The other raw materials (B) and (C) can be charged into the tank at any stage from the dispersion step to the emulsification step, but before the emulsification step described below is completed (see Examples of the present invention). Under the conditions, 20 minutes before the end of the emulsification step), it is necessary to put all of them into the tank. When introduced in the cooling step, the resulting aqueous dispersion composition tends to have poor storage stability. When adding a surfactant, it is preferable to dissolve or uniformly disperse the surfactant in an aqueous medium in advance, and to add the surfactant before the emulsification step.

The dispersing step is carried out for the purpose of preventing the polyester resin from agglomerating, and is usually carried out by stirring at room temperature. However, if the subsequent heating step requires time,
The dispersion step may be performed while heating the inside of the tank. At that time, it is necessary to uniformly disperse the polyester resin powder or granules in an aqueous medium until the temperature in the tank reaches 40 ° C. The aqueous medium in the present invention is water or a mixture of water and the organic solvent and / or the basic compound and / or the surfactant. The end point of the dispersion step, that is, the state in which the polyester resin powder or the particulate matter is uniformly dispersed in the aqueous medium is described in T.I. N. Zwiretering (Ch
electronic Engineering Science
e, Vol. 8, p. 244, 1958), which means a state in which no particles remain at the bottom of the tank for more than 1 to 2 seconds. It is preferable that the stirring is performed at a completely floating stirring speed NJS or more that achieves the “state”. The stirring state in the tank can usually be easily determined visually. The perfect floating stirring speed depends on many factors such as the type of stirring blade used, the size and position in the tank, the amount of the polyester resin charged and its shape, and is determined by a test using an actual processing apparatus. There must be. Further, when the stirring speed in the tank is further increased than NJS, the entrainment of gas from the free surface starts at a certain speed NSA or more. This phenomenon is eliminated or reduced by a commercially available antifoaming agent, but the stirring speed in the tank is preferably in the range of NJS to NSA. When the inside of the tank reaches a “perfectly floating state”, it is preferable that the state be maintained and the heating step be started immediately. If the inside of the tank is heated before reaching the “completely floating state”, the above-mentioned agglomeration may occur.

The heating step in the present invention is a step of heating the inside of the tank to a temperature required for the emulsification step, and a step starting from the time when heating is started after the inside of the tank reaches a completely floating state in the dispersion step. It is. If the organic solvent and the basic compound are present in the tank, the formation of resin fine particles has already started in this step. However, since the rate is not sufficient, it is preferable to heat the inside of the tank to a predetermined temperature in a short time as possible. As a method of heating the inside of the tank,
There is a method in which a jacket is provided on the tank wall, or a spiral coil tube is inserted into the tank, or both are used.In the present invention, either method can be adopted, but the time required for the heating step is reduced, and In order to make the temperature in the tank uniform and to control it with high precision, it is preferable to provide a jacket on the tank wall. In addition, the viscosity of the system may be abnormally increased during this step. In such a case, the problem is solved by charging any of the organic solvent and the basic compound into the tank in the emulsification step. Can be solved.

In the present invention, the emulsification step means that the temperature in the tank is the glass transition temperature of the biodegradable polyester resin or 6%.
This is a step started from a point in time when the temperature reaches the higher one of 0 ° C. By heating the inside of the tank to this temperature, the emulsification (formation of resin fine particles) rate in the system is remarkably accelerated. On the other hand, if the treatment is performed at a temperature lower than the temperature, the above-described case where “the viscosity of the system abnormally increases” occurs, and it becomes impossible to substantially stir the inside of the tank, and the intended purpose is obtained. A water dispersion may not be obtained. However, when the reaction vessel is not a completely closed type reaction vessel, it is necessary to control the temperature in the vessel to a temperature lower than the lower of the boiling point of the amphiphilic organic solvent or 90 ° C. If the temperature is exceeded, evaporation of the amphiphilic organic solvent or water becomes remarkable, which may promote aggregation of the formed resin fine particles. In the case of a pressurized completely closed reaction tank, the temperature can be raised within the limit of pressure resistance.

In the emulsification step, the entrainment of gas from the free surface starts at a stirring speed N'SA higher than the NSA, since the viscosity of the aqueous medium increases somewhat. Therefore, NJS ~ N'SA
It is preferable to carry out stirring within the range described above. If the stirring speed is lower than NJS, the renewal of the surface of the biodegradable polyester resin powder or granular material in which the emulsification is progressing is not sufficient, so that the time required for the emulsification becomes longer and the aqueous dispersion is excellent in storage stability. The composition may not be obtained. On the other hand, if the stirring speed exceeds N'SA, not only foaming occurs and the workability is reduced, but also the contact area between the resin and the aqueous medium is reduced due to the entrainment of gas, and the efficiency of emulsification is reduced. It will take a long time.

The end point of the emulsification step is a point in time when the cooling is started to move to the next cooling step after the amount of coarse particles in the system becomes 1% by mass or less. The amount of the coarse particles is determined by sampling and measuring the aqueous dispersion in the system at regular time intervals. The coarse particles referred to in the present invention are resin particles that do not pass through a 635-mesh, 0.02 mm wire diameter, plain-woven stainless steel filter even under pressure, that is, a particle size of 2.
A particle that can be regarded as 0 μm or more, and refers to a coarse particle solid content remaining on the filter when filtered using the filter. When the mass of the solid content exceeds 1% by mass, the particle size distribution of the resin particles is wide even if the filtration is repeated with a filter having a smaller opening.
Precipitation is caused, and an aqueous dispersion composition having excellent storage stability cannot be obtained. After the amount of the coarse particles in the system becomes 1% by mass or less, it is preferable to shift to the cooling step within one hour. Continuing stirring for a long time not only reduces the effect of further micronization, but also makes the biodegradable polyester resin more susceptible to hydrolysis, lowering the storage stability of the aqueous dispersion composition and the performance of the formed coating film. May be.

In the above emulsification step, when the target resin to be an aqueous dispersion has a relatively high glass transition temperature and is difficult to be plasticized, it is more efficient to carry out the emulsification under pressure using a closed reactor. The resin can be finely divided. The pressure at this time is preferably 0.01 to 5 MPa, and 0.01 to 0.
More preferably, it is 5 MPa. By increasing the pressure, the reaction temperature can be increased to the boiling point of the amphipathic organic solvent or water, so that the plasticization of the resin is promoted. The reaction temperature at that time is preferably higher than the boiling point of the amphiphilic organic solvent and lower than the steam vapor temperature or lower than 120 ° C. Under a pressure exceeding 5 MPa or a temperature exceeding 120 ° C., the biodegradable polyester resin is easily hydrolyzed.

The cooling step is a step for cooling the produced water dispersion to around room temperature, and may be naturally cooled, or may be forcibly cooled by passing a cooling medium through the jacket or the coil tube. At that time, in order to prevent so-called "skinning" in which water on the surface of the formed water dispersion evaporates to form a film having a high solid content, until the water dispersion is cooled to 40 ° C or lower. It is preferable to continue stirring. However, the stirring may be any as long as it achieves the above-mentioned purpose, and the speed is preferably NJS or less. In the cooling step, a substance to be described later can be added and mixed.

When an aqueous dispersion is obtained through the above-described steps of dispersion, heating, emulsification, and cooling, the particles may be further subjected to a jet pulverizing treatment during any step or between steps as necessary to reduce the particle size. (Jet crushing process). Jet pulverization treatment in the present invention, the polyester resin aqueous dispersion obtained through each of the above steps, at a high pressure and high-speed jet from nozzles and pores such as slits,
The resin particles collide with each other or the resin particles against a collision plate or the like, and the resin particles are finely divided by mechanical energy.

The apparatus used in such a jet pulverizing process is as follows: (1) A fluid is jetted from a nozzle under a high pressure of 10 to 200 MPa, and the fluid is made to collide with a collision plate or the like within 1 second to make resin particles fine. Crusher (for example, A.I.
P. V. GAULIN, Homogenizer, Mizuho Industries, Microfluidizer M-110E / H),
(2) A fluid is ejected from a nozzle under a high pressure of 10 to 50 MPa, and a fluid of 0.3 to 500 W at 10 to 100 kHz.
Crusher (for example, TK Micromizer, SONICCORPORATION, Sonorator, manufactured by Tokushu Kika Kogyo Co., Ltd.) that irradiates ultrasonic waves of / cm ² with ultrasonic waves. A pulverizer (for example, Nanomizer PE manufactured by Nanomizer Co., Ltd.) that collides fluids at a high speed of 50 to 300 m / sec to make resin particles finer.
N) and the like.

In the case of jet pulverization using any of the apparatuses, the water dispersion is heated to about room temperature to about 90 ° C. under pressure in order to improve the fluidity of the water dispersion obtained through the preceding steps. It may be heated.

A step of removing the organic solvent out of the system may be provided between the emulsifying step and the cooling step, during the cooling step, or after the cooling step is completed (stripping step). In this case, the stirring is performed under reduced pressure so that the solvent can be distilled off. When performing after the cooling step, it is preferable to heat again.

The resulting aqueous dispersion composition may contain, if necessary, various additives such as a leveling agent, an antifoaming agent, an anti-spitting agent, a viscosity modifier, a pigment dispersant, a lubricant, titanium oxide and zinc oxide,
Pigments and dyes such as carbon black, talc and kaolin,
A filler such as clay or another aqueous resin may be mixed. Further, by adding metal oxide fine particles such as zinc oxide or tin oxide, the aqueous dispersion or the coating film can be provided with an ultraviolet ray cutting ability, an antibacterial ability, or an antistatic ability, respectively.

The aqueous dispersion composition of the present invention can be prepared by a dip coating method, a brush coating method, a roll coating method, a spray coating method, a gravure coating method, a curtain flow coating method, various printing methods, or the like. It can be uniformly applied on various substrates such as paper, glass, metal, etc., and after setting at around room temperature or drying at low temperature, if necessary, heat treatment at high temperature to achieve uniform and glossy A coating film having a high degree and excellent in various performances can be obtained. The high-temperature heat treatment is usually performed at 120 to 250 ° C. for 10 seconds using a hot air circulation type oven or an infrared heater.
Achieved by heating for 30 minutes.

[0043]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Each analysis item was performed according to the following method. (1) Molecular weight of biodegradable polyester resin The molecular weight was determined by GPC analysis (Shimadzu Corporation, solvent: tetrahydrofuran, refractive index spectrometer, converted to polystyrene). (2) Acid value of biodegradable polyester resin 0.1 g of polyester resin is dissolved in 20 ml of methylene chloride, titrated with KOH using phenolphthalein as an indicator, and the acid value of mg of KOH consumed for neutralization is determined. Asked. (3) The glass transition temperature of the biodegradable polyester resin (T
g) Using 10 mg of the resin as a sample, measurement was performed using a differential scanning calorimeter (DSC7, manufactured by PerkinElmer) at a heating rate of 10 ° C./min.

(4) Solid Content Concentration of Aqueous Dispersion Composition An appropriate amount of the prepared aqueous dispersion composition was weighed,
The mixture was heated at a temperature of not less than ° C until the mass of the residue (solid content) reached a constant weight, and the solid content concentration was determined from the mass after the constant weight. (5) Viscosity of aqueous dispersion composition Cone plate type rotational viscometer (manufactured by Rheology, MR-3)
And a shear rate of 10 sec ⁻¹ , 3
The viscosity at 0 ° C. was measured. However, in consideration of the thixotropy of the aqueous dispersion composition, the viscosity at the time of starting rotation and in a steady state was determined. (6) Apparatus for measuring average particle size and particle size distribution of aqueous dispersion composition (MICROTRAC, manufactured by Nikkiso Co., Ltd.)
UPA150) and evaluated by volume average particle size. (7) Storage Stability of Aqueous Dispersion Composition The prepared aqueous dispersion composition was stored at 25 ° C., and changes in the composition were visually observed and evaluated according to the following criteria. ×: A clear change in appearance such as phase separation, precipitation, and solidification was observed within 3 days. Δ: Change in appearance was observed between 3 days and less than 1 week. ○: Change in appearance was observed between one week and less than two weeks. A: No change in appearance was observed for 2 weeks or more.

Resin Synthesis Example 1 Polylactic acid (number average molecular weight 60,000, D-form content 1.7%) 2
88 g was charged in an autoclave, and after degassing and drying, 23 g
The mixture was heated to 0 ° C., 8.4 g of trimellitic acid was added, and the mixture was heated and stirred for 1 hour to carry out a depolymerization reaction, and was discharged in a sheet form. After sufficiently cooling this to room temperature, it was pulverized with a crusher to obtain a biodegradable polyester resin A.

Resin Synthesis Example 2 Resin Synthesis Example 1 was the same as Resin Synthesis Example 1 except that polylactic acid (number average molecular weight: 100,000, D-form content: 9%) and 10.5 g of 1,2,3,4-butanetetracarboxylic acid were used. In the same manner, a depolymerization reaction was performed and pulverized to obtain a resin B.

Resin Synthesis Example 3 A depolymerization reaction was carried out in the same manner as in Resin Synthesis Example 1 except that polylactic acid (number-average molecular weight: 100,000, D-form content: 19%) was obtained. Was.

Resin Synthesis Example 4 Polylactic acid (number average molecular weight 100,000, D-form content 1.7%)
265 g, polycaprolactone (number average molecular weight 80,000) 2
Using 3 g, a depolymerization reaction was carried out in the same manner as in Resin Synthesis Example 1, and pulverized to obtain Resin D.

Table 1 shows the results of the analysis of the resins A to D.

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[Table 1]

Example 1 As a device, a table type homodisper equipped with a 2 L glass container capable of being sealed with a jacket (manufactured by Tokushu Kika Kogyo Co., Ltd.)
TK Robomix) was used. In a glass container, 250 g of biodegradable polyester resin A, 100 parts of acetonitrile
g, polyvinyl alcohol (UF170 made by Unitika)
G) 100 g of a 2% by mass aqueous solution, 550 g of distilled water, and 1. of the total carboxyl group content in the polyester resin.
Triethylamine equivalent to twice equivalent was added, and 6,0
The mixture was stirred at 00 rpm, and no precipitation of resin particles was observed at the bottom of the container, and it was confirmed that the resin particles were completely suspended (dispersion step). Thereafter, the jacket was heated by passing hot water at a predetermined temperature to raise the temperature in the system to 60 ° C. (heating step). When the temperature reaches 60 ° C., the stirring is performed at 7,000 rpm.
m, and the mixture was further stirred for 25 minutes while maintaining the temperature in the system at 70 to 72 ° C. to obtain a milky white uniform aqueous dispersion, and after partially sampling, it was confirmed that the coarse particles had become 1% by mass or less. Stirring was continued for another 10 minutes (emulsification step). Thereafter, the jacket was cooled to room temperature while flowing cold water in the jacket and stirring at 4000 rpm (cooling step). Stainless steel filter (635 mesh, wire diameter 0.02mm plain weave)
The whole amount was filtered using to obtain an aqueous dispersion composition. At the time of filtration, coarse particles having a size of 20 μm or more were 1% by mass or less.

Example 2 An aqueous dispersion composition was obtained in the same manner as in Example 1, except that resin B was used as a biodegradable resin and methyl ethyl ketone was used as an amphiphilic organic solvent. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Example 3 Resin C was used as a biodegradable resin, isopropanol was used as an amphiphilic organic solvent, and carboxymethyl cellulose (number average molecular weight 2
50,000), and the same procedure as in Example 1 was carried out, except that the temperature in the system was set to 60 ° C. in the emulsification step, to obtain an aqueous dispersion composition. Table 2 shows the analysis results of the obtained aqueous dispersion compositions.
Shown in

Example 4 An aqueous dispersion composition was obtained in the same manner as in Example 3, except that 650 g of distilled water was used instead of the aqueous solution of carboxymethyl cellulose using the resin C. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Example 5 Using 350 g of resin D as a biodegradable resin, distilled water
An aqueous dispersion composition was obtained by performing the same operation as in Example 3 except that the amount was changed to 00 g. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Example 6 A completely closed container was used, and the internal pressure of the container was 0.10 MPa.
a. An aqueous dispersion composition was obtained in the same manner as in Example 1, except that the temperature in the emulsification step was changed to 100 ° C. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Example 7 The aqueous dispersion obtained in Example 1 was treated with A.I. P. V. GAULI
N homogenizer 15MR-8TA, 40
The mixture was heated to 70 ° C., subjected to one jet pulverization treatment under the condition of 70 MPa, and cooled to room temperature. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Comparative Example 1 Polylactic acid before depolymerization (number average molecular weight 6
An aqueous dispersion composition was obtained by performing the same operation as in Example 1, except that the content of D-form was 1.7% and the acid value was 1 mgKOH / g). However, in the emulsification step, the coarse particles did not decrease to 1% by mass or less even after the same time as the time required in the same step in Example 1, but the process was shifted to the cooling step and cooled to room temperature. And filtration. At the time of filtration, 39% by mass of coarse particles of 20 μm or more was observed. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Comparative Example 2 An aqueous dispersion composition was obtained in the same manner as in Example 1, except that 700 g of distilled water was used without using the amphiphilic organic solvent. However, in the emulsification step, the coarse particles did not decrease to 1% by mass or less even after the same time as the time required in the same step in Example 1, but the process was shifted to the cooling step and cooled to room temperature. And filtration. 20 at the time of filtration
27% by mass of coarse particles of μm or more were observed. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Comparative Example 3 300 g of resin B was dissolved in 300 g of tetrahydrofuran by heating, and triethylamine equivalent to 1.2 times equivalent of the total amount of carboxyl groups contained in the polyester resin was added. Under stirring at 7,000 rpm, distilled water 600
g of the mixture was added at a rate of 30 g / min to perform phase inversion emulsification. Table 2 shows the analysis results of the obtained aqueous dispersion composition.

Comparative Example 4 The aqueous dispersion obtained in Comparative Example 3 was heated to 80 ° C. with stirring to remove excess organic solvent in the aqueous dispersion. Happens,
A white mass was obtained.

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[Table 2]

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According to the method for producing a biodegradable polyester-based aqueous dispersion of the present invention, the amount of organic solvent used can be greatly reduced, the production process can be simplified, and water having excellent storage stability can be obtained. A dispersion is obtained. The coating film formed from this biodegradable polyester-based aqueous dispersion has excellent water resistance, chemical resistance, weather resistance, and the like, and can be suitably used as a paper coating liquid and various binders.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Daisuke Shirasawa 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory F-term (reference) 4F070 AA47 AC12 AC19 AC36 AC38 AC43 AC46 CA03 CB03 CB12

Claims (5)

[Claims] 1. A total of 100 including the following components (A) to (D):
A method for producing an aqueous dispersion of a biodegradable polyester resin in the form of a mass%, comprising a dispersing step, a heating step, an emulsifying step and a cooling step.
And all or part of components (B) and (C) are coarsely dispersed in an aqueous medium, and in a heating step and an emulsifying step,
Before the end of the emulsification step, the remaining components are added with stirring, and the mixture is heated to 60 ° C. or the higher of the glass transition temperatures of the component (A), and the biodegradable particles having a particle size of 20 μm or more are heated. A method for producing an aqueous dispersion of a biodegradable polyester resin, wherein stirring is continued until the polyester resin coarse particles become 1% by mass or less. (A) The lactic acid unit contains 50 mol% or more, the D-form content in the lactic acid unit is 0.1 to 25 mol%, and the acid value is 5 to 50 KO.
Hmg / g biodegradable polyester resin 10-60
(B) a basic compound, (C) 0.1 to 30% by mass of an amphiphilic organic solvent having a plasticizing ability with respect to a biodegradable polyester resin, and (D) water. 2. The method according to claim 1, wherein the basic compound is ammonia or a compound having a boiling point of 25.
The method for producing an aqueous dispersion of a biodegradable polyester resin according to claim 1, which is an organic amine compound having a temperature of 0 ° C or lower. 3. The swelling degree (mass ratio before and after immersion) of the organic solvent after stirring for 1 hour at 60 ° C. in a solvent whose mass ratio is 10 times that of the biodegradable polyester resin is 1. The method for producing an aqueous dispersion of a biodegradable polyester resin according to claim 1 or 2, wherein the solubility under the same conditions is 02 g or more or 0.01 g / g or more. 4. The biodegradable polyester resin contains at least 90 mol% of a lactic acid unit, and the D-form content in the lactic acid unit is 1 to 4.
4. The composition according to claim 1, wherein the content is 20 mol%.
A method for producing the aqueous dispersion of a biodegradable polyester resin according to the above. 5. The process for producing an aqueous dispersion of a biodegradable polyester resin according to claim 1, wherein the emulsification step is carried out under a pressurized condition using a closed stirrer. [0001]