JP2009013400A - Method for producing polymer solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polymer solution by which the water content of a wet polymer powder can be reduced by removing water from the powder within a short time and without subjecting a drying step using a drier. <P>SOLUTION: The method for producing the polymer solution comprises mixing a water-containing wet polymer powder with a solvent of a boiling point of 100°C or higher and heating the mixture to boil the water contained in the wet powder to distill it off. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a polymer solution.

  Polymers obtained by suspension polymerization or polymers recovered from emulsions obtained by emulsion polymerization are substantially free from organic solvents and solvents such as water, so they can be easily transported and stored in small volumes. It can be carried out, has a high degree of freedom in solvent selection, and can easily control the molecular weight. Such polymers are used in a wide range of fields as resins such as paints, inks, adhesives, plastic molding materials, and fired pastes. In addition, a polymer is normally dissolved in various solvents and used as a polymer solution.

In general, suspension polymerization proceeds in a state where monomer oil droplets are dispersed in water as a dispersion medium. Therefore, in order to obtain a polymer solution, the slurry (aqueous suspension) after the completion of the polymerization reaction is washed with pure water, then a polymer powder is formed in the dehydration step, and water is further added in the drying step. In many cases, the powder is completely removed to obtain a dry powder, and the dry powder is dissolved in a target solvent.
On the other hand, in emulsion polymerization, water is used as a medium, an emulsifier or a surfactant is dissolved therein, a monomer that is insoluble or poorly soluble in water is added thereto, and polymerization is performed using a water-soluble initiator. It is a method to perform and is generally obtained as an emulsion in which polymer particles are dispersed in water. For this reason, in order to obtain a polymer solution, the process of collect | recovering polymer particles from the obtained emulsion first is needed. As a method used in this recovery step, a known method such as a spray drying method (spray drying method) or a coagulation method can be used. In the case of the spray drying method, a polymer solution is often obtained by dissolving the recovered dry powder in a target solvent. In the case of the coagulation method, water is contained in the collected polymer (polymer wet powder), so after drying the polymer wet powder to make a dry powder, the dry powder is dissolved in the target solvent. In many cases, a polymer solution is obtained.

By the way, particularly in the field of fired paste, when water reacts with a filler such as metal or glass, the performance of the paste is likely to deteriorate. Therefore, the polymer or polymer solution used as the resin for the fired paste contains water. A reduction in rate is required.
In recent years, in consideration of the RoHS Directive, home appliances and electronic parts such as televisions have poor water resistance, such as phosphate glass and multi-alkali / borate glass instead of lead glass used in the past. The movement to replace with materials is spreading. Also from such a movement, the polymer used as resin, such as a baking paste, and a polymer solution are calculated | required by the further water content reduction.

In order to reduce the water content of the polymer solution, as described above, the polymer wet powder obtained in the dehydration process or the recovery process may be sufficiently dried to produce a polymer having a reduced water content. Examples of the method for drying the polymer wet powder include a method of drying by heating under reduced pressure, a method of heating under reduced pressure and rotating in the vertical direction, and particulate polymerization using heated air. There is known a method of drying a product while flowing it.
However, the method of heating and drying under reduced pressure has a problem that it takes a long time to obtain a sufficient drying effect. Moreover, in the method using warm air, it is difficult to dry and remove the water present inside the particulate polymer.

Therefore, as a dryer suitable for the production of bead polymer, a two-stage fluidized bed dryer with a primary drying chamber and a secondary drying chamber arranged above and below is used to efficiently and stably produce a bead polymer. A method has been proposed (for example, see Patent Document 1).
In addition, a drying apparatus (for example, see Patent Document 2) suitable for drying a polymer wet powder recovered from an emulsion by a coagulation method and a drying method (for example, see Patent Document 3) have been proposed.
JP 2003-313229 A JP 2003-262466 A JP 2003-261686 A

However, even if the drying methods as described in Patent Documents 1 to 3 are used, the drying efficiency may be reduced depending on the characteristics of the dryer such as the size and capacity of the dryer. In particular, when drying a polymer wet powder having a glass transition temperature (Tg) of 23 ° C. or lower, it is necessary to take a long time to obtain a sufficient drying effect because it is necessary to dry under reduced pressure at a low temperature. It was necessary to pay attention to handling because the dry powder to be solidified easily.
Also, if a dryer is used to dry the polymer wet powder, or if a spray drying method is used to recover the polymer particles from the emulsion, contamination may occur even if it is slight. In particular, in the field of electronic materials where high purity is required, it may be fatal.

  The present invention has been made in view of the above circumstances, and removes water contained in a polymer wet powder in a short time and without going through a drying process using a dryer, thereby reducing the water content. It aims at realization of the manufacturing method of a united solution.

As a result of intensive studies, the present inventors have found that water contained in the polymer powder can be efficiently removed by mixing and heating the polymer powder before drying and a solvent having a boiling point of 100 ° C. or higher. The present invention has been completed.
That is, in the method for producing a polymer solution of the present invention, a polymer powder containing water and a solvent having a boiling point of 100 ° C. or higher are mixed and heated, and the water is boiled and contained in the polymer powder. It is characterized by distilling off water.
Here, the polymer wet powder is obtained by suspension polymerization or recovered from an emulsion by a coagulation method.
Moreover, it is preferable to heat in the state which mixed the polymer powder and the solvent whose boiling point is 100 degreeC or more with the solvent whose boiling point is less than 100 degreeC.

According to the production method of the present invention, it is possible to obtain a polymer solution that can reduce the water content by removing water contained in the polymer wet powder in a short time and without going through a drying step using a dryer. .
Moreover, according to this invention, since it does not go through a drying process, the contamination by a dryer can be suppressed.
Furthermore, this invention is suitable also when using a polymer wet powder whose glass transition temperature (Tg) is 23 degrees C or less.

The present invention will be described in detail below.
[Polymer wet powder]
The polymer wet powder used in the present invention is obtained, for example, by suspension polymerization or recovery from an emulsion by a coagulation method, and contains water.
When the polymer wet powder is obtained by suspension polymerization, the suspension polymerization method is not particularly limited. For example, the monomer constituting the polymer in water, a dispersant, an oil-soluble polymerization initiator, necessary According to the method, a chain transfer agent or the like is added to form an aqueous suspension, and while stirring this, the monomer is dispersed in droplets of about 0.05 to 1 mm, and the polymerization proceeds under heating.

Although it does not restrict | limit especially as a monomer which comprises a polymer, For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate Alkyl (meth) acrylates such as 2-ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate; N-phenylmaleimide, N-cyclohexylmaleimide, N- Maleimide derivatives such as butyl maleimide; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl methacrylate), 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxy Vinyl polymerizable monomers having a hydroxyalkyl group such as hexyl (meth) acrylate; (meth) acrylic acid, 2- (meth) acryloxyethyl hexahydrophthalic acid, 2- (meth) acryloxypropyl hexahydrophthalic acid, 2 -(Meth) acryloxyethyltetrahydrophthalic acid, 2- (meth) acryloxypropyltetrahydrophthalic acid, 5-methyl-2- (meth) acryloxyethylhexahydrophthalic acid, 2- (meth) acryloxyethylphthalic acid 2- (meth) acryloxypropylphthalic acid, 2- (meth) acryloxyethyl oxalic acid, 2- (meth) acryloxypropyl oxalic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, sorbic acid, etc. Carboxyl group-containing vinyl monomers; acrolein, diacetone Rilamide, formylstyrene, vinyl alkyl ketone, (meth) acrylamide pivalin aldehyde, diacetone (meth) acrylate, acetonyl acrylate, 2-hydroxypropyl acrylate acetyl acetate, acetoacetoxyethyl (meth) acrylate, butanediol-1,4-acrylate -Vinyl monomers having aldehyde groups or carbonyl groups such as acetyl acetate and acrylamide methyl anisaldehyde; vinyl monomers containing amide groups such as (meth) acrylamide, crotonamide and N-methylolacrylamide; allyl glycidyl ether, glycidyl (meth) acrylate Epoxy group-containing vinyl monomers such as styrene, α-methylstyrene and other aromatic vinyl monomers; acrylonitrile Olefinic monomers such as butadiene; nitrile group-containing vinyl monomers include vinyl halide monomers such as vinyl chloride and the like. These may be used alone or in combination of two or more.
In the present invention, “(meth) acryl” represents a general term for acrylic and methacrylic.

  In the present invention, the effects of the invention are remarkably exhibited in a composition having a glass transition temperature (Tg) of 23 ° C. or lower. Examples of compositions with a Tg of 23 ° C. or lower include methyl acrylate, ethyl acrylate, n-butyl (meth) acrylate, i-butyl acrylate, 2-ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, and n-stearyl. Examples include homopolymers such as (meth) acrylates, copolymers with other monomers, and the like.

Examples of the dispersant include poly (meth) acrylic acid metal salts, or alkali metal salts of copolymers of (meth) acrylic acid and methyl (meth) acrylate; polyvinyl alcohol having a saponification degree of 70 to 100%, methylcellulose, and the like Is mentioned. These may be used alone or in combination of two or more. Among these, polyvinyl alcohol is preferable.
0.001-10 mass% is preferable in 100 mass of aqueous suspensions, and, as for the compounding quantity of a dispersing agent, 0.01-1 mass% is more preferable. When the blending amount of the dispersant is 0.001% by mass or more, the dispersibility during polymerization tends to be good. On the other hand, when the blending amount of the dispersant is 10% by mass or less, the dehydrating property and drying property of the obtained polymer wet powder tend to be good.

As a method for suspension polymerization, the above-mentioned dispersant is dissolved alone or in a mixture of two or more in water, a monomer, an oil-soluble polymerization initiator, and a chain transfer agent are added as necessary. It is preferable to carry out the polymerization under heating by dispersing in droplets of about 1 mm.
The polymerization temperature is not particularly limited, but is preferably 50 to 100 ° C. from the viewpoint of ensuring dispersion stability and reaction time.

Examples of the oil-soluble polymerization initiator used during suspension polymerization include oil-soluble azo initiators such as azobisisobutyronitrile and organic peroxide initiators such as benzoyl peroxide.
Although the usage-amount of an oil-soluble polymerization initiator is not restrict | limited in particular, It is preferable to exist in the range of 0.05-10 mass parts with respect to 100 mass parts of monomers which comprise a polymer. If the usage-amount of an oil-soluble polymerization initiator is 0.05 mass part or more, superposition | polymerization will advance in a comparatively short time, and it exists in the tendency for productivity to improve. Moreover, if the usage-amount of an oil-soluble polymerization initiator is 10 mass parts or less, superposition | polymerization heat_generation | fever is relieved and it exists in the tendency for control of polymerization temperature to become easy. The lower limit of the amount of the oil-soluble polymerization initiator used is particularly preferably 0.1 parts by mass or more, and the upper limit is particularly preferably 5 parts by mass or less.

Examples of the chain transfer agent used at the time of suspension polymerization include mercaptans such as n-dodecyl mercaptan, thioglycolic acid esters such as octyl thioglycolate, and α-methylstyrene dimer.
Although the usage-amount of a chain transfer agent is not restrict | limited in particular, It is preferable to exist in the range of 0.05-10 mass parts with respect to 100 mass parts of monomers which comprise a polymer. If the amount of the chain transfer agent used is 0.05 parts by mass or more, the molecular weight of the polymer tends to decrease and the solvent solubility tends to improve, and it is particularly preferably 0.1 parts by mass or more. Further, the upper limit is particularly preferably 5 parts by mass or less from the viewpoint of the molecular weight reduction efficiency.

  Further, for the purpose of improving the dispersion stability during suspension polymerization, an electrolyte such as sodium carbonate, sodium sulfate, or sodium bicarbonate may be used. The amount used is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of water.

The polymer thus obtained is usually spherical and has a particle size distribution of about 10 to 1000 μm. Further, the specific gravity varies depending on its constituent components, but is usually a value larger than 1.
The polymer is obtained in a state dispersed in water after polymerization (aqueous suspension) and may be used as it is, but contains impurities such as a chain transfer agent used in the polymerization. It is preferable to filter and wash the aqueous suspension after polymerization.
In addition, since the time required for azeotropic distillation described later depends on the amount of water contained in the polymer, the polymer is dehydrated with a dehydrator or the like to obtain a polymer powder. In the case of a polymer having a Tg of 23 ° C. or lower, if water is excessively removed by dehydration, particles may be fused while being taken out from the dehydrator or during storage. Therefore, when dehydrating, although depending on the outside air temperature and the Tg of the polymer, it is desirable to dehydrate so that the water content is about 4 to 10%. In the case of a polymer having a Tg of 23 ° C. or higher, although it depends on the capacity of the dehydrator, it is preferable to dehydrate to a water content of about 2% to 6%.

When the polymer wet powder is recovered from the emulsion by a coagulation method, the method is not particularly limited, and examples thereof include a method of adding an aggregating agent to an emulsion obtained by an emulsion polymerization method and aggregating and precipitating. At this time, impurities such as an emulsifier used for the polymerization can be washed by washing the obtained polymer wet powder with pure water or the like.
As a method of emulsion polymerization, a known method can be used. For example, a method of adding a monomer constituting a polymer, a polymerization initiator, an emulsifier and the like to water and allowing the polymerization to proceed under heating can be mentioned.

As the monomer constituting the polymer, one or more types can be selected and used from the monomers constituting the polymer exemplified above in the description of the suspension polymerization.
In the present invention, the effect of the invention is remarkably exhibited in a composition having a glass transition temperature (Tg) of 23 ° C. or lower. As the composition having a Tg of 23 ° C. or lower, one or more kinds selected from the compositions having the Tg of 23 ° C. or lower exemplified above in the description of the suspension polymerization can be used.

Although it does not specifically limit as a polymerization initiator used at the time of emulsion polymerization, For example, benzoyl peroxide, cumene hydroperoxide, peroxides, such as hydrogen peroxide; azo compounds, such as azobisisobutyronitrile; ammonium persulfate, A persulfate compound such as potassium persulfate; a redox initiator composed of a perchloric acid compound, a perborate compound or a combination of a peroxide and a reducing sulfoxy compound is used.
Examples of chain transfer agents include mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl mercaptan, n-tetradecyl mercaptan, and n-hexyl mercaptan.
Although the usage-amount of a polymerization initiator is not restrict | limited in particular, It is preferable to exist in the range of 0.01-5 mass parts with respect to 100 mass parts of monomers which comprise a polymer.

Known emulsifiers can be used for the emulsion polymerization. Specific examples include anionic emulsifiers (sodium dodecylbenzenesulfonate, sodium laurylsulfonate, sodium laurylsulfate, etc.), anions containing polyoxyethylene groups. And emulsifying emulsifiers, nonionic emulsifiers (polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, etc.), and reactive emulsifiers having a vinyl polymerizable double bond in the molecule.
Although the usage-amount of an emulsifier is not restrict | limited in particular, It is preferable to exist in the range of 0.1-10 mass parts with respect to 100 mass parts of monomers which comprise a polymer. If the usage-amount of an emulsifier is 0.1 mass part or more, it exists in the tendency for superposition | polymerization stability to become favorable. Moreover, if the usage-amount of an emulsifier is 10 mass parts or less, it exists in the tendency for the ion content of the polymer obtained to decrease. The lower limit of the amount of the polymerization initiator used is particularly preferably 0.2 parts by mass or more, and the upper limit is particularly preferably 5 parts by mass or less.

  Examples of the flocculant added to the emulsion obtained by the emulsion polymerization method include an aqueous sulfuric acid solution, an aqueous calcium acetate solution, an aqueous magnesium sulfate solution, and an aqueous aluminum sulfate solution.

[Polymer solution]
The polymer solution is obtained by mixing and heating the above-described polymer wet powder and a solvent having a boiling point of 100 ° C. or more at 1 atm, boiling water and distilling it off.
The addition amount of the solvent is preferably 50 to 900 parts by mass with respect to 100 parts by mass of the polymer wet powder. If the addition amount of the solvent is 50 parts by mass or more, the viscosity of the polymer solution tends to be moderately low, and water tends to be easily distilled off. If the addition amount of the solvent is 900 parts by mass or less, a polymer solution having an appropriate concentration can be easily obtained without impairing the efficiency of water distillation.

<Solvent>
The solvent used in the present invention has a boiling point of 100 ° C. or higher. By using a solvent having a boiling point of 100 ° C. or higher, water can be boiled without boiling the solvent, and a function as a heating medium can be obtained until the water is completely distilled off. It becomes easy to transmit and water can be distilled off efficiently. Specific examples of such solvents include α, β, γ-terpineol, propylene glycol monomethyl ether, ethyl-3-ethoxypropionate, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene. Glycol monobutyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, isophorone, 3-methoxybutyl acetate, benzyl alcohol 1-octanol, 1-nonaol, 2-ethyl-1-hexanol, 1-decanol, 1-c Decanol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol , Toluene, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and the like, but not limited thereto. These may be used alone or in combination of two or more. In particular, those having a boiling point of 120 to 250 ° C. are preferred from the viewpoint of being less likely to evaporate during dehydration and more easily exhibiting the function of the heat medium, among which α, β, γ-terpineol, and propylene glycol monomethyl ether are preferred.

Moreover, in this invention, it is preferable to heat in the state which further mixed the solvent with the boiling point in less than 100 degreeC in 1 atmosphere into the said polymer powder and the solvent whose boiling point is 100 degreeC or more.
Examples of the solvent having a boiling point of less than 100 ° C. include solvents that azeotrope with water, and the specific gravity is higher than that of water from the viewpoint that water can be removed more efficiently and the determination of completion of dehydration becomes easier. It is preferable to use a small solvent that is immiscible with water. Specifically, n-hexane, 3-methylpentane, 2-methylpentane, 2,3-dimethylbutane, 2,2-dimethylbutane, n-heptane, 2-methylhexane, 3-methylhexane, 3-ethyl Examples include aliphatic hydrocarbons such as pentane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, and 2,2,3-trimethylbutane. These may be used alone or in combination of two or more. Of these, n-hexane and n-heptane are preferable.

  When a solvent having a boiling point of less than 100 ° C. is further mixed, the amount used is set so as to reflux in the decanter and the production kettle described later. Specifically, 1 to 300 parts by mass is preferable with respect to 100 parts by mass of the solvent having a boiling point of 100 ° C. or more, and 10 to 100 parts by mass is more preferable. When the amount used is less than 1 part by mass, it tends to be difficult to reflux the decanter and the production kettle. When the amount used exceeds 300 parts by mass, the solubility of the polymer tends to deteriorate.

A solvent having a boiling point of less than 100 ° C is further mixed, that is, by using two or more solvents having different boiling points such as a solvent having a boiling point of 100 ° C or more and a solvent having a boiling point of less than 100 ° C, the boiling point is 100 ° C. Less than the solvent and the water in the polymer wet powder azeotrope, and the efficiency of distilling out the water is improved.
When two or more solvents having different boiling points are used, the solvent having a boiling point of less than 100 ° C. is preferably a solvent having a boiling point of 20 ° C. or lower than that having a boiling point of 100 ° C. or higher. Thus, by having a boiling point difference of 20 ° C. or higher, volatilization of a solvent having a high boiling point (high boiling point solvent) among the solvents used tends to be suppressed, and the adjustment of the polymer solution tends to be easy.

In the present invention, when two or more solvents having a boiling point of less than 100 ° C. are used, the solvent having the lowest boiling point (hereinafter referred to as “low boiling solvent”) and water azeotrope. . Since the low boiling point solvent is refluxed between the production tank 11 and the decanter 12 provided in the polymer solution production apparatus 10 as shown in FIG. 1, the amount of the low boiling point solvent used is more than twice the capacity of the decanter 12. It is desirable. The amount of the low boiling point solvent used is preferably 20 parts by mass to 300 parts by mass with respect to 100 parts by mass of the solvent other than the low boiling point solvent.
In the present invention, when a solvent having a boiling point of less than 100 ° C. is used alone, the solvent is referred to as a “low boiling point solvent”.

<Manufacturing method>
In the present invention, for example, a polymer solution is produced using a production apparatus 10 as shown in FIG.
Here, an example of the method for producing the polymer solution of the present invention will be specifically described with reference to FIG. In addition, the example shown below is a case where the solvent whose boiling point is 100 degreeC or more and the solvent whose boiling point is less than 100 degreeC are used as a solvent.

First, the polymer powder obtained as described above is put into the production kettle 11 together with a solvent having a boiling point of 100 ° C. or higher and a solvent having a boiling point of less than 100 ° C., and heated while stirring with the stirring blade 13. The order of charging into the production kettle 11 may be as follows. First, the solvent having a boiling point of 100 ° C. or more may be charged, and then the polymer dust powder may be charged, or vice versa, or the solvent and the polymer dust powder may be charged simultaneously. However, it is preferable that a solvent having a boiling point of 100 ° C. or higher is first added and then a polymer wet powder is added in order to improve the dispersibility of the polymer wet powder. By heating, the water contained in the polymer wet powder and the low boiling point solvent azeotrope into vapor and move to the condenser 14. The steam is cooled by the condenser 14 and condensed in the decanter 12 into water and a low boiling point solvent. The condensed water and the low boiling point solvent are not mixed, and are separated into an upper layer (low boiling point solvent) and a lower layer (water) in the decanter 12. Only the low boiling point solvent whose liquid level reaches the return line 12a provided in the middle stage of the decanter 12 is returned to the production kettle 11 and again azeotroped with water contained in the polymer wet powder.
Thus, the water contained in the polymer wet powder is removed by continuing the reflux.

  The heating temperature is preferably higher than the azeotropic point of the low-boiling point solvent and water and lower than the boiling point of solvents other than the low-boiling point solvent. In addition, it is desirable that the low boiling point solvent is azeotroped with water and sufficiently refluxed in the production vessel 11.

Completion of the azeotropic distillation can be determined by the fact that the liquid (distilled liquid) is not separated in the decanter 12. The water accumulated in the decanter 12 may be discharged from the discharge line 12b provided at the lower part of the decanter 12 during the azeotropic distillation or after the azeotropic distillation is completed. On the other hand, the low boiling point solvent accumulated in the decanter 12 may be discharged from the discharge line 12b together with water after the azeotropic distillation is completed.
By performing azeotropic distillation in this way, water contained in the polymer wet powder can be removed in a shorter time than drying using a dryer. The azeotropic distillation time is preferably 0.1 to 10 hours.

A polymer solution which has been subjected to azeotropic distillation may be used as it is, but it is preferable to further heat to distill off the low boiling point solvent. At this time, the low boiling point solvent can be efficiently distilled off by flowing nitrogen into the production kettle 11 or reducing the pressure. In addition, when three or more solvents are used in the azeotropic distillation, two or more kinds of mixed solvents are distilled off at the same time, or after the low boiling point solvent is distilled off, other solvents are used as necessary. Can be distilled off.
A solvent may be added to the polymer solution thus obtained so as to obtain a desired solid content, if necessary. The solvent to be added may be the same solvent as the solvent used in the azeotropic distillation (excluding the distilled solvent (such as low boiling point solvent)) or a different solvent. Similar solvents are preferred.

  The polymer solution thus obtained is suitable as a resin for paints, inks, adhesives, plastic molding materials, fired pastes and the like.

As described above, according to the present invention, a polymer solution having a reduced water content can be obtained in a short time.
Moreover, since it does not go through the drying process using a dryer, the contamination by a dryer can be suppressed and a polymer solution with high purity can be obtained. Furthermore, the water content can be further reduced as compared with a polymer solution produced by dissolving a dry powder obtained through a drying step in a solvent.
Furthermore, even if it is a polymer wet powder whose Tg is 23 degrees C or less, a polymer solution is obtained in a short time, without reducing production efficiency.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In the following description, “part” represents “part by mass” and “%” represents “% by mass”.

<Various evaluations>
(Measurement of moisture content of polymer wet powder and dry powder)
The polymer wet powder and the dry powder were heated at 105 ° C. for 2 hours, and the volatile content was simply set to the moisture content (water content).

(Measurement of water content of polymer solution)
The polymer solution was measured for moisture content (water content) with a Karl Fischer moisture meter according to a volumetric method.

(Measurement of glass transition temperature (Tg))
As the glass transition temperature, a value calculated by the following Fox formula was used.
1 / Tg = w1 / Tg1 + w2 / Tg2 ...
In the formulas, Tg1, Tg2,... Represent Tg [K], w1, w2,. As the Tg of each component, the value described in “Polymer Handbook 3rd Edition” (A WILEY-INTERSCIENCE PUBLICATION, 1989) can be used.

<Example 1>
(Manufacture of polymer wet powder)
In a polymerization apparatus capable of heating and cooling, 190 parts of deionized water and 100 parts of n-butyl methacrylate (n-BMA) are added, 0.3 part of azobisisobutyronitrile as an oil-soluble polymerization initiator, and as an electrolyte. 0.5 part of sodium sulfate and 0.14 part of octyl thioglycolate as a chain transfer agent were added and sufficiently stirred to dissolve. Then, once the stirring was stopped, a dispersant solution in which 0.3 part of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) was dissolved in 10 parts of deionized water was added as a dispersant, and stirring was resumed. The temperature was raised. The reaction was carried out for 2 hours while maintaining the reaction temperature of 75 to 80 ° C., and after confirming the maximum value of the polymerization exotherm, the temperature was raised to 85 ° C. and held for 2 hours to complete the reaction.
The obtained aqueous suspension was filtered through a nylon filter cloth having an opening of 45 μm, thoroughly washed with deionized water, dehydrated with a dehydrator, and polymer of poly-n-butyl methacrylate (Tg = 20 ° C.). Damp powder was obtained. The water content of the obtained polymer wet powder was 6.1%.

(Production of polymer solution)
A polymer solution was produced using a production apparatus capable of heating and cooling as shown in FIG.
In the production vessel 11, 63 parts of propylene glycol monomethyl ether (PGM) (boiling point 120 ° C.) and 37 parts of n-hexane (boiling point 69 ° C., specific gravity 0.66) were put, and the polymer wetness previously obtained was stirred. 100 parts of the powder was added to dissolve the polymer wet powder. The temperature was raised to 65 ° C., and n-hexane was refluxed between the production kettle 11 and the decanter 12. In order to maintain a sufficiently refluxed state, the temperature was gradually raised to 80 ° C. over 4 hours, and water contained in the polymer wet powder was removed by azeotropic distillation. Since the separation of the liquid (distillate) in the decanter 12 no longer occurred, the completion of the azeotropic distillation was judged, and the water and n-hexane accumulated in the decanter 12 were discharged from the discharge line 12b.
The distillate was further raised to 100 ° C. over 1 hour, held for another 2 hours while slowly reducing the pressure to −33 kPa with a vacuum pump, and the water, n-hexane and PGM remaining in the polymer wet powder were discharged first. The total was distilled off until the total reached 60 parts.
Heating and decompression were completed, and 98 parts of PGM was added to obtain a polymer solution having a solid content of 40%. Table 1 shows the water content of the polymer solution.

<Examples 2 and 3>
In the same manner as in Example 1, a polymer wet powder of poly-n-butyl methacrylate (Tg = 20 ° C.) was produced. Table 1 shows the water content of the polymer wet powder.
Then, using the polymer powder obtained in each example, the type and amount of the solvent used for azeotropic distillation, the distillate and the total amount of water and solvent to be distilled, and the polymer solution A polymer solution was produced in the same manner as in Example 1 except that the type and amount of the solvent added to were changed to the values shown in Table 1. Table 1 shows the water content of the polymer solution.

  As is clear from Table 1, the polymer solutions obtained in Examples 1 to 3 can be produced in a short time (7 hours) without going through the drying step of the polymer wet powder, and all have a water content of 0. It was reduced to 1% or less. Moreover, since no dryer is used, it is considered that contamination (contamination) such as impurities could be suppressed.

<Comparative Example 1>
(Manufacture of polymer wet powder)
A polymer wet powder was produced in the same manner as in Example 1. The water content of the obtained polymer wet powder was 6.1%.

(Polymer wet powder drying process)
The obtained polymer wet powder was dried with a conical blender under a reduced pressure of 2.4 kPa at 20 ° C. for 24 hours to obtain a dry powder of a polymer having a nonvolatile content of 99.0%. In this case, the water content was determined to be 1.0%.

(Production of polymer solution)
A condenser is attached to a production apparatus capable of raising the temperature and cooling, 150 parts of PGM is added, 100 parts of the dry powder obtained above is added with stirring, and heated at 60 ° C. for 4 hours to dissolve the dry powder. A solution was prepared. Table 2 shows the water content of the polymer solution.

<Comparative Examples 2 and 3>
The polymer wet powder was dried in the same manner as in Comparative Example 1 except that the drying time of the polymer wet powder was changed to the values shown in Table 2. In Comparative Example 2, a polymer dry powder having a nonvolatile content of 99.7% was obtained, and in Comparative Example 3, a polymer dry powder having a nonvolatile content of 98.5% was obtained. Table 2 shows the moisture content of each of the obtained dry powders.
Next, a polymer solution was produced in the same manner as in Comparative Example 1 except that the type of solvent used for dissolving the dry powder was changed to that shown in Table 2. Table 2 shows the water content of the polymer solution.

As is clear from Table 2, the water content of the polymer solutions obtained in Comparative Examples 1 and 3 was 0.1% or more. On the other hand, although the polymer solution obtained in Comparative Example 2 was able to reduce the water content to 0.1% or less, it took a long time (42 hours) for the drying process.
In any of the comparative examples, much time was spent in comparison with the examples in order to obtain the polymer solution.

<Example 4>
(Manufacture of emulsion containing acrylic polymer particles)
In a polymerization apparatus capable of heating and cooling, 100 parts of water and 0.05 part of potassium persulfate as a polymerization initiator are added, 2.5 parts of methyl methacrylate and 2.5 parts of isobutyl methacrylate are added as a reaction solution, and nitrogen is added. While stirring at 150 rpm in the atmosphere, heat polymerization was performed at 80 ° C. for 0.5 hours to form core particles. To this reaction solution, 25 parts of deionized water, 1 part of dipotassium alkenyl succinate (manufactured by Kao Corporation, “Latemul ASK”) as an emulsifier, 45 parts of the mixture A shown in Table 3 were added dropwise over 2 hours, and then 80 ° C. For 0.5 hour. Subsequently, 25 parts of deionized water, 1 part of dipotassium alkenyl succinate (manufactured by Kao Corporation, “Latemul ASK”) as an emulsifier, 50 parts of the mixture B shown in Table 3 were added dropwise to the reaction solution over 1 hour, and then 80 parts. The emulsion polymerization was terminated by maintaining at 1 ° C. for 1 hour.
The obtained reaction solution was filtered through a nylon filter cloth having an opening of 45 μm to obtain an emulsion containing acrylic polymer particles having a heating residue of 39.7% as shown in Table 3.

(Recovery of polymer wet powder)
To the obtained emulsion containing acrylic polymer particles, 300 parts of a 3% sulfuric acid aqueous solution as a flocculant was added to agglomerate the polymer, and solidified by heat treatment at 90 ° C. to obtain a polymer slurry.
The obtained polymer slurry was filtered through a nylon filter cloth having an opening of 45 μm, sufficiently washed with deionized water and then dehydrated with a dehydrator to obtain a polymer wet powder. The water content of the obtained polymer wet powder was 36.6%.

(Production of polymer solution)
A polymer solution was produced from the obtained polymer wet powder using a production apparatus capable of heating and cooling as shown in FIG.
570 parts of terpineol (manufactured by Nippon Fragrance Chemical Co., Ltd., boiling point: 219 ° C.) and 188 parts of n-hexane (boiling point: 69 ° C., specific gravity: 0.66) are placed in the production pot 11 and the acrylic polymer particles are contained while stirring 100 parts of the polymer powder collected from the emulsion was added to dissolve the polymer powder.
The temperature was raised to 65 ° C., and n-hexane was refluxed between the production kettle 11 and the decanter 12. In order to maintain a sufficiently refluxed state, the temperature was gradually raised to 80 ° C. over 4 hours, and water contained in the polymer wet powder was removed by azeotropic distillation. Since the separation of the liquid (distillate) in the decanter 12 no longer occurred, the completion of the azeotropic distillation was judged, and the water and n-hexane accumulated in the decanter 12 were discharged from the discharge line 12b. The temperature is further raised to 120 ° C. over 1 hour, and water, n-hexane, and terpineol remaining in the polymer wet powder are distilled while flowing nitrogen until the total of the distillate discharged previously becomes 230 parts. Left.
Heating was terminated, and a polymer solution having a solid content of 10% as shown in Table 4 was obtained. Table 5 shows the water content of the polymer solution.

<Comparative example 4>
The emulsion containing the acrylic polymer particles obtained in Example 4 was spray-dried to obtain a dry powder. 10 parts of the obtained dry powder is added to 90 parts of terpineol (manufactured by Nippon Fragrance Chemicals Co., Ltd., boiling point 219 ° C.), and the dry powder is dissolved over 4 hours at 60 ° C. to produce a polymer solution having a solid content of 10%. did. Table 5 shows the water content of the polymer solution.

As is clear from Table 5, the polymer solution obtained in Example 4 could be produced in a short time (8 hours) without going through the drying step of the polymer wet powder. Furthermore, the polymer solution obtained in Example 4 was able to produce a polymer solution having a lower water content than the polymer solution obtained in Comparative Example 4. Moreover, since no dryer is used, it is considered that contamination (contamination) such as impurities could be suppressed.
On the other hand, the polymer solution obtained in Comparative Example 4 had a higher water content than Example 4. Therefore, it is necessary to spend a long time in the drying process when scaling up. Moreover, the drying process which may mix an impurity was required.

  As is clear from the above results, the present invention is a production method for obtaining a pure polymer solution efficiently and without contamination from a polymer powder containing water without going through a drying step. It is very useful industrially.

It is the schematic which shows an example of the manufacturing apparatus of a polymer solution.

Explanation of symbols

10: Manufacturing apparatus 11: Manufacturing pot 12: Decanter 12a: Return line 12b: Discharge line 13: Stirring blade 14: Condenser

Claims (4)

  A method for producing a polymer solution, comprising mixing and heating a polymer powder containing water and a solvent having a boiling point of 100 ° C. or more, boiling the water, and distilling off the water contained in the polymer powder.   The method for producing a polymer solution according to claim 1, wherein the polymer wet powder is obtained by suspension polymerization.   The method for producing a polymer solution according to claim 1, wherein the polymer wet powder is recovered from the emulsion by a coagulation method.   The method for producing a polymer solution according to any one of claims 1 to 3, wherein heating is performed in a state where a solvent having a boiling point of less than 100 ° C is further mixed with the polymer powder and a solvent having a boiling point of 100 ° C or higher.

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