Aqueous solution of acrylic acid polymer, method for producing the same, and cleaning agent
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOAGOSEI CO LTD
- Filing Date
- 2024-12-25
- Publication Date
- 2026-07-07
Smart Images
Figure 2026112619000001
Abstract
Description
Technical Field
[0001] The present invention relates to an aqueous acrylic acid polymer solution, a method for producing the same, and a cleaning agent.
Background Art
[0002] An acrylic acid polymer containing an acrylic acid polymer and water has an effect of adsorbing to fine particles in an aqueous solution and enhancing the dispersibility of the fine particles. Therefore, the aqueous acrylic acid polymer solution is used in various applications such as a dispersant for producing a dispersion liquid having high dispersion stability and a cleaning agent for cleaning foreign substances attached to the surface of an object to be cleaned, for example, in the field of electronic materials.
[0003] For example, Patent Document 1 describes a semiconductor component cleaning composition characterized by containing a water-soluble polymer (a) having a weight average molecular weight in terms of sodium polystyrene sulfonate measured by gel permeation chromatography of 1,000 to 100,000 and a compound (b) represented by the following formula (1). NR4OH (1) (In formula (1), each R independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] By the way, depending on the use of the aqueous acrylic acid polymer solution, an aqueous acrylic acid polymer solution containing an acrylic acid polymer having a small weight average molecular weight and having a low pH may be desired. However, such an aqueous solution has low storage stability, and there is a risk that the polymer aggregates relatively early and the desired performance cannot be obtained.
[0006] Furthermore, when the aqueous solution is used, for example, as a cleaning agent for semiconductor components, microfiltration may be performed to remove foreign matter from the aqueous solution. However, if polymers aggregate in the aqueous solution, turbidity may occur, which may hinder microfiltration.
[0007] This invention was made in view of the above background, and aims to provide an aqueous solution of an acrylic acid polymer with excellent storage stability, a method for producing the same, and a cleaning agent. [Means for solving the problem]
[0008] One aspect of the present invention relates to aqueous solutions of acrylic acid polymers according to the following [1] to [3].
[0009] [1] An aqueous solution of an acrylic acid polymer comprising an acrylic acid polymer consisting of repeating units (a) derived from acrylic acid and repeating units (b) derived from an acrylic acid ester, The weight-average molecular weight of the acrylic acid polymer is 1,500 or more and 10,000 or less. The acrylic acid ester is an ester of acrylic acid and an alcohol having 1 to 4 carbon atoms. An aqueous solution of an acrylic acid polymer, wherein the pH of the aqueous solution of the acrylic acid polymer is 2.5 or less.
[0010] [2] The aqueous solution of the acrylic acid polymer according to [1], wherein the content of the repeating unit (b) in the acrylic acid polymer is 1.5% by mass or more and 5.0% by mass or less with respect to all repeating units contained in the acrylic acid polymer. [3] An aqueous solution of the acrylic acid polymer according to [1] or [2], wherein the concentration of the acrylic acid polymer is 30% by mass or more and 50% by mass or less.
[0011] Another aspect of the present invention is a cleaning agent according to [4] below. A cleaning agent comprising an aqueous solution of an acrylic acid polymer described in any one of [4], [1] to [3], A detergent wherein the concentration of the acrylic acid polymer is 100 ppm by mass or more and 10,000 ppm by mass or less.
[0012] Further aspects of the present invention relate to methods for producing aqueous solutions of acrylic acid polymers according to the following [5] to
[10] .
[0013] A method for producing an aqueous solution of an acrylic acid polymer as described in any one of [5] [1] to [3], A polymerization step in which a monomer containing acrylic acid is polymerized in a polymerization solvent containing the aforementioned alcohol, A method for producing an aqueous solution of an acrylic acid polymer, comprising: an esterification step in which, in the polymerization solvent, a solid acid catalyst having a sulfo group is brought into contact with the reaction product obtained by the polymerization, thereby reacting the alcohol with a portion of the repeating unit (a) in the reaction product to form the repeating unit (b).
[0014] [6] A method for producing an aqueous solution of an acrylic acid polymer according to [5], wherein the polymerization step and the esterification step are carried out in parallel. [7] A method for producing an aqueous solution of an acrylic acid polymer according to [5] or [6], wherein the content of the acrylic acid in the monomer is 95 parts by mass or more per 100 parts by mass of the monomer. [8] A method for producing an aqueous solution of an acrylic acid polymer according to any one of [5] to [7], wherein the polymerization solvent comprises one or more alcohols selected from the group consisting of primary alcohols and secondary alcohols.
[0015] [9] A method for producing an aqueous solution of an acrylic acid polymer according to any one of [5] to [8], wherein the solid acid catalyst is composed of one or more compounds selected from the group consisting of polymers that contain repeating units derived from styrene and are modified with sulfo groups, and inorganic oxides having sulfo groups on their surface.
[10] A method for producing an aqueous solution of an acrylic acid polymer according to [5] to [9], wherein in the esterification step, particles of the solid acid catalyst are brought into contact with the reaction product. [Effects of the Invention]
[0016] The acrylic acid-based polymer aqueous solution (hereinafter referred to as "aqueous solution") contains an acrylic acid-based polymer (hereinafter referred to as "polymer") composed of a repeating unit (a) derived from acrylic acid and a repeating unit (b) derived from an acrylic acid ester. A polymer containing both the repeating unit (a) and the repeating unit (b) has a small weight average molecular weight and is difficult to aggregate even when the pH of the aqueous solution is low. Therefore, the aqueous solution has excellent storage stability and can maintain desired performance over a long period of time.
[0017] In addition, since the cleaning agent contains the aqueous solution, it has excellent storage stability and can maintain high cleaning performance over a long period of time. Furthermore, the cleaning agent can suppress the generation of turbidity that hinders fine filtration and can maintain a transparent state over a long period of time.
[0018] The method for producing the aqueous solution has a polymerization step and an esterification step. In the esterification step, by bringing the solid acid catalyst into contact with the reaction product in the polymerization step in a polymerization solvent, the repeating unit (a) in the reaction product and the alcohol in the polymerization solvent can be appropriately reacted to form the repeating unit (b). As a result, the aqueous solution can be easily obtained.
[0019] As described above, according to the above aspect, it is possible to provide an acrylic acid-based polymer aqueous solution excellent in storage stability, a method for producing the same, and a cleaning agent.
Embodiments for Carrying Out the Invention
[0020] (Acrylic acid-based polymer aqueous solution) The aqueous solution contains the polymer and water. In the aqueous solution, components other than the polymer and water may be contained as necessary. For example, an alcohol having 1 to 4 carbon atoms may be contained in the aqueous solution. When the aqueous solution is used as a cleaning agent that requires precise cleaning, such as a cleaning agent for semiconductor components, it is preferable that the aqueous solution is composed of the polymer, water, and an alcohol having 1 to 4 carbon atoms. In this case, by setting the content of the alcohol having 1 to 4 carbon atoms in the aqueous solution to preferably 0.1% by mass or more and 3.0% by mass or less, more preferably 1.0% by mass or more and 2.5% by mass or less, the progress of hydrolysis of the polymer can be suppressed.
[0021] 〔Acrylic acid-based polymer〕 The polymer contained in the aqueous solution includes an acrylic acid-based polymer composed of a repeating unit (a) derived from acrylic acid and a repeating unit (b) derived from an acrylic acid ester. The weight average molecular weight of the polymer is 1,500 or more and 10,000 or less. Further, the pH of the aqueous solution is 2.5 or less. Since an aqueous solution containing such a polymer has excellent dispersibility of fine particles, it can be suitably used for applications such as a dispersant for improving the dispersion stability of a dispersion liquid, a cleaning agent for cleaning foreign substances attached to the surface of an object to be cleaned, and the like.
[0022] When the weight average molecular weight of the polymer is less than 1,500, the dispersibility of the fine particles is low, and there is a risk that the desired performance cannot be obtained. Therefore, for example, when the aqueous solution is used as a dispersant, there is a risk of causing a decrease in the dispersion stability of the dispersion liquid. Further, for example, when the aqueous solution is used as a cleaning agent, there is a risk of causing a decrease in the cleaning performance. From the viewpoint of further enhancing the dispersibility of the fine particles, the weight average molecular weight of the polymer is preferably 2,000 or more, more preferably 2,200 or more, and even more preferably 2,500 or more.
[0023] On the other hand, if the weight-average molecular weight of the polymer exceeds 10,000, the adsorption of the polymer to solid surfaces may become excessively high. Therefore, for example, when the aqueous solution is used as a dispersant, aggregates of the polymer and fine particles may easily form, which may actually lead to a decrease in the dispersion stability of the dispersion. Also, for example, when the aqueous solution is used as a cleaning agent, the polymer adsorbed on the surface of the object to be cleaned may become difficult to detach from the object, and the object to be cleaned may become easily contaminated by the polymer. From the viewpoint of more easily avoiding these problems, the weight-average molecular weight of the polymer is preferably 9,000 or less, more preferably 8,000 or less, and even more preferably 7,000 or less.
[0024] In determining the preferred range for the weight-average molecular weight of the polymer, the upper and lower limits of the weight-average molecular weight of the polymer described above can be arbitrarily combined. For example, the preferred range for the weight-average molecular weight of the polymer may be 2,000 to 9,000, 2,200 to 8,000, or 2,500 to 7,000.
[0025] The weight-average molecular weight of the polymer is a sodium polyacrylate equivalent value obtained by converting the retention time measured by gel permeation chromatography (GPC) to molecular weight using sodium polyacrylate as a standard substance.
[0026] If the pH of the aqueous solution exceeds 2.5, it may lead to a decrease in the dispersibility of the fine particles. From the viewpoint of further improving the dispersibility of the fine particles, the pH of the aqueous solution is preferably 2.4 or less, more preferably 2.3 or less, even more preferably 2.2 or less, and particularly preferably 2.1 or less.
[0027] From the viewpoint of the dispersibility of fine particles, the lower limit of the pH of the aqueous solution is not particularly limited, however, if the acid contained in the aqueous solution is only the polymer, the lower limit of the pH of the aqueous solution is 1.5. Therefore, if the acid contained in the aqueous solution is only the polymer, the pH of the aqueous solution is preferably 1.5 or more and 2.5 or less, more preferably 1.5 or more and 2.4 or less, even more preferably 1.5 or more and 2.3 or less, particularly preferably 1.5 or more and 2.2 or less, and most preferably 1.5 or more and 2.1 or less.
[0028] [Acrylic acid polymer] In the aqueous solution, the acrylic acid polymer may be in an unneutralized state or partially neutralized by an alkali. In either case, the storage stability of the aqueous solution can be improved by using a polymer having both the repeating unit (a) and the repeating unit (b). From the viewpoint of improving the storage stability of the aqueous solution and making it easier to lower the pH of the aqueous solution, it is preferable that the acrylic acid polymer in the aqueous solution is in an unneutralized state, that is, that all of the repeating units (a) in the polymer have carboxyl groups.
[0029] The acrylic acid ester that forms the repeating unit (b) in the polymer is an ester of acrylic acid and an alcohol having 1 to 4 carbon atoms. If the alcohol in the acrylic acid ester has 5 or more carbon atoms, it may lead to a decrease in the solubility of the polymer in water.
[0030] The polymer may contain one type of repeating unit (b), or it may contain two or more types of repeating units (b). Examples of acrylic acid esters that serve as repeating units (b) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate.
[0031] The acrylic acid ester is preferably an ester of acrylic acid with an alcohol having 3 to 4 carbon atoms, and more preferably an ester of acrylic acid with an alcohol having 3 carbon atoms. In this case, the storage stability of the aqueous solution can be further improved.
[0032] The content of the repeating unit (b) in the acrylic acid polymer is preferably 1.5% by mass or more and 5.0% by mass or less relative to all repeating units contained in the polymer. By setting the content of the repeating unit (b) in the polymer to preferably 1.5% by mass or more, more preferably 2.0% by mass or more, and even more preferably 2.5% by mass or more, the storage stability of the aqueous solution can be further improved. Furthermore, by setting the content of the repeating unit (b) in the polymer to preferably 5.0% by mass or less, more preferably 4.0% by mass or less, and even more preferably 3.5% by mass or less, the pH of the aqueous solution can be lowered more easily without impairing the storage stability of the aqueous solution.
[0033] In determining a preferred range for the content of the repeating unit (b), the upper and lower limits of the content of the repeating unit (b) described above can be arbitrarily combined. For example, the preferred range for the content of the repeating unit (b) may be 1.5% by mass or more and 5.0% by mass or less, 2.0% by mass or more and 4.0% by mass or less, or 2.5% by mass or more and 3.5% by mass or less, relative to all repeating units contained in the polymer.
[0034] The content of the repeating unit (b) in the polymer is, for example, the content of the polymer 1 It can be calculated based on the H-NMR spectrum.
[0035] The polymer may contain repeating units other than repeating unit (a) and repeating unit (b) to the extent that it does not impair the storage stability of the aqueous solution and the dispersibility of the fine particles. The content of repeating units other than repeating unit (a) and repeating unit (b) is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and most preferably 0% by mass, that is, the polymer is composed of repeating unit (a) and repeating unit (b).
[0036] The concentration of the acrylic acid polymer in the aqueous solution is preferably 30% by mass or more and 50% by mass or less. Since the polymer contains both repeating unit (a) and repeating unit (b), it is less likely to aggregate in the aqueous solution. Therefore, the aqueous solution has high storage stability even when the concentration of the polymer is within the specified range. In this case, when the aqueous solution is used as a raw material for chemical solutions such as detergents or dispersants, a large amount of chemical solution can be prepared from a small amount of the aqueous solution.
[0037] (Cleaning agent) As mentioned above, the aqueous solution has excellent dispersibility of fine particles, making it suitable as a cleaning agent for removing foreign matter such as fine particles adsorbed on the surface of an object to be cleaned. When the aqueous solution is used as a cleaning agent, the concentration of the polymer in the aqueous solution is preferably 100 ppm by mass or more and 10,000 ppm by mass or less.
[0038] The method for preparing the cleaning agent is not particularly limited, and known methods can be used as appropriate. For example, the method for preparing the cleaning agent from the aqueous solution may include steps such as diluting the aqueous solution with water or microfiltration of the aqueous solution.
[0039] The object to be cleaned by the cleaning agent is not particularly limited, but the cleaning agent is preferably used as a cleaning agent for semiconductor components for cleaning semiconductor components of various materials and shapes. The cleaning agent for semiconductor components is preferably composed of the acrylic acid ester polymer and water. Furthermore, the polymer contained in the cleaning agent for semiconductor components is preferably composed of the repeating unit (a) and the repeating unit (b).
[0040] The object to be cleaned by the cleaning agent may be, for example, a semiconductor component made of silicon, glass, ceramics, etc. Furthermore, at least a portion of the surface of the semiconductor component to be cleaned may be composed of, for example, single-crystal silicon, polycrystalline silicon, amorphous silicon, thermal silicon oxide film, undoped silicate glass film, phosphorus-doped silicate glass film, boron-doped silicate glass film, phosphorus-boron-doped silicate glass film, tetraethyl orthosilicate (TEOS) film, plasma CVD oxide film, silicon nitride film, silicon carbide film, silicon acid carbide film, silicon oxynitride film, silicon carbonitride film, or silicon acid carbonitride film. In addition, at least a portion of the surface of the semiconductor component to be cleaned may be composed of metal, glass, quartz, crystal, ceramics, etc. Furthermore, the surface of the semiconductor component to be cleaned may be composed of one of the aforementioned materials, or two or more materials. When two or more materials are present on the surface of the semiconductor component, these materials may be patterned using techniques such as photolithography, or they may be stacked on top of each other.
[0041] The cleaning agent is used, for example, in a cleaning process performed during the manufacturing of semiconductor components. The cleaning process is performed at various timings, such as before CMP (chemical mechanical polishing), after CMP, before CVD (chemical vapor deposition), after CVD, after resist development, after dry etching, after wet etching, after dry ashing, and after resist stripping. From the viewpoint of effectively utilizing the high cleaning performance, it is preferable to use the cleaning agent in the cleaning process after CMP.
[0042] The method for cleaning semiconductor components is not particularly limited, and known cleaning methods can be used as appropriate. More specifically, cleaning methods for semiconductor components include dip cleaning, in which the semiconductor component is immersed in a cleaning agent in a cleaning tank; spin cleaning, in which the semiconductor component is rotated at high speed while a cleaning agent flows down onto the semiconductor component from a nozzle; and spray cleaning, in which a cleaning agent is sprayed onto the semiconductor component. Furthermore, as a cleaning apparatus, a batch-type cleaning apparatus that cleans multiple semiconductor components contained in a cassette simultaneously may be used, or a single-wafer cleaning apparatus that removes a single semiconductor component from the cassette, mounts it in a holder, and cleans each component individually may be used.
[0043] The contact time between the cleaning agent and the semiconductor component during the cleaning process can be appropriately selected depending on the cleaning method. For example, when cleaning semiconductor components using a batch-type cleaning device, the contact time between the cleaning agent and the semiconductor component may be 0.5 minutes to 1 hour, 1 minute to 30 minutes, or 1 minute to 15 minutes. Similarly, when cleaning semiconductor components using a single-wafer cleaning device, the contact time between the cleaning agent and the semiconductor component may be 1 second to 15 minutes, 5 seconds to 10 minutes, or 5 seconds to 5 minutes.
[0044] When cleaning semiconductor components with a cleaning agent after the polishing process, the cleaning of the semiconductor components may be performed on the polishing platen or after removal from the polishing apparatus. When cleaning semiconductor components on the polishing platen, for example, a method can be employed in which the cleaning agent is supplied to the semiconductor components on the polishing platen while moving the polishing pad. In this case, in addition to the chemical cleaning action of the cleaning agent, foreign matter on the surface of the semiconductor components can be physically removed by the polishing pad. As a result, impurities such as foreign matter and metal ions on the surface of the semiconductor components can be effectively cleaned.
[0045] When cleaning semiconductor components after removing them from a polishing device, the cleaning agent should be brought into contact with the removed semiconductor components. In this case, in addition to the chemical cleaning action of the cleaning agent, foreign matter on the semiconductor components can be physically removed by the flow of the cleaning agent when it comes into contact with the semiconductor components. As a result, foreign matter and impurities such as metal ions on the surface of the semiconductor components can be effectively cleaned. If a polishing pad is not used during cleaning, physical cleaning with a cleaning cloth or cleaning brush may be used in combination.
[0046] (Method for producing aqueous solution of acrylic acid polymer) The method for producing the aqueous solution of the acrylic acid polymer can take various forms. For example, the aqueous solution of the acrylic acid polymer can be obtained by polymerizing monomers containing acrylic acid and acrylic acid ester in a polymerization solvent containing water.
[0047] From the viewpoint of more easily obtaining the aqueous solution with excellent storage stability, the method for producing the aqueous solution of the acrylic acid polymer is: A polymerization step in which a monomer containing acrylic acid is polymerized in a polymerization solvent containing the aforementioned alcohol, Preferably, the process includes an esterification step in which, in the polymerization solvent, a solid acid catalyst having a sulfo group is brought into contact with the reaction product obtained by polymerization, thereby reacting the alcohol with a portion of the repeating unit (a) in the reaction product to form the repeating unit (b).
[0048] In the esterification step, when a solid acid catalyst having a sulfo group is brought into contact with the reaction product obtained by polymerization, the repeating unit (a) in the reaction product is appropriately esterified. Furthermore, by esterifying the repeating unit (a) in this manner, it is thought that the positional bias of the repeating unit (b) introduced into the molecular chain of the polymer can be reduced, thereby suppressing the association of the molecular chain of the polymer during the manufacturing process of the aqueous solution and after the manufacturing of the aqueous solution. Therefore, by a manufacturing method comprising the polymerization step and the esterification step, the aqueous solution with excellent storage stability can be obtained more easily. The steps of the manufacturing method will be described in more detail below.
[0049] [Polymerization process] In the polymerization step, a monomer containing acrylic acid is polymerized by solution polymerization in a polymerization solvent containing an alcohol having 1 to 4 carbon atoms. The polymerization solvent may contain one type of alcohol or two or more types of alcohol.
[0050] The polymerization solvent may consist of an alcohol having 1 to 4 carbon atoms. In addition to the alcohol, the polymerization solvent may also contain an organic solvent soluble in the alcohol, such as methyl ethyl ketone, or water. It is preferable that the organic solvent contained in the polymerization solvent has a lower boiling point than water. In this case, the organic solvent can be easily removed from the polymerization solvent after the polymerization and esterification steps are completed.
[0051] The polymerization solvent preferably contains an alcohol having 3 to 4 carbon atoms, and more preferably an alcohol having 3 carbon atoms. In this case, the storage stability of the aqueous solution can be further improved.
[0052] Furthermore, it is preferable that the polymerization solvent contains one or more alcohols selected from the group consisting of primary alcohols and secondary alcohols. In this case, the repeating unit (b) can be introduced into the polymer more reliably.
[0053] From the viewpoint of improving the storage stability of the aqueous solution and facilitating the synthesis of polymers with a low weight-average molecular weight, it is preferable that the polymerization solvent contains isopropyl alcohol as the alcohol. From a similar viewpoint, it is more preferable that the polymerization solvent is composed of isopropyl alcohol.
[0054] The monomer used in the polymerization process may consist of acrylic acid. In addition to acrylic acid, the monomer may also contain compounds that can polymerize with acrylic acid, such as acrylic acid esters, acrylamide, acrylonitrile, methacrylic acid, and methacrylic acid esters.
[0055] From the viewpoint of further improving the dispersibility of fine particles, the content of acrylic acid in the monomer is preferably 95 parts by mass or more, more preferably 99 parts by mass or more, and even more preferably 100 parts by mass, i.e., the monomer is composed solely of acrylic acid.
[0056] In the polymerization process, the polymerization initiator used for monomer polymerization is not particularly limited, and known radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used. Furthermore, in the polymerization process, monomers may be polymerized using one type of polymerization initiator, or two or more types of polymerization initiators may be used in combination to polymerize monomers.
[0057] Examples of azo compounds include 1-[(1-cyano-1-methylethyl)azo]formamide, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis{2-[N-(2-hydroxyethyl)amidino]propane} dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, and 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxy(hydroxy) Examples include methyl(ethyl)propionamide, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(2-methylpropionamide) dihydrate, 4,4'-azobis-4-cyanovaleic acid, 2,2'-azobis[2-(hydroxymethyl)propionitrile], 2,2'-azobis[2-(2-imidazolin-2-yl)propane] disulfate, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate, and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide].
[0058] Examples of organic peroxides include t-butyl peroxide, t-butyl peroxypivalate, di-t-butyl peroxide, benzoyl peroxide, orthochlorobenzoyl peroxide, and orthomethoxybenzoyl peroxide.
[0059] Examples of persulfates include sodium persulfate, potassium persulfate, and ammonium persulfate.
[0060] The reaction conditions in the polymerization process can be appropriately set according to the type of polymerization initiator used in the polymerization process. For example, the amount of polymerization initiator used in the polymerization process can be appropriately set within the range of 0.2 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of monomer. By setting the amount of polymerization initiator in the polymerization process to 0.2 parts by mass or more per 100 parts by mass of monomer, the polymerization of monomer can proceed sufficiently, and the amount of unreacted monomer remaining in the reaction product can be further reduced. From the viewpoint of obtaining this effect more reliably, the amount of polymerization initiator in the polymerization process is preferably 0.4 parts by mass or more per 100 parts by mass of monomer, and more preferably 0.9 parts by mass or more.
[0061] Furthermore, by setting the amount of polymerization initiator in the polymerization process to 5.0 parts by mass or less per 100 parts by mass of monomer, the amount of polymerization initiator decomposition products contained in the reaction product can be reduced. As a result, the decrease in the dispersibility of fine particles due to polymerization initiator decomposition products can be more easily avoided. From the viewpoint of more reliably obtaining this effect, the amount of polymerization initiator in the polymerization process is preferably 4.0 parts by mass or less per 100 parts by mass of monomer, and more preferably 3.5 parts by mass or less.
[0062] In determining the preferred range for the amount of polymerization initiator used in the polymerization process, the upper and lower limits for the amount of polymerization initiator described above can be arbitrarily combined. For example, the preferred range for the amount of polymerization initiator may be 0.4 parts by mass or more and 4.0 parts by mass or less, or 0.9 parts by mass or more and 3.5 parts by mass or less.
[0063] [Esterification process] In the esterification step, a solid acid catalyst having a sulfo group is brought into contact with the reaction product during polymerization or after polymerization is complete in the polymerization solvent. When the reaction product is brought into contact with the solid acid catalyst in this way, a portion of the repeating unit (a) in the reaction product reacts with the alcohol in the polymerization solvent and is esterified by the catalytic action of the solid acid catalyst. As a result, the repeating unit (b) can be formed in the reaction product.
[0064] The timing of the esterification step is not particularly limited, as long as it is performed after the polymerization of the monomer has started in the polymerization step. That is, for example, the polymerization step and the esterification step may be performed in parallel by starting the polymerization of the monomer while the polymerization solvent and the solid acid catalyst are in contact. Alternatively, for example, the esterification step may be performed by bringing the reaction product into contact with the solid acid catalyst during the polymerization step. In these cases, the polymerization reaction of the monomer and the esterification reaction of the reaction product produced by polymerization proceed simultaneously.
[0065] Alternatively, for example, the reaction product after the polymerization step may be contacted with a solid acid catalyst to carry out an esterification step. In this case, a portion of the repeating units (a) contained in the reaction product after polymerization is esterified.
[0066] From the viewpoint of more easily obtaining an aqueous solution with excellent storage stability, it is preferable to carry out the polymerization step and the esterification step in parallel in the above manufacturing method.
[0067] The solid acid catalyst used in the esterification process is insoluble in the polymerization solvent and has sulfo groups on its surface. The solid acid catalyst is preferably composed of one or more compounds selected from the group consisting of polymers containing repeating units derived from styrene and modified with sulfo groups, and inorganic oxides having sulfo groups on their surface, and more preferably composed of polymers containing repeating units derived from styrene and modified with sulfo groups.
[0068] As a polymer containing repeating units derived from styrene and modified with sulfo groups, for example, a strongly acidic cation exchange resin can be used.
[0069] The shape of the solid acid catalyst is not particularly limited, but from the viewpoint of increasing the contact area with the polymerization solvent and reaction product and carrying out the esterification reaction more efficiently, it is preferable that the solid acid catalyst has a particulate shape. That is, it is preferable to bring the particles of the solid acid catalyst into contact with the reaction product in the esterification step.
[0070] Furthermore, the average particle size of the solid acid catalyst particles is preferably 0.1 mm or more and 3.0 mm or less. By setting the average particle size of the solid acid catalyst particles to preferably 0.1 mm or more, and more preferably 0.2 mm or more, the solid acid catalyst can be easily separated and removed from the aqueous solution after the esterification step is completed. On the other hand, by setting the average particle size of the solid acid catalyst particles to preferably 3.0 mm or less, and more preferably 2.0 mm or less, the contact area with the polymerization solvent and monomer can be increased, thereby further improving the efficiency of the esterification reaction.
[0071] The average particle size of the solid acid catalyst particles mentioned above is the median diameter calculated based on the volume-based particle size distribution. The volume-based particle size distribution of the solid acid catalyst can be obtained, for example, by a laser diffraction / scattering particle size distribution analyzer or by image analysis of an optical microscope.
[0072] In the esterification process, various methods can be used to bring the reaction product into contact with the solid acid catalyst. For example, when using solid acid catalyst particles in the esterification process, a method can be employed in which the solid acid catalyst particles are placed in the polymerization solvent in the reaction vessel, and the reaction product and solid acid catalyst are brought into contact within the reaction vessel. Alternatively, for example, a method can be employed in which the reaction vessel and a strainer filled with solid acid catalyst particles are connected by piping, and the polymerization solvent is circulated through a path including the reaction vessel, strainer, and piping, thereby bringing the reaction product and solid acid catalyst into contact within the strainer.
[0073] From the viewpoint of further improving the reaction efficiency in the esterification process, it is preferable to place solid acid catalyst particles in the polymerization solvent in the reaction vessel and bring the reaction product into contact with the solid acid catalyst within the reaction vessel.
[0074] [Solvent replacement process] The above-mentioned manufacturing method may further include a solvent replacement step of replacing the organic solvent contained in the polymerization solvent after the esterification step is completed with water. In the above-mentioned manufacturing method, by performing the solvent replacement step after the esterification step is completed, the content of organic solvents in the aqueous solution can be reduced.
[0075] In the solvent replacement step, more specifically, the organic solvent is replaced with water by adding water to the polymerization solvent and removing the organic solvent. As a method for removing the organic solvent from the polymerization solvent, known methods such as atmospheric distillation or reduced-pressure distillation can be employed. The organic solvent separated from the polymerization solvent in the solvent replacement step includes, for example, alcohol in the polymerization solvent and organic solvents other than alcohol that are added as needed.
[0076] The addition of water to the polymerization solvent may be performed before the removal of the organic solvent begins, or during the removal of the organic solvent. Alternatively, water can be continuously supplied to the polymerization solvent while the organic solvent is being removed.
[0077] In the solvent replacement step, the organic solvent in the polymerization solvent may be completely replaced with water, or only a portion of the organic solvent may be replaced with water. From the viewpoint of suppressing hydrolysis of the polymer in the aqueous solution, it is preferable in the solvent replacement step to replace the organic solvent with water such that the content of alcohols having 1 to 4 carbon atoms in the aqueous solution is 0.1% by mass or more and 3.0% by mass or less. Furthermore, in the solvent replacement step, it is preferable to completely replace organic solvents other than alcohols having 1 to 4 carbon atoms in the polymerization solvent with water.
[0078] The timing of the solvent replacement step is not particularly limited as long as it is performed after the esterification step is completed. For example, if the manufacturing method includes a solid acid catalyst separation step described later, the solvent replacement step may be performed before the solid acid catalyst separation step or after the solid acid catalyst separation step.
[0079] [Solid acid catalyst separation process] The above-mentioned manufacturing method may further include a solid acid catalyst separation step, in which the solid acid catalyst contained in the polymerization solvent is separated from the polymerization solvent after the esterification step is completed. The timing of the solid acid catalyst separation step is not particularly limited as long as it is performed after the esterification step is completed. For example, if the manufacturing method includes a solvent replacement step, which will be described later, the solid acid catalyst separation step may be performed before the solvent replacement step or after the solvent replacement step. From the viewpoint of performing the solvent replacement step following the polymerization step, it is preferable that the solid acid catalyst separation step be performed after the solvent replacement step. Furthermore, known methods such as filtration can be used as the method for separating the solid acid catalyst from the polymerization solvent. [Examples]
[0080] Examples of the aqueous solution of the acrylic acid polymer and its manufacturing method are described below. The acrylic acid polymer in this example includes an acrylic acid polymer consisting of repeating units (a) derived from acrylic acid and repeating units (b) derived from an acrylic acid ester. The weight-average molecular weight of the acrylic acid polymer is 1,500 to 10,000. The acrylic acid ester is an ester of acrylic acid and an alcohol having 1 to 4 carbon atoms. The pH of the aqueous solution of the acrylic acid polymer is 2.5 or less. The more detailed composition and manufacturing method of the aqueous solution of the acrylic acid polymer in this example are as follows.
[0081] (Example 1) The aqueous solution of the acrylic acid polymer in Example 1 contains an acrylic acid polymer composed of repeating units (a) derived from acrylic acid and repeating units (b) derived from isopropyl acrylate. The pH of the aqueous solution, the concentration of the polymer, and the weight-average molecular weight of the polymer in this example are shown in Table 1. The method for producing the aqueous solution of the acrylic acid polymer in Example 1 is as follows.
[0082] First, 700 g of isopropyl alcohol and 100 g of solid acid catalyst were placed in a reaction vessel equipped with a stirrer and a condenser, and the contents of the reaction vessel were heated until the temperature reached 80°C. The solid acid catalyst used in this example was a bead-shaped strong acid cation exchange resin ("Amberlist® 15dry" manufactured by Organo Corporation, with an average particle size of 0.6-1 mm).
[0083] Next, a polymerization initiator solution was prepared by dissolving 10 g of 75% by mass benzoyl peroxide in 100 g of methyl ethyl ketone, and a monomer solution was prepared by mixing acrylic acid and isopropyl alcohol in a mass ratio of acrylic acid:isopropyl alcohol = 1:1. After adding the polymerization initiator solution to the reaction vessel, 1000 g of the monomer solution was supplied to the reaction vessel over 5 hours while stirring the contents of the reaction vessel. This allowed for the parallel carrying out of the polymerization step, in which acrylic acid was polymerized, and the esterification step, in which the reaction product produced by polymerization was reacted with isopropyl alcohol. The masses of acrylic acid and isopropyl alcohol supplied to the reaction vessel are shown in Table 1. In Table 1, acrylic acid is abbreviated as "AA", isopropyl alcohol as "IPA", benzoyl peroxide as "BPO", and methyl ethyl ketone as "MEK".
[0084] After the supply of the reaction solution was complete, the reaction vessel was stirred for 1 hour while maintaining the temperature at 80°C. Subsequently, isopropyl alcohol and methyl ethyl ketone were removed from the reaction vessel by vacuum distillation while supplying deionized water to the reaction vessel. In this way, the organic solvent in the reaction vessel was replaced with deionized water, and an aqueous solution of the polymer was obtained. After the aqueous solution thus obtained was cooled to room temperature, the aqueous solution was filtered using a 100-mesh polyethylene mesh filter to separate the solid acid catalyst from the aqueous solution.
[0085] Subsequently, the aqueous solution was brought into contact with an adsorbent to adsorb the benzoic acid produced by the decomposition of benzoyl peroxide onto the adsorbent and remove it from the aqueous solution. More specifically, the aqueous solution was supplied to a 3M ZetaPlus adsorption depth filter "B90-50S" manufactured by 3M, which was attached to a filter holder (3M "INLINE 90-TE-T"), using a diaphragm pump (Takumina "Q-100-TT-PS" manufactured by Takumina Co., Ltd.), and the aqueous solution after passing through the filter was collected. The supply rate of the polymer aqueous solution to the filter was 15 mL / min. The aqueous solution of Example 1 was obtained by the above procedure.
[0086] (Example 2) The aqueous solution of Example 2 has a composition that is generally similar to that of the aqueous solution of Example 1. The method for producing the aqueous solution of Example 2 is the same as the method for producing the aqueous solution of Example 1, except that a silica gel modified with sulfo groups (Teika Cure-6, bead-shaped, average particle size 0.2 mm, manufactured by Teika Co., Ltd.) was used as the solid acid catalyst.
[0087] (Comparative Example 1) The aqueous solution of Comparative Example 1 is composed of polyacrylic acid and water. The method for producing the aqueous solution of Comparative Example 1 is the same as the method for producing the aqueous solution of Example 1, except that a solid acid catalyst was not added to the reaction vessel.
[0088] (Comparative Example 2) The aqueous solution of Comparative Example 2 is composed of polyacrylic acid and water. The weight-average molecular weight of the polyacrylic acid is 30,000. The method for producing the aqueous solution of Comparative Example 2 is the same as the method for producing the aqueous solution of Example 1, except that the solvent initially added to the reaction vessel is changed to a mixed solvent of 350 g of isopropyl alcohol and 350 g of water, the amount of polymerization initiator solution added is changed to 55 g, and the composition of the monomer solution is changed to acrylic acid:isopropyl alcohol:water = 2:1:1 in mass ratio. The masses of acrylic acid, isopropyl alcohol, and water supplied to the reaction vessel are shown in Table 1.
[0089] Table 1 shows the content of repeating units (b) in the acrylic acid polymer and polyacrylic acid (hereinafter collectively referred to as "polymers") obtained above, the molecular weight of the polymer, storage stability, and washability. The evaluation methods for these are as follows.
[0090] (Content of repeating unit (b)) The aqueous solutions of the examples and comparative examples were diluted 2-fold by adding heavy water. DSS-d6 was added as a standard substance to this diluted solution to prepare a sample solution. Then, using a nuclear magnetic resonance spectrometer (Bruker "AVANCE III"), the sample solution was subjected to... 1 The 1H-NMR spectrum was measured. The temperature of the sample solution was set to 25°C. 1 In the 1H-NMR spectrum, the signal originating from repeating unit (b) has a chemical shift of 1.0 ppm, while the signal originating from the main chain has a chemical shift of 1.2–2.9 ppm. Therefore, the content of repeating unit (b) can be calculated based on the intensity ratio of these signals.
[0091] (Molecular weight of polymer) The weight-average molecular weight of the polymer, in terms of sodium polyacrylate, was measured using a gel permeation chromatograph (model "HLC-8020," manufactured by Tosoh Corporation) under the following conditions.
[0092] [Measurement conditions] Column: A column consisting of one G4000PW, one G3000PW, and one G2500PW connected in series (all manufactured by Tosoh Corporation). Detection device: RI Eluent: pH 7 phosphate buffer containing 0.1 mol / L NaCl. Standard substance: Sodium polyacrylate (manufactured by Sowa Kagaku Co., Ltd.)
[0093] (pH of aqueous solution) The pH of the aqueous solution was measured using a pH meter (HORIBA Corporation's "D-51").
[0094] (Storage stability) Storage stability was evaluated based on the transparency of the aqueous solution immediately after preparation and after long-term storage. The measurement methods are as follows.
[0095] [Initial transparency] The aqueous solution prepared using the method described above was collected in a 10 mm long glass cell. The glass cell was then attached to a spectrophotometer, and the transmittance of light at a wavelength of 610 nm was measured. The transmittance obtained in this way was defined as the initial transparency of the aqueous solution. The "Initial Transparency" column in Table 1 shows the initial transparency of each aqueous solution.
[0096] [Transparency after long-term storage] The aqueous solutions prepared using the method described above were placed in a sealed container and left to stand for one month at a temperature of 15°C. Afterward, the aqueous solutions in the sealed container were collected into a 10 mm long glass cell. The glass cell was then attached to a spectrophotometer, and the transmittance of light at a wavelength of 610 nm was measured. The light transmittance obtained in this way was defined as the transparency of the aqueous solution after long-term storage. The "Transparency after Long-Term Storage" column in Table 1 shows the transparency of each aqueous solution after long-term storage.
[0097] If the polymer aggregates during storage of the aqueous solution, the clarity of the solution decreases. Therefore, a larger difference between the initial clarity and the clarity after long-term storage indicates lower storage stability of the aqueous solution.
[0098] (cleanability) First, the objects to be cleaned and the cleaning solution to be used for evaluating the cleaning performance were prepared as follows.
[0099] To prepare the test specimens for cleaning, first, a silicon wafer with a 1000 nm thick SiO2 film was cut to create a 30 mm square test piece. Separately, a colloidal silica aqueous dispersion (PL-7, manufactured by Fuso Chemical Industries, Ltd., particle concentration 23 wt%, average particle diameter 80 nm) was diluted with deionized water to a particle concentration of 10%, and then the pH was adjusted to 11 using potassium hydroxide to prepare the wafer contamination solution. 50 mL of the wafer contamination solution was poured into a 100 mL plastic cup, and the test piece was immersed in this wafer contamination solution for 5 minutes before being removed from the cup. The test specimens for cleaning were thus prepared.
[0100] Furthermore, washing solutions were prepared by diluting any aqueous solution from Examples 1-2 or Comparative Examples 1-2 in ion-exchanged water to a polymer concentration of 0.10% by mass.
[0101] The cleaning performance was evaluated using the objects to be cleaned and the cleaning solution obtained as described above. First, 100 mL of cleaning solution was poured into a 1 L plastic cup, and a stirring bar was placed inside. Next, the objects to be cleaned were immersed in the cleaning solution in the cup, and the cleaning solution was stirred by rotating the stirring bar at a rotation speed of 600 rpm to clean the objects. Five minutes after the start of cleaning, the objects to be cleaned were removed from the cup, and nitrogen gas was blown onto them to dry them. An optical microscope (Nikon Corporation's "ECLIPSE® LV100ND") was used to observe the outer edges and the center of the surface of the dried objects at 50x magnification, and the number of particle residues and organic residues present on the objects were evaluated, respectively. In the "Cleaning Performance" column of Table 1, the symbol "A" was used if no residue was observed in the field of view, the symbol "B" was used if a small amount of residue was observed, and the symbol "C" was used if a large amount of residue was observed.
[0102] [Table 1]
[0103] As shown in Table 1, the aqueous solutions of Example 1 and Example 2 contain polymers comprising the repeating units (a) and (b). Furthermore, the weight-average molecular weight of the polymer and the pH of the aqueous solution are within the specified ranges. Therefore, the aqueous solutions of these examples have excellent storage stability. In addition, because the aqueous solutions of these examples have excellent dispersibility of fine particles, foreign matter such as fine particles adhering to the object to be cleaned can be easily removed by using the aqueous solution as a cleaning agent.
[0104] In contrast, the polymer contained in the aqueous solution of Comparative Example 1 is polyacrylic acid and does not have repeating units (b). Therefore, the aqueous solution of Comparative Example 1 had poor storage stability.
[0105] The weight-average molecular weight of the polymer contained in the aqueous solution of Comparative Example 2 is greater than the specified range mentioned above. Therefore, the aqueous solution of Comparative Example 2 has poor dispersibility of fine particles, and when used as a cleaning agent, fine particles tend to remain on the surface of the object being cleaned.
[0106] Although the embodiments of the acrylic acid polymer aqueous solution, its manufacturing method, and cleaning agent have been described above based on the examples, the specific embodiments of the acrylic acid polymer aqueous solution, its manufacturing method, and cleaning agent according to the present invention are not limited to those of the examples, and the configuration can be appropriately modified without impairing the spirit of the present invention.
Claims
1. An aqueous solution of an acrylic acid polymer comprising an acrylic acid polymer consisting of repeating units (a) derived from acrylic acid and repeating units (b) derived from an acrylic acid ester, The weight-average molecular weight of the acrylic acid polymer is 1,500 or more and 10,000 or less. The acrylic acid ester is an ester of acrylic acid and an alcohol having 1 to 4 carbon atoms. An aqueous solution of an acrylic acid polymer, wherein the pH of the aqueous solution of the acrylic acid polymer is 2.5 or less.
2. The aqueous solution of the acrylic acid polymer according to claim 1, wherein the content of the repeating unit (b) in the acrylic acid polymer is 1.5% by mass or more and 5.0% by mass or less with respect to all repeating units contained in the acrylic acid polymer.
3. The aqueous solution of the acrylic acid polymer according to claim 1, wherein the concentration of the acrylic acid polymer is 30% by mass or more and 50% by mass or less.
4. A cleaning agent comprising an aqueous solution of an acrylic acid polymer according to any one of claims 1 to 3, A detergent wherein the concentration of the acrylic acid polymer is 100 ppm by mass or more and 10,000 ppm by mass or less.
5. A method for producing an aqueous solution of an acrylic acid polymer according to any one of claims 1 to 3, A polymerization step in which a monomer containing acrylic acid is polymerized in a polymerization solvent containing the aforementioned alcohol, A method for producing an aqueous solution of an acrylic acid polymer, comprising: an esterification step of contacting a solid acid catalyst having a sulfo group with the reaction product obtained by polymerization in the polymerization solvent, thereby reacting the alcohol with a portion of the repeating unit (a) in the reaction product to form the repeating unit (b).
6. A method for producing an aqueous solution of an acrylic acid polymer according to claim 5, wherein the polymerization step and the esterification step are carried out in parallel.
7. A method for producing an aqueous solution of an acrylic acid polymer according to claim 5, wherein the content of the acrylic acid in the monomer is 95 parts by mass or more per 100 parts by mass of the monomer.
8. The method for producing an aqueous solution of an acrylic acid polymer according to claim 5, wherein the polymerization solvent contains one or more alcohols selected from the group consisting of primary alcohols and secondary alcohols.
9. The method for producing an aqueous solution of an acrylic acid polymer according to claim 5, wherein the solid acid catalyst is composed of one or more compounds selected from the group consisting of polymers containing repeating units derived from styrene and modified with sulfo groups, and inorganic oxides having sulfo groups on their surface.
10. A method for producing an aqueous solution of an acrylic acid polymer according to claim 6, wherein in the esterification step, particles of the solid acid catalyst are brought into contact with the reaction product.