JP4475907B2 - Polymer and production method thereof - Google Patents

Description

The present invention relates to a polymer and a method for producing the same. More specifically, the present invention relates to a polymer having properties such as solubility in an alkaline aqueous solution and suitably used for applications such as a photosensitive resin and a method for producing the same.

A polymer having a functional group such as a carboxyl group has various properties due to the characteristics exhibited by the functional group and is industrially useful. For example, since it has basic performance such as dissolution in an alkaline aqueous solution, it can be used for binders in photosensitive resin compositions and other various applications. In such a polymer, for the purpose of adjusting various properties, it is usually constituted by other monomer units together with monomer units having a functional group such as a carboxyl group. These are produced by copolymerizing monomer components containing several kinds of monomers, and the composition of each monomer unit in the polymer is distributed.

For such a polymer, a photosensitive resin composition containing a carboxyl group-containing binder polymer containing styrene or a styrene derivative as a copolymerization component, a photopolymerization initiator, and a photopolymerizable compound is disclosed (for example, patents). Reference 1). As a carboxyl group-containing binder polymer, it is described that methacrylic acid, styrene and (meth) acrylic acid ester can be obtained as a copolymer component, but the composition of the binder polymer obtained by polymerizing the copolymer component is studied. It has not been. In such a binder polymer, there was room for improvement to improve the basic performance of the photosensitive resin composition.

By the way, regarding the method for producing a random styrene-butadiene copolymer having a high styrene content, the remaining butadiene is continuously or intermittently supplied to the polymerization system so that the styrene monomer content in the polymerization monomer falls within a specific concentration range. And acrylonitrile-styrene copolymer resin having a narrow copolymer composition distribution is disclosed (for example, Patent Document 2). 3).
However, these prior arts do not describe a polymer constituted by other monomer units together with monomer units having a functional group such as a carboxyl group.
Therefore, it is suitable in the field of photosensitive resin compositions and the like, and there is room for improvement in order to improve basic performance in various applications.
JP 2000-214583 A (1-2, 10-12 pages) JP-A-60-212413 (pages 1, 4) Japanese Patent No. 3125892 (page 1-2)

The present invention has been made in view of the above situation, and is a polymer essentially comprising a monomer unit of styrene and / or a styrene derivative and a monomer unit of an unsaturated organic acid, An object of the present invention is to provide a polymer having improved basic performance and capable of being suitably used in various applications and a method for producing the same.

As a result of various studies on polymers (polymers) having a functional group such as a carboxyl group, the present inventors have found that basic performance such as dissolution of a polymer in which an styrene-based unit and an unsaturated organic acid unit are essential in an alkaline aqueous solution. Since it has, it paid attention to that it can be used for various uses. And if the composition distribution of such a polymer is narrowed and set within a specific range, the properties will be homogeneous compared to ordinary polymers, and it will be suitable for various applications taking advantage of its characteristics, especially It has been found that it can be suitably used for a photosensitive resin, and it has been conceived that the above problems can be solved brilliantly.
Moreover, in the production of the polymer, the above-mentioned effects are exhibited by keeping the fluctuation of the monomer composition ratio in the polymerization system within ± 3% of the monomer composition ratio at the start of the polymerization from the start to the end of the polymerization. As a result, the present invention has been achieved.
Usually, when copolymerizing a styrenic monomer and an unsaturated organic acid monomer as essential, a polymer having a narrow composition distribution cannot be obtained even if the monomer is charged in the same ratio as the composition of the desired polymer. Moreover, in the polymer formed by copolymerizing such a monomer system, conventionally, the examination of narrowing the composition distribution has not been made. Furthermore, in the prior art, the copolymer composition distribution has been studied. However, since the polymer system is different from that of the present invention, the intended polymer cannot be obtained simply by changing the composition. . In the present invention, for example, (1) in the initial stage, the styrene monomer is charged in a larger ratio than the target composition, and the unsaturated organic acid monomer is charged in a smaller ratio. (3) In the aging stage in the latter half of the polymerization, the monomer ratio in the polymerization system is always set at the start of the polymerization by adding only the unsaturated organic acid monomer consumed earlier. By keeping it within ± 3% of the ratio, a polymer having a narrow composition distribution can be obtained.

That is, the present invention is a polymer essentially comprising a monomer unit of styrene and / or a styrene derivative and a monomer unit of an unsaturated organic acid, and from an average value of the composition ratio of the polymer from 3% The content ratio of the polymer having a deviated composition ratio is a polymer that is 20% by mass or less.
The present invention is described in detail below.

The content of the polymer having a composition ratio deviating from 3% from the average value of the composition ratio of the polymer in the present invention is 20% by mass or less when the mass of the whole polymer is 100% by mass. By setting it as such a range, the basic performance which a polymer exhibits can be fully improved. As said content, 15% or less is preferable. More preferably, it is 10% or less.
The polymer of the present invention essentially comprises a monomer unit of styrene and / or a styrene derivative and a monomer unit of an unsaturated organic acid, and other monomers other than these monomers. The average value of the composition ratio of the polymer of the present invention is (1) monomer units of styrene and styrene derivatives in the polymer, and (2) It means the average mass ratio between the monomer unit of unsaturated organic acid and the monomer unit of (3) other monomer.
As the average value of the composition ratio of the polymer, ¹ H-NMR (nuclear magnetic resonance) of the whole polymer of the present invention is measured, and the average composition ratio is calculated from the ratio of specific ¹ H signal intensity obtained. Can be obtained. When the polymer of the present invention is in the form of a solution, the solution is added to a large amount of methanol / water mixed precipitant to form a precipitate, and the precipitate is determined by measuring ¹ H-NMR. Can do.

The composition ratio deviating from the above 3% means that the average value of the composition ratio in the polymer is [(1) monomer unit of styrene and styrene derivative] / [(2) monomer unit of unsaturated organic acid] / [(3) Monomer unit of other monomer] = a / b / c (provided that a + b + c = 100 mass%), the monomer unit of (1) and / or the monomer of (2) Composition ratio when the body unit deviates from 3 mass%, that is, (a-3) less than mass% or (a + 3) mass% and / or (b-3) less than mass% or (b + 3) mass% It is a composition ratio in the super.

With regard to the composition ratio deviating from the above 3%, for example, when (I) a / b = 80/20, (1) is less than 77 mass% or more than 83 mass%, and / or (2) is 17 The composition ratio is less than mass% or more than 23 mass%. In addition, when (II) a / b / c = 70/20/10, (1) is less than 67% by mass or more than 73% by mass, and / or (2) is less than 17% by mass or 23% by mass. It is a composition ratio in excess of%. Furthermore, in the case of (III) a / b / c = 20/40/40, (1) is less than 17% by mass or more than 23% by mass, and / or (2) is less than 37% by mass or 43% by mass. It is a composition ratio in excess of%.
In summary, in the case of the composition ratio deviating from the above 3%, those that do not fall within the range shown in Table 1, for example, in the case of (III), 17 to 23% by mass of the monomer unit of (1) And what does not enter the range of 37-43 mass% of monomer units of (2) becomes a composition ratio deviating from 3% in the present invention.

As the content of the polymer having a composition ratio deviating from 3% from the average value of the composition ratio of the polymer, for example, ¹ H-NMR is measured for each fraction (precipitate) obtained by fractional precipitation, It can measure by calculating the average composition ratio (mass ratio) in each fraction from the ratio of the specific ¹ H signal intensity obtained. The fractional precipitation can be performed by the following method.

<Separate precipitation>
The polymer is concentrated, 8 parts of solid content is dissolved in 12 parts of ethyl acetate, 60 parts of acetone is added to the resulting polymer solution, and when the polymer is precipitated, it is filtered (precipitate 1). 5 parts of hexane is added to the filtrate, and the precipitated polymer is filtered off (precipitate 2). The operation of adding 5 parts of hexane and filtering the precipitated polymer is repeated until the solids recovery is 90% by mass or more (precipitate 3 to precipitate n-1). The filtrate is concentrated, and the concentrated filtrate is added to 50 times amount of the mixed precipitant of methanol / water to precipitate all remaining dissolved polymer, which is filtered off (precipitate n).
In the present invention, each of the precipitates ^{1 to} n thus obtained is measured by ¹ H-NMR to contain a polymer having a composition ratio deviating from 3% from the average composition ratio of the polymers. The amount can be determined.

In the average composition of the polymer, when the total monomer unit amount is 100% by mass, the monomer unit amount of (1) is preferably 35 to 95% by mass. More preferably, it is 40-90 mass%, More preferably, it is 45-85 mass%. Moreover, it is preferable that the monomer unit amount of (2) is 35-5 mass%. More preferably, it is 30-10 mass%, More preferably, it is 25-15 mass%.

As described above, the polymer of the present invention essentially comprises a monomer unit of styrene and / or a styrene derivative and a monomer unit of an unsaturated organic acid, and a monomer unit of an unsaturated organic acid. By having a property such as solubility in an alkaline aqueous solution, it can be suitably used for applications such as a photosensitive resin, and by having a monomer unit of styrene and / or a styrene derivative, The basic performance exhibited by such a polymer can be sufficiently improved. Moreover, you may have the monomer unit of other monomers other than these monomers.
Examples of the styrene derivative include α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, o-methoxystyrene, m- Methoxystyrene, p-methoxystyrene, o-ethoxystyrene, m-ethoxystyrene, p-ethoxystyrene, o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, o-chlorostyrene, m-chlorostyrene, p- Chlorostyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-acetoxystyrene, m-acetoxystyrene, p-acetoxystyrene, ot-butoxystyrene, mt-butoxystyrene, pt -Butoxystyrene and the like are preferred. These can use 1 type (s) or 2 or more types. Among these, styrene is preferable. In styrene and / or styrene derivatives, the benzene ring has a functional group such as an alkyl group such as a methyl group or a tert-butyl group, a nitro group, a nitrile group, an alkoxyl group, an acyl group, a sulfone group, a hydroxyl group, or a halogen atom. May be substituted.

Examples of the unsaturated organic acid include (meth) acrylic acid, α-bromo (meth) acrylic acid, α-chloro (meth) acrylic acid, β-furyl (meth) acrylic acid, β-styryl (meth) acrylic. Acid; maleic acid monoester such as maleic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, monoisopropyl maleate; fumaric acid monoester such as fumaric acid, monomethyl fumarate, monoethyl fumarate, monoisopropyl fumarate Itaconic acid, itaconic anhydride, itaconic acid monomethyl, itaconic acid monoethyl, itaconic acid monoisopropyl etc. itaconic acid monoesters; citraconic acid, citraconic acid anhydride, citraconic acid monomethyl, citraconic acid monoethyl, citraconic acid monoisopropyl, etc. Citraconic acid Monoester; cinnamic acid, alpha-cyanocinnamic acid, crotonic acid, propiolic acid are preferred. These can use 1 type (s) or 2 or more types. Among these, (meth) acrylic acid is preferable.

Examples of the other monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, and (meth) acrylic. Hexyl acid, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, (meth) (Meth) acrylic acid esters such as dodecyl acrylate; acrylamides such as 2,2,3,3-tetrafluoropropyl acrylate acrylamide, 2,2,3,3-tetrafluoropropyl methacrylate acrylamide, diacetone acrylamide; (Meth) acrylonitrile; vinyl ethyl ether, vinyl Vinyl alcohol esters such as -n- butyl ether, vinyl acetate, vinyl propionate, vinyl esters such as vinyl butanoate, etc. and the like. These can use 1 type (s) or 2 or more types.

The polymer of the present invention preferably has an acid value of 50 to 200. Even if the acid value is less than 50 or more than 200, the basic performance exhibited by the polymer may not be sufficiently improved. As a lower limit, More preferably, it is 60, More preferably, it is 70. As an upper limit, More preferably, it is 180, More preferably, it is 160. A more preferable range is 60 to 180, and a further preferable range is 70 to 160.
The acid value can be measured by titration using an automatic titration apparatus (for example, COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.) and using a KOH aqueous solution as a titrant.

The polymer of the present invention preferably has a weight average molecular weight of 3000 to 50000. Even if the weight average molecular weight is less than 3000 or exceeds 50000, the basic performance exhibited by the polymer may not be sufficiently improved. As a lower limit, More preferably, it is 4000, More preferably, it is 5000. As an upper limit, More preferably, it is 35000, More preferably, it is 20000. Moreover, as a more preferable range, it is 4000-35000, and as a more preferable range, it is 5000-20000.
The said weight average molecular weight can be measured by the gel permeation chromatography (GPC; elution solvent tetrahydrofuran) by polystyrene conversion.

The polymer of the present invention is preferably produced by polymerizing a monomer component containing the aforementioned styrene and / or styrene derivative monomer and an unsaturated organic acid monomer. In such a production method, the amount of the monomer used may be appropriately set so that the polymer has the composition ratio as described above, and the monomer component enters the polymerization system. As a method for charging, all of the monomers may be charged all at once before polymerization is started, or all or part of the monomers may be charged continuously or dividedly.
A preferable form in the production of the polymer is a form in which the polymerization is performed so that the fluctuation of the monomer composition ratio in the polymerization system is within ± 3% from the start to the end of the polymerization. When the reactivity ratio of styrene and / or styrene derivative and unsaturated organic acid is compared, highly reactive monomers are easily used for polymerization and consumed earlier, so the consumed monomers are compensated. Thus, by adding a monomer in a polymerization system, it can manufacture so that the basic performance which a polymer exhibits may fully be improved. A method for producing the polymer of the present invention from a polymerization system containing a monomer of styrene and / or a styrene derivative and a monomer of an unsaturated organic acid, the monomer in the polymerization system A method for producing a polymer in which the polymerization is performed so that the fluctuation of the composition ratio is within ± 3% from the start to the end of the polymerization is also one aspect of the present invention.

The monomer composition ratio in the polymerization system is a mass ratio of styrene and / or a styrene derivative and an unsaturated organic acid that have not yet been polymerized in the polymerization system. When the body is contained, the mass ratio of styrene and / or a styrene derivative, an unsaturated organic acid, and another monomer.
Within ± 3%, the monomer composition ratio at the start of polymerization is [(1) styrene and styrene derivatives] / [(2) unsaturated organic acid] / [(3) other monomers] = d / E / f (where d + e + f = 100 mass%), each of (1) and (2) within the polymerization system is within 3 mass% of the monomer composition ratio at the start of polymerization. . In addition, the form in which the polymerization is performed within ± 3% is always the fluctuation of the monomer composition ratio in the polymerization system of styrene and / or a styrene derivative and an unsaturated organic acid from the start to the end of the polymerization. For example, when the composition ratio at the start of polymerization is d / e = 89/11, from the start to the end of the polymerization. The monomer composition ratio in the polymerization system is within the range of (1) 86 to 92% by mass and (2) 8 to 14% by mass. Moreover, in the case of d / e / f = 70/20/10, it is set within the range of (1) 67 to 73% by mass and (2) 17 to 23% by mass, and d / e / In the case of f = 20/40/40, it is set to (1) 17-23 mass% and (2) 37-43 mass%. The monomer composition ratio at the start of polymerization is the mass ratio of the respective monomers in the polymerization system immediately before the start of polymerization.

The monomer composition ratio at the start of polymerization in the polymerization system may be appropriately set depending on the reactivity ratio of the monomers so that the polymer has the desired composition, but the ratio of styrene and styrene derivative It is preferable to make the ratio higher than the target composition and the ratio of the unsaturated organic acid to be smaller.
In the above monomer component, styrene and styrene derivatives, and monomers other than unsaturated organic acids may be contained, and the content of styrene, styrene derivatives and unsaturated organic acids may be all monomers. When the component is 100% by mass, it is preferably 60% by mass or more. More preferably, it is 70 mass% or more, More preferably, it is 75 mass% or more.

In the production method of the present invention, it is more preferable that the unsaturated organic acid is added after the polymerization in the polymerization system has proceeded 65% or more. Further, it is more preferable that only the unsaturated organic acid is added. The unsaturated organic acid may be added continuously, discontinuously, or a combination thereof. For example, the unsaturated organic acid may be added dropwise into the polymerization system. Moreover, you may throw in collectively, and when throwing discontinuously, you may throw in regularly and it may not be so. The time when the unsaturated organic acid is added may be any time after the polymerization in the polymerization system has progressed 65% or more, and more preferably after 70% or more has progressed. More preferably, it is 75% or more.
The unsaturated organic acid is more easily consumed by the polymerization reaction than styrene and styrene derivatives. Therefore, by introducing the unsaturated organic acid after the polymerization has proceeded 65% or more, it has a target composition and has basic performance. A sufficiently improved polymer can be prepared.
After the polymerization in the polymerization system proceeds 65% or more, when the total charge of the monomer components is 100% by weight, 65% by weight of the total charge of the monomer components is used for the polymerization. And after the polymerization is complete.

As a particularly preferable form in which the monomer component in the polymerization reaction is added, for example, styrene and methacrylic acid are copolymerized at a monomer composition ratio (styrene / methacrylic acid) at the start of polymerization = 89/11. In addition, when adding a monomer component in the polymerization system after the start of polymerization, the styrene is less than the monomer composition ratio at the start of the polymerization, the amount of methacrylic acid is increased, for example, the composition of styrene / methacrylic acid = 74/26 In this mode, the methacrylic acid is added to the polymerization system after the polymerization has proceeded by 65% or more.

In the above polymerization reaction, emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization and the like are suitable, and these may be combined for polymerization. Among these, bulk polymerization, solution polymerization and the like are preferable. Further, a polymerization initiator may be used. For example, it is preferable that a radical is generated by heat. Examples of such a polymerization initiator include azo compounds such as azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2′-azobisisobutyrate, Organic peroxides such as benzoyl peroxide, toluoyl peroxide, and di-t-butyl peroxide are preferred.
In the polymerization reaction, a reaction solvent may be used, and as such a reaction solvent, any solvent that can dissolve monomer components and the like can be used. For example, alcohols such as isopropyl alcohol and butyl alcohol can be used. Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate, butyl acetate, isobutyl acetate, methyl lactate, ethyl lactate, butyl lactate, isobutyl lactate, propylene glycol monomethyl ether acetate and 3-methoxybutyl acetate Cellosolves such as ethyl cellosolve and butyl cellosolve; ethers such as 1,4-dioxane, tetrahydrofuran, and propylene glycol monomethyl ether; aromatics such as toluene, ethylbenzene, o, m, p-xylene, and the like are preferable. These may be used alone or in combination. Among these, ethyl acetate, toluene, and 1,4-dioxane are preferable.
About the reaction conditions in the said superposition | polymerization, as reaction temperature, 40 to 120 degreeC is preferable. More preferably, they are 50 degreeC or more and 100 degrees C or less, More preferably, they are 60 degreeC or more and 90 degrees C or less. The reaction time is preferably 60 minutes or more and 720 minutes or less. More preferably, it is 120 minutes or more and 660 minutes or less, More preferably, it is 240 minutes or more and 600 minutes or less.

The polymer of the present invention and the method for producing the same have the above-described configuration, and the basic performance exhibited by the polymer is improved. Therefore, the polymer and the method for producing the polymer can be suitably used in various applications. It is suitable for use.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

Example 1
<Polymerization>
400 parts of ethyl acetate, 403 parts of styrene (St) and 49 parts of methacrylic acid (MAA) were heated to 70 ° C. in a reaction kettle, and V65 (manufactured by Wako Pure Chemical Industries, Ltd .; azo-based initiator, 2,2′- The reaction was started by adding 12 parts of azobis (2,4-dimethylvaleronitrile) and 40 parts of ethyl acetate. Over 230 minutes after 10 minutes, 253 parts of St, 89 parts of MAA, 47 parts of V65, and 219 parts of ethyl acetate were added dropwise. Over 180 minutes after 240 minutes from the start of the reaction, 18 parts of V65 and 61 parts of ethyl acetate were added dropwise. After 360 minutes from the start of the reaction, 10 parts of MAA were added all at once, and the reaction was completed after 480 minutes from the start of the reaction.

<Separate precipitation>
After completion of the polymerization, 8 parts of the solid content obtained by concentrating and drying the obtained polymer solution was dissolved in 12 parts of ethyl acetate. The resulting polymer solution was added to 60 parts of acetone. If the polymer precipitates, it is filtered off. Thereto was added 5 parts of hexane, and the precipitated polymer was filtered off. The operation of adding 5 parts of hexane and filtering the precipitated polymer was repeated until the solids recovery was 90% by mass or more. The remaining filtrate was concentrated, and the concentrated solution was added to 50 times amount of a mixed precipitant of methanol / water (2/1) to precipitate all remaining dissolved polymer, followed by filtration.
<Analysis>
Each fraction obtained by the fractional precipitation was analyzed by NMR. As a result, the average composition (parts) was 81/19, and 90% by mass was within ± 2%. Table 2 shows the composition distribution.

Comparative Example 1
400 parts of ethyl acetate, 362 parts of St, 90 parts of MAA (St / MAA = 80/20) were heated to 70 ° C. in a reaction kettle, and 12 parts of V65 (manufactured by Wako Pure Chemical Industries, Ltd .; azo initiator) The reaction was started by adding 40 parts of ethyl acetate. Over 230 minutes after 10 minutes, 274 parts of St, 68 parts of MAA (St / MAA = 80/20), 47 parts of V65, and 219 parts of ethyl acetate were added dropwise. Over 180 minutes after 240 minutes from the start of the reaction, 18 parts of V65 and 61 parts of ethyl acetate were added dropwise. The temperature was lowered after 480 minutes from the start of the reaction to complete the reaction.
In the same manner as in Example 1, fractional precipitation was performed for analysis. As a result, the average composition (parts) was 80/20, and the content within ± 3% was 55% by mass. Table 2 shows the composition distribution.

Claims (4)

A polymer having a monomer unit of styrene and / or a styrene derivative and a monomer unit of an unsaturated organic acid as an essential component and soluble in an alkaline aqueous solution,
The content ratio of the polymer having a composition ratio deviating from 3% from the average value of the composition ratio of the polymer is 20% by mass or less,
The average value of the composition ratio of the polymer is 45 to 90% by mass of monomer units of styrene and styrene derivatives, and the monomer unit of unsaturated organic acid, assuming that the total monomer unit amount is 100% by mass. The amount is 35-10% by weight,
The average value of the composition ratio of the polymer is determined by measuring ¹ H-NMR (nuclear magnetic resonance) of the whole polymer (however, when the polymer is in the form of a solution, the solution is added with a large amount of methanol). / Added to a mixed precipitant of water to form a precipitate, and the ¹ H-NMR (nuclear magnetic resonance) of the precipitate is measured.), And the average composition ratio is determined from the ratio of the specific ¹ H signal intensity obtained. It is a value obtained by calculating,
The weight average molecular weight of the polymer is 3000 to 50000,
The polymer is obtained using a polymerization initiator that generates radicals by heat,
The unsaturated organic acid includes (meth) acrylic acid , α-bromo (meth) acrylic acid, α-chloro (meth) acrylic acid, β-furyl (meth) acrylic acid, and β-styryl (meth) acrylic acid. A polymer comprising at least one acid selected from the group consisting of: The polymer according to claim 1, wherein the polymer has an acid value of 50 to 200. The polymer is obtained by polymerizing a monomer component essentially comprising a monomer of styrene and / or a styrene derivative and a monomer of an unsaturated organic acid,
The unsaturated organic acid includes (meth) acrylic acid , α-bromo (meth) acrylic acid, α-chloro (meth) acrylic acid, β-furyl (meth) acrylic acid, and β-styryl (meth) acrylic acid. At least one acid selected from the group consisting of
The ratio of styrene and styrene derivative monomers in the monomer component at the start of polymerization is greater than the ratio of styrene and styrene derivative monomer units in the target polymer,
The ratio of the unsaturated organic acid monomer in the monomer component at the start of polymerization is less than the ratio of the unsaturated organic acid monomer unit in the target polymer. Item 3. The polymer according to Item 1 or 2. A method for producing a polymer according to claim 1, 2 or 3, from a polymerization system comprising a monomer of styrene and / or a styrene derivative and a monomer of an unsaturated organic acid,
A method in which the polymerization is performed so that the fluctuation of the monomer composition ratio in the polymerization system is within ± 3% from the start to the end of the polymerization, and the unsaturated organic acid is added after the polymerization has proceeded 65% or more And
The polymerization is carried out so that the fluctuation of the monomer composition ratio in the polymerization system is within ± 3% from the start to the end of the polymerization. The monomer composition ratio at the start of the polymerization is [(1) styrene and Styrene derivatives] / [(2) Unsaturated organic acid] / [(3) Other monomers] = d / e / f (where d + e + f = 100% by mass) And / or polymerization so that the monomer composition ratio of the styrene derivative is within (d ± 3) mass% and the monomer composition ratio of the unsaturated organic acid is within (e ± 3) mass%. Is a form that performs
After the polymerization proceeds 65% or more, when the total charge of the monomer components is 100% by weight, 65% by weight of the total charge of the monomer components is used for the polymerization. Until the polymerization is complete,
The polymerization in the polymerization system is solution polymerization using a reaction solvent,
The unsaturated organic acid includes (meth) acrylic acid , α-bromo (meth) acrylic acid, α-chloro (meth) acrylic acid, β-furyl (meth) acrylic acid, and β-styryl (meth) acrylic acid. A method for producing a polymer, which is at least one acid selected from the group consisting of :