JP2000273110A - Photoinitiator for water-soluble polymer preparation, process for preparation of water-soluble polymer, and polymer flocculant prepared by this process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain such a photoinitiator for water-soluble polymer preparation as having the ability to give a polymer having a high molecular weight as well as good solubility in water; a preparing process for a water-soluble polymer using this photoinitiator; and a polymer flocculant prepared by this process. SOLUTION: The photoinitiator has a cycloalkanol structure in the molecule. A particularly preferable example is 1-benzoyl-1-hydroxycyclohexane. The preparing process comprises photoirradiation to an aqueous solution containing the photoinitiator and a vinyl monomer. A vinyl monomer preferable is an acrylamide or a monomer mixture of both an acrylamide and a tertiary and/or quaternary salt of a dialkylaminoalkyl (meth)acrylates. A water-soluble polymer prepared by this process has a high molecular weight and little insoluble matters, consequently it is suitable as a polymer flucculant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a photoinitiator for producing a water-soluble polymer, a method for producing a water-soluble polymer using the photoinitiator, and a water-soluble polymer produced by the method. According to the photoinitiator of the present invention, a water-soluble polymer having a high molecular weight and good solubility, particularly suitable for use as a polymer flocculant can be obtained.

[0002]

2. Description of the Related Art A polymer flocculant is used for the purpose of flocculating and suspending suspended substances in a liquid such as waste water, etc. In addition to inorganic flocculants, nonionic and cationic flocculants are used. And anionic organic polymer flocculant (hereinafter simply referred to as “polymer flocculant”) and the like. The method for producing this polymer flocculant is based on an aqueous solution polymerization method using a redox initiator or a photoinitiator due to the difference in polymerization method,
Heterogeneous polymerization methods such as reversed-phase suspension polymerization and reversed-phase emulsion polymerization. Of these, the fact that no organic solvent is used and the polymerization operation is simple,
Is generally used. The polymer coagulant has a high molecular weight and a good solubility in water (less insoluble matter) because of its excellent coagulation performance and less burden on piping and pumps during processing. Coalescence is desired. Further, such a polymer having good water solubility and a high molecular weight is very useful in fields such as papermaking chemicals and thickeners in addition to the use of a flocculant.

In order to reduce the insoluble content of the polymer,
It is preferable to suppress the crosslinking reaction during the polymerization. As the method, for example, Japanese Patent Publication No. Hei 4-10881 and
No. 882 discloses a method for producing a water-soluble polymer, which comprises coating the surface of a polymerization system with a paraffin, an alkylene oxide compound or the like after the polymerization system has stopped flowing freely, and then continuing the polymerization. It has been disclosed. JP-A-6-322010 discloses that an aqueous solution of a monomer is prepared under specific conditions to improve the stability of the aqueous monomer solution, thereby obtaining a water-soluble polymer having good water solubility. A method for producing a hydrophilic polymer compound is disclosed. However, these methods have a problem that the production process of the water-soluble polymer becomes complicated.

[0004] Japanese Patent Publication No. 55-11684 discloses a method for producing a cationic polymer, which comprises adding hypophosphite in the UV-initiated polymerization of a water-soluble polymer. . Further, Japanese Patent Application Laid-Open
JP-A-231308 discloses a method for producing a water-soluble polymer, which comprises using a specific photoinitiator. However, even with these methods, it is difficult to sufficiently achieve both high molecular weight and low insoluble content.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoinitiator which gives a water-soluble polymer having a high molecular weight and good solubility in water, and a process for producing a water-soluble polymer using the photoinitiator. And a polymer flocculant produced by this method.

[0006]

Means for Solving the Problems The present inventors have found that by using a photoinitiator having a specific structure in the molecule, the crosslinking reaction during the photoradical polymerization is suppressed, and a high molecular weight but insoluble It has been found that a water-soluble polymer which is particularly suitable for use as a polymer flocculant can be obtained.

That is, the photoinitiator for producing a water-soluble polymer according to the first aspect of the present invention is a photoinitiator for producing a water-soluble polymer by photoradical polymerization of a vinyl monomer. It is characterized by comprising a compound having a cycloalkanol structure in the molecule.

The photoinitiator is preferably a compound represented by the following structural formula (1) as in the second invention.

[0009]

Embedded image

[In the above formula (1), X is A
r—C (＝ O) — or Cy—N ＝ N— and Ar
Is a phenyl group or -Cl, -Br, -OH, -Alk
Or -OAlk (where Alk has 1 to 1 carbon atoms)
6 represents an alkyl group), Cy is a group represented by a structural formula represented by the following formula (2), and Y and Z are -OH, -N (A
lk) ₂ , -OAlk, -O-Si (Alk) ₃ or-
CN, R ¹ and R ³ are —H, —OH, or an alkyl group having 1 to 6 carbon atoms, and R ² and R ⁴ are —H
Or an alkyl group having 1 to 6 carbon atoms, wherein Y is -O
When H, a is an integer of 0 to 11, b is an integer of 1 to 11, and when Y is not -OH, a and b are 1 to 1.
Is an integer of 1, and a + b is an integer of 2 to 11, and when Z is -OH, c is an integer of 0 to 11, d is an integer of 1 to 11, and Z is not -OH. And c and d are integers of 1 to 11, and c + d is 2 to 11
Is an integer.

[0011]

Embedded image ]

A particularly preferred compound as the photoinitiator is a compound represented by the structural formula (1), wherein X is Ar—C (（O), Y is —OH, a
Is 0, b is 4 or 5, and R ¹ and R ² are —H.

In the method for producing a water-soluble polymer according to a fourth aspect of the present invention, the aqueous solution containing the photoinitiator according to the first, second or third aspect and a vinyl monomer is irradiated with light. It is characterized by the following.

[0014] The manufacturing method of the present invention comprises the following steps:
When the vinyl monomer is made of acrylamide,
Alternatively, as in the sixth invention, the vinyl monomer is
It is particularly useful when it is a monomer mixture comprising tertiary and / or quaternary salts of acrylamide and dialkylaminoalkyl (meth) acrylate.

Further, the water-soluble polymer of the present invention comprises
It is manufactured by the method of the fifth or sixth invention. This water-soluble polymer is particularly suitable as a polymer flocculant. In this specification, acrylamide or methacrylamide is represented as (meth) acrylamide,
Acrylic acid or methacrylic acid is represented as (meth) acrylic acid, and acrylate or methacrylate is represented as (meth) acrylate.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. (1) Photoinitiator The photoinitiator for producing a water-soluble polymer of the present invention is characterized by having a cycloalkanol structure in the molecule. At least one of the carbon atoms constituting the ring of the cycloalkanol structure is bonded to a hydroxyl group and a hydrogen atom, or is bonded to a hydroxyl group and a group that is radically cleaved with the carbon atom by light irradiation. Is preferred. The structure of the other portion is not limited as long as it is a compound having this structure and functioning as a photoinitiator, but is preferably a compound represented by the above structural formula (1).

X in the above formula (1) is Ar—C (=
O)-or Cy-N = N-, and Ar-C (=
O)-. This Ar is a phenyl group or -Cl, -Br, -OH, -Alk or -O
Alk [where Alk represents an alkyl group having 1 to 6 (more preferably 1 to 4) carbon atoms] is a phenyl group substituted with one or two or more kinds, and the number of the substituents is 1 To 3 are preferred. Desirable Ar is a phenyl group or a phenyl group substituted with 1 or 2 or more of -Alk or -OAlk. Y is -OH, -N (Alk) ₂ , -OAlk, -O
-Si (Alk) ₃ or -CN, most preferably -OH.

R ¹ is -H, -OH, or 1 carbon atom.
To 6 (more preferably 1 to 4) alkyl groups;
² is -H or 1 to 6 carbon atoms (more preferably 1 to 6
And 4) an alkyl group. A + b is an integer of 2 to 11 (more preferably an integer of 4 to 6, particularly preferably 5).
It is. When Y is -OH, a is an integer of 0 to 11 (more preferably an integer of 0 to 2, particularly preferably 0), b is an integer of 1 to 11, and a preferred value of b is 4
And an integer of from 6 to 6, particularly preferably 5. On the other hand, if Y is-
When it is not OH, a is an integer of 1 to 11 (more preferably an integer of 1 to 3, particularly preferably 1), and b is 1 to 11
It is an integer of 11, and a preferable value of b is an integer of 3 to 5 (particularly preferably 4). Note that R ¹ and R ² may be the same or different groups. When b is 2 or more, a plurality of R ¹ contained in one molecule may be all the same or different from each other, and the same applies to R ² .

In the description of the above formula (1),
Examples of the alkyl group 6 include a methyl group, an ethyl group,
n- and i-propyl groups, n-, i- or tert
-Butyl group. Cy in X is a group represented by the structural formula shown in the above formula (2). In this formula, Z, R ³ , R ⁴ , c and d are each Y in formula (1). , R ¹ , R ² , a and b have the same meanings.

In the compound of the formula (1), X is Ar-C
(= O), a compound in which Y is —OH, a is 0, b is 4 or 5, and R ¹ and R ² are —H, that is, a 1-arylcarbonyl-1-hydroxycycloalkane is preferable. Specific examples of the compound include 1-benzoyl-1-hydroxycyclohexane, 1-benzoyl-1-hydroxycyclopentane, 1- (4-methylbenzoyl) -1-hydroxycyclohexane, 1- (3,4-dimethylbenzoyl) ) -1-Hydroxycyclohexane, 1- (2,
4-dimethylbenzoyl) -1-hydroxycyclohexane, 1- (2,5-dimethylbenzoyl) -1-hydroxycyclohexane, 1- (4-ethylbenzoyl)
-1-hydroxycyclohexane, 1- (4-isopropylbenzoyl) -1-hydroxycyclohexane, 1
-(4-isobutylbenzoyl) -1-hydroxycyclohexane and 1- (4-methoxybenzoyl) -1
-Hydroxycyclohexane and the like, and among these, 1-benzoyl-1-hydroxycyclohexane is preferable.

(2) Type and composition ratio of vinyl monomer The vinyl monomer used in the present invention (hereinafter simply referred to as "monomer")
Sometimes. ) Are preferably water-soluble monomers, for example, (meth) acrylamide; (meth) acrylic acid and alkali metal salts or ammonium salts such as sodium salt of these acids, and acrylamide-2-methylpropanesulfonic acid and the like. Acrylamidoalkanesulfonic acid and its alkali metal or ammonium salts;
Dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate; tertiary or quaternary salts such as hydrochlorides and sulfates thereof; N, N'-
Tertiary or quaternary salts such as dialkylaminoalkyl (meth) acrylamide and their hydrochlorides and sulfates; and dialkyldiallylammonium salts such as dimethyldiallylammonium chloride. In addition, a water-insoluble monomer such as acrylonitrile, an N-substituted derivative of acrylamide, or styrene may be used in combination with the water-soluble monomer as long as the water solubility of the obtained polymer is not impaired. These monomers may be used alone or in a combination of two or more.

In the present invention, the monomer may be as defined in claim 5
As described in the above, it is preferable that it is composed of acrylamide. In this case, it is composed of only acrylamide, or 10 mol% or more of acrylamide (more preferably 15 mol% or more).
Mol%) and a mixture comprising another vinyl monomer copolymerizable therewith. In this case, other vinyl monomers include dialkylaminoalkyl (meth)
Tertiary and / or quaternary salts of acrylates are preferred. Further, a cationic monomer containing one or more (preferably 5 mol% or more, more preferably 10 mol% or more) selected from tertiary salts and / or quaternary salts of dialkylaminoalkyl (meth) acrylates The monomer mixture is also a preferred vinyl monomer for the present invention.

(3) Method for Producing a Water-Soluble Polymer By irradiating these monomers and an aqueous solution containing one or more of the photoinitiators of the present invention by light irradiation and polymerizing them,
It is possible to obtain a water-soluble polymer having a high molecular weight and a very small amount of insoluble components. In this aqueous solution polymerization, the monomer concentration in the monomer aqueous solution is usually preferably in the range of 20 to 90% by weight, more preferably in the range of 25 to 80% by weight. If the monomer concentration exceeds 90% by weight, it is difficult to remove the heat of polymerization, and it becomes difficult to control the polymerization reaction. On the other hand, when the monomer concentration is less than 20% by weight, the productivity and the drying efficiency in the case of forming a powdery product are low. The reaction can be carried out batchwise or continuously.

The concentration of the photoinitiator is determined in consideration of the molecular weight and composition of the water-soluble polymer to be obtained.
pm (more preferably 2 to 500 ppm, further preferably 3 to 200 ppm). The intensity of light irradiation is determined in consideration of the initiator concentration, the molecular weight of the water-soluble polymer to be obtained, the polymerization time, and the like, and is usually in the range of 0.5 to 1,000 W / m ² , 5-400
It is preferably in the range of W / m ² . This irradiation intensity may be constant during the polymerization or may be changed during the polymerization. As a light source, a fluorescent chemical lamp, a fluorescent blue lamp, a metal halide lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, or the like can be used, and ultraviolet light and visible light obtained from these light sources may be used. When the reaction is performed in a batch system, the light irradiation time (polymerization time) is usually 0.5 to 360 minutes, preferably 3 to 300 minutes, and more preferably 5 to 240 minutes. When the reaction is carried out continuously, the residence time is usually 0.5 to 360.
Minutes, preferably 3 to 300 minutes, more preferably 5 to 2 minutes.
40 minutes.

The preferred temperature of the reaction system at the start of the polymerization is 40 ° C. or lower, preferably 25 ° C. or lower, more preferably 10 ° C. or lower. When the polymerization initiation temperature is higher than 40 ° C., the frequency of the branching reaction may increase to increase the amount of insolubles or the average molecular weight may decrease. The lower limit of the polymerization initiation temperature is not particularly limited, but is -10 from the viewpoint of operability and energy efficiency.
It is preferable that the temperature is not lower than ° C. Further, the maximum temperature reached in the system during the polymerization is preferably less than 100 ° C, more preferably less than 95 ° C. Processes such as drying and pulverization of the obtained polymer may be performed according to a conventional method.

The water-soluble polymer obtained by using the photoinitiator of the present invention has a molecular weight of 0.5% by weight in a 4% by weight aqueous sodium chloride solution at 25 ° C. (measured by a B-type viscometer). Hereinafter, also referred to as “0.5% salt viscosity”) is preferably 10 mPa · S or more, and more preferably 30 mPa · S. When such a high-molecular weight water-soluble polymer is used as a polymer flocculant, excellent coagulation performance can be exhibited by adding a small amount to muddy water. The upper limit of the 0.5% salt viscosity is not particularly limited, but is usually 200 mPa · s or less. The water-soluble polymer obtained using the photoinitiator of the present invention was prepared by dissolving a polymer sample in ion-exchanged water to prepare 400 ml of a 0.1% by weight polymer solution. When filtered through a mesh sieve, the volume of the insoluble matter remaining on the sieve is preferably 5% by volume or less, more preferably 1% by volume or less, based on the total amount of the solution. Most preferably no. According to the present invention, even in the case of the high molecular weight as described above, almost no insoluble matter is generated, it is economical with no loss of monomer, and the insoluble matter is clogged in a pipe or the like. Therefore, stable operation can be achieved during polymerization.

In the production method of the present invention, the photoinitiator of the present invention is combined with a usual initiator having no cycloalkanol structure, for example, benzophenone, benzoin, benzoin alkyl ether, acetophenone type, acylphosphine oxide type and the like. Photoinitiators, amine-based photosensitizers such as triethanolamine and methyldiethanolamine, thermal polymerization initiators such as azo compounds, persulfates and peroxides, or redox-based initiators may be used in combination. . In this case, the proportion of the photoinitiator of the present invention in the entire initiator is preferably at least 10% by weight (more preferably at least 30% by weight).

The water-soluble polymer obtained by the present invention can be used for various uses, and specifically, a polymer flocculant,
Examples thereof include a papermaking agent and a thickener, and in particular, can be suitably used as a polymer flocculant.

(4) Function The reason why a water-soluble polymer having a high molecular weight and containing no insoluble components can be obtained by using the photoinitiator of the present invention is not necessarily clear, but is presumed as follows. You. That is, the cycloalkanol radical generated by photocleavage reacts with the monomer to initiate polymerization, but partially,
It is thought that the hydroxyl group in this cycloalkanol radical is ketonized to generate a hydrogen radical, and the hydrogen radical suppresses the α-position hydrogen abstraction reaction of the produced polymer, thereby preventing the crosslinking reaction from occurring. .

[0030]

EXAMPLES The present invention will be described more specifically with reference to the following examples. (Example 1) A monomer mixture of 70 mol% of acrylamide and 30 mol% of a quaternized salt of dimethylaminoethyl acrylate with methyl chloride (hereinafter referred to as "DAC") was mixed with a total weight of 500 g and a monomer concentration of 35. Distilled water was added to give a weight percent. This was charged into a cylindrical glass container (reactor) having an inner diameter of 146 mm, and after adjusting the pH to 4.0, nitrogen bubbling was performed for 30 minutes while maintaining the temperature of the aqueous solution at 15 ° C. to obtain an aqueous monomer solution. At this time, the liquid depth is 3
It was 0 mm. Next, 1-benzoyl-1-hydroxycyclohexane (initiator A) as a photoinitiator was added to the monomer aqueous solution in an amount of 4% by weight based on the monomer pure content.
0 ppm (2.11 mmol%) was added, and nitrogen bubbling was further performed for 2 minutes. Then, from above the reactor, 10
0W Black Light (Toshiba Corporation, product name "H10
OBL ”), irradiation was performed at an irradiation intensity of 1.7 mW / cm ² for 20 minutes, followed by irradiation at an irradiation intensity of 5.0 mW / cm ² for 10 minutes to obtain a hydrogel polymer. This hydrogel was cut into pieces each having a size of about 3 mm, dried at 80 ° C. for 5 hours with a hot air drier, and then pulverized with a pulverizer to obtain a powdery polymer. When the obtained polymer was applied to sewage sludge, a good floc was formed, and the sludge after the floc formation was excellent in filterability, and a cake obtained by dewatering the filtrate after filtration had a water content of It was low.

(Examples 2 and 3) The addition amounts of 1-benzoyl-1-hydroxycyclohexane as a photoinitiator were 50 ppm (2.64 mmol) and 60 pp, respectively.
A powdery polymer was obtained in the same manner as in Example 1 except that m (3.17 mmol) was used. When the obtained polymer was applied to sewage sludge, a good floc was formed, and the sludge after the floc formation was excellent in filterability, and a cake obtained by dewatering the filtrate after filtration had a water content of It was low.

(Comparative Examples 1 to 5) As a photoinitiator, each compound shown in Table 1 was used in place of 1-benzoyl-1-hydroxycyclohexane. The amount of the photoinitiator used was 2.64 mmol% with respect to the pure monomer content. In other respects, a powdery polymer was obtained in the same manner as in Example 1.

(Comparative Examples 6 to 10) As photoinitiators, 1-
Each compound shown in Table 1 was used in place of benzoyl-1-hydroxycyclohexane. Table 1 shows the amount of photoinitiator used.
The values shown in the table were used. In other respects, a powdery polymer was obtained in the same manner as in Example 1.

[0034]

[Table 1]

The photoinitiators A to E in Table 1 are the following compounds, respectively.

Initiator A: 1-benzoyl-1-hydroxycyclohexane

Embedded image

Initiator B: 2-hydroxy-2-methyl-
1-phenylpropan-1-one

Embedded image

Initiator C: 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1
-Propan-1-one

Embedded image

Initiator D: 2,2-dimethoxy-1,2-
Diphenylethan-1-one

Embedded image

Initiator E: benzoin ethyl ether

Embedded image

Initiator F: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide

Embedded image

The following physical properties of the polymers obtained in Examples 1 to 3 and Comparative Examples 1 to 10 were measured. The results are shown in Table 1. [0.5% Salt Viscosity] Each polymer was dissolved in a 4% by weight aqueous sodium chloride solution to prepare a 0.5% by weight polymer solution, and the solution was prepared using a B-type viscometer at 25 ° C. and 60 rpm. The viscosity after one minute was measured. [Insoluble content] Each polymer was dissolved in ion-exchanged water to obtain 0.1%.
A 400% by weight polymer solution was prepared, and the whole amount of the solution was filtered through a 20-cm diameter, 83-mesh sieve.
The insoluble material remaining on the sieve was collected and its volume was measured.

As can be seen from the results in Table 1, the polymers of Examples 1 to 3 using the initiator A corresponding to the photoinitiator of the present invention all have a 0.5% salt viscosity of 80 mPa · S or more. And a water-soluble polymer having a high molecular weight and containing no insoluble components. On the other hand, in Comparative Examples 1 and 2 using initiators B and C in which the cyclohexanol structure part of the initiator A was replaced with a linear (non-cyclic) secondary alcohol, the amount of the initiator used was changed in Example 2. When the same amount was used (based on the number of moles), the insoluble content contained in the polymer was remarkably large at 200 ml or more, and the 0.5% salt viscosity was clearly lower than those in Examples 1 to 3. And also in Comparative Examples 6 and 7 in which the added amount was increased in order to reduce the insoluble content,
As in Examples 1 to 3, insoluble components could not be eliminated at all.

The polymers obtained in Comparative Examples 3, 4, 8, and 9 using initiators D and E, which are conventional general photoinitiators, also have a 0.5% salt viscosity and an insoluble content. Was inferior to Examples 1 to 3, and even when the amount of the initiator used was increased or decreased, these performances could not be compatible. In Comparative Example 5 using the same amount (in terms of moles) of the initiator F, which is a kind of acylphosphine oxide compound, described in JP-A-10-231308 as in Example 2, although there was no insoluble matter, The 0.5% salt viscosity was significantly lower. As in Comparative Example 10, the amount of initiator used was reduced (4
(0 ppm), the 0.5% salt viscosity increased slightly, but was clearly lower than in Examples 1 to 3, and insoluble components were generated. When the amount of the initiator was less than 40 ppm, the polymerization did not proceed under the above polymerization conditions.

It should be noted that the present invention is not limited to the specific embodiments described above, but can be variously modified within the scope of the present invention according to the purpose and application.

[0046]

The photoinitiator for producing a water-soluble polymer of the present invention has an effect of suppressing a crosslinking reaction during photoradical polymerization. Therefore, according to the production method of the present invention using this photoinitiator, it is possible to obtain a water-soluble polymer having a high molecular weight and a small amount of insoluble matter, and particularly suitable for use as a polymer flocculant. The polymer coagulant using the water-soluble polymer produced by the method of the present invention has excellent coagulation performance because of its high molecular weight and small amount of insoluble components.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kunihiko Mizutani 1-1-1, Funami-cho, Minato-ku, Nagoya-shi, Aichi F-term in the Nagoya Research Institute, Toagosei Co., Ltd. 4H050 AA03 AB81 4J011 QA01 QA03 QA06 SA02 SA16 SA36 SA38 UA01 WA10

Claims (7)

[Claims] 1. A photo-initiator for producing a water-soluble polymer by photo-radical polymerization of a vinyl monomer, comprising a compound having a cycloalkanol structure in the molecule. Photoinitiator for polymer production. 2. The photoinitiator for producing a water-soluble polymer according to claim 1, wherein the compound having a cycloalkanol structure in the molecule is a compound represented by the following structural formula (1). Embedded image [However, in the above formula (1), X is Ar—C (＝ O) — or Cy—N ＝ N—, and Ar is a phenyl group or —Cl, —Br, —OH,
-Alk or -OAlk (here, Alk represents an alkyl group having 1 to 6 carbon atoms) is a phenyl group substituted with one or two or more kinds, and Cy is a structural formula represented by the following formula (2). Y and Z are -OH, -N (Alk) ₂ , -OAlk,
—O—Si (Alk) ₃ or —CN, wherein R ¹ and R ³ are —H, —OH, or 1 to 6 carbon atoms.
R ² and R ⁴ are —H or an alkyl group having 1 to 6 carbon atoms. When Y is —OH, a is an integer of 0 to 11, and b is 1 to
An integer of 11 and a and b when Y is not -OH
Is an integer of 1 to 11, and a + b is an integer of 2 to 11. When Z is -OH, c is an integer of 0 to 11, d is an integer of 1 to 11, and Z is- When not OH, c and d are integers of 1 to 11, and c + d is an integer of 2 to 11. Embedded image ] 3. A compound represented by the above structural formula (1), wherein X is Ar—C (= O), Y is —OH, a is 0, b
Is a compound in which R is 4 or 5, and R ¹ and R ² are —H. The photoinitiator for producing a water-soluble polymer according to claim 2. 4. A method for producing a water-soluble polymer, comprising irradiating an aqueous solution containing the photoinitiator according to claim 1, 2 or 3 with a vinyl monomer. 5. The method for producing a water-soluble polymer according to claim 4, wherein the vinyl monomer comprises acrylamide. 6. The method according to claim 1, wherein the vinyl monomer is an acrylamide and a dialkylaminoalkyl (meth) acrylate.
The method for producing a water-soluble polymer according to claim 5, which is a monomer mixture comprising a quaternary salt and / or a quaternary salt. 7. A polymer flocculant comprising a water-soluble polymer produced by the method according to claim 4, 5 or 6.