JPS619416A - Production of copolymer - Google Patents

Abstract

PURPOSE:To obtain a copolymer suitable as a binder for photographic toners, free of migration of a fixed image to vinyl chloride resin and excellent in offset resistance, etc., by copolymerizing a specified dihydric phenol derivative with a polymerizable monomer. CONSTITUTION:The purpose copolymer is obtained by copolymerizing 0.5-75pts. wt. compound of formula I (wherein R1 and R2 are each H or methyl, R3 and R4 are each -(CH2)n-, formula II or the like, n is 1-8, m is 1-29, R7 and R8 are each -C2H4, or the like, and R5 and R6 are each H or formula III) with 99.5-25pts.wt. polymerizable monomer. The compound of formula I can be obtained by an addition reaction between a compound of formula IV (e.g., bisphenol A/ethylene oxide adduct) and maleic anhydride. An electrophotographic toner can be obtained by adding a colorant, a magnetic powder, etc., to said copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a novel copolymer, and in particular, a method for producing a copolymer, which has no transferability of a fixed image to a plasticized vinyl chloride resin, and
The present invention relates to a method for producing a copolymer suitable as a binder for electrophotographic toners that has excellent offset resistance in heat-pressure fixing.

(Prior Art) Conventionally, styrene-acrylate copolymers (eg, styrene-acrylate copolymers) have been used as binders for electrophotographic toners.

The toner disclosed in Japanese Patent Application Laid-Open No. 50-134652) is used, but this toner is used for developing and
When the nine images obtained by fixing come into contact with plasticized vinyl chloride resin (hereinafter referred to as PVC), the fixed toner constituting one image easily migrates to the surface of 270 (hereinafter referred to as PVC).
This property is called “PVC transferability”) Image defects and PV
causing contamination of C. This mainly occurs due to plasticizers such as dioctyl phthalate and dibutyl phthalate contained in PVC. Note that PVC is often used in plastic document scissors and the like.

On the other hand, as a fixing method for electrostatic images in electrophotography,
There are heat roll fixing, pressure fixing, high frequency heat fixing, flash fixing, etc., but the heat roll fixing method is the most popular because it is superior in image quality compared to other fixing methods. The biggest drawback of the heat roll fixing method is the offset phenomenon.

Offset phenomenon occurs when the temperature of the heat roll is too high, and the melt viscosity of the thermoplastic resin, which is the binder for the toner, is too low, so toner adheres to the roll and when the roll rotates once, it does not stick to the paper. This is a phenomenon of reattachment. To prevent this phenomenon from occurring.

As in the above publication, methods of adjusting the molecular weight distribution of the binder to a specific range, methods of cross-dispersing an offset' preventive agent in the toner (for example, JP-A No. As pointed out in Japanese Patent Publication No. 55-153944, in the latter method, the anti-offset agent is insufficiently dispersed in the toner, and in order to obtain a sufficient anti-offset effect, it has recently been found that a large amount must be used. It has been pointed out.

(Problems to be Solved by the Invention) The present invention first provides a novel method for producing a copolymer.

A second object of the present invention is to provide a method for producing a copolymer which is suitable as a binder for electrophotographic toners and has excellent PVC migration resistance.

Thirdly, the present invention uses a heat-pressure fixing method (
The present invention provides a method for producing a copolymer suitable as a binder for electrophotographic toners, which has excellent offset resistance when using a discharge-roll fixing method.

The present invention is.

General formula il+ Ordinary 2 [However, in one set.

R1 and R are each hydrogen or methyl group.

R3 and R4 are each →CHx +n (here.

n is an integer from 1 to 8) or - to +0-ru → 1 (this ζ is 9m 1 to 29 regular lines, 翫 and Rs.

-〇　2H4- or -CH2CH-CH, respectively.

In R8, when m is 2 or more, -CH*- and -OH-
CH- may be repeated in any order.

Ri and mountain are hydrogen or -C-CH=CH-COOH.

A method for producing a copolymer, characterized by copolymerizing 0.5 to 75 parts by weight of a compound represented by the formula and 995 to 25 parts by weight of a polymerizable monomer. Regarding.

The compound represented by the general formula (1) is a compound represented by the general formula (Il11
F song - Seal R = 11 (However, in formula 9, & , Rtue Rs and R4 are
It can be obtained by addition reacting a compound represented by the general formula (same as in the case of 11) with malemoleic anhydride.

As the compound represented by the general formula [111, bis(
4-hydroxyphenyl)methane, 1,1-bis(4-
hydroxyphenyl)ethane 312.2-t's(4-
Hydroxyphenyl)furopane, bis(hydroxymethyl ether), bis(2-hydroxyethyl ether), bis(2-hydroxypropyl ether), bis(
2-hydroxybutyl ether), bis(2-hydroxypentyl ether), bis(2-hydroxyhexyl ether), bis(2-hydroxyoctyl ether)
.

Bis(3-hydroxypropyl ether), bis(3-
hydroxybutyl ether), bis(3-hydroxypentyl ether), bis(3-hydroxyhexyl ether), bis(3-hydroxyoctyl ether), bis(polyoxyethylene ether), bis(polyoxypropylene ether), and the like.

The above addition reaction is carried out at 50-150"C, preferably at 70-150"C.
It can be carried out at 130°C in aromatic organic solvents such as benzene, toluene, and xylene, halogen solvents such as dichloromethane, dichloroethane, chloroform, bromoform, and chlorobenzene, and ether solvents such as diethyl ether, tetrahydrofuran, and dioxane. .

In such a reaction, a compound in which R and R are both hydrogen in the general formula t1), that is, a compound represented by the general formula (Ill), may remain unreacted, but
Without separating this, the reaction product (general formula (1)
A compound represented by 1) can be used. In this case, the compound represented by the general formula The caking resistance of toner prepared using a copolymer as a binder is poor.

Among the compounds represented by general formula (11), R3 and R4
It is practically preferable that is an alkylene group having 1 to 8 carbon atoms, particularly preferably one having 2 to 4 carbon atoms.

In addition, among the compounds represented by the general formula (11) + Rs
and R6 are -C-CH=CH-COOH at the same time, it becomes a crosslinking agent that creates two 9-polymerizable double bonds,
If this amount is too large, the fixing properties of the toner prepared using the copolymer obtained by the present invention as a binder will tend to decrease. It is preferably used in an amount of 0 to 20% by weight based on the total amount.

Examples of the polymerizable monomers include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, p-
Ethylstyrene, λ4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene,
p-n-hexylstyrene, p-n octylstyrene,
p-n-nonylstyrene.

Styrene and its derivatives such as p-n-tethylstyrene, p-n-dodecylstyrene, n-methoxystyrene, p-phenylstyrene, p-chlorostyrene, &4-dichlorostyrene, ethylene such as ethylene, propylene, butylene, isobutylene, etc. Unsaturated monoolefins, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride, vinyl acetate, and vinyl propionate.

Vinyl esters such as vinyl benzoate and vinyl butyrate, methyl acrylate, and ethyl acrylate.

n-butyl acrylate, isobutyl acrylate.

Propyl acrylate, n-octyl acrylate.

Dodecyl acrylate, 2-ethylhexyl acrylate,
stearyl acrylate, 2-chloroethyl acrylate,
Acrylic acid alkyl esters such as methyl α-chloroacrylate or derivatives thereof, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-methacrylate
Butyl, isobutyl methacrylate, n-octyl methacrylate.

Dodecyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid, alkyl methacrylates such as stearyl, phenyl acrylate, etc.+J aromatic esters of methacrylate, aromatic methacrylic esters such as phenyl methacrylate, dimethylamino acrylate Ethyl, dialkylaminoalkyl acrylates such as diethylaminoethyl acrylate, and dimethylamineethyl methacrylate.

dialkylaminoalkyl esters of methacrylic acid such as dimethylaminoethyl methacrylate; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate;

Hydroxyalkyl methacrylate and glycerin having hydroxyalkyl groups similar to these.

Examples include α-methylene aliphatic monocarboxylic acid esters such as monoacrylates or monomethacrylates of polyhydric alcohols such as trimethylolpropane.

Others include acrylonitrile and methacrylate.

Derivatives of acrylic acid or methacrylic acid such as acrylamide and methacrylamide, and in some cases acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. can also be used. Also, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isophthyl ether,
Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone;
Vinylnaphthalene salts and the like can be used in L type or in combination of two or more types. Furthermore, as the other polymerizable monomers mentioned above, a compound having two or more polymerizable double bonds that serves as a crosslinking agent can also be used in part. Aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and their derivatives, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol triacrylate.

Diethylenic carboxylic acid esters such as trimethylolpropane triacrylate, all divinyl compounds such as N,N divinylaniline, divinyl ether, divinyl sulfite, and compounds having three or more vinyl groups can be used alone or as a mixture. The amount of the crosslinking agent used is preferably 0 to 20% by weight based on the total amount of the compound represented by the general formula +11 and the polymerizable monomer, including the compound represented by the general formula (11) that serves as a crosslinking agent. , particularly preferably 0 to 5% by weight.

The compound represented by the general formula (1) and the above polymerizable monomer are polymerized to form a polymer in the presence of a radical polymerization initiator. The polymerization can be carried out by any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. As a radical polymerization initiator, hendiyl peroxide, lauroyl peroxide, tertiary peroxy 2-ethylhexanoate,
These include organic peroxides such as acetyl peroxide and tert-butyl perbenzoate, and azo compounds such as azobisinbutyronitrile and azobisdimethylvaleronitrile.
Inorganic polymerization initiators such as ammonium persulfate, sodium persulfate, and potassium persulfate can be used. The amount of polymerization initiator is 0.05 to 10iit based on the total amount of one polymerizable monomer.
J is preferably used.

A chain transfer agent can be appropriately added during polymerization.

Examples of chain transfer agents include alkyl mercaptans such as t-dodecyl mercaptan, lower alkyl xanthogens such as diisopropyl xanthogen, carbon tetrachloride, carbon tetrabromide, etc. 0 to 2% by weight based on the total amount of polymerizable monomers. Preferably used.

The electrophotographic toner prepared using the copolymer obtained according to the present invention as a binder contains 9
Contains colorant or magnetic powder.

Other additives may include toner property improvers, if necessary.

Coloring agents can include pigments or dyes. For example, carbon black, nigrosine dye, oil black, azo oil black.

Lamp black (C, 1, Na77266), aniline black, black pigments such as iron black, calco oil blue (azoec Blue 3) + aniline blue (
C.I.

Na50405), ultramarine blue (C, 1, N
177103), methylene blue chloride (C,I.

52015), phthalocyanine blue (C, 1, N1
74160), blue fl+ materials such as navy blue, cobalt blue, alkali blue lake, and furnace sky blue,
rim 0-m 4-o- (C, 1, Ha 14090)
.

Quinoline Yellow (C, I. & 47005), yellow lead.

Mineral First Yellow, Hansa Yellow G.

Yellow pigments such as Benzidine Yellow G and Permanent Yellow NCG, Rose Bengal (C, 1, Na45435).

DuPont Oil Red (C, 1, N1126105)
, Orient Oil Reddna 330 (C, 1, Magic 605
05).

Permanent Red 4R, Brilliant Carmino 6B,
Red pigments such as alizarin lake, red lead, red pigment, orange pigments such as permanent orange GTR, pyrazolone orange, Halcan orange, benzidine orange G, indanthrene brilliant orange GK, molybdenum orange, red yellow lead, malachite green offsalate ( C
, 1, Na42000), green pigments such as chrome green, pigment green B, and final yellow green G, purple pigments such as manganese violet, fast violet B, and methyl violet lake, and titanium oxide.

There are white pigments such as zinc white and antimony white.

The coloring agent is used in an amount of 0.1 to 50% by weight based on the binder, and the proportion may be determined as appropriate depending on the case.

The above-mentioned carbon black may be used as grafted carbon in which the above-mentioned polymerizable monomer is graft-polymerized to carbon black.

Magnetic powder is used when manufacturing magnetic toner.

This can serve as two colorants. Preferred magnetic powders include, for example, oxides or compounds of iron such as magnetite or ferrite, or ferromagnetic elements such as nickel and ferrite. These magnetic powders are preferably powders with a particle size of 0.01 to 3 μm, and the surface of the magnetic powder is resin.

Titanium coupling agent, silane coupling agent.

It may be treated with a higher fatty acid metal salt or the like.

These magnetic materials have a weight srs of 20 to 80 weight srs relative to the toner.

Preferably, it can be contained in an amount of 35 to 70% by weight. Less than this amount may be used as one coloring agent.

An anti-offset agent is used as a toner property improver.

Examples include fluidity improvers, cleaning performance improvers, and charge control agents.

As offset inhibitors, low molecular weight polyalkylenes such as low molecular weight polyethylene and low molecular weight polypropylene (polyalkylenes disclosed in JP-A-55-153944, and low-molecular weight olefin copolymers described in %I41+850-93647) are used. natural waxes such as carnauba wax, hydrogenated castor oil, and paraffin wax.

There are higher fatty acids, higher alcohols, x-sulfurs of polyhydric alcohols, fatty rlR esters, alkylene bis fatty acid amides, etc. Specifically, JP-A-54-1628
The anti-offset agent described in Japanese Patent No. 43 can be used. Preferably, these are used in the toner in an amount of 0 to 30% by weight.

Examples of fluidity improvers include oxides of silane, titanium, aluminum, calcium, magnesium and the like.

This oxide can be made hydrophobic with a titanium coupling agent or a silane coupling agent.

Preferably, these are used in the toner in an amount of 0 to 3% by weight.

Examples of the cleaning performance improver include metal salts of higher fatty acids such as zinc stearate, lithium stearate, and magnesium laurate, and aromatic acid esters such as pentaerythritol benzoate. These are 0 in the toner.
It is preferable to add up to 3% by weight.

As a charge control agent, Subiron Black TRH is used.

Azo dyes such as Subiron Black TPH (all trade names from Hodogaya Chemical Industries), p-fluorobenzoic acid, 2.4
Examples include aromatic acid derivatives such as -di-t-butylsalicylic acid, and tin compounds such as dibutyltin oxide and dioctyltin oxide. The charge control agent is preferably added to the toner in an amount of 0 to 5% by weight.

Anti-offset agents are used as toner property improvers.

In the present invention, it is not necessarily necessary to add it to the toner, but it may be added in some cases.

The electrophotographic toner described above can be obtained by melt-kneading the above-mentioned binder 9, colorant or magnetic powder, and, if necessary, a toner property improver, followed by pulverization and, if necessary, classification.

Further, during the polymerization of the above-mentioned polymerizable monomer, a colorant or magnetic powder and, if necessary, a toner property improver were present, and after the polymerization was completed, the obtained polymer was pulverized.

If necessary, the toner of the present invention can be obtained by υ classification. In this case, when emulsion polymerization or suspension polymerization is adopted,
Toner can be obtained by simply classifying into 9 parts without going through a pulverization process.

Note that among the toner property improvers, the fluidity improver and the cleaning performance improver are preferably externally added to the product toner afterwards.

The electrophotographic toner according to the present invention has an average particle size of 9 to 15
It is preferable to use it after classifying it into micrometers.

The electrophotographic toner according to the present invention uses a cascade development method,
Magnetic brush method, powder cloud method.

It can be applied to development methods such as a touchdown development method, a jumping method, a so-called microtoning method using a magnetic toner as a carrier, and a so-called bipolar and magnetic toner method in which a toner charge is obtained by electrification of magnetic toners by volatilization.

Furthermore, as a fixing method after development, so-called oil-less and oil-coated heat roll methods, flash methods, oven methods, pressure fixing methods, etc. can be employed. Further, as a cleaning method, a so-called fur brush method, a blade method, etc. can be adopted.

(Function) Although a novel copolymer can be obtained from the present invention, an electrophotographic toner prepared using a skeleton copolymer as a binder contains a compound represented by the general formula (11) as a copolymer component. By including the toner, it is possible to obtain a toner that has excellent resistance to vinyl chloride migration of a fixed image, and at the same time, it has excellent offset resistance when fixing by a heat-press bonding method.

Therefore, the compound represented by the general formula (11) contains 0.5 to 75 parts by weight per 99.5 to 25 parts by weight of 1 polymerizable monomer, or 95 to 50 parts by weight of 9 polymerizable monomers. It is preferable that the weight is 5 to 50 parts by weight.The general formula (
If the amount of the compound represented by 11 is too small, the PVC migration resistance will be poor, and if it is too large, the balance between toner fixing properties, caking resistance, and offset resistance will be poor. Poor moisture resistance. In addition, the above blending ratio is such that the obtained copolymer has a glass transition point of 10 to 100°C, preferably 30 to 80°C.
will be considered.

(Example) Next, the present invention will be explained in detail by way of examples.

Hereinafter, "parts" indicate "parts by weight."

Example 1 Into a flask equipped with a stirrer, a thermometer, and a condenser, 50 parts of bisphenol A ethylene oxide 2 mol adduct and 15.5 parts maleic anhydride (1.0 mol per 2 mol bisphenol A ethylene oxide adduct) were added. ratio) and 30 parts of toluene.

The mixture was kept at 100° C. for 4 hours while stirring. At the end of the preparation, the acid value changed from 185 to 92. (
The intermediate (Al solid content: 68.6 cm) was then charged with 30 parts of toluene into a flask equipped with a stirrer, a thermometer, a condenser, a dropping funnel, and a gas introduction tube, heated to 80° C., and stirred. In a dropping funnel, 44 parts of intermediate (A), 50 parts of styrene, 10 parts of methyl methacrylate, and 10 parts of butyl acrylate were added.
benzoyl peroxide 2 as a radical initiator
The mixture was added dropwise over 2 hours under a stream of N2 gas. Subsequently, the temperature was raised to 100°C and kept for 4 hours to complete polymerization.

Subsequently, the 1st polymerization mixture solution was subjected to membrane solvent under reduced pressure to obtain a solid resin (glass transition point: 65° C., differential thermometry).

90 parts of the obtained solid resin, 5 parts of nigrosine dye, and 5 parts of carbon black were kneaded using a heating mixer, and then pulverized to obtain an electrophotographic toner having an average particle size of about 12 μm.

Five parts of this electrophotographic toner was mixed with 95 parts of iron powder carrier having an average particle diameter of 150 μm, and used as a developer to develop a negative electrostatic image to obtain an unfixed image on 9 sheets of paper.

As a result of repeated tests using a tester that fixes the unfixed image obtained in this way by pressure contact with a Teflon-coated heat fixing roll (170°C), it was found that no offset development occurred and a good fixed image was obtained. It was done. Moreover, the caking resistance was also good.

Further, the obtained fixed image was brought into contact with a PvC sheet (containing 3 (l) of dioctyl phthalate as a plasticizer), and
A plasticizer migration resistance test was carried out by applying a load of g O i and leaving it at 30° C. for 12 hours. As a result, no toner migration to the PVC sheet was observed, and good results were obtained.

Example 2 A solid resin (
As a result of obtaining a glass transition point BO° C. (differential thermal balance method) and evaluating the resulting toner, it was found to have good caking resistance, fixing ability, offset resistance, and vinyl chloride stain resistance.

Example 3 Intermediate (Al 15 parts (solid content 10.3 parts), styrene 5
0 parts, 20 parts of methyl methacrylate, 2 parts of butyl acrylate
A solid resin (glass transition point: 63°C, differential thermal balance method) was obtained in the same manner as in Example 1 from 0 part of benzoyl peroxide and 3 parts of benzoyl peroxide. Both offset properties and PVC stain resistance were good.

Example 4 Bisphenol A ethylene oxide 10 mole adduct (
50 parts of ethylene glycol unit average 5) and 7.4 parts of maleic anhydride (bisphenol A ethylene oxide 10
Intermediate (Bl was obtained in the same manner as in Example 1 from 1.0 molar ratio to the molar adduct) and 30 parts of toluene (solid content 65.7%, acid value 48). body (B 146 parts (solid content 30.2 parts), styrene 5
0 parts, methyl methacrylate 10 parts, butyl acrylate l
A solid resin (glass transition point: 58°C, differential thermometry) was obtained from 2 parts of 1, silver oxide in the same manner as in Example 1, made into a toner, and evaluated. As a result, caking resistance, fixing properties, Both offset resistance and PVC stain resistance were good.

Example 5 Bisphenol A ethylene oxide 2 mole adduct 50
The intermediate (
C) was obtained. (Solid content 69.6%.

Acid value 108) A solid resin (glass Transition point: 62℃, differential thermometry)
Obtain it and turn it into toner.

As a result of the evaluation, the caking resistance, fixing property, offset resistance, and vinyl chloride stain resistance were all good.

Comparative Example 1 Bisphenol A ethylene oxide 2 mole adduct 50
Intermediate (2) was obtained in the same manner as in Example 1 from 1 part, 6.2 parts of maleic anhydride (0.4 molar ratio to 2 moles of bisphenol A ethylene oxide adduct), and 30 parts of toluene. (Solid content 65.2%, acid value 41) Intermediate ■) 46 parts (solid content 30 parts), styrene 50 parts,
10 parts of methyl methacrylate, 10 parts of butyl acrylate,
A solid resin (glass transition point: 38°C, differential thermometry) was obtained from 2 parts of benzoyl peroxide in the same manner as in Example 1, and as a result of forming and evaluating a toner, the caking resistance was poor and offset occurred. .

Comparative example 2 Contains 2 moles of bisphenol A ethylene oxide.

50 parts of additive, 34.1 parts of maleic anhydride (2..
An intermediate (El) was obtained in the same manner as in Example 1 from 30 parts of toluene (solid content 73.7%, acid value 18%).
6) A solid resin (glass A transition point of 70°C (differential thermal balance method) was obtained, and as a result of making and evaluating the toner, the fixability was poor.

Comparative Example 3 A solid resin (glass transition point: 80°C.

This is the result of obtaining toner and evaluating it using differential thermal balance method.

Fixation was poor.

Comparative example 4 70 parts of Sunalene, 10 parts of methyl methacrylate.

10 parts of butyl acrylate, 2 parts of benzoyl peroxide
A solid resin (glass transition point: 60°C, differential thermogravimetry) was obtained in the same manner as in Example 1.

As a result of toner formation and evaluation, the caking resistance and fixing properties were good/difficult, but offset occurred, and the vinyl chloride stain resistance was significantly poor.

The results of each of the above Examples and Comparative Examples are shown in the table.

The evaluation criteria are as follows.

(1) Caking resistance: ○: No caking ×: Caking occurrence Test conditions: 50°C, open system for 24 hours, no load (2) Fixability: ○: No image peeling ×: Image peeling Test method: Cellotape Peeling (3) Offset resistance: ○: No offset occurred 62 Partially or slightly occurred ×: Offset occurred completely (4) PVC stain resistance: ○: Toner migration did not occur on the PVC film (dye migration did occur) ×: Toner was completely transferred to the PVC film. An electrophotographic toner prepared using the compound as a binder exhibits excellent PVC migration resistance and offset resistance.

Claims (1)

[Claims] 1. General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [However, in the formula, R_1 and R_2 are hydrogen or a methyl group, R_
3 and R_4 are respectively -(CH_2)-_n (where n is an integer of 1 to 8) or -R_7-(O-R_8)-_m, where m is 1 to 29
The integers R_7 and R_8 are respectively ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and R_8 is -CH_2- and ▲There are mathematical formulas, chemical formulas, tables, etc.▼ when m is 2 or more, repeated in any order. May be returned. R_5 and R_6 are each hydrogen or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and R_5 and R_6 are not hydrogen at the same time] 0.5 to 75 parts by weight of a compound represented by and a polymerizable monomer 9. A method for producing a copolymer, comprising copolymerizing 9.5 to 25 parts by weight.