JP7285664B2 - Polymer production method - Google Patents

Description

The present invention relates to a method for producing polymers.

Polymers are often made by polymerizing monomers in a solvent. In order to remove the solvent from the polymer-containing solution after production and recover a polymer with a low residual solvent amount, the solvent is usually evaporated by placing the polymer-containing solution under heating and reduced pressure. A method of removing is used.

However, polymers often have high viscosity, and in order to sufficiently reduce the amount of residual solvent, it is necessary to lengthen the time required for volatilization, raise the temperature during volatilization, or lower the pressure, resulting in production problems. There were problems in terms of time and utility costs. In addition, there was also a concern that the use of severe volatilization conditions as described above would degrade the polymer.

Patent Document 1 discloses a devolatilization method by removing volatile matter contained in a compound having a reactive double bond under reduced pressure, but does not disclose devolatilization of a polymer.

JP 2011-252070 A

In view of the above-mentioned current situation, the object of the present invention is to provide a method for producing a polymer with a reduced amount of residual solvent by efficiently removing the solvent from a polymer solution in which the polymer is dissolved in the solvent. and

The present inventors have made intensive studies to solve the above problems, and as a result, after distilling off the solvent from the polymer solution under reduced pressure, a gaseous substance is introduced into the system to increase the pressure, and then The present inventors have found that the amount of residual solvent in the polymer can be efficiently reduced by reducing the pressure, leading to the present invention.

That is, the present invention is a method for producing a polymer with a reduced amount of residual solvent from a polymer solution in which the polymer is dissolved in a solvent, wherein the pressure of the system containing the polymer solution is set to 1 kPa or less. distilling off the solvent by reducing the pressure to , followed by introducing a substance whose state is gas at 0 ° C. into the system to raise the pressure of the system to 10 kPa or more, and then The pressure of the system is reduced to 1 kPa or less to reduce the residual solvent amount in the polymer, and the viscosity of the polymer with the reduced residual solvent amount at 23 ° C. is 0.1 Pa s to 300 Pa s. s, it relates to a method for producing a polymer.

Preferably, the residual solvent amount in the polymer whose residual solvent amount has been reduced is 2000 ppm or less, more preferably 1000 ppm or less, relative to the entire polymer. Preferably, the substance whose state is gas at 0° C. is an inert gas. Preferably, the temperature of the system during the step of distilling off the solvent is the boiling point of the solvent at 101 kPa ±20°C. Preferably, the temperature of the system during the step of distilling off said solvent is lower than the boiling point of said solvent at 101 kPa. Preferably, the solvent is an alcoholic solvent. Preferably, the polymer contains a (meth)acrylate polymer. Preferably, the polymer contains a (meth)acrylate polymer having a reactive silyl group. Preferably, said solvent comprises the solvent used in the polymerization reaction to form said polymer.

In the production method of the present invention, after the step of reducing the residual solvent amount, a substance that is gaseous at 0° C. is again introduced into the system, and the pressure of the system is increased to 10 kPa or more. and, thereafter, a step of reducing the pressure of the system to 1 kPa or less to further reduce the amount of residual solvent in the polymer can be carried out.

According to the present invention, it is possible to efficiently remove the solvent from a polymer solution in which the polymer is dissolved in the solvent, and to produce a polymer with a reduced amount of residual solvent. As a result, even if the time for which the polymer solution is placed under reduced pressure in order to volatilize the solvent is shortened, the temperature during the reduced pressure is lowered, or the atmospheric pressure is raised, a polymer with a sufficiently reduced amount of residual solvent can be obtained. manufacturing becomes possible.

Embodiments of the present invention are described in detail below.

The method for producing a polymer according to the present invention relates to a method for producing a polymer with a reduced amount of residual solvent by distilling off the solvent from a polymer solution in which the polymer is dissolved in the solvent.

The polymer to which the present invention can be applied is not particularly limited, and may be either an organic polymer or an inorganic polymer. Examples of organic polymers include (meth)acrylic acid ester polymers, polyoxyalkylene polymers, polyolefin polymers, and polyester polymers. Examples of inorganic polymers include polyorganosiloxanes. etc. The polymer used in the present invention may be one kind of polymer or a mixture of two or more kinds of polymers. The mixture of two or more polymers may be a mixture of two or more polymers composed of the same main chain system, or a mixture of two or more polymers composed of different main chain systems. In the case of a mixture of two or more polymers composed of different main chain systems, specifically, a mixture of a (meth)acrylic acid ester polymer and a polyoxyalkylene polymer can be mentioned.

Among organic polymers, it is difficult to volatilize the solvent from the polymer solution of (meth)acrylic acid ester polymers in particular to obtain a polymer that is substantially free of the solvent. It is preferable to apply the invention to efficiently reduce the residual solvent amount.

In the present invention, it is preferable to use a polymer that exhibits fluidity by itself without being diluted with a solvent or the like. By using such a polymer, it becomes possible to efficiently reduce the amount of residual solvent according to the present invention.

The (meth)acrylate polymer described above may contain a reactive functional group. The reactive functional group is not particularly limited, but preferable reactive functional groups include a reactive silyl group having an alkoxy group or the like on a silicon atom and capable of bonding to each other by hydrolysis/dehydration condensation reaction, a hydroxy group, Epoxy groups and isocyanate groups can be mentioned. A reactive silyl group is particularly preferred. In general, when the solvent is distilled off from a polymer having a reactive silyl group, the condensation reaction of the reactive silyl group proceeds unnecessarily due to the heating conditions at that time and the contamination of water under reduced pressure. Although there are cases, according to the present invention, the amount of residual solvent in the polymer can be reduced while suppressing the progress of such a condensation reaction.

The solvent to be removed by the present invention is not particularly limited as long as it dissolves the polymer. For example, hydrocarbons such as toluene, xylene, n-hexane and cyclohexane; alcoholic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, 2-butanol and isobutyl alcohol; ethyl acetate, propyl acetate; Esters such as isopropyl acetate and butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, diethyl ether, di-n-butyl ether, tetrahydrofuran (THF), tetrahydropyran (THP), t-butyl methyl ether ( MTBE), cyclopentyl methyl ether (CPME), ethers such as 1,2-dimethoxyethane (glyme), and the like. Only one of these may be used, or two or more may be mixed and used.

Among them, alcohol-based solvents are known as solvents that have a low evaporation rate and are difficult to volatilize. Among alcohol-based solvents, alcohol-based solvents with 3 to 4 carbon atoms such as isobutyl alcohol have a lower evaporation rate than other solvents with boiling points in the same range, and are difficult to volatilize and remove. is a solvent. In particular, from a polymer solution in which a (meth)acrylic acid ester polymer is dissolved in an alcoholic solvent, it has been difficult to reduce the amount of residual solvent by distilling off the alcoholic solvent. However, according to the present invention, it is possible to efficiently reduce the amount of residual solvent even from a polymer solution in which reduction of the amount of residual solvent has conventionally been difficult.

The solvent removed by the present invention may be the solvent used in the polymerization reaction to form said polymer. That is, the present invention may be applied to polymerize a monomer in the presence of a solvent to obtain a solution containing the polymer, and then distill off the solvent from the solution. That is, in the production method of the present invention, before the step of reducing the solvent, a step of polymerizing a monomer in the presence of a solvent to obtain a polymer solution may be performed, and the reaction obtained in the polymerization step The step of distilling off the solvent described below may be performed directly on the liquid. According to this aspect, it is possible to efficiently remove the solvent from the reaction solution obtained by performing polymerization in the presence of the solvent, and to obtain a polymer with a reduced amount of residual solvent.

When the step of distilling off the solvent continuously from the polymerization step is carried out, the reaction temperature during the polymerization may be maintained and the step of distilling off the solvent may be carried out at that temperature. By doing so, the temperature control of the system becomes simple, which is preferable.

The polymerization method is not particularly limited as long as it is a polymerization method for forming the polymer. For example, when the polymer is a (meth)acrylic acid ester polymer, a radical polymerization method can be used, Either a free radical polymerization method or a living radical polymerization method may be used.

The polymer concentration of the polymer solution to which the present invention is applicable is not particularly limited. For example, the polymer concentration may be about 0.1 to 80% by weight.

According to the present invention, first, the step of distilling off the solvent by reducing the pressure of the system containing the polymer solution to 1 kPa or less (hereinafter also referred to as the first pressure reduction step) is performed. By carrying out this step, the amount of residual solvent in the polymer is reduced to some extent. The residual solvent amount to be achieved in this step is not particularly limited, but is preferably 100000 ppm or less, more preferably 10000 ppm or less, even more preferably 5000 ppm or less, and even more preferably 3000 ppm or less.

The lower limit of the amount of residual solvent achieved in this step is not particularly limited because it depends on the viscosity of the polymer, the type of solvent, or the conditions of the step, but it never becomes zero. Usually, there is a limit to the amount of residual solvent that can be achieved only by this first decompression step, and once the amount of residual solvent reaches a certain level, further reduction often becomes difficult. Specifically, it is usually 1000 ppm or more, and may be 2000 ppm or more.

The first decompression step can be performed by a conventional method, but since the second decompression step described later is performed, the temperature, the degree of decompression, and the decompression time in the first decompression step are relatively loose conditions. ie lower temperature, higher pressure, shorter decompression time.

Specifically, the temperature of the system in the first decompression step can be appropriately set in consideration of the boiling point of the solvent at the degree of decompression, and is not particularly limited. However, the temperature of the system in the first depressurization step may be relatively low, preferably in the range of the boiling point of the solvent at 101 kPa (atmospheric pressure) ± 20 ° C., and the temperature of the solvent at 101 kPa is preferably lower than the boiling point of Specifically, the temperature of the system is preferably about 50 to 150.degree. It is preferable to carry out the depressurization step at a relatively low temperature because deterioration of the polymer can be avoided.

In addition, the pressure of the system in the first decompression step may be decompressed to 1 kPa or less, and the lower limit is not particularly limited as long as it is a value that can be achieved with a normal vacuum apparatus.

The decompression time in the first decompression step is not particularly limited, and can be set appropriately by those skilled in the art. Therefore, it may be a relatively short period of time. It is preferable to perform the depressurization step in a short time because productivity can be improved. Although it depends on the volume and concentration of the polymer solution, specifically, the decompression time in the first decompression step may be 300 minutes or less, may be 200 minutes or less, or may be 150 minutes or less. It may be 100 minutes or less. Although the lower limit is not particularly limited, it is preferably 10 minutes or longer, more preferably 30 minutes or longer.

After the first depressurization step described above, a step of introducing a substance that is gaseous at 0° C. (hereinafter also referred to as a gaseous substance) into the system and raising the pressure of the system to 10 kPa or more. (hereinafter also referred to as a step of introducing a gaseous substance) is performed. By carrying out the following second decompression step after carrying out the step of introducing the gaseous substance, it becomes possible to efficiently reduce the residual solvent amount of the polymer.

The gaseous substance used in this step is not particularly limited as long as it is a substance that can be easily removed in the following second decompression step. For example, it may be air or oxygen gas, or it may be a hydrocarbon-based gas such as methane. However, in order to avoid degrading the polymer or reacting with the reactive functional groups of the polymer, the gaseous substance is preferably an inert gas. As such an inert gas, for example, nitrogen gas, argon, helium, and neon are preferable, and nitrogen gas is particularly preferable, because of ease of handling.

The method of introducing the gaseous substance into the system is not particularly limited. good too.

By introducing the gaseous substance into the system, the pressure of the system depressurized in the first depressurization step is raised to 10 kPa or more. By once increasing the pressure of the system in this way, it becomes possible to efficiently reduce the amount of residual solvent in the next second depressurization step. The atmospheric pressure after the increase is preferably 50 kPa or higher, more preferably 80 kPa or higher. Moreover, since the operation becomes simple and the reduction of the residual solvent amount is also effective, the pressure may be raised to 101 kPa (atmospheric pressure). Furthermore, a pressurization condition exceeding 101 kPa may be used.

The temperature of the system when the gaseous substance is introduced into the system is not particularly limited, but the temperature of the system when performing the first depressurization step may be maintained. In this case, the process becomes simple, which is preferable.

After once increasing the pressure of the system as described above, the step of reducing the pressure of the system to 1 kPa or less to reduce the solvent (hereinafter also referred to as the second pressure reduction step) is performed. By carrying out this step, a polymer with a reduced amount of residual solvent can be obtained. According to a preferred embodiment of the present invention, it is possible to obtain a polymer exhibiting a low residual solvent amount that cannot be achieved even if one depressurization step is performed for a long time.

The second depressurization step can also be carried out by a conventional method in the same manner as the first depressurization step. The temperature, the degree of pressure reduction, and the pressure reduction time in the second pressure reduction step may also be relatively mild conditions, that is, a relatively low temperature, a relatively high atmospheric pressure, and a relatively short pressure reduction time. The temperature, pressure, and decompression times detailed for the first decompression step can also be applied to the second decompression step. The temperature and pressure in the second pressure reduction step may be the same as the temperature and pressure in the first pressure reduction step. In particular, the temperature may be the same throughout the first depressurization step, the gaseous substance introduction step, and the second depressurization step, which is preferred because it simplifies the process. Further, the pressure reduction time in the second pressure reduction step may be shorter than the pressure reduction time in the first pressure reduction step, for example, it may be 80 minutes or less, 60 minutes or less, or 30 minutes or less. There may be.

According to the present invention, there is an advantage that the first decompression step, the gaseous substance introduction step, and the second decompression step can be performed in the same vessel. It is extremely preferable to carry out the reaction in the same vessel, since a polymer with a reduced amount of residual solvent can be easily obtained from the polymer solution. Further, in the case of the embodiment in which the present invention is applied directly to the reaction solution obtained in the polymerization step, the polymerization step, the first decompression step, the gaseous substance introduction step, and 2 are carried out in the same container. The second decompression step can be carried out continuously. In this case, it is possible to recover the polymer substantially free of solvent from the container in which the polymerization was carried out in the solvent.

The present invention may be composed of the first decompression step, the gaseous substance introduction step, and the second decompression step described above. A second step of introducing a gaseous substance and a third step of depressurizing may be performed. This makes it possible to further reduce the amount of residual solvent in the polymer. The specific conditions of the second gaseous substance introduction step and the third pressure reduction step can conform to the conditions of the first gaseous substance introduction step and the second pressure reduction step. In addition, the step of introducing the gaseous substance for the third and subsequent times, and the step of decompressing the pressure for the fourth and subsequent times may be carried out subsequently.

According to a preferred embodiment of the present invention, even if the time required for each decompression step is short, it is possible to efficiently reduce the amount of residual solvent in the polymer, and the total time required for multiple decompression steps It can also be shortened. Despite such a short total time required for decompression, it is possible to achieve a residual solvent amount lower than the residual solvent amount that can be reached by only one decompression step, which is extremely preferable from the viewpoint of productivity. .

The polymer with a reduced amount of residual solvent obtained by the present invention has a viscosity of 0.1 Pa.s at 23°C. s to 300 Pa.s s. According to the present invention, a polymer exhibiting such viscosity can be efficiently produced. It is of little significance to apply the present invention to a polymer having a viscosity lower than the above range, and it is difficult to distill off the solvent from a polymer having a viscosity higher than the above range. Said viscosity is preferably 1 Pa.s. s to 200 Pa.s s, more preferably 5 Pa.s. s~150Pa.s is s.

Further, according to the present invention, the amount of residual solvent in the polymer produced is not limited, but according to a preferred embodiment, it is possible to achieve 2000 ppm or less with respect to the entire polymer, and further, 1000 ppm You can also achieve: It was difficult to achieve such a low residual solvent amount by performing only one solvent distillation step, but the present invention has made it possible.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

(Synthesis example)
77 parts by weight of isobutyl alcohol (boiling point at 101 kPa: 107° C.) was added to the flask, heated to 105° C., and purged with nitrogen. Thereafter, while stirring, under a nitrogen atmosphere, 3.0 parts by weight of methyl methacrylate, 73.2 parts by weight of butyl acrylate, 1.9 parts by weight of 3-(trimethoxysilyl)propyl methacrylate, and 3 parts of methacrylic acid were added as monomers. -(methyldimethoxysilyl)propyl 1.9 parts by weight, 20 parts by weight of 2-ethylhexyl acrylate, 2.6 parts by weight of dimethyl 2,2'-azobis(2-methylpropionate) as a polymerization initiator, and isobutyl A solution of 13 parts by weight of alcohol was added dropwise over 5 hours, and then polymerization was carried out for 2 hours. As described above, an isobutyl alcohol solution of a (meth)acrylic acid ester polymer having a weight average molecular weight of 8,600 and having a reactive silicon group was obtained.

The weight average molecular weight is a polystyrene equivalent molecular weight measured using HLC-8220GPC manufactured by Tosoh Corporation as a liquid delivery system, using TSKgel SuperH series manufactured by Tosoh Corporation as a column, and using THF as a solvent.

(Examples 1 to 4)
While maintaining the temperature of the isobutyl alcohol solution of the (meth)acrylate polymer having a reactive silicon group obtained in Synthesis Example at 105° C., isobutyl alcohol was devolatilized under reduced pressure as follows.

First, the pressure was reduced to less than 1 kPa, and the pressure reduction time described in Table 1 was maintained (first devolatilization). After that, nitrogen gas was introduced into the system over 5 minutes to return the atmospheric pressure of the system to normal pressure (first pressure return).

Then, devolatilization was performed for the second time. First, the pressure was reduced to 1 kPa over the pressure reduction time until reaching 1 kPa described in Table 1, and then the pressure of less than 1 kPa was maintained for the pressure reduction time of less than 1 kPa described in Table 1 (second devolatilization). After that, nitrogen gas was again introduced into the system over 5 minutes to return the atmospheric pressure of the system to normal pressure (second pressure return).

Subsequently, devolatization was performed for the third time. First, the pressure was reduced to 1 kPa over the pressure reduction time until reaching 1 kPa described in Table 1, and then the pressure of less than 1 kPa was maintained for the pressure reduction time of less than 1 kPa described in Table 1 (third devolatilization).

After each depressurization, the content of isobutyl alcohol contained in the (meth)acrylic acid ester polymer was quantified. Isobutyl alcohol is quantified by gas chromatography (Agilent 7890A manufactured by Agilent Technologies Inc. as a GC system, HP-INNOWAX manufactured by Agilent Technologies Inc. as a column, using acetone as a measurement solvent, and detected by FID). I used it. The quantitative results of isobutyl alcohol are shown in Table 1 as the amount of residual solvent.

In any of Examples 1 to 4, after the third devolatilization, the amount of residual solvent in the polymer was about 500 ppm, and the viscosity of the resulting polymer at 23°C was about 30 Pa·s. rice field.

In the first devolatilization in Examples 1 to 4, regardless of the length of the depressurization time (50 to 190 minutes), the amount of residual solvent exceeded 2000 ppm, showing similarly high numerical values. From this, it can be seen that it is difficult to reduce the residual solvent amount to less than 2000 ppm in one devolatilization even if the depressurization time is lengthened. On the other hand, in any of the examples, by introducing the gas and performing the second devolatilization after the first devolatilization, the residual solvent amount could be greatly reduced to less than 1,000 ppm. From the above, it can be seen that the residual solvent amount in the polymer can be greatly reduced by introducing a gas and performing the second devolatilization after the first devolatilization.

Further, for example, the first depressurization time in Example 2 was 190 minutes and the residual solvent amount was 2,000 ppm or more, but in Example 4, the total time including the first devolatilization and the second devolatilization Although the time is 95 minutes, which is half the first pressure reduction time in Example 2, the amount of residual solvent is reduced to less than 1,000 ppm. As a result, by introducing a gas and performing the second devolatilization after the first devolatilization, it is possible to greatly reduce the amount of residual solvent in the polymer while significantly shortening the time required for devolatilization. I understand.

Further, from each example, it can be seen that the amount of residual solvent in the polymer can be further reduced by performing the second gas introduction and the third devolatilization after the second devolatilization. For example, when comparing the first devolatilization in Example 1 and the third devolatilization in Example 4, the amount of residual solvent in Example 4 was 4 minutes, although the time required was approximately the same. It can be seen that it has decreased to about 1.

Claims (11)

A method for producing a polymer with a reduced amount of residual solvent from a polymer solution in which the polymer is dissolved in a solvent,
a step of reducing the pressure of the system containing the polymer solution to 1 kPa or less to distill off the solvent;
Subsequently, a step of introducing a substance whose state is a gas at 0 ° C. into the system and increasing the pressure of the system to 10 kPa or more, and then reducing the pressure of the system to 1 kPa or less and heavy reducing the amount of residual solvent during coalescence;
The viscosity at 23 ° C. of the polymer in which the amount of residual solvent is reduced is 0.1 Pa s to 300 Pa s,
A method for producing a polymer, wherein the substance that is gaseous at 0° C. includes at least one substance selected from the group consisting of air, oxygen gas, hydrocarbon-based gas, and inert gas. 2. The production method according to claim 1, wherein the residual solvent amount in the polymer with the reduced residual solvent amount is 2000 ppm or less with respect to the entire polymer. 3. The production method according to claim 2, wherein the residual solvent amount in the reduced residual solvent amount polymer is 1000 ppm or less with respect to the entire polymer. The production method according to any one of claims 1 to 3, wherein the substance whose state is gas at 0°C is an inert gas. The production method according to any one of claims 1 to 4, wherein the temperature of the system during the step of distilling off the solvent is the boiling point of the solvent at 101 kPa ±20°C. The production method according to any one of claims 1 to 5, wherein the temperature of the system during the step of distilling off the solvent is lower than the boiling point of the solvent at 101 kPa. The production method according to any one of claims 1 to 6, wherein the solvent is an alcohol solvent. The production method according to any one of claims 1 to 7, wherein the polymer comprises a (meth)acrylic acid ester polymer. 9. The production method according to claim 8, wherein the polymer comprises a (meth)acrylate polymer having a reactive silyl group. A process according to any one of claims 1-9, wherein the solvent comprises the solvent used in the polymerization reaction to form the polymer. After the step of reducing the residual solvent amount,
Again, introducing a substance whose state is gas at 0 ° C. into the system to raise the pressure of the system to 10 kPa or more, and then reducing the pressure of the system to 1 kPa or less to polymer The production method according to any one of claims 1 to 10, wherein a step of further reducing the amount of residual solvent in is carried out.